Two galaxies and something bright
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by st_isidore
What's going on in this one?
Posted
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by Budgieye moderator
There is no sign of interaction between the two galaxies.
The photoZ s are different, the spiral is closer.
spiral photoZ 0.0970 http://skyserver.sdss3.org/dr8/en/tools/explore/obj.asp?id=1237666273664827408
bright object is an overlap star in our galaxy , though there might be a galaxy behind it.
edge-on photoZ 0.116 http://skyserver.sdss3.org/dr8/en/tools/explore/obj.asp?id=1237666273664827407
Posted
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by JeanTate in response to Budgieye's comment.
spiral photoZ 0.0970
The DR8 pipeline gives 0.097061±0.026006, i.e. between 0.071 and 0.123 (1 sigma, presumably)
edge-on photoZ 0.116
Likewise, 0.116162±0.018842, i.e. between 0.097 and 0.135 (ditto).
Given the uncertainties in the photoZ's, I don't think it's possible to say which is closer.
bright object is an overlap star in our galaxy , though there might be a galaxy behind it.
The SDSS pipeline thinks there is a galaxy, SDSS J012207.45+225551.3, and gives its photoZ as 0.142377±0.08267 (i.e. between 0.060 and 0.225; 1 sigma).
There's another galaxy of similar appearance, top-right, SDSS J012208.15+225620.3; its photoZ is 0.089272±0.017104 (i.e. between 0.072 and 0.106).
The four photoZ's are consistent with the four galaxies having the same redshift, and so it's possible they make up a fairly tight group. The barred spiral is 'red', as are the other three (as far as one can tell); perhaps star-formation has all-but ceased in all four galaxies? If so, that may be due to depletion of cold (molecular) gas, as a result of earlier interactions.
It's a pity there are no spectra.
Posted
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by zutopian in response to JeanTate's comment.
It's a pity there are no spectra.
Well, there are no spectra for these galaxies in DR8, but there is a spectrum available for one of the galaxies in DR10.:
The spectroscopic redshift of the spiral (red square on below image) is z=0.071 .Posted
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by Budgieye moderator
Thank you JeanTate
and Zutopian thanks for finding out that dr10 has more information.
So spiral galaxy has PhotoZ 0.097±0.026, so maybe 0.071 and the Z is 0.071. Not a bad guess by the PhotoZ
Posted