The role of galaxy mass on AGN emission: a view from the VANDELS survey

Abstract

We present a comparative analysis of the properties of AGN emitting at radio and X-ray wavelengths. The study is performed on 907 X-ray AGN and 100 radio AGN selected on the CDFS and UDS fields and makes use of new and ancillary data available to the VANDELS collaboration. Our results indicate that the mass of the host galaxy is a fundamental quantity which determines the level of AGN activity at the various wavelengths. Indeed large stellar masses are found to be connected with AGN radio emission, as virtually all radio-active AGN reside within galaxies of M * > 10 10 M . Large stellar masses also seem to favour AGN activity in the X-ray, even though X-ray AGN present a mass distribution which is more spread out and with a non-negligible tail at M * ∼ < 10 9 M . Stellar mass alone is also observed to play a fundamental role in simultaneous radio and X-ray emission: the percentage of AGN active at both wavelengths increases from around 1% of all X-ray AGN residing within hosts of M * < 10 11 M to ∼ 13% in more massive galaxies. In the case of radio-selected AGN, such a percentage moves from ∼ 15% to ∼ 45% (but up to ∼ 80% in the deepest fields). Neither cosmic epoch, nor radio luminosity, X-ray luminosity, Eddington ratio or starformation rate of the hosts are found to be connected to an enhanced probability for joint radio+X-ray emission of AGN origin. Furthermore, only a loose relation is observed between X-ray and radio luminosity in those AGN which are simultaneously active at both frequencies.

What is the origin of the stacked radio emission in radio-undetected quasars?: Insights from a radio-infrared image stacking analysis

“…These results demonstrate that vigorous SF activity is coeval with the growth of the SMBHs residing in the nuclei of the RLQs host galaxies. This agrees with previous works that found evidence for high SFRs in radio AGN (e.g., Seymour et al 2011;Magliocchetti et al 2014;Podigachoski et al 2015;Magliocchetti et al 2016Magliocchetti et al , 2020. Moreover, bright RDQs have been associated with higher SFRs in comparison to their radio-quiet counterparts (e.g., Kalfountzou et al 2014Kalfountzou et al , 2017 The enhancement in the star formation in radio AGN could be explained considering the formation of bow shocks caused by radio jets that compress the interstellar medium in the host galaxy.…”

No strong dependence of Lyman continuum leakage on physical properties of star-forming galaxies at $\mathbf{3.1 \lesssim z \lesssim 3.5}$

“…The sources detected in the Luo et al ( 2017) catalogue at 𝑧 3 are very likely to be AGN, owing to X-ray luminosities of > 10 42 erg s −1 at these redshifts (e.g. Magliocchetti et al 2020;Saxena et al 2020aSaxena et al , 2021. We identify and remove two sources with counterparts in the X-ray catalogue that are also classified as AGN in the catalogue and therefore, the total number of sources in our final sample comes to 183.…”

The VANDELS ESO public spectroscopic survey

“…VANDELS, proposed as an ESO public spectroscopic survey in 2014, aims to shed new light on these aspects, not limiting itself to finding a redshift, but also providing midresolution, high signal-to-noise ratio (S/N) spectra that allow us to study the physical characteristics of the high-redshift galaxies in detail and with statistically meaningful numbers (McLure et al 2018). Since the first data release of VANDELS (Pentericci et al 2018b), a number of different studies have already been published: from dust attenuation and stellar metallicities of star forming (Cullen et al 2018(Cullen et al , 2019Calabrò et al 2021) and quiescent galaxies (Carnall et al 2019(Carnall et al , 2020, to Lyα and He II λ1640 emitters (Marchi et al 2019;Hoag et al 2019;Cullen et al 2020;Saxena et al 2020a,b;Guaita et al 2020), intergalactic-medium properties (Thomas et al 2020) and active galactic nuclei (AGNs) (Magliocchetti et al 2020). All these works were based on only a subset of the data.…”