A&A 505, 1049–1074 (2009) DOI: 10.1051/0004-6361/200912592 c ESO 2009 Astronomy & Astrophysics Parkes H I observations of galaxies behind the southern Milky Way II. The Crux and Great Attractor regions (l ≈ 289 ◦ to 338 ◦ ) , A. C. Schröder 1,2 , R. C. Kraan-Korteweg 3 , and P. A. Henning 4 1 Hartebeesthoek Radio Astronomy Observatory, PO Box 443, Krugersdorp 1740, South Africa e-mail: [email protected]2 Dept. of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK 3 Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa 4 Institute for Astrophysics, University of New Mexico, MSC07 4220, 800 Yale Blvd., NE, Albuquerque, NM, 87131, USA Received 28 May 2009 / Accepted 15 July 2009 ABSTRACT As part of our programme to map the large-scale distribution of galaxies behind the southern Milky Way, we observed 314 optically- selected, partially-obscured galaxies in the Zone of Avoidance (ZOA) in the Crux and Great Attractor (GA) regions. An additional 29 galaxies were observed in the Vela ZOA survey region (because of the small numbers they are not discussed any further). The observations were conducted with the Parkes 64 m (210 ft) radio telescope, in a single-pixel pointed mode, reaching an rms noise level of typically 2−6 mJy over the velocity search range of 400 <v< 10 500 km s −1 . A total of 162 galaxies were detected (plus 14 galaxies in the Vela region). The detection rate is slightly higher than for the Hydra/Antlia region (52% versus 45%) observed in the same way. This can be explained by the prominence of the GA overdensity in the survey regions, which leads to a relatively higher fraction of nearby galaxies. It is also evident from the quite narrow velocity distribution (largely confined to 3000−6000 km s −1 ) and deviates significantly from the expectation of a uniform galaxy distribution for the given sensitivity and velocity range. No systematic differences were found between detections and non-detections, in terms of latitude, foreground extinction, or environment, except for the very central part of the rich Norma cluster, where hardly any galaxies were detected. A detailed investigation of the H i content of the galaxies reveals strong H i deficiency at the core of the Norma cluster (within about a 0.4 Abell radius), similar to what has been found in the Coma cluster. The redshifts obtained by this observing technique result in a substantial reduction of the so-called redshift ZOA. This is obvious when analysing the large-scale structure of the new H i data in combination with data from other (optical) ZOA redshift surveys. The lower latitude detections provide further evidence of the extension of the Norma Wall, across the ZOA, in particular its bending towards the Cen-Crux clusters above the Galactic plane at slightly higher redshift, rather than a straight continuation towards the Centaurus clusters. Key words. catalogs – surveys – ISM: dust, extinction – galaxies: fundamental parameters – radio lines: galaxies – cosmology: large-scale structure of Universe 1. Introduction Revealing the three-dimensional distribution of galaxies over the entire sky including the regions behind the dust and stars of our Milky Way is important for understanding the motion of the Local Group with respect to the microwave background as well as the peculiar flow fields in the nearby Universe (e.g., re- view by Kraan-Korteweg & Lahav 2000; Kraan-Korteweg 2005; and contributions in “Mapping the Hidden Universe”, 2000, ASP CS 218, eds. Kraan-Korteweg et al. 2000; “Nearby Large-Scale Structures and the Zone of Avoidance”, 2005, ASP CS 329, eds. Fairall & Woudt 2005). Except for blind H i surveys where both the angular coordinates and redshifts of galaxies are simulta- neously detected, this is a two-step process: first the galaxies have to be identified (in the optical, near or far-infrared), then Figure 1 is only available in electronic form at http://www.aanda.org Table 1 is also available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/505/1049 redshifts have to be determined in follow-up studies. This has been done in the optical, either as single-channel or multi-fibre spectroscopy depending on surface brightness of the galaxies and the galaxy density on the sky or in the radio using the 21 cm spectral line of neutral hydrogen. The latter is most effective for the most obscured and/or low surface brightness spirals and ir- regular galaxies. Based on the deep optical galaxy catalogues in the south- ern Zone of Avoidance (ZOA; Kraan-Korteweg 2000; Woudt & Kraan-Korteweg 2001), we have obtained pointed H i ob- servations of a sample of obscured spiral galaxies with the 64 m Parkes radio telescope in Australia. Previous results of the Hydra/Antlia region (266 ◦ < ∼ < ∼ 296 ◦ ) were presented in Kraan-Korteweg et al. (2002, hereafter Paper I). The second part, presented here, covers the observations of spiral galaxies in the Crux and Great Attractor regions (hereafter GA; 289 ◦ < ∼ < ∼ 338 ◦ , −10 ◦ < ∼ b < ∼ +10 ◦ ; Woudt & Kraan-Korteweg 2001). The optical search detected galaxies above a diameter limit of D > ∼ 0. 2 on IIIaJ film copies of the ESO/SRC sky survey. For a detailed description of the optical search, see Paper I and Article published by EDP Sciences
Parkes H I observations of galaxies behind the southern Milky Way
II. The Crux and Great Attractor regions (l ≈ 289◦ to 338◦)�,��
A. C. Schröder1,2, R. C. Kraan-Korteweg3, and P. A. Henning4
1 Hartebeesthoek Radio Astronomy Observatory, PO Box 443, Krugersdorp 1740, South Africae-mail: [email protected]
2 Dept. of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK3 Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa4 Institute for Astrophysics, University of New Mexico, MSC07 4220, 800 Yale Blvd., NE, Albuquerque, NM, 87131, USA
Received 28 May 2009 / Accepted 15 July 2009
ABSTRACT
As part of our programme to map the large-scale distribution of galaxies behind the southern Milky Way, we observed 314 optically-selected, partially-obscured galaxies in the Zone of Avoidance (ZOA) in the Crux and Great Attractor (GA) regions. An additional29 galaxies were observed in the Vela ZOA survey region (because of the small numbers they are not discussed any further). Theobservations were conducted with the Parkes 64 m (210 ft) radio telescope, in a single-pixel pointed mode, reaching an rms noiselevel of typically 2−6 mJy over the velocity search range of 400 < v < 10 500 km s−1. A total of 162 galaxies were detected (plus14 galaxies in the Vela region). The detection rate is slightly higher than for the Hydra/Antlia region (52% versus 45%) observed inthe same way. This can be explained by the prominence of the GA overdensity in the survey regions, which leads to a relatively higherfraction of nearby galaxies. It is also evident from the quite narrow velocity distribution (largely confined to 3000−6000 km s−1) anddeviates significantly from the expectation of a uniform galaxy distribution for the given sensitivity and velocity range. No systematicdifferences were found between detections and non-detections, in terms of latitude, foreground extinction, or environment, except forthe very central part of the rich Norma cluster, where hardly any galaxies were detected. A detailed investigation of the H i contentof the galaxies reveals strong H i deficiency at the core of the Norma cluster (within about a 0.4 Abell radius), similar to what hasbeen found in the Coma cluster. The redshifts obtained by this observing technique result in a substantial reduction of the so-calledredshift ZOA. This is obvious when analysing the large-scale structure of the new H i data in combination with data from other(optical) ZOA redshift surveys. The lower latitude detections provide further evidence of the extension of the Norma Wall, across theZOA, in particular its bending towards the Cen-Crux clusters above the Galactic plane at slightly higher redshift, rather than a straightcontinuation towards the Centaurus clusters.
Key words. catalogs – surveys – ISM: dust, extinction – galaxies: fundamental parameters – radio lines: galaxies –cosmology: large-scale structure of Universe
1. Introduction
Revealing the three-dimensional distribution of galaxies over theentire sky including the regions behind the dust and stars ofour Milky Way is important for understanding the motion ofthe Local Group with respect to the microwave background aswell as the peculiar flow fields in the nearby Universe (e.g., re-view by Kraan-Korteweg & Lahav 2000; Kraan-Korteweg 2005;and contributions in “Mapping the Hidden Universe”, 2000, ASPCS 218, eds. Kraan-Korteweg et al. 2000; “Nearby Large-ScaleStructures and the Zone of Avoidance”, 2005, ASP CS 329, eds.Fairall & Woudt 2005). Except for blind H i surveys where boththe angular coordinates and redshifts of galaxies are simulta-neously detected, this is a two-step process: first the galaxieshave to be identified (in the optical, near or far-infrared), then
� Figure 1 is only available in electronic form athttp://www.aanda.org�� Table 1 is also available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/505/1049
redshifts have to be determined in follow-up studies. This hasbeen done in the optical, either as single-channel or multi-fibrespectroscopy depending on surface brightness of the galaxiesand the galaxy density on the sky or in the radio using the 21 cmspectral line of neutral hydrogen. The latter is most effective forthe most obscured and/or low surface brightness spirals and ir-regular galaxies.
Based on the deep optical galaxy catalogues in the south-ern Zone of Avoidance (ZOA; Kraan-Korteweg 2000; Woudt& Kraan-Korteweg 2001), we have obtained pointed H i ob-servations of a sample of obscured spiral galaxies with the64 m Parkes radio telescope in Australia. Previous results ofthe Hydra/Antlia region (266◦ <∼ � <∼ 296◦) were presentedin Kraan-Korteweg et al. (2002, hereafter Paper I). The secondpart, presented here, covers the observations of spiral galaxiesin the Crux and Great Attractor regions (hereafter GA; 289◦ <∼� <∼ 338◦, −10◦ <∼ b <∼ +10◦; Woudt & Kraan-Korteweg 2001).The optical search detected galaxies above a diameter limit ofD >∼ 0.′2 on IIIaJ film copies of the ESO/SRC sky survey. Fora detailed description of the optical search, see Paper I and
1050 A. C. Schröder et al.: Parkes H I observations of galaxies behind the southern Milky Way. II.
the optical catalogue papers (Kraan-Korteweg 2000; Woudt &Kraan-Korteweg 2001). In summary, our target list consisted ofspiral galaxies without redshift information at the time of ob-servation, which have extinction-corrected diameters larger thanD0 > 60′′ (based on the Schlegel at al. 1998 extinction maps,and the Cameron 1990 correction laws). This corresponds to thecompleteness limit of the deep optical ZOA galaxy cataloguesto foreground extinction levels of AB ≤ 3.m0 (Kraan-Korteweg2000). It will therefore complement existing optical whole-sky catalogues such as Nilson (1973) for the northern sky andLauberts (1982) for the southern sky. The ESO/SRC IIIaJ film-copies that were used for the searches have such fine-grainedemulsion and sensitivity that the spiral morphology could al-ways be discerned with our 50×magnifying viewer – though notalways the spiral sub-type. At the highest extinction levels, wealso targeted smaller galaxies since optical spectroscopy is un-likely to succeed in yielding redshifts for these heavily extinctedgalaxies. We also sampled deeper in some of the overdensitieslike, e.g., the Norma cluster.
Our sample has a sensitivity of 2−6 mJy. This study istherefore complementary to the systematic blind H i survey ofthe southern ZOA conducted with the Parkes multibeam re-ceiver (Staveley-Smith et al. 2000; for preliminary results seeKraan-Korteweg et al. 2005; Henning et al. 2005), which coversthe optically opaque part of the southern ZOA (212◦ ≤ � ≤ 36◦,|b| ≤ 5◦) for the velocity range −1200 to 12 700 km s−1, with asensitivity similar to the observations presented here. A subsam-ple of this work consists of the shallow H i ZOA survey (here-after HIZSS; Henning et al. 2000), based on 8% of the integra-tion time of the full survey with a sensitivity of 15 mJy beam−1
after Hanning smoothing). In another subsample which is basedon 16% of the integration time of the full survey, Juraszek et al.(2000, hereafter JS00) focused on the area of the GA in the ZOA(308◦ <∼ � <∼ 332◦).
In the following section, a short description of the obser-vations is given (see Paper I for further details). Section 3presents the H i data and line profiles of the detected galax-ies. In Sect. 4, the non-detected galaxies are listed with theirrespective velocity search range. An analysis of the propertiesof the detected galaxies, the velocity distribution as well as thedetection rate (Sect. 5) is followed by a detailed discussion ofH i-deficiency in the Norma cluster (Sect. 6). We then present adescription of the three-dimensional galaxy distribution in andaround the investigated area (Sect. 7). A summary is given inSect. 8. Throughout the paper we assume a Hubble constant ofH0 = 70 km s−1 Mpc−1.
In Appendix A, we discuss cross-identifications of opticalgalaxies for which the detected H i signal might not necessarilybe associated with the optical counterpart, or where more thanone galaxy was detected in one pointing. In Appendix B, wepresent detections in the Vela region (245◦ <∼ � <∼ 275◦) whichhave also been observed during the course of these observingruns.
2. Observations
The Parkes 64 m radio telescope1 was used over four observ-ing periods of about 10−14 days each (June 1993, April 1994,July 1995 and September 1996). Here, we report on theobservations that cover the Crux and GA ZOA regions.
1 The Parkes telescope is part of the Australia Telescope which isfunded by the Commonwealth of Australia for operation as a NationalFacility managed by CSIRO.
A detailed description of the observational set-up is given inPaper I. A summary of the main characteristics of the observa-tions is given below.
At 21 cm, the telescope has a half-power beam-width(HPBW) of 15′. The system temperature was typically 39 K atthe time of these observations. Typical integration times were atotal of 30 min each on the source (ON) and on a reference po-sition (OFF). Strong sources had shorter integration times (10 or20 min) while weaker possible detections were reobserved untilthe reality of the signal was clearly determined. Based on cali-brating observations the internal consistency of the flux scale isabout ±15%.
In 1993, we used the 1024-channel auto correlator witha bandwidth of 32 MHz, covering, in most cases, the radialvelocity range 300−5500 km s−1, with some additional ob-servations centred at 7500 km s−1; the channel spacing was6.6 km s−1 and the velocity resolution after Hanning smooth-ing was 13.2 km s−1. From 1994 on, we covered the range300−10 500 km s−1 with a channel spacing of 13.2 km s−1 anda velocity resolution after Hanning smoothing of 27.0 km s−1.
3. Detections
In the following, we present the parameters of the 162 de-tected galaxies, from the sample of 314 target galaxies. Thedata were reduced using the Spectral Line Analysis Program(Staveley-Smith 1985). The two orthogonal polarisations wereaveraged during reduction, and a low-order polynomial base-line subtracted from each spectrum. The reduced H i spectra areshown in Fig. 1 which is available online at A&A. The opticalproperties as well as the H i parameters are given in Table 1. Thecolumns in the table are described below. A colon after an entryindicates an uncertain value.
Column 1: identification as given in the optical Crux/GAZOA galaxy catalogue (Woudt & Kraan-Korteweg 2001). A fewgalaxies from Yamada et al. (1993), which are all IRAS-selectedgalaxies, had been added to the observing programme. Theirnames start with “Y” and have the ESO-galaxy number or theIRAS number attached to it. A question mark after the namedenotes an uncertain identification of the H i signal, and a plusindicates that more than one signal was found in the pointing orin the associated OFF-observation.
