THE MOST MASSIVE GALAXIES AT 3.0 {<=} z < 4.0 IN THE NEWFIRM MEDIUM-BAND SURVEY: PROPERTIES AND IMPROVED CONSTRAINTS ON THE STELLAR MASS FUNCTION
- Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States)
- Department of Astronomy, Yale University, New Haven, CT 06520-8101 (United States)
- Carnegie Observatories, Pasadena, CA 91101 (United States)
- Sterrewacht Leiden, Leiden University, NL-2300 RA Leiden (Netherlands)
- Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)
- Yale Center for Astronomy and Astrophysics, Departments of Physics and Astronomy, Yale University, New Haven, CT 06520 (United States)
- Department of Physics and Astronomy, University of Kansas, Lawrence, KS 66045 (United States)
- UCO/Lick Observatory, University of California, Santa Cruz, CA 95064 (United States)
We use the optical to mid-infrared coverage of the NEWFIRM Medium-Band Survey (NMBS) to characterize, for the first time, the properties of a mass-complete sample of 14 galaxies at 3.0 {<=} z < 4.0 with M{sub star}>2.5 x 10{sup 11} M{sub sun}, and to derive significantly more accurate measurements of the high-mass end of the stellar mass function (SMF) of galaxies at 3.0 {<=} z < 4.0. The accurate photometric redshifts and well-sampled spectral energy distributions (SEDs) provided by the NMBS combined with the large surveyed area result in significantly reduced contributions from photometric redshift errors and cosmic variance to the total error budget of the SMF. The typical very massive galaxy at 3.0 {<=} z < 4.0 is red and faint in the observer's optical, with a median r-band magnitude of (r{sub tot}) = 26.1, and median rest-frame U - V colors of (U - V) = 1.6. About 60% of the mass-complete sample has optical colors satisfying either the U- or the B-dropout color criteria, although {approx}50% of these galaxies has r>25.5. We find that {approx}30% of the sample has star formation rates (SFRs) from SED modeling consistent with zero, although SFRs of up to {approx}1-18 M{sub sun} yr{sup -1} are also allowed within 1{sigma}. However, >80% of the sample is detected at 24 {mu}m, resulting in total infrared luminosities in the range (0.5-4.0) x 10{sup 13} L{sub sun}. This implies the presence of either dust-enshrouded starburst activity (with SFRs of 600-4300 M{sub sun} yr{sup -1}) and/or highly obscured active galactic nuclei (AGNs). The contribution of galaxies with M{sub star}>2.5 x 10{sup 11} M{sub sun} to the total stellar mass budget at 3.0 {<=} z < 4.0 is {approx}8{sup +13}{sub -3}%. Compared to recent estimates of the stellar mass density in galaxies with M{sub star} {approx} 10{sup 9}-10{sup 11} M{sub sun} at z {approx} 5 and z {approx} 6, we find an evolution by a factor of 2-7 and 3-22 from z {approx} 5 and z {approx} 6, respectively, to z = 3.5. The previously found disagreement at the high-mass end between observed and model-predicted SMFs is now significant at the 3{sigma} level when only random uncertainties are considered. However, systematic uncertainties dominate the total error budget, with errors up to a factor of {approx}8 in the densities at the high-mass end, bringing the observed SMF in marginal agreement with the predicted SMF. Additional systematic uncertainties on the high-mass end could be potentially introduced by either (1) the intense star formation and/or the very common AGN activities as inferred from the MIPS 24 {mu}m detections, and/or (2) contamination by a significant population of massive, old, and dusty galaxies at z {approx} 2.6.
- OSTI ID:
- 21474352
- Journal Information:
- Astrophysical Journal, Vol. 725, Issue 1; Other Information: DOI: 10.1088/0004-637X/725/1/1277; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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