6dF J0406457-124421 – QSO pair at same redshift

Arp (1980) noted this system briefly:

Another pair of obviously related quasars is shown in Figure 6. Search of the Palomar Sky Survey reveals a galaxy just about midway between them.

One point about these two quasars is their similar redshift. The centering galaxy is brightest in the nearby field, according to Arp.

Marr & Spinrad (1985) found a faint galaxy (object 4 in the object table below) near object 3, at redshift of z = 0.568. They said:

The nominal velocity difference between the two objects is only 900 km s-1 in the quasar’s rest frame, clearly consistent (within the galaxy redshift uncertainty) with a cluster velocity dispersion.

There are some studies of absorption lines in the spectrum of object 3, and their possible correlation with nearby galaxy distribution. Williger et al. (2006) is an example of such study.


There are lot of objects with available redshift in the field, but only the centering galaxy and the two quasars are shown in Fig. 1. Nearest objects with available redshift to 6dF J0406457-124421 are about at 8 – 10 arcmin angular distance, and as the photographed field in Fig. 1 is only 5 x 5 arcmin, those objects are not shown.

There are 15 objects having redshifts between z = 0.55 and 0.60 within 40 arcmin from 6dF J0406457-124421. The two aligned across 6dF J0406457-124421 are clearly brightest of them.

Figure 1. The field of 6dF J0406457-124421 with the two quasars. Size of the photograph section of the image is 5 x 5 arcmin. Image is from Digitized Sky Survey (POSS2/UKSTU blue).

Objects and their data

1 6dF J0406457-124421 galaxy 0.032621 (9780 km/s) 16.11 0
2 [HB89] 0403-132 QSO, HPQ 0.570550 17.17 29.555
3 [HB89] 0405-123 QSO, blazar, Sy1.2 0.572590 14.82 36.169
4 G1 galaxy 0.568 20 0.22

NED page for object 1
NED page for object 2
NED page for object 3


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

Marr & Spinrad, 1985, PASP, 97, 684, “An emission-line companion galaxy to the quasar PKS 0405-123”

Williger et al., 2006, ApJ, 636, 631, “The Low-Redshift Lyα Forest toward PKS 0405-123”

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