Galaxy Group Masses: Lensing, Dynamics & Xrays

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1 Galaxy Group Masses: Lensing, Dynamics & Xrays Laura Parker Michael Balogh Richard Bower Ray Carlberg Jennifer Connelly Alexis Finoguenov Robbie Henderson Annie Hou Mike Hudson Sean McGee John Mulchaey Krystal Tyler

2 Why do groups matter? Most galaxies in the local universe are in groups (Eke et al. 2004) groups are the characteristic structures in the low-z universe

3 Why do groups matter? Most galaxies in the local universe are in groups (Eke et al. 2004) groups are the characteristic structures in the low-z universe Morphology-Density Relation Galaxy transformation in high density environments When/where/how is this established?

4 Why do groups matter? Most galaxies in the local universe are in groups (Eke et al. 2004) groups are the characteristic structures in the low-z universe Morphology-Density Relation Galaxy transformation in high density environments When/where/how is this established? Can serve as laboratories for the study of galaxy evolution galaxy-galaxy interactions efficient

5 Why are groups hard to study? Groups are a diverse collection of objects Some are cluster-like (BGGs, X-ray emission), many are X-ray faint and lack an obvious BGG Some are very compact, some are very extended g g g g g g g g g g g g g g g g

6 Why are groups hard to study? Groups are a diverse collection of objects Some are cluster-like (BGGs, X-ray emission), many are X-ray faint and lack an obvious BGG Some are very compact, some are very extended Groups are difficult to locate Optical: need very complete spectroscopy typically only a few bright members (low contrast); hard to build large samples Need to go very deep in X-rays (gets worse at high z) g g g g g g g g g g g g g g g g

7 Why are groups hard to study? Groups are a diverse collection of objects Some are cluster-like (BGGs, X-ray emission), many are X-ray faint and lack an obvious BGG Some are very compact, some are very extended Groups are difficult to locate Optical: need very complete spectroscopy typically only a few bright members (low contrast); hard to build large samples Need to go very deep in X-rays (gets worse at high z) g g g g g g g g g g g g g g g g Difficult to compare surveys Optical and X-ray surveys have different sample biasses friends-of-friends algorithms can be tuned to find very different systems (from compact groups to loose associations of galaxies) t

8 Group Masses multiple methods -- diff. strengths and weaknesses Dynamics velocity dispersion from a handful of galaxies equilibrium? (working on detecting departures from Gaussian velocity distributions) Weak Lensing not very massive systems, have to stack the signal from many groups X-ray flux biassed towards massive systems (worse at high z) Do L x -Mass relations evolve?

9 Group Masses multiple methods -- diff. strengths and weaknesses Dynamics velocity dispersion from a handful of galaxies equilibrium? (working on detecting departures from Gaussian velocity distributions) Weak Lensing not very massive systems, have to stack the signal from many groups X-ray flux Will not discuss today... biassed towards massive systems (worse at high z) Do L x -Mass relations evolve?

10 CNOC2 groups ~200 groups between 0.1<z<0.55, selected from the CNOC2 survey (Carlberg et al. 2001)

11 CNOC2 groups ~200 groups between 0.1<z<0.55, selected from the CNOC2 survey (Carlberg et al. 2001) Spectroscopic follow-up at Magellan & VLT

12 CNOC2 groups ~200 groups between 0.1<z<0.55, selected from the CNOC2 survey (Carlberg et al. 2001) Spectroscopic follow-up at Magellan & VLT Observations of 20 groups with HST- ACS Multiwavelength follow-up: GALEX, XMM, Chandra, Spitzer,... Plus more optical imaging

13 Weak Lensing Masses Signal σ 2 Have to stack WL shear from many groups together CNOC2 sample is large and at a favourable redshift range

14 Weak Lensing Masses Signal σ 2 Have to stack WL shear from many groups together CNOC2 sample is large and at a favourable redshift range

15 Weak Lensing Masses Signal σ 2 Have to stack WL shear from many groups together CNOC2 sample is large and at a favourable redshift range + + +

16 γ t σ 2 D LS D S Measure Estimate z of sources based on ~100 CNOC2 groups, imaging from CFHT and KPNO

17 M/L B-band M/L γ t σ 2 D LS D S flat! Measure Estimate z of sources <M/L> B = 185 +/- 28 Radius in units of r 200 Parker et al., 2005 based on ~100 CNOC2 groups, imaging from CFHT and KPNO

