Discovery of Carbon Radio Recombination Lines in M82
Artikel i vetenskaplig tidskrift, 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.

galaxies: individual (M82)

ISM: general

radio lines: galaxies

galaxies: ISM

radio lines: ISM

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-institutet

B. Adebahr

Max Planck-institutet

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

Universite Paris 7- Denis Diderot

J. Gregson

Open University

M. Haverkorn

Radboud Universiteit

Universiteit Leiden

G. Heald

Rijksuniversiteit Groningen

Netherlands Institute for Radio Astronomy (ASTRON)

Cathy Horellou

Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik

A. Horneffer

Max Planck-institutet

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 Art. no. L33- L33

Ämneskategorier

Astronomi, astrofysik och kosmologi

DOI

10.1088/2041-8205/795/2/l33