UV‐Optical Colors as Probes of Early‐Type Galaxy Evolution | Zendy

Sugata Kaviraj | Zendy; Kevin Schawinski | Zendy; Julien Devriendt | Zendy; Ignacio Ferreras | Zendy; Sadegh Khochfar | Zendy; Sung-Chul Yoon | Zendy; Sukyoung K. Yi | Zendy; J. M. Deharveng | Zendy; A. Boselli | Zendy; Tom A. Barlow | Zendy; T. Conrow | Zendy; Karl Förster | Zendy; Peter G. Friedman | Zendy; D. Christopher Martin | Zendy; Patrick Morrissey | Zendy; Susan G. Neff | Zendy; David Schiminovich | Zendy; Mark Seibert | Zendy; Todd Small | Zendy; Ted Wyder | Zendy; L. Bianchi | Zendy; J. Donas | Zendy; Timothy M. Heckman | Zendy; YoungWook Lee | Zendy; B. Madore | Zendy; B. Milliard | Zendy; R. Michael Rich | Zendy; Alexander S. Szalay | Zendy

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UV‐Optical Colors as Probes of Early‐Type Galaxy Evolution

Author(s) -

Sugata Kaviraj,

Kevin Schawinski,

Julien Devriendt,

Ignacio Ferreras,

Sadegh Khochfar,

Sung-Chul Yoon,

Sukyoung K. Yi,

J. M. Deharveng,

A. Boselli,

Tom A. Barlow,

T. Conrow,

Karl Förster,

Peter G. Friedman,

D. Christopher Martin,

Patrick Morrissey,

Susan G. Neff,

David Schiminovich,

Mark Seibert,

Todd Small,

Ted Wyder,

L. Bianchi,

J. Donas,

Timothy M. Heckman,

YoungWook Lee,

B. Madore,

B. Milliard,

R. Michael Rich,

Alexander S. Szalay

Publication year - 2007

Publication title -

the astrophysical journal supplement series

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 3.546

H-Index - 277

eISSN - 1538-4365

pISSN - 0067-0049

DOI - 10.1086/516633

Subject(s) - physics , astrophysics , galaxy , redshift , star formation , photometry (optics) , stellar population , stellar mass , astronomy , stars , galaxy formation and evolution

We have studied ~2100 early-type galaxies in the SDSS DR3 which have been detected by the GALEX Medium Imaging Survey (MIS), in the redshift range 0 andlt; z andlt; 0.11. Combining GALEX UV photometry with corollary optical data from the SDSS, we find that, at a 95% confidence level, at least ~30% of galaxies in this sample have UV to optical colors consistent with some recent star formation within the last Gyr. In particular, galaxies with an NUV − r color less than 5.5 are very likely to have experienced such recent star formation, taking into account the possibility of a contribution to NUV flux from the UV upturn phenomenon. We find quantitative agreement between the observations and the predictions of a semianalytical ΛCDM hierarchical merger model and deduce that early-type galaxies in the redshift range 0 andlt; z andlt; 0.11 have ~1%-3% of their stellar mass in stars less than 1 Gyr old. The average age of this recently formed population is ~300-500 Myr. We also find that "monolithically" evolving galaxies, where recent star formation can be driven solely by recycled gas from stellar mass loss, cannot exhibit the blue colors (NUV − r andlt; 5.5) seen in a significant fraction (~30%) of our observed sample.