High redshift object in front of low redshift object

Note: This is part of my old website content that I’m transferring here.


M84 E1;LERG LINER 0.00354
QSO B1222+131 quasar 1.250000

NGC 383

  • Association of 1E 0104 and NGC 383

    • 1E 0104 has X-ray tail that points toward NGC 383. [1]

  • Association of quasar B and 1E 0104

    • Quasar B is within the optical boundaries of one of 1E 0104 galaxies. [1]

      • Quasar B shows no absorption lines at z = 0.11 as it should if it would be in 1E
        0104’s background. [1]

  • General information

    • NGC 383 has three companion galaxies, NGC 379, NGC 380 and NGC 385. [1]

  • References

NGC 383 SA0-: LERG 0.01700
NGC 379 S0 0.01861
NGC 380 E2 0.01476
NGC 385 SA0-: 0.01659
1E 0104 galaxy group 0.11 [1]
B quasar 2.027 [1]

NGC 450

NGC 450 NED01 SAB(s)cd: 0.00587
UGC 807 S 0.03813

NGC 1199

NGC 1199 E3 0.00857
[A81] 030118-1549SW compact object 0.044400

NGC 1232

  • Association of NGC 1232A and NGC 1232

    • A companion galaxy NGC 1232A is on the end of the spiral arm of NGC 1232. [1]
    • NGC 1232A doesn’t seem to be at it’s redshift distance. [1]

      • The degree of resolution is quite similar in NGC 1232 and NGC 1232A. [1]
      • The apparent size of H II regions is quite similar in NGC 1232 and NGC 1232A. [1]
      • Distance modulus (from luminosity index and apparent magnitude) of NGC 1232A is
        bigger than in NGC 1232. [1]
      • Absolute magnitude of NGC 1232A seems too faint for such a well-developed barred
        spiral to be at NGC 1232 distance. [1]

        • Galaxies of such low surface brightness and irregularity as NGC 1232A are known
          to be of low luminosity. [1]

      • If NGC 1232A were in the background, it would be isolated. There is no obvious
        background group to which it belongs. Type of NGC 1232A is such that it isn’t
        expected to appear isolated in space. [1]

  • Association of NGC 1232B and NGC 1232

    • There is another companion galaxy, NGC 1232B, in the disk of NGC 1232. [1]

      • NGC 1232B doesn’t appear to be dimmed. [1]
      • NGC 1232B doesn’t appear to be reddened. [1]

  • References

NGC 1232 SAB(rs)c 0.00535
NGC 1232A SB(s)m 0.02167
NGC 1232B ? 0.093 [1]

NGC 1275

NGC 1275 cD;pec;NLRG Sy2 0.01756
? filaments 0.027 [1]
? intermediate velocity gas 0.023, 0.024 [11]

NGC 3718

NGC 3718 SB(s)a pec;Sy1 LINER 0.00331
VV 150 galaxy group 0.02738
VV 150a SB0 0.02642
VV 150b (R’)S0/A pec: Sy2 0.02705
VV 150c SA(s)0/a pec: Sy2 0.02784

NGC 4698

NGC 4698 SA(s)ab Sy2 0.00334
XMMU J124825.9+083020 BLLAC 0.43000
RXJ1248.4+0831 Sy 0.12000

NGC 5296

  • Association of NGC 5296 BSO1 and NGC 5296

    • Luminous filament from NGC 5296 points toward NGC 5296 BSO1. [1]

  • Association of [A76] G1 and NGC 5296

    • [A76] G1 may be interacting with NGC 5296. [1]

      • [A76] G1 appears to be disturbed. [1]

    • [A76] G1 is embedded in the outskirts of NGC 5296. [1]

      • [A76] G1 doesn’t seem to be obscured by NGC 5296. [1]
      • [A76] G1 has only one peculiar arm that has a dark lane just outside of it. The
        lane seems to be absorbing the light of NGC 5296. [1]

        • Appearance of absorbtion could be just a photographic effect. [1]

          • Photographic effect should also be seen elsewhere in the photographic plate,
            it is not seen. [1]

        • Cusp of material could be missing from NGC 5296 just in the place where
          absorbtion is seen. [1]

