On the dependence of spectroscopic indices of early-type galaxies on age, metallicity and velocity dispersion

By H. Kuntschner, J. Lucey, Russell J. Smith, M. Hudson, R. L. D. U. O. Durham, U. D. Chile, U. Waterloo. 2000

137 citations recorded by the source corpus.

We investigate the Mg–σ and Fe–σ relations in a sample of 72 early-type galaxies drawn mostly from cluster and group environments using a homogeneous data set which is well calibrated on to the Lick/IDS system. The small intrinsic scatter in Mg at a given σ gives upper limits on the spread in age and metallicity of 49 and 32 per cent respectively, if the spread is attributed to one quantity only, and if the variations in age and metallicity are uncorrelated. The age/metallicity distribution as inferred from the Hβ versus Fe diagnostic diagram reinforces this conclusion, as we find mostly galaxies with large luminosity-weighted ages spanning a range in metallicity. Using Monte Carlo simulations, we show that the galaxy distribution in the Hβ versus Fe plane cannot be reproduced by a model in which galaxy age is the only parameter driving the index–σ relation. In our sample we do not find significant evidence for an anticorrelation of ages and metallicities which would keep the index–σ relations tight while hiding a large spread in age and metallicity. As a result of correlated errors in the age–metallicity plane, a mild age–metallicity anticorrelation cannot be completely ruled out by the current data. Correcting the line-strength indices for non-solar abundance ratios, following the recent paper by Trager et al., leads to higher mean metallicity and slightly younger age estimates while preserving the metallicity sequence. The [Mg/Fe] ratio is mildly correlated with the central velocity dispersion, and ranges from [Mg/Fe]=0.05 to 0.3 for galaxies with σ>100 km s1. Under the assumption that there is no age gradient along the index–σ relations, the abundance-ratio-corrected Mg–σ,Fe–σ and Hβ–σ relations give consistent estimates of Δ[M/H]/Δ log σ0.9±0.1. The slope of the Hβ–σ relation limits a potential age trend as a function of σ to 2–3 Gyr along the sequence.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/940817773dc088698c0be34b394ce95819d85c4e

