Discovery of Carbon Radio Recombination Lines in M82
Journal article, 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.

ISM: general

galaxies: individual (M82)

radio lines: ISM

radio lines: galaxies

galaxies: ISM

Author

L. K. Morabito

Leiden University

J. B. R. Oonk

Netherlands Institute for Radio Astronomy (ASTRON)

Leiden University

F. Salgado

Leiden University

M. C. Toribio

Netherlands Institute for Radio Astronomy (ASTRON)

H. Rottgering

Leiden University

Aggm Tielens

Leiden University

R. Beck

Max Planck Institute

B. Adebahr

Max Planck Institute

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

Jagiellonian University in Kraków

John Conway

Chalmers, Earth and Space Sciences, Onsala Space Observatory

W. van Driel

Paris Diderot University

J. Gregson

Open University

M. Haverkorn

Radboud University

Leiden University

G. Heald

University of Groningen

Netherlands Institute for Radio Astronomy (ASTRON)

Cathy Horellou

Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics

A. Horneffer

Max Planck Institute

M. Iacobelli

Netherlands Institute for Radio Astronomy (ASTRON)

M. J. Jarvis

University of the Western Cape

University of Oxford

Ivan Marti-Vidal

Chalmers, Earth and Space Sciences, Onsala Space Observatory

G. Miley

Leiden University

D. D. Mulcahy

University of Southampton

E. Orru

Radboud University

Netherlands Institute for Radio Astronomy (ASTRON)

R. Pizzo

Netherlands Institute for Radio Astronomy (ASTRON)

A. M. M. Scaife

University of Southampton

Eskil Varenius

Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics

R. J. van Weeren

Harvard-Smithsonian Center for Astrophysics

G. J. White

Open University

RAL Space/STFC

M. W. Wise

Netherlands Institute for Radio Astronomy (ASTRON)

Astrophysical Journal Letters

2041-8205 (ISSN) 2041-8213 (eISSN)

Vol. 795 2 Art. no. L33- L33

Subject Categories

Astronomy, Astrophysics and Cosmology

DOI

10.1088/2041-8205/795/2/l33

More information

Latest update

8/1/2018 9