1996MNRAS.282..137J
Mon. Not. R. Astron. Soc. 282,137-143 (1996)
The head-tail and wide-angle-tail radio galaxies in cluster A3627
Paul A. Jones 1 and W. Bruce McAdam2
1
2
Department of Physics, University of Western Sydney, Nepean, PO Box 10, Kingswood, NSW, 2747, Australia
School of Physics, University of Sydney, NSW, 2006, Australia
Accepted 1996 April1l. Received 1996 April 11; in original form 1995 September 1
ABSTRACT
Two radio galaxies, the head-tail B1610 - 605 and the wide-angle-tail B1610 - 608,
in Abell cluster A3627 have been observed with the Australia Telescope Compact
Array. The distribution of relativistic pressure in the jets, lobes and tail has been
calculated using the standard equipartition conditions. The cluster A3627 is nearby,
massive and X-ray-bright, but only recently recognized as a significant mass
concentration in the local Universe.
Key words: galaxies: active - galaxies: clusters: individual: A3627 - galaxies: jets radio continuum: galaxies.
1 INTRODUCTION
Radio galaxies in galaxy clusters are often distorted (Miley
1980) into a wide-angle tail (WAT, C-shape) or a head-tail
(HT, elongated with the galaxy at one end). This is presumed to be due to motion of the galaxy relative to the
dense intracluster medium (ICM) causing the radio jets and
lobes to be bent back by ram pressure. In older sources, the
residual tails and cocoons have time to reach equilibrium
with the ICM, and the radiating plasma is confined by the
thermal pressure of the ICM. These radio galaxies therefore
act as probes of the pressure distribution within the cluster
medium (Burns et al. 1986).
The bright radio galaxies B1610 - 608 and B1610 - 605
lie close to the centre of the southern Abell cluster A3627
(catalogue of Abell, Corwin & Olowin 1989). This cluster is
close (distance class 1), but it is in the Zone of Avoidance
behind the Galactic plane (I, b =325°, _7°) near the cut-off
of the cluster catalogues (Abell et al. 1989). Until recently,
extinction concealed the richness of this cluster. A3627 is
now known to be much larger than the richness class 1
quoted in the catalogue and may be one of the richest
(massive) clusters in the nearby Universe, extending about
10° on the sky (Kraan-Korteweg & Woudt 1994; KraanKorteweg et al. 1996).
At the centre of the cluster, the radio source B1610 - 608
is one of the 20 strongest extragalactic radio sources, and
was identified with the 12.8-mag galaxy by Ekers (1969,
1970), who also noted a weaker radio source 16 arcmin to
the north. The stronger source was shown to be a WAT
(Christiansen et al. 1977), and the weaker source, also
resolved by the Fleurs Synthesis Telescope, is a HT
(131610 - 605) identified with a 14-mag galaxy.
Both galaxies were observed by Jones & McAdam (1992)
with improved sensitivity at 843 MHz using the Molonglo
Observatory Synthesis Telescope (MOST). B1610 - 605
was found to extend more than 26 arcmin or 315 h -1 kpc at
the cluster redshift (the scale is 1 arcmin = 12 h - I kpc:
Ho = 100 h km S -I Mpc I). The tail maintains its width at
low surface brightness, with only small deviations from the
initial jet direction, suggesting that it is in pressure equilibrium with a stable cluster medium. A detailed analysis
of the MOST data on B1610 - 605 is given by Jones &
McAdam (1994).
With the publication of the southern Abell cluster catalogue (Abell et al. 1989), correlation with the Molonglo and
Parkes radio catalogues (Robertson & Roach 1990; Brown
& Burns 1991) stimulated a study of all known radio sources
which are in clusters. Unewisse (1993) found diffuse
extended radio emission around the WAT B1610 - 608
associated with the central cD galaxy in A3627. The literature has many discrepant redshift measurements for this
cluster, and we adopt the average redshift of z=0.0143
quoted in the Abell catalogue and used by Unewisse.
This paper reports observations with the Australia Telescope Compact Array (ATCA) of the two radio sources
B1610 - 608 and B1610 - 605, and estimates the pressure
within A3627 through the interaction of the jets and lobes
with the cluster medium.
