4C +07.04 – tight QSO-galaxy pair

Clarke et al. (1966) associated Parkes catalog radio source PKS 0114+074 (4C +07.04) with a QSO (object 2 in figure 1). Lang et al. (1970) associated the radio source to a “faint red galaxy” (object 1) near the QSO. So did Hunstead & Jauncey (1970), Pauliny-Toth et al. (1972), and Shaffer et al. (1978). Agnew & Arp (1973) gave the redshift of z = 0.861 for the QSO but it had been measured by Bolton in 1970.

Previous studies had shown 4C +07.04 as double radio source, but Akujor (1987) detected three radio sources. The third source coincided with the position of the QSO, while the two previously known coincided with the galaxy. They then suggested that the system consists of either a galaxy + QSO or a galaxy + QSO + unidentified object. In their conclusion they mention:

The QSO and the galaxy are separated by 30 arcsec. If they are physically related, one must assume a noncosmological redshift in order to place a QSO (z = 0.861) and a galaxy with z ~ 0.2 at the same distance.

However, it is unclear where they got the estimate of z ~ 0.2 for the galaxy, but earlier they mentioned assuming a redshift of z = 0.2 for a 18 mag galaxy, so they might have estimated it from the magnitude of the galaxy. Akujor (1989) presented further radio observations of the system, and verified the three radio source structure. Akujor gave a chance projection probability of 10-3 for the QSO and galaxy, and mentioned that the galaxy has peculiar structure:

Indeed, this may be the first double radio source showing such a wide difference in spectrum between two components, and the first in which one component has a spectrum as flat as 0.45.

Note that here Akujor is talking about the double radio source of the galaxy, not about the radio source related to the QSO.

The redshift of the galaxy was given by Akujor & Jackson (1992). They found it to be z = 0.344. They also found that the spectrum of the galaxy showed a rare occurance of double extended emission line system. The two emission line systems differed from each other by about 400 km/s. They noted that only few cases were known with such wholescale splitting of nuclear emission lines. They discussed rotation as a possible source for emission line splitting but they noted that the usual velocity scale produced by rotation is smaller than 400 km/s observed in 4C +07.04. They also discussed a possibility of a radio jet causing an expanding cylinder of gas:

Because of the velocity field of this expanding cylinder of gas, we see split narrow emission lines as the gas cools. This model can also be applied to the case of 0114+074, although here the splitting occurs in the whole of the nuclear line.

So they didn’t seem very happy with that hypothesis either. Then they suggested a possibility of two active nuclei, but 4C +07.04 didn’t seem to show any double hotspot structure. They also were somewhat puzzled by their observations of the optical extended emission coinciding with radio lobe, and suggested it might be a sign of interaction taking place there.

4C_07_04
Figure 1. The objects with measured redshifts near 4C +07.04. Size of the image is 5 x 5 arcmin. Image is from Digitized Sky Survey (POSS2/UKSTU Blue).

Objects and their data

NBR NAME TYPE REDSHIFT MAG SEPARATION
1 4C +07.04 NED02 galaxy 0.343000 22.14 0
2 [HB89] 0114+074 QSO 0.858000 18 0.536

NED objects with available redshift within 10′ from 4C +07.04 NED02

References

Agnew & Arp, 1973, PASP, 85, 162, “A List of Quasi-Stellar Radio Sources and Quasi-Stellar Radio Source Candidates from the 3C and 4C Catalogs Between Declination -7° and +40°”

Akujor, 1987, AJ, 94, 867, “PKS 0114+074 – A QSO-galaxy association?”

Akujor, 1989, AJ, 98, 1226, “0114 + 074 – A very asymmetric galaxy in the field of an intermediate-redshift QSO”

Akujor & Jackson, 1992, AJ, 104, 546, “Double emission-line system in the radio galaxy 0114 + 074S”

Clarke et al., 1966, AuJPh, 19, 375, “Identification of extragalactic radio sources between declinations 0° and +20°”

Hunstead & Jauncey, 1970, MNRAS, 149, 91, “Observations of radio sources near 2 f.u. at 408 MHz”

Lang et al., 1970, ApJ, 160, 17, “Additional Occultation Studies of Weak Radio Sources at Arecibo Observatory: lIST 4”

Pauliny-Toth et al., 1972, AJ, 77, 265, “The NRAO 5-GHz radio source survey. II. The 140-ft “strong”, “intermediate”, and “deep” source surveys”

Shaffer et al., 1978, AJ, 83, 209, “Optical identifications of radio sources in the NRAO 5-GHz survey – The ‘S2’ and ‘intermediate’ surveys”

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