Active Nucleus of NGC 3393
I'm still on a roll with the active galactic nuclei (AGN) and here is the latest, with thanks to Mitchell Revalski et al. for the list of interesting objects to investigate. I had the usual trouble with this one trying to balance the colors while making the illuminated filaments easy to discern. In many galaxies, the details near the nucleus are not so important to convey, and it is therefore ok if it's all a bright ball. Here, the image is quite dark to accommodate the details in the core.
We're quite used to seeing spiral galaxies with uniformly yellowish cores full of old stars, so when something blue or green is spotted, it seems a bit odd, and that's one of the ways astronomers can find these fascinating galaxies. Such nuances are picked out relatively easily by comparing spectroscopic results from many different galaxies. Spectroscopy is kind of like a fingerprint in light, and whatever spikes and dips in the graph appear tell a story about how far the light traveled, what elements are present, and what's happening to those elements.
Apparently there is not just one black hole at the center of this galaxy, but a pair that are eventually going to merge. Would you believe that spectroscopy can also tell us this? This is moving into the realm of things I don't understand well enough to explain, but here are a number of papers specifically on the case of this galaxy.
arxiv.org/find/all/1/all:+AND+NGC+3393/0/1/0/all/0/1
Data from the following proposal were used to create this image:
The Hosts of Megamaser Disk Galaxies
The representation of filters was a bit difficult, as I used some near-infrared data for around the core, but it didn't extend all the way to the edge, and I had to make up for it with the F814W data there. With that in mind, colors are as follows:
Red: WFC3/IR F160W + WFC3/IR F110W
Green: WFC3/UVIS F814W
Blue: WFC3/UVIS F438W + WFC3/UVIS F336W
North is NOT up. It is 38.67° counter-clockwise from up.