The AGN and Gas Disk in the Low Surface Brightness Galaxy PGC045080

TL;DR

This study investigates the AGN activity and gas dynamics in the low surface brightness galaxy PGC 045080 through radio and optical observations, revealing potential weak AGN presence and a warped, lopsided HI disk with a flat rotation curve.

Contribution

First detailed radio and optical analysis of PGC 045080 showing possible weak AGN activity and complex gas dynamics in a low surface brightness galaxy.

Findings

Detected extended radio emission with lobes indicating AGN activity.

HI disk is warped and lopsided with a flat rotation curve of ~190 km/s.

Optical spectrum shows no strong AGN emission lines, but non-thermal radio emission suggests hidden AGN.

Abstract

We present radio observations and optical spectroscopy of the giant low surface brightness (LSB) galaxy PGC 045080 (or 1300+0144). PGC 045080 is a moderately distant galaxy having a highly inclined optical disk and massive HI gas content. Radio continuum observations of the galaxy were carried out at 320 MHz, 610 MHz and 1.4 GHz. Continuum emission was detected and mapped in the galaxy. The emission appears extended over the inner disk at all three frequencies. At 1.4 GHz and 610 MHz it appears to have two distinct lobes. We also did optical spectroscopy of the galaxy nucleus; the spectrum did not show any strong emission lines associated with AGN activity but the presence of a weak AGN cannot be ruled out. Furthermore, comparison of the H$\alpha$ flux and radio continuum at 1.4 GHz suggests that a significant fraction of the emission is non-thermal in nature. Hence we conclude that a weak or hidden AGN may be present in PGC 045080. The extended radio emission represents lobes/jets from the AGN. These observations show that although LSB galaxies are metal poor and have very little star formation, their centers can host significant AGN activity. We also mapped the HI gas disk and velocity field in PGC 045080. The HI disk extends well beyond the optical disk and appears warped. In the HI intensity maps, the disk appears distinctly lopsided. The velocity field is disturbed on the lopsided side of the disk but is fairly uniform in the other half. We derived the HI rotation curve for the galaxy from the velocity field. The rotation curve has a flat rotation speed of ~ 190 km/s.