          • NGC 5296 has smooth outline. [1]

      • Point where [A76] G1 and NGC 5296 are closest to each other has diminished
        brightness. If [A76] G1 would be behind NGC 5296, that point should have enhanced
        brightness. [1]
      • Based on surface brightness analysis, the silhouetting seems to be an illusion due
        to complex structure of NGC 5296. [3]

  • Notes

    • NGC 5296 is a companion to NGC 5297, and there’s luminous bridge between them. [1]
    • Radio observations don’t show anything special in NGC 5296 field. [2]

  • References

NGC 5296 S0+: 0.00742
NGC 5297 SAB(s)c: sp 0.00804
NGC 5296 BSO1 QSO 0.96300
[A76] G1 peculiar 0.08630

NGC 7319

  • Association of CXOU J223603.6+335825 and NGC 7319

    • ULX/QSO (CXOU J223603.6+335825) seems to be in front of NGC 7319. [1]

      • ULX/QSO is in very dense part of the NGC 7319 disc. If it would be background
        object, we shouldn’t see it through the disc. [1]
      • ULX/QSO is not reddened. [1]

    • ULX/QSO seems to be interacting strongly with the interstellar gas in the disc of NGC
      7319. [1]
    • NGC 7319 has outflow in the direction of the ULX/QSO. [1]
    • NGC 7319 has luminous filament to the direction of the ULX/QSO. [1]

      • Filament is almost connected to the ULX/QSO. [1]
      • The filament is bluer than the body of the galaxy. [1]

  • Notes

    • NGC 7319 belongs to NGC 7331 DRS and NGC 7320 DRS.

  • References

NGC 7319 SB(s)bc pec Sy2 0.0225
CXOU J223603.6+335825 QSO 2.114000

NGC 7603

NGC 7603 SA(rs)b: pec Sy1.5 0.02952
NGC 7603B Sy1 0.05574
NGC 7603:[LG2002] 2 ? 0.24300
NGC 7603:[LG2002] 3 ? 0.39100
? bridge 0.030 [2]

SBS 1543+593

SBS 1543+593 dwarf galaxy 0.00900
HS 1543+5921 QSO 0.80700

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.

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

Objects and their data

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.

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

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.

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

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”.

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.


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.

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

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


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.

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

Objects and their data

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


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”

IC 2402 – QSOs, Galaxy, and a Radio filament

Note that this is a new version of IC 2402 post, original can be found here. There are some new redshifts in SDSS DR9 for this system (5 new QSOs), so it was time to do this post again. Only changes are in Notes section and in Figure 1 and Table 1.

Olsen (1970) studied the positions of 4C radio sources, and noted about radio source 4C 31.32:

The primary identification is the *13.5-mag E galaxy, NGC 2402 [should be IC 2402], which appears 3″E and 34″S of the radio position. An 18-mag blue stellar object appears 30″W and 17″N of the radio position.

Grueff & Vigotti (1974) studied the system further:

…the starlike object noted by Olsen was being studied by Schmidt, who found it to be a Quasar with a red-shift of 1.8 (Schmidt, private communication). The separation between the center of the galaxy and the Quasar is only less than a minute of arc.

In order to study the identification of the radio source, and the possible relationship between the galaxy and the quasar, they took new image and a radio map of the system. They found:

An inspection of Fig. 1 reveals that we are probably dealing with a double radio source with the two components symmetrical on each side of the parent galaxy, and showing considerable complexity.


There seems to be no evidence of any physical relation between the Quasar (marked by the arrow) and the radiosource.

They also noted that the double sided radiosource is normal in its dimensions at the redshift distance of IC 2402. New radio observations of the system was reported by van Breugel (1980), who noted some hot spots in the distribution of the radio material. Arp (1987) noted the situation:

As an example of a quasar connected to a galaxy by a radio filament we show in Fig. 8. In the northern lobe of the radio galaxy 0844+31 there is a hot spot only 5 arc sec distant from a high redshift, bright apparent magnitude quasar.

0844+31 being the IC 2402. He also gave probabilities for the association:

The chance of a quasar this bright falling this close to the hot spot is only 3×10-6. Even if we take the significant distance to be from the quasar to the center of the lobe, a distance of 19 arc sec, the chance is only 4×10-5.


