Low-luminosity Extragalactic H 2 O Masers Yoshiaki Hagiwara ASTRON 22 GHz Extragalactic H 2 O Masers High-luminosity (L H 2 O > ~10 Lsun)... ca.35 galaxies (Megamasers) NGC4258, NGC3079, NGC4945, Circinus, Most of these have been found in narrow-line AGNs Low-luminosity (L H 2 O < ~1 Lsun)... ca. 10 galaxies NGC253, M82, IC342, M33, M51, Found in nearby star-forming galaxies, starbursts, and AGNs. NOTE: Strongest Galactic H 2 O maser (W49N) is as luminous as 1 Lsun. Some Low-L masers arise in star-forming regions. These masers are associated with AGN-activity. NGC 3079 ~100 Lsun Sherwood et al. Why Study the Low-luminosity H 2 O masers? Learn something about the extragalactic star-formation. - The evolution and kinematics. - Structures of exotic star-formation in outer galaxies. Use the masers for Astrometry (IC10, M33, LMC, SMC). - Parallaxes establish 3D-kinematics for the Local group (Brunthaler et al. 2003, 2004). - Proper motions yield galactic kinematics. Learn something about the environment of low-luminosity AGN. - The masers at shock with molecular clouds. VLBI/VLA actual images Low-luminosity H 2 O Masers H 2 O maser in the starburst galaxy M82 H2O Maser Spectrum in M82 (Baudry, Henkel et al. 1994) OH masers (blue-shifted) imply star-formation in the expanding shell of SNR (Pedlar et al. 1999, Wills et al. 1999). Molecular super bubble structures in CO (Matsushita et al. 2000, Weiss et al. 2001) Weak ( Lsun) H 2 O masers (Claussen et al. 1984) VLA at 1" res could not resolve the maser (Baudry & Brouillet 1996). New VLA Observations -Angular res: arcsec - A Configuration -Velocity range: V( LSR ) = km/s -Velocity res: 1.3 km/s Xray source S1 S2 S1 New2 New1 New2 S2S2 M82 S1 : Compact HII Region S2 : 0.2 arcsec (3.5 pc) away from Compact HII Region. - Followed up by MERLIN. New1 & 2 : Weak and narrow lines No nearby continuum What is ' S2 ' and other 'new' masers? No continuum counterparts for these H 2 O masers. The masers are associated with neither thermal HII regions nor SNRs. The masers could trace the earlier phase of SF, like bipolar outflows in YSOs. Need for mapping at higher resolution ~ < 0.01 pc (Signatures of Galactic SF structures ~ < 0.01 pc) MERLIN, at res ~ 30 mas ~ 0.2 pc, barely resolved the maser. S2 MERLIN 22 GHz CO (2-1) Intensity map with PdBI & the 30m (Weiss et al. 2001) and positions of H2O masers. CO(2-1) H2OH2O VLA Observations of NGC4051 -T ype 1 Seyfert, D=9.7 Mpc (VLA-A: 0.1 arcsec = ~ 5pc) -Narrow-line Seyfert 1 (NLS1) (Osterbrock & Pogge 1985) -Weak H 2 O emission (~2 Lsun) (Hagiwara et al. 2004) -H 2 O maser in a type 1 nucleus is rather unique. Effelsberg and VLA Spectra Quasi-symmetric velocity distribution w.r.t Vlsr = 710 km/s. VLA-A could not resolve the masers at 0.1 arcsec, or 5pc. Vsys = 730 km/s Vsys No high-velocity emission was seen at rms ~ 5 mJy/ch within km/s w.r.t Vsys. What is the maser in NGC4051? The radio continuum peak coincides with the maser. - AGN-activity -But, why is the low-luminosity (~ 2 Lsun) ? Because... -Narrow-line Seyfert 1 -Low inclination disc-like configuration Lower column density in the line-of-site Dense and warm molecular gas environment (HCN, HCO+). -Star-forming activity ?? The H 2 O maser in M51 Terashima & Wilson (2004) + : Hard