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 ${\hat{I}}^3$-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 ${\hat{I}}^3$-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 ${\hat{I}}^3$-ray source and find that PKS 1007+142 is in close proximity to the ${\hat{I}}^3$-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 6.6\ddot{I}ƒ$). PKS 1007+142 exhibits a steep power-law spectrum in the 0.1--300 GeV band, with a photon spectral index ($\hat{I}{“}_{\hat{I}}^3$) of $2.86\pm 0.17$. The average flux in the considered time interval is $(2.14\pm 0.34)\times 10^{-12}\mathrm{erg}\mathrm{c}{\mathrm{m}}^{-2}{\mathrm{s}}^{-1}$. Comparing PKS 1007+142 with other ${\hat{I}}^3$-ray emitting AGNs in both the $L_{\hat{I}}^3-\hat{I}{“}_{\hat{I}}^3$ and $L_{\hat{I}}^3-L_{1.4GHz}$ planes, it shows a softer ${\hat{I}}^3$-ray spectrum and lower luminosity compared to other ${\hat{I}}^3$-ray emitting CSSs. Furthermore, the possible origins of ${\hat{I}}^3$-ray in PKS 1007+142 are also discussed.

11 pages, 5 figures, 2 tables, accepted for publication in ApJ