A DIRECT MEASUREMENT OF HIERARCHICAL GROWTH IN GALAXY GROUPS SINCE z {approx} 1
We present the first measurement of the evolution of the galaxy group stellar mass function (GrSMF) to redshift z {approx}> 1 and low masses (M{sub *} > 10{sup 12} M{sub Sun }). Our results are based on early data from the Carnegie-Spitzer-IMACS Survey, utilizing low-resolution spectra and broadband optical/near-IR photometry to measure redshifts for a 3.6 {mu}m selected sample of 37,000 galaxies over a 5.3 deg{sup 2} area to z {approx} 1.2. Employing a standard friends-of-friends algorithm for all galaxies more massive than log M{sub *}/M{sub Sun} = 10.5, we find a total of {approx}4000 groups. Correcting for spectroscopic incompleteness (including slit collisions), we build cumulative stellar mass functions for these groups in redshift bins at z > 0.35, comparing to the z = 0 and z > 0 mass functions from various group and cluster samples. Our derived mass functions match up well with z > 0.35 X-ray-selected clusters, and strong evolution is evident at all masses over the past 8 Gyr. Given the already low level of star formation activity in galaxies at these masses, we therefore attribute most of the observed growth in the GrSMF to group-group and group-galaxy mergers, in accordance with qualitative notions of hierarchical structure formation. Given the factor of 3-10 increase in the number density of groups and clusters with M{sub *} > 10{sup 12} M{sub Sun} since z = 1 and the strong anticorrelation between star formation activity and environmental density during this epoch, this late-time growth in group-sized halos may therefore be an important contributor to the structural and star formation evolution of massive galaxies over the past 8 Gyr.
- OSTI ID:
- 22047919
- Journal Information:
- Astrophysical Journal Letters, Vol. 749, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
Similar Records
THE 10k zCOSMOS: MORPHOLOGICAL TRANSFORMATION OF GALAXIES IN THE GROUP ENVIRONMENT SINCE z {approx}1
MAJOR-MERGER GALAXY PAIRS IN THE COSMOS FIELD-MASS-DEPENDENT MERGER RATE EVOLUTION SINCE z = 1