Radio galaxies as probes of the largescale external medium Lakshmi Saripalli Raman Research Institut

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Radio galaxies as probes of the large-scale
external mediumLakshmi SaripalliRaman Research
InstituteBangalore
Low Frequency Radio Universe NCRA, Pune, Dec 2008
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Radio galaxies as probes
J0116-473 Saripalli et al, 2002
3C296 Credit NRAO/AUI1999
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Interaction between lobe material and thermal
plasma
3C28 3CRR Atlas
Gutierrez and Krawczynski, 2005
3C381
McCarthy et al. 1995 OIII
Leahy Perley, 1991
McCarthy et al. 1995, H?
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• On the relationship between a giant radio galaxy
  MSH 05-22 and the large-scale galaxy structure
  
• Subrahmanyan, Saripalli, Safouris and
  Hunstead, 2008, ApJ 677, 63
• MRC B0319-454 probing the large scale structure
  with a giant radio galaxy Safouris,
  Subrahmanyan, Bicknell, Saripalli, 2009, accepted
  for publication in MNRAS
• The genesis of morphologies in extended radio
  sources X-shapes, off-axis distortions and giant
  radio sources Saripalli and Subrahmanyan,
  2009, accepted for publication in ApJ

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Radio galaxies as probes of galactic halos
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B2014-558

• Linear size 1.53 Mpc
• FR-I structure
• Existence of FR-I
• X-shaped sources is potentially trouble for
• the backflow model
• (Leahy and Willams, 1984 Capetti et al, 2002)

MOST 843 MHz Jones McAdam 1992
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ATCA radio imaging of this giant FR-I X-shaped
source B2014-558 (Saripalli et al. 2008)
ATCA 1.4 GHz
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The FR-I source has a 30 kpc edge-brightened
inner double at the centreWith PA same as the
1530 kpc outer double It is restarting
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We have identified more examples of FR-I
restarting X-shaped sources
3CRR Atlas

• 3C315 has an 8 kpc inner edge-brightened double
• Position angle same as the outer double

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Both these FR-I X-shaped sources have main radio
axis close to optical major axis and wings along
minor axis similar to FR-II sources Capetti
et al, 2002
DSS

Both FR-I X-shaped radio galaxies have lobe-wing
pairs on same side of optical major axis As
expected in a backflow model
Madrid et al, 2006
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We have also identified XRGs that lack hotspots
at the ends (and possess restarting inner doubles)
4C12.03 Leahy Perley, 1991
1531104 Ledlow and Owen, 1997
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Conclusion so far Concerning FR-I X-shaped
radio sources and the backflow model

• our understanding they were hotspot radio
  sources in a previous epoch, when strong
  backflows created the wings we see today via
  interaction with an elliptical halo associated
  with the host galaxy

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A study of the relative orientation of radio
sources and their hosts

• In three samples
• 3CRR 3C revised sample
• GRG Giant radio sources
• XRG X-shaped sources

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3CRR sample of FRII radio sources
3CRR sources have a distribution in ?PA over 0-90
degrees
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3CRR sample of FRII radio sources
Larger radio sources appear to lie closer to
the minor axis
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3CRR WENSS 1-Jy MRC giant radio galaxy samples
Median offset in radio-optical PA 79 deg Most
giant radio galaxies are minor axis sources
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Giant radio sources radio-optical axis comparison
Madrid et al 2006
3C223 Size 732 kpc ?PA 88 deg
4C73.08 Size 1115 kpc ?PA 45 deg
Radio images from 3CRR Atlas
DSS
3C35 Size918 kpc ?PA79 deg
GRGs along minor axis lack wings GRGs off the
minor axis show prominent wings
Madrid et al 2006
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3CRR radio sources with prominent wings

• Definition of the sample
• Central distortions gt 50 of respective lobes
• This gives 13 sources with
• Median linear size 143 kpc
• Median radio-optical PA 22.5 deg

3C61.1 3CRR Atlas ?PA17 deg

• Radio sources with prominent wings tend to be
• Smaller, and
• Major axis sources

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Minor axis sources

• Definition 3CRR radio sources with radio axis
  within 25 deg of host minor axis
• This gives 12 sources
• Median linear size 410 kpc
• --None has central wings
• --5 are giant radio galaxies

3C319 3CRR Atlas
(1) Wings have difficulty forming when radio axis
is close to host minor axis. (2) Minor axis
sources often grow to giant sizes.
3C79 Spangler et al. 1984
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Major axis sources

• Definition 3CRR sources with radio
• axis within 25 deg of host major axis
• This gives 16 sources
• Median linear size 132 kpc
• Sources with central distortions 8
• Sources with prominent wings 5 of these 8
• Sources with no lobe distortions 6
• Number of giant radio sources 1

