Extreme MgII Emission in Recently-Quenched Galaxies: A New Sample of Intermediate-Redshift Post-Starburst Quasars from the DESI Early Data Release
Abstract
Post-starburst galaxies are galaxies which have recently and rapidly shut off star formation. AGN activity is often invoked to explain this rapid quenching, but most post-starburst selection methods select against optical AGN, motivating searches for "post-starburst quasars." We present DESI observations of ten post-starburst quasars with significant MgII emission (LMgII ≥ 3 × 1041 erg/s). This is the first sample of post-starburst quasars to be selected from a post-starburst galaxy parent sample rather than a quasar catalog. Quasars make up 4.6+1.6−1.2% of the post-starburst parent sample at 0.49 ≤ z ≤ 1.39. Using multiwavelength AGN diagnostics, we find that 26+3.0−2.8% of post-starbursts in the parent sample host AGN. We find that post-starburst selection methods are biased against AGN with LBol≳1045 erg s−1, potentially removing the quasars responsible for driving outflows that aid in quenching. Finally, we find that 9/10 post-starburst quasars in our sample have no detected broad Hβ, similar to so-called "MgII emitters" that may be the remnants of fading quasars; if confirmed, these objects suggest a link between post-starburst galaxies and variable AGN. Our new sample of post-starburst quasars provides a link between previously reported local and high redshift post-starburst quasars during the epoch when star formation throughout the universe was declining.
Related
- Unveiling the Origins of the Molecular Gas Reservoirs in Recently Quenched Massive Galaxies
- Euclid Quick Data Release (Q1). Exploring the complexity of quenching processes across time, environment, and mass through recently quenched galaxies
- The Evolution of the Circumgalactic Medium after a starburst in DESI Post-Starburst Galaxies
- SQuIGGL⃗E: Ubiquitous Cool Gas Outflows with Large Mass-Loading Factors in z∼0.7 Post-starburst Galaxies
- X-ray measurements of the elemental abundances for the diffuse emission in the nuclear starburst galaxy NGC 3079
BibTeX
@misc{verrico2026extreme,
title = {{Extreme MgII Emission in Recently-Quenched Galaxies: A New Sample of Intermediate-Redshift Post-Starburst Quasars from the DESI Early Data Release}},
author = {Margaret E. Verrico and Aayan Verma and K. Decker French and David J. Setton and Omar Almaini and Jenny E. Greene and Stephanie LaMassa and Yuanze Luo and Pallavi Patil and Kate Rowlands and Dharlenny Soto},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.35343},
eprint = {2609.35343},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.35343},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Extreme MgII Emission in Recently-Quenched Galaxies: A New Sample of Intermediate-Redshift Post-Starburst Quasars from the DESI Early Data Release
AU - Margaret E. Verrico
AU - Aayan Verma
AU - K. Decker French
AU - David J. Setton
AU - Omar Almaini
AU - Jenny E. Greene
AU - Stephanie LaMassa
AU - Yuanze Luo
AU - Pallavi Patil
AU - Kate Rowlands
AU - Dharlenny Soto
PY - 2026
DA - 2026/09/28
PB - arXiv
DO - 10.48550/arxiv.2609.35343
UR - https://arxiv.org/abs/2609.35343
AB - Post-starburst galaxies are galaxies which have recently and rapidly shut off star formation. AGN activity is often invoked to explain this rapid quenching, but most post-starburst selection methods select against optical AGN, motivating searches for "post-starburst quasars." We present DESI observations of ten post-starburst quasars with significant MgII emission (L_MgII ≥ 3 × 10^41 erg/s). This is the first sample of post-starburst quasars to be selected from a post-starburst galaxy parent sample rather than a quasar catalog. Quasars make up 4.6^+1.6_−1.2% of the post-starburst parent sample at 0.49 ≤ z ≤ 1.39. Using multiwavelength AGN diagnostics, we find that 26^+3.0_−2.8% of post-starbursts in the parent sample host AGN. We find that post-starburst selection methods are biased against AGN with L_Bol≳10^45 erg s^−1, potentially removing the quasars responsible for driving outflows that aid in quenching. Finally, we find that 9/10 post-starburst quasars in our sample have no detected broad Hβ, similar to so-called "MgII emitters" that may be the remnants of fading quasars; if confirmed, these objects suggest a link between post-starburst galaxies and variable AGN. Our new sample of post-starburst quasars provides a link between previously reported local and high redshift post-starburst quasars during the epoch when star formation throughout the universe was declining.
ER -