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Published April 2016 | Published + Submitted
Journal Article Open

AGN host galaxy mass function in COSMOS Is AGN feedback responsible for the mass-quenching of galaxies


We investigate the role of supermassive black holes in the global context of galaxy evolution by measuring the host galaxy stellar mass function (HGMF) and the specific accretion rate, that is, λ_(SAR), the distribution function (SARDF), up to z ~ 2.5 with ~1000 X-ray selected AGN from XMM-COSMOS. Using a maximum likelihood approach, we jointly fit the stellar mass function and specific accretion rate distribution function, with the X-ray luminosity function as an additional constraint. Our best-fit model characterizes the SARDF as a double power-law with mass-dependent but redshift-independent break, whose low λ_(SAR) slope flattens with increasing redshift while the normalization increases. This implies that for a given stellar mass, higher λ_(SAR) objects have a peak in their space density at earlier epoch than the lower λ_(SAR) objects, following and mimicking the well-known AGN cosmic downsizing as observed in the AGN luminosity function. The mass function of active galaxies is described by a Schechter function with an almost constant M^∗_⋆ and a low-mass slope α that flattens with redshift. Compared to the stellar mass function, we find that the HGMF has a similar shape and that up to log (M_⋆/M_⊙) ~ 11.5, the ratio of AGN host galaxies to star-forming galaxies is basically constant (~10%). Finally, the comparison of the AGN HGMF for different luminosity and specific accretion rate subclasses with a previously published phenomenological model prediction for the "transient" population, which are galaxies in the process of being mass-quenched, reveals that low-luminosity AGN do not appear to be able to contribute significantly to the quenching and that at least at high masses, that is, M_⋆ > 10^(10.7) M_⊙, feedback from luminous AGN (log L_(bol) ≳ 46 [erg/s]) may be responsible for the quenching of star formation in the host galaxy.

Additional Information

© 2016 ESO. Received 23 September 2015. Accepted 5 January 2016. We thank the referee for the careful reading and helpful suggestions that helped to improve the manuscript. This work is based on the COSMOS program. The HST COSMOS Treasury program was supported through NASA grant HST-GO-09822. This work is mainly based on observations obtained with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and the USA (NASA), and with the European Southern Observatory under Large Program 175.A-0839, Chile. A.B. and E.P. acknowledge financial support from INAF under the contract PRIN-INAF-2012. A.S. acknowledges support by JSPS KAKENHI Grant Number 26800098. MCMC corner plots make use of triangle.py (Foreman-Mackey et al. 2013).

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Published - aa27436-15.pdf

Submitted - 1601.02091v1.pdf


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August 20, 2023
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