Column 2: second name as found by NED2 in the order ofNGC, IC, ESO, and other catalogue names. Most of the secondidentifications originate from the ESO/Uppsala Survey of theESO(B) Atlas (Lauberts 1982). Other names come from the fol-lowing catalogues: NGC stands for the New General Catalogue(Dreyer 1888), IC stands for the Index Catalogue (Dreyer 1908),FGCE stands for the Flat Galaxy Catalog (Karachentsev et al.1993), AM for Arp & Madore (1987), CSRG for Catalog ofSouthern Ringed Galaxies (Buta 1995), HIZSS for the H i ParkesZOA Shallow Survey (Henning et al. 2000), and HIZOA forJuraszek et al. (2000).
Column 3: identification in the infrared (IR) and near-infrared (NIR): “I” indicates an entry in the IRAS PointSource Catalog according to the precepts explained in Woudt& Kraan-Korteweg (2001); “M” or “D” indicates an entry in the2MASS Extended Objects Catalogue (2MASS, 2003) and theDENIS catalogue by Vauglin et al. (2002), respectively.
Columns 4 and 5: Right Ascension RA and DeclinationDec (J2000.0).
Columns 6 and 7: Galactic longitude and latitude � and b.
2 the NASA/IPAC Extragalactic Database.
A. C. Schröder et al.: Parkes H I observations of galaxies behind the southern Milky Way. II. 1051
Column 8: morphological type. The morphological types arecoded similarly to the precepts of the RC2 (de Vaucouleurs et al.1976) with the addition of the subtypes E, M and L, which standfor early spiral (S0/a–Sab), middle spiral (Sb–Sd) and late spi-ral or irregular (Sdm–Im), respectively. (Note that the uncer-tainty of the bar presence is indicated by “Y” as in Woudt &Kraan-Korteweg (2001), rather than the standard “X” as in theRC2. We have kept their denotation.)
Column 9: major axis diameter D and minor axis diameter din arcseconds.
Column 10: apparent magnitude BJ. These magnitudes areeye-estimates from the ESO/SERC IIIaJ film copies. They com-pare well with the Lauberts & Valentijn (1989) B25 magnitudesand have a 1σ-dispersion of less than 0.m5.
Column 11: the Galactic reddening at the position of thegalaxy, as given by the DIRBE/IRAS extinction maps (Schlegelet al. 1998). See the catalogue paper (Woudt & Kraan-Korteweg2001) for a more detailed discussion.
Column 12: heliocentric H i radial velocity in km s−1 takenat the midpoint of the H i profile at the 20% level. The veloc-ity is given in the optical convention V = c · (λ − λo)/λo. Theuncertainty on the velocities, σV , can be determined followingSchneider et al. (1986) using 1.5(ΔV20 − ΔV50)(S/N)−1, whereS/N is the ratio of the peak signal to rms noise level. The me-dian error over all detections is 3.6 km s−1.
Column 13: velocity width in km s−1 of the H i profile mea-sured at the 50% level of the peak intensity. The expected erroris 2.0σV (Schneider et al. 1986), and the median error derivedfrom the table is 7.3 km s−1.
Column 14: velocity width in km s−1 of the H i profile mea-sured at the 20% level of the peak intensity. The expected erroris 3.1σV (Schneider et al. 1986), and the median error derivedfrom the table is 11.3 km s−1.
Column 15: integrated H i flux density, in Jy km s−1, uncor-rected for finite beam size. The uncertainty on the flux densities,σI , can be determined following Schneider et al. (1990) using2(1.2ΔV20/R)0.5Rσ, where R is the velocity resolution of the data(see Sect. 2) and σ is the rms noise level. The median error overall defined flux densities is 0.65 Jy.
Column 16: rms noise level in mJy measured over the regionused to fit a baseline, typically of a width of 1600 km s−1 centredon, but not including, the detection.
Column 17: most spectra have been Hanning-smoothed, ex-cept when the line width was smaller than 100 km s−1 or for otherreasons (see footnotes to the table), which is indicated with an“n” for “no Hanning-smoothing”.
Column 18: a star indicates a footnote for this entry.Column 19: angular distance of the detected galaxy from the
centre of the beam in arcminutes. Sometimes the telescope wasnot pointed towards the galaxy listed as, e.g., in a close pair orwhen there was a second detection in the beam. As the sensitiv-ity of the beam decreases with distance to the beam centre, thefluxes will have higher uncertainties (see Col. 20).
Column 20: corrected flux densities for off-centre detections.The sensitivity decreases as a function of the distance from thebeam centre. The observed flux density of galaxies detectedaway from the central pointing will be underestimated. We haveprovided a rough correction for such galaxies by assuming thatthe beam sensitivity can be approximated by a circular Gaussian.This correction becomes uncertain for distances above the beamradius, i.e., 7.′5.
Column 21: excised RFI (radio frequency interference) on ornear the detected H i profile.
The galaxy density in the Crux and particular in the GA re-gion is quite high. In 16% of the pointings, more than one galaxywas found within the 1σ beam radius. In most cases the properidentification of the detected galaxy was straightforward (bycomparing size, morphological type, optical velocity if avail-able, and distance from the beam centre). In questionable caseswe have made use of the HIPASS public data release3 (as a blindsurvey it is independent of our pointed observations) to spec-ify the origin of a signal. In a few cases the identification ofthe detection remains ambiguous or the counterpart could not befound at all. Due to the high extinction in these regions, low sur-face brightness (late-type) spiral galaxies are often too obscuredto be visible. In other cases the detection is a combination of thesignals from two or even more galaxies and the individual H i pa-rameters are uncertain or could not be derived. The problematiccases are discussed in more detail in Appendix A.
We have compared our detected velocities with indepen-dent velocity determinations in the literature. Table 2 gives thegalaxy IDs for which we have found velocity determinations,their observed velocity (from Col. 12 in Table 1), the velocityfrom the literature and its error, the origin of the measurement(optical or H i), and the reference (as explained in Table 3).
Since we did not repeat observations at Parkes for galaxieswith already existing H i data, most of the given independent ve-locities originate from optical spectroscopy. A number of strongH i sources were subsequently detected with HIZSS, JS00 and/orwith HIPASS.
The H i velocities measured by HIPASS with the Multibeam(MB) receiver compared to our single beam observations arein very good agreement. The 1σ-dispersion of 31 galaxies incommon is 11 km s−1 (including only velocities with HIPASSerror measurements <10 km s−1). A comparison with HIZSSgives a dispersion of 6.5 km s−1 for 7 galaxies. The agreementwith optical velocities is also satisfactory, giving a dispersionof 100 km s−1 for 50 measurements with errors <100 km s−1
(excluding one wrong measurement for WKK 5416).The line width measurements also agree well with HIPASS
albeit with a larger scatter of 28 km s−1 for both 50% and 20%line widths (using 29 measurements, excluding all uncertainmeasurements).
While the shallower HIPASS survey detected all galaxieswith peak flux density >120 mJy, the majority of our detec-tions have peak flux densities <70 mJy, see Fig. 2. Most ofthe HIPASS detections below 70 mJy have larger uncertainties,while our survey becomes incomplete only at <20 mJy. Thiscompares well with the distribution of rms noise in our survey:the median rms level lies at 3.8 mJy. The majority of detectionshave an rms noise level between 2 and 6 mJy. For comparison,the rms noise for HIPASS typically is 13 mJy, though expectedto be slightly higher in the Galactic plane. This indicates that weare sensitive enough to detect M∗ galaxies in the GA region –contrary to the blind HIPASS.
Comparing integrated flux densities with HIPASS gives a1σ-dispersion of 25% of the flux for 23 measurements (uncer-tain measurements excluded). Reducing the acceptable HIPASSerror on velocities from 9 km s−1 to 8 km s−1 (cf. the comparisonof H i velocities above) the 1σ-dispersion is 15% of the flux (for19 measurements), which is more comparable with what we findfor the calibrators (cf. Sect. 2). Table 1 lists 14 galaxies offsetfrom the beam centre. A comparison of the corrected fluxes
3 Data provided by the ATNF under the auspices of the MultibeamSurvey Working Group, see http://www.atnf.csiro.au/research/multibeam/release/
2769 ± 10 H i HIZOA IC4585 3671: 3638 ± 40 opt RC32774 ± 6 H i HIPASS WKK5768 5422 5426 ± 10 H i RC3
WKK2542 684 694 ± 6 H i HK01 5428 ± 6 H i HIPASS680 H i BD99 WKK5796 5372 5260 ± 60 opt RC3688 ± 3 H i HIPASS-BGC WKK5993 3443: 3487 ± 108 opt WK04687 ± 5 H i HIPASS WKK5999 3244 3250 ± 38 opt WK04
WKK2576 3883: 3948 ± 70 opt DN97 3246 ± 6 H i HIPASS3876 ± 85 opt RS06 WKK6181 3331 3278 ± 70 opt VY963872 ± 5 H i HIPASS 3308 ± 70 opt WK99
WKK3107 3088 3090 ± 7 H i HIPASS 1340 ± 85 opt RS06WKK3139 2826 2844 ± 70 opt VY96 1499 ± 5 H i HIPASS
2823 ± 7 H i HIPASS WKK7776 2791 2790 ± 3 H i HIPASS-BGCWKK3191 3192 3187 ± 6 H i HIPASS 2790 ± 5 H i HIPASSWKK3278 2918 3118 ± 40 opt FW98 Y395-4 4904 4896 ± 43 opt FH95WKK3285 3010 3016 H i RK02 4895 ± 9 H i TH07
3016 ± 3 H i HIPASS-BGC3017 ± 5 H i HIPASS
A. C. Schröder et al.: Parkes H I observations of galaxies behind the southern Milky Way. II. 1057
Fig. 2. Histogram of peak flux density in mJy of our detections (open)and of the detections in common with HIPASS (hashed). Cross-hasheddetections are HIPASS detections with errors ≥10 km s−1. Note thatthere are three more detections by both surveys beyond the frame ofthe plot between 400 mJy and 800 mJy.
with HIPASS confirms that corrections for distances up to halfthe beam width (i.e., 7.′5) are acceptable.
4. The non-detections
A further 152 galaxies that were observed in the Crux and GA re-gions were not detected. They are listed in Table 4 with thesearched velocity range as well as the rms within that inter-val. Some spectra did reveal a signal, but careful investigationshowed them to be due to close neighbours rather than the tar-geted galaxies. These cases are marked with a plus in Col. 1 ofTable 4 (see also Table 1), and the identification of the signal isgiven in the footnote. Some of these cases are discussed in detailin Appendix A.
Columns 1–11: same as in Table 1. CGMW4# in Col. 2stands for the 4th Catalog of Galaxies Behind the Milky Way(Roman et al. 2000).
Column 12: the searched velocity range in km s−1.Column 13: the rms noise of the searched velocity range in
mJy, typically of the order of 4 mJy. These values were deter-mined after baseline fitting over a width of 1600 km s−1 – hencesimilar to the determination for detections – centred at increas-ingly higher redshifts in order to obtain values for the wholevelocity range. The quoted values represent the highest rms forthe velocity intervals, the rms for the nearer velocities are onaverage slightly lower.
Column 14: perturbed velocity intervals, mainly due to recur-ring RFI around 800, 1250 and ∼7400 km s−1, very strong GPS(Global Positioning System) signals around 8300−8500 km s−1,and detections of other galaxies. In these intervals a signal wouldhave gone undetected.
Column 15: a star indicates a footnote for this entry.Column 16: the distance in arcminutes of the targeted galaxy
to the centre of the beam. Given the falloff of sensitivity with dis-tance from the centre of the beam, any upper limits for flux den-sities calculated from the rms of such cases are underestimated.
Columns 17–19: independent velocity determinations and er-ror for the non-detected galaxies. The reference coding (Col. 18)is as in Table 3, and Col. 19 gives the origin of the measurement(optical or H i).
Table 3. References for independent velocity determinations.
BD99: Banks et al. (1999)CF97: Coté et al. (1997)DN96: Di Nella et al. (1996)DN97: Di Nella et al. (1997)DT90: Djorgovski et al. (1990)D91: Dressler (1991)F83: Fairall (1983)FW98: Fairall et al. (1998)FW06: Fairall & Woudt (2006)FH95: Fisher et al. (1995)HW00: Hasegawa et al. (2000)HIZSS: Henning et al. (2000)HIPASS: HIPASS (2006)HG95: Huchra et al. (1995)HK01: Huchtmeier et al. (2001)JS00: Juraszek et al. (2000)KD04: Koribalski & Dickey (2004)HIPASS-BGC Koribalski et al. (2004)MF96: Mathewson & Ford (1996)MH91: Mould et al. (1991)PT03: Paturel et al. (2003)RS06: Radburn-Smith et al. (2006)RK02: Ryan-Weber et al. (2002)SE95: Sanders et al. (1995)SH92: Strauss et al. (1992)TH07: Theureau et al. (2007)RC3: de Vaucouleurs et al. (1991)Vv92: Visvanathan & van den Bergh (1992)VY96: Visvanathan & Yamada (1996)WK99: Woudt et al. (1999)WK04: Woudt et al. (2004)
Based on this table, only 42% of the 149 pointings have anunperturbed velocity range, and 52% of the pointings are RFIfree (i.e., 18 pointings are affected by the detection of a galaxy,either in the ON or in the OFF scan). Table 5 lists the frequen-cies of the noted velocity ranges affected by RFIs which affectthe possible detection of a galaxy. Note that the single 10-minscans show many more RFIs, most of which, however, could beexcised successfully. The worst affected velocity ranges are ei-ther very low (800−1350 km s−1 for 23% of pointings) or around8300−8500 km s−1 for 14% of the cases. In 8% of the cases thevelocity range 7000−7700 km s−1 shows some problems.
WKK 3836 is the only galaxy that we have not detected butwas subsequently detected by HIPASS. On the one hand, ourrms of 7 mJy is fairly high (only 13% of our detection have anrms of 7 mJy and higher) and the pointing is d = 8.′5 away fromthe galaxy position (which means the signal would be reducedby a factor of 2.4). On the other hand, the HIPASS detectionis weak (the peak flux density is 37 mJy and the error on thevelocity at 12 km s−1 is the second highest value in our sampleof HIPASS galaxies).
5. Velocity distribution and detection rate
Figure 3 shows the Crux/GA search area (outlined regions)in Galactic coordinates with the optically discovered galaxies(D <∼ 0.m2) plotted as small dots (Woudt & Kraan-Korteweg2001). The 314 galaxies observed with the Parkes radio tele-scope (indicated with larger symbols) are distributed fairly ho-mogeneously over the galaxy density distribution – leading nat-urally to a larger number of observations in the high density area
1058 A. C. Schröder et al.: Parkes H I observations of galaxies behind the southern Milky Way. II.Ta
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l�ga
lbTy
peD×d
BJ
E(B−V
)V
obs
rang
erm
sV
pert
rang
eN
dist
Vot
her
Ref
orig
in(h
ms)
(deg
′′′ )
(deg
)(d
eg)
(′′)
(m)
(m)
kms−
1m
Jykm
s−1
(′ )km
s−1
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
(13)
(14)
(15)
(16)
(17)
(18)
(19)
WK
K01
9911
0724
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022
4029
4.35−9
.26
SY5
58×
3015
.90.
