NOAO Fundamental Plane Survey. II. Age and Metallicity along the Red Sequence from Line-Strength Data

By Jenica E. Nelan, Russell J. Smith, M. Hudson, G. Wegner, J. Lucey, S. Moore, S. Quinney, N. Suntzeff. 2005

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We present spectroscopic line-strength data for 4097 red-sequence galaxies in 93 low-redshift galaxy clusters and use these to investigate variations in average stellar populations as a function of galaxy mass. Our analysis includes an improved treatment of nebular emission contamination, which affects ~10% of the sample galaxies. Using the stellar population models of D. Thomas and collaborators, we simultaneously fit 12 observed line-strength-σ relations in terms of common underlying trends of age, [Z/H] (total metallicity), and [α/Fe] (α-element enhancement). We find that the observed line-strength-σ relations can be explained only if higher mass red-sequence galaxies are, on average, older, more metal-rich, and more α-enhanced than lower mass galaxies. Quantitatively, the scaling relations are age ∝ σ0.59±0.13, Z/H ∝ σ0.53±0.08, and α/Fe ∝ σ0.31±0.06, where the errors reflect the range obtained using different subsets of indices. Our conclusions are not strongly dependent on which Balmer lines are used as age indicators. The derived age-σ relation is such that if the largest (σ ~ 400 km s-1) galaxies formed their stars ~13 Gyr ago, then the mean age of low-mass (σ ~ 50 km s-1) objects is only ~4 Gyr. The data also suggest a large spread in age at the low-mass end of the red sequence, with 68% of the galaxies having ages between 2 and 8 Gyr. We conclude that although the stars in giant red galaxies in clusters formed early, most of the galaxies at the faint end joined the red sequence only at recent epochs. This "downsizing" trend is in good qualitative agreement with observations of the red sequence at higher redshifts but is not predicted by semianalytic models of galaxy formation.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/122b8675496a1d4479f35a9f8c834adbd20c96c8

