Supernova RemnantMolecular Cloud InteractionHI CO Observations

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Supernova Remnant/Molecular Cloud
InteractionHICO Observations
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Outline

• Why studying SNR/molecular cloud interaction? How
  to know an interaction happened?
• Radio X-ray observations of two SNR/cloud
  interaction systems SNRs G23.3-0.3 (W41) and
  G18.80.3 (Kes 67)
• HICO observations to other SNRs the powerful
  tool to determine distances of Galactic objects
  (Kes 69, 73, 75)
• Summary It is time and worth to re-value the
  distances to some Galactic SNRs.

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Why studying SNR/molecular cloud interactions?

• The SNR/molecular cloud interaction may trigger
  gravitational collapse and the formation of a new
  generation of stars, so constitutes an important
  part of Galactic ecology.
• High energy Cosmic Rays (CRs) emission can
  originate from the SNR shock running into an
  adjacent giant molecular cloud (Torres et al.
  2003, Phys. Rep., 382, 303)
• 1720 MHz shock-excited OH masers are produced by
  the SNR/high density cloud interaction (Wardle
  Yusef-Zadeh, 2002, Science, 296, 2350)
• More Non-thermal X-ray emission et al.

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How to know an interaction really happened?

• 1. Detection of high energy gamma ray and
  non-thermal X-ray emission
• 2. Detection of 1720 MHz shock-excited OH masers
  ---"signposts" of SNR-molecular cloud
  interactions.
• 3. Detection of high line rates CO(2-1)/CO(1-0)
  and broad wings of 1020 km/s in CO and other
  molecular spectra (Moriguch et al. 2005, ApJ,
  631, 947).
• 4. Detection of shocked H2 emission from the
  system at near-infrared band (Reach et al. 2005,
  ApJ, 618, 297).
• Direct methods Determine distance to a SNR/CO
  Cloud system by HICO obs.

Emit TeV gamma-rays
Schematic of an expanding SNR interacting
with an adjacent molecular cloud (Wardle
Yusef-Zadeh 2002)
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HI and CO data (available X-ray data)

• 13CO(J1-0) data are from the Galactic ring
  survey (Jackson et al.2006, ApJS, 163, 145) by
  the Five College Radio Astronomy Observatory 14m
  telescope
• Range18
• FWHM46"x46"x0.21 km/s
• rms0.13 K per channel.
• Velocity range -5-- 135 km/s
• (-40d)

HI data come from the VLA Galactic Plane Survey
(Still et al. 2006, AJ, 132, 1158) Range18, -1.3range-113 165 km/s rms 2 K per
channel Short-spacing information for the H I
line emission was obtained by additional
observations with the Green Bank Telescope
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First Target SNR G18.80.3

• Previous observations (12CO HI OH, Dubner et
  al. 1996, AJ, 111, 1304 2004 AA, 426, 201)
• 1. Morphological agreement between one clump and
  the SNR shock front.
• 2. Detection of high line rates CO(2-1)/CO(1-0)
  in a clump.
• A conclusion an interaction between SN shock and
  an adjoining molecular cloud

• New13CO observationmore clearly morphological
  agreement between the SNR and an adjoining
  cloud a broaden profile in the individual 13CO
  spectra.
• HICO observations distance range of the SNR a
  GMC at 20km/s physically adjoining with the SNR.
• ROSAT PSPC a diffuse X-ray feature apparently
  associated with part of the radio shell of the
  SNR.
• There exists a physical interaction!

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Radio and X-ray images of G18.80.3
HI Image at 18.3 km/s
1420 MHz image
ROSAT PSPC image (0.5-2.4 kev)
CO image at 19.8 km/s
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HI and CO spectra
1.The largest velocity absorption feature being
at the tangent point gives a lower distance
limit of 7.6 kpc. 2. Absence of absorption at
negative velocities gives an upper limit of
15.2 kpc. 3. The broadened profile at 20 km/s in
the 13CO spectra indicates a possible SNR/CO
cloud interaction and gives a distance of 12 kpc.
20 km/s
Tangent point
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Second Target SNR G23.3-0.3 (or W41)

• Tian et al (2007, ApJL, 657, 25) shows that a
  new XMM-Newton observation reveals diffuse X-ray
  emission within the HESS source
  J1834-087---suggests an association between the
  X-ray and TeV gamma-ray emission.
• High-resolution 13CO images reveal a giant
  molecular cloud at the center of W41--likely
  associated with W41.
• Probably first evidence that an old SNR
  encounters a GMC to emit TeV gamma-rays in the
  cloud.
• New results (Leahy Tian 2007, AJ, accepted) of
  distance estimates to W41/cloud system support
  that such interaction is physical by HI and 13CO
  spectra analysis.