2360
0−
5800
4.8
WK
K03
31E
SO06
3-G
019
M11
4400
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821
3529
6.76−6
.30
S5
73×
2316
.00.
3560
0−1
3600
4.4
1256
5±2
50FW
98op
tW
KK
0338
ESO
064-
G00
1M
1145
09.1−7
150
2729
7.76−9
.64
S4
70×
2316
.00.
3050
0−1
3350
4.1
7313±1
00FW
98op
tW
KK
0411
ESO
171-
G00
2I
1154
15.3−5
409
3929
4.54
7.78
SR
60×
4015
.60.
2760
0−1
3600
3.6
5359±
77V
V92
opt
WK
K04
25M
1155
15.5−5
520
2829
4.94
6.66
SB5
42×
3816
.30.
2770
0−1
0450
3.6
7500−
7750
WK
K04
28I
1155
24.9−5
654
5829
5.31
5.12
?54×
1616
.80.
4450
0−1
0450
2.5
1150−
1300
WK
K05
85E
SO17
1-G
006
M12
0428
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356
0929
5.98
8.30
S5
87×
1116
.30.
2070
0−1
0350
3.1
8382±1
34W
K04
opt
8112±
85R
S06
opt
Y21
7-21
ESO
217-
G02
1M
I12
0443
.7−5
228
4929
5.75
9.74
S4
63×
917
.5L
0.14
450−1
0450
3.0
7400−
8750
8074±
39FH
95op
t79
63±
85R
S06
opt
WK
K06
33M
1206
37.6−6
818
4429
8.79−5
.80
S5
40×
518
.10.
3539
50−1
1100
4.6
WK
K09
75M
1223
48.8−5
956
4129
9.48
2.74
S5
43×
718
.31.
2260
0−
5700
4.4
WK
K15
84M
1257
51.2−5
601
1830
3.83
6.84
S3
40×
917
.30.
3560
0−
5700
4.2
WK
K15
97M
1258
38.9−7
135
0930
3.51−8
.72
S56×
917
.60.
3050
00−1
0450
3.0
8100−
8950
WK
K16
94+
ESO
173-
G00
2M
I13
0222
.9−5
617
3530
4.46
6.55
S4:
78×
1716
.10.
3360
0−1
0350
3.1
6350−
6700
*59
57±
85R
S06
opt
WK
K17
07M
1302
57.6−6
603
5030
4.10−3
.22
S26×
1117
.50.
7945
0−1
0350
3.9
WK
K18
06M
1307
00.4−6
719
2330
4.44−4
.50
S54×
2416
.30.
5360
0−1
0000
3.7
1000
0−1
0350
WK
K18
22E
SO17
3-G
006
MI
1307
17.9−5
407
3530
5.28
8.67
SR
560×
3015
.90.
3840
0−1
3600
5.3
0.1
7730±
30W
K04
opt
8016±
70V
Y96
opt
7777±
85R
S06
opt
WK
K18
27E
SO06
5-G
005
M13
0752
.5−7
155
1730
4.22−9
.09
S6
51×
3816
.20.
2940
0−1
0250
3.1
6950−
7200
8200−
8750
WK
K18
83M
I13
0930
.4−5
728
1630
5.37
5.32
S3
32×
1217
.30.
4640
0−
5700
3.4
2.2
6801±
70V
Y96
opt
5657±
38W
K04
opt
5666±
85R
S06
opt
WK
K18
8413
0959
.3−7
144
0730
4.40−8
.92
SB5
51×
4016
.20.
3060
0−1
0450
3.8
6950−
7350
WK
K18
8813
0944
.8−5
752
4330
5.37
4.91
S40×
2216
.60.
4460
0−1
0250
3.9
9250−
9450
6413±1
46W
K04
opt
WK
K18
91M
1310
24.4−7
201
3730
4.41−9
.21
SL
54×
817
.90.
2535
0−1
0450
4.3
WK
K19
0913
1028
.3−5
618
1330
5.59
6.47
SL
51×
2816
.50.
5970
0−1
0450
3.8
WK
K20
42E
SO17
3-G
009
I13
1547
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629
4030
6.31
6.22
SL
81×
3015
.60.
6260
0−1
0450
3.5
1005
0−1
0250
6012±
70FW
06op
tW
KK
2049
1315
58.5−5
747
2930
6.21
4.92
S6:
58×
1117
.20.
5970
0−1
0450
4.1
7150−
7700
WK
K20
60M
I13
1628
.6−5
834
5530
6.20
4.13
S7?
50×
1616
.80.
8560
0−
9850
4.1
7800−
8750
WK
K21
01I
1318
50.2−5
736
0930
6.61
5.07
I9:
47×
2416
.70.
7540
0−1
0250
3.4
1025
0−1
2550
*W
KK
2134
1321
07.8−6
900
0730
5.60−6
.28
SL
43×
917
.80.
5260
0−1
0350
3.7
WK
K21
43M
1321
46.3−5
649
2330
7.09
5.80
S4
59×
1116
.90.
7720
0−1
0250
5.6
800−
1100
5369±1
99FW
98op
tW
KK
2296
M13
3102
.2−5
509
3930
8.61
7.27
SL
58×
3115
.80.
4760
0−1
0550
4.6
WK
K23
00M
1331
33.1−5
750
0530
8.27
4.62
S5
38×
1217
.00.
6510
0−
7050
10.7
5897±
85R
S06
opt
WK
K23
3313
3331
.8−5
528
3430
8.92
6.91
S6
55×
1317
.00.
5060
0−1
0350
5.3
WK
K23
37M
1333
44.0−5
514
2830
8.98
7.13
I38×
2016
.90.
4930
0−1
0350
4.1
800−
1100
3700−
3900
WK
K23
76M
1336
35.1−5
719
5930
9.02
5.00
SL
60×
2316
.30.
6860
0−1
0450
3.5
WK
K24
5313
4053
.2−5
315
5731
0.38
8.89
S4
40×
1516
.70.
3740
0−1
0250
3.2
8200−
9050
WK
K24
93I
1344
10.8−7
116
1330
7.18−8
.84
S2
36×
3016
.10.
3750
0−
5600
4.4
0.6
7259±
35FH
95op
t72
20±
45FW
98op
t
A. C. Schröder et al.: Parkes H I observations of galaxies behind the southern Milky Way. II. 1059
Tabl
e4.
cont
inue
d.
Iden
t.O
ther
IRR
AD
ecga
l�ga
lbTy
peD×d
BJ
E(B−V
)V
obs
rang
erm
sV
pert
rang
eN
dist
Vot
her
Ref
orig
in(h
ms)
(deg
′′′ )
(deg
)(d
eg)
(′′)
(m)
(m)
kms−
1m
Jykm
s−1
(′ )km
s−1
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
(13)
(14)
(15)
(16)
(17)
(18)
(19)
WK
K25
19E
SO06
6-G
002
M13
4626
.7−6
942
2630
7.70−7
.35
SB4
51×
2815
.80.
3080
0−1
0550
2.6
7500−
7900
2071±2
50FW
98op
tW
KK
2564
1349
49.6−5
737
2631
0.71
4.36
SL
43×
1916
.70.
6010
50−1
0250
4.9
WK
K28
7314
0303
.5−6
531
5831
0.26−3
.69
31×
1117
.60.
7070
0−1
0350
4.3
1200−
1350
7700−
8550
WK
K28
74M
I14
0236
.3−5
305
5231
3.62
8.29
S7:
35×
1916
.80.
4960
0−
5800
4.7
1.1
6000±
70V
Y96
opt
5819±
85R
S06
opt
WK
K28
92M
1404
07.6−5
254
30:
313.
898.
41S
767×
3816
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4330
0−1
0350
3.9
3550−
3800
*7.
513
844±
85R
S06
opt
WK
K28
93M
1404
14.4−7
107
4630
8.80−9
.09
S4
55×
1916
.00.
2970
0−1
0450
3.9
7150−
7450
WK
K28
9514
0356
.6−6
603
0331
0.21−4
.21
S46×
917
.40.
5130
0−1
0250
4.0
900−
1150
WK
K29
5814
0646
.0−6
506
5231
0.75−3
.39
SY31×
1717
.10.
7130
0−1
0250
6.0
WK
K30
2314
1048
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019
0731
2.61
1.05
SE
?43×
1516
.64.
3250
0−1
0450
4.4
1005
0−1
0250
WK
K30
41M
I14
1308
.6−7
100
2130
9.54−9
.19
SP
47×
2816
.10.
3460
0−
9800
4.1
8400−
8900
1.3
7533±
70V
Y96
opt
7604±
70FW
98op
tW
KK
3072
MI
1415
21.8−6
731
3131
0.84−5
.95
S66×
817
.40.
4640
0−1
0450
4.7
8200−
8550
WK
K31
28+
1419
24.5−5
513
4231
5.32
5.51
SL
56×
1516
.70.
6360
0−1
0550
3.6
4150−
4500
*W
KK
3136
1421
09.2−7
120
3931
0.04−9
.72
54×
2216
.30.
2560
0−1
0450
3.8
WK
K31
6314
2429
.2−7
037
2731
0.56−9
.14
SL
56×
717
.60.
3260
0−1
0350
3.4
8000−
8500
WK
K32
66M
1434
37.0−5
238
4231
8.36
7.11
S7:
55×
917
.30.
5340
0−1
0450
4.6
WK
K32
79M
I14
3606
.5−5
424
5131
7.87
5.39
S?
38×
1217
.20.
7560
0−
9800
5.2
3100−
3350
1.1
3118±
40FH
95op
tW
KK
3296+
M14
3731
.0−5
353
2531
8.27
5.79
SL
60×
2416
.20.
7740
0−1
0400
3.7
2950−
3200
*W
KK
3346
ESO
067-
G00
3M
1443
45.3−7
007
4931
2.26−9
.32
S3:
63×
1616
.40.
2640
0−1
0350
3.1
8000−
8350
5147±1
00FW
98op
tW
KK
3357
M14
4444
.8−6
734
2231
3.44−7
.04
SB5
56×
4615
.40.
3455
0−1
0450
4.0
WK
K33
72M
1446
38.7−6
626
5831
4.09−6
.11
S5
67×
3215
.20.
3055
0−1
0450
3.5
7050−
7700
WK
K38
2313
5733
.1−5
206
4331
3.13
9.45
SM
:20×
618
.60.
4430
0−1
0550
7.3
650−
1000
*8.
727
483±
85R
S06
opt
WK
K38
3614
0006
.4−5
203
0231
3.53
9.40
SL
83×
1516
.40.
4230
0−1
0550
7.3
650−
1000
*8.
536
12±
12H
IPA
SSHi
WK
K39
91M
I14
2730
.8−5
207
1531
7.55
8.00
SM
34×
818
.00.
4060
0−
5700
6.1
0.8
1716
4±
52FH
95op
t16
968±
85R
S06
opt
WK
K47
51M
1514
36.0−4
812
4132
6.11
8.11
SY5
56×
1916
.50.
4040
0−1
0250
5.1
650−
1100
*2.
9W
KK
4755
M15
1450
.4−4
812
4432
6.15
8.09
SM
:58×
3515
.80.
4040
0−1
0250
5.1
650−
1100
*2.
9Y
68-3
LE
SO06
8-G
003
I15
2015
−69
0252
:31
5.61−9
.92
S72×
2415
.6N
0.11
300−
5500
5.4
1.1
4981±
37FH
95op
tW
KK
4907
MI
1525
06.2−4
849
0332
7.26
6.66
S5
40×
1616
.90.
3960
0−
9700
7.9
0.8
1052
5±
70V
Y96
opt
WK
K49
8915
2948
.8−5
359
3432
4.95
1.97
S43×
1117
.12.
6930
0−1
0250
4.0
1100−
1350
WK
K50
3915
3236
.7−6
252
3332
0.16−5
.53
SL
?42×
2016
.30.
4840
0−1
0250
3.6
1100−
1300
WK
K50
6115
3329
.7−6
021
3832
1.71−3
.54
S23×
1317
.00.
8360
0−1
0350
4.0
WK
K51
2415
3712
.1−6
025
0932
2.05−3
.85
?I24×
2016
.80.
7140
0−1
0250
5.6
WK
K51
31M
1537
41.6−6
233
0632
0.83−5
.61
20×
1217
.40.
5030
0−1
0250
5.0
1449
8±
54W
K04
opt
WK
K51
38M
1538
05.3−5
947
1332
2.51−3
.41
S46×
3515
.51.
0220
0−1
0250
3.6
650−
1000
WK
K51
86M
I15
4044
.8−6
005
2232
2.60−3
.85
S6
46×
2615
.50.
7460
0−1
0250
5.7
0.7
5151±
70V
Y96
opt
WK
K51
95M
I15
4111
.6−5
958
5032
2.71−3
.80
S28×
1716
.70.
7330
0−1
0250
5.9
5918±
70V
Y96
opt
WK
K51
9615
4114
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038
3432
2.31−4
.33
S24×
717
.60.
5930
0−1
0250
5.7
WK
K52
5115
4516
.8−5
921
4532
3.49−3
.62
S20×
817
.90.
8030
0−1
0250
6.1
WK
K52
67+
1546
47.8−6
624
0431
9.25−9
.26
S62×
816
.90.
1360
0−1
0450
3.4
4550−
5050
*W
KK
5268
M15
4619
.5−5
853
2032
3.89−3
.33
S24×
1116
.90.
6130
0−1
0350
6.3
5541±
46W
K04
opt
1060 A. C. Schröder et al.: Parkes H I observations of galaxies behind the southern Milky Way. II.Ta
ble
4.co
ntin
ued.
Iden
t.O
ther
IRR
AD
ecga
l�ga
lbTy
peD×d
BJ
E(B−V
)V
obs
rang
erm
sV
pert
rang
eN
dist
Vot
her
Ref
orig
in(h
ms)
(deg
′′′ )
(deg
)(d
eg)
(′′)
(m)
(m)
kms−
1m
Jykm
s−1
(′ )km
s−1
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
(13)
(14)
(15)
(16)
(17)
(18)
(19)
WK
K52
88M
1547
21.5−6
014
1832
3.16−4
.47
SL
52×
1915
.90.
5860
0−1
0350
5.4
WK
K52
97+
1547
41.7−5
859
2732
3.97−3
.52
S7
51×
1915
.80.
6060
0−1
0450
5.3
5300−
5650
*43
43±
52W
K04
opt
5950−
6150
WK
K53
3015
4906
.3−6
042
3932
3.03−4
.97
S9
63×
3415
.10.
6160
0−1
0550
3.8
WK
K53
34M
1549
19.8−6
155
5932
2.29−5
.94
S?
44×
2015
.80.
3530
0−1
0350
4.2
8350−
8650
6038±
33W
K04
opt
WK
K53
49M
I15
4942
.0−6
100
3432
2.90−5
.25
S5:
38×
916
.90.
4830
0−1
0250
4.2
WK
K53
57M
1549
52.4−5
842
5632
4.36−3
.48
SM
44×
2315
.80.
