The SAURON project – XVII. Stellar population analysis of the absorption line strength maps of 48 early-type galaxies

By H. Kuntschner, Eric Emsellem, R. Bacon, M. Cappellari, Roger Davies, P. de Zeeuw, J. Falc'on-Barroso, D. Krajnovi'c, R. McDermid, Reynier Peletier and 4 more. 2010

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We present a stellar population analysis of the absorption line strength maps for 48 early-type galaxies from the SAURON sample. Using the line strength index maps of H beta, Fe5015 and Mgb, measured in the Lick/IDS system and spatially binned to a constant signal-to-noise ratio, together with predictions from up-to-date stellar population models, we estimate the simple stellar population-equivalent (SSP-equivalent) age, metallicity and abundance ratio [alpha/Fe] over a two-dimensional field extending up to approximately one effective radius. A discussion of calibrations and differences between model predictions is given. Maps of SSP-equivalent age, metallicity and abundance ratio [alpha/Fe] are presented for each galaxy. We find a large range of SSP-equivalent ages in our sample, of which similar to 40 per cent of the galaxies show signs of a contribution from a young stellar population. The most extreme cases of post-starburst galaxies, with SSP-equivalent ages of The flattened components with disc-like kinematics previously identified in all fast rotators are shown to be connected to regions of distinct stellar populations. These range from the young, still star-forming circumnuclear discs and rings with increased metallicity preferentially found in intermediate-mass fast rotators, to apparently old structures with extended disc-like kinematics, which are observed to have an increased metallicity and mildly depressed [alpha/Fe] ratio compared to the main body of the galaxy. The slow rotators, often harbouring kinematically decoupled components (KDC) in their central regions, generally show no stellar population signatures over and above the well-known metallicity gradients in early-type galaxies and are largely consistent with old (>= 10 Gyr) stellar populations. Using radially averaged stellar population gradients we find in agreement with Spolaor et al. a mass-metallicity gradient relation where low-mass fast rotators form a sequence of increasing metallicity gradient with increasing mass. For more massive systems (above similar to 3.5 x 10(10) M-circle dot) there is an overall downturn such that metallicity gradients become shallower with increased scatter at a given mass leading to the most massive systems being slow rotators with relatively shallow metallicity gradients. The observed shallower metallicity gradients and increased scatter could be a consequence of the competition between different star formation and assembly scenarios following a general trend of diminishing gas fractions and more equal-mass mergers with increasing mass, leading to the most massive systems being devoid of ordered motion and signs of recent star formation.

