ASCAObservations of Type 2 Seyfert Galaxies. I. Data Analysis Results

Abstract

We present ASCA spatial, temporal, and spectral data for a sample of 26 observations of 25 type 2 active galactic nuclei (AGNs), composed of 17 Seyfert 2 galaxies and eight narrow emission line galaxies (NELGs). Twenty-four of the 25 sources were detected.The ASCA images are generally consistent with emission from point sources at energies above D3 keV. We use archival ROSAT data to examine each Ðeld at high spatial resolution and to check for the presence of sources that would contaminate the ASCA data.Of the Ðve sources bright enough for 128 s temporal analysis, three are variable at [99% conÐdence, with characteristics consistent with those observed in Seyfert 1 galaxies. Analysis on a timescale of 5760 s reveals six sources variable at [99% conÐdence, and comparison with previous X-ray results shows most of the sample to be variable in hard X-ray Ñux on timescales of years.Simple continuum models are Ðtted to the sample spectra to characterize the variety of spectral forms and hence to determine the fundamental nature of the X-ray spectrum of each source. No single spectral model provides an adequate Ðt to all the sample sources. Thirty-six percent of the sample cannot be adequately Ðtted by any of our test models (all rejected at [95% conÐdence). Approximately half of the sample have an iron Ka line with an equivalent width consistent with an origin in the line-of-sight absorber ; the remaining lines must be produced in material out of the line of sight. Absorbing columns up to 1024 atoms cm~2 are detected, and even larger columns are inferred for some sources. The mean underlying hard X-ray power-law index is ! D 2.Many X-ray emission lines were detected at high levels of conÐdence. The iron K-shell regime is dominated by emission from "" neutral ÏÏ material. Many data sets also show evidence for complexity in the iron Ka proÐle, which may be interpreted as evidence for broad-line proÐles, including Ñux both redward and blueward of the line peak, and/or for the existence of hydrogen-like and helium-like iron K lines.Hydrogen-like and helium-like lines are detected from Fe, Ne, Si, S, and Ar in addition to Mg lines. While almost half of the sample have an estimated starburst contribution of [30% in the 0.5È4.5 keV bandpass, the soft X-ray emission lines are not solely associated with a strong starburst component.

X-ray imaging of the ionisation cones in NGC 5252

“…The investigation on the true nature of this soft X-ray component will be the subject of the next sections. Here it is important to note that whatever the fitting of the data below ∼1 keV, the best-fit model for the nuclear emission of NGC 5252 above ∼1 keV is typical in shape, but flatter (Γ ∼ 1.4-1.5) than normally found from Seyfert 2 galaxies (Γ = 1.5-2.5, Turner & Pounds 1989;Turner et al 1997; Cappi et al 2006;Dadina 2008). It is however consistent with the previous ASCA measurement (Γ ∼ 1-1.5, Cappi et al 1996), confirming the need in this source for a more complex absorption (either multiple, ionised or both) to recover a steeper canonical photon index.…”

“…It has been well known since the early days of X-ray spectroscopy that excess emission above the extrapolation of the absorbed nuclear radiation is present in almost all bright Seyfert 2s (Turner et al 1997). This excess appears smooth when measured with instruments with moderate energy resolutions like CCD.…”

BAT AGN Spectroscopic Survey. VIII. Type 1 AGN with Massive Absorbing Columns

“…Under the simple picture of a static dusty torus around an AGN, both optical and X-ray measurements of the gas column density should agree. To a large extent this is true, as many studies find that Type 1 AGNs show little to no X-ray absorption, while most Type 2 AGNs are X-ray absorbed with N H 10 22 cm −2 (e.g., Smith & Done 1996;Turner et al 1997;Risaliti et al 1999;Garcet et al 2007;Mainieri et al 2007;Tajer et al 2007;Antonucci 2012;Malizia et al 2012;Merloni et al 2014;Davies et al 2015) in accordance with the unified model. Of course, the unified model, while broadly successful in explaining the diversity of AGNs, is simplified and investigations of differences between Type 1 and Type 2 AGNs that cannot be explained by this paradigm can help to reveal the complex nature of AGNs.…”

The history of the iron Kαline profile in the Piccinotti AGN ESO 198-G24

“…However, often the observed profiles do not match the theoretical calculations (Fabian et al 1989;Laor 1991;Matt et al 1992). Electron scattering, as often observed in type 2 Seyferts (Ueno et al 1994;Turner et al 1997;Matt et al 2000), may help reconciling the difference between observed and theoretical line profiles produced in X-ray illuminated, relativistic accretion disks Matt et al 2001). Other pieces of evidence suggest constraints on the nature of the accretion: the disk may be truncated at a radius where relativistically broadened wings are negligible (see, Send offprint requests to: M. Guainazzi, e-mail: mguainaz@xmm.vilspa.esa.es e.g.…”