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; F. Aharonian; A. G. Akhperjanian; G. Anton; S. Balenderan; A. Balzer; A. Barnacka; Y. Becherini; J. Becker Tjus; K. Bernlöhr; E. Birsin; J. Biteau; A. Bochow; C. Boisson; J. Bolmont; P. Bordas; J. Brucker; F. Brun; P. Brun; T. Bulik; S. Carrigan; S. Casanova; M. Cerruti; P. M. Chadwick; A. Charbonnier; R. C G Chaves; A. Cheesebrough; G. Cologna; J. Conrad; C. Couturier; M. Dalton; M. K. Daniel; I. D. Davids; B. Degrange; C. Deil; P. Dewilt; H. J. Dickinson; A. Djannati-Ataï; W. Domainko; L. O C Drury; F. Dubois; G. Dubus; K. Dutson; J. Dyks; M. Dyrda; K. Egberts; P. Eger; P. Espigat; L. Fallon; C. Farnier; S. Fegan; F. Feinstein; M. V. Fernandes; D. Fernandez; A. Fiasson; G. Fontaine; A. Förster; M. Füßling; M. Gajdus; Y. A. Gallant; T. Garrigoux; H. Gast; B. Giebels; 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; C. Jahn; M. Jamrozy; I. Jung; M. A. Kastendieck; K. Katarzyński; U. Katz; S. Kaufmann; B. Khélifi; D. Klochkov; W. Klua Niak; T. Kneiske; Nu Komin; K. Kosack; R. Kossakowski; F. Krayzel; P. P. Krüger; H. Laffon; G. Lamanna; J. P. Lenain; D. Lennarz; T. Lohse; A. Lopatin; C. C. Lu; V. Marandon; A. Marcowith; J. Masbou; G. Maurin; N. Maxted; M. Mayer; T. J L McComb; M. C. Medina; J. Méhault; U. Menzler; R. Moderski; M. Mohamed; E. Moulin; C. L. Naumann; M. Naumann-Godo; M. De Naurois; D. Nedbal; N. Nguyen; J. Niemiec; S. J. Nolan; S. Ohm; E. De Oña Wilhelmi; B. Opitz; M. Ostrowski; I. Oya; M. Panter; D. Parsons; M. Paz Arribas; N. W. Pekeur; G. Pelletier; J. Perez; P. O. Petrucci; B. Peyaud; S. Pita; G. Pühlhofer; M. Punch; A. Quirrenbach; M. Raue; A. Reimer; O. Reimer; M. Renaud; R. De Los Reyes; F. Rieger; J. Ripken; L. Rob; S. Rosier-Lees; 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; J. L. Skilton; H. Sol; G. Spengler; A. Stawarz; R. Steenkamp; C. Stegmann; F. Stinzing; K. Stycz; I. Sushch; A. Szostek; J. P. Tavernet; R. Terrier; M. Tluczykont; C. Trichard; K. Valerius; C. Van Eldik; G. Vasileiadis; C. Venter; A. Viana; P. Vincent; H. J. Völk; F. Volpe; S. Vorobiov; 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