18 M/L vs Mass B-band M/L rising M/L with mass transition in M/L at a mass scale of ~10 13 solar masses? groups clusters Can look at the stellar mass as a function of halo mass to see if rise is due to differences in star formation efficiency Parker et al., 2005

19 Dynamical-to-stellar mass versus velocity dispersion M200/M* Solid: from velocity info Open: from weak lensing Stellar mass estimated from Spitzer-IRAC and WHT data (BC03 + Chabrier IMF) Balogh et al., 2007 M/L K increases significantly with mass - big change in star formation efficiency?

20 Extended Xray emission from groups in the CNOC2 fields (Finoguenov et al., submitted) XMM and Chandra data from 2 of 4 CNOC2 fields joint analysis, with careful point source removal How many spectroscopic groups are seen in X- ray? our two fields have very different depths Are mass estimates from X-ray consistent with lensing and dynamical estimates? Are there extended X-ray systems without spectroscopic groups associated?

21 Extended Xray emission from groups in the CNOC2 fields (Finoguenov et al., submitted) XMM and Chandra data from 2 of 4 CNOC2 fields joint analysis, with careful point source removal How many spectroscopic groups are seen in X- ray? our two fields have very different depths Are mass estimates from X-ray consistent with lensing and dynamical estimates? Are there extended X-ray systems without spectroscopic groups associated?

22 Extended Xray emission from groups in the CNOC2 fields (Finoguenov et al., submitted) XMM and Chandra data from 2 of 4 CNOC2 fields joint analysis, with careful point source removal How many spectroscopic groups are seen in X- ray? our two fields have very different depths Are mass estimates from X-ray consistent with lensing and dynamical estimates? Are there extended X-ray systems without spectroscopic groups associated?

23 Where is the extended Xray emission? g g g g g g g g g g g g g g g g g g g g g g g g g g g g g g Wavelet reconstruction of X-ray surface brightness dashed circles show X-ray emission associated with spectroscopic groups solid circle are spectroscopic groups with no Xray emission 50% of spectroscopic groups in deep 14hour X-ray are identified, only 20% in shallower 21hour field

24 Lensing for Optical vs. Xray groups tangential shear Optical Groups

25 Lensing for Optical vs. Xray groups tangential shear Optical Groups X-ray Groups

26 Lensing for Optical vs. Xray groups tangential shear Optical Groups X-ray Groups Sample N groups Mean z Mean shear (<2 ) σ km s 1 Spectroscopic groups in 21h & 14h fields ± ± 137 Spectroscopic groups within X-ray survey ± ± 110 Spectroscopic groups with no X-rays ± ± 326 All X-ray detected systems 49 N(z) ± ± 138 X-ray groups with redshifts ± ± 106

27 Lensing for Optical vs. Xray groups tangential shear Optical Groups X-ray Groups Unfortunately small number statistics! Sample N groups Mean z Mean shear (<2 ) σ km s 1 Spectroscopic groups in 21h & 14h fields ± ± 137 Spectroscopic groups within X-ray survey ± ± 110 Spectroscopic groups with no X-rays ± ± 326 All X-ray detected systems 49 N(z) ± ± 138 X-ray groups with redshifts ± ± 106

28 Predicted number density of groups X-ray detection threshold increases with redshift At z<0.3 we should be able to find halos with <10 13 M At z~0.7 we are only sensitive to things more massive than ~3x10 13 M Solid line is modeling of the z dist n of X-ray systems assuming WMAP5 cosmology and Lx-M relation from Rykoff et al (2008)

29 What should we expect to find? Modeling of the probability of group detection as a function of halo mass (at z=0.4) takes into account: spectroscopic incompleteness X-ray flux limits At the low mass end groups detected only with spectroscopy depends sensitively on completeness of spectroscopy, depth of X-ray observations.

30 Putting it all together Galaxy groups are diverse systems Observed properties vary depending on how they are selected So far the story appears consistent between lensing, velocity dispersions and X-ray detections for the CNOC2 sample Currently working on spectroscopic confirmation of all X-ray selected groups (Connelly, PhD thesis) Number of CNOC2 groups found optically and with X-rays is consistent with the modeling No evidence for evolution in L x -σ relation (though large scatter) compared with z~0 groups