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

A. Abramowski F. Acero 1 F. Aharonian A. G. Akhperjanian G. Anton S. Balenderan A. Balzer A. Barnacka Y. Becherini 2, 3 J. Becker Tjus K. Bernlöhr E. Birsin J. Biteau 2 A. Bochow C. Boisson J. Bolmont 4 P. Bordas J. Brucker F. Brun 2 P. Brun T. Bulik S. Carrigan S. Casanova M. Cerruti P. M. Chadwick A. Charbonnier 4 R. C. G. Chaves A. Cheesebrough G. Cologna J. Conrad C. Couturier M. Dalton M. K. Daniel I. D. Davids B. Degrange 2 C. Deil P. DeWilt H. J. Dickinson A. Djannati-Ataï 5 W. Domainko L. O'C. Drury F. Dubois G. Dubus K. Dutson J. Dyks M. Dyrda K. Egberts P. Eger P. Espigat 3 L. Fallon C. Farnier 1 S. Fegan 2 F. Feinstein 1 M. V. Fernandes D. Fernandez A. Fiasson 6 G. Fontaine 2 A. Förster M. Füß Ling M. Gajdus Y. A. Gallant 1 T. Garrigoux H. Gast B. Giebels 2 J. F. Glicenstein B. Glück D. Göring M. -H. Grondin S. Häffner J. D. Hague J. Hahn D. Hampf J. Harris S. Heinz G. Heinzelmann G. Henri G. Hermann A. Hillert J. A. Hinton W. Hofmann P. Hofverberg M. Holler D. Horns A. Jacholkowska 4 C. Jahn M. Jamrozy I. Jung M. A. Kastendieck K. Katarzyń Ski U. Katz S. Kaufmann B. Khélifi 2 D. Klochkov W. Kluź Niak T. Kneiske Nu. Komin 6 K. Kosack R. Kossakowski 6 F. Krayzel 6 P. P. Krüger H. Laffon 2 G. Lamanna 6 J. -P. Lenain D. Lennarz T. Lohse A. Lopatin C. -C. Lu V. Marandon A. Marcowith 1 J. Masbou 6 G. Maurin 6 N. Maxted M. Mayer T. J. L. McCom M. C. Medina J. Méhault 1 U. Menzler R. Moderski M. Mohamed E. Moulin C. L. Naumann 4 M. Naumann-Godo M. DeNaurois 4 D. Nedbal N. Nguyen J. Niemiec S. J. Nolan S. Ohm E. DeOñ AWilhelmi B. Opitz M. Ostrowski I. Oya M. Panter D. Parsons M. PazArribas N. W. Pekeur G. Pelletier J. Perez P. -O. Petrucci B. Peyaud S. Pita 3 G. Pühlhofer M. Punch 3 A. Quirrenbach M. Raue A. Reimer O. Reimer M. Renaud 1 R. DelosReyes F. Rieger J. Ripken L. Rob S. Rosier-Lees 6 G. Rowell B. Rudak C. B. Rulten V. Sahakian D. A. Sanchez A. Santangelo R. Schlickeiser A. Schulz U. Schwanke S. Schwarzburg S. Schwemmer F. Sheidaei 3 J. L. Skilton H. Sol G. Spengler L. Stawarz R. Steenkamp C. Stegmann F. Stinzing K. Stycz I. Sushch A. Szostek J. -P. Tavernet 4 R. Terrier 3 M. Tluczykont C. Trichard K. Valerius C. VanEldik G. Vasileiadis 1 C. Venter A. Viana P. Vincent 4 H. J. Völk F. Volpe S. Vorobiov 1 M. Vorster S. J. Wagner M. Ward R. White A. Wierzcholska D. Wouters M. Zacharias A. Zajczyk A. A. Zdziarski A. Zech H. -S. Zechlin
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).


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A. Abramowski, F. 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, EDP Sciences, 2012, 548, pp.A38. <10.1051/0004-6361/201219919>. <in2p3-00748534>

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