Morphological and spectral properties of the W51 region measured with the MAGIC telescopes



Downloads per month over past year

Antoranz Canales, Pedro and Barrio Uña, Juan Abel and Contreras González, José Luis and Fonseca González, Mª Victoria and Miranda Pantoja, José Miguel and Scapin, Valeria (2012) Morphological and spectral properties of the W51 region measured with the MAGIC telescopes. Astronomy & Astrophysics, 541 . ISSN 0004-6361

[thumbnail of MirandaJM04preprint.pdf]
[thumbnail of MirandaJMlibre.pdf]

Official URL:


The W51 complex hosts the supernova remnant W51C which is known to interact with the molecular clouds in the star forming region W51B. In addition, a possible pulsar wind nebula CXO J192318.5+140305 was found likely associated with the supernova remnant. Gamma-ray emission from this region was discovered by Fermi/LAT (between 0.2 and 50 GeV) and H. E. S. S. (>1 TeV). The spatial distribution of the events could not be used to pinpoint the location of the emission among the pulsar wind nebula, the supernova remnant shell and/or the molecular cloud. However, the modeling of the spectral energy distribution presented by the Fermi/LAT collaboration suggests a hadronic emission mechanism. The possibility that the gamma-ray emission from such an object is of hadronic origin can contribute to solvingthe long-standing problem of the contribution to galactic cosmic rays by supernova remnants. Aims. Our aim is to determine the morphology of the very-high-energy gamma-ray emission of W51 and measure its spectral properties. Methods. We performed observations of the W51 complex with the MAGIC telescopes for more than 50 h. The energy range accessible with MAGIC extends from 50 GeV to several TeV, allowing for the first spectral measurement at these energies. In addition, the good angular resolution in the medium (few hundred GeV) to high (above 1 TeV) energies allow us to perform morphological studies. We look for underlying structures by means of detailed morphological studies. Multi-wavelength data from this source have been sampled to model the emission with both leptonic and hadronic processes. Results. We detect an extended emission of very-high-energy gamma rays, with a significance of 11 standard deviations. We extend the spectrum from the highest Fermi/LAT energies to similar to 5 TeV and find that it follows a single power law with an index of 2.58 +/- 0.07(stat) +/- 0.22(syst). The main part of the emission coincides with the shocked cloud region, while we find a feature extending towards the pulsar wind nebula. The possible contribution of the pulsar wind nebula, assuming a point-like source, shows no dependence on energy and it is about 20% of the overall emission. The broad band spectral energy distribution can be explained with a hadronic model that implies proton acceleration above 100 TeV. This result, together with the morphology of the source, tentatively suggests that we observe ongoing acceleration of ions in the interaction zone between supernova remnant and cloud.

Item Type:Article
Additional Information:

© ESO. We would like to thank the anonymous referee as well as the Associate Editor M. Walmsley for fruitful comments and suggestions. We would like to thank the Instituto de Astrofisica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma.

Uncontrolled Keywords:Supernova Remnant W51C, Gamma-Ray Emission, Galactic Cosmic-Rays, Molecular Cloud, Nonthermal Emission, Acceleration, Discovery, Radiation, MHZ.
Subjects:Sciences > Physics > Electronics
Sciences > Physics > Electricity
Sciences > Physics > Nuclear physics
ID Code:21243
Deposited On:31 May 2013 12:24
Last Modified:10 Dec 2018 14:58

Origin of downloads

Repository Staff Only: item control page