Date and Time of the Query: 2019-05-26 T00:53:42 PDT
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Notes for object 3C 268.4

6 note(s) found in NED.

1. 2004A&A...424..531H
Re:3C 268.4
3C 268.4: Our FIR fluxes at 90 and 170 micron are similar to those
reported by Andreani et al. (2002), but they are surprisingly high for a
quasar at z~1.4. Therefore we checked for the presence of other nearby
galaxies. In fact, the galaxy NGC 4138 lies less than 200" apart
and has an extent of more than 100". In the FIR it is also bright with
F(170 micron) > 6 Jy, as we found with the help of the ISOPHOT
Serendipity Survey (Stickel et al. 2000). Hence the large ISOPHOT beams
of 45" and 180", respectively, have seen mainly the contamination by
NGC 4138. Therefore, we do not consider 3C 268.4 any further.

2. 2002MNRAS.331..435W
Re:3C 268.4
3C 268.4 is detected at 850 microns (5.1+-1.2 mJy) but not at 450
microns. Recent detections at 170 and 90 microns with ISO and at 1.3 mm
with IRAM(6.1+-1.6 mJy) indicate a high far-infrared luminosity and
some synchrotron contamination of the mm fluxes (Andreani et al. 2001).
Estimating the millimetre contamination by synchrotron emission is not
a trivial matter owing to the lack of other data at frequencies higher
than 15 GHz (Fig. 1). For reasons to be discussed in Section 3 we
expect the extended radio lobe spectrum to steepen sharply at high
frequencies and the main synchrotron component in the millimetre regime
to be the compact core. It is also clear in Fig. 1 that the core
spectrum also steepens between 15 GHz and 1.3 mm. To estimate the
synchrotron contamination to the 850-microns flux density we assume a
millimetre core spectrum with {alpha}=1, which gives S_850_=3 mJy. As
we will show below, the properties of the dust spectrum require a
contribution to the 850-microns flux-density from dust, which is in
approximate agreement with this contribution from the core.
We have fitted the far-IR and submm data with a range of thermal dust
spectra. Using only the ISO fluxes and the 450-microns upper limit, the
strongly peaked spectrum at ~170 microns (observed frame) provides
strong constraints on the dust temperature and emissivity index (Fig.
1). The best fitting values are T=48 K and {beta}=2.5 for dust that is
optically thin at {lambda}>50 microns and this spectrum gives an
expected 850-microns flux-density of 2.7 mJy. The far-IR luminosity of
this dust spectrum is 2X10^13^ L. This value for the emissivity index
is larger than usually observed (Priddey & McMahon 2001; Dunne et al.
2000) but requiring {beta} to be no larger than 2.0 gives a similar
far-IR luminosity and a higher expected 850-microns flux-density of
4.0 mJy. Therefore we conclude that the dust contribution to the
850-microns flux-density is significant and independent of its actual
value, L_FIR_>2X10^13^ L and the object is classified as hyperluminous.
3C 268.4 is not heavily reddened in the rest-frame UV but does show
strong C IV associated absorption (equivalent width >1.9 Angstrom;
Anderson et al. 1987).

3. 1995A&AS..110..213R
Re:[HB89] 1206+439
1206+439 (3C 268.4): Maps for this source have been published at all
frequencies. The 408 MHz and 1666 MHz maps are discussed by Lonsdale &
Morrison (1983). A 5 GHz VLA map is presented by Burns et al. (1984) and
more maps and discussion can be found in Lonsdale & Barthel (1986). The
present 5 GHz map was made from only two minutes of data.

4. 1994ApJS...93....1A
Re:3C 268.4
Q1206+4356 (3C 268.4, z_em_ = 1.400)
AWFC studied this object in the range 3150 -
4025A and they found Mg II absorption at z_abs_=0.4124 and
associated C IV absorption at z_abs_=1.3767 and 1.3963. We find no
absorption lines in our spectrum. At the position of Mg II at z_abs_
= 1.38 the 1{sigma} rest equivalent width limit in our spectrum is

5. 1992MNRAS.257..545L
Re:3C 268.4
The high-resolution maps show a jet-like feature pointing from the strong
core of this quasar towards the more compact one of the double hotspots
in the Sp lobe. The spectral indices are derived from the lower
resolution maps. The spectrum in the Sp lobe steepens along the extended
emission towards the south-west. Like 3C263.1, 3C268.4 has one hotspot
(the Nf one) with a much steeper spectrum than the other. The core has a
spectral index of 0.3 between 1.4 and 5 GHz.

6. 1978ApJ...219..803K
Re:3C 268.4
Identification by Wyndham, J.D. (1966) Ap. J., 144, 459
with QSO, z = 1.4
Schmidt, M. (1968) Ap. J., 151, 393.
Our position is 2 arcsec [east]
(twice the combined errors) of the central radio component
Pooley, G.G., and Henbest, S.N.
(1974) MNRAS, 169, 477
and 1.5 arcsec [east] of the optical position by
Veron, P. (1968) Ann. d'Ap., 31, 483.
A faint object, probably a galaxy,
is 2 arcsec [south] and 0.5 arcsec [east] of the QSO
Kristian, J. (1973) Ap. J. (Letters), 179, L61.
The BSO noted by Wyndham is at the edge of a group of faint galaxies,
but is probably not connected with them because the cluster
has z = 0.3 (estimated).

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