doi:10.1051/0004-6361/201219919

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, F. Aharonian, A. G. Akhperjanian, G. Anton, S. Balenderan, A. Balzer, A. Barnacka, Y. Becherini, J. Becker Tjus, K. Bernlöhr, E. Birsin, J. Biteau, A. Bochow, C. Boisson, J. Bolmont, P. Bordas, J. Brucker, F. Brun, P. BrunT. Bulik, S. Carrigan, S. Casanova, M. Cerruti, P. M. Chadwick, A. Charbonnier, R. C G Chaves, A. Cheesebrough, G. Cologna, J. Conrad, C. Couturier, M. Dalton, M. K. Daniel, I. D. Davids, B. Degrange, C. Deil, P. Dewilt, H. J. Dickinson, A. Djannati-Ataï, W. Domainko, L. O C Drury, F. Dubois, G. Dubus, K. Dutson, J. Dyks, M. Dyrda, K. Egberts, P. Eger, P. Espigat, L. Fallon, C. Farnier, S. Fegan, F. Feinstein, M. V. Fernandes, D. Fernandez, A. Fiasson, G. Fontaine, A. Förster, M. Füßling, M. Gajdus, Y. A. Gallant, T. Garrigoux, H. Gast, B. Giebels, 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, C. Jahn, M. Jamrozy, I. Jung, M. A. Kastendieck, K. Katarzyński, U. Katz, S. Kaufmann, B. Khélifi, D. Klochkov, W. Klua Niak, T. Kneiske, Nu Komin, K. Kosack, R. Kossakowski, F. Krayzel, P. P. Krüger, H. Laffon, G. Lamanna, J. P. Lenain, D. Lennarz, T. Lohse, A. Lopatin, C. C. Lu, V. Marandon, A. Marcowith, J. Masbou, G. Maurin, N. Maxted, M. Mayer, T. J L McComb, M. C. Medina, J. Méhault, U. Menzler, R. Moderski, M. Mohamed, E. Moulin, C. L. Naumann, M. Naumann-Godo, M. De Naurois, D. Nedbal, N. Nguyen, J. Niemiec, S. J. Nolan, S. Ohm, E. De Oña Wilhelmi, B. Opitz, M. Ostrowski, I. Oya, M. Panter, D. Parsons, M. Paz Arribas, N. W. Pekeur, G. Pelletier, J. Perez, P. O. Petrucci, B. Peyaud, S. Pita, G. Pühlhofer, M. Punch, A. Quirrenbach, M. Raue, A. Reimer, O. Reimer, M. Renaud, R. De Los Reyes, F. Rieger, J. Ripken, L. Rob, S. Rosier-Lees, 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, J. L. Skilton, H. Sol, G. Spengler, A. Stawarz, R. Steenkamp, C. Stegmann, F. Stinzing, K. Stycz, I. Sushch, A. Szostek, J. P. Tavernet, R. Terrier, M. Tluczykont, C. Trichard, K. Valerius, C. Van Eldik, G. Vasileiadis, C. Venter, A. Viana, P. Vincent, H. J. Völk, F. Volpe, S. Vorobiov, 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

Physics and Astronomy (Twin Cities)

Research output: Contribution to journal › Review article › peer-review

66 Scopus citations

Abstract

Context. Vela X is a region of extended radio emission in the western part of the Vela constellation: one of the nearest pulsar wind nebulae, and associated with the energetic Vela pulsar (PSR B0833-45). Extended very-high-energy (VHE) γ-ray emission (HESS J0835-455) was discovered using the H.E.S.S. experiment in 2004. The VHE γ-ray emission was found to be coincident with a region of X-ray emission discovered with ROSAT above 1.5 keV (the so-called Vela X cocoon): a filamentary structure extending southwest from the pulsar to the centre of Vela X. Aims. 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. Methods. To increase the sensitivity to the faint γ-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 γ-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 γ-ray sources but with comparable observation conditions. Results. The γ-ray surface brightness over the large Vela X region reveals that the detection of non-thermal VHE γ-ray emission from the PWN HESS J0835-455 is statistically significant over a region of radius 1.2° around the position α = 08 ^h35^m00^s, δ = - 45°36′00′′ (J2000). The Vela X region exhibits almost uniform γ-ray spectra over its full extent: the differential energy spectrum can be described by a power-law function with a hard spectral index Γ = 1.32 ± 0.06_stat ± 0.12_sys and an exponential cutoff at an energy of (14.0 ± 1.6_stat ± 2.6_sys) TeV. Compared to the previous H.E.S.S. observations of Vela X the new analysis confirms the general spatial overlap of the bulk of the VHE γ-ray emission with the X-ray cocoon, while its extent and morphology appear more consistent with the (more extended) radio emission, contradicting the simple correspondence between VHE γ-ray and X-ray emissions. Morphological and spectral results challenge the interpretation of the origin of γ-ray emission in the GeV and TeV ranges in the framework of current models.

