PKS 0743$-$67: An Ultra-luminous Accretion Disk and a High Kinetic Luminosity Jet

Abstract

In this letter, deep radio observations of the quasar PKS 0743$-$67 are presented that reveal a central engine capable of driving jets with enormous kinetic luminosity, $Q>4.1 \times 10^{46}\mathrm{ergs/s}$. This result is significant because archival optical spectral data indicates that the accretion disk has a thermal luminosity, $L_{bol}>2\times 10^{47}\mathrm{ergs/s}$. Furthermore, estimates of the central black hole mass from line widths indicate that $L_{bol}/L_{Edd}\approx 1$. This suggests that neither a large $L_{bol}$ nor $L_{bol}/L_{Edd}$ suppresses jet power in quasars, despite claims that they do in the recent literature. Earlier studies have found $L_{bol}$ and $Q$ are correlated in blazars. However, by removing the BL-Lacs and leaving only the quasars in the sample, we found that $Q$ is very weakly correlated with $L_{bol}$ in the subsample. Comment: To appear in ApJ Letters

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arXiv:astro-ph/0510044v1 3 Oct 2005
PKS 0743−67: An Ultra-luminous Accretion Disk and a High
Kinetic Luminosity Jet
Brian Punsly1
and
Steven Tingay2
ABSTRACT
In this letter, deep radio observations of the quasar PKS 0743−67 are pre-
sented that reveal a central engine capable of driving jets with enormous kinetic
luminosity, Q > 4.1 × 1046ergs/s. This result is significant because archival op-
tical spectral data indicates that the accretion disk has a thermal luminosity,
Lbol> 2×1047ergs/s. Furthermore, estimates of the central black hole mass from
line widths indicate that Lbol/LEdd≈ 1. This suggests that neither a large Lbol
nor Lbol/LEddsuppresses jet power in quasars, despite claims that they do in the
recent literature. Earlier studies have found Lboland Q are correlated in blazars.
However, by removing the BL-Lacs and leaving only the quasars in the sample,
we found that Q is very weakly correlated with Lbolin the subsample.
Subject headings: quasars: general — quasars: individual (PKS 0743−67) —
galaxies: jets — galaxies: active — accretion disks — black holes
1.Introduction
The connection between accretion flow parameters and radio jet production is a mys-
terious one. It has been argued in Wang et al (2004) that the jet kinetic luminosity, Q, is
correlated with the bolometric luminosity of the thermal emission, Lbol, produced by the
accretion flow in blazar type AGN. However, using virtually identical techniques as Wang
14014 Emerald Street No.116, Torrance CA, USA 90503 and International Center for Relativistic As-
trophysics, I.C.R.A.,University of Rome La Sapienza, I-00185 Roma, Italy, brian.m.punsly@L-3com.com or
brian.punsly@gte.net
2Centre for Astrophysics and Supercomputing, Swinburne University of Technology, P.O. Box 218,
Hawthorn, Vic 3122, Australia, stingay@astro.swin.edu.au

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et al (2004), Celotti et al (1997) came to the opposite conclusion. In order to shed some
light on this issue, we explore this question from a different perspective for the particu-
lar case of quasars. The vast majority (∼ 90%) of quasars are radio quiet whether their
Lbollies just above the Seyfert 1/ quasar dividing line or if they are at the other extreme,
Lbol> 1047ergs/s. This observation indicates that there are additional parameters, beyond
Lbol that Lbol/LEdd, that control the power of the radio jet. We note that the very high
Q, FRII radio source, Cygnus A, Q ≈ 1.6 × 1046erg/s (according to (1.1) of this article),
harbors a hidden quasar with Lbol just above the Seyfert 1/ quasar dividing line and has
a low Eddington rate, the ratio of Lbolto the Eddington accretion rate, Lbol/LEdd∼ 0.01
Young et al (2002); Tadhunter et al (2003). Cygnus A is an extremely powerful FR II radio
source even when compared with low frequency selected samples at high redshift (Willott
et al 1999). It has two orders of magnitude higher Q than most FR II quasars (see Chap-
ter 10 of Punsly (2001) and references therein). Thus, Cygnus A provides a well studied
”standard” candle for an extremely powerful FR II source. This motivated us to explore
the opposite extreme in the quasar family, the very powerful quasar PKS 0743−67, which
is luminous in all frequency bands and seemed to be a likely candidate for extremely high
Q jets. In sections 3 and 4, it is shown that it has a has a powerful accretion luminosity,
Lbol> 2 × 1047ergs/sec, Lbol/LEdd≈ 1, a strong unresolved VLBI radio core and prominent
radio lobes. Even though the quasar is at a redshift of z = 1.511 (Bechtold et al. 2002), both
the radio core and the radio lobe flux densities are ∼ 1Jy.
In section 5, it is demonstrated that the high Q for these two extreme ends of the quasar
range, Cygnus A and PKS 0743-067, are not out of line with the properties of the quasar
population as a whole. By studying a sample of quasars from Wang et al (2004), we find
that Q is not correlated with Lbolfor radio loud quasars that possess blazar cores. Secondly,
we demonstrate that the inverse correlation claimed between Q/Lboland Lbol/LEddin Wang
et al (2004), although true, is a trivial consequence of the fact that Q is not correlated with
Lbolin quasars. The primary conclusion of this study is that the intrinsic power of a quasar
jet is not, to first order, controlled by the accretion rate.
We have performed deep radio observations with the Australia Telescope National Facil-
ity (ATCA) in order to understand the radio structure of PKS 0743−673; the lobe emission
alone would qualify it for the 3C catalogue if the source were in the Northern Hemisphere,
our observations indicate that the jet kinetic luminosity, Q, is far more powerful than that
in Cygnus A.

