Near UV properties of Early-Type Galaxies at z~1

TL;DR

This study uses spectral fitting to estimate the average stellar ages of early-type galaxies at redshift around 1, revealing partial discrepancies with previous methods and exploring UV spectral properties.

Contribution

It introduces a spectral fitting approach to determine stellar ages of high-redshift ETGs and compares results with traditional FP-based estimates, highlighting limitations.

Findings

Spectral fits underestimate ages of luminous ETGs.

Partial agreement between spectral and FP age estimates.

Analysis of near-UV spectral indices related to stellar ages.

Abstract

We have used spectral fits to SSP-based atmosphere models to derive an estimate of the average stellar age for an almost complete sample of 15 Early-Type Galaxies (ETG) at 0.88<z<1.3. The results are in only partial agreement with the age estimates previously obtained for the same objects from an analysis of the M/L_B ratio, derived from the Fundamental Plane (FP) parameters. In particular spectral fits seem to underestimate the age of the most luminous ETG, and therefore do not reproduce the downsizing effect, which is clear for the FP ages. We also analyse the relationship between the spectral-fit ages and various near-UV spectral indices.