6360
0−1
0350
4.3
5447±
44W
K04
opt
WK
K53
81+
D15
5105
.4−5
835
2832
4.56−3
.48
S32×
1516
.70.
6430
0−1
0150
3.8
2000−
2150
*55
18±
98W
K04
opt
WK
K54
24I
1552
54.2−5
834
5332
4.75−3
.62
?S19×
1617
.10.
6230
0−1
0350
4.7
4350−
4600
WK
K54
43+
M15
5337
.7−5
841
3032
4.76−3
.77
S5:
38×
1216
.60.
7515
0−1
0350
4.0
2850−
3050
*50
69±
40W
K04
opt
WK
K54
82I
1554
51.3−5
652
0832
6.05−2
.47
?I?
71×
6014
.91.
1420
0−1
0350
4.2
1150−
1450
WK
K54
90M
1555
23.9−5
814
3032
5.22−3
.57
S27×
1217
.10.
7460
0−1
0550
4.5
WK
K55
28M
1556
49.3−6
148
5932
3.04−6
.42
S5:
60×
916
.70.
4760
0−1
0250
4.2
WK
K55
34+
1556
58.6−5
906
2632
4.82−4
.36
S9:
43×
2615
.80.
5630
0−1
0350
4.1
5300−
5800
*W
KK
5544+
M15
5733
.1−6
321
4132
2.10−7
.65
SM
51×
1316
.10.
2610
0−1
0250
3.5
4450−
4850
*68
50−
7150
8000−
8700
WK
K55
56+
M15
5733
.3−5
901
0632
4.93−4
.34
S22×
1516
.60.
5211
00−
8100
4.6
5400−
5900
*46
58±1
62W
K99
opt
WK
K55
63M
1557
54.4−6
053
1832
3.75−5
.80
S35×
1516
.50.
4560
0−1
0550
3.6
1306
0±1
02W
K04
opt
WK
K55
68M
1558
13.2−6
253
1332
2.47−7
.34
S3:
65×
1615
.60.
3430
0−1
0250
3.5
850−
1000
7460±
70D
N97
opt
WK
K55
81+
1558
53.3−6
617
5532
0.26−9
.96
SB4:
58×
3914
.80.
1140
0−1
0250
4.1
3450−
3900
*97
50±
70D
N97
opt
6800−
7150
8350−
8700
WK
K55
9515
5840
.7−5
727
1032
6.07−3
.25
I?
30×
1916
.80.
6630
0−1
0250
5.5
800−
1100
0.7
WK
K55
9615
5916
.0−6
502
1332
1.13−9
.03
SL
50×
2615
.40.
1340
0−1
0250
3.2
1100−
1300
WK
K55
9715
5845
.7−5
727
2632
6.07−3
.26
SL
?28×
1117
.30.
6730
0−1
0250
5.5
800−
1100
WK
K56
15M
I15
5922
.2−6
001
2432
4.45−5
.26
SM
42×
1216
.50.
3860
0−
7700
5.7
3936±
37FH
95op
t38
67±
70W
K99
opt
WK
K56
47M
1600
14.4−6
022
2232
4.31−5
.59
SL
44×
3115
.40.
3540
0−1
0250
4.6
WK
K56
50I
1600
18.1−6
025
2032
4.28−5
.63
SM
52×
1915
.60.
3430
0−1
0350
4.5
8300−
8600
WK
K56
93M
1601
36.8−5
904
4432
5.29−4
.73
S?
42×
2415
.60.
3730
0−1
0250
5.9
650−
1000
WK
K56
94+
DI
1601
48.3−6
108
5432
3.94−6
.30
SM
66×
3814
.70.
3340
0−
9700
4.0
8100−
8950
*34
12±
36FH
95op
t35
05±
50W
K04
opt
WK
K57
09+
M16
0212
.6−6
059
1032
4.08−6
.21
SD?
46×
2615
.50.
3220
0−1
0250
5.0
5600−
5800
*W
KK
5733++
M16
0250
.2−6
110
0732
4.02−6
.40
S3
54×
916
.40.
3136
50−
8950
3.8
4150−
4500
*62
15±
92W
K99
opt
5500−
5850
WK
K57
80+
1604
11.7−6
107
4632
4.17−6
.48
S6
56×
3515
.20.
2930
0−1
2950
4.4
5100−
5700
*W
KK
5791
1604
11.9−5
909
2832
5.49−5
.01
S5:
95×
1615
.20.
3220
0−1
0250
4.7
800−
1000
WK
K58
01M
1604
24.8−5
940
1932
5.16−5
.41
SM
44×
2615
.30.
3460
0−1
0450
4.5
WK
K58
05+
ESO
136-
G01
8M
1604
37.5−6
046
3232
4.44−6
.25
S5
71×
1615
.50.
3034
50−
8950
5.6
6207±2
30W
K99
opt
WK
K59
23M
I16
0753
.1−5
913
3732
5.79−5
.38
SR
350×
2815
.20.
3824
00−
7900
5.3
4514±
42SH
92op
tW
KK
5928
ESO
100-
G01
116
0820
.8−6
257
3932
3.28−8
.16
S5
90×
2814
.60.
1840
0−1
0250
4.2
8354±1
30W
K04
opt
WK
K59
71M
1609
24.3−6
241
1832
3.56−8
.04
43×
2315
.90.
2030
0−1
0250
4.1
8350−
8650
A. C. Schröder et al.: Parkes H I observations of galaxies behind the southern Milky Way. II. 1061
Tabl
e4.
cont
inue
d.
Iden
t.O
ther
IRR
AD
ecga
l�ga
lbTy
peD×d
BJ
E(B−V
)V
obs
rang
erm
sV
pert
rang
eN
dist
Vot
her
Ref
orig
in(h
ms)
(deg
′′′ )
(deg
)(d
eg)
(′′)
(m)
(m)
kms−
1m
Jykm
s−1
(′ )km
s−1
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
(13)
(14)
(15)
(16)
(17)
(18)
(19)
WK
K59
83M
1609
52.5−6
500
4832
1.99−9
.77
S47×
3015
.50.
1440
0−1
0250
4.3
1100−
1300
1505
0±
70D
N97
opt
1483
8±1
78W
K99
opt
WK
K60
07E
SO13
6-G
021
M16
1009
.5−6
125
6032
4.49−7
.19
SB2
75×
5814
.10.
2310
0−1
0250
4.2
5750−
5950
WK
K60
5516
1050
.2−5
625
5932
7.98−3
.59
SL
43×
1716
.70.
5820
0−1
0250
3.8
900−
1050
WK
K60
90D
1611
51.8−6
111
4232
4.81−7
.15
SY5
31×
2016
.20.
2360
0−1
0350
5.1
WK
K60
92+
M16
1151
.4−6
037
5532
5.20−6
.74
SB2
56×
4714
.70.
1960
0−1
0350
2.1
4900−
5100
*46
88±
38W
K99
opt
8200−
8750
4711±
58W
K04
opt
WK
K61
5416
1241
.8−5
654
0932
7.85−4
.11
SL
32×
1916
.70.
5020
0−1
0350
3.7
900−
1050
8050−
8850
WK
K61
62M
1613
13.8−6
234
5432
3.96−8
.27
SY44×
1715
.90.
1710
0−1
0350
2.1
WK
K61
76E
SO13
6-G
001
MI
1613
27.2−6
045
5132
5.25−6
.98
S5
86×
3114
.60.
2130
0−1
0350
6.8
4630±
58W
K99
opt
WK
K61
87D
1613
42.4−6
217
1432
4.20−8
.09
22×
2216
.80.
1560
0−1
0550
5.2
7400−
7600
0.9
WK
K61
8916
1344
.9−6
217
0432
4.21−8
.10
E13×
817
.30.
1460
0−1
0550
5.2
7400−
7600
WK
K62
49M
1614
53.5−6
253
0932
3.88−8
.62
S5
51×
2015
.70.
1430
0−1
0350
3.1
8350−
8650
WK
K62
51M
1614
45.0−6
055
3632
5.25−7
.20
S4
36×
1815
.90.
2013
50−1
0250
27.6
8350−
8750
*56
89±1
00W
K99
opt
WK
K62
8616
1514
.1−6
016
5932
5.74−6
.78
S20×
518
.50.
2724
00−
7900
4.0
7.4
WK
K63
68E
SO13
7-G
013
M16
1651
.5−6
221
0632
4.42−8
.40
SY5
74×
1915
.50.
1360
0−1
0450
4.4
1324
2±
34W
K04
opt
WK
K64
59M
1618
26.7−6
046
4732
5.68−7
.41
S5:
62×
4314
.80.
2620
0−1
0250
6.5
1100−
1400
5268±
35W
K08
opt
WK
K65
41M
1620
00.9−6
000
4732
6.36−7
.01
SYM
42×
2715
.60.
2130
0−1
0250
2.6
8350−
8550
WK
K66
40C
SRG
0801
M16
2146
.8−6
125
3132
5.50−8
.15
SR
56×
4314
.90.
2040
0−1
0250
3.3
1150−
1450
4147±
71W
K04
opt
WK
K66
63M
1622
20.3−6
121
2832
5.60−8
.15
S2
85×
2015
.00.
2130
0−1
0350
5.0
1150−
1300
3062±
70W
K99
opt
WK
K67
6816
2425
.1−5
618
4132
9.42−4
.82
S5:
39×
1916
.20.
3630
0−1
0350
11.5
700−
1000
WK
K68
3016
2547
.8−5
610
5532
9.65−4
.87
SM
:35×
1916
.20.
3730
0−1
0350
4.7
800−
1050
8350−
8700
WK
K70
37M
1631
05.3−5
949
0632
7.47−7
.87
S5
42×
1516
.50.
2425
00−
7800
5.3
1872
2±
71W
K04
opt
WK
K70
42M
1631
00.4−5
645
3532
9.72−5
.79
S5:
78×
4214
.60.
3530
0−1
0250
5.2
850−
1050
4800−
5100
WK
K71
75+
M16
3541
.2−6
009
3632
7.60−8
.53
S5:
39×
916
.80.
2416
00−
6750
6.7
3250−
3500
*W
KK
7177
ESO
137-
G03
5M
1635
50.8−6
127
6032
6.63−9
.41
S3
112×
3614
.30.
2524
00−
7900
4.9
4780±
60R
C3
opt
WK
K72
48+
ESO
137-
G03
7M
1639
18.5−5
953
1132
8.11−8
.69
S3
106×
2214
.80.
2824
00−
7900
4.4
5450−
5600
*54
30±
50R
C3
opt
WK
K73
2016
4205
.3−5
549
1133
1.46−6
.30
S5
67×
2415
.30.
3120
0−1
0250
3.5
WK
K73
75M
1644
37.9−6
051
0532
7.80−9
.81
S70×
2215
.10.
2630
0−1
0250
4.6
800−
1000
Y45
3-3
ESO
453-
G00
3M
I16
4635
.2−3
135
2135
0.44
8.86
S3
60×
3013
.6I
0.43
600−
5800
4.6
0.1
6644±
10M
F96
opt
WK
K76
25M
1652
14.6−5
940
1032
9.34−9
.80
SB5
65×
5414
.80.
2110
0−1
0250
2.8
1200−
1350
1427
8±
40W
K04
opt
1432
2±
85R
S06
opt
WK
K76
3516
5214
.4−5
516
3933
2.80−7
.06
?I?
78×
5414
.70.
2630
0−1
0250
4.7
WK
K76
89+
1653
48.6−5
905
2432
9.92−9
.60
I74×
4315
.20.
1330
0−1
0250
6.5
1300−
1700
*15
59±
3H
K01
Hi
1655±
KD
04Hi
WK
K77
2616
5450
.5−5
517
0333
3.03−7
.35
SB10
5×74
14.1
0.30
500−1
0250
3.8
1200−
1350
Y45
3-11
ESO
453-
G01
1M
I16
5642
.5−3
137
1635
1.78
7.16
S3
78×
1815
.8N
0.33
500−
9700
6.3
0.1
7028±
1H
W00
opt
WK
K77
94+
MI
1658
40.8−5
829
0633
0.80−9
.73
SB4
51×
4415
.10.
1950
0−
5800
5.4
*0.
858
54±
70V
Y96
opt
WK
K78
5317
0144
.2−5
257
1433
5.51−6
.72
S5
52×
1516
.20.
3930
0−1
0350
8.8
700−
1050
Y17
030-
48M
I17
0643
.5−4
823
5933
9.64−4
.61
S48×
0.86
400−
9800
5.5
8750−
8900
0.5
1062 A. C. Schröder et al.: Parkes H I observations of galaxies behind the southern Milky Way. II.Ta
ble
4.co
ntin
ued.
Iden
t.O
ther
IRR
AD
ecga
l�ga
lbTy
peD×d
BJ
E(B−V
)V
obs
rang
erm
sV
pert
rang
eN
dist
Vot
her
Ref
orig
in(h
ms)
(deg
′′′ )
(deg
)(d
eg)
(′′)
(m)
(m)
kms−
1m
Jykm
s−1
(′ )km
s−1
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
(13)
(14)
(15)
(16)
(17)
(18)
(19)
Y51
9-9
ESO
519-
G00
9I
1711
44.2−2
544
4835
8.51
8.03
S5
73×
815
.6N
0.49
500−
9800
4.9
8300−
8800
6259±
50D
T90
opt
6335±
15PT
03Hi
WK
K80
7417
1500
.5−5
408
2633
5.71
−9.0
1SR
555×
2415
.90.
2030
0−1
0250
5.8
1100−
1300
WK
K80
90M
1716
04.6−5
446
5533
5.26
−9.5
0S
559×
1216
.40.
2120
0−1
0350
4.9
WK
K81
63M
1722
28.6−5
419
4533
6.17−1
0.02
S7:
50×
1516
.30.
2060
0−1
0550
5.8
WK
K81
65M
I17
2234
.7−5
242
0433
7.56
−9.1
4S
358×
1316
.00.
2350
0−
9800
4.6
0.7
Y17
477-
40M
I17
5118
−40
2625
:35
0.70
−6.9
0S
24×
16.8
N0.
3250
0−
9800
5.4
8200−
9050
2.4
1280
8±
38FH
95op
tY
1813
9-37
CG
MW
4-04
33M
I18
1721
−37
2108
:35
5.87
−9.8
9S
42×
1816
.5N
0.10
500−
9800
4.8
1200−
1300
0.5
7214±
70V
Y96
opt
Not
es:
WK
K16
94:
dete
cted
WK
K16
96;
WK
K21
01:
the
velo
city
rang
e10
250−
1255
0ha
san
rms
of6.