Figure 1 shows the objects with available redshifts in IC 2402 field. I have kept the old numbering from the first version and I have added new SDSS DR9 objects numbered as S1, S2, S3,…

Objects 4 and 8 in Fig. 1 are quite well aligned across IC 2402.

Objects S1 and S2, both QSOs, are aligned across IC 2402. Object S2 is very close to a galaxy which has similar size as nearby object 3.

Objects 2 and S4, both QSOs, are aligned across IC 2402.

Objects 3, 6, 7, 9, and 10 in Fig. 1 are objects with similar redshift to IC 2402.

Figure 1. The objects with measured redshifts near of IC 2402. Size of the image is 10 x 10 arcmin. Image is from Sloan Digital Sky Survey (SDSS). Click image for larger version.

Objects and their data

1 IC 2402 galaxy, AGN 0.067373 14.9 (G) 0
2 [HB89] 0844+319 QSO 1.838570 19.1 (G) 1.001
S1 SDSS J084804.07+314703.8 QSO 1.04432 20.9 (G) 1.072
3 SDSS J084750.95+314755.7 galaxy 0.066607 18.2 (G) 1.893
4 SDSS J084800.96+314516.1 galaxy 0.143678 18.5 (G) 1.914
S2 SDSS J084749.38+314729.9 QSO 0.55262 21.6 (G) 2.084
5 SDSS J084809.99+314607.2 galaxy 0.144116 18.2 (G) 2.540
6 SDSS J084753.20+314437.5 galaxy 0.068520 18.1 (G) 2.803
S3 SDSS J084807.52+314912.9 QSO 1.70557 21.2 (G)
7 SDSS J084750.32+315119.2 galaxy 0.070321 17.3 (G) 4.574
8 SDSS J084755.36+315142.7 galaxy 0.375645 21.1 (G) 4.640
9 SDSS J084814.81+315054.5 galaxy 0.065922 18.5 (G) 5.044
10 SDSS J084738.84+315032.8 galaxy 0.068930 17.7 (G) 5.481
S4 SDSS J084811.42+314256.5 QSO 1.45813 20.9 (G)
S5 SDSS J084820.17+315014.9 QSO 1.33695 20.6 (G)

Objects in NED within 10 arcmin (and with redshift available).
SDSS image of the system.


Arp, 1987, IAUS, 124, 479, “Observations requiring a non-standard approach”

Grueff & Vigotti, 1974, A&A, 35, 491, “On the radiosource 0844 + 31 B”

Olsen, 1970, AJ, 75, 764, “Optical identification of radio source selected from the 4C catalogue”

van Breugel, 1980, A&A, 81, 275, “Multifrequency Observations of Extended Radio Galaxies – Part Two – B0844+31”

AM 0058-402 – bridged discordant redshift objects

Arp (1980) reported three new discordant redshift cases. One of the reported systems was AM 0058-402. This system has main galaxy (object 1) connected to an apparent companion (object 2) galaxy with a spiral arm-like bridge. Problem is that main galaxy has radial velocity cz = 6773 km/s while the companion has radial velocity 16415 km/s, so the difference in these velocities is too large for them to be physically connected in traditional view. Arp says this about the bridge:

On this latter higher-resolution photograph, it is seen that the connecting filament is in the nature of a spiral arm emerging from the larger galaxy. But the arm is much longer than any of the other arms in the galaxy, emerges orthogonally rather than tangentially from the main body, and terminates directly at the center of the companion.


Figure 1 shows nearest objects with measured redshifts in AM 0058-402 field.

– The bridged object, object 2, seems to belong to a group of galaxies at about 16500 km/s. Object 19 (which is just outside the pictured field) is brightest and seemingly largest of the galaxies in this group, and might be the main galaxy of the group. Objects in the group (within this field) are 2, 6, 7, 8, 11, 16, and 19.

– There seems to be another group at redshift z = 0.177. This group seems to be overlapping with the 16500 km/s group described above. Objects in this group are 9, 10, 13, 14, and 17.

– Objects 12 and 15 are roughly aligned across object 1. Object 3 also falls to their alignment line.

