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

By S. Kaviraj, Kevin Schawinski, J. Devriendt, I. Ferreras, S. Khochfar, Seok-Jin Yoon, Sukyoung K. Yi, J. Deharveng, A. Boselli, T. Barlow and 18 more. 2006

288 citations recorded by the source corpus.

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 < z < 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 < z < 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 < 5.5) seen in a significant fraction (~30%) of our observed sample.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/c7067ccf60524d0f978521898a9e6c8176643cc5

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In Astronomy and Astrophysics

1. M. Cappellari
2. C. Conroy
3. P. Hopkins
4. L. Hernquist
5. R. Dav'e
6. R. Somerville
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In Instrumentation

1. M. Cappellari
2. C. Conroy
3. P. Hopkins
4. L. Hernquist
5. T. Naab
6. R. Somerville
7. A. Dekel
8. R. Dav'e

Citations in the corpus

• THE HERSCHEL REFERENCE SURVEY: DUST IN EARLY-TYPE GALAXIES AND ACROSS THE HUBBLE SEQUENCE (2011, background): “Saintonge et al. (2011) have found that galaxies with NUV–r > 5 have very little molecular gas and Kaviraj et al. (2007), Schawinski et al. (2007), and Yi et al. (2005) have showed that quiescent non-star- forming ETGs occupy the region above the boundary NUV–r = 5.4.”
• Galaxy Zoo: a sample of blue early-type galaxies at low redshift (2009, background): “Such events are predicted by current semi-analyticmodels (Khochfar & Burkert 2003; Kaviraj et al. 2006) and so may be a natural trigger for the the time sequence of S07.”
• The role of minor mergers in the recent star formation history of early-type galaxies (2007, background): “Furthermore, the UV remains largely unaffected by the age-metallicity degeneracy (Worthey 1994) that typically plagues optical analyses (Kaviraj et al. 2007a), making it an ideal photometric indicator of RSF.”
• UV Star Formation Rates in the Local Universe (2007, result): “This conclusion is also reached in other studies based onGALEX data (Yi et al. 2005; Kaviraj et al. 2007; Schawinski et al. 2007), where the blue UV-to-optical colors of morphologically selected early-type galaxies are interpreted as signs of recent star formation.”
• GALAXY ZOO: THE FUNDAMENTALLY DIFFERENT CO-EVOLUTION OF SUPERMASSIVE BLACK HOLES AND THEIR EARLY- AND LATE-TYPE HOST GALAXIES (2010, background): “The star formation histories are parameterized as two bursts (e.g., Schawinski et al. 2007; Kaviraj et al. 2007) of varying ages and mass-fractions, fixed solar metallicity, varying dust extinction (0 <E(B − V )< 0.5; Calzetti et al. 2000) and exponential e-folding time (τ = 10, 100, 1000 Myr); all…”
• The Tully-Fisher relations of early-type spiral and S0 galaxies (2010, background): “The evidence for recent (and even ongoing) star formation in local S0s from UV (Kaviraj et al. 2007; Jeong et al. 2009) and mid-infrared (Temi et al. 2009a,b; Shapiro et al. 2010) observations is in fact strong.”
• The Effect of Environment on the Ultraviolet Color-Magnitude Relation of Early-Type Galaxies (2006, methodology): “A full description of our method can be found in Kaviraj et al. (2007).”
• Fitting the integrated spectral energy distributions of galaxies (2010, background): “However, detailed spectroscopic studies (Trager et al. 2000) as well as near-ultraviolet photometry of early-type galaxies (Ferreras and Silk 2000; Yi et al. 2005; Kaviraj et al. 2007) have confirmed the presence of hot stars in early-type galaxies.”
• The correlation of star formation quenching with internal galaxy properties and environment (2008, methodology): “The UV provides a much more sensitive probe of the recent star formation history of a galaxy than optical colours alone, which reflect the highly degenerate effects of stellar populations, metallicity and dust extinction (Yi et al. 2005; Kaviraj et al. 2007).”
• The ATLAS3D project - X. On the origin of the molecular and ionized gas in early-type galaxies (2011, background): “Yi et al. (2005) and Kaviraj et al. (2007) have also shown that at least30% of ETGs have an excess of UV emission, attributable to ongoing residual star formation (over and above that predicted for an old stellar population from the UV-upturn phenomenon; see Yi 2008 for a review).”
• The ATLAS3D project - XIII. Mass and morphology of H I in early-type galaxies as a function of environment (2011, background): “…early insights by Gunn, Stryker & Tinsley (1981) and Rabin (1982), it is now established that a large fraction of ETGs are forming small amounts of stars or have done so in their recent past (e.g. González 1993; Trager et al. 2000; Yi et al. 2005; Kaviraj et al. 2007; Thomas et al. 2010).”
• THE STELLAR MASS CONTENT OF SUBMILLIMETER-SELECTED GALAXIES (2010, background): “…which employ more complex star formation histories, such as short bursts on top of an exponential star formation history (e.g., Borch et al. 2006; Kaviraj et al. 2007; Dye 2008); however, we feel that doing so is not justified because the observational data are insufficient to constrain even…”
• Star Formation in the Milky Way and Nearby Galaxies (2012, background): “Deep GALEX imaging of E/S0 galaxies (e.g., Kaviraj et al. 2007), however, has revealed that approximately 30% of these early-type galaxies exhibit near-ultraviolet emission in excess of what could reasonably arise from an evolved stellar population (e.g., Kaviraj et al. 2007).”