Original language	English (US)
Article number	A38
Journal	Astronomy and Astrophysics
Volume	548
DOIs	https://doi.org/10.1051/0004-6361/201219919
State	Published - 2012

Keywords

ISM: individual objects: HESS J0835-455-Gamma rays: general
ISM: individual objects: Vela X
Radiation mechanisms: non-thermal

Publisher link

10.1051/0004-6361/201219919

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Abramowski, A., Acero, F., Aharonian, F., Akhperjanian, A. G., Anton, G., Balenderan, S., Balzer, A., Barnacka, A., Becherini, Y., Becker Tjus, J., Bernlöhr, K., Birsin, E., Biteau, J., Bochow, A., Boisson, C., Bolmont, J., Bordas, P., Brucker, J., Brun, F., ... Zechlin, H. S. (2012). Probing the extent of the non-thermal emission from the Vela X region at TeV energies with H.E.S.S. Astronomy and Astrophysics, 548, Article A38. https://doi.org/10.1051/0004-6361/201219919

Abramowski, A, Acero, F, Aharonian, F, Akhperjanian, AG, Anton, G, Balenderan, S, Balzer, A, Barnacka, A, Becherini, Y, Becker Tjus, J, Bernlöhr, K, Birsin, E, Biteau, J, Bochow, A, Boisson, C, Bolmont, J, Bordas, P, Brucker, J, Brun, F, Brun, P, Bulik, T, Carrigan, S, Casanova, S, Cerruti, M, Chadwick, PM, Charbonnier, A, Chaves, RCG, Cheesebrough, A, Cologna, G, Conrad, J, Couturier, C, Dalton, M, Daniel, MK, Davids, ID, Degrange, B, Deil, C, Dewilt, P, Dickinson, HJ, Djannati-Ataï, A, Domainko, W, Drury, LOC, Dubois, F, Dubus, G, Dutson, K, Dyks, J, Dyrda, M, Egberts, K, Eger, P, Espigat, P, Fallon, L, Farnier, C, Fegan, S, Feinstein, F, Fernandes, MV, Fernandez, D, Fiasson, A, Fontaine, G, Förster, A, Füßling, M, Gajdus, M, Gallant, YA, Garrigoux, T, Gast, H, Giebels, B, Glicenstein, JF, Glück, B, Göring, D, Grondin, MH, Häffner, S, Hague, JD, Hahn, J, Hampf, D, Harris, J, Heinz, S, Heinzelmann, G, Henri, G, Hermann, G, Hillert, A, Hinton, JA, Hofmann, W, Hofverberg, P, Holler, M, Horns, D, Jacholkowska, A, Jahn, C, Jamrozy, M, Jung, I, Kastendieck, MA, Katarzyński, K, Katz, U, Kaufmann, S, Khélifi, B, Klochkov, D, Klua Niak, W, Kneiske, T, Komin, N, Kosack, K, Kossakowski, R, Krayzel, F, Krüger, PP, Laffon, H, Lamanna, G, Lenain, JP, Lennarz, D, Lohse, T, Lopatin, A, Lu, CC, Marandon, V, Marcowith, A, Masbou, J, Maurin, G, Maxted, N, Mayer, M, McComb, TJL, Medina, MC, Méhault, J, Menzler, U, Moderski, R, Mohamed, M, Moulin, E, Naumann, CL, Naumann-Godo, M, De Naurois, M, Nedbal, D, Nguyen, N, Niemiec, J, Nolan, SJ, Ohm, S, De Oña Wilhelmi, E, Opitz, B, Ostrowski, M, Oya, I, Panter, M, Parsons, D, Paz Arribas, M, Pekeur, NW, Pelletier, G, Perez, J, Petrucci, PO, Peyaud, B, Pita, S, Pühlhofer, G, Punch, M, Quirrenbach, A, Raue, M, Reimer, A, Reimer, O, Renaud, M, De Los Reyes, R, Rieger, F, Ripken, J, Rob, L, Rosier-Lees, S, Rowell, G, Rudak, B, Rulten, CB, Sahakian, V, Sanchez, DA, Santangelo, A, Schlickeiser, R, Schulz, A, Schwanke, U, Schwarzburg, S, Schwemmer, S, Sheidaei, F, Skilton, JL, Sol, H, Spengler, G, Stawarz, A, Steenkamp, R, Stegmann, C, Stinzing, F, Stycz, K, Sushch, I, Szostek, A, Tavernet, JP, Terrier, R, Tluczykont, M, Trichard, C, Valerius, K, Van Eldik, C, Vasileiadis, G, Venter, C, Viana, A, Vincent, P, Völk, HJ, Volpe, F, Vorobiov, S, Vorster, M, Wagner, SJ, Ward, M, White, R, Wierzcholska, A, Wouters, D, Zacharias, M, Zajczyk, A, Zdziarski, AA, Zech, A & Zechlin, HS 2012, 'Probing the extent of the non-thermal emission from the Vela X region at TeV energies with H.E.S.S.', Astronomy and Astrophysics, vol. 548, A38. https://doi.org/10.1051/0004-6361/201219919

