The Effect of Environment on the Ultraviolet Color-Magnitude Relation of Early-Type Galaxies

By Kevin Schawinski, S. Kaviraj, S. Khochfar, Suk-Jin Yoon, Sukyoung K. Yi, J. Deharveng, A. Boselli, T. Barlow, T. Conrow, K. Forster and 16 more. 2006

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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 Mr 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.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/97d5c8a5a41db9ca8d9d5273e64e5dc3e4fb916f

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Citations in the corpus

Physical properties and environments of nearby galaxies (2009, background): “Schawinski et al. (2007) further found that early-types with recent star formation were more prevalent in low density environments, even after controlling for the fact that lower-mass (massive) galaxies are found preferentially in underdense (dense) regions.”
The correlation of star formation quenching with internal galaxy properties and environment (2008, background): “There is also mounting observational evidence that AGN are associated with the quenching of star formation (Schawinski et al. 2006; Salim et al. 2007, hereafter S07; Schawinski et al. 2007b).”
BAT AGN Spectroscopic Survey. I. Spectral Measurements, Derived Quantities, and AGN Demographics (2017, methodology): “For the [N II]λ6583 diagnostic, we further separate the star forming (HII) galaxies and composite galaxies, and separate AGN into LINERs and Seyferts (following Schawinski et al. 2007b).”
Environment and self-regulation in galaxy formation (2009, methodology): “A detailed BPT analysis of the present sample is presented in Schawinski et al. (2007b), and we refer the reader to this paper for further details.”
The green valley is a red herring: Galaxy Zoo reveals two evolutionary pathways towards quenching of star formation in early-and late-type galaxies (2014, methodology): “This is why it has been suggested previously that black hole accretion is correlated with a decline in sSFR (and therefore green colours; e.g. Schawinski et al. 2007b; Nandra et al. 2007; Wild et al. 2007; Silverman et al. 2008).”
The ATLAS3D Project – XXX. Star formation histories and stellar population scaling relations of early-type galaxies (2015, background): “Previously considered as important for ETGs in general (Thomas et al. 2005; Schawinski et al. 2007), the interplay of mass and environment may also play a role (Thomas et al. 2010).”
IMPROVED AND QUALITY-ASSESSED EMISSION AND ABSORPTION LINE MEASUREMENTS IN SLOAN DIGITAL SKY SURVEY GALAXIES (2011, methodology): “Baldwin, Phillips & Terlevich (1981) first proposed the use of diagnostic diagrams, which have subsequently been used and refined by numerous research groups (Veilleux & Osterbrock 1987; Kewley et al. 2001; Kauffmann et al. 2003; Schawinski et al. 2007).”
Galaxy Zoo: a sample of blue early-type galaxies at low redshift (2009, methodology): “We measure the local environment using the measure of Schawinski et al. (2007a) and Yoon et al. (2008) and find, at a given velocity dispersion, a statistically significant differenc between red and blue early-type galaxies.”
Galaxy Zoo: the dependence of morphology and colour on environment (2008, methodology): “Studies have thus far been limited to samples containing several thousand galaxies (Nakamura et al.2004; Fukugita et al. 2007), although the MOSES project (Morphologically Selected Ellipticals in SDSS; Schawinski et al. 2007)visually inspected nearly 50000 galaxies in order to identify a cleansample”
THE HERSCHEL REFERENCE SURVEY: DUST IN EARLY-TYPE GALAXIES AND ACROSS THE HUBBLE SEQUENCE (2011, methodology): “In this case (including sources not detected with GALEX but excluding NGC4486 and NGC4552), ∼ 40% of our early-type sample is in the RSF group, including 30% of our ellipticals.”
Galaxy Zoo: Disentangling the Environmental Dependence of Morphology and Colour ⋆ (2008, background): “This also explains the weak colour-environment correlation observed by Schawinski et al. (2007), whose sample of early-types is brighter and smaller than ours.”
Formation of Early-Type Galaxies from Cosmological Initial Conditions (2005, background): “However, it is not unusual for field ellipticals (E+A phenomenon) to actually show residual star formation (Blake et al. 2004; Schawinski et al. 2007).”
STELLAR MASSES AND STAR FORMATION RATES FOR 1 M GALAXIES FROM SDSS+WISE (2015, background): “We have also indicated the intermediate region often called the green valley, which has been argued to contain galaxies that are transitioning from blue to red (e.g., Schawinski et al. 2007).”
Galaxy Zoo: the properties of merging galaxies in the nearby Universe – local environments, colours, masses, star formation rates and AGN activity (2009, methodology): “To parametrise environment, we employ the method of Schawinski et al. (2007b) that takes advantage of all the spectroscopic-redshift recordings in the SDSS DR6 to obtain the dimensionless number ρg (the adaptive Gaussian environment parameter) for each galaxy in our catalogue.”
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.”