Stellar population properties of individual massive early-type galaxies at 1.4 < z < 2

Abstract

We analyse publicly available, individual spectra of four massive ($M\gt 10^{11}\, \mathrm{M}_{\odot }$) early-type galaxies with redshifts in the range 1.4 ≤ z ≤ 2 to determine their stellar content, extending our previous work up to z ∼ 2. The wide wavelength range of the VLT/X-Shooter spectroscopic data in the UV–Optical–NIR arms along with the availability of spectro-photometry allows us to explore different techniques to obtain the stellar population properties, namely through age/metallicity-sensitive spectral indices, full spectral fitting, and broad-band photometric fitting. Moreover, together with the widely used optical Lick indices, we consider further indices in the UV rest frame, and demonstrate that UV indices significantly help the accuracy of the resulting population parameters. We find galaxy ages ranging from 0.2 to 4 Gyr, where the oldest galaxy is found at the lowest redshift, with an excellent agreement between ages determined via indices, full spectral fitting, or broad-band colours. These ages are in perfect agreement with ages of local galaxies at the same velocity dispersion when we assume pure passive evolution. Total metallicities derived from indices show some scatter (between less than half-solar to very high values, [Z/H] ∼ 0.6). We speculate on possible mechanisms explaining these values, but given the sample size and low S/N of the spectra no conclusion can be made. Indices in the UV rest frame generally lead to similar conclusions as optical indices. For the oldest galaxy (4 Gyr), we show that its UV indices can only be explained by stellar population models including a UV contribution from old stellar populations, suggesting that old, UV bright populations start to inhabit mature galaxies of a few Gyr of age. This is the highest redshift (z ∼ 1.4) detection of the UV upturn up to date.

L-GALAXIES 2020: The evolution of radial metallicity profiles and global metallicities in disc galaxies

“…We also find a much reduced evolution in the M * R for ETGs compared to star-forming galaxies in L-G 2020, in agreement with observations (e.g. Kriek et al 2019;Estrada-Carpenter et al 2019;Leethochawalit et al 2019;Lonoce et al 2020). At log 10 ( * / M ) = 11.0, * increases by only 0.04 dex from = 2 to 0 for ETGs in the modified model.…”

“…Kewley & Dopita 2002;Yates et al 2012;Sánchez et al 2014;Belfiore et al 2017;Erroz-Ferrer et al 2019), stellar populations (e.g. Maraston 2005;Lonoce et al 2020), and the circumgalactic medium (CGM) (e.g. Tumlinson et al 2017;Werner & Mernier 2020;Péroux & Howk 2020).…”

Toward a Better Understanding of Cosmic Chronometers: Stellar Population Properties of Passive Galaxies at Intermediate Redshift

“…For this reason, they are mostly limited to samples of few up to dozens galaxies (e.g. Jørgensen & Chiboucas 2013;Gallazzi et al 2014;Lonoce et al 2015Lonoce et al , 2020Belli et al 2019;Carnall et al 2019;Kriek et al 2019;Tacchella et al 2021;Beverage et al 2021), and/or require the stacking of different galaxy spectra (e.g. Choi et al 2014;Onodera et al 2015).…”

Resolved Multi-element Stellar Chemical Abundances in the Brightest Quiescent Galaxy at z ∼ 2

“…However, the faintness of high-z quiescent galaxies makes spectroscopic observations extremely challenging. In recent years, several authors have attempted to extend stellar chemical abundance studies to higher redshifts using a single or stacked spectra of a handful of quiescent galaxies (e.g., Onodera et al 2015;Lonoce et al 2015;Kriek et al 2019;Lonoce et al 2020). Currently, there is only one quiescent galaxy at z ∼ 2 for which [Fe/H] and [Mg/Fe] have been measured to ∼ 0.1 dex precision (COSMOS-11494, Kriek et al 2016).…”