Schawinski, K. and Kaviraj, S. and Khochfar, S. and Yoon, S.-J. and Yi, S. K. and Deharveng, J.-M. and Boselli, A. and Barlow, T. and Conrow, T. and Forster, K. and Friedman, P. G. and Martin, D. C. and Morrissey, P. and Neff, S. and Schiminovich, D. and Seibert, M. and Small, T. and Wyder, T. and Bianchi, L. and Donas, J. and Heckman, T. and Lee, Y.-W. and Madore, B. and Milliard, B. and Rich, R. M. and Szalay, A. (2007) The Effect of Environment on the Ultraviolet Color-Magnitude Relation of Early-Type Galaxies. Astrophysical Journal Supplement Series, 173 (2). pp. 512-523. ISSN 0067-0049 http://resolver.caltech.edu/CaltechAUTHORS:20100309-143017549
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We use GALEX near-UV (NUV) photometry of a sample of early-type galaxies selected in the SDSS (Sloan Digital Sky Survey) to study the UV color-magnitude relation (CMR). NUV − r color is an excellent tracer of even small amounts (~1% mass fraction) of recent (≲1 Gyr) star formation, and so the NUV − r CMR allows us to study the effect of environment on the recent star formation history. We analyze a volume-limited sample of 839 visually inspected early-type galaxies in the redshift range 0.05 < z < 0.10 brighter than M_r of –21.5 with any possible emission-line or radio-selected active galactic nuclei (AGNs) removed to avoid contamination. We find that contamination by AGN candidates and late-type interlopers highly bias any study of recent star formation in early-type galaxies and that, after removing those, our lower limit to the fraction of massive early-type galaxies showing signs of recent star formation is roughly 30% ± 3% . This suggests that residual star formation is common even among the present day early-type galaxy population. We find that the fraction of UV-bright early-type galaxies is 25% higher in low-density environments. However, the density effect is clear only in the lowest density bin. The blue galaxy fraction for the subsample of the brightest early-type galaxies, however, shows a very strong density dependence, in the sense that the blue galaxy fraction is lower in a higher density region.
|Additional Information:||© 2007 American Astronomical Society. Print publication: Issue 2 (2007 December); received 2005 November 2; accepted for publication 2005 December 28. Special thanks are given to M. Bernardi, who kindly supplied her early-type galaxy catalog, which provided us with a great insight on our catalog generation. We warmly thank C. Wolf for making the COMBO-17 S11 field image available to us. We would also like to thank E. Gawiser, L. Miller, S. Rawlings, J. Silk, R. Davies, I. Jorgensen, M. Sarzi, J. Magorrian, S. Salim, M. Urry, and K. Kotera for helpful comments and discussions. GALEX (Galaxy Evolution Explorer) is a NASA Small Explorer, launched in 2003 April. We gratefully acknowledge NASA’s support for construction, operation, and science analysis for the GALEX mission, developed in cooperation with the Centre National d’Etudes Spatiales of France and the Korean Ministry of Science and Technology. This work was supported by grant R01-2006-000-10716-0 from the Basic Research Program of the KOSEF and Yonsei University Research Fund to the corresponding author (S. K. Yi).|
|Group:||Space Radiation Laboratory|
|Subject Keywords:||galaxies: elliptical and lenticular, cD; galaxies: evolution; galaxies: formation; galaxies: fundamental parameters|
|Official Citation:||The Effect of Environment on the Ultraviolet Color-Magnitude Relation of Early-Type Galaxies K. Schawinski, S. Kaviraj, S. Khochfar, S.-J. Yoon, S. K. Yi, J.-M. Deharveng, A. Boselli, T. Barlow, T. Conrow, K. Forster, P. G. Friedman, D. C. Martin, P. Morrissey, S. Neff, D. Schiminovich, M. Seibert, T. Small, T. Wyder, L. Bianchi, J. Donas, T. Heckman, Y.-W. Lee, B. Madore, B. Milliard, R. M. Rich, and A. Szalay 2007 ApJS 173 512-523 doi: 10.1086/516631|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Jason Perez|
|Deposited On:||10 Mar 2010 18:16|
|Last Modified:||04 Mar 2013 18:07|
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