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MOSFIRE Spectroscopy of Quiescent Galaxies at 1.5 < z < 2.5. I. Evolution of Structural and Dynamical Properties

Belli, S; Newman, AB; Ellis, R; (2017) MOSFIRE Spectroscopy of Quiescent Galaxies at 1.5 < z < 2.5. I. Evolution of Structural and Dynamical Properties. The Astrophysical Journal , 834 (1) , Article 18. 10.3847/1538-4357/834/1/18. Green open access

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Abstract

We present deep near-infrared spectra for a sample of 24 quiescent galaxies in the redshift range 1.5 < z < 2.5 obtained with the MOSFIRE spectrograph at the W. M. Keck Observatory. In conjunction with a similar dataset we obtained in the range 1 < z < 1.5 with the LRIS spectrograph, we analyze the kinematic and structural properties for 80 quiescent galaxies, the largest homogeneously-selected sample to date spanning 3 Gyr of early cosmic history. Analysis of our Keck spectra together with measurements derived from associated HST images reveals increasingly larger stellar velocity dispersions and smaller sizes to redshifts beyond z~2. By classifying our sample according to Sersic indices, we find that among disk-like systems the flatter ones show a higher dynamical to stellar mass ratio compared to their rounder counterparts which we interpret as evidence for a significant contribution of rotational motion. For this subset of disk-like systems, we estimate that V/sigma, the ratio of the circular velocity to the intrinsic velocity dispersion, is a factor of two larger than for present-day disky quiescent galaxies. Although this ratio between dynamical and stellar mass is roughly constant with redshift for the total quiescent population, we see a redshift evolution for the subset of spheroidal systems. By matching galaxies at fixed velocity dispersion, we are able to connect descendants with their earlier progenitors thereby determining the growth in size for quiescent galaxies over two distinct redshift ranges for the first time. We measure a size growth rate of 0.13 dex/Gyr over 1.3 < z < 2 which contrasts with a rate of only 0.03 dex/Gyr over 0 < z < 1.3. We discuss the physical origin of this time-dependent growth in size in the context of the associated reduction of the systematic rotation.

Type: Article
Title: MOSFIRE Spectroscopy of Quiescent Galaxies at 1.5 < z < 2.5. I. Evolution of Structural and Dynamical Properties
Open access status: An open access version is available from UCL Discovery
DOI: 10.3847/1538-4357/834/1/18
Publisher version: https://doi.org/10.3847/1538-4357/834/1/18
Language: English
Additional information: This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: galaxies: evolution; galaxies: formation; galaxies: high-redshift; galaxies: kinematics and dynamics; galaxies: stellar content
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
URI: https://discovery.ucl.ac.uk/id/eprint/1527505
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