Probing properties of nearly two-hundred new active galactic nuclei

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 $0.3_{-0.14}^{+0.16}$ to $2.54_{-0.13}^{+0.14}$. Particularly, 76 of these AGNs display discernible levels of intrinsic absorption, after considering the Galactic absorption. The column densities associated with this local absorption ($n_{\mathrm{H}}^{\mathrm{local}}$) are within a range of $\sim 10^{19}-10^{22}\mathrm{c}{\mathrm{m}}^{-2}$. We study the cosmological evolution of AGNs using the variation of $n_{\mathrm{H}}^{\mathrm{local}}$ 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 ($L_{\mathrm{B}}^{\mathrm{intr}}$) ranging from $4.59_{-0.41}^{+0.41}\times 10^{42}$ to $2.4_{-0.12}^{+0.12}\times 10^{46}{\mathrm{erg}\mathrm{s}}^{-1}$ 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.

15 pages, 12 figures, 1 table, accepted for publication in Monthly Notices of the Royal Astronomical Society

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