Probing properties of nearly two-hundred new active galactic nuclei

TL;DR

This study analyzes the X-ray spectral properties of 198 newly identified AGNs, examining their spectral signatures, absorption features, and evolution with redshift, revealing no significant cosmological evolution but a possible deficit of hard sources at high redshift.

Contribution

First comprehensive analysis of X-ray spectra for nearly two hundred new AGNs, including spectral characterization, absorption measurement, and evolution study with redshift.

Findings

76 AGNs show intrinsic absorption with $n_{H}^{local}$ up to 10^{22} cm^{-2}

No significant cosmological evolution of spectral properties observed

Sample spans luminosities from 4.59e42 to 2.4e46 erg/s with peak at redshift 1.84

Abstract

We present a comprehensive analysis of the X-ray spectral properties of 198 newly identified active galactic nuclei (AGNs), leveraging archival data from the {\it Chandra} X-ray Observatory. All these AGNs exhibit a powerlaw spectral signature spanning a broad energy range of $0.5-7.0$ keV, characterized by the photon index ($\Gamma$) values ranging from $0.3^{+0.16}_{-0.14}$ to $2.54^{+0.14}_{-0.13}$. Particularly, 76 of these AGNs display discernible levels of intrinsic absorption, after considering the Galactic absorption. The column densities associated with this local absorption ($n_{\rm H}^{\rm local}$) are within a range of $\sim 10^{19} - 10^{22}\ {\rm cm^{-2}}$. We study the cosmological evolution of AGNs using the variation of $n_{\rm H}^{\rm local}$ and $\Gamma$ with their estimated redshift. The intrinsic spectral signature did not reveal any significant cosmological evolution; however, a deficit of hard sources at high redshift is possibly intrinsic. Our sample covers several decades of broadband intrinsic luminosity ($L_{\rm B}^{\rm intr}$) ranging from $4.59^{+0.41}_{-0.41} \times 10^{42}$ to $2.4^{+0.12}_{-0.12} \times 10^{46}\, {\rm erg~s}^{-1}$ with peak at 1.84 redshift. We also investigate the hardness-luminosity diagram (HLD) to further probe the AGNs. We conduct a sanity check by applying our findings to known AGNs, and the results are consistent with our observations.