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

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 distantgalaxy having a highly inclined optical disk and massive HI gas content. Radio continuumobservations 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 extendedover the inner disk at all three frequencies. At 1.4 GHz and 610 MHz it appearsto have two distinct lobes. We also did optical spectroscopy of the galaxy nucleus; thespectrum did not show any strong emission lines associated with AGN activity butthe presence of a weak AGN cannot be ruled out. Furthermore, comparison of theH flux and radio continuum at 1.4 GHz suggests that a significant fraction of theemission is non-thermal in nature. Hence we conclude that a weak or hidden AGNmay be present in PGC 045080. The extended radio emission represents lobes/jetsfrom the AGN. These observations show that although LSB galaxies are metal poorand 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 extendswell beyond the optical disk and appears warped. In the HI intensity maps, thedisk appears distinctly lopsided. The velocity field is disturbed on the lopsided sideof the disk but is fairly uniform in the other half. We derived the HI rotation curvefor the galaxy from the velocity field. The rotation curve has a flat rotation speed of 190km s−1.