DRS: HCG 028

Higher redshift object (z = 0.101) within Hickson compact group 28 (z = 0.038) and very close to one of HCG 028 galaxies:

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DRS: ESO 476-008

Three higher redshift galaxies around ESO 476-008:

SDSS J083531.06+245608.1 – very close discordant redshift galaxy pair

There is a higher redshift galaxy (SDSS J083530.81+245558.3, z = 0.267) very close to SDSS J083531.06+245608.1 (z = 0.073, see Figure below). Higher redshift might be projected within the disk of SDSS J083531.06+245608.1.

SDSSJ083531_06_245608_1
Figure 1. The objects with measured redshifts near SDSS J083531.06+245608.1. Image is from Sloan Digital Sky Survey.

Objects and their data

NBR NAME TYPE REDSHIFT MAG SEPARATION
1 SDSS J083531.06+245608.1 galaxy 0.072907 16.5 (g) 0
2 SDSS J083530.81+245558.3 galaxy 0.266687 20.7 (g) 0.175

NED objects within 10′ from SDSS J083531.06+245608.1

ESO 534-021 – very close and bright high redshift companion

Projected very close to ESO 534-021 is higher redshift galaxy ESO-LV 5340211. There seem to be no obvious signs of interaction. It should be noted that further out (at 4.8 and 5.7 angular separation from ESO 534-021) there are two galaxies at similar redshift as ESO-LV 5340211.

One noteworthy thing about this system is that ESO-LV 5340211 is brighter than ESO 534-021 although ESO-LV 5340211 has about 6 times higher redshift (and therefore should be 6 times farther from us than ESO 534-021). I queried NED for galaxies between redshifts 18016 and 18216 (+/- 100 km/s from the redshift of ESO-LV 5340211). From resulting set of galaxies 1942 had nominal magnitude data (apparently) at same band as ESO-LV 5340211. Apparent magnitude of ESO-LV 5340211 is 14.66. Average apparent magnitude of the 1942 galaxies is 17.73. Standard deviation of the apparent magnitude of 1942 galaxies is 1.15. The apparent magnitude of ESO-LV 5340211 therefore deviates by about 2.7 sigmas from the mean apparent magnitude of the galaxies at its redshift.

It should be noted that of the 1942 galaxies, ESO-LV 5340211 is not brightest even if it is among the brightest. There are 13 galaxies that are brighter than ESO-LV 5340211. I checked the 13 galaxies and in one system (2MFGC 12636) there was similar situation that the high redshift galaxy was clearly brighter than nearby lower redshift galaxy. This is perhaps something to study in near future.

ESO534_021
Figure 1. The objects with measured redshifts near ESO 534-021. Size of the image is 5 x 5 arcmin. Image is from Digitized Sky Survey.

Objects and their data

NBR NAME TYPE REDSHIFT MAG SEPARATION
1 ESO 534-021 Sc 0.010474 (3140 km/s) 15.48 0
2 ESO-LV 5340211 galaxy 0.060428 (18116 km/s) 14.66 0.269

NED objects within 10′ from ESO 534-021

UGC 06003 – high redshift galaxy at the edge of the disk

Figure 1 shows UGC 06003 system. A galaxy with clearly higher redshift (object 2 in Figure 1) lies at the edge of UGC 06003’s (object 1 in Figure 1) disk. Apart from closeness to UGC 06003, there doesn’t seem to be any evidence suggesting that this apparent background galaxy would be anything else than a background galaxy.

UGC06003
Figure 1. The objects with measured redshifts near UGC 06003. Size of the image is about 3.4 x 3.4 arcmin. Image is from Sloan Digital Sky Survey.

Object 3 is quite well aligned across UGC 06003 with a similar looking object at the edge of Figure 2, but the object doesn’t have redshift available. In fact, there is a line alignment consisting of object 3, nucleus of object 1 (only roughly at the alignment line), object 2, yellow compact object, and then the object 3 counterpart.

Objects and their data

NBR NAME TYPE REDSHIFT MAG SEPARATION
1 UGC 06003 S0/a 0.019410 (5819 km/s) 14.7 0
2 SDSS J105302.76+043800.8 galaxy 0.239829 20.4 (g) 0.288
3 SDSS J105309.72+043738.6 galaxy 0.463130 21.7 (g) 1.490
4 SDSS J105257.64+043726.9 galaxy 0.019277 17.9 (g) 1.612

NED objects within 10′ from UGC 06003

AM 0213-283 – higher redshift companion galaxy

AM 0213-283 was included to sample of Arp (1981). He reported his measurements of the redshifts in this system and noted:

The central object is a very disturbed spiral. High resolution photographs in the following paper indicate that the companion SE is on the end of a spiral arm, and the companion N is strongly interacting. The spectrum of the companion N shows strong, high excitation emission lines.

Companion N is the object 2 in Figure 2 and Table below. It has discordant redshift compared to the main galaxy (object 1). “Following paper” in quote above is Arp (1982). In that paper, Arp said of this system:

Note particularly the strong tail or jet curving out of companion B to the west. Most important of all, note the short spiral arm segments curving from the center of the disturbed spiral directly to companion B. Regardless of what the redshifts of the other galaxies in the vicinity may turn out to be, the evidence of interaction of companion B with the central galaxy is so strong, in my opinion, that the Δz = +14,021 km s-1 redshift discrepancy must be accepted as real and therefore as principally nonvelocity.

Figure 1 below shows an extract of the high resolution photograph presented in Arp (1982) of this system. I have added the marking of the discordant redshift “companion B”.

AM0213_283_2
Figure 1. AM 0213-283 system from Arp (1982).

