Multi-wavelength Observations of Galaxies at z>~2 Mauro Giavalisco (UMass) + The GOODS Team + The...

Multi-wavelength Observations of Galaxies at z>~2

Mauro Giavalisco (UMass)

+ The GOODS Team

+ The COSMOS Team

GOODS: Great Observatories Origins Deep Survey

Color selection at z~2: BzK galaxies

BzK selection more general than UV selection (LBG). It is reddening independent and it includes:

1) Obscured star forming galaxies (larger range of obscuration)

2) Larger range of stellar masses3) Passively evolving galaxies

Well suited for 24m MIPS studies:• Selected range 1.4 < z < 2.5

places strong mid-IR features in 24m band

• Color selection includes objects with red UV continuum, e.g., from extinction

• K-band selection suitable for relatively massive galaxies

(Daddi et al. 2005)

BzK selection: 1.4<z<2.5


GOODS BzK

GOODS-S: 1080 galaxies, K<22.0 175 redshift (17%)

GOODS-N: 273 galaxies, K<20.5 57 redshifts (21%)


Spectra of sBzK galaxies

27 COSMOS BzK<z>=1.87

Daddi et al., in prep.


Spectra of pBzKs

VLT/VIMOS spectra ofpBzKs from Kong et alw/ 2.5h integration

VLT/FORS2 spectra ofpBzKs in the UDF from GMASS w/ 30h integration


Surface brightness profile Analysis:

-2-D modeling using a single Sérsic function using GALFIT Software (Peng et al. 2002)

Exponential disks: n = 1

R1/4 spheroids : n = 4

Ravindranath et al. 2007


Bulge-dominated BzKs

pBzK,

Bulge-like (n>2.5):

sBzK, Bulge-like (n>2.5):


Disk-dominated BzKs

pBzK, Disk-like (n< 2.5):

sBzKDisk-like (n< 2.5):


Profile shapes of BzK Galaxies

About 40% of the pBzKs have bulge-like profiles with the fraction increasing to 60% when only the secure pBzKs are considered.

Star-forming BzKs mostly (80%) have low n (< 2.5) suggesting disk-like, irregulars, or mergers.


Size distributions

Passive BzKs have peak at re ≤ 0.25 arcsec (~ 2.1 kpc) with broad distribution that extends to compact sizes.

Star-forming BzKs are fairly symmetrically distributed about the peak at re ~ 3.5 kpc.


COSMOS BzK galaxies

Bz from SUBARUK from CFHTdown to K

Vega = 21.3

McCracken et al. in prep.

~4x104 ~3000

K<20 Vega64174 galaxies7460 sBzK ~1/sq.arcmin1548 pBzK ~0.2/sq.arcmin

K<21.3 Vega151974 galaxies42105 sBzK2923 pBzK

VLT/VIMOS


Multi-wavelength measures of SFR

MIPS: <f(24m)>=125 Jy, <z>=1.9, and CE01 templates: <LIR> = 1.7e12 Lo, <SFR> ~ 300 Mo/yr

UV continuum + reddening: <SFR> ~ 220 Mo/yr

Radio: stacked VLA data <f(20cm)> = 17 Jy<LIR> = 2e12 Lo, <SFR> ~ 340 Mo/yr

Sub-mm: stacked <f(850m)> = 1.0 mJy (5) <LIR> = 1.0e12 Lo, <SFR> ~ 170 Mo/yr

X-ray: stacked 8.5 soft-band detection, no significant hard-band. Far below expected AGN level. <SFR> = 100 - 500 Mo/yr (Persic 2004, Ranalli 2003 conversions)

On average, multi-wavelength SFR tracers agree reasonably wellwith expectations from low-z correlations, templates & analogs.


UV vs. IR SFRs: BzK-selected galaxies at z ~ 2

B-band samples ~1500A UV continuum at z~2; B-z measures UV continuum slope.

f(24m) / f(B) correlates strongly with B-z color, as expected if UV continuum slope results from dust reddening. Log scatter is a factor of ~3 (including effects of the broad BzK z-range).

Brighter/more luminous mid-IR sources (LIR > 1012 Lo) tend to exceed expected IRX-, while less luminous sources match or fall below it (possibly including “passive” BzKs.


