Chandra Observations of Nuclear X-Ray Emission from Low Surface Brightness Galaxies

We present Chandra detections of X-ray emission from the active galactic nuclei (AGN) in two giant low surface brightness (LSB) galaxies, UGC 2936 and UGC 1455. Their X-ray luminosities are 1.8 × 10⁴² ergs s^-1 and 1.1 × 10⁴⁰ ergs s^-1 respectively. Of the two galaxies, UGC 2936 is radio loud. Together with another LSB galaxy UGC 6614 (XMM-Newton archival data) both appear to lie above the X-ray-radio fundamental plane, and their AGN have black hole masses that are low compared to similar galaxies lying on the correlation. However, the bulges in these galaxies are well developed, and we detect diffuse X-ray emission from four of the eight galaxies in our sample. Our results suggest that the bulges of giant LSB galaxies evolve independently of their halo-dominated disks which are low in star formation and disk dynamics. The centers follow an evolutionary path similar to that of bulge-dominated normal galaxies on the Hubble sequence, but the LSB disks remain unevolved. Thus, the bulge and disk evolution are decoupled and so whatever star formation processes produced the bulges did not affect the disks.