X-Ray Properties of LINERs and Low-Luminosity Seyfert Galaxies Observed with ASCA. I. Observations and Results

By Y. Terashima, N. Iyomoto, Luis C. Ho, A. Ptak. 2002

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This paper presents a comprehensive study of the X-ray properties of low-ionization nuclear emission-line regions (LINERs) and low-luminosity Seyfert galaxies based on observations obtained with the ASCA satellite. We analyzed data of 53 observations of 21 LINERs and 17 low-luminosity Seyferts. X-ray emission has been detected in all but one object. The X-ray luminosities in the 2-10 keV band range from 4 × 1039 to 5 × 1041 ergs s-1, which are 1-3 orders of magnitude smaller than in classical Seyfert galaxies. The X-ray spectra of most objects are well described by a canonical model which consists of (1) a soft component from a thermal plasma with kT < 1 keV and (2) a hard component represented by a power law with a photon index of Γ ≈ 1.8 or thermal bremsstrahlung emission with kT ≈ 10 keV. Several objects do not require the soft thermal component, and their continua are well fitted by a single power-law model. Some objects show heavy absorption with column densities in excess of 1023 cm-2. We detect in several objects Fe K line emission with equivalent widths ranging from 50 eV to 2 keV. Variability on timescales less than a day is uncommon in our sample. By comparing multiple observations made with ASCA or with published 2-10 keV observations from other satellites, we show that at least eight objects are variable on timescales of a week to several years. We find that the morphologies of many objects, both in the soft and hard bands, are consistent with being pointlike relative to the telescope point-spread function; a few are clearly extended in either or both energy bands. The second paper of this series will discuss the physical interpretation of the X-ray emission and its implications for low-luminosity active galactic nuclei.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/fc1349aac2de45e24e45f424d72b94a4fb53bafb

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Citations in the corpus

Nuclear Activity in Nearby Galaxies (2008, methodology): “Early X-ray observations of LLAGNs using ASCA have consistently revealed the presence of a diffuse, thermal component, typically with a temperature of kT ≈ 0.5 keV (Ptak et al. 1999; Terashima et al. 2002).”
Radiative efficiency, variability and Bondi accretion on to massive black holes: the transition from radio AGN to quasars in brightest cluster galaxies (2012, background): “For an ADAF, the X-ray emission is radiated from a relatively large volume and variation is expected on timescales longer than around a day (Ptak et al. 1998; Terashima et al. 2002).”
The 2-10 keV luminosity as a Star Formation Rate indicator (2002, methodology): “Therefore we believe that the HFS97 classification is reliable and that our sample is not polluted by AGN.”
Measuring the kinetic power of active galactic nuclei in the radio mode (2007, unknown): “…(4) Rafferty et al. (2006); (5) Carilli & Barthel (1996); (6) Nagar et al. (2005); (6) De Ruiter et al. (1986); (7) Pellegrini (2005b); (8) Allen et al. (2006); (9) Allen et al. (2001); (10) Fabian et al. (2002); (11) Terashima et al. (2002); (12) Di Matteo et al. (2003); (13) Macchetto etal.”
THE NGC 404 NUCLEUS: STAR CLUSTER AND POSSIBLE INTERMEDIATE-MASS BLACK HOLE (2010, background): “The hot dust luminosity is somewhat larger than the [O III] luminosity (assuming D=3.06 Mpc) of 2 × 1037 ergs s−1 (Ho et al. 1997) and the possible hard X-ray component with 2-10 keV luminosity of ∼ 3×1037 ergs s−1 noted by Terashima et al. (2002).”
On the X-ray, optical emission line and black hole mass properties of local Seyfert galaxies ! (2006, unknown): “Col. (6): X-RAY REFERENCES: (1) Cappi et al. (2006); (2) this work; (3) Pappa et al. (2001); (4) Guainazzi et al. (2005); (5) Terashima et al. (2002); (6) Eracleous et al. (2002); Col. (7): Final classification: “ √ ”=Compton thick candidates, “×”=Compton thin candidate and “?””
A Fundamental plane of black hole activity (2003, background): “X-ray studies at arcsecond (or sub-arcsecond) resolution with theChandraX-ray Observatory have also allowed us to firmly pin down the emission properties of the nearby dim galactic nuclei through systematic surveys of LLAGN (Ho et al. 2001; Terashima et al. 2002; Terashima & Wilson 2003).”
X-ray spectral survey with XMM-Newton of a complete sample of nearby Seyfert galaxies (2005, background): “Recent studies performed with the last generation X-ray observatories have extended the X-ray spectral analysis down to lower luminosities, sometimes also comparing Seyferts with LINERs (Heckman 1980) and/or H II-starburst galaxies (e.g., Terashima et al. 2002, Georgantopoulos et al. 2002).”
The subarcsecond mid-infrared view of local active galactic nuclei – II. The mid-infrared–X-ray correlation (2015, background): “On the other hand, NGC 4945 is Compton-thick obscured in X-rays exhibiting a highly variable and complex spectrum (e.g., c© 2015 RAS, MNRAS 000, 1–??”