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

2. October 2006Galaxy Mergers Workshop STScI 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 (STScI) Alessandro Rettura (JHU) Piero Rosati (ESO) Arjen van der Wel (JHU) Andrew Zirm (JHU)

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

4. October 2006Galaxy Mergers Workshop STScI z ~ 1 Cluster Survey Targets ClusterRedshiftsVelocityDispersion X-ray Lum. (10 44 erg/s) ACS Filters Total Orbits MS1054 0.831 (154) 111223.3V,i,z24+16 CL0152 0.837 (102) 12507.8r,i,z24+16 CL1604 +4304 0.897 (22) ~1002.0V,I4 CL1604 +4321 0.924 (44) 935<1.2V,I4 CL0910 1.101 (10+) N/A1.5i,z8 CL1252 1.235 (36) 7552.5i,z32 CL0848- A,B 1.265 (~40) 640 (A) 1.5 (A), ~1 (B) i,z24

5. October 2006Galaxy Mergers Workshop STScI The Red Sequence in z ~ 1 Clusters Elliptical S0 Spiral Blakeslee et al. 2003, Mei et al. 2006 a,b, Blakeslee et al. 2006, Homeier et al. 2006 Mean Z f >2.2-2.6

6. October 2006Galaxy Mergers Workshop STScI Mean Ages from the Scatter about the RCS use the intrinsic scatter about the CMR to constrain the average age and formation redshift Homeier et al. 2006 Bursts, t max <t< tend, BC03

7. October 2006Galaxy Mergers Workshop STScI The Red Sequence in z ~ 1 Clusters Mean Z f >2.2-2.6 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. Cluster E/S0s passively evolving to present day. But there is evolution, not everything in massive cluster halos is passively evolving between z=1 and z=0.

8. October 2006Galaxy Mergers Workshop STScI Morphology-density relation for our sample at z ~ 1 Ellipticals have about same fraction as found locally. S0 fraction is lower at these redshifts. Population built up by infalling spirals? Postman + ACS Team 2005

9. October 2006Galaxy Mergers Workshop STScI How are the massive galaxies (not) evolving? Coma z=0.33 z=0.59 z=0.83 Holden et al. 2006

10. October 2006Galaxy Mergers Workshop STScI 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?

11. October 2006Galaxy Mergers Workshop STScI Massive X-ray clusters at z=1 ClJ0152-1357, z=0.84 MS1054, z=0.831

12. October 2006Galaxy Mergers Workshop STScI 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)

13. October 2006Galaxy Mergers Workshop STScI Example: Morphologies of [OII] galaxies in CL J0152 Homeier et al. 2005 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)

14. October 2006Galaxy Mergers Workshop STScI 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 star- forming galaxies?

15. October 2006Galaxy Mergers Workshop STScI Halpha SFRs for 4 lower mass EDisCS clusters @z~0.7 Show lower SFRs than the field population Starburst fraction within 0.5R_200 < 5% But no morphological info Finn et al. 2005

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

17. October 2006Galaxy Mergers Workshop STScI Halpha selection for MS1054 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

18. October 2006Galaxy Mergers Workshop STScI 35 Halpha sources in MS1054 field 13 spec. confirmed cluster members 6 obvious non-mem 7 spec non-mem = 9 probable new

19. October 2006Galaxy Mergers Workshop STScI For Cl0152: 15% of the [OII] population are merger/interaction candidates [OII] population is ~20% of the total cluster population >> gas-rich merger candidates are only ~3% of the total cluster population M B <- 20.5 For MS1054: In the strongest Halpha galaxies, ~20% are merger/interaction candidates

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

21. October 2006Galaxy Mergers Workshop STScI MIPS source extraction Cl0152 and MS1054, z=0.84 2 overlapping pointings for each cluster 268 sources in Cl0152, 244 in MS1054-- 70% in MS1054 have an ACS counterpart within (5” matching radius) –Only 4 (Cl0152) and 11 (MS1054) are spec. cluster members

22. October 2006Galaxy Mergers Workshop STScI 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

23. October 2006Galaxy Mergers Workshop STScI 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

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

25. October 2006Galaxy Mergers Workshop STScI Starbursts, AGN, and Quiescent Star Formation in Massive Galaxy Clusters at z=0.84

26. October 2006Galaxy Mergers Workshop STScI Close, Red Pair Candidates MS1054: 9 pairs observed; 5.5 expected CL0152: 12 pairs observed; 5.7 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

27. October 2006Galaxy Mergers Workshop STScI Monte Carlo Simulations 1.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. 2.This is achieved by shifting the observed positions using offsets randomly drawn from a Gaussian distribution with  ~ 50 - 100 kpc. 3.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. 4.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

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

29. October 2006Galaxy Mergers Workshop STScI Classification Methodology Visual classification by Bartko done in F775W (Rest- frame B).Visual classification by Bartko done in F775W (Rest- frame B). Two classification categories: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.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.