2 ATCA OBSERVATIONS
The observations were made with the ATCA (Frater,
Brooks & Whiteoak 1992, Nelson 1992) at two simultaneous frequencies of 1.36 and 2.37 GHz using the six antennas
in a 6-km array. A single 12-h synthesis was used, giving 15
© 1996 RAS
© Royal Astronomical Society • Provided by the NASA Astrophysics Data System
1996MNRAS.282..137J
138 P. A. Jones and W. B. McAdam
spacings in the u-v plane. The primary flux calibrator was
B1934 - 638 (with flux density 14.95 Jy at 1.36 GHz and
11.55 Jy at 2.37 GHz), and the phase calibrators were
B1619 - 680 and Bl718 - 649. The data were edited in the
AlPS package, transferred to the MlRlAD package for polarization calibration and returned to AlPS for imaging, cleaning
and analysis.
The observation was centred (primary beam pointing
centre and phase centre) on B1610 - 605, since this was the
main target. The primary beamwidth of the ATCA antennas
is around 33 arcmin for the 20-cm band and 22 arcmin for
the 13-cm band (Australia Telescope National Facility
1994), so that B1610 - 608, at 15 arcmin from the pointing
centre, was near the primary beam half-power radius for the
1.36-GHz data and outside the half-power radius for the
2.37-GHz data. However, since it is an order of magnitude
stronger in flux, B1610 - 608 dominated in the data, particularly in the short spacings (large-scale structure). In
order to make a satisfactory image of B1610 - 605, it was
necessary to 'clean' away the effect of B1610 - 608 from the
data by making a good image of it as well. Thus we present
data for both galaxies. The imaging required narrow-bandwidth synthesis (Bridle & Schwab 1989) to prevent smearing
over the wide field. There were 19 channels of 4 MHz used,
after some channels at the edge of the 128-MHz observed
band were dropped.
Images were made using the longest spacings with moderate tapering, to give resolution 8 arcsec at 1.36 GHz and
5 arcsec at 2.37 GHz. Another image at 2.37 GHz was made
with resolution 8 arcsec for the spectral index comparisons.
For these three images, the shortest spacing was not used, as
it contained a large amount of flux from B1610 - 608 which
could not be successfully cleaned away. Therefore these
images do not show the broad structure of B1610 - 608, but
they do show the fine details near the core. To show the
broad-scale structure of both galaxies, further images were
made at both frequencies using the shortest spacing, but
using severe tapering to give 24-arcsec resolution. At
2.37 GHz in the 24-arcsec image, B1610 - 608 was not
reconstructed well enough to be useful in the spectral index
analysis.
Images were made in total intensity and polarized
intensity (Stokes parameters I and Ip = .JCf2 + Q2) and position angle (PA). The observed E-field PAs were corrected
for Faraday rotation, to give the intrinsic PA and hence the
magnetic field direction. The 1.36-GHz data were split
into two bands (centred at 1.346 and 1.384 GHz) to resolve
the 180° ambiguity in rotation between the 1.36- and
2.37-GHz data. The PA images at the three frequencies
gave good fits (rms residual < 10°) in PA versus A,z, using
AlPS task RM, to derive rotation measures (RM) and magnetic field directions for B1610 - 605. Because of the relatively low frequencies used here, the RM correction is
significant, of order 180° between the PA at 2.37 GHz and
the intrinsic PA.
(optical position 12000 16h15m32~86, - 60039'55~8) and the
first 3 arcmin of the tail as it expands, brightens and then
fades. The 24-arcsec-resolution ATCA images show the tail
for 6 arcmin, and the MOST image (Jones & McAdam
1994) for 26 arcmin.
The peak at the galaxy is extended along the main axis
(deconvolved size 5 x 2 arcsec2, at PA 102°) and has flux
210 mJy at 1.36 GHz and 160 mJy at 2.37 GHz. It includes
flux from the inner jet and tail as well as the subarcsecond
core, since the flux of the core is 31 mJy at 2.3 GHz,
obtained with the Parkes-Tidbinbilla Interferometer (PTI)
with a fringe spacing of 0.1 arcsec (Jones, McAdam &
Reynolds 1994).
The tick marks in Fig. 1 show the direction of the magnetic field, and their lengths are proportional to polarized
intensity. The peak at the core is polarized along the axis of
the tail, and there are two peaks of polarization in the tail
with magnetic field perpendicular to the axis. However,
most of the tail here shows confused magnetic field direction. Typically, FR I jets have magnetic field parallel to the
axis near the core, becoming perpendicular to the axis as the
jet expands and brightens (Bridle & Perley 1984), and the
field pattern is disrupted wherever the jet bends. It is possible that some of the scatter in plotted magnetic field direction is due to errors in the corrections for Faraday rotation
where the polarization is weak, but the tail here shows this
pattern of magnetic field, initially parallel to the axis, then
perpendicular, then disrupted.
