CPL - Chalmers Publication Library
| Utbildning | Forskning | Styrkeområden | Om Chalmers | In English In English Ej inloggad.

Subarcsecond international LOFAR radio images of Arp 220 at 150 MHz: A kpc-scale star forming disk surrounding nuclei with shocked outflows

Eskil Varenius (Institutionen för rymd- och geovetenskap, Radioastronomi och astrofysik) ; John Conway (Institutionen för rymd- och geovetenskap, Onsala rymdobservatorium) ; Ivan Marti-Vidal (Institutionen för rymd- och geovetenskap, Onsala rymdobservatorium) ; Susanne Aalto (Institutionen för rymd- och geovetenskap, Radioastronomi och astrofysik) ; Loreto Barcos-Munoz ; Sabine König (Institutionen för rymd- och geovetenskap, Radioastronomi och astrofysik) ; Miguel Perez-Torres ; Adam T. Deller ; Javier Moldon ; John S. III Gallagher ; Tova M. Yoast-Hull ; Cathy Horellou (Institutionen för rymd- och geovetenskap, Radioastronomi och astrofysik) ; Leah K. Morabito ; Antxon Alberdi ; Neal Jackson ; Robert Beswick ; Tobia Carozzi (Institutionen för rymd- och geovetenskap, Onsala rymdobservatorium) ; Olaf Wucknitz ; Naim Ramirez-Olivencia
Astronomy and Astrophysics (0004-6361). Vol. 593 (2016), p. A86.
[Artikel, refereegranskad vetenskaplig]

Context. Arp 220 is the prototypical ultra luminous infrared galaxy (ULIRG). Despite extensive studies, the structure at MHz-frequencies has remained unknown because of limits in spatial resolution. Aims: This work aims to constrain the flux and shape of radio emission from Arp 220 at MHz frequencies. Methods: We analyse new observations with the International Low Frequency Array (LOFAR) telescope, and archival data from the Multi-Element Radio Linked Interferometer Network (MERLIN) and the Karl G. Jansky Very Large Array (VLA). We model the spatially resolved radio spectrum of Arp 220 from 150 MHz to 33 GHz. Results: We present an image of Arp 220 at 150 MHz with resolution 0.̋65 × 0.̋35, sensitivity 0.15 mJy beam-1, and integrated flux density 394 ± 59 mJy. More than 80% of the detected flux comes from extended (6''≈ 2.2 kpc) steep spectrum (α = -0.7) emission, likely from star formation in the molecular disk surrounding the two nuclei. We find elongated features extending 0.3'' (110 pc) and 0.9'' (330 pc) from the eastern and western nucleus respectively, which we interpret as evidence for outflows. The extent of radio emission requires acceleration of cosmic rays far outside the nuclei. We find that a simple three component model can explain most of the observed radio spectrum of the galaxy. When accounting for absorption at 1.4 GHz, Arp 220 follows the FIR/radio correlation with q = 2.36, and we estimate a star formation rate of 220 M⊙ yr-1. We derive thermal fractions at 1 GHz of less than 1% for the nuclei, which indicates that a major part of the UV-photons are absorbed by dust. Conclusions: International LOFAR observations shows great promise to detect steep spectrum outflows and probe regions of thermal absorption. However, in LIRGs the emission detected at 150 MHz does not necessarily come from the main regions of star formation. This implies that high spatial resolution is crucial for accurate estimates of star formation rates for such galaxies at 150 MHz.

Nyckelord: ISM: structure, techniques: high angular resolution, galaxies: individual: Arp 220, galaxies: starburst



Denna post skapades 2016-12-02. Senast ändrad 2016-12-09.
CPL Pubid: 245805

 

Läs direkt!

Lokal fulltext (fritt tillgänglig)

Länk till annan sajt (kan kräva inloggning)


Institutioner (Chalmers)

Institutionen för rymd- och geovetenskap, Radioastronomi och astrofysik (2010-2017)
Institutionen för rymd- och geovetenskap, Onsala rymdobservatorium (2010-2017)

Ämnesområden

Astronomi
Extragalaktisk astronomi

Chalmers infrastruktur

 


Projekt

Denna publikation är ett resultat av följande projekt:


Advanced Radio Astronomy in Europe (RADIONET3) (EC/FP7/283393)