Seyfert galaxies such as NGC 5793 are known to house megamasers. Megamasers can have a luminosity of thousands of times greater than the Sun.[1]Neutral hydrogen has been detected against the galactic nucleus. This means that NGC 5793 has an estimated HI cloud size of ≈15 pc and an estimated atomic gas density of ≈200 cm -3.[8]
^ abcdeHagiwara, Y.; et al. (August 2000). "Probing circumnuclear molecular gas in NGC 5793 with OH absorption". Astronomy and Astrophysics. 360: 49-56. Bibcode:2000A&A...360...49H.