The RM is large and varies from around 200 rad m -2 at
the core to 300 rad m -2 over the first 0.8 arcmin of the tail,
declining to 150 rad m -2 at 2.3 arcmin. The Faraday rotation can be from several places along the line of sight - in
our own Galaxy, in the general cluster and in the environment close to the galaxy. The first two may be significant, as
B1610 - 605 is at low galactic latitude and in a rich cluster.
Simard-Normandin & Kronberg (1980) find a scatter in RM
of -140 rad m- 2 [variance - 20 000 (rad m- 2)2] for extragalactic sources with galactic latitude Ib I < 10° and Kim,
Tribble & Kronberg (1991) find -100 rad m- 2 excess RM
scatter in the centres of Abell clusters. More polarization
data at a range of frequences would be required to test
3 RESULTS
Figure 1. The ACfA image of B1610 - 605 with a resolution of
8 arcsec at 1.36 GHz. The contours give the total power, with contour levels - 8, 4, 8, 20, 40, 80 and 120 mly beam -I. The tick marks
show the magnetic field direction and polarized intensity (with the
line in the bottom right corner giving the tick length for 9 mly
beam-I).
3.1 The head-tail B1610 - 60S
The 1.36-GHz ATCA image of B1610 - 605 (Fig. 1) at
8-arcsec resolution shows the peak at the optical galaxy
181 CJ.605
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© 1996 RAS, MNRAS 282, 137-143
© Royal Astronomical Society • Provided by the NASA Astrophysics Data System
1996MNRAS.282..137J
Radio galaxies in cluster A3627 139
whether the variation in RM on the scale of a few arcmin is
associated with the galaxy or with variations in the foreground screens.
For quantitative analysis of the source profile, onedimensional Gaussians were fitted (AlPS tasks SLICE and
SLFIT) perpendicular to the axis at PA 108° in steps along the
axis. The observed width and peak flux of the fitted Gaussians were deconvolved, using the known beamwidth and
the equations (given in appendix A of Killeen, Bicknell &
Ekers 1986) for a cylindrical jet of Gaussian profile, to give
the deconvolved width and peak surface brightness.
The plot of deconvolved surface brightness (Fig. 2a)
shows the bright core (off scale), decreasing in surface
brightness for 0.5 arcmin, brightening again to a peak at
1 arcmin, and with a steady decline further along the tail.
The plot of deconvolved width (Fig. 2b) shows the expansion of the tail over the first 6 arcmin. The tail expands at
opening angle 9° to a width of 10 arcsec at 1 arcmin from the
core. The expansion then has a mean opening angle 5° out
to a tail width of 33 arcsec at 6 arcmin from the core. The
MOST data (Jones & McAdam 1994) show that the tail
width stays at around 30 arcsec for another 20 arcmin, with
a possible final expansion just at the end as the tail fades
out.
The position of the centre of the fitted Gaussians, relative
to a reference line of PA 108° (Fig. 2c) shows that the tail
starts to oscillate 1 arcmin from the core. The bending back
and forth of the tail continues over the full length (Jones &
McAdam 1994).
The spectral index plot (Fig. 3a), obtained by comparing
the data at 1.36 and 2.37 GHz, at both 8- and 24-arcsec
resolution, shows that the core has spectral index rx = - 0.4
(S, ex: va), the first 2 arcmin of the tail has rx = - 0.6, and then
the spectrum steepens, to rx < - 1.
The ratio of polarized intensity Ip to total intensity I gives
the polarized fraction (Fig. 3b), shown for only the first
2.4 arcmin of the tail. The core is only slightly (4 per cent)
polarized, while the tail shows stronger, but variable, polarization (up to 25 per cent), as seen in Fig. 1.
Values for magnetic field and pressure were calculated
using the standard assumptions of minimum energy and
minimum pressure for a synchrotron-emitting plasma
(Packolczyk 1970). The equations for a cylinder of Gaussian
profile were used, from appendices C and D of Killeen et al.