Figure 2. The objects with measured redshifts near AM 0058-402. Size of the image is about 15 x 15 arcmin. Image is from Digitized Sky Survey. Click for larger version of the image.

Objects and their data

1 MCG -07-03-005 spiral 0.022592 (6773 km/s) 14.5 0
2 PGC 003633 galaxy 0.054755 (16415 km/s) 15.6 (I) 0.426
3 ESP 40160 galaxy 0.105483 18.60 0.948
4 ESP 38602 galaxy 0.223564 19.21 2.551
5 ESP 38632 galaxy 0.115486 19.13 3.021
6 ESP 38526 galaxy 0.055215 (16553 km/s) 19.18 3.706
7 ESP 40626 galaxy 0.053981 (16183 km/s) 17.33 4.657
8 ESP 40625 galaxy 0.054845 (16442 km/s) 17.86 6.093
9 ESP 40187 galaxy 0.179334 18.29 6.479
10 ESP 40161 galaxy 0.177549 18.65 6.733
11 ESP 38528 galaxy 0.055582 (16663 km/s) 18.84 6.858
12 ESP 38482 galaxy 0.188030 19.38 6.875
13 ESP 38605 galaxy 0.176455 18.94 6.912
14 ESP 38669 galaxy 0.177936 18.99 7.119
15 ESP 38704 galaxy 0.107267 19.03 7.224
16 ESP 38529 galaxy 0.054858 (16446 km/s) 18.84 7.258
17 ESP 40188 galaxy 0.179994 18.72 7.799
18 [VCV2001] J010031.5-401351 QSO 0.610000 17.90 7.958
19 LEDA 101141 E 0.054948 (16473 km/s) 16.17 7.961
20 ESP 38483 galaxy 0.159123 18.95 8.449

NED objects within 10′ from AM 0058-402


Arp, H. 1980, Astrophysical Journal, Part 1, vol. 239, July 15, 1980, p. 469-471, 473, 474, “Three new cases of galaxies with large discrepant redshifts”

NGC 4460 – high redshift object within disk

It seems that NGC 4460 system hasn’t been discussed as discordant redshift system before. NGC 4460 has a high redshift object (object 2, z = 0.173) within its disk. NED says this about object 2: “This is part of the galaxy NGC 4460. Either z or Dxd is incorrect.” Quite confident statement considering that object 2’s appearance is not something you would expect to see in NGC 4460’s disk, and fits rather well with a background galaxy shining through NGC 4460’s disk.

Object 3 also has discordant redshift compared to NGC 4460, and it is very close to NGC 4460. There’s nothing apparent to suggest interaction in the system, so this seems to be genuine background object (also the appearance of object 3 suggests background galaxy in my opinion).


Only two additional redshifts are available in the field despite it being within SDSS coverage area. Object 4 has similar redshift to NGC 4460, so apparently it is an object of NGC 4460’s disk. Additionally there’s one star in the field. Both of these redshifts are in SDSS DR9 and they are not yet available in NED.

Figure 1. The objects with measured redshifts near NGC 4460. Size of the image is about 6.8 x 6.8 arcmin. Image is from Sloan Digital Sky Survey. Click for larger version of the image.

Objects and their data

1 NGC 4460 SB(s)0+? sp 0.001634 (490 km/s) 12.26 0
2 SDSS J122848.76+445208.7 galaxy 0.172950 15.2 (g) 0.638
3 SDSS J122842.63+445230.3 galaxy 0.066883 (20051 km/s) 18.0 (g) 0.833
4 SDSS J122841.41+445054.9 part of galaxy (544 km/s) 20.92 (g) 1.188

NED objects with measured redshifts within 10′ from NGC 4460

2dFGRS N379Z082 – another case of high redshift galaxy within disk

Apparently 2dFGRS N379Z082 system has not been discussed as discordant redshift system before. The main galaxy (2dFGRS N379Z082, object 1) has redshift of z = 0.08 (cz ~ 24000 km/s). Within its disk there is object 2 that has redshift of z = 0.163. These redshifts suggest, if interpreted traditionally, that object 2 is a background object that has been accidentally positioned behind the main galaxy and shining through the main galaxy disk.

