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Title: THE STAR-FORMATION-RATE-DENSITY RELATION AT 0.6 < z < 0.9 AND THE ROLE OF STAR-FORMING GALAXIES

Abstract

We study the star formation rates (SFRs) of galaxies as a function of local galaxy density at 0.6 < z < 0.9. We used a low-dispersion prism in IMACS on the 6.5 m Baade (Magellan I) telescope to obtain spectra and measured redshifts to a precision of {sigma}{sub z}/(1 + z) {approx} 1% for galaxies with z{sub AB} < 23.3 mag. We utilized a stellar mass-limited sample of 977 galaxies above M > 1.8 x 10{sup 10} M{sub sun} (log M/M{sub sun} >10.25) to conduct our main analysis. With three different SFR indicators, (1) Spitzer MIPS 24 {mu}m imaging, (2) spectral energy distribution (SED) fitting, and (3) [O II]{lambda}3727 emission, we find the median specific SFR (SSFR) and SFR to decline from the low-density field to the cores of groups and a rich cluster. For the SED- and [O II]-based SFRs, the decline in SSFR is roughly an order of magnitude while for the MIPS-based SFRs, the decline is a factor of {approx}4. We find approximately the same magnitude of decline in SSFR even after removing the sample of galaxies near the cluster. Galaxies in groups and a cluster at these redshifts therefore have lower star formation (SF) activity thanmore » galaxies in the field, as is the case at z {approx} 0. We investigated whether the decline in SFR with increasing density is caused by a change in the proportion of quiescent and star-forming galaxies (SFGs) or by a decline in the SFRs of SFGs. Using the rest-frame U - V and V - J colors to distinguish quiescent galaxies from SFGs (including both unattenuated blue galaxies and reddened ones), we find that the fraction of quiescent galaxies increases from {approx}32% to 79% from low to high density. In addition, we find the SSFRs of SFGs, selected based on U - V and V - J colors, to decline with increasing density by factors of {approx}5-6 for the SED- and [O II]-based SFRs. The MIPS-based SSFRs for SFGs decline with a shallower slope. The declining SFRs of SFGs with density are paralleled by a decline in the median A{sub V}, providing indirect evidence that the cold gas content that fuels future SF is diminished in higher density environments. The order of magnitude decline in the SSFR-density relation at 0.6 < z < 0.9 is therefore driven by both a combination of declining SFRs of SFGs as well as a changing mix of SFGs and quiescent galaxies.« less

Authors:
; ;  [1];  [2];  [3]
  1. UCO/Lick Observatory, University of California, Santa Cruz, CA 95064 (United States)
  2. Observatories of the Carnegie Institution of Washington, Pasadena, CA 91101 (United States)
  3. Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 AA Leiden (Netherlands)
Publication Date:
OSTI Identifier:
21576518
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 735; Journal Issue: 1; Other Information: DOI: 10.1088/0004-637X/735/1/53; Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; DENSITY; ENERGY SPECTRA; GALACTIC EVOLUTION; GALAXIES; GALAXY CLUSTERS; EVOLUTION; PHYSICAL PROPERTIES; SPECTRA

Citation Formats

Patel, Shannon G., Holden, Bradford P., Illingworth, Garth D., Kelson, Daniel D., and Franx, Marijn, E-mail: patel@ucolick.org. THE STAR-FORMATION-RATE-DENSITY RELATION AT 0.6 < z < 0.9 AND THE ROLE OF STAR-FORMING GALAXIES. United States: N. p., 2011. Web. doi:10.1088/0004-637X/735/1/53.
Patel, Shannon G., Holden, Bradford P., Illingworth, Garth D., Kelson, Daniel D., & Franx, Marijn, E-mail: patel@ucolick.org. THE STAR-FORMATION-RATE-DENSITY RELATION AT 0.6 < z < 0.9 AND THE ROLE OF STAR-FORMING GALAXIES. United States. doi:10.1088/0004-637X/735/1/53.
Patel, Shannon G., Holden, Bradford P., Illingworth, Garth D., Kelson, Daniel D., and Franx, Marijn, E-mail: patel@ucolick.org. Fri . "THE STAR-FORMATION-RATE-DENSITY RELATION AT 0.6 < z < 0.9 AND THE ROLE OF STAR-FORMING GALAXIES". United States. doi:10.1088/0004-637X/735/1/53.
@article{osti_21576518,
title = {THE STAR-FORMATION-RATE-DENSITY RELATION AT 0.6 < z < 0.9 AND THE ROLE OF STAR-FORMING GALAXIES},
author = {Patel, Shannon G. and Holden, Bradford P. and Illingworth, Garth D. and Kelson, Daniel D. and Franx, Marijn, E-mail: patel@ucolick.org},
abstractNote = {We study the star formation rates (SFRs) of galaxies as a function of local galaxy density at 0.6 < z < 0.9. We used a low-dispersion prism in IMACS on the 6.5 m Baade (Magellan I) telescope to obtain spectra and measured redshifts to a precision of {sigma}{sub z}/(1 + z) {approx} 1% for galaxies with z{sub AB} < 23.3 mag. We utilized a stellar mass-limited sample of 977 galaxies above M > 1.8 x 10{sup 10} M{sub sun} (log M/M{sub sun} >10.25) to conduct our main analysis. With three different SFR indicators, (1) Spitzer MIPS 24 {mu}m imaging, (2) spectral energy distribution (SED) fitting, and (3) [O II]{lambda}3727 emission, we find the median specific SFR (SSFR) and SFR to decline from the low-density field to the cores of groups and a rich cluster. For the SED- and [O II]-based SFRs, the decline in SSFR is roughly an order of magnitude while for the MIPS-based SFRs, the decline is a factor of {approx}4. We find approximately the same magnitude of decline in SSFR even after removing the sample of galaxies near the cluster. Galaxies in groups and a cluster at these redshifts therefore have lower star formation (SF) activity than galaxies in the field, as is the case at z {approx} 0. We investigated whether the decline in SFR with increasing density is caused by a change in the proportion of quiescent and star-forming galaxies (SFGs) or by a decline in the SFRs of SFGs. Using the rest-frame U - V and V - J colors to distinguish quiescent galaxies from SFGs (including both unattenuated blue galaxies and reddened ones), we find that the fraction of quiescent galaxies increases from {approx}32% to 79% from low to high density. In addition, we find the SSFRs of SFGs, selected based on U - V and V - J colors, to decline with increasing density by factors of {approx}5-6 for the SED- and [O II]-based SFRs. The MIPS-based SSFRs for SFGs decline with a shallower slope. The declining SFRs of SFGs with density are paralleled by a decline in the median A{sub V}, providing indirect evidence that the cold gas content that fuels future SF is diminished in higher density environments. The order of magnitude decline in the SSFR-density relation at 0.6 < z < 0.9 is therefore driven by both a combination of declining SFRs of SFGs as well as a changing mix of SFGs and quiescent galaxies.},
doi = {10.1088/0004-637X/735/1/53},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 735,
place = {United States},
year = {2011},
month = {7}
}