1;W
KK
2892
:th
epo
intin
glie
sbe
twee
nth
ega
laxi
esW
KK
2892
atd=
7.′5
and
WK
K29
34at
d=
11.′ 3
(not
liste
d);
WK
K31
28:d
etec
ted
WK
K29
93in
the
OFF
poin
ting;
WK
K32
96:d
etec
ted
WK
K32
85;W
KK
3823
and
WK
K38
36ar
ein
the
sam
ebe
amat
asi
mila
rdi
stan
cefr
omth
ece
ntre
;WK
K47
51an
dW
KK
4755
are
inth
esa
me
beam
ata
sim
ilard
ista
nce
from
the
cent
re;W
KK
5267
:det
ecte
dW
KK
5240
;WK
K52
97:d
etec
ted
WK
K52
85;W
KK
5381
:det
etce
dW
KK
5366
;WK
K54
43:d
etec
ted
HIZ
SS10
0(W
KK
5443
OFF
)in
the
OFF
poin
ting;
WK
K55
34:d
etet
ced
WK
K52
85in
the
OFF
poin
ting;
WK
K55
44:
dete
cted
WK
K52
60in
the
OFF
poin
ting;
WK
K55
56:
dete
cted
WK
K52
85in
the
OFF
poin
ting;
WK
K55
81:
dete
cted
IC45
84an
dIC
4585
;WK
K56
94:
dete
cted
WK
K57
68an
dW
KK
5729
;WK
K57
09:d
etec
ted
WK
K57
68;W
KK
5733
:det
ecte
dW
KK
5768
and
WK
K57
29;W
KK
5733
:det
etce
dW
KK
5768
and
WK
K57
29;W
KK
5780
:det
etce
dW
KK
5768
;WK
K58
05:
dete
tced
WK
K57
96;W
KK
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of the Norma cluster. The contours mark extinction levels ofAB = 1.m0 and 3.m0 following Schlegel et al. (1998). The formerindicates where previous optical surveys become incomplete,the latter where the deep optical ZOA survey becomes incom-plete (Kraan-Korteweg 2000; Woudt & Kraan-Korteweg 2001).Detected galaxies are marked by filled circles, non-detectedgalaxies by crossed squares. The detections are colour-coded forradial velocity in such a way that they emphasise the velocityspace of the GA region (blue dots; 3000 < vhel < 6500 km s−1),showing the Norma cluster and Norma Wall that (is believed to)encompass the GA overdensity. Magenta dots are at lower ve-locities, while the red dots indicate higher velocities.
The majority of the detections are found to lie in the velocityrange of the GA overdensity (3000 < vhel < 6500 km s−1). Fewnearer galaxies are detected (Vhel < 3000 km s−1), even thoughwe are sensitive to them. And very few more distant galaxieswere detected. This is partly due to the lower sensitivity at thesehigher redshifts, but also indicative of the lack of distant large-scale structures in this area.
This is further illustrated by a histogram of the heliocen-tric radial velocities for the detections presented in this paper(Fig. 4). The overall histogram shows all detections. Detectionsin the GA survey region are marked in blue, and the ones inthe Crux survey region in red. The inset shows the velocity his-tograms for the Crux and GA region separately, including theprevious work in the adjacent Hydra/Antlia survey region.
The histogram shows a markedly different behaviour fromwhat is expected for a uniform distribution of galaxies in spacegiven our rms, with a sharp drop-off at about 6000 km s−1. Thepeak – albeit quite broad – is centred roughly at 4500 km s−1
ranging from 3000−6000 km s−1, similar to the velocity rangeof the Norma cluster (Woudt et al. 2008) which completelycoincides with the predicted velocity range of the GA (Kolattet al. 1995) and the mean Norma cluster velocity (Woudt et al.2008). It is distinct from the much flatter distribution of theH i-survey undertaken under the same observing conditions forthe Hydra/Antlia survey area (top panel of inset; as in Paper I).
This is in agreement with the results by Woudt et al. (2004)who have shown that the velocity distribution of all survey galax-ies for which we obtained redshifts (about 15% on average forthe deep ZOA surveys, mostly optical spectra from our dedi-cated follow-up surveys at the SAAO and ESO, plus some pre-viously published redshifts), is fairly flat out to 20 000 km s−1
in the Hydra/Antlia region, while the Crux region and – muchmore pronounced – the GA region show a distinct broad peakof galaxies at ∼4000−5000 km s−1 (see their Fig. 5), while thehistogram is otherwise similar for the three survey regions. Theprominence of the GA overdensity around � ∼ 320◦ leads to anoverall higher fraction of nearby galaxies (V <∼ 6000 km s−1)over the sampled volume (out to about 20 000 km s−1). This maywell explain the slightly higher detection rate of 52% found forthis survey compared to Paper I (45%, with a total 148 observedgalaxies compared to 314 here). In general, the non-detectionsare for fainter and smaller galaxies (extinction-corrected), im-plying that they are most likely background galaxies beyond thevelocity search range of our survey, plus some closer-by galaxieswith an H i flux density below our sensitivity limit.
Inspection of Fig. 3 indicates that the detections and non-detections are spread quite evenly with respect to the galaxydensity of the overall galaxy distribution. We subsequently havea larger number of observations in and around the high densityarea of the Norma cluster. A relatively higher fraction of obser-vations were also made at higher extinction levels: (i) in the sus-pected extension of the Norma Wall across the Galactic plane,
A. C. Schröder et al.: Parkes H I observations of galaxies behind the southern Milky Way. II. 1063
330 320 310 300
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GALACTIC LONGITUDE
Fig. 3. Distribution of galaxies in the Crux and GA ZOA regions. Filled circles indicate the 162 21 cm detections, crosses in squares the 152 non-detections. The small dots represent the galaxies uncovered within the optical search regions (outlined areas). The contours show the dust extinctionas determined from the 100 μm DIRBE maps (Schlegel et al. 1998) at the levels AB = 1.m0 and 3.m0 (thick line). The circles are centred on theNorma cluster with 1 RA and 2 RA.
i.e., extending from the Norma cluster at (�, b, v) = (325.29◦,−7.21◦, 4821 km s−1) (Woudt et al. 2008) towards the low-latitude CIZA J1324.7–5736 and Cen-Crux clusters at (�, b, v) =(307.4◦, +5.0◦, 5700 km s−1) and (305◦, +5◦, 6214 km s−1), re-spectively (Radburn-Smith et al. 2006, see also their Fig. 4),which form part of the GA Wall; (ii) for some highly obscuredgalaxy candidates deep into the ZOA (in total 37 were observedwith AB > 3.m0 of which 20 were detected) as H i observationsare the only way to obtain a redshift for such heavily obscuredgalaxies.
Overall the detections and non-detections seem to be sim-ilarly distributed over the survey area. However, a closer lookat the Norma cluster (see also Fig. 5) reveals that the detec-tion rate within one Abell radius (RA = 1.◦75) of the centralcD galaxy, WKK 6292, is only 41% (ntot = 32), which is lowerthan for the whole survey on the 1σ level. A bit further out, inthe annulus 1 − 2 RA, the detection rate is similar to the rest ofthe GA/Crux survey, namely 53% (ntot = 53). Such a trend, ifreal, would be expected if there are not many spiral galaxies inthe cluster or if the spirals are H i deficient. The former is un-likely as morphological distinction between ellipticals and spi-rals is largely unaffected at the extinction levels of the Normacluster. The latter is probable since rich, massive, and X-raystrong galaxy clusters like the Norma cluster generally showH i deficiencies (Giovanelli & Haynes 1985). We explore thiseffect in more detail in Sect. 6.
6. HI deficiency in the Norma cluster
As a first measure of H i-deficiency we regard the H i-massesof the galaxies in and around the cluster as a function of
Table 5. References for independent velocity determinations.
Velocity range Counts800−1000 19
1200−1350 153200 1
3700−3800 24450 24900 15800 16000 17000 3
7200−7300 37500−7700 6
8100 18300−8500 218800−9000 2
9300 110000 1
10 100−10 300 4
cluster-centric distance. The H i masses are calculated usingMHI = 2.356 × 105D2S , where S is the H i flux integral inJy km s−1, and D the distance in Mpc calculated from the mea-sured velocity and corrected for the motion with respect to theLocal Group (Yahil et al. 1977). For galaxies assumed to lie inthe Norma cluster (i.e., within 1.5 RA and 2096 km s−1 < v <7646 km s−1, cf. Woudt et al. 2008) we adopt a distance ofD = 67 h−1
70 Mpc.Figure 6 shows histograms of the logarithm of H i mass for
galaxies in the inner region of the Norma cluster (<0.5 RA,top panel), three different annuli (0.5−1 RA; 1−1.5 RA,
1064 A. C. Schröder et al.: Parkes H I observations of galaxies behind the southern Milky Way. II.
GA
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Fig. 4. Velocity distribution of the 162 H i detections in the Crux (lightgrey/red) and GA (dark grey/blue) regions. The inset shows the detec-tions separated by regions; the detections in the Hydra/Antlia regionfrom Paper I are also shown.
Fig. 5. Distribution of the galaxies observed at 21 cm zoomed in at theNorma cluster (cf. description of Fig. 3). A third contour level at AB =2.m0 is shown as a dotted line. Non-detections with a large circle have aknown optical velocity (a black circle stands for v > 12 000 km s−1).
and 1.5−2 RA, middle panels), including for comparison theH i-mass distribution of all the 162 detections in the survey area(bottom panel). For reference, the hashed histograms are shownin accumulation in the bottom panel as well. The mean valuesand the standard deviations are indicated for each subset and forthe total region in the bottom panel. Our median value of all de-tections is log MHI = 9.86 (in units of solar mass) and compareswell with the H i mass distribution in the Northern Extension of
Fig. 6. Histogram of the logarithm of H i mass for various regions inthe Norma cluster (hashed) and the total region observed (non-hashed).The non-hashed region in the second panel from the top indicates twogalaxies (WKK 6689 and WKK 6732) with an uncertain though smallcontribution from each other. The H i mass in both cases is thereforeslightly overestimated.
the HIZOA survey (log MHI = 9.7, Donley et al. 2005) whichhas s similar sensitivity to our pointed survey. These histogramsshow that galaxies closer to the cluster core have lower H i massthan farther galaxies, although at only about the 1σ level.
In the innermost region only two galaxies (out of nine; 22%)were detected, one of which actually has a substantial H i-mass(WKK 5999 lies at d = 0.49 RA and v = 3244 km s−1). Apartfrom this galaxy, the distribution of H i mass for the galaxieswithin 1.5 RA is shifted towards the lower end as compared tothe field. This is expected if we assume that cluster membershave passed at least once through the centre of the cluster andhave undergone ram-pressure stripping. In contrast, galaxies inthe range 1.5−2 RA have an H i mass distribution comparable tothe field.
A better estimate of the effect of the cluster environmenton the H i content of the Norma spiral galaxies is the H i defi-ciency parameter (Giovanelli & Haynes 1985) which comparesthe H i content of a cluster galaxy with the average H i content ofan isolated field spiral of the same morphological type. Solaneset al. (1996) have shown that the H i content of a field spiralalso depends on the diameter. However, due to the uncertain-ties in diameter of our highly obscured galaxies we have not in-cluded the diameter dependence in our calculations. Moreover,there is uncertainty in the morphology of many of the highlyobscured galaxies. Such obscured galaxies were generally la-belled as “S” by Woudt & Kraan-Korteweg (2001) without afurther subtype. We assumed these to be late type spirals (i.e.,Scd or Sd,) as a bulge dominated spiral could have been classi-fied, whereas strongly obscured low-surface brightness irregulargalaxies would most likely have remained invisible on the opti-cal survey plate.
We note furthermore, that our sample of latest type spi-rals (Sdm − I) shows a systematic offset in H i mass compared
A. C. Schröder et al.: Parkes H I observations of galaxies behind the southern Milky Way. II. 1065
to our other morphological sub-samples. The mean H i mass ofthis latest type sample (not including the possibly H i-deficientNorma galaxies within 2 RA) is log MHI = 9.79 with a standarddeviation of 0.33. This value is typical of Scd and Sd galaxies(log MHI = 9.62, with a standard deviation of 0.31) and con-sistent with the fact that Giovanelli & Haynes (1985) find thevalue 9.09 for their field Sm − Im sample (all H i masses fromGiovanelli & Haynes were corrected for the difference of theiradopted Hubble constant of 50 km s−1 Mpc−1 to our value of70 km s−1 Mpc−1). Considering the high foreground extinctionof our sample, we assume that most of the galaxies classified aslate type S/Im were probably misclassified: it is unlikely to findmore than a couple of very late-type galaxies at these foregroundextinctions. Hence, we have calculated the H i deficiency param-eter for the Sdm − I galaxy sample using the average H i contentof field galaxies of types Scd and Sd.
The derived H i deficiency parameters are plotted as a func-tion of cluster-centric distance out to 2 RA, as illustrated in Fig. 7.The dispersion is quite large and only a very weak dependenceis seen. The least squares fit out to a radius of 2 RA has a slopeof −0.07 ± 0.12. A comparison with the respective plot for theComa cluster (Bravo-Alfaro et al. 2000, their Fig. 4) which issimilar to the Norma cluster in its cluster specific properties(Kraan-Korteweg et al. 1996; Woudt 1998), shows that we haveonly one detection within 0.4 RA, whereas Coma shows obvi-ous deficiencies for seven central galaxies. This one detection(WKK 6100) is of unknown morphological type. Revisiting theR- and J-band images and taking account of the effect of ex-tinction, it is likely that this galaxy is actually an Sc galaxy. thatwould make this galaxy more deficient.
However, the fact that we have six non-detections withind = 0.49 RA of the Norma cluster indirectly suggests that thecluster is even more H i deficient than suggested by Fig. 7. Thesegalaxies must lie below our sensitivity limit. To test this, welooked at the non-detections that have optically determined ve-locities. Based on that, we can test whether they are part of thecluster or cluster environment. These are identified with opencircles in Fig. 5. Nearly all non-detections with optically knownvelocities have velocities consistent with being part of the clus-ter (blue open circles with crosses). For these we have calculatedupper limits of the H i-mass based on our measured rms, assum-ing that we would have detected the galaxy if it had an S/N = 3,and a 50% line width typical of a spiral galaxy of 200 km s−1.These values are added to the sample’s H i deficiency parame-ters, and shown in Fig. 8.
This is not all the data available to test the H i deficiencyhypothesis. Vollmer et al. (2001) obtained ATCA radio synthe-sis imaging observations of the centre of the Norma cluster aswell as for two fields just slightly offset from the centre. In allthree fields (with a HPBW of 30′) they detected only two galax-ies (both were not observed by us). That alone presents an indi-cation of H i deficiency. Only one of their two detected galaxiesis clearly H i deficient: WKK 6489 lies at 0.36 RA and has anH i deficiency of 1.0, while the other galaxy detected by them,WKK 6801, at 0.75 RA has a normal value of −0.15.
The ATCA fields contain, however, many more spiral galaxycandidates (the reason why these fields were chosen for obser-vations). We assume that all the spiral galaxies in the ATCAfields actually are members of the Norma cluster. An inspectionof the velocity histograms of all known redshifts of galaxies inthe Norma cluster (available from Woudt et al. 2008) in rings outto 2 RA confirms that nearly all galaxies within 0.5 RA are mem-bers of the cluster, with just a very low number of outliers (seeFig. 9). Even for the outermost ATCA field (at about 0.65 RA
Fig. 7. H i deficiency parameters of Norma cluster are plotted versusdistance from the centre of the cluster in Abell radii. Open circles indi-cate unknown spiral types or early morphological types which are notincluded in the fitted line. (One RA corresponds to 1.◦75).
