Discovery of Carbon Radio Recombination Lines in M82
Reviewartikel, 2014
Carbon radio recombination lines (RRLs) at low frequencies (less than or similar to 500 MHz) trace the cold, diffuse phase of the interstellar medium, which is otherwise difficult to observe. We present the detection of carbon RRLs in absorption in M82 with the Low Frequency Array in the frequency range of 48-64 MHz. This is the first extragalactic detection of RRLs from a species other than hydrogen, and below 1 GHz. Since the carbon RRLs are not detected individually, we cross-correlated the observed spectrum with a template spectrum of carbon RRLs to determine a radial velocity of 219 km s(-1). Using this radial velocity, we stack 22 carbon-alpha transitions from quantum levels n = 468-508 to achieve an 8.5 sigma detection. The absorption line profile exhibits a narrow feature with peak optical depth of 3x10(-3) and FWHM of 31 km s(-1). Closer inspection suggests that the narrow feature is superimposed on a broad, shallow component. The total line profile appears to be correlated with the 21 cm Hi line profile reconstructed from Hi absorption in the direction of supernova remnants in the nucleus. The narrow width and centroid velocity of the feature suggests that it is associated with the nuclear starburst region. It is therefore likely that the carbon RRLs are associated with cold atomic gas in the direction of the nucleus of M82.
radio lines: ISM
radio lines: galaxies
galaxies: individual (M82)
galaxies: ISM
ISM: general
Författare
L. K. Morabito
Universiteit Leiden
J. B. R. Oonk
Netherlands Institute for Radio Astronomy (ASTRON)
Universiteit Leiden
F. Salgado
Universiteit Leiden
M. C. Toribio
Netherlands Institute for Radio Astronomy (ASTRON)
H. Rottgering
Universiteit Leiden
Aggm Tielens
Universiteit Leiden
R. Beck
Max-Planck-Gesellschaft
B. Adebahr
Max-Planck-Gesellschaft
P. Best
Royal Observatory
R. Beswick
University of Manchester
A. Bonafede
Universität Hamburg
G. Brunetti
Istituto di Radioastronomia
M. Brüggen
Universität Hamburg
K.T. Chyz̊y
Uniwersytet Jagiellonski w Krakowie
John Conway
Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium
W. van Driel
Université Paris Diderot
J. Gregson
Open University
M. Haverkorn
Universiteit Leiden
Radboud Universiteit
G. Heald
Rijksuniversiteit Groningen
Netherlands Institute for Radio Astronomy (ASTRON)
Cathy Horellou
Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik
A. Horneffer
Max-Planck-Gesellschaft
M. Iacobelli
Netherlands Institute for Radio Astronomy (ASTRON)
M. J. Jarvis
University of Oxford
University of the Western Cape
Ivan Marti-Vidal
Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium
G. Miley
Universiteit Leiden
D. D. Mulcahy
University of Southampton
E. Orru
Netherlands Institute for Radio Astronomy (ASTRON)
Radboud Universiteit
R. Pizzo
Netherlands Institute for Radio Astronomy (ASTRON)
A. M. M. Scaife
University of Southampton
Eskil Varenius
Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik
R. J. van Weeren
Harvard-Smithsonian Center for Astrophysics
G. J. White
RAL Space/STFC
Open University
M. W. Wise
Netherlands Institute for Radio Astronomy (ASTRON)
Astrophysical Journal Letters
2041-8205 (ISSN) 2041-8213 (eISSN)
Vol. 795 2 Art. no. L33- L33Ämneskategorier
Astronomi, astrofysik och kosmologi
DOI
10.1088/2041-8205/795/2/l33