Where do quasar hosts lie with respect to the size-mass relation of galaxies?

Abstract

The evolution of the galaxy size - stellar mass (Mstellar) relation has been a puzzle for over a decade. High redshift galaxies are significantly more compact than galaxies observed today, at an equivalent mass, but how much of this apparent growth is driven by progenitor bias, minor mergers, secular processes, or feedback from AGN is unclear. To help disentangle the physical mechanisms at work by addressing the latter, we study the galaxy size - Mstellar relation of 32 carefully-selected broad-line AGN hosts at 1.2 < z < 1.7 (7.5 < log M_BH < 8.5; L_bol/L_Edd > 0.1). Using HST with multi-band photometry and state-of-the-art modeling techniques, we measure half-light radii while accounting for uncertainties from subtracting bright central point sources. We find AGN hosts to have sizes ranging from 1 to 6 kpc at Mstellar ~ 0.3 - 1 x 10^11 Msun. Thus, many hosts have intermediate sizes as compared to equal-mass star-forming and quiescent galaxies. While inconsistent with the idea that AGN feedback may induce an increase in galaxy sizes, this finding is consistent with hypotheses in which AGNs preferentially occur in systems with prior concentrated gas reservoirs, or are involved in secular compaction processes perhaps responsible for simultaneously building bulges and shutting down star formation. If driven by minor mergers, which do not grow central black holes as fast as they do bulge-like stellar structures, such a process would explain both the galaxy size - mass relation observed here and the evolution in the black hole, bulge mass relation described in a companion paper.

4 pages; 1 figure; To be resubmitted to ApJ Letters imminently; minor corrections based on comments from the referee have been included; Further comments are welcome

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Cited by in corpus (16)

• Hyper Suprime-Cam Subaru Strategic Program: A Mass-Dependent Slope of the Galaxy Size-Mass Relation at $z<1$
• A local baseline of the black hole mass scaling relations for active galaxies. IV. Correlations between $M_{\mathrm{BH}}$ and host galaxy $\sigma$, stellar mass, and luminosity
• The Sizes of Quasar Host Galaxies with the Hyper Suprime-Cam Subaru Strategic Program
• Opening the era of quasar host studies at high redshift with JWST
• The rocky road to quiescence: compaction and quenching of quasar host galaxies at z~2
• The Impact of Dust on the Sizes of Galaxies in the Epoch of Reionization
• The host galaxies of z=7 quasars: predictions from the BlueTides simulation
• The Star-forming Main Sequence of the Host Galaxies of Low-redshift Quasars
• AGN accretion and black hole growth across compact and extended galaxy evolution phases
• Mass and Environment as Drivers of Galaxy Evolution. IV. On the Quenching of Massive Central Disk Galaxies in The Local Universe
• Molecular Outflows in z > 6 QSO Hosts Driven by Star Formation
• ALMA resolves the first strongly-lensed Optical/NIR-dark galaxy
• Cold Mode Gas Accretion on Two Galaxy Groups at z$\sim$2
• Discovery of a radio jet in the Cloverleaf Quasar at z = 2.56
• Inferences on relations between distant supermassive black holes and their hosts complemented by the galaxy fundamental plane
• HARMONI view of the host galaxies of active galactic nuclei around cosmic noon: Resolved stellar morpho-kinematics and the M${}_{BH}$-${\sigma }_{\star }$ relation