@article{76e3002546dd4d769efcfa2945f82bd4,

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

abstract = "Context. Vela X is a region of extended radio emission in the western part of the Vela constellation: one of the nearest pulsar wind nebulae, and associated with the energetic Vela pulsar (PSR B0833-45). Extended very-high-energy (VHE) γ-ray emission (HESS J0835-455) was discovered using the H.E.S.S. experiment in 2004. The VHE γ-ray emission was found to be coincident with a region of X-ray emission discovered with ROSAT above 1.5 keV (the so-called Vela X cocoon): a filamentary structure extending southwest from the pulsar to the centre of Vela X. Aims. 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. Methods. To increase the sensitivity to the faint γ-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 γ-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 γ-ray sources but with comparable observation conditions. Results. The γ-ray surface brightness over the large Vela X region reveals that the detection of non-thermal VHE γ-ray emission from the PWN HESS J0835-455 is statistically significant over a region of radius 1.2° around the position α = 08 h35m00s, δ = - 45°36′00′′ (J2000). The Vela X region exhibits almost uniform γ-ray spectra over its full extent: the differential energy spectrum can be described by a power-law function with a hard spectral index Γ = 1.32 ± 0.06stat ± 0.12sys and an exponential cutoff at an energy of (14.0 ± 1.6stat ± 2.6sys) TeV. Compared to the previous H.E.S.S. observations of Vela X the new analysis confirms the general spatial overlap of the bulk of the VHE γ-ray emission with the X-ray cocoon, while its extent and morphology appear more consistent with the (more extended) radio emission, contradicting the simple correspondence between VHE γ-ray and X-ray emissions. Morphological and spectral results challenge the interpretation of the origin of γ-ray emission in the GeV and TeV ranges in the framework of current models.",

keywords = "ISM: individual objects: HESS J0835-455-Gamma rays: general, ISM: individual objects: Vela X, Radiation mechanisms: non-thermal",