3C401
3CRR Atlas
Radio sources with axis close to optical major
axis tend to be (1) smaller, and (2) often
have central lobe distortions
3C433
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• X sources have radio axis closer to optical major
  axis
• Wings are closer to optical minor axis
• Main radio axis is uniformly distributed over
  0-50 degrees
• Wings prefer to be close to the optical minor axis

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In conclusion

• The radio morphology in powerful radio sources
  depends on the orientation of the radio axis
  relative to the host galaxy major axis.
• Jets propagating along the major axis advance
  less, may have strong backflows which interact
  with host gaseous halo leading to prominent wings
  and X-shaped radio sources.
• Jets propagating along the host minor axis
  advance rapidly often forming giant radio
  sources may have weak backflows, resulting in
  poor formation of wings and almost never forming
  X-shaped sources.

Strong evidence for role of galactic halos in
shaping radio sources
Capetti et al. 2002
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Case studies of the relationship between radio
structures and ambient galaxy distribution MRC
B0319-454 MSH J0505-2835
In collaboration with Ravi Subrahmanyan (RRI,
Bangalore, India) Vicky Safouris (ANU
ATNF-CSIRO) Dick Hunstead (University of
Sydney) Geoff Bicknell (ANU) Ron Ekers
(ATNF-CSIRO)
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MRC B0319-454 Redshift z 0.0622 (1 1.2
kpc) 26 arcmin LLS 1.9 Mpc
bJ 15 MR -23.7
ATCA 1378 MHz
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S (1378 MHz) 3.86 Jy P (1378 MHz) 4 x 1025
W/Hz

• Very asymmetric source
• Different lobe extents
• Different lobe surface brightnesses
• Different lobe structures
• Emission gaps

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Large-scale galaxy distribution from 6dFGS R 6
Mpc top-hat smoothing
Radio source is embedded in a filament 60 Mpc x
15 Mpc x 8 Mpc
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Zoom-in view of the large-scale structure
AAOmega and 2dF instruments on the
Anglo-Australian Telescope
664 galaxy redshifts over a 2-degree field
with 73 completeness to bJ lt 19.5
2
1
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Conc 1 Conc 2
Galaxy distribution Is not uniform Concentrations
and Voids (e.g. NE of radio src)
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How do we understand the asymmetries?

• Smoothed to R1.25 Mpc the galaxy density ratio
  is 3.30.9 between the NE and SW hotspots this
  is consistent with the side-to-side length ratio
  of 12.
• The NE jet terminates within the thermal halo of
  the loose group, of which the host is a member
  the NE lobe has higher surface brightness
• In the SW lobe, the relatively lower ambient gas
  density results in lower surface brightness lobe

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How do we understand the off-axis deflection of
the SW lobe?
There is a galaxy density gradient opposite to
the deflection factor of 2 difference in galaxy
density on the two sides of the SW hot
spot There is also an increasing galaxy density
towards the core. The associated gas density
gradients likely deflect the backflow
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MSH J0505-2835 A giant radio source
of 40 arcmin size z 0.038 1.8 Mpc
projected size
1.8 Mpc

• Source is asymmetric
• 11.6 length ratio
• N lobe shorter in length
• N lobe off axis to W

843 MHz MOST
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• No hotspots
• S (1.4 GHz) 3 Jy
• P (1.4 GHz) 1.1 x 1025 W/Hz
• The radio lobes of
• MSH J0505-2835 are not
• sharply bounded
• Radio spectral index a -1.05
• Relict lobes

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6dF galaxy redshift survey (Jones et al.
2004) Slices 216 Mpc a side and 21 Mpc
deep Radio source at the centre. (a) Dz
-0.015 to -0.010 (b) Dz -0.010 to -0.005 (c) Dz
-0.005 to -0.000 (d) Dz 0.000 to 0.005 (e)
Dz 0.005 to 0.010 (f) Dz 0.010 to
0.015 Radio source is at the bottom far
boundary of a sheet of galaxies.
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• AAT 2dF spectroscopy to get a zoomed in view of
  the local galaxy distribution
• 592 object spectra in 2 fiber allocations
• 359 galaxies within 2 diameter circle

MSH J0505-2835 at z 0.038
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5.4 Mpc 2
Galaxies within z 0.03 0.05 Large stars Dz
/- 0.003
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• On 1 Mpc scale galaxy density to the north is
  factor 3 4 higher than to the south. This is
  consistent with the side-to-side length ratio of
  12
• minimum pressure in the relic lobe synchrotron
  plasma
• p 4.1 10-15 N/m2
• and expected pressure in diffuse IGM
• pIGM 2.7 x 10-16 (Dn/n / 13) (kT / 0.5 keV)
  N/m2
• Since diffuse IGM pressure is 10 times lower
  local feedback could be enhancing the pressure in
  the vicinity
• Giant radio galaxies are potential tools in
  studying medium
• on large scales