Starbursts AGN and Quiescent Star Formation in High

Starbursts, AGN, and Quiescent Star Formation in High Redshift Galaxy Clusters Nicole Homeier ACS Science Team Johns Hopkins University October 2006 Galaxy Mergers Workshop STSc. I

ACS Science Team Collaborators Cluster/Galaxy Evolution PI: Holland Ford (JHU) Co-PI: Garth Illingworth (UCSC) Ricardo Demarco (JHU) Marijn Franx (Leiden) Brad Holden (UCSC) Nicole Homeier (JHU) Simona Mei (JHU) Marc Postman (STSc. I) Alessandro Rettura (JHU) Piero Rosati (ESO) Arjen van der Wel (JHU) Andrew Zirm (JHU) October 2006 Galaxy Mergers Workshop STSc. I

Do we need major gas-rich mergers to build up the RCS? • Let’s look back ~8 Gyr, z=1, and see what’s happening October 2006 Galaxy Mergers Workshop STSc. I

z ~ 1 Cluster Survey Targets Cluster Redshifts Velocity Dispersion X-ray Lum. (1044 erg/s) ACS Filters Total Orbits MS 1054 0. 831 (154) 1112 23. 3 V, i, z 24+16 CL 0152 0. 837 (102) 1250 7. 8 r, i, z 24+16 CL 1604 +4304 0. 897 (22) ~100 2. 0 V, I 4 CL 1604 +4321 0. 924 (44) 935 <1. 2 V, I 4 CL 0910 1. 101 (10+) N/A 1. 5 i, z 8 CL 1252 1. 235 (36) 755 2. 5 i, z 32 CL 0848 -A, B 1. 265 (~40) 640 (A) 1. 5 (A), ~1 (B) i, z 24 October 2006 Galaxy Mergers Workshop STSc. I

The Red Sequence in z ~ 1 Clusters Elliptical S 0 Spiral Mean Zf>2. 2 -2. 6 Blakeslee et al. 2003, Mei et al. 2006 a, b, Blakeslee et al. 2006, Homeier et al. 2006 October 2006 Galaxy Mergers Workshop STSc. I

Mean Ages from the Scatter about the RCS • use the intrinsic scatter about the CMR to constrain the average and formation redshift Bursts, tmax<t<tend, BC 03 Homeier et al. 2006 October 2006 Galaxy Mergers Workshop STSc. I

The Red Sequence in z ~ 1 Clusters If these early-type galaxies formed via ‘mergers’, it’s at high redshift, and not from major mergers of the type we see in the local universe. Mean Zf>2. 2 -2. 6 Cluster E/S 0 s passively evolving to present day. But there is evolution, not everything in massive cluster halos is passively evolving between z=1 and z=0. October 2006 Galaxy Mergers Workshop STSc. I

$Morphology-density relation for our sample at z ~ 1 Ellipticals have about same fraction$

Morphology-density relation for our sample at z ~ 1 Ellipticals have about same fraction as found locally. S 0 fraction is lower at these redshifts. Population built up by infalling spirals? October 2006 Galaxy Mergers Workshop STSc. I Postman + ACS Team 2005

How are the massive galaxies (not) evolving? Coma z=0. 33 z=0. 59 z=0. 83 Holden et al. 2006 October 2006 Galaxy Mergers Workshop STSc. I

• We don’t need gas-rich mergers to build up the high mass early-types in clusters from z=1 to z=0 (although some could be accommodated). • Do the rest of the observations agree with this? Do we observe a significant fraction of gas-rich mergers in clusters? October 2006 Galaxy Mergers Workshop STSc. I

Massive X-ray clusters at z=1 Cl. J 0152 -1357, z=0. 84 October 2006 MS 1054, z=0. 831 Galaxy Mergers Workshop STSc. I

Locating star-forming galaxies at z=1 • [OII] is available for the most galaxies, get it for free with a redshift survey – Spec surveys (e. g. Lubin et al. 2001, Homeier, Demarco et al. 2005, Tran et al. 2005) – Narrow-band imaging surveys (e. g. Crawford et al. 2006, Sato & Martin et al. 2006, Lotz et al. 2003) October 2006 Galaxy Mergers Workshop STSc. I