author = "A. Abramowski and F. Acero and F. Aharonian and Akhperjanian, {A. G.} and G. Anton and S. Balenderan and A. Balzer and A. Barnacka and Y. Becherini and {Becker Tjus}, J. and K. Bernl{\"o}hr and E. Birsin and J. Biteau and A. Bochow and C. Boisson and J. Bolmont and P. Bordas and J. Brucker and F. Brun and P. Brun and T. Bulik and S. Carrigan and S. Casanova and M. Cerruti and Chadwick, {P. M.} and A. Charbonnier and Chaves, {R. C G} and A. Cheesebrough and G. Cologna and J. Conrad and C. Couturier and M. Dalton and Daniel, {M. K.} and Davids, {I. D.} and B. Degrange and C. Deil and P. Dewilt and Dickinson, {H. J.} and A. Djannati-Ata{\"i} and W. Domainko and Drury, {L. O C} and F. Dubois and G. Dubus and K. Dutson and J. Dyks and M. Dyrda and K. Egberts and P. Eger and P. Espigat and L. Fallon and C. Farnier and S. Fegan and F. Feinstein and Fernandes, {M. V.} and D. Fernandez and A. Fiasson and G. Fontaine and A. F{\"o}rster and M. F{\"u}{\ss}ling and M. Gajdus and Gallant, {Y. A.} and T. Garrigoux and H. Gast and B. Giebels and Glicenstein, {J. F.} and B. Gl{\"u}ck and D. G{\"o}ring and Grondin, {M. H.} and S. H{\"a}ffner and Hague, {J. D.} and J. Hahn and D. Hampf and J. Harris and S. Heinz and G. Heinzelmann and G. Henri and G. Hermann and A. Hillert and Hinton, {J. A.} and W. Hofmann and P. Hofverberg and M. Holler and D. Horns and A. Jacholkowska and C. Jahn and M. Jamrozy and I. Jung and Kastendieck, {M. A.} and K. Katarzy{\'n}ski and U. Katz and S. Kaufmann and B. Kh{\'e}lifi and D. Klochkov and {Klua Niak}, W. and T. Kneiske and Nu Komin and K. Kosack and R. Kossakowski and F. Krayzel and Kr{\"u}ger, {P. P.} and H. Laffon and G. Lamanna and Lenain, {J. P.} and D. Lennarz and T. Lohse and A. Lopatin and Lu, {C. C.} and V. Marandon and A. Marcowith and J. Masbou and G. Maurin and N. Maxted and M. Mayer and McComb, {T. J L} and Medina, {M. C.} and J. M{\'e}hault and U. Menzler and R. Moderski and M. Mohamed and E. Moulin and Naumann, {C. L.} and M. Naumann-Godo and {De Naurois}, M. and D. Nedbal and N. Nguyen and J. Niemiec and Nolan, {S. J.} and S. Ohm and {De O{\~n}a Wilhelmi}, E. and B. Opitz and M. Ostrowski and I. Oya and M. Panter and D. Parsons and {Paz Arribas}, M. and Pekeur, {N. W.} and G. Pelletier and J. Perez and Petrucci, {P. O.} and B. Peyaud and S. Pita and G. P{\"u}hlhofer and M. Punch and A. Quirrenbach and M. Raue and A. Reimer and O. Reimer and M. Renaud and {De Los Reyes}, R. and F. Rieger and J. Ripken and L. Rob and S. Rosier-Lees and G. Rowell and B. Rudak and Rulten, {C. B.} and V. Sahakian and Sanchez, {D. A.} and A. Santangelo and R. Schlickeiser and A. Schulz and U. Schwanke and S. Schwarzburg and S. Schwemmer and F. Sheidaei and Skilton, {J. L.} and H. Sol and G. Spengler and A. Stawarz and R. Steenkamp and C. Stegmann and F. Stinzing and K. Stycz and I. Sushch and A. Szostek and Tavernet, {J. P.} and R. Terrier and M. Tluczykont and C. Trichard and K. Valerius and {Van Eldik}, C. and G. Vasileiadis and C. Venter and A. Viana and P. Vincent and V{\"o}lk, {H. J.} and F. Volpe and S. Vorobiov and M. Vorster and Wagner, {S. J.} and M. Ward and R. White and A. Wierzcholska and D. Wouters and M. Zacharias and A. Zajczyk and Zdziarski, {A. A.} and A. Zech and Zechlin, {H. S.}",

year = "2012",

doi = "10.1051/0004-6361/201219919",

language = "English (US)",

volume = "548",

journal = "Astronomy and Astrophysics",

issn = "0004-6361",

publisher = "EDP Sciences",

}

TY - JOUR

T1 - Probing the extent of the non-thermal emission from the Vela X region at TeV energies with H.E.S.S.

AU - Abramowski, A.

AU - Acero, F.

AU - Aharonian, F.

AU - Akhperjanian, A. G.

AU - Anton, G.

AU - Balenderan, S.

AU - Balzer, A.

AU - Barnacka, A.

AU - Becherini, Y.

AU - Becker Tjus, J.

AU - Bernlöhr, K.

AU - Birsin, E.

AU - Biteau, J.

AU - Bochow, A.

AU - Boisson, C.

AU - Bolmont, J.

AU - Bordas, P.

AU - Brucker, J.

AU - Brun, F.

AU - Brun, P.

AU - Bulik, T.

AU - Carrigan, S.

AU - Casanova, S.

AU - Cerruti, M.

AU - Chadwick, P. M.

AU - Charbonnier, A.

AU - Chaves, R. C G

AU - Cheesebrough, A.

AU - Cologna, G.

AU - Conrad, J.

AU - Couturier, C.

AU - Dalton, M.

AU - Daniel, M. K.

AU - Davids, I. D.

AU - Degrange, B.

AU - Deil, C.

AU - Dewilt, P.

AU - Dickinson, H. J.

AU - Djannati-Ataï, A.

AU - Domainko, W.

AU - Drury, L. O C

AU - Dubois, F.

AU - Dubus, G.

AU - Dutson, K.

AU - Dyks, J.

AU - Dyrda, M.

