Stellar populations of quasar host galaxies with MFICA decomposition
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Oxford University Press (OUP)
https://doi.org/10.1093/mnras/staf1557
https://doi.org/10.1093/mnras/staf1557
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Funder: National Science Foundation; doi: https://doi.org/10.13039/100000001
Funder: U.S. Department of Energy; doi: https://doi.org/10.13039/100000015
Funder: National Aeronautics and Space Administration; doi: https://doi.org/10.13039/100000104
Funder: University of Basel; doi: https://doi.org/10.13039/100008375
Funder: University of Cambridge; doi: https://doi.org/10.13039/501100000735
Funder: Case Western Reserve University; doi: https://doi.org/10.13039/100008136
Funder: Drexel University; doi: https://doi.org/10.13039/100008211
Funder: Johns Hopkins University; doi: https://doi.org/10.13039/100007880
Funder: New Mexico State University; doi: https://doi.org/10.13039/100009611
Funder: Ohio State University; doi: https://doi.org/10.13039/100006928
Funder: University of Pittsburgh; doi: https://doi.org/10.13039/100007921
Funder: University of Portsmouth; doi: https://doi.org/10.13039/100009153
Funder: Princeton University; doi: https://doi.org/10.13039/100006734
ABSTRACT Galaxy evolution theories require co-evolution between accreting supermassive black holes (SMBH) and galaxies to explain many properties of the local galaxy population, yet observational evidence for the mechanisms driving this co-evolution is lacking. The recent star formation histories of the host galaxies of accreting SMBHs [active galactic nuclei (AGNs)] can help constrain the processes that feed SMBHs and halt star formation in galaxies, but are difficult to obtain for the most luminous AGNs (quasars). We introduce Mean-Field Independent Component Analysis (MFICA) to decompose quasar spectra and obtain recent star formation histories of their host galaxies. Applying MFICA to quasar spectra from the Sloan Digital Sky Survey DR7 Quasar Catalogue in the redshift range $0.16 \le z \le 0.76$, we find that 53 per cent of quasar host galaxies are star-forming, 17 per cent lie in the green-valley, and only 5 per cent are quiescent. This contrasts with 14, 11, and 74 per cent of a mass-matched control sample that are star-forming, green-valley, and quiescent, respectively. We find that $\sim 25$ per cent of quasars are hosted by post-starburst galaxies, an excess of $28\pm 1$ compared to our control sample. While the heterogeneity of recent star formation histories implies multiple SMBH feeding mechanisms, the excess of post-starburst host galaxies demonstrates the link between accreting SMBHs and a recent starburst followed by rapid quenching. Given that massive post-starburst galaxies are predominantly caused by gas-rich major mergers, our results indicate that $30\!-\!50$ per cent of quasars originate from merger-induced starbursts.
Funder: U.S. Department of Energy; doi: https://doi.org/10.13039/100000015
Funder: National Aeronautics and Space Administration; doi: https://doi.org/10.13039/100000104
Funder: University of Basel; doi: https://doi.org/10.13039/100008375
Funder: University of Cambridge; doi: https://doi.org/10.13039/501100000735
Funder: Case Western Reserve University; doi: https://doi.org/10.13039/100008136
Funder: Drexel University; doi: https://doi.org/10.13039/100008211
Funder: Johns Hopkins University; doi: https://doi.org/10.13039/100007880
Funder: New Mexico State University; doi: https://doi.org/10.13039/100009611
Funder: Ohio State University; doi: https://doi.org/10.13039/100006928
Funder: University of Pittsburgh; doi: https://doi.org/10.13039/100007921
Funder: University of Portsmouth; doi: https://doi.org/10.13039/100009153
Funder: Princeton University; doi: https://doi.org/10.13039/100006734
ABSTRACT Galaxy evolution theories require co-evolution between accreting supermassive black holes (SMBH) and galaxies to explain many properties of the local galaxy population, yet observational evidence for the mechanisms driving this co-evolution is lacking. The recent star formation histories of the host galaxies of accreting SMBHs [active galactic nuclei (AGNs)] can help constrain the processes that feed SMBHs and halt star formation in galaxies, but are difficult to obtain for the most luminous AGNs (quasars). We introduce Mean-Field Independent Component Analysis (MFICA) to decompose quasar spectra and obtain recent star formation histories of their host galaxies. Applying MFICA to quasar spectra from the Sloan Digital Sky Survey DR7 Quasar Catalogue in the redshift range $0.16 \le z \le 0.76$, we find that 53 per cent of quasar host galaxies are star-forming, 17 per cent lie in the green-valley, and only 5 per cent are quiescent. This contrasts with 14, 11, and 74 per cent of a mass-matched control sample that are star-forming, green-valley, and quiescent, respectively. We find that $\sim 25$ per cent of quasars are hosted by post-starburst galaxies, an excess of $28\pm 1$ compared to our control sample. While the heterogeneity of recent star formation histories implies multiple SMBH feeding mechanisms, the excess of post-starburst host galaxies demonstrates the link between accreting SMBHs and a recent starburst followed by rapid quenching. Given that massive post-starburst galaxies are predominantly caused by gas-rich major mergers, our results indicate that $30\!-\!50$ per cent of quasars originate from merger-induced starbursts.