Inverse stellar population age gradients of post-starburst galaxies at z=0.8 with LEGA-C. (arXiv:2007.00663v1 [astro-ph.GA])

Inverse stellar population age gradients of post-starburst galaxies at z=0.8 with LEGA-C. (arXiv:2007.00663v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+DEugenio_F/0/1/0/all/0/1">Francesco D&#x27;Eugenio</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wel_A/0/1/0/all/0/1">Arjen van der Wel</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wu_P/0/1/0/all/0/1">Po-Feng Wu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Barone_T/0/1/0/all/0/1">Tania M. Barone</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Houdt_J/0/1/0/all/0/1">Josha van Houdt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bezanson_R/0/1/0/all/0/1">Rachel Bezanson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Straatman_C/0/1/0/all/0/1">Caroline M. S. Straatman</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pacifici_C/0/1/0/all/0/1">Camilla Pacifici</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Muzzin_A/0/1/0/all/0/1">Adam Muzzin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gallazzi_A/0/1/0/all/0/1">Anna Gallazzi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wild_V/0/1/0/all/0/1">Vivienne Wild</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sobral_D/0/1/0/all/0/1">David Sobral</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bell_E/0/1/0/all/0/1">Eric F. Bell</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zibetti_S/0/1/0/all/0/1">Stefano Zibetti</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mowla_L/0/1/0/all/0/1">Lamiya Mowla</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Franx_M/0/1/0/all/0/1">Marijn Franx</a>

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 $zapprox0.8$, 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.

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 $zapprox0.8$, 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.

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