The Evolution of the Circumgalactic Medium after a starburst in DESI Post-Starburst Galaxies
Abstract
We present a statistical study of the cool circumgalactic medium (CGM) around massive post-starburst galaxies, traced by Mg II λλ2796,2803 absorption in background quasar spectra from the Dark Energy Spectroscopic Instrument (DESI) Data Release 2. Cross-matching ~1.98 million quasar sightlines with luminous red galaxies at 0.4 < z < 0.76 with stellar masses between 10.6 < log10(M*/M⊙) < 12 yields ~143 million galaxy-quasar pairs, 50-60 times more per impact-parameter bin than our previous SDSS-based analysis. We stack the Mg II absorption as a function of projected separation and classify the foreground galaxies using mean-field independent component analysis (MFICA), further subdividing the post-starburst population into sub-samples ordered by time since the starburst. The mean Mg II equivalent width declines with impact parameter for every class. Post-starburst galaxies show the strongest absorption of any spectral class, reaching WMgII = 1.58 ± 0.32 Å within 71 kpc, well above star-forming (0.69 ± 0.15 Å) and quiescent (0.22 ± 0.05 Å) galaxies of comparable stellar mass at the same projected separation. Within the post-starburst phase the absorption profile evolves systematically: the youngest systems show the highest, most centrally concentrated absorption and the steepest radial decline, whereas progressively older systems show weaker inner absorption and enhanced absorption at intermediate radii (~300-1000 kpc). Independent Bagpipes star-formation-history fitting confirms that this ordering corresponds to an ageing sequence. We interpret this evolution as the outward redistribution of cool gas expelled by feedback-driven winds, consistent with characteristic outflow velocities of a few hundred km s−1, with a residual inner cool-gas reservoir persisting throughout the post-starburst phase.
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BibTeX
@misc{harvey2026evolution,
title = {{The Evolution of the Circumgalactic Medium after a starburst in DESI Post-Starburst Galaxies}},
author = {Zoe Harvey and Sahyadri Krishna and Rita Tojeiro and Vivienne Wild and Jessica Nicole Aguilar and Steven Ahlen and Eric Armengaud and Florian Beutler and Davide Bianchi and David Brooks and Rebecca Canning and Aurelio Carnero Rosell and Todd Claybaugh and Andrei Cuceu and Axel de la Macorra and Peter Doel and Jaime E. Forero-Romero and Enrique Gaztañaga and Satya Gontcho A Gontcho and Gaston Gutierrez and ChangHoon Hahn and Hiram K. Herrera-Alcantar and Stephanie Juneau and Robert Kehoe and Martin Landriau and Laurent Le Guillou and Marc Manera and Aaron Meisner and Ramon Miquel and John Moustakas and Adam Myers and Seshadri Nadathur and Jeffrey A. Newman and Enrique Paillas and Will Percival and Ignasi Pérez-Ràfols and Francisco Prada and Corentin Ravoux and Graziano Rossi and Rossana Ruggeri and Eusebio Sanchez and Christoph Saulder and David Schlegel and Joseph Harry Silber and Małgorzata Siudek and Gregory Tarlé and Benjamin Alan Weaver and Hu Zou},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.41681},
eprint = {2610.41681},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.41681},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - The Evolution of the Circumgalactic Medium after a starburst in DESI Post-Starburst Galaxies
AU - Zoe Harvey
AU - Sahyadri Krishna
AU - Rita Tojeiro
AU - Vivienne Wild
AU - Jessica Nicole Aguilar
AU - Steven Ahlen
AU - Eric Armengaud
AU - Florian Beutler
AU - Davide Bianchi
AU - David Brooks
AU - Rebecca Canning
AU - Aurelio Carnero Rosell
AU - Todd Claybaugh
AU - Andrei Cuceu
AU - Axel de la Macorra
AU - Peter Doel
AU - Jaime E. Forero-Romero
AU - Enrique Gaztañaga
AU - Satya Gontcho A Gontcho
AU - Gaston Gutierrez
AU - ChangHoon Hahn
AU - Hiram K. Herrera-Alcantar
AU - Stephanie Juneau
AU - Robert Kehoe
AU - Martin Landriau
AU - Laurent Le Guillou
AU - Marc Manera
AU - Aaron Meisner
AU - Ramon Miquel
AU - John Moustakas
AU - Adam Myers
AU - Seshadri Nadathur
AU - Jeffrey A. Newman
AU - Enrique Paillas
AU - Will Percival
AU - Ignasi Pérez-Ràfols
AU - Francisco Prada
AU - Corentin Ravoux
AU - Graziano Rossi
AU - Rossana Ruggeri
AU - Eusebio Sanchez
AU - Christoph Saulder
AU - David Schlegel
AU - Joseph Harry Silber
AU - Małgorzata Siudek
AU - Gregory Tarlé
AU - Benjamin Alan Weaver
AU - Hu Zou
PY - 2026
DA - 2026/10/30
PB - arXiv
DO - 10.48550/arxiv.2610.41681
UR - https://arxiv.org/abs/2610.41681
AB - We present a statistical study of the cool circumgalactic medium (CGM) around massive post-starburst galaxies, traced by Mg II λλ2796,2803 absorption in background quasar spectra from the Dark Energy Spectroscopic Instrument (DESI) Data Release 2. Cross-matching ~1.98 million quasar sightlines with luminous red galaxies at 0.4 < z < 0.76 with stellar masses between 10.6 < log_10(M_*/M_⊙) < 12 yields ~143 million galaxy-quasar pairs, 50-60 times more per impact-parameter bin than our previous SDSS-based analysis. We stack the Mg II absorption as a function of projected separation and classify the foreground galaxies using mean-field independent component analysis (MFICA), further subdividing the post-starburst population into sub-samples ordered by time since the starburst. The mean Mg II equivalent width declines with impact parameter for every class. Post-starburst galaxies show the strongest absorption of any spectral class, reaching W_MgII = 1.58 ± 0.32 Å within 71 kpc, well above star-forming (0.69 ± 0.15 Å) and quiescent (0.22 ± 0.05 Å) galaxies of comparable stellar mass at the same projected separation. Within the post-starburst phase the absorption profile evolves systematically: the youngest systems show the highest, most centrally concentrated absorption and the steepest radial decline, whereas progressively older systems show weaker inner absorption and enhanced absorption at intermediate radii (~300-1000 kpc). Independent Bagpipes star-formation-history fitting confirms that this ordering corresponds to an ageing sequence. We interpret this evolution as the outward redistribution of cool gas expelled by feedback-driven winds, consistent with characteristic outflow velocities of a few hundred km s^−1, with a residual inner cool-gas reservoir persisting throughout the post-starburst phase.
ER -