Radio vs. 8 μm

•Radio and mid-IR indicators agree at low to medium luminosity, L(8m)<~2x1011 LO

•For L(8m)>2x1011 LO, LIR(mid-IR) in excess over LIR(radio), as well as other estimators, compared to local templates: mid-IR excess

All “monochromatic” luminositytransformed into bolometric IR luminosity (8-1000 m) using the Chary and Elbaz (2001) and Dale and Helou (2002) templates);

Bolometric IR luminosity transformed into SFR using Kennicutt 1998 (the two used interchangeably)

Daddi et al. 2007


70 m (warm dust emission) and 850 m (cold dust emission) luminosity vs. midIR luminosity exhibit similar trends


UV vs. mid-IR derived SFR

SFRUV,obscured = SFRUV,corr - SFRUV,uncorr

Does the UV under-estimate the true SFR or is it the mid-IR over-estimating it compared to the local templates?


UV vs. Radio

UV and radio-derived SFR agrees relatively well.This shows that for high luminosity mid-IR over-estimates LIR, and thus SFR, at high IR luminosity. Why?

UV,corr reliable estimator of SFR in most cases


Recipe for SFR

• If SFRUV,corr/SFR(8mm)<~3

– SFR = SFR(8mm) + SFRUV,uncorr

• If (SFR(8mm)+SFRUV,uncorr)/SFRUV,corr<~3– SFR = SFR(8mm)

• If (SFR(8mm)+SFRUV,uncorr)/SFRUV,corr>~3

– SFR = SFRUV,corr

•L(UV) corrected for obscuration using UV slope and Calzetti law provides reliable SFR estimates•The typical z~2 URLIG is transparent to UV radiation (not true for local ULRIG)


Tight SFR-Stellar Mass Correlation

•Millennium sims predictions different: less SF and shallower slope•Significant population of ULIRG•Very different from local ones:

•UV bright and transparent•Large duty cycle: 40% or ~0.5Gyr•Unlikely produced by mergers

Green points from radio measures


Massive Galaxies at z~2Sims make star-forming massive galaxies too soonPassive galaxies OK

Duty cycle estimated from fraction of SF ULRIG in mass- and volume-limited sample: 0.4, corresponding to ~0.5 Gyr


The mid-IR Excess (MIRX)

mid-IR excess observed in most galaxies with L(8m)>2x1011 LO

mid-IR excess responsible for galaxies with SFR(8m)~1000 MO/yr

(true SFR rarely exceeds a few MO/yr)

For typical z~2 galaxies, local SED templates work

Daddi et al. 2007b


Properties of mid-IR Excess Galaxies


The SED of midr-IR Exess Galaxies


The mid-IR galaxies

Fraction of mid-IR galaxies increases with mass,


The origin of the mid-IR Excess: Hard Spectrum X-Ray Sources

0.5-2 keV

0.5-2 keV

2-8 keV

2-8 keV

Normal

Normal

Excess

Excess


The origin of the mid-IR Excess: Hard Spectrum X-Ray

Sources

Spectral shape implies very large column density, up to NH~1025. In turn, this implies very large luministy, up to L~1045 erg/s


Compton thick AGN

•X-ray spectral index implies column density of about 1024-1025.

•In turn, this implies X-ray luminosity up to ~1044 erg/s. AGN bolometric luminosity~SF bolometric luminosity

•All this energy is released into the IGM. •Very energetic feedback consistent with that required to stop SF

•Very large population of Compton thick AGN buried inside mid-IR BzK.

•Contribution to X-ray background is modest: 10-15%

•BH growth significantly larger than that of SMGs

•Stellar and BH growth consistent with Magorrian relationship


Conclusions• BzK selection more general, representative of the mix at z~2

– Both active and passive galaxies included, with a larger spread of UV colors, obcuration

– Larger morphological variety: bulges and disks are included

• BzK galaxies at z~2 include significant faction of ULIRG, which are very different from local ones– UV bright and UV transparent; morphology not compact, often disk-like– Duty cycle of ULIRG phase is large, 40% or 0.5 Gyr, unlikely merger induced– Today these must be looked among very massive and old galaxies

• Widesprerad presence of Compton-thick AGN in z~2 galaxies. – Fraction increases w/mass– Large deposition of energy into the IGM, LAGN~LSF. Feedback energy can

eventually stop SF

• More BH growth than in SMG; coeval growth of stellar and BH mass growth, consistent with today’s “Magorrian” relation

• Modest contribution to XBL 10-15% at most


Large Millimeter Telescope (LMT)U Mass – INAOE Mexico

Projected start of scientific observations at 3 mm ~Aug 2008


LMT: a new powerful facility for

(sub)-mm observations

• A 50-m aperture will greatly improve observations at these critical wavelengths

