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

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