Colors, Magnitudes, and Velocity Dispersions in Early-Type Galaxies: Implications for Galaxy Ages and Metallicities

By Mariangela Bernardi, R. Sheth, Robert Nichol, D. Schneider, J. Brinkmann. 2004

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We present an analysis of the color–magnitude–velocity dispersion relation for a sample of 39,320 early-type galaxies within the Sloan Digital Sky Survey. We demonstrate that the color-magnitude relation is entirely a consequence of the fact that both the luminosities and colors of these galaxies are correlated with stellar velocity dispersions. Previous studies of the color-magnitude relation over a range of redshifts suggest that the luminosity of an early-type galaxy is an indicator of its metallicity, whereas residuals in color from the relation are indicators of the luminosity-weighted age of its stars. We show that this, when combined with our finding that velocity dispersion plays a crucial role, has a number of interesting implications. First, galaxies with large velocity dispersions tend to be older (i.e., they scatter redward of the color-magnitude relation). Similarly, galaxies with large dynamical mass estimates also tend to be older. In addition, at fixed luminosity galaxies that are smaller or have larger velocity dispersions or are more massive tend to be older. Second, models in which galaxies with the largest velocity dispersions are also the most metal-poor are difficult to reconcile with our data. However, at fixed velocity dispersion galaxies have a range of ages and metallicities: the older galaxies have smaller metallicities and vice versa. Finally, a plot of velocity dispersion versus luminosity can be used as an age indicator: lines of constant age run parallel to the correlation between velocity dispersion and luminosity.

Subfields: Astronomy and Astrophysics, Global and Planetary Change

View Paper: https://www.semanticscholar.org/paper/1ba5066938552fb5c4e11a00c67379fd710f0521

