Detection of excess hard X-ray emission from the optical jet galaxy NGC 1097

Naoko Iyomoto, Kazuo Makishima, Yasushi Fukazawa, Makoto Tashiro, Yoshitaka Ishisaki, Naomasa Nakai, Yoshiaki Taniguchi

Research output: Contribution to journalArticle

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Abstract

Using the ASCA observatory, X-ray observations were made of the spiral galaxy NGC 1097, which exhibits four optical jets. Hard X-ray emission from a point-like source at the nucleus was detected at a 2-10 keV luminosity of 1 × 1041 erg s-1 for an assumed distance of 24 Mpc. The 2-10 keV spectrum was well fitted with a power-law of photon index ∼ 1.8. Although no X-ray variability was detected during a ∼ 40 ks pointing, the observed X-ray to optical luminosity ratio of NGC 1097 is too high for the X-ray emission to be explained by an assembly of discrete X-ray sources. From our results and optical activity, the existence of a low-luminosity active galactic nucleus (LLAGN) is strongly suggested. In the soft X-ray band (0.5-2 keV) a thin thermal emission with a temperature kT ∼ 0.6 keV was also detected, which is understood to be emission from hot gas associated with starburst activity.

Original languageEnglish
Pages (from-to)231-236
Number of pages6
JournalPublications of the Astronomical Society of Japan
Volume48
Issue number2
DOIs
Publication statusPublished - Jan 1 1996

Fingerprint

galaxies
x rays
luminosity
optical activity
high temperature gases
thermal emission
spiral galaxies
detection
active galactic nuclei
erg
point sources
observatories
power law
observatory
assembly
nuclei
photons
gas
temperature

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Detection of excess hard X-ray emission from the optical jet galaxy NGC 1097. / Iyomoto, Naoko; Makishima, Kazuo; Fukazawa, Yasushi; Tashiro, Makoto; Ishisaki, Yoshitaka; Nakai, Naomasa; Taniguchi, Yoshiaki.

In: Publications of the Astronomical Society of Japan, Vol. 48, No. 2, 01.01.1996, p. 231-236.

Research output: Contribution to journalArticle

Iyomoto, N, Makishima, K, Fukazawa, Y, Tashiro, M, Ishisaki, Y, Nakai, N & Taniguchi, Y 1996, 'Detection of excess hard X-ray emission from the optical jet galaxy NGC 1097', Publications of the Astronomical Society of Japan, vol. 48, no. 2, pp. 231-236. https://doi.org/10.1093/pasj/48.2.231
Iyomoto, Naoko ; Makishima, Kazuo ; Fukazawa, Yasushi ; Tashiro, Makoto ; Ishisaki, Yoshitaka ; Nakai, Naomasa ; Taniguchi, Yoshiaki. / Detection of excess hard X-ray emission from the optical jet galaxy NGC 1097. In: Publications of the Astronomical Society of Japan. 1996 ; Vol. 48, No. 2. pp. 231-236.
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AU - Ishisaki, Yoshitaka

AU - Nakai, Naomasa

AU - Taniguchi, Yoshiaki

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AB - Using the ASCA observatory, X-ray observations were made of the spiral galaxy NGC 1097, which exhibits four optical jets. Hard X-ray emission from a point-like source at the nucleus was detected at a 2-10 keV luminosity of 1 × 1041 erg s-1 for an assumed distance of 24 Mpc. The 2-10 keV spectrum was well fitted with a power-law of photon index ∼ 1.8. Although no X-ray variability was detected during a ∼ 40 ks pointing, the observed X-ray to optical luminosity ratio of NGC 1097 is too high for the X-ray emission to be explained by an assembly of discrete X-ray sources. From our results and optical activity, the existence of a low-luminosity active galactic nucleus (LLAGN) is strongly suggested. In the soft X-ray band (0.5-2 keV) a thin thermal emission with a temperature kT ∼ 0.6 keV was also detected, which is understood to be emission from hot gas associated with starburst activity.

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