– Higher mapping speeds big bolometer arrays

– Higher flux sensitivity bigger telescopes

– Less source confusion bigger telescopes

– Source Redshifts new technologies


The LMT Submm Galaxy Program

• First-generation LMT instruments chosen to address avariety of science topics

– AzTEC – large FOV imaging for source detection– Redshift Search Receiver and 1mm Receiver – spectroscopic redshifts– SPEED – quickly measure SED

• LMT + first generation instruments will provide a new view of faint sources and of the Far-IR background

– Detect fainter sources with high angular resolution (~6 arcsec beam at 1 mm)

• Improved measures of luminosity function

– Study environments and link to large scale structure– Explore cosmic evolution of the population

• LMT project scientist: Min Yun• AzTEC PI: Grant Wilson

LMT/AzTEC simulation including high-redshift starburst galaxies, Galactic cirrus, Sunyaev-Zel’dovich clusters, Cosmic Microwave Background

0.5 deg

AzTEC/LMT Surveys for SMGs and SZE Clusters

Large Area Survey:30 sq. degrees600 hrs, 100,000 sources

The Deep Survey:25 sq. arcmin to confusion limit (0.01mJy)750 hrs, 1000 sources


AzTEC – Source Detection1. improved accuracy in source-counts2. greater dynamic range in source-counts


Lyman-break galaxiesULIRGSMassive ellipticals

ultra-massive, rare, starburst galaxies

LMT + AzTEC


S-COSMOS IRAC-deep sensitivities (5)

S-COSMOS MIPS sensitivities (5)

Galaxy SED templates + sensitivities vs. z (0.5, 1, 2, 3)

S-COSMOS Cycle 2 sensitivity goals achieved !!QuickTime™ and a

TIFF (LZW) decompressorare needed to see this picture.

LMT + AzTEC


Redshift Search Receiver

Spectroscopic Redshift Survey

• 36.5 GHz Bandwidth(74-110.5 GHz)

• 90 km/s resolution

• At least one CO line except for 0.4<z<1 and 2+ lines for z>2.8

Red - no line Yellow -one CO line Green - two CO lines


For dusty systems at high redshift, molecular lines may be ONLY way to measure z!

Spectroscopy with Redshift Receiver System


Redshift Receiver System on the FCRAO and Haystack Telescope


Photometric redshifts with SPEED

LMT+SPEED(5) in 1 minute

CFRS14a (z=2.06)

VLA (24hrs)

SPITZER CO redshifts practical for

only some 1000 objects

Photo-z can be obtained in minutes using SPEED if other data available (e.g. VLA, Spitzer)

Photo-z good to 10%

Yun & Carilli (2002), Hughes et al. (2002)


GOODS IRAC observations have identified a dozen candidates for even older (~700 Myr), more massive (up to ~10x the Milky Way!) galaxies at z~5-6.

Spectroscopy has been impossible so far - but if correct, these would be unexpected in current galaxy formation models.

Unexpected “Big Babies” at z ~ 5-6 ?

Mobasher et al. 2005; Wiklind et al. 2007


z ~ 5 z ~ 6

GOODS/IRAC “weighs” and age dates galaxies at z~5-

6. The red starlight seen by IRAC implies ages ~100-500 Myr, and masses up to that of the Milky Way. Substantial star

formation took place during the reionization era at z ~ 7-9.

IRAC 3.6m:

H. Yan et al. 2005, 2006


z~3 spectroscopy

Popesso et al., Vanzella et al. in prep. 2006


z~4 spectroscopy

Variety of spectral “types”

Very similar to the z~3 galaxies

Emission of Lya observed together with weak interstellar absorption lines

Stronger absorption lines are present when Lya is obsered in absorption

Effect of geometry of ISM?

Vanzella et al., Popesso et al., in prep. 2006


z~4 spectroscopy

Popesso et al, in prep.


z~5 spectroscopy

At z~5 and 6 selection effects make “emission” galaxies easier to confirmspectroscopically

Vanzella et al. in prep.


Composite spectrum ofi-band dropouts

The spectral properties of “observed” LBGs at z~6 are very similar to some LBGs observedat z~3.

At z~6 it is very hard to obtain spectra of those LBGs with no Lya. Selection effect!

Vanzella et al., Giavalisco et al 2006, in prep.


Stellar populations of LBGs at z~5-6

(Yan et al. 2005; also Eyles et al. 2005)

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Multi-wavelength Observations of Galaxies at z>~2 Mauro Giavalisco (UMass) + The GOODS Team + The...

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