Volume 527, March 2011
|Number of page(s)||10|
|Published online||11 February 2011|
Suzaku observation of the LINER NGC 4102
IESL, Foundation for Research and Technology, 711 10
e-mail: firstname.lastname@example.org; email@example.com
2 Physics Department, University of Crete, PO Box 2208, 710 03 Heraklion, Crete, Greece
3 Department of Physics and Astronomy, Leicester University, LE1 7RH, UK
4 Instituto de Astrofísica de Andalucía (CSIC), Granada, Spain
5 Instituto de Astrofísica de Canarias (IAC), C/Via Lactea, s/n, 38205 La Laguna, Tenerife, Spain
6 Departamento de Astrofísica, Universidad de La Laguna, 38205 La Laguna, Tenerife, Spain
7 Grupo de Mecánica Espacial and Instituto Universitario de Matemática y Aplicaciones, Universidad de Zaragoza, 50009 Zaragoza, Spain
8 SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA, Utrecht, The Netherlands
9 NASA Goddard Space Flight Center, Astrophysics Science Division, Greenbelt, MD 20771, USA
Received: 8 November 2010
Accepted: 13 December 2010
Context. Low-ionisation, nuclear emission-line region (LINER) nuclei are said to be different from other active galactic nuclei (AGN) due to the presence of complex absorbing structures along the line-of-sight and/or an inefficient mode of accretion onto the supermassive black hole. However, this is still open.
Aims. We investigate the broad band X-ray spectrum of NGC 4102, one of the most luminous LINERs in the Swift/BAT survey.
Methods. We studied a 80 ks Suzaku spectrum of NGC 4102, together with archival Chandra and Swift/BAT observations. We also studied the optical (3.5 m/TWIN at Calar Alto observatory) and near-infrared (WHT/LIRIS at Observatorio Roque los Muchachos) spectra that were taken at the same time as the Suzaku data.
Results. There is strong evidence that NGC 4102 is a Compton-thick AGN, as suggested by the Swift/BAT detected intrinsic continuum and the presence of a strong narrow, neutral FeKα emission line. We have also detected ionised FeXXV emission lines in the Suzaku spectrum of the source. NGC 4102 shows a variable soft excess found at a significantly higher flux state at the time of Suzaku observations when compared to Chandra observations. Finally, a complex structure of absorbers is seen with at least two absorbers besides the Compton-thick one, derived from the X-ray spectral analysis and the optical extinction.
Conclusions. All the signatures described in this paper strongly suggest that NGC 4102 is a Compton-thick Type-2 AGN from the X-ray point of view. The “soft excess”, the electron scattered continuum component, and the ionised iron emission line might arise from Compton-thin material photoionised by the AGN. From variability and geometrical arguments, this material should be located somewhere between 0.4 and 2 pc away from the nuclear source, inside the torus and perpendicular to the disc. The bolometric luminosity (Lbol = 1.4 × 1043 erg s-1) and accretion rate (ṁEdd = 5.4 × 10-3) are consistent with other low-luminosity AGN. However, the optical and near infrared spectra correspond to that of a LINER source. We suggest that the LINER classification might be due a different spectral energy distribution according to its steeper spectral index.
Key words: galaxies: active / galaxies: nuclei / galaxies: Seyfert / galaxies: individual: NGC 4102 / X-ray: galaxies
© ESO, 2011
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.