Spatially resolved spectroscopy of Coma cluster early-type galaxies III. The stellar population gradients ?

By D. Mehlert, D. Thomas, R. Saglia, R. Bender, G. Wegner. 2003

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Based on Paper I of this series (Mehlert et al. 2000), we derive central values and logarithmic gradients for the H, Mg and Fe indices of 35 early-type galaxies in the Coma cluster. We find that pure elliptical galaxies have on average slightly higher velocity dispersions, lower H, and higher metallic line-strengths than galaxies with disks (S0). The latter form two families, one comparable to the ellipticals and a second one with significantly higher H, and weaker metallic lines. Our measured logarithmic gradients within the eective radius areh4Mg b i 0:037,h4hFeii 0:029,h4H i+0:017 and h4i 0:063. The gradients strongly correlate with the gradients of , but only weakly with the central index values and galaxy velocity dispersion. Using stellar population models with variable element abundance ratios from Thomas et al. (2003a) we derive average ages, metallicities and (=Fe) ratios in the center and at the eective radius. We find that the =Fe ratio correlates with velocity dispersion and drives 30% of the Mg- relation, the remaining 70% being caused by metallicity variations. We confirm previous findings that part of the lenticular galaxies in the Coma cluster host very young (2 Gyr) stellar populations, hence must have experienced relatively recent star formation episodes. Again in accordance with previous work we derive negative metallicity gradients ( 0:16 dex per decade) that are significantly flatter than what is expected from gaseous monolithic collapse models, pointing to the importance of mergers in the galaxy formation history. Moreover, the metallicity gradients correlate with the velocity dispersion gradients, confirming empirically earlier suggestions that the metallicity gradient in ellipticals is produced by the local potential well. The gradients in age are negligible, implying that no significant residual star formation has occurred either in the center or in the outer parts of the galaxies, and that the stellar populations at dierent radii must have formed at a common epoch. For the first time we derive the gradients of the =Fe ratio and find them very small on average. Hence, =Fe enhancement is not restricted to galaxy centers but it is a global phenomenon. Our results imply that the Mg- local relation inside a galaxy, unlike the global Mg- relation, must be primarily driven by metallicity variations alone. Finally we note that none of the stellar population parameters or their gradients depend on the density profile of the Coma cluster, even though it spans 3 dex in density.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/e0e6afeae9e05f1002e9c96a57e8d853883f1be3