Fig. 8. Same as Fig. 7 but with lower limits for non-detections (trian-gles). Open symbols stand for ATCA data, filled symbols are from thepresent paper.
from the cluster centre) contamination by background or fore-ground galaxies will be minimal.
The ATCA non-detections have a 3σ detection limit of about3 mJy/beam in each velocity channel. Assuming emission to beunresolved with the 30′′ beam in each channel, the 3σ upperlimit on H i mass for these non-detections is 6 × 108 M (fol-lowing Vollmer et al. 2001, but with D = 67 Mpc rather thanD = 79 Mpc, and an assumed linewidth of 200 km s−1 ratherthan 150 km s−1). Taking this limit, the calculated H i deficiencyfor spiral galaxies in the ATCA fields are also added to Fig. 8(filled triangles). The addition of these lower limits now reveal avery clear and strong trend of H i deficiency for galaxies within0.4 RA. For the annulus from 0.4 RA to 1 RA and beyond, theH i deficiency scatters between normal values to considerablydeficient galaxies. This is consistent with what has been foundfor other rich clusters, where clear H i deficiency manifests it-self unambiguously only in the innermost core of the cluster(R <∼ 0.5 RA; see e.g., Haynes et al. 1984).
1066 A. C. Schröder et al.: Parkes H I observations of galaxies behind the southern Milky Way. II.
Velocity distribution of WKK galaxies in the Norma cluster
0
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Fig. 9. Velocity distribution of WKK (optical) detections in the Normaregion, separated by Abell radii, as indicated.
The non-detection rate can also be used to calculate anH i deficiency fraction as defined by Giovanelli & Haynes1985. In our sample, we have one detection with an H i defi-ciency >0.3 within 1 RA as well as 13 lower limits close toor above 0.3. There are an additional 8 detections and 5 non-detections which may have H i deficiencies just under 0.3. TheH i deficiency fraction in this case is at least 0.58. Böhringeret al. (1996) give an X-ray luminosity for the Norma clus-ter of 2.2(±0.3) × 1044 erg s−1 in the ROSAT energy band(0.1−2.4 keV). Figure 9 in Giovanelli & Haynes shows a rela-tionship between the H i deficiency fraction and X-ray luminos-ity in the (0.5−3.0 keV) band. The values for the Norma clusterfit well onto that relationship.
For completeness, we have checked for H i deficiency inour other galaxies. There are only two outliers, WKK 1294with (l, b, v) = (301.◦7, 10.◦1, 1919 km s−1) and WKK 1510 with(l, b, v) = (303.◦4, 7.◦0, 2668 km s−1). Both are located in thevicinity of the two clusters in Crux area, the CIZA clusters(Clusters in the ZOA, Ebeling et al. 2002) CIZA 1324.7–5736at (l, b, v) = (307◦, 5◦, 5700 km s−1) and less rich Cen-Crux clus-ters (l, b, v) = (306◦, 5.◦5, 6200 km s−1), but not close enough toexpect any H i stripping. It is therefore more likely that the mor-phological types (S3 and S4, respectively) are wrong, and thatthese galaxies are of later type. This is supported for WKK 1294,which is bright in the B-band but barely visible on the 2MASSJ-band image. A later type would reduce the H i deficiencyvalue.
7. Large-scale structure in the Crux and GA regions
In this section, we will discuss the new H i detections in thecontext of the known large-scale structures (LSS) in and acrossthe ZOA. The new data is presented together with previouslyknown redshifts in and adjacent to the survey area (extractedfrom LEDA) in a series of sky projections and redshift cones(Figs. 10 and 11). Care should be taken in the interpretation ofthese plots as they are based on an “uncontrolled” redshift sam-ple of galaxies.
7.1. Sky projections
Figure 10 displays the galaxy distribution in Galactic coordi-nates in and around the survey region sliced in redshift intervalsof widthΔv = 2000 km s−1 out to 8000 km s−1 (the first slice runsfrom 300−2000 km s−1). Higher velocity slices (8000−12 000)are not shown, as the detections for v > 8000 km s−1 (see Fig. 4)are too scarce to add useful insight to the LSS at those redshifts.
What is immediately conspicuous in all four panels is thatthe H i detections constitute a large fraction of the galaxies withredshifts within the band limited by AB < 3.m0 and b < 10◦ (apartfrom the H i-deficient galaxies in the Norma cluster). This em-phasises that H i-observations, even when dependent on optical(or NIR) pre-identification, are tremendously powerful in map-ping LSS of highly obscured galaxies in and across the ZOA.Note that optical redshifts for these survey regions have been ob-tained earlier with the SAAO 1.9 m telescope (Fairall et al. 1998;Woudt et al. 1999), as well as with multi-object spectroscopy us-ing the 3.6 m telescope of ESO in Chile (Woudt et al. 2004).
The first slice is quite sparsely populated. The SupergalacticPlane (SGP; de Vaucouleurs 1953) is the most prominent fea-ture, visible here from about (�, b) = (335◦, −30◦) to (315◦,+30◦), crossing the Galactic Plane (GP) at � = 325◦. Most ofthe detections in this panel lie along the SGP.
In the second panel (2000–4000) the Centaurus Wall (CenW)is the dominant feature (Fairall 1998; Fairall et al. 1998). It en-ters the panel at about (345◦, −30◦) and extends across the ZOAto the Centaurus clusters (302◦, +22◦); it is less inclined than theSGP. Apart from a few detections below the GP in Crux, whichdo not seem to highlight any particular structure, most of theH i-detected galaxies in this panel follow CenW. However, thedetections above the GP spread out over a much wider area thanwould be expected from the quite narrow CenW, i.e., it seems toveer off toward the right (∼310◦, +5◦), away from CenW. Thesegalaxies probably are the low velocity members of the two Cen-Crux clusters discussed below which form part of the NormaGreat Wall.
Despite the many H i non-detections at the core of the cluster,the Norma cluster and the Norma Great Wall – dubbed so for thefirst time by Woudt et al. in 1999 – are the prominent structuresin the third panel. There are still a few galaxies visible that formpart of CenW (blue dots above the GP around the Crux/GA bor-der). But the majority of the detections (mostly red dots) fol-low the Norma Wall (Woudt et al. 1999). The Norma Wall canbe traced from the Pavo II cluster (∼332◦, −23◦) to the Normacluster (∼325◦, −7◦), see also Fig. 11. It crosses the GalacticPlane at ∼320◦, and continues with a much shallower slopewith respect to the Galactic Plane towards two neighbouringgalaxy clusters at slightly higher redshift, the Cen-Crux cluster at(�, b, v) ∼ (305.◦4, 5◦, 6200 km s−1) (Woudt et al. 1999; Woudt &Kraan-Korteweg 2001) and the X-ray cluster CIZA J1324.7–736at (�, b, v) ∼ (307.◦4, 5◦, 5700 km s−1) (Ebeling et al. 2002). Fromthere, the Wall connects with the Vela cluster (Abell S0639;
A. C. Schröder et al.: Parkes H I observations of galaxies behind the southern Milky Way. II. 1067
Fig. 10. Sky projections in Galactic coordinates in and around theCrux/GA survey region in redshift intervals of Δv = 2000 km s−1
for 300 < v < 8000 km s−1. In each panel, the “nearer” galaxies(Δv = 1000 km s−1) have blue symbols, and the more distant red sym-bols. The squares around the dots identify the new H i detections. Thesurvey area and extinction contour of AB = 3.m0 are outlined.
(�, b, v) = (280.◦5, −10.◦9, 6326 km s−1); Stein 1996). The ex-tent and shape of this wall was suspected in earlier papers(e.g., Kraan-Korteweg et al. 1994) and strongly supported in
more recent work (Woudt et al. 2004; Kraan-Korteweg 2005;Ebeling et al. 2005; Radburn-Smith et al. 2006). A sketch of thisWall, as well as the Centaurus filament, is given with Fig. 4 inRadburn-Smith et al. (2006).
In the final panel, most of the H i detections are found atthe position of the Norma cluster and the two Crux clusters.They most certainly are high velocity dispersion outliers of themassive clusters (finger-of-God effect) prominent in the previ-ous panel, rather than an indication of galaxy agglomerations atthis higher velocity range.
In conclusion, the new H i detections mostly help to delin-eate filaments and walls deeper into the ZOA. They provide sup-porting evidence that the Norma Wall crosses the ZOA, but thenturns away from CenW towards Vela. A much smaller numberof galaxies seem to form part of the general field. The slices alsoindicate that the H i observations of galaxies allow the mappingof LSS to quite high dust column-densities, higher than can beachieved with optical spectroscopy.
7.2. Pie diagrams
The above findings are confirmed with Fig. 11, which showsthe new detections in a composite of pie diagrams that covera wider area than the previous figure to reveal the overall LSSin this part of the sky. The two top panels show redshift slicesout to 12 000 km s−1, the maximum redshift range of our HI ob-servations. They are 30◦ wide in longitude, with the left onecentred on the GA survey region (340◦ > � > 310◦) and theright one centred on the Crux survey region (310◦ > � > 280◦).Note that there is a longitude overlap of 10◦ to facilitate the vi-sualisation of the structures running from one wedge diagramto the next. The pie diagram for these two longitude strips runfrom −45◦ across the ZOA to +45◦. The bottom panel displaysa pie diagram of the ZOA (|b| ≤ 10◦) for the longitude range360◦−270◦ as in the sky projection plot in the middle panel. Themiddle panel displays the projected LSS distribution of galaxiesout to 12 000 km s−1, with blue dots marking the distance rangeof Norma and the Norma Wall (3000−6500 km s−1), magentathe nearer galaxies (300−3000 km s−1), and cyan the distantgalaxies (6500−12 000 km s−1). This panel is meant for orienta-tion and interpretation of the pie diagrams. The plot is collapsedin latitude.
The pie diagrams confirm that H i-observations of opticallyselected galaxies are quite successful in reducing the ZOA downto |b| = 5◦, at least out to redshifts of about 6000 km s−1 (seealso Fig. 4). For higher velocities the detection efficiency dropssubstantially and the ZOA remains increasingly empty. Such adrop in the detection rate at similar velocities can also seen in thesystematic, blind deep Parkes H i ZOA survey (HIZOA; |b| ≤ 5◦;see, e.g., Fig. 13 in Kraan-Korteweg 2005). This is not surprisinggiven that the rms and velocity range of both surveys are similar.In that sense, the pointed Parkes H i observations presented here,which are quite successful in the range 5◦ <∼ |b| <∼ 10◦, are in factcomplementary to the deep Parkes HIZOA survey of the inneroptically opaque ZOA (Henning et al., in prep.; for preliminaryresults see Henning et al. 2005; Kraan-Korteweg et al. 2005).
The most prominent feature in the GA cone diagram (topleft panel) is the Norma cluster with its finger-of-God rangingbetween 2500−6500 km s−1 evident at (b = −7◦). The clusterstands out even more prominently in the bottom panel which dis-plays the ZOA slice. The H i detections (red dots) mostly hoveraround Norma. The cluster itself seems embedded in a wall-like structure centred at a mean velocity of 4500−5000 km s−1
which can be traced from about b ∼ −30◦ to the Norma cluster
1068 A. C. Schröder et al.: Parkes H I observations of galaxies behind the southern Milky Way. II.
Fig. 11. Large scale structures in and around the Crux/GA region. The top two redshift cones are centred on the GA and Crux regions, respectively,and cover the latitude range b ≤ ±45◦ out to v = 12 000 km s−1. The bottom panel displays a redshift cone of the ZOA (|b| ≤ 10◦). Red and greendots represent the Parkes H i detections and previously determined redshifts from LEDA, respectively. The middle panel shows the sky distributionof galaxies out to the same redshift. It is meant as a guide in the interpretation of the redshift cones.
(b = −7◦) where we lose it in the ZOA. This is also evident in themiddle panel where we see part of the wall between the Pavo IIcluster (Abell S0805 at 332◦, −24◦, 4200 km s−1) and Norma. Aweak continuation of the wall is visible on the other side of theGP, together with an overdensity at slightly lower velocities. Thelatter is probably related to CenW (see also panel 2 in Fig. 10).
We find a clearer continuation of these structures in the Cruxcone (top right panel). Most of the detections lie above the GP.Hardly any detections or possible extension of the Norma clus-ter/wall exists below the GP. The galaxies either form part ofCenW which connects with the Centaurus clusters visible inthis cone at lower velocities at b � 20−30◦, or with the higher
A. C. Schröder et al.: Parkes H I observations of galaxies behind the southern Milky Way. II. 1069
velocity Crux clusters (Cen-Crux and CIZA J1324.7–736). Thelatter two also stand out in the ZOA-longitude slice displayedin the bottom panel. The link with the galaxy cluster in Vela(Abell S0639) is not visible here as the cluster with (�, b, v) =(280.◦5, −10.◦9, 6326 km s−1) (Stein 1996) lies just beyond theCrux slice (and just beyond the latitude limit of the ZOA slice).
The bottom panel shows the galaxy distribution in the tradi-tional “optical” ZOA, i.e., for |b| <∼ 10◦ for a major fraction ofthe southern ZOA, where near-infrared surveys are also highlyincomplete (e.g., Fig. 9 in Kraan-Korteweg 2005). It is satisfyingto see that real LSS including voids are now emerging within theZOA. The H i data follow again the previously identified struc-tures, which on average lie at slightly higher latitudes. Distinctfeatures are the Norma cluster with its enormous velocity dis-persion, as well as the Cen-Crux and CIZA cluster, clearly iden-tifiable as clusters. As a clump (rather than a finger of God) wefind an overdensity in red and green dots at about 4000 km s−1
that most certainly is a signature of the crossing of the CentaurusWall across the ZOA.
The wall-like structure of Norma is not obvious in this ZOApie diagram, as the larger structures – from Pavo to Normaand from the Crux clusters to Vela – lie just beyond the ZOA,whereas the inner ZOA (|b| < 5◦) remains unprobed by thisproject due to the optical pre-selection of spiral galaxy candi-dates. However, the pie diagram will soon be filled by the deepParkes HIZOA survey, where indeed evidence is found for thecontinuation of the Centaurus Wall and the Norma (or GA) Wallsuggested here (see Kraan-Korteweg 2005; Henning et al. 2005,for preliminary results).
8. Summary
This paper presents pointed 21 cm spectral line (H i) observa-tions obtained with the 64 m Parkes radio telescope of partiallyto heavily-obscured spiral galaxies uncovered in the deep opti-cal search for galaxies in the Crux and GA regions of the ZOA(Woudt & Kraan-Korteweg 2001). Out of a total of 314 observedgalaxies we have detected 162. Due to the high density of galax-ies in some areas (in particular near and in the Norma cluster),a number of pointings contain more than one detection. On theother hand, some pointings of a non-detection show a chance de-tection of a different galaxy (with a distance to the beam centreof up to 20′).