Example: Morphologies of [OII] galaxies in CL J 0152 15% merger candidates 30% in RCS 20% early-type (but sub-L*) 70% visual spirals (3/5 compact early-types have Sersic n=1 -2) Homeier et al. 2005 October 2006 Galaxy Mergers Workshop STSc. I

Looking for star formation at z=1 • [OII] is available for the most galaxies, get it for free with a redshift survey – Spec surveys (e. g. Lubin et al. 2001, Homeier, Demarco et al. 2005, Tran et al. 2005) – Imaging surveys (e. g. Crawford et al. 2006, Sato & Martin et al. 2006, Lotz et al. 2003) Cluster galaxy SFRs from [OII] are already lower than field galaxy SFRs at z~1 (e. g. Lubin et al. 2001). Extinction? Are we missing significant numbers of starforming galaxies? October 2006 Galaxy Mergers Workshop STSc. I

Halpha SFRs for 4 lower mass EDis. CS clusters @z~0. 7 Show lower SFRs than the field population Starburst fraction within 0. 5 R_200 < 5% But no morphological info Finn et al. 2005 October 2006 Galaxy Mergers Workshop STSc. I

Rest-frame U-B Colors Sample of late-type galaxies in 4 clusters, and a comparison field sample At a given absolute B magnitude, the cluster galaxies are significantly redder. Even the bluest cluster population (excluding the RCS late-types) is redder than the field population. October 2006 Galaxy Mergers Workshop STSc. I cluster field Homeier et al. 2006

Halpha selection for MS 1054 Can select SF galaxies, and also get an upper limit of the SFRs of the late-type spec. members Blue - detected Orange - undetected Upper Limit ~8 -10 M_sun/yr Homeier, Finn, et al. , in prep October 2006 Galaxy Mergers Workshop STSc. I

35 Halpha sources in MS 1054 field 13 spec. confirmed cluster members 6 obvious non-mem 7 spec non-mem = 9 probable new October 2006 Galaxy Mergers Workshop STSc. I

For Cl 0152: 15% of the [OII] population are merger/interaction candidates [OII] population is ~20% of the total cluster population For MS 1054: >> gas-rich merger candidates are only In the strongest Halpha ~3% of the total cluster population MB<galaxies, ~20% are 20. 5 merger/interaction candidates October 2006 Galaxy Mergers Workshop STSc. I

But what about optically completely obscured starbursts? • Let’s check with MIPS – 24 micron = ~13 micron rest-frame – On a weak PAH feature October 2006 Galaxy Mergers Workshop STSc. I

MIPS source extraction • Cl 0152 and MS 1054, z=0. 84 • 2 overlapping pointings for each cluster • 268 sources in Cl 0152, 244 in MS 1054 -70% in MS 1054 have an ACS counterpart within (5” matching radius) – Only 4 (Cl 0152) and 11 (MS 1054) are spec. cluster members October 2006 Galaxy Mergers Workshop STSc. I

Negligible “hidden” star formation 7 sources with both MIPS and Halpha, 2 spec members For the single galaxy with an Halpha- and MIR-derived SFR, they agree quite well. Still have to sift through all the MIPS-only detections, but most appear not to be cluster members (either too big or too faint), and most of the Halpha sources are not detected. Conclusion: Negligible number of obscured starbursts in massive clusters at z=0. 84 October 2006 Galaxy Mergers Workshop STSc. I

But a significant number of AGN? 9 MIPS sources that are either a spec mem, have a radio, or X-ray detection, and no Halpha October 2006 Galaxy Mergers Workshop STSc. I

$Evolution in the AGN fraction? But selection important Martini et al. 2006 X-ray selected$

Evolution in the AGN fraction? But selection important Martini et al. 2006 X-ray selected Dressler et al. 1995, 1999, optical only October 2006 Optical, X-ray, Radio, MIR Galaxy Mergers Workshop STSc. I Homeier et al. , in prep

Starbursts, AGN, and Quiescent Star Formation in Massive Galaxy Clusters at z=0. 84 October 2006 Galaxy Mergers Workshop STSc. I

