Overlapping IR Sources
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by
mdwilber
The SDSS image very nicely shows that the IR source in this image is actually two galaxies overlapping (not sure if they're merging). Is there any way to tell which galaxy is emitting the Radio?
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by
JeanTate
in response to mdwilber's comment.
This is a very nice #overlap! 😃 I wonder if it's in the GZ overlaps catalog?
There are two objects with SDSS spectra:
The smaller galaxy's nucleus seems to be within the spectroscope's fiber, so it should strongly hint at whether it contains an AGN; the spectroscopic pipeline classified it as 'STARFORMING', with a redshift of 0.050, so I guess it's not an AGN.
The other spectrum is of the white star which happen to inconveniently lie - line of sight - close to the nucleus of the bigger galaxy. However, it does have a series of very prominent, unmarked emission lines, pretty much where you'd expect the H-alpha, [NII], [SII], H-beta, and [OII] lines to be, if they were redshifted by ~0.051 (curiously, no sign of the [OIII] lines). These almost certainly originate in the galaxy's nucleus; whether the spectrum data can be analyzed to tell if the nucleus is an AGN or not, I couldn't say for sure (but my guess is that it likely could).
Now I'm going to change my mind: the two galaxies have redshifts very close to each other, so they're more likely interacting (though not necessarily merging) than overlapping, and that interaction may have driven one nucleus to become active ... hence the radio emission.
Here's the star's spectrum, in reduced resolution:
Posted