DEMONSTRATING DIVERSITY IN STAR-FORMATION HISTORIES WITH THE CSI SURVEY

We present coarse but robust star-formation histories (SFHs) derived from spectrophotometric data of the Carnegie-Spitzer-IMACS Survey, for 22,494 galaxies at with stellar masses of 10 9 M ⊙ to 10 12 M ⊙ . Our study moves beyond “average” SFHs and distribution functions of specific star-formation ra...

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Bibliographic Details
Published in:The Astrophysical journal 2016-12, Vol.833 (2), p.251
Main Authors: Dressler, Alan, Kelson, Daniel D., Abramson, Louis E., Gladders, Michael D., Oemler, Augustus, Poggianti, Bianca M., Mulchaey, John S., Vulcani, Benedetta, Shectman, Stephen A., Williams, Rik J., McCarthy, Patrick J.
Format: Article
Language:English
Subjects:
ABUNDANCE
Astronomical models
Astrophysics
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
COMPARATIVE EVALUATIONS
DISTRIBUTION FUNCTIONS
GALACTIC EVOLUTION
GALAXIES
Polls & surveys
QUENCHING
SPECTROPHOTOMETRY
Star & galaxy formation
Star formation
STARS
Stars & galaxies
Stellar mass
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Summary:We present coarse but robust star-formation histories (SFHs) derived from spectrophotometric data of the Carnegie-Spitzer-IMACS Survey, for 22,494 galaxies at with stellar masses of 10 9 M ⊙ to 10 12 M ⊙ . Our study moves beyond “average” SFHs and distribution functions of specific star-formation rates (sSFRs) to individually measured SFHs for tens of thousands of galaxies. By comparing star-formation rates (SFRs) with timescales of , and 10 8 years, we find a wide diversity of SFHs: “old galaxies” that formed most or all of their stars early, galaxies that formed stars with declining or constant SFRs over a Hubble time, and genuinely “young galaxies” that formed most of their stars since z  = 1. This sequence is one of decreasing stellar mass, but remarkably, each type is found over a mass range of a factor of 10. Conversely, galaxies at any given mass follow a wide range of SFHs, leading us to conclude that (1) halo mass does not uniquely determine SFHs, (2) there is no “typical” evolutionary track, and (3) “abundance matching” has limitations as a tool for inferring physics. Our observations imply that SFHs are set at an early epoch, and that—for most galaxies—the decline and cessation of star formation occurs over a Hubble time, without distinct “quenching” events. SFH diversity is inconsistent with models where galaxy mass, at any given epoch, grows simply along relations between SFR and stellar mass, but is consistent with a two-parameter lognormal form, lending credence to this model from a new and independent perspective.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/833/2/251