Inverse stellar population age gradients of post-starburst galaxies at z=0.8 with LEGA-C

Journal
Date Issued
2020
Author(s)
Francesco D'Eugenio
•
Arjen van der Wel
•
Po-Feng Wu
•
Tania M. Barone
•
Josha van Houdt
•
Rachel Bezanson
•
Caroline M. S. Straatman
•
Camilla Pacifici
•
Adam Muzzin
•
•
Vivienne Wild
•
David Sobral
•
Eric F. Bell
•
Stefano Zibetti
•
Lamiya Mowla
•
Marijn Franx
DOI
Abstract
We use deep, spatially resolved spectroscopy from the LEGA-C Survey to study radial variations in the stellar population of 17 spectroscopically-selected post-starburst (PSB) galaxies. We use spectral fitting to measure two Lick indices, $H{\delta}_A$ and $Fe4383$, and find that, on average, PSB galaxies have radially decreasing $H{\delta}_A$ and increasing $Fe4383$ profiles. In contrast, a control sample of quiescent, non-PSB galaxies in the same mass range shows outwardly increasing $H{\delta}_A$ and decreasing $Fe4383$. The observed gradients are weak ($\approx-0.2$ \r{A}/$R_e$), mainly due to seeing convolution. A two-SSP model suggests intrinsic gradients are as strong as observed in local PSB galaxies ($\approx -0.8$ \r{A}$/R_e$). We interpret these results in terms of inside-out growth (for the bulk of the quiescent population) vs star formation occurring last in the centre (for PSB galaxies). At $z\approx0.8$, central starbursts are often the result of gas-rich mergers, as evidenced by the high fraction of PSB galaxies with disturbed morphologies and tidal features (40%). Our results provide additional evidence for multiple paths to quiescence: a standard path, associated with inside-out disc formation and with gradually decreasing star-formation activity, without fundamental structural transformation, and a fast path, associated with centrally-concentrated starbursts, leaving an inverse age gradient and smaller half-light radius.
Volume
497
Issue
1
Start page
389
Uri
Url
Issn Identifier
0035-8711
Ads BibCode
2020MNRAS.497..389D
Rights
open.access
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