J/A+A/568/A74 Low-frequency (115-175MHz) image of M51 (Mulcahy+, 2014)
The nature of the low-frequency emission of M51.
First observations of a nearby galaxy with LOFAR.
Mulcahy D.D., Horneffer A., Beck R., Heald G., Fletcher A., Scaife A.,
Adebahr B., Anderson J.M., Bonafede A., Brueggen M., Brunetti G.,
Chyzy K.T., Conway J., Dettmar R.-J., Ensslin T., Haverkorn M.,
Horellou C., Iacobelli M., Israel F.P., Junklewitz H., Jurusik W.,
Koehler J., Kuniyoshi M., Orru E., Paladino R., Pizzo R., Reich W.,
Roettgering H.J.A.
<Astron. Astrophys. 568, A74 (2014)>
=2014A&A...568A..74M 2014A&A...568A..74M
ADC_Keywords: Galaxies, nearby ; Radio continuum ; Polarization
Keywords: polarization - ISM: cosmic rays - galaxies: individual: M51 -
galaxies: ISM - galaxies: magnetic fields - radio continuum: galaxies
Abstract:
The grand-design spiral galaxy M51 was observed with the LOFAR High
Frequency Antennas (HBA) and imaged in total intensity and
polarization. This observation covered the frequencies between 115MHz
and 175MHz. We produced an image of total emission of M51 at the mean
frequency of 151MHz with 20-arcsec resolution and 0.3mJy rms noise,
which is the most sensitive image of a galaxy at frequencies below
300MHz so far. The integrated spectrum of total radio emission is well
described by a power law, while flat spectral indices in the central
region indicates thermal absorption. We observe the disk to extend out
to 16kpc and a break in the radial profile near the optical radius of
the disk. The radial scale lengths in the inner and outer disks are
larger at 151MHz, and the break is smoother at 151MHz than those
observed at 1.4GHz. The arm--interarm contrast is lower at 151MHz
than at 1400MHz, indicating propagation of cosmic ray electrons (CRE)
from spiral arms into interarm regions.
Description:
Stokes I FITS image of M51 observed with LOFAR High Frequency Antennas
(HBA) with a mean frequency of 151MHz at 20-arcsec resolution. Full
details of the data reduction are explained in section 2 of the paper.
Objects:
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RA (2000) DE Designation(s)
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13 29 52.70 +47 11 42.9 M51 = NGC 5194
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 71 1 List of image
M51LOFARHBA.fits 2880 128 FITS image
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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 I1 arcsec/pix Scale [5] Scale of the image
22- 24 I3 --- Nx [301] Number of pixels along X-axis
25 A1 --- --- [x]
26- 28 I3 --- Ny [301] Number of pixels along Y-axis
30- 32 I3 Kibyte size [363] Size of the FITS image
34- 49 A16 --- FileName Name of the FITS image
51- 71 A21 --- Title Title of the file
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Acknowledgements:
David Mulcahy, D.D.Mulcahy(at)soton.ac.uk
(End) Patricia Vannier [CDS] 04-Jul-2014