The average rms for the detections is 4.2 mJy; 85% of all de-tections have an rms within the range 2−6 mJy. Non-detectionshave a slightly higher rms of 4.7 mJy. The mean peak flux den-sity is 46 mJy (with a median of 39 mJy), which is significantlylower than the average detection limit of the HIPASS detec-tions (∼70 mJy) but similar to HIZOA (Henning et al. 2005;Kraan-Korteweg et al. 2005). The H i parameters compare wellwith those found with HIPASS, and the velocities compare wellwith optical velocities found in the literature.
The detection rate in the survey area is 52%, slightly higherthan in the Hydra/Antlia survey region (45%) obtained in thesame way (Paper I). The exception is the core of the Normacluster: within 1 RA, the detection rate drops to 41% as expectedin case of H i deficiency. To explore this further, we have de-rived H i deficiency parameters for all galaxies in and aroundthe Norma cluster. Although only a few galaxies have actuallybeen detected within 1 RA, the lower limits of non-detectionsconfirm that the galaxies in the Norma cluster are on aver-age strongly H i deficient within 0.4 RA. Including three fieldsobserved with ATCA in the Norma cluster at an earlier stage
(Vollmer et al. 2001) and calculating the upper limits for non-detected spiral galaxies strengthens this conclusion. It shows fur-thermore that non-detected spiral galaxies between 0.4 RA and1.0 RA also exhibit H i deficiencies. The observed trend is simi-lar to that seen in the Coma cluster within 0.4 RA (Bravo-Alfaroet al. 2000) and to other massive, X-ray bright galaxy clusterswithin 1.0 RA (Giovanelli & Haynes 1985).
The H i detections delineate large-scale structures, such asfilaments, walls and voids, deeper into the ZOA than any ofthe other previous optical redshift follow-ups of the opticallyidentified galaxies. Most low-velocity detections lie along theSGP, while intermediate-velocity galaxies follow the CenW. Thehigher-velocity galaxies (5000−6500 km s−1) support evidencethat the Norma Wall crosses the ZOA, but then turns from theCenW towards Vela. Only a small number of the detected galax-ies seem to form part of the general field.
We have shown that H i observations, even when dependenton optical (or NIR) pre-identification, are quite successful in re-ducing the (redshift) ZOA down to |b| >∼ 5◦ and in mapping LSSof highly obscured galaxies in and across the ZOA, at least outto redshifts of about 6000 km s−1. For higher velocities the de-tection efficiency drops substantially and the ZOA remains in-creasingly empty. Our observations are complementary to thedeep Parkes HIZOA survey of the inner optically opaque ZOAat |b| ≤ 5◦ (Kraan-Korteweg et al. 2005; Henning et al. 2005;Henning et al., in prep).
With the future Square Kilometer Array (SKA) pathfinders,the Australian ASKAP and the South African MeerKAT, the sit-uation will be greatly improved: we will be able to close theredshift ZOA to even lower latitudes and to map the LSSs tohigher redshifts and lower H i masses. For example, MeerKATwill not only be able to fully map the GA but also the Shapleycluster concentration and thus possibly solve the GA/Shapleycontroversy on what is the dominant contributor to the dipolemotion of the universe (Kraan-Korteweg et al. 2009, and refer-ences therein).
Acknowledgements. We first of all would like to thank P. A. Woudt for manyvaluable discussions and the referee for many valuable suggestions. We havemade use of the Lyon-Meudon Extragalactic Database (LEDA), supplied by theLEDA team at the Centre de Recherche Astronomique de Lyon, Observatoirede Lyon, and of the NASA/IPAC Extragalactic Database (NED), which is oper-ated by the Jet Propulsion Laboratory, Caltech, under contract with the NationalAeronautics and Space Administration. Furthermore, this research has made useof the Digitized Sky Surveys (produced at the Space Telescope Science Instituteunder US Government grant NAG W-2166) and of the HIPASS database pro-vided by the ATNF under the auspices of the Multibeam Survey Working Group.RKK thanks the South African National Research Foundation for support.
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Appendix A: Notes to individual galaxies
In the following we discuss cases where the cross-identificationis not straightforward or where the signal is a combination ofthe signals from two or more galaxies. In many cases we quotedata from Tables 1−4 (including the optical galaxy catalogue byWoudt & Kraan-Korteweg 2001), notably morphological types,sizes, and optical velocities. We have also made use of DSS4
images and of images from the DENIS (Epchtein et al. 1997)and 2MASS (Skrutskie et al. 2006) surveys.
WKK 0491/WKK 0512: there is a second detection in thebeam of WKK 0491. The small lopsided signal is probably dueto WKK 0512 (d = 12.′4, 28′′ × 8′′, SL) which is the largest late-type spiral in the vicinity. WKK 0493 at d = 10.′2 (28′′ × 6′′, L)is an early type galaxy and less likely to be the candidate.
WKK 0969/WKK 1117: there is a detection in the OFF ob-servation of WKK 1117, close to but separated from its signal.The nearest candidate is WKK 0969 at d = 8.′5 (16′′ × 12′′, un-known type, AB = 3.m4), which is also the only galaxy found by2MASS in this area.
WKK 1696 has also been detected in the beam ofWKK 1694 (not detected) at d = 8.′7 with v = 6680 km s−1,ΔV50 = 300 km s−1, ΔV20 = 318 km s−1, I = 2.47 Jy km s−1,rms = 2.4 mJy.
WKK 2163: the ID is ambiguous. The observed velocity isv = 3533 km s−1, and WKK 2160 at d = 3.′3 (27′′ × 24′′, S) hasan optical velocity of 3512 ± 58 km s−1 (FW98). It is possiblethat we have observed WKK 2160, but if the two galaxies aregenuine companions the signal probably comes from WKK 2163(74′′ × 56′′, S6) which is the larger of the two. HIPASS canbarely resolve the positions, but seems to favour WKK 2163.
WKK 2245: it is possible that WKK 2240 (ESO173-G015,d = 2.′6, S, 85′′ × 12′′) with an optical velocity of v = 3006 ±36 km s−1 (SH92) contributes to the signal.
WKK 2372/WKK 2402: the distance between the galaxiesis d = 16.′1, both have been detected at similar velocities, but theprofiles are not confused.
4 The STScI Digitized Sky Survey.
A. C. Schröder et al.: Parkes H I observations of galaxies behind the southern Milky Way. II. 1071
WKK 2377/WKK 2388/WKK 2406: this is a group of fourgalaxies: WKK 2377 (S7:, 70′′ × 23′′), WKK 2375 (S5, 62′′ ×56′′, 4290 ± 37 km s−1 FH95), WKK 2388 (S5, 36′′ × 16′′,3976 ± 40 km s−1, FH95), and WKK 2406 (SL, 55′′ × 38′′).WKK 2388 lies between WKK 2377 and WKK 2406 and thepointing of WKK 2388 shows a confusion of the two lat-ter profiles at v � 4100−4400 km s−1. The signal at v �3800−4050 km s−1 belongs to WKK 2388 proper and the linewidth is assumed to be unaffected. However, due to difficultieswith fitting a good baseline the flux density is somewhat uncer-tain. Using HIPASS we have found that WKK 2375 does notadd (significantly) to the combined signal. The observations ofWKK 2377 and WKK 2406 at their respective pointings are notconfused at the noise level.
WKK 2390/WKK 2392: the close galaxy pair (at d = 1.′2and d = 3.′2, respectively, from the pointing position) is unre-solved, and the parameters given in Table 1 refer to the full pro-file. The quoted velocity by VY96 refers to the IRAS detectionwhich is also unresolved.
WKK 2503: also observed with HIZSS, the spectrum showsa profile reminiscent of the blended signal of two objects.WKK 2503 has a bright bulge and large faint halo with a brightstar superimposed close to the bulge. No other galaxy in thisarea is visible either in the optical or in the NIR. At an extinc-tion of AB = 3.m7 a late-type/LSB galaxy, WKK 2503B, could beinvisible even in the NIR. Table 1 gives the parameters of thefull profile. The two velocities found in the literature refer toH i observations and are equally unresolved.
WKK 2576/WKK 2595/WKK 2597: the observed profile isa combination of the signals from three galaxies: WKK 2595(S6, 102′′ × 40′′) and WKK 2597 (S5, 59′′ × 47′′, 3973 ±46 km s−1, SH92) are a close galaxy pair (d = 1.′2); ac-cording to HIPASS, WKK 2576 at d = 8.′4 (S5, 86′′ × 75′′,3948 ± 70 km s−1, DN97) has a strong narrow H i profile.Table 1 gives the measurement of the full profile for the un-resolved pair WKK 2595/WKK 2597, while, through compari-son with HIPASS, the width and velocity of the peak at v �3800−3950 km s−1 is given for WKK 2576. By removing thispeak we have re-measured the width and velocity of the under-lying low-intensity profile for the close galaxy pair and foundv = 3889 km s−1, ΔV50 = 266 km s−1, ΔV20 = 313 km s−1.
WKK 2640/WKK 2644: there are two detections in thebeam of WKK 2640: the narrow spike at v = 3705 km s−1
is WKK 2640 (I, 51′′ × 42′′), while the detection at v =9404 km s−1 is WKK 2644 (SM, 26′′ × 9′′) with an optical ve-locity of 9406 ± 100 km s−1 (WK04) at d = 4.′3. Due to the verylopsided profile of WKK 2644 the high-velocity end is uncertain.
WKK 2844/WKK 2863: two galaxies contribute to the de-tected signal. HIPASS shows that WKK 2863 (S5, 98′′ × 83′′,3778 ± 30 km s−1, SE95) at d = 8.′7 has a strong profile withv � 3600−3850 km s−1. At the position of WKK 2844 the ob-served profile is smaller but extends to v � 3950 km s−1; it istherefore assumed that WKK 2844 has been detected but it re-mains unresolved, with a velocity slightly larger than the one forWKK 2863. Table 1 gives the parameters of the full profile forWKK 2863, which is considered to be the main contributor tothe signal.
WKK 2924/WKK 2938: there are two detections in thebeam of WKK 2924: WKK 2938 (L, 34′′ × 22′′) at d = 7.′3has an optical velocity of 3024 ± 157 km s−1 (FW98) whichagrees with the narrow peak at v = 2864 km s−1. WKK 2924(S8, 58′′ × 22′′) is a more likely candidate for the signal atv = 3410 km s−1. HIPASS also shows the latter detection at the
position of WKK 2924, while nothing can be seen at the positionof WKK 2938.
WKK 2993 has a close companion (Woudt &Kraan-Korteweg 2001) which might contribute to the signal.
WKK 3002/WKK 3006: the two detections in the beam ofWKK 3002 can not unambiguously identified: WKK 3002 (SL?,56′′ × 20′′) is more likely to be the stronger signal at v =3436 km s−1 (cf. HIPASS), while the galaxy at v = 2820 km s−1
is more likely WKK 3006 (13′′ × 8′′, no type).WKK 3023: with AB = 22m the galaxy is unlikely to be real,
and nothing is visible on DENIS or 2MASS images.WKK 4016/WKK 4022: the profile is due to the blending
of two signals. HIPASS shows that the high narrow peak at v �4680 km s−1 is WKK 4016 (SL, 67′′ × 48′′) at d = 12.′1, whilethe broader profile is probably due to WKK 4022 proper (S5,91′′ × 34′′). Table 1 gives the parameters for the full profile forWKK 4022 and the measurements of the narrow peak alone forWKK 4016; all parameters are uncertain.
WKK 5240: the detection in the beam of WKK 5267 (not de-tected) at d = 11.′7 is WKK 5240 (S, 157′′ × 13′′; cf. HIPASS).The profile shape is very noisy and the parameters are uncertain.
WKK 5285: this galaxy has been detected in the beams ofthree other galaxies: in the OFF observations of WKK 5534(d = 6.′5) and of WKK 5556 (d = 2.′7), as well as in thebeam of WKK 5297 (not detected) at d = 6.′1. The detec-tion with the smallest distance to the beam centre is listed inTable 1 and shown in Fig. 1, while the detection in the OFFobservation of WKK 5524 is least affected by an RFI at v =5900 km s−1 next to the signal. The other measurements are:v = 5631 km s−1, ΔV50 = 353 km s−1, ΔV20 = 383 km s−1,I = 15.65 Jy km s−1, rms = 5.3 mJy (in the beam of WKK 5297);and v = 5635 km s−1, ΔV50 = 357 km s−1, ΔV20 = 396 km s−1,I = 15.17 Jy km s−1, rms = 3.3 mJy (in the OFF observation ofWKK 5534).
WKK 5366: the identification is uncertain: the optical veloc-ity is 4822± 82 km s−1 (WK04), but both HIPASS and JS00 con-firm the H i signal to be strongest at the position of WKK 5366.Since the extinction here is AB = 3.m8, an obscured galaxy closeby cannot be excluded.
WKK 5443OFF: the detection found in the OFF observationof WKK 5443 was subsequently searched for the “best” position.It has also been detected by HIZSS and JS00. No galaxy couldbe found in the optical or NIR (DENIS, 2MASS).
WKK 5562/WKK 5616/WKK 5642: in the observations ofboth WKK 5562 and WKK 5642 a narrow single peak appears atv � 4160 km s−1. Using HIPASS we determined that this signalmost likely comes from WKK 5616, a late-type galaxy (19′′ ×5′′) at d = 5.′3 from WKK 5642 (listed in Table 1) and d = 12.′2from WKK 5562 with the following parameter: v = 4157 km s−1,ΔV50 = 42 km s−1, ΔV20 = 75 km s−1, I = 1.95 Jy km s−1,rms = 4.7 mJy.
WKK 5595 is included in the catalogue since it is very closeto the observed but undetected WKK 5597 (28′′ × 11′′, L?)at d = 0.′7 and is of comparable size (30′′ × 19′′, type un-known), that is, the rms can be considered an upper limit forboth galaxies.
WKK 5642/WKK 5659: there are three detections in thebeam of WKK 5642 (48′′ × 17′′, SM): the spike at v =4167 km s−1 is WKK 5616 and has been discussed above. Thesignal at v = 6446 km s−1 is assumed to belong to WKK 5642since it also has two optical velocities of 6045 ± 42 km s−1
(SH92) and v = 6118 ± 100 km s−1 (WK04), though this isonly in moderate agreement. WKK 5670 (24′′ × 8′′, SE:) atd = 6.′6 with an optical velocity of v = 6329 ± 44 km s−1
1072 A. C. Schröder et al.: Parkes H I observations of galaxies behind the southern Milky Way. II.
(WK04) can be excluded as a candidate since it is only d = 5.′6from WKK 5694, which has also been observed and shows nosignal at v � 6400 km s−1. A third signal has been found atv = 4418 km s−1 which is likely to be WKK 5659 (44′′ × 15′′,S6) at d = 3.′4.
IC 4584/IC 4585: this is a detection in the beam ofWKK 5581 (not detected). IC 4584 and IC 4585 are two largespiral galaxies at d � 9′ from the pointing. HIPASS confirmstheir identity but cannot resolve the pair, though clearly bothgalaxies contribute to the signal. The measurement of the fullprofile is given in Table 1.