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Citations in the corpus

BREATHING FIRE: HOW STELLAR FEEDBACK DRIVES RADIAL MIGRATION, RAPID SIZE FLUCTUATIONS, AND POPULATION GRADIENTS IN LOW-MASS GALAXIES (2015, background): “Several studies (for example, Mehlert et al. 2003; Spolaor et al. 2009; Kirby et al. 2011; Schroyen et al. 2013; Vargas et al. 2014; Pilyugin et al. 2015) find an average metallicity gradient of ∆[Fe/H] ∼ −0.4 dex between the galactic center and the effective radius, but with significant (∼ 0.3…”
The star formation history of CALIFA galaxies: Radial structures (2013, background): “Sánchez-Blázquez et al. 2007; Mehlert et al. 2003), or IFU data (eg., Rawler et al. 2010; Kuntschner et al. 2006).”
The SAURON project - VI. Line strength maps of 48 elliptical and lenticular galaxies (2006, background): “For elliptical galaxies, the Hβ gradients have a mean value of 0.000 ± 0.006, i.e. they are consistent with a flat relation (see also Mehlert et al. 2003).”
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 result, which was anticipated in several previous studies of early-type galaxies (Worthey et al. 1992; Jørgensen 1999; Greggio 1997), has been quantified using stellar population models with variable metal abundance ratios (Trager et al. 2000b; Mehlert et al. 2003; Thomas et al. 2005).”
THE UNIVERSAL STELLAR MASS–STELLAR METALLICITY RELATION FOR DWARF GALAXIES (2013, background): “There is also a bias in the sense that galaxies have radial metallicity gradients (e.g., Mehlert et al. 2003; Kirby et al. 2011a).”
The SAURON project - IV. The mass-to-light ratio, the virial mass estimator and the Fundamental Plane of elliptical and lenticular galaxies (2005, result): “(1) The logarithmic slope of our best-fitting relation is in reasonable agreement with the value−0.04 found by Jørgensen et al. (1995) and with the value−0.06 derived by Mehlert et al. (2003) from long slit spectroscopy.”
The STAGES view of red spirals and dusty red galaxies: Mass-dependent quenching of star formation in cluster infall (2008, background): “…claim a strong dependence of early-type ages with environmental density at all masses; while no such evidence is seen in the rich local Coma cluster (Mehlert et al. 2003; Trager, Faber & Dressler 2008), Wolf et al. (2007) see an age–density relation at fixed morphology and low luminosity in the…”
OVERVIEW OF THE SDSS-IV MaNGA SURVEY: MAPPING NEARBY GALAXIES AT APACHE POINT OBSERVATORY (2014, background): “…to date, stellar age gradients are negative but shallow among disk galaxies (Sánchez-Blázquez et al. 2014) and flat among early-types (e.g., Mehlert et al. 2003; Sánchez-Blázquez et al. 2006; Kuntschner et al. 2010), although trends consistent with late-time growth are seen at larger…”
The Tully-Fisher relations of early-type spiral and S0 galaxies (2010, background): “…these bulges are in fact bars, and therefore the products of secular evolution, then these particular bright S0s are unlikely to be the elliptical-like products of major mergers, as has previously been suggested (Poggianti et al. 2001; Mehlert et al. 2003; Bedregal et al. 2008; Barway et al. 2009).”
New calibrations for abundance determinations in H ii regions (2016, background): “…abundance gradients, which in turn hold clues about galaxy evolution (e.g., Searle 1971; Janes 1979; Maciel & Quireza 1999; Harbeck et al. 2001; Andrievsky et al. 2002; Chen et al. 2003; Mehlert et al. 2003; Cioni 2009; Haschke et al. 2012; Boeche et al. 2013, 2014; Pilyugin et al. 2014, 2015).”
The ages and metallicities of galaxies in the local universe (2005, background): “Radial gradients in the properties of stellar populations are known to exist for both bulge-dominated (Henry & Worthey 1999; Saglia et al. 2000; Mehlert et al. 2003) and disc-dominated (Bell & de Jong 2000; MacArthur et al. 2004) galaxies.”
NOAO Fundamental Plane Survey. II. Age and Metallicity along the Red Sequence from Line-Strength Data (2005, background): “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).”
Evidence for TP-AGB Stars in High-Redshift Galaxies, and Their Effect on Deriving Stellar Population Parameters (2006, background): “Metallicity gradients are going to decrease the light-average-determined metallicity slightly, but not to such low values (Mehlert et al. 2003).”
Structure of Disk-dominated Galaxies. II. Color Gradients and Stellar Population Models (2004, result): “Peletier et al. (1999) conclude that the intrinsic color gradients of early-type bulges are caused mainly by metallicity gradients (in agreement with other similar studies; e.g., Mehlert et al. 2003), consistent with the monolithic collapse scenario.”
A census of metals and baryons in stars in the local universe (2007, result): “The relatively large variation in metallicity that we find for bulge-dominated galaxies are, at least qualitatively, consistent with the typical abundance gradients found in the literature (∼ 0.16– 0.2 dex per decade in radius, e.g. Henry & Worthey 1999; Mehlert et al. 2003).”
Environment and self-regulation in galaxy formation (2009, methodology): “…galaxies were explicitly derived, no evidence for a correlation with mass, luminosity or velocity dispersion was found (Jørgensen 1999; Kuntschner 2000; Trager et al. 2000a; Kuntschner et al. 2001; Poggianti et al. 2001a,b; Vazdekis et al. 2001; Terlevich & Forbes 2002; Mehlert et al. 2003).”