Inverse stellar population age gradients of post-starburst galaxies at z = 0.8 with LEGA-C
Abstract
We use deep, spatially resolved spectroscopy from the Large Early Galaxy Astrophysics Census 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 δA and Fe 4383 , and find that, on average, PSB galaxies have radially decreasing H δA and increasing Fe 4383 profiles. In contrast, a control sample of quiescent, non-PSB galaxies in the same mass range shows outwardly increasing H δA and decreasing Fe 4383 . The observed gradients are weak (≈−0.2 Å/Re), mainly due to seeing convolution. A two-SSP (simple stellar population) model suggests that intrinsic gradients are as strong as observed in local PSB galaxies (≈−0.8 Å/Re). We interpret these results in terms of inside-out growth (for the bulk of the quiescent population) versus star formation occurring last in the centre (for PSB galaxies). At z ≈ 0.8, 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 per cent). 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.
Citation
D'Eugenio , F , van der Wel , A , Wu (吳柏锋) , P-F , Barone , T M , van Houdt , J , Bezanson , R , Straatman , C M S , Pacifici , C , Muzzin , A , Gallazzi , A , Wild , V , Sobral , D , Bell , E F , Zibetti , S , Mowla , L & Franx , M 2020 , ' Inverse stellar population age gradients of post-starburst galaxies at z = 0.8 with LEGA-C ' , Monthly Notices of the Royal Astronomical Society , vol. 497 , no. 1 , pp. 389-404 . https://doi.org/10.1093/mnras/staa1937
Publication
Monthly Notices of the Royal Astronomical Society
Status
Peer reviewed
ISSN
0035-8711Type
Journal article
Description
Funding: This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 683184). PFW acknowledges the support of the East Asian Core Observatories Association fellowship. TMB is supported by an Australian Government Research Training Program Scholarship. AG and SZ acknowledge support from Istituto Nazionale di Astrofisica (PRIN-SKA2017 program 1.05.01.88.04).Collections
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