WKK 5729: the three observations of WKK 5733 (vopt =
6215± 92 km s−1, WK99), WKK 5694 (vopt = 3412± 36 km s−1,FH95), and WKK 5709 show a very similar profile both in linewidth and peak flux at v = 5729 km s−1, v = 5730 km s−1, andv = 5723 km s−1, respectively. The left horn appears to comefrom WKK 5768 (also detected in the beam of WKK 5780),which lies at a distance of d = 13.′5, d = 17.′9, and d = 11.′7,respectively, from the three pointings; the peak flux of this hornvaries according to the distance. Due to the similar peak flux andhigh velocity end of the rest of the profile we conclude that thedetected galaxy must lie at a similar distance from these threepointings. WKK 5729 (48′′ × 16′′, SL) lies at d = 6.′9, d = 9.′1,and d = 5.′9 from WKK 5733, WKK 5694, and WKK 5709, re-spectively. It is a late-type spiral and therefore not visible with2MASS and DENIS. The signal is too weak to be detectable withHIPASS.
WKK 5768 is detected in the beam of WKK 5780 (not de-tected) at d = 9.′5. The low-velocity horn is also visible in theobservations of WKK 5709 (d = 11.′7; see plot of WKK 5729),WKK 5733 (d = 13.′5) and WKK 5694 (d = 17.′9).
WKK 5993/WKK 5999: the detection in the observation ofWKK 5993 is the blending of two signals. The low-velocitydouble-horn comes from WKK 5999 (also observed, see Fig. 1),while the high-velocity part is due to WKK 5993. The param-eters for WKK 5993 in Table 1 have been measured by cuttingoff the profile of WKK 5999 at v � 3350 km s−1. All the pa-rameters are uncertain since the low-velocity end of WKK 5993is undetermined. For the WKK 5999 profile we have measuredv = 3261 km s−1, ΔV50 = 180 km s−1, ΔV20 = 226 km s−1,I = 8.83 Jy km s−1, rms = 2.3 mJy.
WKK 6187 is included in the catalogue since it is very closeto the observed but undetected WKK 6189 (13′′ × 8′′, E) at d =0.′9 and is slightly larger (22′′ × 22′′, type unknown), that is, therms can be considered an upper limit for both galaxies.
WKK 6535/WKK 6570: there are two detections in thebeam of WKK 6570. WKK 6535 (39′′ × 9′′, S5) lies at d = 6.′5and is likely to be the detection at v � 4150 km s−1. SinceWKK 6570 (60′′ × 27′′, S3) is the larger and brighter of the twowe have assumed it to be the closer galaxy at v = 2938 km s−1,but the identities remain ambiguous.
WKK 6594: the H i galaxy is probably identical with theIRAS galaxy at d = 2.′2 with v = 642 ± 35 km s−1 (SH92).
WKK 6689/WKK 6732: the two galaxies with similar ve-locities lie 9.′6 apart. The observation of WKK 6732 shows nosignificant confusion with the signal of WKK 6689 (though theflux density may be uncertain), while the profile for WKK 6689is more uncertain.
WKK 7287/WKK 7289: the small signal at v = 5740 km s−1
detected in the beam of WKK 7289 is probably WKK 7287 atd = 3.′3 (30′′ × 20′′, I).
WKK 7460/WKK 7463 is an interacting system with a sep-aration of 1.′4: WKK 7460 (198′′ × 105′′, SL) is the larger com-ponent with an optical velocity of 775± 36 km s−1 (SH92), while
the profile gives v = 842 km s−1. Table 1 gives the full param-eters for WKK 7460 only, since the contribution by WKK 7463(82′′ × 67′′, S) is uncertain. However, considering the types andsizes of the two galaxies as well as the H i velocity as comparedto the optical of WKK 7460, we can assume that WKK 7463contributes to the profile.
WKK 7465/WKK 7198: WKK 7198 has been detected inthe OFF observation of WKK 7465 at d = 7.′2, and the profilesoverlap. The observation of WKK 7198 (see Fig. 1) shows thatthe profile extends from v � 3270 km s−1 to ∼3540 km s−1. Theprofile of WKK 7465 is therefore truncated and no line widthsand flux could be derived. The systemic velocity is likely to behigher than the one given.
WKK 7652/WKK 7689: WKK7652 has been detected inthe beam of WKK 7689 (not detected) at d = 11.′2. Optical ve-locities for this galaxy are v = 1350 ± 31 km s−1 (RC3) andv = 1478 ± 38 km s−1 (WK04), while other H i measurementsfind v = 1482 ± 6 km s−1 (RC3). While we find v = 1519 km s−1,HK01 has detected WKK 7689 at v = 1559 ± 3 km s−1 in H iwith the radio telescope at Effelsberg, which has a smaller beamsize (9′ as compared to 15′ for Parkes). We can therefore notexclude that part of the signal in our observation comes fromWKK 7689.
WKK 7776 has also been detected in the beam ofWKK 7794 at d = 10.′7 with v = 2790 km s−1,ΔV50 = 45 km s−1,ΔV20 = 55 km s−1, I = 4.11 Jy km s−1, rms = 5.6 mJy.
Appendix B: Galaxies in the Vela region
A number of galaxies outside of the Crux and GA region werealso observed within this observing programme, i.e., galaxies inthe Vela region (245◦ >∼ � >∼ 275◦). They were taken from theZOA deep optical galaxy catalogue (Salem & Kraan-Korteweg,in prep.; see Kraan-Korteweg & Lahav 2000, for preliminary re-sults) that covers the region between Puppis (Saito et al. 1991)and the Hydra/Antlia region (Kraan-Korteweg 2000); see Figs. 2and 3 in Kraan-Korteweg & Lahav 2000, for an outline of thesurveyed area and the distribution of the uncovered galaxies.
The data of the detected (N = 14) and non-detected galax-ies (N = 15) are presented in Tables B.2 and B.3, which areequivalent to Tables 1 and 4 (see Sects. 3 and 4 for the columndescriptions). The profiles of the detected galaxies are shownin Fig. B.1, and Table B.1 gives the independent velocity mea-surements found in the literature for the detected galaxies (seethe description of Table 2 in Sect. 3). The reference for KF95 isKraan-Korteweg et al. (1995).
Table B.1. Comparison of velocities for Vela galaxies.
Ident. Vhel Vother Origin Referencekm s−1 km s−1
(1) (2) (3) (4) (5)
SKK259- 15L 2730 2723 ± 7 H i HIPASSSKK261- 17L 2979 2974 ± 10 H i HIPASSSKK262- 89L 3513 3451 ± 50 opt FW98SKK262- 36L 4650 4651 ± 9 H i HIPASSRKK1949 4030 4002 ± 100 opt KF95
4037 ± 36 opt SH92SKK263-164L 4118 4116 ± 1 H i DN96SKK263-133L 1106 969 ± 54 opt FH95
1106 ± 6 H i HIPASSSKK263- 12L 4540 4600 ± 40 opt RC3
4545 ± 6 H i HIPASS
A. C. Schröder et al.: Parkes H I observations of galaxies behind the southern Milky Way. II. 1073
Tabl
eB
.2.Hi-
dete
ctio
nsin
the
Vel
are
gion
.
Iden
t.O
ther
IRR
AD
ecga
l�ga
lbTy
peD×d
BJ
E(B−V
)V
helΔ
V50
ΔV
20I
rms
hann
Ndi
stI c
exci
sed
RF
I(h
ms)
(deg
′′′ )
(deg
)(d
eg)
(′′)
(m)
(m)
kms−
1km
s−1
kms−
1Jy
kms−
1m
Jy(′
)Jy
kms−
1km
s−1
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
(13)
(14)
(15)
(16)
(17)
(18)
(19)
(20)
(21)
SK
K25
8-19
6LE
SO
258-
G00
207
5813
.9−4
701
0926
1.52−9
.16
S60×
4014
.90.
3261
7417
722
07.
253.
558
00S
KK
209-
184L
ES
O20
9-G
016
MI
0805
29.0−4
850
5626
3.74−9
.06
SB
R3
54×
5414
.60.
2981
9619
824
02.
983.
0S
KK
209-
123L
ES
O20
9-G
017
M08
0833
.2−4
903
5026
4.20−8
.74
S54×
1216
.20.
2681
3037
839
54.
713.
3S
KK
209-
5208
1134
.2−4
708
4126
2.83−7
.29
I34×
1316
.90.
6110
91:
79:
99:
3.49
:10
.2*
1000
SK
K25
9-15
LE
SO
259-
G00
108
1731
.4−4
537
1126
2.11−5
.60
SL
?34×
1916
.10.
8127
3027
829
915
.44
5.7
SK
K21
0-1
0846
54.4−4
747
5326
6.85−2
.82
?47×
1316
.81.
0089
6921
028
54.
202.
8S
KK
261-
17L
ES
O26
1-G
006
M09
2334
.0−4
245
3926
7.42
5.34
S5
40×
4015
.50.
6529
7915
620
77.
793.
5S
KK
262-
556L
ES
O26
2-G
004
0946
22.5−4
638
3827
3.06
5.21
S10
8×11
15.8
0.46
2709
288
319
13.7
34.
2S
KK
262-
89L
ES
O26
2-G
015
I10
0239
.2−4
529
5827
4.56
7.87
S1
60×
2415
.10.
1935
1326
428
27.
18:
3.5
4150
SK
K26
2-36
LE
SO
262-
G01
6M
1003
11.6−4
249
0827
2.99
10.0
6S
371×
4414
.50.
1646
5014
416
95.
923.
0
RK
K19
49E
SO
263-
G00
4M
I10
0646
.9−4
741
4827
6.45
6.53
SB
154×
4714
.70.
2040
3030
231
65.
26:
3.3
3350/4
150
SK
K26
3-16
4LE
SO
263-
G01
6M
1012
32.4−4
514
1327
5.82
9.11
S3
108×
8113
.40.
1941
1819
722
116
.08
5.3
SK
K26
3-13
3LE
SO
263-
G02
1I
1014
42.0−4
450
5927
5.91
9.64
74×
6014
.10.
2111
0683
106
5.92
7.8
SK
K26
3-12
LE
SO
263-
G03
5I
1026
14.4−4
544
1327
8.12
10.0
2S
112
1×47
13.6
0.18
4540
450:
491:
27.6
1:7.
143
50
Not
es:S
KK
209-
52:t
heR
FI
isne
xtto
the
profi
lean
dpo
ssib
lyaff
ects
the
line
wid
th.
Tabl
eB
.3.Hi
non-
dete
ctio
nsin
the
Vel
are
gion
.
Iden
t.O
ther
IRR
AD
ecga
l�ga
lbTy
peD×d
BJ
E(B−V
)V
obs
rang
erm
sV
pert
rang
eN
dist
Vot
her
Ref
orig
in(h
ms)
(deg
′′′ )
(deg
)(d
eg)
(′′)
(m)
(m)
kms−
1m
Jykm
s−1
(′)
kms−
1
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
(13)
(14)
(15)
(16)
(17)
(18)
(19)
SK
K25
8-13
7M
0742
49.8−4
412
2725
7.70−1
0.14
S?47×
2715
.90.
3130
0−1
0250
4.0
SK
K25
8-89
M07
5507
.4−4
500
2625
9.49
−8.6
2SM
54×
817
.00.
2330
0−1
0250
3.2
700−
1100
*S
KK
209-
209
LE
DA
3098
730
M08
0453
.1−4
908
5026
3.95
−9.2
9S
54×
816
.80.
2950
0−1
0250
3.5
SK
K25
8-14
M08
0610
.6−4
352
2825
9.53
−6.3
4SM
40×
2415
.80.
4340
0−1
0250
4.5
SK
K31
2-4
M08
0918
.5−3
838
4625
5.42
−3.0
4?
20×
2016
.62.
4540
0−1
0350
3.8
900−
1100
SK
K25
9-18
M08
1420
.1−4
638
0726
2.65
−6.6
2?S
L67×
716
.90.
6950
0−1
0250
7.3
SK
K26
2-42
5LE
SO
262-
G00
6M
0948
40.3−4
529
4627
2.62
6.35
S74×
517
.00.
1930
0−1
0350
4.4
SK
K26
2-36
1E
SO
262-
G00
909
5131
.9−4
401
1427
2.07
7.81
S67×
716
.60.
2540
0−1
0250
3.3
300−
400
850−
1050
SK
K26
2-30
3LE
SO
262-
G01
0M
0953
47.3−4
558
0227
3.62
6.55
S54×
1316
.00.
2230
0−1
0250
4.1
820−
1020
SK
K26
2-12
7E
SO
316-
G01
5M
1000
53.3−4
241
0327
2.57
9.91
S74×
1116
.00.
2330
0−1
0250
4.6
800−
1070
*97
96±
10M
F96
opt
SK
K26
2-59
ES
O31
6-G
019
1002
47.0−4
234
4227
2.78
10.2
1S
67×
916
.30.
1930
0−1
0250
4.1
800−
1030
*S
KK
263-
65L
ES
O26
3-G
008
1007
46.1−4
329
4027
4.08
10.0
2S
83×
1615
.40.
1551
00−1
0250
4.0
SK
K26
3-15
7LE
SO
263-
G01
4M
I10
1100
.2−4
509
0627
5.54
9.02
S1?
67×
5014
.40.
1916
00−
6700
4.5
5200±1
00F
83op
tS
KK
263-
53L
ES
O26
3-G
024
MI
1015
33.7−4
507
5827
6.20
9.50
SE?
87×
40:
14.3
0.20−6
00−
4650
6.3−1
00−
300
1050±1
00F
83op
t
750−
1100
SK
K26
3-20
LE
SO
263-
G02
910
2109
.8−4
600
5327
7.52
9.31
SE10
8×30
14.2
0.25
300−
5500
5.4
900−
1030
2960±
60R
C3
opt
Not
es:S
KK
258-
89:d
etec
ted
HV
C94
7atv=
262
kms−
1;S
KK
262-
127:
dete
cted
CH
VC
1098
atv=
261
kms−
1;S
KK
262-
59:d
etec
ted
CH
VC
1098
atv=
263
kms−
1.
1074 A. C. Schröder et al.: Parkes H I observations of galaxies behind the southern Milky Way. II.
Fig. B.1. H i profiles of the 14 H i detections in the Vela region. The vertical axis gives the flux density in mJy, the horizontal axis the velocity range(radio convention), generally centred on the radio velocity of the galaxy displaying a width of 1600 km s−1. All spectra are baseline-subtracted andgenerally Hanning-smoothed. The respective identifications are given within the panels.
A. C. Schröder et al.: Parkes H I observations of galaxies behind the southern Milky Way. II., Online Material p 1
Fig. 1. Baseline-subtracted H i profiles of the 162 detections in the Crux/GA region. The vertical axis gives the flux density in mJy, the horizontalaxis the velocity range (optical convention), generally centred on the velocity of the galaxy and displaying a width of 1600 km s−1. All spectraare baseline-subtracted and generally Hanning-smoothed. The identifications are given within the panels. Question marks indicate uncertainidentifications, stars denote a detection not at the centre of the beam.
