Active Galaxy Nuclei at high redshifts: properties and environment of Type 1 and 2 AGNs

TL;DR

This study compares the host galaxy properties and environments of Type 1 and 2 AGNs at redshifts 0.3 to 1.1, revealing differences in galaxy type, color, and local surroundings that suggest large-scale obscuration mechanisms.

Contribution

It provides a detailed comparative analysis of host galaxy characteristics and environments of Type 1 and 2 AGNs at intermediate redshifts, highlighting potential large-scale obscuration effects.

Findings

Type 1 AGNs are in blue, star-forming, less massive galaxies.

Type 2 AGNs are in more diverse, often redder and more massive environments.

Type 2 AGNs have more neighbors within 100 kpc, indicating different environmental influences.

Abstract

We explore host galaxy properties and environment of a sample of Type 1 and 2 active galactic nuclei (AGN) taken from the COSMOS2015 catalog, within 0.3 $\leq z \leq$ 1.1 selected for their emission in X-rays, optical spectra and SED signatures. We find different properties of host galaxies of distinct AGNs: Type 1 AGNs reside in blue, star-forming and less massive host galaxies compared to Type 2. The majority of the AGNs have intermediate X-ray luminosities, $10^{42}\leq L_X<10^{44}$ \ergs, while only a few have X-ray luminosities ($L_X > 10^{44}$ \ergs) as those observed in QSOs. Non-parametric morphological analysis show that the majority of Type 1 AGN hosts are elliptical or compact galaxies, while Type 2 AGN host present more scatter, from spirals, irregulars and elliptical galaxies. The environment of the different AGN types are similar except at small scales ($r_p<$100 kpc), where Type 2 AGNs have more neighbour galaxies than Type 1s. Galaxies located close to Type 2 AGNs ($\sim$100 kpc) tend to have redder colours, and are more massive compared to the local environment of Type 1s. The observed differences in the environment and host galaxy properties of Type 1 and 2 AGN types show that the obscuration due to the presence of gas and dust may be distributed in larger galactic-scales, possibly originated by galaxy interactions or mergers.