Sharp (1985) studied the interaction in the system and found no evidence of interaction between the main galaxy and the discordant redshift companion. Sharp did find evidence of interaction between the main galaxy and the non-discordant redshift companion. Sharp also measured redshifts of some nearby galaxies and found some of them to have similar redshift than the discordant redshift companion. Sharp’s conclusions:

The lack of any dynamical disturbance in the main galaxy near the anomalous companion B, contrasted with the disturbed arm stretching to the nonanomalous companion A, is clear evidence against any interaction between B and the main galaxy. For this reason alone, it is not necessary to postulate that the galaxy called B has a noncosmological redshift. In addition, at least two, and possibly three, nearby galaxies of small angular size have redshifts comparable to that of B, with similar emission-line structure in at least one, and probably two, of them. It seems that this system is a coincidental projection of a foreground interacting pair on a distant background group.

Notes

Figure 2 shows the objects with measured redshifts in the AM 0213-283 field. Object 7 also has similar redshift to AM 0213-283, so there seems to be a galaxy group at that redshift and not just an interacting pair.

Object 4 doesn’t belong to either galaxy group – it has redshift of about z = 0.3.

AM0213_283
Figure 2. The objects with measured redshifts near AM 0213-283. Size of the image is about 7.5 x 7.5 arcmin. Image is from Digitized Sky Survey.

Objects and their data

NBR NAME TYPE REDSHIFT MAG SEPARATION
1 AM 0213-283 Sc 0.035161 (10541 km/s) 15.11 0
2 [A81] 021344-2833N galaxy 0.082040 (24595 km/s) 0.231
3 [A81] 021344-2833SE galaxy 0.035948 (10777 km/s) 17.0 (r) 0.447
4 2QZ J021551.8-282321 galaxy 0.298000 20.29 0.982
5 2dFGRS S308Z130 galaxy 0.082200 (24643 km/s) 19.05 0.997
6 2dFGRS S307Z023 galaxy 0.082000 (24583 km/s) 19.20 1.087
7 LEDA 3210176 galaxy 0.035736 (10713 km/s) 17.96 1.211
8 2dFGRS S308Z127 galaxy 0.082914 (24857 km/s) 19.38 1.904

NED objects with measured redshifts within 10′ from AM 0213-283

References

Arp, H., 1981, Astrophysical Journal Supplement Series, vol. 46, May 1981, p. 75-112, “Spectroscopic measures of galaxies, their companions, and peculiar galaxies in the southern hemisphere”
Arp, H., 1982, Astrophysical Journal, Part 1, vol. 256, May 1, 1982, p. 54-74, “Characteristics of companion galaxies”
Sharp, N. A., 1985, Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 297, Oct. 1, 1985, p. 90-97, “Anomalous redshift companion galaxies – 0213-2836”

HCG 027 – galaxy line that couldn’t decide its redshift

Hickson Compact Group (HCG) number 27 is a line of five or six galaxies. There is only 5 objects within HCG 027 with redshift available in NED. Hickson et al. (1992) reported a sixth redshift for the system. They have there an object called “27f” with a redshift of 26100 km/s, while originally group had only five members 27a-e. This is object 6 in Figure 1 and table below. This additional galaxy is somewhat off from the line of five other galaxies.

HCG 027 was included to the sample of Mendes de Oliveira (1995) who studied discordant redshift objects in Hickson Compact Groups, and concluded that the results of the study supported the view of a cosmological origin for galaxy redshifts. However, Mendes de Oliveira found that “the distribution of positions for the discordant galaxies in quintets, however, is more centrally concentrated than that predicted for a uniform distribution of field interlopers,” and offered gravitational lensing as an explanation for the observation. Here we don’t explore this general compact group situation much further, and we concentrate on the HCG 027, but for another view of the general situation, an interested reader might take a look at Sulentic (1997).

So far, I haven’t found any paper that discusses HCG 027 as an individual discordant redshift system. The discordant redshift situation in the system is such that in the line there are two galaxies having radial velocity of cz ~ 18500 km/s, while three galaxies (and the additional sixth galaxy) have cz ~ 26000. In the traditional view this system is interpreted so that a pair of galaxies at cz ~ 18500 and group of background galaxies at cz ~ 26000 are accidentally aligned so that they seem to form a line (or a chain).

Figure 1 shows the objects with measured redshifts in the field of HCG 027, and data for the objects is given in the table below.

hcg027
Figure 1. Objects with measured redshifts in/near HCG 027. Image is from Simbad.

Objects and their data

NBR NAME TYPE REDSHIFT MAG SEPARATION
1 PGC 014863 SBc 0.061756 (18514 km/s) 16.44 0
2 2MASX J04192158-1142395 S0 0.086873 (26044 km/s) 18.74 0.910
3 PGC 014861 S0a 0.087581 (26256 km/s) 18.02 1.010
4 PGC 014870 Sa 0.087901 (26352 km/s) 17.50 1.813
5 PGC 014873 Sb 0.061176 (18340 km/s) 17.01 2.796
6 APMUKS(BJ) B041656.98-114846.3 S0 (26100 km/s) 19.46 0.519

NED objects within 10′ from HCG 027

References

Hickson et al., 1992, ApJ, 399, 2, 353-367, “Dynamical properties of compact groups of galaxies”

Mendes de Oliveira, C., 1995, MNRAS, 273, 1, 139-145, “The nature of discordant redshift galaxies in compact groups”

Sulentic, Jack W., 1997, ApJ, 482, 640, “The Twin Paradoxes of Compact Groups: Discordant Excess Muted but the Dynamical Puzzle Persists”