Old age and supersolar metallicity in a massive z ~ 1.4 early-type galaxy from VLT/X-Shooter spectroscopy

I. Lonoce, M. Longhetti, C. Maraston, D. Thomas, C. Mancini, A. Cimatti, F. Ciocca, A. Citro, E. Daddi, S. di Serego Alighieri, A. Gargiulo, R. Maiolino, F. Mannucci, M. Moresco, L. Pozzetti, S. Quai, P. Saracco

Research output: Contribution to journalArticlepeer-review

35 Scopus citations

Abstract

We present the first estimate of age, stellar metallicity and chemical abundance ratios, for an individual early-type galaxy at high-redshift (z = 1.426) in the COSMOS (Cosmological Evolution Survey) field. Our analysis is based on observations obtained with the X-Shooter instrument at the Very Large Telescope (VLT), which cover the visual and near-infrared spectrum at high (R > 5000) spectral resolution. We measure the values of several spectral absorptions tracing chemical species, in particular magnesium and iron, besides determining the age-sensitive D4000 break.We compare the measured indices to stellar population models, finding good agreement. We find that our target is an old (t > 3 Gyr), high-metallicity ([Z/H] > 0.5) galaxy which formed its stars at zform > 5 within a short time-scale ~ 0.1 Gyr, as testified by the strong [a/Fe] ratio (>0.4), and has passively evolved in the first > 3-4 Gyr of its life.We have verified that this result is robust against the choice and number of fitted spectral features, and stellar population model. The result of an old age and high-metallicity has important implications for galaxy formation and evolution confirming an early and rapid formation of the most massive galaxies in the Universe.

Original languageEnglish (US)
Pages (from-to)3912-3919
Number of pages8
JournalMonthly Notices of the Royal Astronomical Society
Volume454
Issue number4
DOIs
StatePublished - Dec 21 2015
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.

Keywords

  • Galaxies: elliptical and lenticular, cD
  • Galaxies: high-redshift
  • Galaxies: stellar content

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