J/A+A/569/A81 CO observations towards W44E and W44F with APEX (Anderl+, 2014)
APEX observations of supernova remnants. I. Non-stationary MHD-shocks in W44.
Anderl S., Gusdorf A., Gusten R.
<Astron. Astrophys. 569, A81 (2014)>
=2014A&A...569A..81A 2014A&A...569A..81A
ADC_Keywords: Supernova remnants ; Carbon monoxide ; Interstellar medium
Keywords: ISM: supernova remnants - ISM: individual objects: W44 -
ISM: kinematics and dynamics - shock waves - submillimeter: ISM -
infrared: ISM
Abstract:
When supernova blast waves interact with nearby molecular clouds, they
send slower shocks into these clouds. The resulting interaction
regions provide excellent environments for the use of MHD shock models
to constrain the physical and chemical conditions in these regions.
The interaction of supernova remnants (SNRs) with molecular clouds
gives rise to strong molecular emission in the far-IR and sub-mm
wavelength regimes. The application of MHD shock models in the
interpretation of this line emission can yield valuable information on
the energetic and chemical impact of supernova remnants.
New mapping observations with the APEX telescope in 12CO (3-2),
(4-3), (6-5), (7-6) and 13CO (3-2) towards two regions in the
supernova remnant W44 are presented. Integrated intensities are
extracted on five different positions, corresponding to local maxima
of CO emission. The integrated intensities are compared to the outputs
of a grid of models, which combine an MHD shock code with a radiative
transfer module based on the 'large velocity gradient' approximation.
Results: All extracted spectra show ambient and line-of-sight
components as well as blue- and red-shifted wings indicating the
presence of shocked gas. Basing the shock model fits only on the
highest-lying transitions that unambiguously trace the shock-heated
gas, we find that the observed CO line emission is compatible with
non-stationary shocks and a pre-shock density of 104cm-3. The ages
of the modelled shocks scatter between values of ∼1000 and ∼3000
years. The shock velocities in W44F are found to lie between 20 and
25km/s, while in W44E fast shocks (30-35km/s) as well as slower shocks
(∼20km/s) are compatible with the observed spectral line energy
diagrams. The pre-shock magnetic field strength components
perpendicular to the line-of-sight in both regions have values between
100 and 200uG. Our best-fitting models allow us to predict the full
ladder of CO transitions, the shocked gas mass in one beam as well as
the momentum- and energy injection.
Description:
Observations in 12CO (3-2), (4-3), (6-5), (7-6) towards the
supernova remnant's region W44E were conducted in July 2010, while
observations towards the region W44F were conducted in several runs in
the year 2009 (in June and August). We made use of a great part of the
suite of heterodyne receivers available for this facility: FLASH345,
FLASH460, and CHAMP+, in combination with the MPIfR Fast Fourier
Transform Spectrometer backend (FFTS), or with the newly commissioned
MPIfR X-Fast Fourier Transform Spectrometer backends (XFFT). Focus was
checked at the beginning of each observing session, after sunrise
and/or sunset on Mars, Jupiter, or Saturn. Continuum and CO line
pointing was locally established on G34.26 and R-Aql. The pointing
accuracy was found to be of the order of 5" r.m.s, regardless of the
receiver that was used. The observations were performed in
position-switching/raster mode using the APECS software. The data were
reduced with the CLASS software. Here we provide the velocity
integrated maps of 12CO (3-2), (4-3), (6-5), and (7-6) for the blue
wing (20-40km/s), red wing (50-70km/s), and ambient (40-50km/s)
emission. The CO (7-6) map was smoothed to the resolution of CO (4-3)
in order to improve the signal-to-noise.
Objects:
------------------------------------------------
RA (2000) DE Designation(s)
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18 56 09 +01 22.5 W44 = SNR G034.6-00.5
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
list.dat 112 24 List of FITS images
fits/* . 24 Individual FITS images
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 23 F4.2 arcsec/pix scale Scale of the image
25- 26 I2 --- Nx [14/52] Number of pixels along X-axis
27 A1 --- --- [x]
28- 29 I2 --- Ny [20/53] Number of pixels along Y-axis
31- 32 I2 Kibyte size [8/17] Size of FITS file
34- 61 A28 --- FileName Name of FITS file in subdirectory fits
63- 69 A7 --- Line Transition line observed (1)
71-112 A42 --- Title Title of the file
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Note (1): the transitions observed are:
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line CO(3-2) CO(4-3) CO(6-5) CO(7-6) 13CO(3-2)
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GHz 345.796 461.041 691.473 806.652 330.588
----------------------------------------------------
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Acknowledgements:
Sibylle Anderl, sibylle.anderl(at)obs.ujf-grenoble.fr
(End) Sibylle Anderl [IPAG, Grenoble], Patricia Vannier [CDS] 24-Jul-2014