Abstract
The origin of the narrow Fe-Kα fluorescence line at 6.4 keV from active galactic nuclei has long been under debate; some of the possible sites are the outer accretion disk, the broad line region, a molecular torus, or interstellar/intracluster media. In 2016 February-March, we performed the first X-ray microcalorimeter spectroscopy with the Soft X-ray Spectrometer (SXS) on board the Hitomi satellite of the Fanaroff-Riley type I radio galaxy NGC 1275 at the center of the Perseus cluster of galaxies. With the high-energy resolution of ∼5 eV at 6 keV achieved by Hitomi/SXS, we detected the Fe-Kα line with ∼5.4 σ significance. The velocity width is constrained to be 500-1600 km s−1 (FWHM for Gaussian models) at 90% confidence. The SXS also constrains the continuum level from the NGC 1275 nucleus up to ∼20 keV, giving an equivalent width of ∼20 eV for the 6.4 keV line. Because the velocity width is narrower than that of the broad Hα line of ∼2750 km s−1, we can exclude a large contribution to the line flux from the accretion disk and the broad line region. Furthermore, we performed pixel map analyses on the Hitomi/SXS data and image analyses on the Chandra archival data, and revealed that the Fe-Kα line comes from a region within ∼1.6 kpc of the NGC 1275 core, where an active galactic nucleus emission dominates, rather than that from intracluster media. Therefore, we suggest that the source of the Fe-Kα line from NGC 1275 is likely a low-covering-fraction molecular torus or a rotating molecular disk which probably extends from a parsec to hundreds of parsecs scale in the active galactic nucleus system.
| Original language | English |
|---|---|
| Article number | psx147 |
| Journal | Publications of the Astronomical Society of Japan |
| Volume | 70 |
| Issue number | 2 |
| DOIs | |
| Publication status | Published - 2018 Mar 1 |
Fingerprint
Keywords
- Galaxies: active
- Galaxies: individual (NGC 1275)
- Galaxies: radio galaxy
- Methods: observational
- X-rays: galaxies
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science
Cite this
Hitomi observation of radio galaxy NGC 1275 : The first X-ray microcalorimeter spectroscopy of Fe-Kα line emission from an active galactic nucleus. / Hitomi Collaboration.
In: Publications of the Astronomical Society of Japan, Vol. 70, No. 2, psx147, 01.03.2018.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Hitomi observation of radio galaxy NGC 1275
T2 - The first X-ray microcalorimeter spectroscopy of Fe-Kα line emission from an active galactic nucleus
AU - Hitomi Collaboration
AU - Aharonian, Felix
AU - Akamatsu, Hiroki
AU - Akimoto, Fumie
AU - Allen, Steven W.
AU - Angelini, Lorella
AU - Audard, Marc
AU - Awaki, Hisamitsu
AU - Axelsson, Magnus
AU - Bamba, Aya
AU - Bautz, Marshall W.
AU - Blandford, Roger
AU - Brenneman, Laura W.
AU - Brown, Gregory V.
AU - Bulbul, Esra
AU - Cackett, Edward M.
AU - Chernyakova, Maria
AU - Chiao, Meng P.
AU - Coppi, Paolo S.
AU - Costantini, Elisa
AU - De Plaa, Jelle
AU - De Vries, Cor P.
AU - Den Herder, Jan Willem
AU - Done, Chris
AU - Dotani, Tadayasu
AU - Ebisawa, Ken
AU - Eckart, Megan E.
AU - Enoto, Teruaki
AU - Ezoe, Yuichiro
AU - Fabian, Andrew C.
AU - Ferrigno, Carlo
AU - Foster, Adam R.
AU - Fujimoto, Ryuichi
AU - Fukazawa, Yasushi
AU - Furuzawa, Akihiro
AU - Galeazzi, Massimiliano
AU - Gallo, Luigi C.
AU - Gandhi, Poshak
AU - Giustini, Margherita
AU - Goldwurm, Andrea
AU - Gu, Liyi
AU - Guainazzi, Matteo
AU - Haba, Yoshito
AU - Hagino, Kouichi
AU - Hamaguchi, Kenji
AU - Harrus, Ilana M.