Figure 1. Closeup of 2dFGRS N379Z082 system. Image is from Sloan Digital Sky Survey.

There are lot of galaxies in the universe so we would expect to see some of them to fall close to same lines of sight, so we can’t really say if the position of the high redshift object within the main galaxy disk is unexpected. However, Figure 2 below shows that the field near this system has lot of objects at the redshift of main galaxy (cz ~ 24000 km/s) and at the redshift of object 2 (cz ~ 49000 km/s). In fact, it seems that if you would have to get two of all these objects shown very close together (such as the situation with objects 1 and 2), you would be most likely to succeed in that with objects having radial velocities of 24000 and 49000 km/s, because there seems to be most objects at those two radial velocities (i.e. redshifts). So, the presence of groups at the redshifts of both objects increases the probability of chance projection.

Figure 2. Objects with redshift available in NED within 20 arcmin from 2dFGRS N379Z082. X axis is angular separation from 2dFGRS N379Z082 and Y axis is the redshift (shown as radial velocity, cz) of the object. Excluded are objects with redshift quality problems and galaxy group entries.

One curious coincidence here is that the redshift of the higher redshift group is very closely twice the redshift of the lower redshift group. Figure 2 also shows a banded structure so that at some radial velocity ranges there are lot of objects and some radial velocity ranges don’t have any objects.

The question always presented with these kind of systems is that should the background galaxy show so well through the disk of the main galaxy? To this I don’t have answer, but object 2 is somewhat at the outskirts of the main galaxy disk, so seeing through the disk might be more probable there.


Figure 3 below shows the field near 2dFGRS N379Z082 and object data is presented below that. Some notes on the field:

– There are some stars in the field marked by their radial velocity (ones that have number followed by “km/s”). These are given in SDSS DR9 (NED only gives objects to SDSS DR6 level currently).

– Although there are many objects with redshifts in the field, there are no good alignments across lower redshift galaxies. However, field has a possibly interesting alignment. Object C seems to be a galaxy that has two blue stellar appearing objects (D and E) aligned across it. It would be interesting to know the redshifts for these three objects.

– Object 10 has another redshift measurement within its disk (z = 0.080900, 24253 km/s).

– Object 10 has two very close objects (A and B). object A has redshift close to object 10 in NED but its quality is marked as “FoF”, which I don’t know what it means, but usually these redshift quality flags indicate uncertain redshift.

Figure 3. The objects with measured redshifts near 2dFGRS N379Z082. Size of the image is about 6.7 x 6.7 arcmin. Image is from Sloan Digital Sky Survey. Click for larger version of the image.

Objects and their data

1 2dFGRS N379Z082 galaxy 0.080021 (23990 km/s) 17.0 (g) 0
2 SDSS J120040.27-000800.1 galaxy 0.163021 19.3 (g) 0.104
3 SDSS J120041.61-000923.3 galaxy 0.49599 (DR9) 22.1 (g) 1.389
4 SDSS J120044.69-000922.4 galaxy 0.165374 18.1 (g) 1.769
5 2dFGRS N380Z131 galaxy 0.164100 18.4 (g) 1.825
6 2dFGRS N379Z077 galaxy 0.165720 17.6 (g) 1.834
7 2dFGRS N379Z078 galaxy 0.163164 18.2 (g) 2.191
8 SDSS J120046.64-000620.1 galaxy 0.166192 18.9 (g) 2.408
9 2QZ J120047.5-000939 galaxy 0.206 20.7 2.470
10 SDSS J120028.87-000724.8 galaxy 0.081336 (24384 km/s) 16.1 (g) 2.843
11 SDSS J120029.52-000943.3 galaxy 0.43266 (DR9) 22.2 (g) 3.086
12 2dFGRS N379Z088 galaxy 0.177200 19.39 3.298
13 SDSS J120028.47-000619.1 galaxy 0.257866 20.6 (g) 3.356
14 SDSS J120026.81-000611.1 galaxy 0.257464 21.0 (g) 3.781
15 2dFGRS N379Z087 galaxy 0.200016 18.8 (g) 4.373

NED objects within 10′ from 2dFGRS N379Z082