Subarcsecond international LOFAR radio images of the M82 nucleus at 118 MHz and 154 MHz
Artikel i vetenskaplig tidskrift, 2015
Context. The nuclear starburst in the nearby galaxy M82 provides an excellent laboratory for understanding the physics of star formation. This galaxy has been extensively observed in the past, revealing tens of radio bright compact objects embedded in a diffuse free-free absorbing medium. Our understanding of the structure and physics of this medium in M82 can be greatly improved by high-resolution images at tow frequencies where the effects of free-free absorption are most prominent.
Aims. The aims of this study are, firstly, to demonstrate imaging using international baselines of the Low Frequency Array (LOFAR), and secondly, to constrain low frequency spectra of compact and diffuse emission in the central starburst region of M82 via high resolution radio imaging at low frequencies.
Methods. The international LOFAR telescope was used to observe M82 at 110-126 MHz and 146-1621\4Hz. Images were obtained using standard techniques from very long baseline interferometry. images were obtained at each frequency range: one only using international baselines, and one only using the longest Dutch (remote) baselines.
Results. The 154 MHz image obtained using international baselines is a new imaging record in terms of combined image resolution (0.3") and sensitivity (sigma = 0.15 mIy/beath) at low frequencies (<327 MHz). We detected 16 objects at 154 MHz, six of these also at 118 MHz. Seven objects detected at 154 MHz have not been catalogued previously. For the nine objects previously detected, we obtained spectral indices and emission measures by fitting models to spectra (combining LOFAR with literature data). Four weaker but resolved features are also found: a linear (50 pc) filament and three other resolved objects, of which two show a clear shell structure. We do not detect any emission from either supernova 2008iz or from the radio transient source 43.78+59.3. The images obtained using remote baselines show diffuse emission associated with the outflow in M82, with reduced brightness in the region of the edge on star forming disk.
galaxies: individual: M82
galaxies: star formation
techniques: high angular resolution
supernovae: individual: 2008iz
techniques: interferometric
galaxies: starburst
Författare
Eskil Varenius
Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik
John Conway
Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium
Ivan Marti-Vidal
Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium
R. Beswick
University of Manchester
A. T. Deller
Netherlands Institute for Radio Astronomy (ASTRON)
O. Wucknitz
Max-Planck-Gesellschaft
N. Jackson
University of Manchester
B. Adebahr
Max-Planck-Gesellschaft
Miguel Angel Perez-Torres
Instituto de Astrofisica de Andalucía (IAA)
Universidad de Zaragoza
Centro de Estudios de Física del Cosmos de Aragón
K.T. Chyz̊y
Uniwersytet Jagiellonski w Krakowie
Tobia Carozzi
Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium
J. Moldon
Netherlands Institute for Radio Astronomy (ASTRON)
Susanne Aalto
Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik
R. Beck
Max-Planck-Gesellschaft
P. Best
Royal Observatory
R. J. Dettmar
Ruhr-Universität Bochum
W. van Driel
Centre national de la recherche scientifique (CNRS)
G. Brunetti
Istituto di Radioastronomia
M. Brüggen
Universität Hamburg
M. Haverkorn
Universiteit Leiden
Radboud Universiteit
G. Heald
Netherlands Institute for Radio Astronomy (ASTRON)
Rijksuniversiteit Groningen
Cathy Horellou
Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik
M. J. Jarvis
University of Oxford
University of the Western Cape
L. K. Morabito
Universiteit Leiden
G. K. Miley
Universiteit Leiden
H. Rottgering
Universiteit Leiden
M. C. Toribio
Netherlands Institute for Radio Astronomy (ASTRON)
G. J. White
RAL Space/STFC
Open University
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 574 Art. no. A114- A114Advanced Radio Astronomy in Europe (RADIONET3)
Europeiska kommissionen (EU) (EC/FP7/283393), 2012-01-01 -- 2015-12-31.
Ämneskategorier
Astronomi, astrofysik och kosmologi
DOI
10.1051/0004-6361/201425089