From Carbon to Cobalt: Chemical compositions and ages of $z\sim 0.7$ quiescent galaxies

Abstract

We present elemental abundance patterns (C, N, Mg, Si, Ca, Ti, V, Cr, Fe, Co, and Ni) for a population of 135 massive quiescent galaxies at $z\sim 0.7$ with ultra-deep rest-frame optical spectroscopy drawn from the LEGA-C survey. We derive average ages and elemental abundances in four bins of stellar velocity dispersion (${\sigma }_v$) ranging from 150 kms${}^{-1}$ to 250 kms${}^{-1}$ using a full-spectrum hierarchical Bayesian model. The resulting elemental abundance measurements are precise to 0.05dex. The majority of elements, as well as the total metallicity and stellar age, show a positive correlation with ${\sigma }_v$. Thus, the highest dispersion galaxies formed the earliest and are the most metal-rich. We find only mild or non-significant trends between [X/Fe] and ${\sigma }_v$, suggesting that the average star-formation timescale does not strongly depend on velocity dispersion. To first order, the abundance patterns of the $z\sim 0.7$ quiescent galaxies are strikingly similar to those at $z\sim 0$. However, at the lowest velocity dispersions the $z\sim 0.7$ galaxies have slightly enhanced N, Mg, Ti, and Ni abundance ratios and earlier formation redshifts than their $z\sim 0$ counterparts. Thus, while the higher-mass quiescent galaxy population shows little evolution, the low-mass quiescent galaxies population has grown significantly over the past six billion years. Finally, the abundance patterns of both $z\sim 0$ and $z\sim 0.7$ quiescent galaxies differ considerably from theoretical prediction based on a chemical evolution model, indicating that our understanding of the enrichment histories of these galaxies is still very limited.

24 pages, 12 figures, accepted for publication in ApJ

References in corpus (23)

• The Cosmic Evolution Survey (COSMOS) -- Overview
• The propagation of uncertainties in stellar population synthesis modeling I: The relevance of uncertain aspects of stellar evolution and the IMF to the derived physical properties of galaxies
• EAZY: A Fast, Public Photometric Redshift Code
• Improving the full spectrum fitting method: accurate convolution with Gauss-Hermite functions
• A simple model to interpret the ultraviolet, optical and infrared emission from galaxies
• An ultra-deep near-infrared spectrum of a compact quiescent galaxy at z=2.2
• The Atlas3D Project - XXX. Star formation histories and stellar population scaling relations of early-type galaxies
• Population Synthesis in the Blue IV: Accurate Model Predictions for Lick Indices and UBV Colors in Single Stellar Populations
• Properties of Galaxy Groups in the SDSS: II.- AGN Feedback and Star Formation Truncation
• Charting the evolution of the ages and metallicities of massive galaxies since z=0.7
• Multi-Element Abundance Measurements from Medium-Resolution Spectra. IV. Alpha Element Distributions in Milky Way Dwarf Satellite Galaxies
• The Assembly Histories of Quiescent Galaxies Since z=0.7 from Absorption Line Spectroscopy
• Ages and Abundances of Red Sequence Galaxies as a Function of LINER Emission Line Strength
• A massive, quiescent, population II galaxy at a redshift of 2.1
• The Extended IRTF Spectral Library: Expanded coverage in metallicity, temperature, and surface gravity
• GALEX UV Color Relations for Nearby Early-Type Galaxies
• Rejuvenation in $z\sim 0.8$ quiescent galaxies in LEGA-C
• SDSS-IV MaNGA: Radial Gradients in Stellar Population Properties of Early-Type and Late-Type Galaxies
• Color gradients along the quiescent galaxy sequence: clues to quenching and structural growth
• The MASSIVE Survey - XII Connecting Stellar Populations of Early-Type Galaxies to Kinematics and Environment
• Resolved Multi-element Stellar Chemical Abundances in the Brightest Quiescent Galaxy at z $\sim$ 2
• Evolution of the Stellar Mass-Metallicity Relation. II. Constraints on Galactic Outflows from the Mg Abundances of Quiescent Galaxies
• The Velocity Dispersion Function for Massive Quiescent and Star-Forming Galaxies at 0.6 $<$ z $\le$ 1.0

Cited by in corpus (3)

• SIMBA-C: An updated chemical enrichment model for galactic chemical evolution in the SIMBA simulation
• Age and metal gradients in massive quiescent galaxies at $0.6\lesssim z\lesssim 1.0$: implications for quenching and assembly histories
• [Mg/Fe] and variable initial mass function: Revision of [$\alpha$/Fe] for massive galaxies