Xray point source Hagiwara, Henkel, et al. (2001) Vsys ~ 470 km/s -Nearby star-forming galaxy, hosting a low-luminosity AGN -Weak (0.1-1 Lsun) H2O maser (Ho et al. 1986) -Hagiwara, Henkel et al. (2001) pinpointed the maser in the vicinity (0.1", ~5pc) of the radio continuum nucleus with the VLA-A snap-shot. What is the origin ? AGN-activity or Star-forming-activity? New VLA Observations of M51 A weak blue-shifted (V=445 km/s) and red-shifted (V= km/s) components were detected arcsec resolution Red-shifted maser: 0.1" (~ 5pc ) north the radio (3.6-cm) nucleus -Confirmed the results in Hagi, Henkel et al. (2001) A blue-shifted maser: 0.6" (~30pc) north-west the nucleus. Where is the maser in M51 ? 3.6-cm VLA map: Bradley, Kaiser, Baan (2004) Origin of the maser in M51 VLA maps: Bradley, Kaiser, Baan (2004) The red-shifted masers are likely to be related to AGN-activity. The blue-shifted maser might be originated from the gas-rich environment in star-forming region. VLBA resolved the maser ! The presence of a thin disc (Moran et al. 2003)? Blue-shifted emission Red-shifted emission VLA 3.6-cm Jet Maser in NGC1068 C Weak (~10 Lsun) H 2 O maser at the radio knot (C), located ~30 pc north the nucleus. - The maser intensity is variable. - Proper motion over 2 epochs (1983 and 1987)? The origin of the maser (Gallimore et al. 2001) - Molecular outflows in YSOs - Amplifying the radio jet - Shock in molecular clouds in star-forming site Nakai et al. (1995) Gallimore et al. (1996) MERLIN Observations of the Jet Maser According to preliminary data analysis... The jet maser was not detected in these observations Because of... -Intensity variability -Maser is resolved at 30 mas, ~ 3pc. -MERLIN sensitivity ( rms ~ 4 mJy/beam/ch) Nucleus S1 Knot C NGC cm Radio Continuum What do the Low-L H2O Masers tell us ? Particular conditions required for H 2 O maser -Density (10^8 - 10^10 cm /cm^3) -Warm ( K) What can be traced by low-luminosity masers? Low-L H 2 O masers are outside of the nucleus (e.g. Claussen & Lo 1986). In Star-forming and starburst galaxies Extragalactic star forming phenomena: Shock, disc around a central star, and outflows in YSOs. (M82 ?) Scales of Galactic star forming signatures are < pc. - Even VLBI cannot resolve ! - Thermal radio continuum (M33, IC10, M82,) - Non-thermal SNR - Expanding shell of SNRs. - Startburst nucleus ? (NGC 253) - Galaxy-galaxy merging or interaction ? (NGC 6240) In AGN Disc or torus of low-luminosity AGN (e.g. M51) - Jet, or non-nuclear region (NGC 1068) - Molecular environments: Outflows in YSOs. Two different populations of extragalactic H 2 O masers (e.g. Ho et al. 1986) 21-cm VLA radio continuum - FIR (100 um + 60 um) 21cmVLA data from Condon et al. (1990) ( Hagiwara, in prep ) 21-cm compact radio continuum: AGN or SNR FIR (100um): Dust emission Radio-excess galaxies = H 2 Omegamasers FIR-excess galaxies = OH megamasers Low-L H 2 O masers The future is Water masers in general Diagnosing tools in extragalactic objects -Tracers of High density, warm regions Low-luminosity H 2 O masers -Extragalactic star-forming regions OH(H.Kloeckner and W.Baan), HCHO masers and, of course, we need more H 2 O masers CH 3 OH masers: Massive star-forming regions in outer galaxies ? (not yet detected)