# Probing the extent of the non-thermal emission from the Vela X region at TeV energies with H.E.S.S

5 APC - AHE - APC - Astrophysique des Hautes Energies
APC - UMR 7164 - AstroParticule et Cosmologie, Dipartimemto di Astronomia, Universita degli Studi di Bologna
Abstract : Vela X is a region of extended radio emission in the western part of the Vela constellation: one of the nearest pulsar wind nebulae (PWNe), and associated with the energetic Vela pulsar (PSR B0833-45). Extended very-high-energy (VHE) $\gamma$-ray emission (HESS $\mathrm{J0835\mhyphen 455}$) was discovered using the H.E.S.S. experiment in 2004. The VHE $\gamma$-ray emission was found to be coincident with a region of X-ray emission discovered with ${\it ROSAT}$ above 1.5 keV (the so-called \textit{Vela X cocoon}): a filamentary structure extending southwest from the pulsar to the centre of Vela X. A deeper observation of the entire Vela X nebula region, also including larger offsets from the cocoon, has been performed with H.E.S.S. This re-observation was carried out in order to probe the extent of the non-thermal emission from the Vela X region at TeV energies and to investigate its spectral properties. In order to increase the sensitivity to the faint $\gamma$-ray emission from the very extended Vela X region, a multivariate analysis method combining three complementary reconstruction techniques of Cherenkov-shower images is applied for the selection of $\gamma$-ray events. The analysis is performed with the On/Off background method, which estimates the background from separate observations pointing away from Vela X; towards regions free of $\gamma$-ray sources but with comparable observation conditions. The $\gamma$-ray surface brightness over the large Vela X region reveals that the detection of non-thermal VHE $\gamma$-ray emission from the PWN HESS $\mathrm{J0835\mhyphen 455}$ is statistically significant over a region of radius 1.2$^{\circ}$ around the position $\alpha$ = 08$^{\mathrm{h}}$ 35$^{\mathrm{m}}$ 00$^{\mathrm{s}}$, $\delta$ = -45$^{\circ}$ 36$^{\mathrm{\prime}}$ 00$^{\mathrm{\prime}\mathrm{\prime}}$ (J2000).
Type de document :
Article dans une revue
Astronomy and Astrophysics - A&A, EDP Sciences, 2012, 548, pp.A38. <10.1051/0004-6361/201219919>
Domaine :

http://hal.in2p3.fr/in2p3-00748534
Contributeur : Claudine Bombar <>
Soumis le : lundi 5 novembre 2012 - 14:25:22
Dernière modification le : mardi 11 octobre 2016 - 15:08:39

### Citation

A. Abramowski, Fabio Acero, F. Aharonian, A. G. Akhperjanian, G. Anton, et al.. Probing the extent of the non-thermal emission from the Vela X region at TeV energies with H.E.S.S. Astronomy and Astrophysics - A&A, EDP Sciences, 2012, 548, pp.A38. <10.1051/0004-6361/201219919>. <in2p3-00748534>

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