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Citations in the corpus

Internal and Collective Properties of Galaxies in the Sloan Digital Sky Survey (2006, background): “The fundamental plane and the color-magnitudevelocity dispersion relation for early type galaxies with SDSS have been investigated by Bernardi et al. (2003a, 2005) Very recently Desroches et al. (2006) showed that the fundamental plane projections of elliptical galaxies depend on luminosity using…”
Dissecting the size evolution of elliptical galaxies since z∼ 1: puffing-up versus minor-merging scenarios (2011, background): “…habitually found between the stellar populations and velocity dispersion is evident, with the oldest galaxies being the most massive ones (see e.g. Bernardi et al. 2005; Graves et al. 2009; Napolitano, Romanowsky & Tortora 2010; Rogers et al. 2010), with a larger dark matter content within the…”
Stellar Population Diagnostics of Elliptical Galaxy Formation (2006, result): “…in a cluster with very tight C-M and FP relations such as Coma, a large age spread at all magnitudes was found for a sample of 247 cluster members (Poggianti et al. 2001), and a sizable age-metallicity anticorrelation was also found for a large sample of SDSS galaxies (Bernardi et al. 2005).”
Galaxy Zoo: a sample of blue early-type galaxies at low redshift (2009, background): “…a picture where blue early-type galaxies are systems containing substantial young stellar populations with low and intermediate velocity dispersions almost exclusively belowσ = 200 kms−1, in accordance with the picture of downsizing (Thomas et al. 2005; Nelan et al. 2005; Bernardi et al. 2005).”
The SAURON project – VIII. OASIS/CFHT integral-field spectroscopy of elliptical and lenticular galaxy centres (2006, background): “We perform a robust straight-line fit to the data, the parameters ofwhich are: log t = −3.95 + 2.04 log σ, (3) [Z/H ] = 0.02 + 0.14 log σ, (4) [α/Fe] = −0.45 + 0.26 log σ. (5) As found by many authors (e.g. Carollo, Danziger, & Buson 1993; Trager et al. 2000; Kuntschner et al. 2001; Proctor & Sansom”
Curvature in the scaling relations of early-type galaxies (2008, unknown): “However, g − r color is strongly correlated with σ – large σ implies redder colors (Bernardi et al. 2005), and so M∗/L increases with σ.”
The Effect of Environment on the Ultraviolet Color-Magnitude Relation of Early-Type Galaxies (2006, background): “Furthermore, Bernardi et al. (2005) suggest that the color-magnitude relation is entirely a consequence of the fact that both the luminosities and colors are correlated with sigma, a proxy to mass; that the colorsigma relation is in fact the more fundamental relation.”
Systematic variation of the stellar initial mass function with velocity dispersion in early-type galaxies (2012, methodology): “We select the sample according toσ, because (i) the underlying stellar populations of ETGs are known to correlate strongly with this observable (Bernardi et al. 2005), and (ii) the spectral analysis depends sensitively on velocity dispersion, as a higherσ introduces an effectively lower spectral…”
The Luminosities, Sizes, and Velocity Dispersions of Brightest Cluster Galaxies: Implications for Formation History (2006, background): “Objects which lie redward of the color-magnitude relation are expected to be older (Kodama et al. 1998; Bernardi et al. 2005).”
Determining the Properties and Evolution of Red Galaxies from the Quasar Luminosity Function (2005, methodology): “…et al. 1995; Faber et al. 1995; Worthey 1997) and some studies infer no connection between metallicity and either velocity dspersion or age (e.g. Bernardi et al. 2003c, 2005) or find that the observed scaling of Mg and Hβ line profiles is consistent with more massive ellipticals having formed…”
THE SLOAN LENS ACS SURVEY. IX. COLORS, LENSING, AND STELLAR MASSES OF EARLY-TYPE GALAXIES (2009, methodology): “…relation is due to the narrow effective velocity dispersion range of the SLACS lenses (comparable in width to the ‘constant velocity dispersion’ bins used by other authors, e.g., Bernardi et al. 2005; Graves et al. 2009); a slightly clearer trend is seen in a color-σ diagram (Figure 5).”
Extreme Gas Kinematics in the z = 2.2 Powerful Radio Galaxy MRC 1138–262: Evidence for Efficient Active Galactic Nucleus Feedback in the Early Universe? (2006, background): “…limit to the kinetic energy density in x 8.3.1, 9 ; 1060 ergsMpc 3, we find that on average, eachM early-type galaxy ejects hEejiP6 ; 1059 ergs, roughly the binding energy of an elliptical galaxy with total mass Mtot 4 ; 1011 M (or a galaxy about 1 mag brighter than L r ; Bernardi et al. 2005).”
Ages and metallicities of early-type galaxies in the SDSS: new insight into the physical origin of the colour-magnitude and the Mg2-sigmaV relations (2006, methodology): “This slope is consistent with that of −0.024 obtained previously by Bernardi et al. (2005)4.”
Galaxy Luminosity Functions to z~1 from DEEP2 and COMBO-17: Implications for Red Galaxy Formation (2005, background): “On the other hand, there is at most a weak trend in stellar age with mass or σ along the red sequence (Trager et al. 2001, Terlevich & Forbes 2002, Bernardi et al. 2005), so that stellar ages and metallicities scatter substantially at every point on all three relations.”
Selection bias in dynamically measured supermassive black hole samples: its consequences and the quest for the most fundamental relation (2016, background): “(7) As σ is the controlling parameter in a number of other galaxy scaling relations (Bernardi et al. 2005), our finding thatσ is the most important parameter inMbh scaling relations will serve as a more robust test for the next generation of galaxy-black hole co-evolution models, for a deeper…”
The Link between Submillimetre Galaxies and Luminous Ellipticals: Near-Infrared IFU Spectroscopy of Submillimetre Galaxies (2006, background): “The Faber-Jackson (FJ) relation for local early-type galaxies indicates that this dispersion corresponds to an r-band magnitude of Mr = −22.7 ± 0.5 (Bernardi et al. 2005) or MK = −25.3 ± 0.5 (assuming (r − K) = 2.6, typical for an elliptical galaxy at the present day).”
Galaxy luminosities, stellar masses, sizes, velocity dispersions as a function of morphological type (2009, background): “…has been known for some time that early-type galaxies with large velocity dispersions tend to be older (e.g. Trager et al. 2000; Cattaneo & Bernardi 2003; Bernardi et al. 2005; Thomas et al. 2005; Jimenez et al. 2007), and the virial theorem implies that velocity dispersion and size are correlated.”
Population Synthesis in the Blue. IV. Accurate Model Predictions for Lick Indices and UBV Colors in Single Stellar Populations (2007, result): “…is correct, this result tells us that star formation was more extended in lower mass galaxies, which is in agreement with findings by other authors (e.g., Caldwell et al. 2003, Bernardi et al. 2005, Gallazzi et al. 2006) and seems to lend support to the downsizing scenario (Cowie et al. 1996).”
Evolution and Environment of Early-Type Galaxies (2005, background): “In this respect, many linestrengths behave similarly to color (Bernardi et al. 2003d, 2005).”