Close, Red Pair Candidates CL 0152: 12 pairs observed; 5. 7 expected MS 1054: 9 pairs observed; 5. 5 expected In both clusters, the number of pairs with sep < 20 kpc is ~2 times that predicted from MC sims Postman, Bartko et al. , in preparation October 2006 Galaxy Mergers Workshop STSc. I

Monte Carlo Simulations 1. 2. 3. 4. Create a reference galaxy distribution that has the same global clustering properties as the actual data on scales > 150 kpc but which erases correlations on smaller scales. This is achieved by shifting the observed positions using offsets randomly drawn from a Gaussian distribution with ~ 50 - 100 kpc. Compute the average of and standard deviation in the number of pairs as a function of separation and local galaxy surface density from 1, 000 such simulations. Use the above results to estimate the significance of features in the observed galaxy density vs pair separation relationship. Postman, Bartko et al. , in prep October 2006 Galaxy Mergers Workshop STSc. I

Kinematic pairs confirmed Red Pair Sim al. 2006 Results Tran et October 2006 Galaxy Mergers Workshop STSc. I

Classification Methodology • Visual classification by Bartko done in F 775 W (Restframe B). • Two classification categories: – Interaction: galaxy with interaction feature (tidal tail, irregular disk, etc. ) even if no companion seen – Merger: at least 2 galaxies in close proximity with interaction features (tidal tail, irregular disk, etc. ) • Reliable automated merger classification is challenging but becoming more feasible (e. g. , Lotz et al. 2006). Nonetheless, visual classification is a competitive approach when sample size <5, 000 objects. October 2006 Galaxy Mergers Workshop STSc. I

Classification Methodology BUMPINESS ASYMMETRY MS 1054 -0321 & RXJ 0152 -1357 CONCENTRATION All galaxies with i < 24 mag October 2006 RCS galaxies with i < 24 mag Galaxy Mergers Workshop STSc. I

Classification Methodology October 2006 Galaxy Mergers Workshop STSc. I

Merger and/or Interacting System Candidates CL 0152 MS 1054 Green 2006 highlights the spectroscopically confirmed cluster members; others are October Galaxy Mergers Workshop cluster member candidates based on their photo-z’s. STSc. I

Merger Fraction by Morphology Class and Cluster Radius MS 1054 -0321 (z = 0. 831) <f 200> = 0. 13 0. 08 RXJ 0152 -1357 (z = 0. 836) <f 200> = 0. 20 0. 07 October 2006 Galaxy Mergers Workshop R/R 200 STSc. I

$Merger Fraction & Rate • Completeness & projection corrected fraction of mergers (and excess$

Merger Fraction & Rate • Completeness & projection corrected fraction of mergers (and excess close-pairs) within R 200 and with MV < -20. 3 are: – fm = 0. 13 +/- 0. 08 in MS 1054 (Lum frac = 0. 08) – fm = 0. 20 +/- 0. 07 in CL 0152 (Lum frac = 0. 11) • Merger rate = ncl fm. Tm-1 (e. g. , Lotz et al. 2006) – 2. 5 (± 2. 0) Gyr-1 Mpc-2 in MS 1054 – 7. 9 (± 4. 8) Gyr-1 Mpc-2 in CL 0152 • Early type mergers are largely confined to the central ~600 kpc, consistent with the known morphologydensity relation. Postman, Bartko et al. , in prep October 2006 Galaxy Mergers Workshop STSc. I

CL 0152 -13 z = 0. 837 CL 16 h+4321 z = 0. 924 E MS 1054 -03 S 0/E CL 0910+54 E CL 1226+33 S 0/Sa CL 1252 -29 z = 0. 831 z = 0. 888 z = 1. 10 z = 1. 235 E E CL 16 h+4304 CL 0848+44 z = 0. 895 Sb/Sc October 2006 z = 1. 265 Brightest Cluster Galaxies z ~ 1 BCG exhibit a broader morphological distribution than their z=0 counterparts. M 2 - M 1 in the majority z~1 clusters is smaller (<0. 35 mag) than that in ~85% of the z~0 rich Abell clusters Evidence for eventual near equal mass merger with BCG seen in at least 2 of these 8 clusters (CL 1252 and CL 0848). Significant tail of underluminous BCGs relative to low-z BCG luminosity distribution (after modeling expected evolution). Many of these BCGs will undergo a significant increase in mass before z~0. 5. Postman et al. , in prep E Galaxy Mergers Workshop STSc. I