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The Radio Images of W41/molecular cloud
13CO map from the Galactic Ring Survey a GMC at
the center of W41 MH2105 M0 NH2 1022
(cm-2), no 103 (cm-3)
The 1420 MHz continuum map 36'x30' in size,
F142060/-8 Jy Alpha0.43 (330 -1420 MHz) (Fv
v(-alpha)
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XMM-NEWTON Observations of W41
The central part image of W41 in the 1.5-7 keV
hard bands. A region of enhanced intensity is
clearly present within the extent of HESS
source, apparently diffuse, likely associated
with HESS source. Contours of 13CO emissions at
1.2, 1.4, 1.8 and 2.1k.
An EPIC-pn intensity image in the 0.3-1.5 keV
soft bands. The field is of smooth, low uniform
surface intensity. 15 point-like sources are
detected also. Red circle represents HESS
J1834-087 Small green illustrates the region of
spectral interest. Large green outlines a region
for the background spectrum.
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First observational evidence that an old SNR
encounters a GMC to emit TeV gamma-rays in the
cloud?

• Observations and theories support Galactic TeV
  gamma-rays originate from young SNRs (SN1054,
  Weeks et al. 1989 ApJ,342,379 RXs J1713.7-3946
  and J0852.0-4622, Enomoto et al 2002
  Nature,416,823 Aharonian et al. 2005 AA,437,7)
  .
• Old SNRs ( a possible GMC) may produce TeV
  gamma-rays (Yamazaki et al, 2006, MNRAS, 371,
  1975) from the old SNR, or the SNR shock
  running into a GMC, or the GMC illuminated by
  high energy protons from the SNR shock. This may
  be distinguished by the X-ray to gamma-ray
  spectra. A simple disgnostic is the
  ratioRTeV/XFgamma(1-10TeV)/FX(2-10keV) For an
  old SNR, it is above 2 ( 102). For a young
  SNR, it is below 2 .
• The GMC associated with W41 has a density of
  103 cm-3, is dense enough to produce the
  observed TeV intensity with a lower acceleration
  efficiency(scenario W41 encounters the GMC to emit TeV
  gamma-rays (HESS J1834-087) by an acceleration
  mechanismproton-proton collision---
  pion(decay)--- gamma-rays.

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A question on distance of W41
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HI and CO spectra of W41
Two nearby CO emission features at
77 km/s and 95 km/s

• The maximum velocity of HI absorption78 km/s.
  No absorption at 95 km/s.

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The Distance of the SNR Kes 73/AXP 1E1841045

Distance 6 7.5 kpc Method employing a
commonly used technique comparing absorption
spectra of a SNR with a nearby bright
source. Results !!! Or ??? A warning this tech.
is inadequate when there exist differences in the
distribution of HI clouds along the
line-of-sight to the target source and the
comparison source.
Sanbonmatsu Helfand 1992, AJ, 104, 2189 (30
citations)
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New results 1.Absorption features appear up to
the tangent point velocity (110 km/s) 2. At
114 km/s, the HI distribution is quite
inhomogeneous. 3. The HI feature at 84 km/s
is at the far distance, A conclusion Kes 73
is in front of the HI at 84 km/s, but beyonds
the tangent point.
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• HICO spectra confirm the above conclusion.
• A CO cloud (89 km/s) is behind of Kes 73. This
  limits the distance of Kes 73/AXP between the far
  distance of 89 km/s and the dis. of the tangent
  point (7.5 9.4 kpc).
• Kes 73 has a refined age of 500 to 1000, the AXP
  has a larger 50 X-ray luminosity.

84 km/s 89 km/s
110 km/s tangent point
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The distance to Kes 69 by HIOH observations
Green A.J. et al. (1997, AJ, 114, G2058)
suggested a far distance (11.2 kpc) of the 1720
MHz OH maser velocity 69.3 km/s by HIOH obs.
Old OH maser at 69.3 km/s New H Maser at 83 km/s
X-ray (contour from ROSAT PSPC) radio (grey from
NVSS) image from Yusef-Zadeh et al. (2003, ApJ,
585, 319)

• New VLA 1420 MHz image

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HICO spectra of Kes 69

• New HI spectra reveals the maximum velocity of
  absorption 86 km/s a HI emission feature at
  113 km/s with no respective absorption.
• CO image spectra shows an adjoining cloud at
  85 km/s, no prominent cloud around 70 km/s
  towards the bright southern shell.
• A new detected 1720 MHz OH maser at velocity of
  80 86 km/s originates from within the southern
  shell of Kes 69.
• Conclusions a distance of 5.2 kpc to Kes 73,
  and existing a physical interaction between Kes
  69 and an adjoining cloud.

85 km/s
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Distance to Kes 75/Young X-ray Pulsar (PWN)
Becker Helfand, 1984, ApJ, 283, 154. 30
citations.

• Data VLA obs.(BCD) 2, 6, 20 cm
• Method HI absorption spectra
• Results distance of 19 -- 21 kpc and old age
  (2400 yrs).
• Later 700yr young X-ray PSR J1846-0258, also PWN
  within Kes 75 (Gotthelf et al.2000,ApJ)
• Extremely high X-ray luminos. for both the SNR
  and PSR 4x1037 / 8x1036 erg/s

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Distance to Kes 75/young pulsar
94 km/s

• Distance 5.3 kpc
• Small age.
• Normal luminosity

102 km/s
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Summary

• HICO is a powerful tool to estimate distances of
  Galactic objects.
• It is worth to re-value distances to more
  Galactic SNRs