AU - Egberts, K.

AU - Eger, P.

AU - Espigat, P.

AU - Fallon, L.

AU - Farnier, C.

AU - Fegan, S.

AU - Feinstein, F.

AU - Fernandes, M. V.

AU - Fernandez, D.

AU - Fiasson, A.

AU - Fontaine, G.

AU - Förster, A.

AU - Füßling, M.

AU - Gajdus, M.

AU - Gallant, Y. A.

AU - Garrigoux, T.

AU - Gast, H.

AU - Giebels, B.

AU - Glicenstein, J. F.

AU - Glück, B.

AU - Göring, D.

AU - Grondin, M. H.

AU - Häffner, S.

AU - Hague, J. D.

AU - Hahn, J.

AU - Hampf, D.

AU - Harris, J.

AU - Heinz, S.

AU - Heinzelmann, G.

AU - Henri, G.

AU - Hermann, G.

AU - Hillert, A.

AU - Hinton, J. A.

AU - Hofmann, W.

AU - Hofverberg, P.

AU - Holler, M.

AU - Horns, D.

AU - Jacholkowska, A.

AU - Jahn, C.

AU - Jamrozy, M.

AU - Jung, I.

AU - Kastendieck, M. A.

AU - Katarzyński, K.

AU - Katz, U.

AU - Kaufmann, S.

AU - Khélifi, B.

AU - Klochkov, D.

AU - Klua Niak, W.

AU - Kneiske, T.

AU - Komin, Nu

AU - Kosack, K.

AU - Kossakowski, R.

AU - Krayzel, F.

AU - Krüger, P. P.

AU - Laffon, H.

AU - Lamanna, G.

AU - Lenain, J. P.

AU - Lennarz, D.

AU - Lohse, T.

AU - Lopatin, A.

AU - Lu, C. C.

AU - Marandon, V.

AU - Marcowith, A.

AU - Masbou, J.

AU - Maurin, G.

AU - Maxted, N.

AU - Mayer, M.

AU - McComb, T. J L

AU - Medina, M. C.

AU - Méhault, J.

AU - Menzler, U.

AU - Moderski, R.

AU - Mohamed, M.

AU - Moulin, E.

AU - Naumann, C. L.

AU - Naumann-Godo, M.

AU - De Naurois, M.

AU - Nedbal, D.

AU - Nguyen, N.

AU - Niemiec, J.

AU - Nolan, S. J.

AU - Ohm, S.

AU - De Oña Wilhelmi, E.

AU - Opitz, B.

AU - Ostrowski, M.

AU - Oya, I.

AU - Panter, M.

AU - Parsons, D.

AU - Paz Arribas, M.

AU - Pekeur, N. W.

AU - Pelletier, G.

AU - Perez, J.

AU - Petrucci, P. O.

AU - Peyaud, B.

AU - Pita, S.

AU - Pühlhofer, G.

AU - Punch, M.

AU - Quirrenbach, A.

AU - Raue, M.

AU - Reimer, A.

AU - Reimer, O.

AU - Renaud, M.

AU - De Los Reyes, R.

AU - Rieger, F.

AU - Ripken, J.

AU - Rob, L.

AU - Rosier-Lees, S.

AU - Rowell, G.

AU - Rudak, B.

AU - Rulten, C. B.

AU - Sahakian, V.

AU - Sanchez, D. A.

AU - Santangelo, A.

AU - Schlickeiser, R.

AU - Schulz, A.

AU - Schwanke, U.

AU - Schwarzburg, S.

AU - Schwemmer, S.

AU - Sheidaei, F.

AU - Skilton, J. L.

AU - Sol, H.

AU - Spengler, G.

AU - Stawarz, A.

AU - Steenkamp, R.

AU - Stegmann, C.

AU - Stinzing, F.

AU - Stycz, K.

AU - Sushch, I.

AU - Szostek, A.

AU - Tavernet, J. P.

AU - Terrier, R.

AU - Tluczykont, M.

AU - Trichard, C.

AU - Valerius, K.

AU - Van Eldik, C.

AU - Vasileiadis, G.

AU - Venter, C.

AU - Viana, A.

AU - Vincent, P.

AU - Völk, H. J.

AU - Volpe, F.

AU - Vorobiov, S.

