A large population of recently-quenched red-sequence dwarf galaxies in the outskirts of the Coma Cluster

Abstract

We analyse the stellar populations of 75 red-sequence dwarf galaxies in the Coma cluster, based on high signal-to-noise spectroscopy from the 6.5m MMT. The sample covers a luminosity range 3-4 magnitudes below M*, in the cluster core and in a field centred 1 deg to the south-west. We find a strong dependence of the absorption line strengths with location in the cluster. Galaxies further from the cluster centre have stronger Balmer lines than inner-field galaxies of the same luminosity. The magnesium lines are weaker at large radius, while the iron lines are not correlated with radius. Converting the line strengths into estimates of stellar age, metallicity and abundance ratios, we find the gradients are driven by variations in age (>6 sigma significance) and in the iron abundance Fe/H (~2.7 sigma significance). The light element (Mg, C, N, Ca) abundances are almost independent of radius. At radius of 0.4-1.3 degree (~0.3-1.0x the virial radius), dwarf galaxies have ages ~3.8 Gyr on average, compared to ~6 Gyr near the cluster centre. The outer dwarfs are also ~50% more iron-enriched, at given luminosity. Our results confirm earlier indications that the ages of red-sequence galaxies depend on location within clusters, and in Coma in particular. The exceptionally strong trends found here suggest that dwarf galaxies are especially susceptible to environmental "quenching", and/or that the south-west part of Coma is a particularly clear example of recent quenching in an infalling subcluster.

Accepted by MNRAS (Letters); six pages

References in corpus (11)

• The Fifth Data Release of the Sloan Digital Sky Survey
• The 2dF Galaxy Redshift Survey: The environmental dependence of galaxy star formation rates near clusters
• Hectospec, the MMT's 300 Optical Fiber-Fed Spectrograph
• Population Synthesis in the Blue IV: Accurate Model Predictions for Lick Indices and UBV Colors in Single Stellar Populations
• The colour magnitude relation for galaxies in the Coma cluster
• Stellar populations of early-type galaxies in different environments I. Line-strength indices
• Starburst galaxies in cluster-feeding filaments unveiled by Spitzer
• The HST/ACS Coma Cluster Survey: I - Survey Objectives and Design
• The NOAO Fundamental Plane Survey - III. Variations in the stellar populations of red-sequence galaxies from the cluster core to the virial radius
• A deep AAOmega survey of low-luminosity galaxies in the Shapley Supercluster: Stellar population trends
• A photometric and spectroscopic study of dwarf and giant galaxies in the Coma cluster - V. Dependence of the spectroscopic properties on location in the cluster

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• The HST/ACS Coma Cluster Survey. II. Data Description and Source Catalogs
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• Colours of Bulges and Discs within Galaxy Clusters and the Signature of Disc Fading on Infall
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• The anatomy of the NGC 5044 group -- II. Stellar populations and star-formation histories
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