30. October 2006Galaxy Mergers Workshop STScI Classification Methodology All galaxies with i < 24 mag RCS galaxies with i < 24 mag ASYMMETRY CONCENTRATION BUMPINESS MS1054-0321 & RXJ0152-1357

31. October 2006Galaxy Mergers Workshop STScI Classification Methodology

32. October 2006Galaxy Mergers Workshop STScI Merger and/or Interacting System Candidates CL0152 MS1054 Green highlights the spectroscopically confirmed cluster members; others are cluster member candidates based on their photo-z’s.

33. October 2006Galaxy Mergers Workshop STScI Merger Fraction by Morphology Class and Cluster Radius MS1054-0321 (z = 0.831) = 0.13  0.08 RXJ0152-1357 (z = 0.836) = 0.20  0.07 R/R 200

34. October 2006Galaxy Mergers Workshop STScI Merger Fraction & Rate Completeness & projection corrected fraction of mergers (and excess close-pairs) within R 200 and with M V < -20.3 are:Completeness & projection corrected fraction of mergers (and excess close-pairs) within R 200 and with M V < -20.3 are: –f m = 0.13 +/- 0.08 in MS1054 (Lum frac = 0.08) –f m = 0.20 +/- 0.07 in CL0152 (Lum frac = 0.11) Merger rate = n cl f m T m -1 (e.g., Lotz et al. 2006)Merger rate = n cl f m T m -1 (e.g., Lotz et al. 2006) –2.5 (± 2.0) Gyr -1 Mpc -2 in MS1054 –7.9 (± 4.8) Gyr -1 Mpc -2 in CL0152 Early type mergers are largely confined to the central ~600 kpc, consistent with the known morphology- density relation.Early type mergers are largely confined to the central ~600 kpc, consistent with the known morphology- density relation. Postman, Bartko et al., in prep

35. October 2006Galaxy Mergers Workshop STScI Brightest Cluster Galaxies CL0152-13 z = 0.837 z = 0.837 E E E E E S0/E S0/E S0/Sa S0/Sa Sb/Sc Sb/Sc MS1054-03 z = 0.831 z = 0.831 CL1226+33 z = 0.888 z = 0.888 CL16h+4304 z = 0.895 z = 0.895CL0848+44 z = 1.265 z = 1.265 CL1252-29 z = 1.235 z = 1.235 CL0910+54 z = 1.10 z = 1.10 CL16h+4321 z = 0.924 z = 0.924 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 (CL1252 and CL0848). 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

36. October 2006Galaxy Mergers Workshop STScI 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 MS1054 where we have an Halpha SFR and a mid-IR SFR, they agree very well We do observe mergers. MS1054 & CL0152 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.

37. October 2006Galaxy Mergers Workshop STScI Quasars and RCS Galaxies If all massive early- types 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 ~3Gyr # of galaxies going through a quasar phase >(50- 100*tau)/3, tau=0.3, #>5-10 for some significant length of time 3 10 tau 100Myr 300Myr

38. October 2006Galaxy Mergers Workshop STScI 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 histogram of z~0 BCG magnitude differences (similarly normalized) along with the location of the Coma cluster BCG. Horizontal dashed lines show the 1 and 2 sigma levels. Different from Gaussian at 98% C.L.

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

40. October 2006Galaxy Mergers Workshop STScI From observed 24mum to SFR Go from observed 12mum to 15mum 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 15mum flux density vs. FIR luminosity (Elbaz et al. 2002) Use LFIR-SFR relation (Kennicutt 1998)

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

42. October 2006Galaxy Mergers Workshop STScI What are the “new” late-type galaxies? Red - ellipticals Blue - spirals Black - mergers Orange - S0s Zooming in on z=0.8

43. October 2006Galaxy Mergers Workshop STScI How are the massive galaxies evolving? Coma z=0.33 z=0.59 z=0.83 Holden et al. 2006

44. October 2006Galaxy Mergers Workshop STScI How are the massive galaxies (not) evolving? Coma z=0.33 z=0.59 z=0.83 Holden et al. 2006

45. October 2006Galaxy Mergers Workshop STScI 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 S0 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

46. October 2006Galaxy Mergers Workshop STScI Butcher-Oemler effect Ellingson et al 2001, see also Andreon & Ettori 2004 B-O effect is detected if one counts within r 200, but the effect disappears if 0.5r 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.