Publication Date

9-1-2020

Document Type

Article

Publication Title

Monthly Notices of the Royal Astronomical Society

Volume

497

Issue

1

DOI

10.1093/mnras/staa1992

First Page

626

Last Page

631

Abstract

We present new spectra obtained using Keck/KCWI and perform kinematics and stellar population analyses of the shell galaxy NGC 474, from both the galaxy centre and a region from the outer shell. We show that both regions have similarly extended star formation histories although with different stellar population properties. The central region of NGC 474 is dominated by intermediate-Aged stars (8.3 ± 0.3 Gyr) with subsolar metallicity ([Z/H] =-0.24 ± 0.07 dex) while the observed shell region, which hosts a substantial population of younger stars, has a mean luminosity-weighted age of 4.0 ± 0.5 Gyr with solar metallicities ([Z/H] =-0.03 ± 0.09 dex). Our results are consistent with a scenario in which NGC 474 experienced a major to intermediate merger with a log$(M_∗/\rm M_\odot) \sim 10$ mass satellite galaxy at least ${\sim}2$ Gyr ago which produced its shell system. This work shows that the direct spectroscopic study of low-surface brightness stellar features, such as shells, is now feasible and opens up a new window to understanding galaxy formation and evolution.

Funding Number

1518294

Funding Sponsor

National Science Foundation

Keywords

galaxies: individual (NGC 474), galaxy: evolution, galaxy: formation

Comments

This article has been accepted for publication in the Monthly Notices of the Royal Astronomical Society ©: 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

Department

Physics and Astronomy

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