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Citations in the corpus

Spatially resolved spectroscopy of Coma cluster early-type galaxies III. The stellar population gradients ? (2003, background): “Note that, except for a very small fraction of young field elliptical galaxies (see also Kuntschner et al. 2001), also Thomas et al. (2002) could not find any significant differences between earlytype galaxies in low and high density environments with respect to their stellar parameters.”
Early-Type Galaxies in the Sloan Digital Sky Survey. I. The Sample (2003, background): “…galaxies points to early formation (e.g., Worthey 1994; Bressan, Chiosi, & Fagotto 1994; Vazdekis et al. 1996; Tantalo, Chiosi, & Bressan 1998); certainly their stellar populations appear old (e.g., Bernardi et al. 1998; Colless et al. 1999; Trager et al. 2000a, 2000b; Kuntschner et al. 2001).”
Measuring Distances and Probing the Unresolved Stellar Populations of Galaxies Using Infrared Surface Brightness Fluctuations (2002, methodology): “It is unnecessary to adjust the measurements to a common system since Kuntschner et al. (2001) found that H does not change significantly with radius from the galaxy center.”
The dependence of star formation history and internal structure on stellar mass for 105 low‐redshift galaxies (2002, background): “…the absorption line strengths of early-type galaxies vary systematically with their velocity dispersions, there is much debate as to whether this reflects trends in stellar age, in metallicity or in the relative abundance of different heavy elements (e.g. Trager et al 1998; Kuntschner et al 2001).”
Stellar Population Diagnostics of Elliptical Galaxy Formation (2006, methodology): “Kuntschner et al. (2001) investigated the effect by means of Monte Carlo simulations, and indeed showed that much of the apparent age-metallicity anticorrelation is a mere result of the tight correlation of their errors.”
Evolutionary synthesis of galaxies at high spectral resolution with the code PEGASE-HR. Metallicity and age tracers (2004, background): “But in practice the tests are difficult and give ambiguous results, partly because of the contamination by nebular emission, in particular for Hα and Hβ (González 1993; Worthey & Ottaviani 1997; Kuntschner et al. 2001).”
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, background): “Similar interpretations have been proposed for the relation between Mg2 index strength and central velocity dispersion σV , which is generally thought to arise from a combination of age and metallicity variations (Colless et al. 1999; Trager et al. 2000a; Kuntschner et al. 2001).”
Colors, Magnitudes, and Velocity Dispersions in Early-Type Galaxies: Implications for Galaxy Ages and Metallicities (2004, background): “The tightness of the correlation between Mg2 and σ (e.g. Bernardi et al. 1998; Colless et al. 1999), is thought to be a consequence of variations in age and metallicity which conspire to keep the observed correlation tight (e.g. Kuntschner et al. 2001).”
Determining the Properties and Evolution of Red Galaxies from the Quasar Luminosity Function (2005, background): “The slopes from the observations of Kuntschner et al. (2001) and Trager et al. (2000) are determined by fitting in Nelan et al. (2005).”
The SAURON project – VIII. OASIS/CFHT integral-field spectroscopy of elliptical and lenticular galaxy centres (2006, background): “Moreover, theseand comparable ground-based studies looking at central properties (e.g. Carollo & Danziger 1994b; Trager et al. 2000; Thomas et al. 2005) are restricted to either aperture measurements or long-slit profiles, making the association between population changes and other structural variat”
Environment and self-regulation in galaxy formation (2009, background): “This leads to tight correlations between the errors of these parameters, which hampers their determination (Trager et al. 2000a; Kuntschner et al. 2001; T05).”
The ages and metallicities of galaxies in the local universe (2005, background): “…lines and agesensitive Balmer lines can break the age–metallicity degeneracy, but only in a relative way: the derived ages and metallicities appear to depend strongly on the specific choice of metal indices (e.g. Kuntschner et al. 2001; Eisenstein et al. 2003; Thomas, Maraston & Korn 2004).”
The SAURON project – XVII. Stellar population analysis of the absorption line strength maps of 48 early-type galaxies (2010, background): “Error ellipses are drawn for each galaxy and demonstrate graphically the well known error correlation between [Z/H] and Age (e.g., Trager et al. 2000; Kuntschner et al. 2001).”
Evolution and Environment of Early-Type Galaxies (2005, background): “In constrast, Thomas et al. (2005) found that objects in less dense regions are slightly younger and metal rich, but they find no α-enhancement effect (see also Kuntschner et al. 2001).”
NOAO Fundamental Plane Survey. II. Age and Metallicity along the Red Sequence from Line-Strength Data (2005, methodology): “Especially well studied are the linestrength centered on the magnesium triplet of absorption lines near λ5175 with σ (Bender et al. 1993; Wegner et al. 1999; Kuntschner et al. 2001; Bernardi et al 2003; Davies et al. 1987), as well as iron lines and the Balmer series (e.g., Mehlert et al. 2003).”
Near-infrared line-strengths in elliptical galaxies: evidence for initial mass function variations? (2002, methodology): “Using Monte-Carlo simulations (following a procedure similar to that of Kuntschner et al. 2001), we have checked that this relation is not driven by a combined effect of Poisson noise and non-orthogonal diagnostic diagrams, thus concluding that Es can indeed be explained using µ–[Fe/H]–log σ0…”
The many manifestations of downsizing: hierarchical galaxy formation models confront observations (2009, background): “Several studies have since confirmed this observational trend (Carollo, Danziger & Buson 1993; Davies, Sadler & Peletier 1993; Trager et al. 2000b; Kuntschner et al. 2001), and a standard interpretation has become that of shorter formation time-scales in more luminous/massive galaxies (Matteucci…”