CaltechAUTHORS
Published December 16, 2022 | Version Published
Journal Article Open

Mapping the circumnuclear regions of the Circinus galaxy with the Imaging X-ray Polarimetry Explorer

Creators

  • 1. ROR icon Roma Tre University
  • 2. ROR icon Agenzia Spaziale Italiana
  • 3. ROR icon Observatory of Strasbourg
  • 4. ROR icon Massachusetts Institute of Technology
  • 5. ROR icon University of Turku
  • 6. ROR icon Space Research Institute
  • 7. ROR icon National Institute for Astrophysics
  • 8. ROR icon California Institute of Technology
  • 9. ROR icon University of Oxford
  • 10. ROR icon Newcastle University
  • 11. ROR icon Sapienza University of Rome
  • 12. ROR icon University of Rome Tor Vergata
  • 13. ROR icon Washington University in St. Louis
  • 14. ROR icon Astronomical Institute
  • 15. ROR icon INFN Sezione di Roma II
  • 16. ROR icon University of Maryland, College Park
  • 17. ROR icon Marshall Space Flight Center
  • 18. ROR icon Astronomical Observatory of Rome
  • 19. ROR icon Charles University
  • 20. ROR icon Instituto de Astrofísica de Andalucía
  • 21. ROR icon Osservatorio Astronomico di Cagliari
  • 22. ROR icon INFN Sezione di Pisa
  • 23. ROR icon University of Pisa
  • 24. ROR icon INFN Sezione di Torino
  • 25. ROR icon University of Turin
  • 26. ROR icon Arcetri Astrophysical Observatory
  • 27. ROR icon University of Florence
  • 28. ROR icon National Institute for Nuclear Physics
  • 29. ROR icon Stanford University
  • 30. ROR icon University of Tübingen
  • 31. ROR icon RIKEN
  • 32. ROR icon Yamagata University
  • 33. ROR icon University of British Columbia
  • 34. ROR icon Chuo University
  • 35. ROR icon Boston University
  • 36. ROR icon St Petersburg University
  • 37. ROR icon Nagoya University
  • 38. ROR icon Hiroshima University
  • 39. ROR icon University of Hong Kong
  • 40. ROR icon Pennsylvania State University
  • 41. ROR icon Institut de Planétologie et d'Astrophysique de Grenoble
  • 42. ROR icon Harvard-Smithsonian Center for Astrophysics
  • 43. ROR icon Brera Astronomical Observatory
  • 44. ROR icon University of Padua
  • 45. ROR icon University College London
  • 46. ROR icon University of Amsterdam
  • 47. ROR icon Guangxi University

Abstract

We report on the Imaging X-ray Polarimetry Explorer (IXPE) observation of the closest and X-ray brightest Compton-thick active galactic nucleus (AGN), the Circinus galaxy. We find the source to be significantly polarized in the 2–6 keV band. From previous studies, the X-ray spectrum is known to be dominated by reflection components, both neutral (torus) and ionized (ionization cones). Our analysis indicates that the polarization degree is 28 ± 7 per cent (at 68 per cent confidence level) for the neutral reflector, with a polarization angle of 18° ± 5°, roughly perpendicular to the radio jet. The polarization of the ionized reflection is unconstrained. A comparison with Monte Carlo simulations of the polarization expected from the torus shows that the neutral reflector is consistent with being an equatorial torus with a half-opening angle of 45°–55°. This is the first X-ray polarization detection in a Seyfert galaxy, demonstrating the power of X-ray polarimetry in probing the geometry of the circumnuclear regions of AGNs, and confirming the basic predictions of standard Unification Models.

Additional Information

The Imaging X ray Polarimetry Explorer (IXPE) is a joint US and Italian mission. The US contribution is supported by the National Aeronautics and Space Administration (NASA) and led and managed by its Marshall Space Flight Center (MSFC), with industry partner Ball Aerospace (contract NNM15AA18C). The Italian contribution is supported by the Italian Space Agency (Agenzia Spaziale Italiana, ASI) through contract ASI-OHBI-2017-12-I.0, agreements ASI-INAF-2017-12-H0 and ASI-INFN-2017.13-H0, and its Space Science Data Center (SSDC) with agreements ASI-INAF-2022-14-HH.0 and ASI-INFN 2021-43-HH.0, and by the Istituto Nazionale di Astrofisica (INAF) and the Istituto Nazionale di Fisica Nucleare (INFN) in Italy. This research used data products provided by the IXPE Team (MSFC, SSDC, INAF, and INFN) and distributed with additional software tools by the High-Energy Astrophysics Science Archive Research Center (HEASARC), at NASA Goddard Space Flight Center (GSFC). JPou and SST were supported by the Academy of Finland grants 349373 and 349906. AIng acknowledges support from the Royal Society. MDov, JSvo, and VKar acknowledge the support from the GACR project 21-06825X. POP acknowledges financial support from the French High Energy Program (PNHE/CNRS) and from the French spatial agency (CNES).

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Additional details

Identifiers

Eprint ID
119641
Resolver ID
CaltechAUTHORS:20230302-365859100.9

Funding

National Aeronautics and Space Administration
Marshall Space Flight Center
NNM15AA18C
Italian Space Agency
Agenzia Spaziale Italiana
ASI-OHBI-2017-12-I.0
Agenzia Spaziale Italiana
ASI-INAF-2017-12-H0
Agenzia Spaziale Italiana
ASI-INFN-2017.13-H0
Agenzia Spaziale Italiana
ASI-INAF-2022-14-HH.0
Agenzia Spaziale Italiana
ASI-INFN 2021-43-HH.0
INAF
Goddard Space Flight Center
Academy of Finland
349373
Academy of Finland
349906
Royal Society
CNRS
CNES

Dates

Created
2023-05-18
Created from EPrint's datestamp field
Updated
2023-05-18
Created from EPrint's last_modified field