The Evolution of X-ray Luminous Groups Tesla Jeltema Carnegie Observatories J. Mulchaey, L. Lubin, C. Fassnacht, P. Rosati, and H. Böhringer

Sample 9 groups selected from the RDCS with 0.2 < z < 0.6. Optical Observations: – Initial spectroscopy with Palomar and Las Campanas – Spectroscopy with Keck and Gemini for 7 groups – Imaging with WFPC2 on HST X-ray Observations: – XMM observations for 6 groups – Additional Chandra and XMM coming Jeltema et al. 2006a; Mulchaey et al. 2006; Jeltema et al. 2006b

X-ray Properties T X = 1.0 – 2.6 keV and L X (r 500 ) = 1.5x10 43 – 15x10 43 ergs/s

Entropy in Groups These groups show excess entropy similar to low-z systems.

Optical Properties  v = km/s from members.

Galaxy Populations Similar to clusters, they have large fractions of early-type galaxies (f e ~0.7) and small fractions of galaxies with significant star formation (f OII ~0.3).

Galaxy Populations Similar to clusters, they have large fractions of early-type galaxies (f e ~0.7) and small fractions of galaxies with significant star formation (f OII ~0.3). field

Central Galaxies At low redshift the X-ray emission is peaked on the brightest elliptical Mulchaey et al. 2003

Central Galaxies At low redshift the X-ray emission is peaked on the brightest elliptical At intermediate redshift … Mulchaey et al. 2003

Central Galaxies At low redshift the X-ray emission is peaked on the brightest elliptical At intermediate redshift … Mulchaey et al. 2003

Central BGGs z = 0.41  = 302 km/s, T = 1.9 keV X-ray and BGG align z = 0.59  = 682 km/s, T = 2.6 keV f e = 0.38, f OII = 0.43 BGG: small secondary

Multiple component BGGs z = 0.23  = 570 km/s, T = 2.6 keV Secondary in group z = 0.23  = 595 km/s, T = 2.4 keV M V,2 - M V,1 = 1.5

Offset BGGs z = 0.38  = 246 km/s, T = 1.7 keV BGG: E, E pair R BGG = 110 kpc z = 0.38  = 417 km/s, T = 1.0 keV String:  = 194 km/s

Other Groups z = 0.46  = 211 km/s f e = 0.43, f OII = 0.67 BGG offset in velocity z = 0.31  = 632 km/s f e = 0.27 Spiral BGG

BGG Formation None of the central galaxies, including those with multiple components, show significant [OII] emission. Consistent with late formation of BGGs through gas-poor mergers. Late BCG formation seen in simulations (De Lucia & Blaizot 2006; Dubinski 1998).

Summary The X-ray properties of these groups are similar to low-z groups. –They appear to follow the scaling relations between L, T, and  and they show excess entropy over self-similar predictions. We do not observe a strong evolution in the galaxy populations from X-ray luminous low-z groups. –They have large fractions of early-type galaxies and small fractions of galaxies with significant star formation. –However, the galaxy populations vary between groups. Unlike low-z, X-ray luminous groups, we do not generally find a single, dominant BGG at the center of these groups. Late BGG formation?

Future Upcoming observations with Chandra and XMM High-resolution spectroscopy and simulations of multiple component BGGs X-ray and optical follow up of a large, X-ray selected sample of groups at low-redshift