Subfields: Astronomy and Astrophysics, Instrumentation

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Citations in the corpus

Structure and Kinematics of Early-Type Galaxies from Integral Field Spectroscopy (2016, methodology): “This fact revealed an increase of metallicity in fast rotators which is specifically associated with the disk component, rather than being uniformly distributed within the spheroidal or bulge component (Kuntschner et al. 2010; Scott et al. 2013a).”
THE NATURE OF LINER-LIKE EMISSION IN RED GALAXIES (2011, background): “At fixed density and ionization parameter, it requires a factor of∼ 3 change in metallicity with radius, which is com- to the electron density, U ≡ q(H0)/(cnH ). parable though somewhat larger than the observed stellar metallicity gradients (Kuntschner et al. 2010).”
The ATLAS3D project - X. On the origin of the molecular and ionized gas in early-type galaxies (2011, background): “…we detect in these galaxies could be a remnant, left over from the progenitors that formed the ETG. Stellar population analyses (e.g. Kuntschner et al. 2006, Kuntschner et al. 2010, McDermid et al., in prep), however, show that the underlyingstellar populations in these galaxies are old (≫ 1Gyr).”
The ATLAS3D project - XIII. Mass and morphology of H I in early-type galaxies as a function of environment (2011, background): “These show that most ETGs host a rotating, kinematically cold component (Krajnović et al. 2008) whose stars are usually younger and more metal-rich than those in the bulge (Kuntschner et al. 2010).”
The ATLAS3D Project – XXX. Star formation histories and stellar population scaling relations of early-type galaxies (2015, methodology): “ETGs are now known to host some degree of young stellar populations (e.g. Trager et al. 2000; Kaviraj et al. 2007; Kuntschner et al. 2010).”
The star formation history of CALIFA galaxies: Radial structures (2013, background): “…al. 2002), and ATLAS3D (Capellari et al. 2011) have taken this approach to spatially resolve the stellar population properties of mainly early type galaxies (Peletier et al. 1997; McDermid et al. 2006; Chilingarian 2009; Kuntschner et al. 2010; see also Ganda et al. 2007 for a few spiral galaxies).”
OVERVIEW OF THE SDSS-IV MaNGA SURVEY: MAPPING NEARBY GALAXIES AT APACHE POINT OBSERVATORY (2014, background): “…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 radii, near 2 Re (Greene et al. 2013).”
The ATLAS3D project – I. A volume-limited sample of 260 nearby early-type galaxies: science goals and selection criteria (2010, background): “Disks in fast rotators have enhanced metallicity, while kinematically distinct cores in slow rotators show no stellar population signatures (Kuntschner et al. 2006, 2010).”
THE NEXT GENERATION VIRGO CLUSTER SURVEY (NGVS). I. INTRODUCTION TO THE SURVEY (2012, background): “…a new perspective on an array of problems related to galaxy formation and evolution, such as the formation of massive gas-poor galaxies (e.g., Kuntschner et al. 2010), the radial migrations of stars within gas-rich galaxies (e.g., Barker et al. 2011), and the multiple populations of dwarf…”
Flux-calibrated stellar population models of Lick absorption-line indices with variable element abundance ratios (2010, methodology): “We confirm the conclusion by Kuntschner et al. (2010) that observations at all galaxy radii are reasonably well covered by the models.”
ON SIZES, KINEMATICS, M/L GRADIENTS, AND LIGHT PROFILES OF MASSIVE COMPACT GALAXIES AT z ∼ 2 (2010, background): “This slope is a factor 1.5 to 2.5 steeper than that of typical massive early-type galaxies today (Rawle, Smith & Lucey 2010; Kuntschner et al. 2010), although those exhibit a large scatter in gradients.”
The ATLAS3D project – XX. Mass–size and mass–σ distributions of early-type galaxies: bulge fraction drives kinematics, mass-to-light ratio, molecular gas fraction and stellar initial mass function (2012, background): “…for the SAURON survey at E uropean Southern O bservatory on A ugust 13, 2014 http://m nras.oxfordjournals.org/ D ow nloaded from The ATLAS3D project – XX. Mass–size 1871 1872 M. Cappellari et al. (de Zeeuw et al. 2002) subset of 48 galaxies was already presented in Kuntschner et al. (2010).”
Re-evaluating old stellar populations (2018, result): “…be inconsistent with the data in indices which are affected by α-elements, but to be consistent with observations in other indices, particularly those 5 [MgFe50]′ = 0.5(0.69 Mg b + Fe5015), added to the original index definitions by Kuntschner et al. (2010). dominated by lines of hydrogen and iron.”
Mechanical AGN feedback: controlling the thermodynamical evolution of elliptical galaxies (2012, result): “It would be interesting to estimate the central Balmer indexes (dependent on the star-formation history) and compare them with the available observations (Kuntschner et al. 2010).”
The ATLAS3D project XV: benchmark for early-type galaxies scaling relations from 260 dynamical models: mass-to-light ratio, dark matter, fundamental plane and mass plane (2012, background): “In this fit, we assume that the distance error are due to the 1σ depth of the Virgo cluster.”
The ATLAS3D project - II. Morphologies, kinemetric features and alignment between photometric and kinematic axes of early-type galaxies (2011, background): “In addition, the stellar population content of RR galaxies often shows distinct and flattened regions of increased metallicity, suggesting a link with regions of ordered rotation (Kuntschner et al. 2006, 2010).”