(1986). Data for the deconvolved surface brightness and
deconvolved width were taken from the 2.37-GHz ATCA
images at 8- and 24-arcsec resolution and the 843-MHz
MOST image with 44-arcsec resolution (Jones & McAdam
1994) to get calculated parameters for the whole length of
the tail. A spectral index of - 1.2 was used for the region
where it could not be determined from the data in Fig.
3(a).
The calculated magnetic field (Fig. 4) falls from about
3 x 10- 9 T (30IlG) at the core to 8 x 10- 10 Tat 4 arcmin
from the core, and 2 x 10 -10 T at the end of the tail. (The
error bars in Fig. 4 should be used cautiously, since they do
not include the effect of errors in the spectral index.) The
minimum pressure is, by the assumptions of the model,
proportional to the square of the magnetic field (also Fig. 4)
from 5 x 10- 12 Pa (5 x 10- 11 dyne cm- 2 ) at the core to
4 x 10- 13 Pa at 4 arcmin from the core, and 2 x 10- 14 Pa at
the end of the tail.
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Figure 2. The fitted parameters of B1610 - 605 as a function of
position along the tail from the core. (a) The deconvolved peak
surface brightness at 2.37 GHz (mJy beam - \ for the 8 x 8 arcsec2
beam). The core is bright (off scale); the tail brightens to a maximum 1 arcmin from the core and then fades. (b) The deconvolved
full-width at half-maximum, showing the expansion of the tail. (c)
The variation in position of the tail, relative to a reference line of
PA 108°, showing the changes in direction.
© 1996 RAS, MNRAS 282,137-143
© Royal Astronomical Society • Provided by the NASA Astrophysics Data System
1996MNRAS.282..137J
140 P. A. Jones and W B. McAdam
1610-605
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Figure 4. The derived magnetic field for B1610 - 605, from the
minimum-energy conditions, in units of 10 -10 T = 1 IlG and the
derived minimum pressure, in units of 10- 13 PA= 10- 12 dyn cm -2.
The 2.37-GHz ATCA data with a resolution of 8 arcsec and the
843-MHz MOST data with a resolution of 44 arcsec were used.
Position (oremin)
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Figure 3. (a) The spectral index of B1610 - 605 between 1.36 and
2.37 GHz. The spectral index is - 0.4 at the core, - 0.6 for the tail
out to 2 arcmin from the core, and steepens to < - 1 only beyond
3 arcmin. (b) The fractional polarization of B1610 - 605 at
2.37 GHz, showing low polarization at the core and polarization
variations in the tail.
3.2 The wide-angle tail B1610 - 608
The l.36-GHz ATCA image of B1610 - 608 (Fig. Sa) at
24-arcsec resolution shows the broad structure of the jets,
with bright peaks 1 arcmin from the centre, fading away
until they expand and brighten again into the lobes at 4 arcmin from the centre. The west jet bends sharply to the south
at the bright spot, and both lobes are bent towards the
south. The l.36-GHz ATCA image (Fig. 5b) at 8-arcsec
resolution shows the detail near the core, where the jets
brighten. There is an unresolved peak at the position of the
optical galaxy (optical position J2000 16h 15 m 03 ~ 85,
- 60054'26~0) with a flux of 40 mJy at 1.36 GHz and 63 mJy
at 2.37 GHz. This probably represents the compact (milliarcsecond scale) core, since it has an inverted spectrum and
has little emission from the jet. The core flux obtained with
the PTI is 116 mJy at 2.3 GHz (Jones et al. 1994), indicating
that the compact core is also variable.
One-dimensional Gaussians were fitted to the jets of
B1610 - 608, in the same way as for B1610 - 605, and the
width and surface brightness were deconvolved. The plot of
deconvolved surface brightness (Fig. 6a) shows symmetric
structure in the two jets, with several phases: a brightening
around 1 arcmin from the core and rapid decline, a slower
decline between 2 and 4 arcmin from the core, and brightening again in the lobes at around 5 arcmin from the core.
The west jet is fainter, and the changes between the different phases are further out from the centre. The jets
within 0.5 arcmin of the core are very faint.
