The properties of radio and mid-infrared detected galaxies and the effect of environment on the co-evolution of AGN and star formation at z ∼ 1

Abstract

In this study we investigate 179 radio-IR galaxies drawn from a sample of spectroscopically-confirmed galaxies that are detected in radio and mid-infrared (MIR) in the redshift range of 0.55 ≤ z ≤ 1.30 in the Observations of Redshift Evolution in Large Scale Environments (ORELSE) survey. We constrain the Active Galactic Nuclei (AGN) contribution in the total IR luminosity (f AGN ), and estimate the AGN luminosity (L AGN ) and the star formation rate (SFR) using the CIGALE Spectral Energy Distribution (SED) fitting routine. Based on the f AGN and radio luminosity, radio-IR galaxies are split into: galaxies that host either high or low f AGN AGN (high-/lowf AGN ), and star forming galaxies with little to no AGN activity (SFGs). We study the colour, stellar mass, radio luminosity, L AGN and SFR properties of the three radio-IR sub-samples, comparing to a spec-IR sample drawn from spectroscopically-confirmed galaxies that are also detected in MIR. No significant difference between radio luminosity of these sub-samples was found, which could be due to the combined contribution of radio emission from AGN and star formation. We find a positive relationship between L AGN and specific SFR (sSFR) for both AGN sub-samples, strongly suggesting a co-evolution scenario of AGN and SF in these galaxies. A toy model is designed to demonstrate this co-evolution scenario, where we find that, in almost all cases, a rapid quenching timescale is required, which we argue is a signature of AGN quenching. The environmental preference for intermediate/infall regions of clusters/groups remains across the co-evolution scenario, which suggests that galaxies might be in an orbital motion around the cluster/group during the scenario.

Implications of the Environments of Radio-detected Active Galactic Nuclei in a Complex Protostructure at z ∼ 3.3

“…We adopt a primary search radius of 2″ for the overall photometric catalogs that have an observed H-or K-band magnitude. These bands are in similar rest-frame wavelength as the observed i′ band at z ∼ 1 that was used in previous optical matching in the ORELSE survey (e.g., Rumbaugh et al 2012;Shen et al 2020a). We run parallel optical matching using H-and K-band magnitudes and obtain the same matches.…”

“…The final radio catalogs contain sources above 4σ and down to ∼50 μJy. Data reduction and source catalogs for this field are obtained following the same methodology as that used in Shen et al (2020a). The original observation was taken as part of the ORELSE survey, targeting the foreground cluster XLSS005 at z ∼ 1.05 (Valtchanov et al 2004;Lemaux et al 2019;Tomczak et al 2019;Hung et al 2020), but the z ∼ 3.3 protostructure that is the subject of this paper is contained in the same field of view.…”

Extended Radio AGN at z ∼ 1 in the ORELSE Survey: The Confining Effect of Dense Environments

“…Data reduction and source catalogs for the fields (SC1604, SG0023, SC1324, RXJ1757, and RXJ1821) mapped with the traditional VLA are described in Shen et al (2017Shen et al ( , 2019. Those of the remaining seven fields (XLSS005, RXJ1053, RXJ0910, RXJ1716, Cl1137, Cl1429, and Cl1350) mapped with the new JVLA are obtained following the same methodology as in Shen et al (2020). For those catalogs, we automatically detect radio sources down to a 4σ detection flux density limit, where σ is the local rms noise.…”

Environmental effects on AGN activity via extinction-free mid-infrared census

“…They compared the number of sources with varying frac AGN with AGNs classified by spectroscopic surveys and Chandra X-ray surveys in Shim et al (2013) and Krumpe et al (2015), and AGNs classified using Le Phare Oi et al (2021). A similar study by Shen et al (2020) also used CIGALE to select AGNs at 0.55 ≤ z ≤ 1.30 in the ORELSE survey, and they adopted the definition frac AGN ≥ 0.1 as their AGN selection criteria. However, in Wang…”

“…These results by Miller et al (2003) are comparable with a previous study conducted with optically detected galaxies selected from the 15R-North galaxy redshift survey, a uniform spectroscopic survey (S/N 10) with 3650-7400 Å spectral coverage and median redshift of z = 0.05 showing that AGN fraction is insensitive to the surrounding galaxy density (Carter et al 2001). When it comes to radio AGNs, radio galaxies with infrared (IR) detection in the redshift range 0.55 ≤ z ≤ 1.30 drawn from the Observations of Redshift Evolution in Large-Scale Environments (ORELSE) survey show preference in various local density environments based on their AGN contribution fraction (ratio of AGN luminosity to the total IR luminosity) (Shen et al 2020). In their work, sources with higher AGN contribution fraction show no local environmental preference, while sources with almost no AGN contribution prefer locally denser environments.…”