AU - Hatsukade, Isamu
AU - Hayashi, Katsuhiro
AU - Hayashi, Takayuki
AU - Hayashida, Kiyoshi
AU - Kubota, Aya
PY - 2018/3/1
Y1 - 2018/3/1
N2 - The origin of the narrow Fe-Kα fluorescence line at 6.4 keV from active galactic nuclei has long been under debate; some of the possible sites are the outer accretion disk, the broad line region, a molecular torus, or interstellar/intracluster media. In 2016 February-March, we performed the first X-ray microcalorimeter spectroscopy with the Soft X-ray Spectrometer (SXS) on board the Hitomi satellite of the Fanaroff-Riley type I radio galaxy NGC 1275 at the center of the Perseus cluster of galaxies. With the high-energy resolution of ∼5 eV at 6 keV achieved by Hitomi/SXS, we detected the Fe-Kα line with ∼5.4 σ significance. The velocity width is constrained to be 500-1600 km s−1 (FWHM for Gaussian models) at 90% confidence. The SXS also constrains the continuum level from the NGC 1275 nucleus up to ∼20 keV, giving an equivalent width of ∼20 eV for the 6.4 keV line. Because the velocity width is narrower than that of the broad Hα line of ∼2750 km s−1, we can exclude a large contribution to the line flux from the accretion disk and the broad line region. Furthermore, we performed pixel map analyses on the Hitomi/SXS data and image analyses on the Chandra archival data, and revealed that the Fe-Kα line comes from a region within ∼1.6 kpc of the NGC 1275 core, where an active galactic nucleus emission dominates, rather than that from intracluster media. Therefore, we suggest that the source of the Fe-Kα line from NGC 1275 is likely a low-covering-fraction molecular torus or a rotating molecular disk which probably extends from a parsec to hundreds of parsecs scale in the active galactic nucleus system.
AB - The origin of the narrow Fe-Kα fluorescence line at 6.4 keV from active galactic nuclei has long been under debate; some of the possible sites are the outer accretion disk, the broad line region, a molecular torus, or interstellar/intracluster media. In 2016 February-March, we performed the first X-ray microcalorimeter spectroscopy with the Soft X-ray Spectrometer (SXS) on board the Hitomi satellite of the Fanaroff-Riley type I radio galaxy NGC 1275 at the center of the Perseus cluster of galaxies. With the high-energy resolution of ∼5 eV at 6 keV achieved by Hitomi/SXS, we detected the Fe-Kα line with ∼5.4 σ significance. The velocity width is constrained to be 500-1600 km s−1 (FWHM for Gaussian models) at 90% confidence. The SXS also constrains the continuum level from the NGC 1275 nucleus up to ∼20 keV, giving an equivalent width of ∼20 eV for the 6.4 keV line. Because the velocity width is narrower than that of the broad Hα line of ∼2750 km s−1, we can exclude a large contribution to the line flux from the accretion disk and the broad line region. Furthermore, we performed pixel map analyses on the Hitomi/SXS data and image analyses on the Chandra archival data, and revealed that the Fe-Kα line comes from a region within ∼1.6 kpc of the NGC 1275 core, where an active galactic nucleus emission dominates, rather than that from intracluster media. Therefore, we suggest that the source of the Fe-Kα line from NGC 1275 is likely a low-covering-fraction molecular torus or a rotating molecular disk which probably extends from a parsec to hundreds of parsecs scale in the active galactic nucleus system.
KW - Galaxies: active
KW - Galaxies: individual (NGC 1275)
KW - Galaxies: radio galaxy
KW - Methods: observational
KW - X-rays: galaxies
UR - http://www.scopus.com/inward/record.url?scp=85058321980&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85058321980&partnerID=8YFLogxK
U2 - 10.1093/pasj/psx147
DO - 10.1093/pasj/psx147
M3 - Article
AN - SCOPUS:85058321980
VL - 70
JO - Publication of the Astronomical Society of Japan
JF - Publication of the Astronomical Society of Japan
SN - 0004-6264
IS - 2
M1 - psx147
ER -