LOFAR detections of low-frequency radio recombination lines towards Cassiopeia A
Artikel i vetenskaplig tidskrift, 2013
Cassiopeia A was observed using the low-band antennas of the LOw Frequency ARray (LOFAR) with high spectral resolution. This allowed a search for radio recombination lines (RRLs) along the line-of-sight to this source. Five carbon alpha RRLs were detected in absorption between 40 and 50 MHz with a signal-to-noise ratio of >5 from two independent LOFAR data sets. The derived line velocities (v(LSR) similar to -50 km s(-1)) and integrated optical depths (similar to 13 s(-1)) of the RRLs in our spectra, extracted over the whole supernova remnant, are consistent within each LOFAR data set and with those previously reported. For the first time, we are able to extract spectra against the brightest hotspot of the remnant at frequencies below 330 MHz. These spectra show significantly higher (15-80 percent) integrated optical depths, indicating that there is small-scale angular structure of the order of similar to 1 pc in the absorbing gas distribution over the face of the remnant. We also place an upper limit of 3 x 10(-4) on the peak optical depths of hydrogen and helium RRLs. These results demonstrate that LOFAR has the desired spectral stability and sensitivity to study faint recombination lines in the decameter band.
ISM: individual objects: Cassiopeia A
Radio lines: ISM
ISM: clouds
Författare
A. Asgekar
Shell Technology Center
J. B. R. Oonk
Universiteit Leiden
S. Yatawatta
Netherlands Institute for Radio Astronomy (ASTRON)
R. J. van Weeren
Universiteit Leiden
J. P. McKean
Rijksuniversiteit Groningen
G. White
Open University
N. Jackson
University of Manchester
J. Anderson
Technische Universität Berlin
I. M. Avruch
Rijksuniversiteit Groningen
Fabien Batejat
Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik
R. Beck
Max-Planck Institut für Radioastronomie
M. E. Bell
University of Technology Sydney
M. R. Bell
Max-Planck-Institut für Astrophysik
I. van Bemmel
Joint Institute for VLBI in Europe (JIVE)
M. J. Bentum
Universiteit Twente
G. Bernardi
Istituto di Radioastronomia
P. Best
University of Edinburgh
L. Birzan
Universität Hamburg
A. Bonafede
Istituto di Radioastronomia
R. Braun
SKA Organisation
F. Breitling
Leibniz-Institut Für Astrophysik Potsdam
R. H. van de Brink
Netherlands Institute for Radio Astronomy (ASTRON)
J. Broderick
Curtin University
W. N. Brouw
Rijksuniversiteit Groningen
M. Brüggen
Universität Hamburg
H. R. Butcher
Australian National University
W. van Cappellen
Netherlands Institute for Radio Astronomy (ASTRON)
B. Ciardi
Max-Planck-Institut für Astrophysik
John Conway
Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium
F. De Gasperin
Universität Hamburg
E. de Geus
SmarterVision BV
A. de Jong
Netherlands Institute for Radio Astronomy (ASTRON)
M. de Vos
Netherlands Institute for Radio Astronomy (ASTRON)
S. Duscha
Netherlands Institute for Radio Astronomy (ASTRON)
J. Eisloffel
Thüringer Landessternwarte Tautenburg
H. Falcke
Max-Planck Institut für Radioastronomie
R. A. Fallows
Netherlands Institute for Radio Astronomy (ASTRON)
C. Ferrari
Observatoire de la Cote d'Azur
W. Frieswijk
Netherlands Institute for Radio Astronomy (ASTRON)
M. A. Garrett
Universiteit Leiden
J. M. Griessmeier
Universite d'Orleans
T. Grit
Netherlands Institute for Radio Astronomy (ASTRON)
A. W. Gunst
Netherlands Institute for Radio Astronomy (ASTRON)
T. E. Hassall
University of Southampton
G. Heald
Commonwealth Scientific and Industrial Research Organisation (CSIRO)
J. W. T. Hessels
Universiteit Van Amsterdam
M. Hoeft
Thüringer Landessternwarte Tautenburg
M. Iacobelli
Netherlands Institute for Radio Astronomy (ASTRON)
H. Intema
Curtin University
E. Juette
Ruhr-Universität Bochum
A. Karastergiou
University of Oxford
J. Kohler
Max-Planck Institut für Radioastronomie
V. I. Kondratiev
Russian Academy of Sciences
M. Kuniyoshi
National Astronomical Observatory of Japan
G. Kuper
Netherlands Institute for Radio Astronomy (ASTRON)
C. Law
California Institute of Technology (Caltech)
J. van Leeuwen
Universiteit Van Amsterdam
P. Maat
Netherlands Institute for Radio Astronomy (ASTRON)
G. Macario
Osservatorio Astrofisico di Arcetri
G. Mann
Leibniz-Institut Für Astrophysik Potsdam
S. Markoff
Universiteit Van Amsterdam
D. McKay-Bukowski
STFC Rutherford Appleton Laboratory
M. Mevius
Netherlands Institute for Radio Astronomy (ASTRON)
J. C. A. Miller-Jones
Curtin University
J. D. Mol
Netherlands Institute for Radio Astronomy (ASTRON)
R. Morganti
Rijksuniversiteit Groningen
D. D. Mulcahy
University of Southampton
H. Munk
Netherlands Institute for Radio Astronomy (ASTRON)
M. J. Norden
Netherlands Institute for Radio Astronomy (ASTRON)
E. Orru
Netherlands Institute for Radio Astronomy (ASTRON)
H. Paas
Rijksuniversiteit Groningen
M. Pandey-Pommier
Université de Lyon
V. N. Pandey
University of Melbourne
R. Pizzo
Netherlands Institute for Radio Astronomy (ASTRON)
A. G. Polatidis
Netherlands Institute for Radio Astronomy (ASTRON)
W. Reich
Max-Planck Institut für Radioastronomie
H. Rottgering
Universiteit Leiden
B. Scheers
Stichting Centrum voor Wiskunde & Informatica (CWI)
A. Schoenmakers
Netherlands Institute for Radio Astronomy (ASTRON)
J. Sluman
Netherlands Institute for Radio Astronomy (ASTRON)
O. Smirnov
South African Radio Astronomy Observatory (SARAO)
C. Sobey
Commonwealth Scientific and Industrial Research Organisation (CSIRO)
M. Steinmetz
Leibniz-Institut Für Astrophysik Potsdam
M. Tagger
Universite d'Orleans
Y. Tang
Netherlands Institute for Radio Astronomy (ASTRON)
C. Tasse
Observatoire de Paris-Meudon
R. Vermeulen
Netherlands Institute for Radio Astronomy (ASTRON)
C. Vocks
Leibniz-Institut Für Astrophysik Potsdam
Ramj Wijers
Universiteit Van Amsterdam
M. W. Wise
Universiteit Van Amsterdam
O. Wucknitz
Max-Planck Institut für Radioastronomie
P. Zarka
LESIA - Laboratoire d'Etudes Spatiales et d'Instrumentation en Astrophysique
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 551 L11Ämneskategorier
Astronomi, astrofysik och kosmologi
DOI
10.1051/0004-6361/201221001