I downloaded a Hubble Legacy Atlas mosaic image of the Sombrero Galaxy, and found his galaxy ("Iris"), right where he said it was. From the appearance (and the color figures in his paper), it's a nice strongly barred spiral (something I study a lot). Given the very small angular size (roughly 4 arc seconds in diameter), it's probably hundreds of megaparsecs (well over a billion light years) or more away, and so not associated with the Sombrero Galaxy (which is at a distance of only 9 or 10 megaparsecs).
The object is not in the NASA Extragalactic Database (not surprising for something so mall and distant). If you search near its position in Simbad, you do indeed get "PSO J190.0301-11.6124" (listed as "globular cluster candidate"), just as he found -- but it's crucial to note that the latter object's position differs by about nine arc seconds from the position of the "Iris" galaxy. If you look at the Hubble image, you can see a compact, slightly elliptical object at the position of PSO J190.0301-11.6124; its appearance is consistent with being a "globular cluster candidate" associated with the halo of the Sombrero Galaxy. But all the deductions about possible distances, spectral energy distributions, etc., are vitiated by the misidentification.
So while this is a galaxy, it's way, way beyond the Sombrero Galaxy, and I doubt the claimed X-ray source association, so it's probably not an active galaxy. (Well, it could be, but we probably don't have any evidence for that.)