IC 1767 – QSO pair alignment

In 1968 Arp reported a finding of two radio sources aligned across IC 1767 (Arp, 1980). Arp (1980) writes:

The pair of radio sources had been identified, first because of its closeness and orientation, as most likely belonging to the galaxy IC 1767. On further inspection it turned out that the apparent flux and spectral index of the radio sources were very similar.

It also turned out that the sources were rather bright quasars. Furthermore, it later turned out that the redshifts of the two quasars were very similar (Burbidge, 1968, first measured the redshift of the z = 0.62 quasar, and Searle & Bolton, 1968, measured the redshift of the z = 0.67 quasar). Arp (2001) also argues for quantized redshifts:

If one refers the redshifts to the central galaxy they become z = 0.588 and 0.640, which, after allowing for about cz = 0.02 toward and away ejection velocity, gives both quasars very close to the major quantization peak of z = 0.60.

Notes

I’ll do things slightly differently than usual here. I have took a quite thorough look on the objects in IC 1767 field, but there’s only one object with available redshift within 10 arcmin, so there’s no point in doing the regular DSS-image marked with objects. Instead I’ll give a map of objects in the field within 60 arcmin. There are 72 objects with available redshift in the field, so I also won’t include all of them to the table below, which only contains the three objects mentioned in the text above. Instead I have uploaded a textfile containing the search results from NED containing all objects with available redshift within 60 arcminutes. Numbers in the search result file correspond to the numbers in the maps below.

Here is a link to the search result file (DOC-format).

Figure 1 shows the full field map and Figure 2 shows the objects in the section marked as “B”. Some observations:

– There are a few objects (marked with green) with similar redshift to IC 1767. One of these is NGC 0773 (object 12) which is of similar size to but brighter than IC 1767.

– There is a group of objects at 1200km/s < cz < 17000 km/s. Objects belonging to this group are marked with red in the maps. This rather dense group in this field obviously forms some alignments with IC 1767 but those are ignored here as meaningless (in my opinion).

– Another possible group based on close positions to each other are the objects marked with blue. Here the redshift spread is rather large (from 20000 to 30000 km/s) but we’ll assume that this is a galaxy group and ignore it in further inspections. Note that also marked with blue is object 20 which has cz = 8995 km/s and is on other side of IC 1767 than the 20000-30000 km/s group.

– The two QSOs mentioned above are the objects 29 and 30.

– There’s another pair alignment across IC 1767 with objects 8 (z = 0.16) and 49 (z = 0.126). Other object in same direction as object 49 are objects 68 (z = 0.91) and 71 (z = 0.44). Objects 49 and 71 are also aligned across low redshift object 58 (wich has similar redshift to IC 1767).


Figure 1. The objects with measured redshifts near IC 1767 within angular separation of 60 arcmin. Image has been created in The Aladin Sky Atlas with some manual editing afterwards (numbers, coloring,…).


Figure 2. The objects in section “B” of Figure 1. Image has been created in The Aladin Sky Atlas with some manual editing afterwards (numbers, coloring,…).

Objects and their data

NBR NAME TYPE REDSHIFT MAG SEPARATION
1 IC 1767 (R’)SA(r)0/a 0.017492 (5244 km/s) 14.77 0
29 [HB89] 0155-109 QSO 0.618468 18.0 (B) 39.839
30 3C 057 QSO Opt.var. Sy1 0.670527 17.3 (B) 40.097

NED objects within 10′ from IC 1767

References

Arp, 1980, ApJ, 236, 63, “Ultraviolet excess objects in the region of a companion galaxy to NGC 2639”

Arp, 2001, ApJ, 549, 780, “The Surroundings of Disturbed, Active Galaxies”

Burbidge, E. M., 1968, ApJ, 154, 109, “Spectroscopic Observations of Twenty-Five Quasi-Stellar Objects”

Searle & Bolton, 1968, ApJ, 154, 101, “Redshifts of Fifteen Radio Sources”