Conclusions • Negligible number of starbursts, but there is quiescent SF and AGN at z=1 in clusters at z=0. 84. Dust levels and extinction levels are low in most SF-galaxies, and SFRs are low. – for the 1 galaxy in MS 1054 where we have an Halpha SFR and a mid-IR SFR, they agree very well • We do observe mergers. MS 1054 & CL 0152 have comparable merger fractions within R 200. The mergers account for ~10% of the cluster light. • Early-type mergers are generally confined to central regions. • BCGs in many z~1 clusters still undergoing significant mass assembly. • October 2006 Galaxy Mergers Workshop STSc. I

Quasars and RCS Galaxies • If all massive earlytypes have SMBHs • And all SMBHs and their hosts go through a quasar phase • And massive clusters have 50 -100 RS members at z=1 with zf=2 -5, span of ~3 Gyr • # of galaxies going through a quasar phase >(50100*tau)/3, tau=0. 3, #>5 -10 for some significant length of time 10 3 100 Myr October 2006 Galaxy Mergers Workshop STSc. I tau 300 Myr

BCG Luminosity Evolution Left: The rest frame absolute B-band metric magnitude (14 kpc aperture) as a function of redshift for our z~1 sample and for solar metallicity models with varying star formation histories. Right: The magnitude difference between the tau=0. 6, z. F=4. 5 model and other models and the data. The flux ratio corresponding to the magnitude difference is shown on the right ordinate. Also shown is the October 2006 Galaxy Mergers Workshop histogram of z~0 BCG magnitude differences (similarly normalized) along with the location of the Coma STSc. I cluster BCG. Horizontal dashed lines show the 1 and 2 sigma levels. Different from Gaussian at 98% C. L.

Use 8 mum to identify probable AGN - also to help matching accuracy Brand et al. 2006 October 2006 Galaxy Mergers Workshop STSc. I

From observed 24 mum to SFR • Go from observed 12 mum to 15 mum flux density by using Dale et al. 2001 SEDs (factor of 2. 7 difference in 13/15 flux densities over the range of SEDs, from quiescent to active) • Empirical 15 mum flux density vs. FIR luminosity (Elbaz et al. 2002) • Use LFIR-SFR relation (Kennicutt 1998) October 2006 Galaxy Mergers Workshop STSc. I

From observed 24 mum to SFR October 2006 Galaxy SEDs from Dale et al. 2001 Mergers Workshop STSc. I

What are the “new” late-type galaxies? Zooming in on z=0. 8 October 2006 Red - ellipticals Orange - S 0 s Blue - spirals Black - mergers Galaxy Mergers Workshop STSc. I

How are the massive galaxies evolving? Coma z=0. 33 z=0. 59 z=0. 83 Holden et al. 2006 October 2006 Galaxy Mergers Workshop STSc. I

How are the massive galaxies (not) evolving? Coma z=0. 33 z=0. 59 z=0. 83 Holden et al. 2006 October 2006 Galaxy Mergers Workshop STSc. I

Conclusions • • Fraction of massive early-type galaxies flat with redshift. The evolution predominately occurs in lower mass systems. Typical mass of the late-types that appear at cluster outskirts similar to that S 0 galaxies at z=0 Galaxies at z=0 of the mass of late-type galaxies at z=0. 8, have ages of 5 -7 Gyr, less than the lookback time to z=0. 8 October 2006 Galaxy Mergers Workshop STSc. I

Butcher-Oemler effect B-O effect is detected if one counts within r 200, but the effect disappears if 0. 5 r 200 is used Determining population fractions is uncertain, without a large spec sample one must use statistical background subtraction, then there is the problem with what is “blue”. Possibly a better method for quantifying cluster galaxy evolution is to look at the total cluster star formation rate. October 2006 Galaxy Mergers Workshop Ellingson et al 2001, see also Andreon & Ettori 2004 STSc. I