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2. The Radio Observations
Previously, Rayner et al (2000) imaged the radio structure of PKS 0743−673 at 4.8 GHz
with the ATCA. We performed deep observations at 2.496, 4.800 and 8.640 GHz in order to
image the source structure and obtain higher resolution as well as spectral and polarization
data. It is essential to obtain both higher resolution and accurate spectral data to assess the
energy content of the extended structure. Our 8.640 GHz map is shown in Figure 1.
The data from our ATCA observations are presented in Table 1. Quasars with a strong
flat spectrum core often have Doppler enhanced kpc scale jets (Punsly 1995). Thus, an
estimate of Q in PKS 0743−67 requires an analysis of the data in Table 1 in order to
determine if the jet and lobe emission to the east of the nucleus is Doppler enhanced or not.
The components E1, E2, E3 denote the eastern jet/lobe components in Figure 1, numbered
consecutively from west to east.
In Figure 1, the magnetic field (perpendicular to the electric field vectors plotted) at the
core is parallel to the jet direction and remains parallel to the jet direction along the length
of the jet, even though the eastern jet goes through a large apparent bend. At the end of the
eastern jet, the magnetic field switches to being perpendicular to the jet direction, typical
of a radio galaxy hot spot.
3.Estimating the Jet Kinetic Luminosity
In order to avoid the ambiguities associated with Doppler enhancement, we estimate
the jet kinetic luminosity from the isotropic extended emission, applying a method that
allows one to convert 151 MHz flux densities, F151, measured in Jy, into estimates of kinetic
luminosity, Q, from Willott et al (1999); Blundell and Rawlings (2000) by means of the
formula derived in Punsly (2005):
Q ≈ 1.1 × 1045?(1 + z)1+αZ2F151
Z ≡ 3.31 − (3.65)
??(1 + z)4− 0.203(1 + z)3+ 0.749(1 + z)2+ 0.444(1 + z) + 0.205?−0.125?
?6
7ergs/sec ,(3-1)
×
, (3-2)
where F151is the total optically thin flux density from the lobes (i.e., no contribution from
Doppler boosted jets or radio cores). We assume a cosmology with H0=70 km/s/Mpc,
ΩΛ= 0.7 and Ωm= 0.3. In order to implement this technique, one needs to determine which
components are optically thin and which are Doppler enhanced.
There are two possible interpretations of the data that one can use to calculate Q. The

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COREW
E1
E2
E3
Fig. 1.— PKS 0743-673 at 8640 MHz. The peak intensity in the image is 1.25 Jy/beam.
The beam-size is 0.9”×1.1” at a position angle of −78.8◦. Contour levels for the Stokes I
emission are 0.0125 Jy/beam × (−0.125, 0.125, 0.25, 0.5, 1, 2, 4, 8, 16, 32, 64). The peak
fractional polarization is 52.1%. The vector lengths represent the electric field with 25.4%
fractional polarization per arcsecond. The beam ellipse is plotted in the lower left hand
corner of the figure

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νComp.Sm
%
α
(GHz)(Jy)
2.496W
C
E1
E2
E3
W
C
E1
E2
E3
W
C
E1
E2
E3
0.17
1.34
...
0.53
0.75
0.08
1.17
0.02
0.31
0.45
0.04
1.25
0.01
0.16
0.24
11
7
...
11
14
...
8
28
22
15
...
5
52
26
15
...
...
...
...
...
4.8001.16
0.21
...
0.82
0.78
1.17
0.06
...
0.98
0.93
8.640
Table 1: ATCA radio data for PKS 0743−673. Column 1: ν, radio frequency. Column 2:
Component identification from Figure 1. Column 3: S, total flux density at ν. Column 4:
m, percentage polarization at ν. Column 5: α, two point spectral index between ν and 2.496
GHz (S ∝ ν−α).