AU - Vorster, M.

AU - Wagner, S. J.

AU - Ward, M.

AU - White, R.

AU - Wierzcholska, A.

AU - Wouters, D.

AU - Zacharias, M.

AU - Zajczyk, A.

AU - Zdziarski, A. A.

AU - Zech, A.

AU - Zechlin, H. S.

PY - 2012

Y1 - 2012

N2 - Context. Vela X is a region of extended radio emission in the western part of the Vela constellation: one of the nearest pulsar wind nebulae, and associated with the energetic Vela pulsar (PSR B0833-45). Extended very-high-energy (VHE) γ-ray emission (HESS J0835-455) was discovered using the H.E.S.S. experiment in 2004. The VHE γ-ray emission was found to be coincident with a region of X-ray emission discovered with ROSAT above 1.5 keV (the so-called Vela X cocoon): a filamentary structure extending southwest from the pulsar to the centre of Vela X. Aims. 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. Methods. To increase the sensitivity to the faint γ-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 γ-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 γ-ray sources but with comparable observation conditions. Results. The γ-ray surface brightness over the large Vela X region reveals that the detection of non-thermal VHE γ-ray emission from the PWN HESS J0835-455 is statistically significant over a region of radius 1.2° around the position α = 08 h35m00s, δ = - 45°36′00′′ (J2000). The Vela X region exhibits almost uniform γ-ray spectra over its full extent: the differential energy spectrum can be described by a power-law function with a hard spectral index Γ = 1.32 ± 0.06stat ± 0.12sys and an exponential cutoff at an energy of (14.0 ± 1.6stat ± 2.6sys) TeV. Compared to the previous H.E.S.S. observations of Vela X the new analysis confirms the general spatial overlap of the bulk of the VHE γ-ray emission with the X-ray cocoon, while its extent and morphology appear more consistent with the (more extended) radio emission, contradicting the simple correspondence between VHE γ-ray and X-ray emissions. Morphological and spectral results challenge the interpretation of the origin of γ-ray emission in the GeV and TeV ranges in the framework of current models.

AB - Context. Vela X is a region of extended radio emission in the western part of the Vela constellation: one of the nearest pulsar wind nebulae, and associated with the energetic Vela pulsar (PSR B0833-45). Extended very-high-energy (VHE) γ-ray emission (HESS J0835-455) was discovered using the H.E.S.S. experiment in 2004. The VHE γ-ray emission was found to be coincident with a region of X-ray emission discovered with ROSAT above 1.5 keV (the so-called Vela X cocoon): a filamentary structure extending southwest from the pulsar to the centre of Vela X. Aims. 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. Methods. To increase the sensitivity to the faint γ-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 γ-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 γ-ray sources but with comparable observation conditions. Results. The γ-ray surface brightness over the large Vela X region reveals that the detection of non-thermal VHE γ-ray emission from the PWN HESS J0835-455 is statistically significant over a region of radius 1.2° around the position α = 08 h35m00s, δ = - 45°36′00′′ (J2000). The Vela X region exhibits almost uniform γ-ray spectra over its full extent: the differential energy spectrum can be described by a power-law function with a hard spectral index Γ = 1.32 ± 0.06stat ± 0.12sys and an exponential cutoff at an energy of (14.0 ± 1.6stat ± 2.6sys) TeV. Compared to the previous H.E.S.S. observations of Vela X the new analysis confirms the general spatial overlap of the bulk of the VHE γ-ray emission with the X-ray cocoon, while its extent and morphology appear more consistent with the (more extended) radio emission, contradicting the simple correspondence between VHE γ-ray and X-ray emissions. Morphological and spectral results challenge the interpretation of the origin of γ-ray emission in the GeV and TeV ranges in the framework of current models.

KW - ISM: individual objects: HESS J0835-455-Gamma rays: general

KW - ISM: individual objects: Vela X

KW - Radiation mechanisms: non-thermal

UR - http://www.scopus.com/inward/record.url?scp=84869857164&partnerID=8YFLogxK

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U2 - 10.1051/0004-6361/201219919

DO - 10.1051/0004-6361/201219919

M3 - Review article

AN - SCOPUS:84869857164

SN - 0004-6361

VL - 548

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

M1 - A38

ER -

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

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