Star Formation Histories of Early-Type Galaxies. I. Higher Order Balmer Lines as Age Indicators

By N. Caldwell, J. Rose, Kristi D. Concannon. 2003

147 citations recorded by the source corpus.

We have obtained blue integrated spectra of 175 nearby early-type galaxies, covering a wide range in galaxy velocity dispersion and emphasizing those with σ < 100 km s-1. Galaxies have been observed both in the Virgo Cluster and in lower density environments. The main goals are the evaluation of higher order Balmer lines as age indicators and differences in stellar populations as a function of mass, environment, and morphology. In this first paper, our emphasis is on presenting the methods used to characterize the behavior of the Balmer lines through evolutionary population synthesis models. Lower σ galaxies exhibit a substantially greater intrinsic scatter, in a variety of line-strength indicators, than do higher σ galaxies, with the large intrinsic scatter setting in below a σ of 100 km s-1. Moreover, a greater contrast in scatter is present in the Balmer lines than in the lines of metal features. Evolutionary synthesis modeling of the observed spectral indexes indicates that the strong Balmer lines found primarily among the low-σ galaxies are caused by young age, rather than by low metallicity. Thus we find a trend between the population age and the central velocity dispersion, such that low-σ galaxies have younger luminosity-weighted mean ages. We have repeated this analysis using several different Balmer lines and find consistent results from one spectral indicator to another.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/90c69b154e0b3d059a4f2c1571ab72e5032c7ac8

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Citations in the corpus

Observational evidence for AGN feedback in early-type galaxies (2007, background): “Today’s early-type galaxies in particular show a clear correlation between mass and age (Caldwell et al. 2003; Thomas et al. 2005; Nelan et al. 2005; Bernardi et al. 2006; Jimenez et al. 2006).”
THE 2MASS REDSHIFT SURVEY—DESCRIPTION AND DATA RELEASE (2011, unknown): “C...0000C Colless et al. (2003) 2003AJ....125.2891C Caldwell et al. (2003) 2003AJ....126.1245T Tanvuia et al. (2003) 2003AJ....126.2152R Rines et al. (2003) 2003AJ....126.2268W Wegner et al. (2003) 2003A&A...399...51G Garrido et al. (2003) 2003A&A...399..511M Morganti et al. (2003)…”
The SAURON project - VI. Line strength maps of 48 elliptical and lenticular galaxies (2006, methodology): “For Fe5015, which was only observed by Caldwell et al. (2003), an offset of approximately 0.01 mag at intermediate velocity dispersions is visible, in the sense that our data have the larger values.”
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, result): “Our results also confirm the trend of increasing age with increasing velocity dispersion (e.g. Caldwell et al. 2003; Thomas et al. 2005; Nelan et al. 2005).”
NOAO Fundamental Plane Survey. II. Age and Metallicity along the Red Sequence from Line-Strength Data (2005, background): “A better predictor of emission at Hβ is the emission at Hα (Caldwell et al. 2003).”
Determining the Properties and Evolution of Red Galaxies from the Quasar Luminosity Function (2005, methodology): “Our prediction of the age-velocity dispersion relation includes the observed steepening of the relation at low velocity dispersions (e.g., Caldwell et al. 2003; Nelan et al. 2005),an effect not accounted for in fitting a single power law, which is why the power law fits extrapolated to lowσ tend to…”
UV-Optical Colors as Probes of Early-Type Galaxy Evolution (2006, background): “The strengths of age-sensitive spectral indices observed in some early-type systems require luminosity-weighted ages which are consistent with the presence of at least some recent star formation (RSF) in these systems (e.g. Caldwell et al. 2003; Trager et al. 2000a,b; Proctor and Sansom 2002).”
Stellar populations of early-type galaxies in different environments - II. Ages and metallicities (2006, background): “Caldwell et al. (2003) also found younger ages for lower σ galaxies in a sample of Virgo galaxies and galaxies in lower environments.”
Spatially resolved spectroscopy of early-type galaxies over a range in mass (2007, background): “Contrary to what has been reported in many studies (e.g. Caldwell et al. 2003; Nelan et al. 2005; Bernardi et al. 2006; Sánchez-Blázquez et al. 2006b) we do not find any relation between these two parameters.”
Virgo Cluster Early-Type Dwarf Galaxies with the Sloan Digital Sky Survey. II. Early-Type Dwarfs with Central Star Formation (2006, unknown): “…et al. (1992); Binggeli et al. (1993); Young & Currie (1995); Drinkwater et al. (1996); Grogin et al. (1998); Falco et al. (1999); Gavazzi et al. (2000); van Driel et al. (2000); Conselice et al. (2001); Simien & Prugniel (2002); Caldwell et al. (2003); Geha et al. (2003); Gavazzi et al. (2004).”
DISSIPATION AND EXTRA LIGHT IN GALACTIC NUCLEI. IV. EVOLUTION IN THE SCALING RELATIONS OF SPHEROIDS (2008, background): “The stellar population age is quite old, 10.5 Gyr (perhaps even up to∼ 13 Gyr, depending on the indicator used; Caldwell et al. 2003), implying a time of last significant star formationz & 2.”
Population Synthesis in the Blue. IV. Accurate Model Predictions for Lick Indices and UBV Colors in Single Stellar Populations (2007, background): “…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).”