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”

2 Responses

  1. Hello,

    I am finishing off a series of posts on the topic of discordant redshifts which you might find of interest.


  2. That’s indeed interesting, thanks. 🙂

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