Multi-wavelength study of AGN NGC 1365: The obscured AGN

We present a multi-wavelength study of the active nucleus and the off-nuclear X-ray sources in the nearby spiral galaxy, NGC 1365 by using three simultaneous UV/X-ray observations made by AstroSat over a two-month period. The excellent spatial resolution of the UVIT onboard AstroSat has allowed us to reliably separate the intrinsic AGN flux from the host galaxy emission and to correct for the Galactic and internal reddening. We detect the AGN only in the NUV band, the FUV emission is undetectable due to the intrinsic extinction. We find no significant variation in the NUV emission from the AGN. In addition, the UVIT is able to resolve two bright spots at a radius of 7" (∼6.3 Kpc) from the central nucleus in the South-West (SW) direction. In the UVIT image of the entire galaxy, we identify UV counterparts to four Chandra identified X-ray sources. One well-known ultra-luminous X-ray source (ULX) NGC 1365 X2 is identified with its UV counterpart at 86" in the north-east (NE) direction from the active nucleus, implying it might be associated with the stellar activity. Furthermore, we model the AGN torus by using multi-wavelength data in the UV and IR bands and find the location of hot dust in the sublimation zone in the torus using the SKIRTcode. This has helped us to derive the parameters associated with the structure of the AGN dusty torus, such as the half opening angle at 26^o, the location of dust at 0.4 pc from the central nucleus and the inclination angle at 69^o.