UGC 05020 – High-z companion, QSO, pair, line

Arp (1980) discussed the companion galaxies of NGC 2859. One of the four discussed companions is UGC 05020 (object 1 in Figure 1). Specifically, Arp studied quasars near companion galaxies. He noted that UGC 05020 had an ultraviolet excess object in its vicinity. Arp studied it spectroscopically, and it turned out to be a quasar (object 2). Arp calculated the probability of 0.01 for a background quasar falling so close to UGC 05020 by chance.

Arp also noted the presence of the apparent companion galaxy (object 3). He said:

…, it is noticeable that a second galaxy, nearly as bright, lies close by to the southwest. The comparable brightness, the closeness, and above all the signs of interaction naturally led to the assumption that these two galaxies were at the same distance. It was a considerable surprise therefore when the spectrum of this second component clearly exhibited a much larger redshift of z = 7442 km s-1.

Arp then mentioned that the redshift difference of UGC 05020 and object 3 is similar to the redshift differences found in Stephan’s quintet. He studied the spectrum of object 3 and noted that some spectral features didn’t fit to a large background galaxy and that some features were similar to typical small companion galaxies. Arp concluded:

We see that there are several kinds of evidence which indicate that the z = 7,442 km s-1 galaxy is also physically associated with an NGC 2859 companion and therefore at the same distance.

New evidence

Objects 6 and 7 are roughly aligned across UGC 05020. The alignment is quite closely along the minor axis of UGC 05020. Objects 6 and 7 have almost the same redshift, but not quite close enough to be clearly a galaxy pair (the radial velocity difference is about 2700 km/s). Their distance from UGC 05020 is similar, so is their appearance, and their G band magnitude is the same.

Objects 2 and 10 form a line that is very accurately aligned with the nucleus of UGC 05020. They are both quasars with redshifts over 2. Lower redshift quasar is closer to UGC 05020, though, which would go against decreasing redshift hypothesis. Object 5 also falls close to the line, and it also is a quasar but with lower redshift. It is interesting to note that within 9 arcminutes from UGC 05020 we have three objects that are labelled as QSO’s in NED and all those three are quite accurately in same direction from UGC 05020. There’s a fourth quasar (SDSS J092548.59+344809.1, z = 0.5405) slightly outside of the field shown in Figure 1. It is not exactly in the same direction, but quite close (it is roughly in the same direction as object 6). On the other side, object 4 also falls to the line, but is not similar to other objects.

In summary, we have here:

– a quasar that is very close to the main galaxy.
– a higher redshift companion galaxy, and the situation is very similar to that of NGC 1232 and NGC 1232A.
– a pair of very similar higher redshift objects aligned along the minor axis of the main galaxy.
– a line of quasars from the main galaxy containing all the nearby quasars.

Notes

There’s no sign of a bridge between UGC 05020 and object 3 or object 2 in DSS os SDSS images.


Figure 1. Objects with available redshift near UGC 05020 (all objects within 9 arcmin are presented). The arrow at lower right points to the approximate direction of NGC 2859. Size of the image is 15 x 15 arcmin. Image is from Digitized Sky Survey (POSS2/UKSTU Blue) and it has been adjusted for brightness and contrast to bring out fainter objects more clearly.

Objects and their data

NBR NAME TYPE REDSHIFT (cz) MAG SEPARATION
1 UGC 05020 Scd 0.005420 (1625 km/s) 14.9 (g) 0
2 NGC 2859 U2 QSO 2.250000 19.2 (g) 1.008
3 MCG +06-21-036 Sc 0.024177 (7248 km/s) 15.8 (g) 1.607
4 SDSS J092616.68+343708.6 galaxy 0.150899 18.8 (g) 3.744
5 SDSS J092542.32+344108.6 QSO 1.066320 16.5 (g) 4.390
6 SDSS J092549.67+344439.7 galaxy 0.080995 (24282 km/s) 17.7 (g) 5.972
7 SDSS J092606.74+343240.7 galaxy 0.071833 (21535 km/s) 17.7 (g) 6.616
8 SDSS J092527.26+343917.7 galaxy 0.235684 18.8 (g) 7.039
9 SDSS J092533.04+343441.0 galaxy 0.017219 (5162 km/s) 17.0 (g) 7.398
10 SDSS J092527.51+344357.7 QSO 2.784200 20.4 (g) 8.449

NED objects within 10′ from NGC 0010.

SDSS image of the system.

References

Arp, 1980, ApJ, 240, 415, “High-redshift objects near the companion galaxies to NGC 2859”

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