Resolving acceleration to very high energies along the Jet of Centaurus A
Abstract
The nearby radio galaxy Centaurus A belongs to a class of Active Galaxies that are very luminous at radio wavelengths. The majority of these galaxies show collimated relativistic outflows known as jets, that extend over hundreds of thousands of parsecs for the most powerful sources. Accretion of matter onto the central super-massive black hole is believed to fuel these jets and power their emission, with the radio emission being related to the synchrotron radiation of relativistic electrons in magnetic fields. The origin of the extended X-ray emission seen in the kiloparsec-scale jets from these sources is still a matter of debate, although Cen A's X-ray emission has been suggested to originate in electron synchrotron processes. The other possible explanation is Inverse Compton (IC) scattering with CMB soft photons. Synchrotron radiation needs ultra-relativistic electrons ( TeV), and given their short cooling times, requires some continuous re-acceleration mechanism to be active. IC scattering, on the other hand, does not require very energetic electrons, but requires jets that stay highly relativistic on large scales (1 Mpc) and that remain well-aligned with the line of sight. Some recent evidence disfavours inverse Compton-CMB models, although other evidence seems to be compatible with them. In principle, the detection of extended gamma-ray emission, directly probing the presence of ultra-relativistic electrons, could distinguish between these options, but instruments have hitherto been unable to resolve the relevant structures. At GeV energies there is also an unusual spectral hardening in Cen A, whose explanation is unclear. Here we report observations of Cen A at TeV energies that resolve its large-scale jet. We interpret the data as evidence for the acceleration of ultra-relativistic electrons in the jet, and favour the synchrotron explanation for the X-rays.
Keywords
Cite
@article{arxiv.2007.04823,
title = {Resolving acceleration to very high energies along the Jet of Centaurus A},
author = {The H. E. S. S. Collaboration and : and H. Abdalla and R. Adam and F. Aharonian and F. Ait Benkhali and E. O. Angüner and M. Arakawa and C. Arcaro and C. Armand and H. Ashkar and M. Backes and V. Barbosa Martins and M. Barnard and Y. Becherini and D. Berge and K. Bernlöhr and R. Blackwell and M. Böttcher and C. Boisson and J. Bolmont and S. Bonnefoy and J. Bregeon and M. Breuhaus and F. Brun and P. Brun and M. Bryan and M. Büchele and T. Bulik and T. Bylund and M. Capasso and S. Caroff and A. Carosi and S. Casanova and M. Cerruti and T. Chand and S. Chandra and A. Chen and S. Colafrancesco and M. Curyło and I. D. Davids and C. Deil and J. Devin and P. deWilt and L. Dirson and A. Djannati-Ataï and A. Dmytriiev and A. Donath and V. Doroshenko and L. O'C. Drury and J. Dyks and K. Egberts and G. Emery and J. -P. Ernenwein and S. Eschbach and K. Feijen and S. Fegan and A. Fiasson and G. Fontaine and S. Funk and M. Füßling and S. Gabici and Y. A. Gallant and F. Gaté and G. Giavitto and D. Glawion and J. F. Glicenstein and D. Gottschall and M. -H. Grondin and J. Hahn and M. Haupt and G. Heinzelmann and G. Henri and G. Hermann and J. A. Hinton and W. Hofmann and C. Hoischen and T. L. Holch and M. Holler and D. Horns and D. Huber and H. Iwasaki and M. Jamrozy and D. Jankowsky and F. Jankowsky and A. Jardin-Blicq and I. Jung-Richardt and M. A. Kastendieck and K. Katarzyński and M. Katsuragawa and U. Katz and D. Khangulyan and B. Khélifi and J. King and S. Klepser and W. Kluźniak and N. Komin and K. Kosack and D. Kostunin and M. Kraus and G. Lamanna and J. Lau and A. Lemière and M. Lemoine-Goumard and J. -P. Lenain and E. Leser and C. Levy and T. Lohse and I. Lypova and J. Mackey and J. Majumdar and D. Malyshev and V. Marandon and A. Marcowith and A. Mares and C. Mariaud and G. Martí-Devesa and R. Marx and G. Maurin and P. J. Meintjes and A. M. W. Mitchell and R. Moderski and M. Mohamed and L. Mohrmann and C. Moore and E. Moulin and J. Muller and T. Murach and S. Nakashima and M. de Naurois and H. Ndiyavala and F. Niederwanger and J. Niemiec and L. Oakes and P. O'Brien and H. Odaka and S. Ohm and E. de Ona Wilhelmi and M. Ostrowski and I. Oya and M. Panter and R. D. Parsons and C. Perennes and P. -O. Petrucci and B. Peyaud and Q. Piel and S. Pita and V. Poireau and A. Priyana Noel and D. A. Prokhorov and H. Prokoph and G. Pühlhofer and M. Punch and A. Quirrenbach and S. Raab and R. Rauth and A. Reimer and O. Reimer and Q. Remy and M. Renaud and F. Rieger and L. Rinchiuso and C. Romoli and G. Rowell and B. Rudak and E. Ruiz-Velasco and V. Sahakian and S. Saito and D. A. Sanchez and A. Santangelo and M. Sasaki and R. Schlickeiser and F. Schüssler and A. Schulz and H. M. Schutte and U. Schwanke and S. Schwemmer and M. Seglar-Arroyo and M. Senniappan and A. S. Seyffert and N. Shafi and K. Shiningayamwe and R. Simoni and A. Sinha and H. Sol and A. Specovius and M. Spir-Jacob and Ł. Stawarz and R. Steenkamp and C. Stegmann and C. Steppa and T. Takahashi and T. Tavernier and A. M. Taylor and R. Terrier and D. Tiziani and M. Tluczykont and C. Trichard and M. Tsirou and N. Tsuji and R. Tuffs and Y. Uchiyama and D. J. van der Walt and C. van Eldik and C. van Rensburg and B. van Soelen and G. Vasileiadis and J. Veh and C. Venter and P. Vincent and J. Vink and F. Voisin and H. J. Völk and T. Vuillaume and Z. Wadiasingh and S. J. Wagner and R. White and A. Wierzcholska and R. Yang and H. Yonedak and M. Zacharias and R. Zanin and A. A. Zdziarski and A. Zech and A. Ziegler and J. Zorn and N. Żywucka},
journal= {arXiv preprint arXiv:2007.04823},
year = {2020}
}
Comments
32 pages, 5 figure