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### Electronic data

• 2007.00663v1

Rights statement: This is a pre-copy-editing, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The definitive publisher-authenticated version is [citation] is available online at: url

Accepted author manuscript, 3.51 MB, PDF document

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

Research output: Contribution to journalJournal article

Forthcoming
• Francesco D'Eugenio
• Arjen van der Wel
• Po-Feng Wu
• Tania M. Barone
• Josha van Houdt
• Rachel Bezanson
• Caroline M. S. Straatman
• Camilla Pacifici
• Anna Gallazzi
• Vivienne Wild
• David Sobral
• Eric F. Bell
• Stefano Zibetti
• Lamiya Mowla
• Marijn Franx
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Journal publication date 29/06/2020 Monthly Notices of the Royal Astronomical Society Accepted/In press English

### 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.

### Bibliographic note

This is a pre-copy-editing, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The definitive publisher-authenticated version is [citation] is available online at: url