Hard x-ray study of lobes of radio galaxy Fornax a naoki Isobe


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Hard X-ray study of lobes of radio galaxy Fornax A

  • Naoki Isobe

  • (RIKEN/Suzaku Help Desk)

  • Makoto Tashiro, Hiromi Seta, Yuichi Yaji (Saitama Univ.)

  • Keiko Matsuta, Hidehiro Kaneda (ISAS/JAXA),

  • Kazuo Makishima (RIKEN/Univ.of Tokyo) etc.


Radio Galaxy Fornax A

  • Nearby radio galaxy (D = 18.6 Mpc)

  • The 1st source, from which the lobe IC X-ray emission was detected with ASCA and ROSAT (e.g., Kaneda et al. 1995)

  • The flux of IC X-ray emission indicate a magnetic field of 1.2 G (Isobe et al. 2006) , which is slightly smaller than the field under the minimum energy condition (1.55G).

  • The X-ray/radio distribution suggest a homogeneous electron and edge-strengthened magnetic field distributions (Tashiro et al. 2001) .



Radio Galaxy Fornax A

  • Nearby radio galaxy (D = 18.6 Mpc)

  • The 1st source, from which the lobe IC X-ray emission was detected with ASCA and ROSAT (e.g., Kaneda et al. 1995)

  • The flux of IC X-ray emission indicate a magnetic field of 1.2 G (Isobe et al. 2006) , which is slightly smaller than the field under the minimum energy condition (1.55G).

  • The X-ray/radio distribution suggest a homogeneous electron and edge-strengthened magnetic field distributions (Tashiro et al. 2001) .



Radio Galaxy Fornax A

  • Nearby radio galaxy (D = 18.6 Mpc)

  • The 1st source, from which the lobe IC X-ray emission was detected with ASCA and ROSAT (e.g., Kaneda et al. 1995)

  • The flux of IC X-ray emission from the east lobe indicate a magnetic field of 1.2 G (Isobe et al. 2006) , which is slightly smaller than the field under the minimum energy condition (1.55G).

  • The X-ray/radio distribution suggest a homogeneous electron and edge-strengthened magnetic field distributions (Tashiro et al. 2001) .



What we have to do next

  • The Lorents factor of radio electrons is larger than that of X-ray ones

  • It is important to detect radio/X-ray emission from electrons with the same Lorentz factor.

  • 2 options

    • low-frequency radio
    • Hard X-ray
  • Low-frequency radio observation is difficult.

  • Hard X-ray observation with Suzaku is the ideal tool.



The X-ray Observatory Suzaku

  • The 5th Japanese X-ray satellite, launched July 10, 2005. (about 3 years old.)

  • 2 X-ray detectors

    • XIS (X-ray Imaging Spectrometer)
      • 3 CCD cameras active
        • 1 BI CCD (XIS1)
        • 2 FI CCD (XIS0, 3)
      • 0.2 – 10 keV
      • Low background
      • Good energy resolution
    • HXD (Hard X-ray Detector)
      • Si-PIN diode
      • : 10 – 60 keV
      • GSO scintillator
      • : 60 – 300 keV
      • Wide energy band
      • low background


Suzaku observation of Fornax A



Suzaku HXD/PIN Spectrum



Wide-band X-ray spectrum of the west lobe



Spectral Energy Distribution



Physical quantities in lobes



Future perspective



Summary

  • IC X-ray emission was detected up to 20 keV from the west lobe of Fornax A, with Suzaku HXD.

  • The X-ray spectrum of the west lobe is described with a PL model with  = 1.82±0.22 and S1keV = 137-29+34 nJy.

  • A comparison between the radio and X-ray fluxes gives B = 1.4±0.1 G, which is slightly smaller than the minimum energy field Bme = 1.59 G.

  • The X-ray photons of 20 keV corresponds to the electron Lorents factor of e ~ 5000. As a result, we have succeeded in connecting the electron spectra of synchrotron and IC emitting electrons.



References

  • Kaneda et al. 1995 ApJ 453, L13

  • Iyomoto et al. 1998 ApJ 503, L31

  • Tashiro et al. 2001 ApJ 546, L19

  • Isobe et al. 2006 ApJ 645, 256




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