Detection of a double-peaked H$\alpha$ component from the accretion disc of NGC 4958

Abstract

Active Galactic Nuclei are objects associated with the presence of an accretion disc around supermassive black holes found in the very central region of galaxies with a well-defined bulge. In the optical range of the spectrum, a possible signature of the accretion disc is the presence of a broad double-peaked component that is mostly seen in H$\alpha$. In this paper, we report the detection of a double-peaked feature in the H$\alpha$ line in the nucleus of the galaxy NGC 4958. The narrow line region of this object has an emission that is typical of a LINER galaxy, which is the usual classification for double-peaked emitters. A central broad component, related to the broad line region (BLR) of this object, is seen in H$\alpha$ and also in H$\beta$. We concluded that the double-peaked emission is emitted by a circular relativistic Keplerian disc with an inner radius $\xi_{\rm i}$ = 570$\pm$ 83, an outer radius $\xi_{\rm o}$ = 860$\pm$170 (both in units of $GM_{\rm SMBH}/c^2$), an inclination to the line of sight $i$ = 27.2$^o \pm$0.7$^o$ and a local broadening parameter $\sigma$ = 1310$\pm$70 km s$^{-1}$.