The plot of deconvolved jet width (Fig. 6b) shows rapid
expansion of the jets from 0.5 to 2 arcmin from the core, a
plateau between 2 and 4 arcmin from the core and another
phase of rapid expansion as the jets flare into the lobes. The
two jets show similar behaviour, but the west jet expands
more rapidly (width 50 arcsec at 2 arcmin from the core,
opening angle 23°) than the east jet (width 30 arcsec at
2 arcmin from the core, opening angle 14°) and so is wider
in the plateau phase. The east lobe has a kink where it bends
towards the south (see Fig. Sa), so that the width fitted by
north-south slices perpendicular to the east-west reference
line is not a good fit and is biased to be high around 5 arcmin
from the core. The weak jets within 0.5 arcmin of the core
have width less than 5 arcsec.
The bending of the jets and lobes can be seen in the radio
image (Fig. Sa) and is shown in Fig. 6(c) with the transverse
position scale expanded. The west jet bends sharply to the
south away from the east-west reference line, at 1 arcmin
from the core, so the plot in Fig. 6( c) also uses a second
reference line at PA 45°. Both jets show some oscillations,
with a bending towards the south where the jets expand and
brighten into the lobes.
A comparison of the fitted data at the two frequencies at
8-arcsec resolution gives the variation in spectral index, but
only for the bright regions within 1.6 arcmin of the core. The
core has spectral index + 0.8 (that is, inverted) and the
brightest regions of the two jets spectral index - 004, with .
little variation between 0.5 and 1.6 arcmin from the core.
The overall spectral index of the source is - 1.2, calculated
from the flux densities listed in the literature obtained over
a wide frequency range. The lobes must therefore have
quite steep spectra.
© 1996 RAS, MNRAS 282,137-143
© Royal Astronomical Society • Provided by the NASA Astrophysics Data System
1996MNRAS.282..137J
Radio galaxies in cluster A3627 141
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Figure 5. (a) The ATCAimage ofB1610 - 608 with a resolution of
24 arcsec at 1.36 GHz. The contour levels are - 85, 85, 190, 380,
570, 950, 1320 and 1700 mly beam - \ (b) The ATCA image of
B1610 - 608 with a resolution of 8 arcsec at 1.36 GHz, showing the
detail near the core. The contour levels are - 20, 20, 40, 80, 120,
200, 280 and 360 mly beam-I. (Courtesy of the Astronomical
Society of the Pacific Conference Series.)
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Position (cremin)
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The minimum magnetic field and minimum pressure, calculated using the fitted surface brightness and width of the
jets, are shown in Fig. 7. The derived magnetic field is in the
range 2 x 10- 9 T (20 J,1G) at the core to 5 x 10- 10 T at the
lobes, and the corresponding pressure range is from
2 x 10- 12 Pa (2 x 10- 11 dyne cm- 2) to 1 x 10- 13 Pa. Note
that the derived pressure shows a fairly smooth decline
compared to the large variations in brightness (Fig. 6a) and
jet width (Fig. 6b).
4 DISCUSSION
Near the core of head-tail radio galaxies we expect to find
(when observed with sufficient resolution) two oppositely
directed jets which are bent back to form twin tails or merge
to form a single tail. However, B1610 - 605 is an example of
a class of head-tail galaxies which have narrow ( < 5 kpc
wide) single tails near the core (O'Dea & Owen 1985a, b;
Rottgering et al. 1994). The tail width is less than 10 arcsec
(2 h- 1 kpc) over the low-brightness region within 1 arcmin
of the core. The true VLBI core is not the peak seen in the
ATCA data at the galaxy, since this peak is extended, has a
steep spectrum and is stronger than the core seen with the
PTI. The peak occurs where twin jets (from the galaxy core)
are stopped or disrupted at a distance of, perhaps, 1 kpc in
-5
o
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Position (cremin)
Figure 6. The fitted parameters of B1610 - 608 as a function of
position along the jets from the core. (a) The deconvolved peak
surface brightness at 1.36 GHz (units mly beam-I, for the 8 x 8
arcsec2 beam) showing the brightening of the jets to peaks 1 arcmin
from the core, fading along the jets and brightening in the lobes at
around 5 arcmin. (b) The deconvolved full-width at half-maximum,
showing the expansion in the jets and lobes, with initial rapid
expansion in the jets up to 2 arcmin from the core, a plateau phase
and further expansion in the lobes at around 5 arcmin. (c) The
variation in position of the jets and lobes. An east-west reference
line (PA 90°) is used for the east lobe and the first 2 arcmin of the
west lobe (up to its kink). Beyond this, the positions of the west
lobe are plotted relative to a reference line at PA 45°.
