Study of γ-ray Emission from a Compact Radio Galaxy with the Fermi Large Area Telescope

Abstract

The radio galaxy PKS 1007+142 is classified as a compact steep-spectrum source (CSS) and belongs to the class of young Active Galactic Nuclei (AGNs). In this paper, we investigate the $γ$-ray emission from this CSS by conducting a comprehensive analysis of the 15 yr Fermi Large Area Telescope (Fermi-LAT) observation data. The Fermi-LAT latest Source Catalog, 4FGL-DR4, includes an unassociated $γ$-ray source, 4FGL J1010.0+1416, located at 0.24° away from the radio position of PKS 1007+142. Using the 15 yr Fermi-LAT observation data, we re-estimate the best-fit position of the $γ$-ray source and find that PKS 1007+142 is in close proximity to the $γ$-ray source and falls within its 68% error circle. Therefore, we conclude that PKS 1007+142 is the most plausible counterpart to the unassociated LAT source with a detection test statistics (TS) $\sim$43.4 ($\sim 6.6σ$). PKS 1007+142 exhibits a steep power-law spectrum in the 0.1--300 GeV band, with a photon spectral index ($Γ_γ$) of $2.86\pm0.17$. The average flux in the considered time interval is $\rm (2.14\pm0.34)\times10^{-12}\ erg\ cm^{-2}\ s^{-1}$. Comparing PKS 1007+142 with other $γ$-ray emitting AGNs in both the $L_γ-Γ_γ$ and $L_γ-L_{\rm 1.4GHz}$ planes, it shows a softer $γ$-ray spectrum and lower luminosity compared to other $γ$-ray emitting CSSs. Furthermore, the possible origins of $γ$-ray in PKS 1007+142 are also discussed.