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Citations in the corpus

The 2df SDSS LRG and QSO survey: evolution of the luminosity function of luminous red galaxies to z= 0.6 (2006, background): “This fraction appears to increase with redshift (Le Borgne et al. 2006; Roseboom et al., in preparation) and decrease with mass (Caldwell, Rose & Concannon 2003; Nelan et al. 2005; Clemens et al. 2006).”
zCOSMOS – 10k-bright spectroscopic sample - The bimodality in the galaxy stellar mass function: exploring its evolution with redshift (2009, background): “…of galaxy stellar populations, according to which less massive galaxies contain younger stars, which is also applicable to similar spectral/morphological types both among ETGs (Nelan et al. 2005; Thomas et al. 2005; Graves et al. 2007; Fontana et al. 2004) and LTGs (Noeske et al. 2007a,b).”
The formation history of elliptical galaxies (2005, result): “We have shown – and this is perhaps the most important result of our study – that in our model the most massive elliptical galaxies have the oldest and most metal rich stellar populations, in agreement with observational results (see for example Nelan et al. 2005).”
The many manifestations of downsizing: hierarchical galaxy formation models confront observations (2009, background): “…indexes or on a detailed fit of the full highresolution spectrum, have confirmed a weak trend between stellar mass and age both in clusters (Nelan et al. 2005; Thomas et al. 2005, though see Trager, Faber & Dressler 2008) and in the field (Trager et al. 2000a; Heavens et al. 2004; Gallazzi…”
Flux-calibrated stellar population models of Lick absorption-line indices with variable element abundance ratios (2010, background): “…instead, discloses stellar population properties that act as fossil record and can be used to derive ages, formation epochs, star formation histories, and element abundances (e.g. Trager et al. 2000a; Kuntschner 2000; Thomas et al. 2005; Nelan et al. 2005; Bernardi et al. 2006; Thomas et al. 2010).”
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).”
Natural downsizing in hierarchical galaxy formation (2006, methodology): “Using observed line indices and abundance ratios, ADS has been detcted in elliptical galaxies (Thomas et al. 2005; Nelan et al. 2005), and in a large sample of galaxies from the Sloan Digital Sky Survey (Heavens et al. 2004; Jimenez et al. 2005).”
Evolution and Environment of Early-Type Galaxies (2005, result): “On the other hand, our derived correlations in the high-density regions in are slightly better agreement with those of the NOAO-FP survey (Nelan et al. 2005) of clusters (dashed curves).”
THE GEMINI CLUSTER ASTROPHYSICS SPECTROSCOPIC SURVEY (GCLASS): THE ROLE OF ENVIRONMENT AND SELF-REGULATION IN GALAXY EVOLUTION AT z ∼ 1 (2011, background): “In general, the converse is seen (e.g., Thomas et al. 2005; Nelan et al. 2005; Gallazzi et al. 2005; van Dokkum & van der Marel 2007; Thomas et al. 2010), which would seem to argue against environmental quenching dominating at late times.”
Spatially resolved spectroscopy of early-type galaxies over a range in mass (2007, methodology): “In the figure we also show the relation found by Nelan et al. (2005).”
Deriving Physical Properties from Broadband Photometry with Prospector: Description of the Model and a Demonstration of its Accuracy Using 129 Galaxies in the Local Universe (2016, background): “To measure Hδ, fixed wavelength indices are defined over which to measure the continuum and the strength of the Hδ feature (e.g., Worthey et al. 1994; Worthey & Ottaviani 1997; Nelan 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, 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).”
GALAXY ZOO: THE FUNDAMENTALLY DIFFERENT CO-EVOLUTION OF SUPERMASSIVE BLACK HOLES AND THEIR EARLY- AND LATE-TYPE HOST GALAXIES (2010, background): “…studies” of local galaxies, and by probing ongoing star formation at increasing redshifts (Cowie et al. 1996; Heavens et al. 2004; Thomas et al. 2005; Nelan et al. 2005; Bernardi et al. 2006; Bundy et al. 2006; Jimenez et al. 2007; Pérez-González et al. 2008; Collins et al. 2009; Thomas et al.…”
Observational evidence for AGN feedback in early-type galaxies (2007, background): “…redshift on very short timescales as suggested by the stellar population properties of nearbysamples (e.g. Trager et al. 2000; Thomas et al. 2005; Nelan et al.2005; Bernardi et al. 2006; Jimenez et al. 2006) as well as the redshift evolution of luminosity and mass functions of massive galaxies…”
Stellar Population Diagnostics of Elliptical Galaxy Formation (2006, background): “For example, if age were to increase along the FP from 5.5 Gyr to 13 Gyr (at z = 0, and for σ = 100 and 320 km s−1, respectively, see Nelan et al. 2005), then at a lookback time of 4 Gyr (z ∼ 0.4) the younger population would have brightened by ∆MB ∼ 1.33 mag, and the older one only by ∼ 0.46 mag…”
THE TWO PHASES OF GALAXY FORMATION (2010, background): “But we know that this is not true observationally (Nelan et al. 2005), giant ellipticals are older - not younger - than lower mass systems (see e.g. Thomas et al. 2005).”
The Origin of Dwarf Ellipticals in the Virgo Cluster (2008, background): “Our results are also consistent with the analysis of Nelan et al. (2005) on 93 nearby clusters based on the age-σ relation which indicates that the quiescent dwarf galaxy population only recently joined the red sequence.”
X-Ray Thermal Coronae of Galaxies in Hot Clusters: Ubiquity of Embedded Mini-Cooling Cores (2006, background): “As SC 1327-312 is 1.4 Mpc from the gas core of A3558 in the plane of sky, the “sloshing” of A3358’s gas core must have proceeded for over 1 Gyr.”
Determining the Properties and Evolution of Red Galaxies from the Quasar Luminosity Function (2005, methodology): “Observations ofthe mean age in bins of logσ are shown from Nelan et al. (2005) (circles) and Caldwell et al. (2003) (squares), with horizontal errors showing the range of logσ of each bin and vertical error bars showing the rms dispersion in ages at the given velocity dispersion (which can be…”