© 1996 RAS, MNRAS 282,137-143
© Royal Astronomical Society • Provided by the NASA Astrophysics Data System
1996MNRAS.282..137J
142 P. A. Jones and W B. McAdam
1610-608
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Figure 7. The derived magnetic field for B1610 - 608, from the
minimum-energy condition, in units of 10 -10 T = 11lG, and the
derived minimum pressure, in units of 10- 13 Pa=1O- 12 dyne cm- 2•
The 1.36-GHz ATCA data with a resolution of 24 and 8 arcsec
were used.
a shock front between the galaxy interstellar medium (ISM)
and the intracluster medium (ICM). The tail then develops
in the wake of the galaxy, as it moves through the ICM. This
interpretation requires the shock front between the galaxy
and the ICM to be within the optical extent of the galaxy
(diameter 1.0 arcmin). It is considered unlikely that the
single-tail sources are due to one-sided jets, despite the
similarity in the expansion and brightening of the tails to the
behaviour of FR I jets (Bridle & Perley 1984).
The derived pressure along the tail has an exponential
decline (Fig. 4) with a scalelength of 7 arcmin (85 h - I kpc),
out to 16 arcmin beyond which the pressure change is small.
The initial pressure gradient is large and suggests a high
central mass density near the galaxy. The gradient is much
steeper than 380 h - I kpc found in radio galaxy 1919 + 479
(Burns et al. 1986). The particularly high pressure at the
peak of B1610 - 605 in the ATCA data is not well modelled,
but probably represents the ram pressure at the front of the
radio source as it moves through the ICM.
As the galaxy moves through the ICM, the tail left behind
expands and comes to rest in the ICM. The tail is then old,
and should move in pressure equilibrium with the cluster
medium. The oscillations in the position of the tail suggest
that there are eddies in the ICM along the trajectory behind
the galaxy. The magnetic field is perpendicular to the tail in
places, but the field pattern is disturbed by turbulence.
For the wide-angle tail B1610 - 608, the derived pressure
(Fig. 7) shows an exponential decline on the west side, with
a scalelength of 5 arcmin (60 h- I kpc). The east side has a
steeper decline, but is not exponential. The different phases
of expansion and brightening in the jet and lobes are considered to be related to the onset of turbulence in the jets as
they move through regions of decreasing pressure in the
ICM. The faint peak at the galaxy appears to be the typical
inverted-spectrum, milliarcsecond core seen in VLBI observations, merged with only low flux from the jets in the first
few arcsec. Within the first 0.5 arcmin of the core the jets
are narrow and weak, similar to the large-scale jets in highpower, FR II galaxies (Bridle & Perley 1984). This suggests
that the jets in low-power, FR I galaxies start out relativistic
(Parma et al. 1994), like FR II jets, but decelerate in the first
few kpc to form the brighter expanding type of jet. The
transition between the two types of jet occurs when the
velocity falls to the order of the sound speed (Bicknell
1985). The expansion and brightening of the jets between
0.5 and 2 arcmin from the core is associated with the pressure decline of the ISM over the scale of the galaxy (optical
diameter 1.5 arcmin).
The bending of the lobes into the wide-angle tail may be
due to motion of the cluster gas in a subcluster merger (as in
Burns et al. 1994) rather than peculiar motion of the cD
galaxy relative to a smooth cluster medium. The brightening
ofthe jets of B1610 - 608 at 1 arcmin from the core and the
sharp kink in the west jet at this point may be associated
with the interface between a static ISM and a windy ICM
(Burns et al. 1994; Loken, Burns & Clarke 1994). The jets
are not smoothly bent into a curve, but stay fairly straight
apart from this kink until they form the lobes. The expansion and brightening into the lobe appears to be linked to
features in the X-ray ROSAT image associated with a subcluster merger (B6hringer et al. 1996). The ROSAT image
also shows unresolved X-ray emission from both galaxies,
strong from B1610 - 608 and weak from B1610 - 605.
ACKNOWLEDGMENTS
We thank Shaun Amy and Mark Wieringa of the ATNF for
assisting with the ATCA observations, and Hans B6hringer
for a preprint of the A3627 ROSAT paper. This project has
been supported by a UWS Nepean Seed Grant and the
Australian Research Council. This research has made use of
the NASNIPAC Extragalactic Database (NED), which is
operated by the Jet Propulsion Laboratory, Caltech, under
contract with the National Aeronautics and Space
Administration.
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