X‐ray spectra of a large sample of quasars with ASCA

By J. Turner. 2000

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The results from an X-ray spectral analysis of a large sample of quasars, observed with ASCA, are presented. The sample was selected to include all ASCA observations of quasars, with z>0.05 and MV 99 per cent confidence, confirming the well-known trend between Γ and Hβ FWHM in Seyfert 1s, but at higher luminosities. Other spectral complexities are observed from this sample. A soft X-ray excess, with blackbody temperatures in the range 100–300 eV, is seen in many low-z radio-quiet quasars. In most cases the temperatures are probably too hot to originate directly from the disc and could imply that some reprocessing is involved. Iron K-line emission features are also found in the RQQs, but often from partially ionized material. Indeed, in the highest-luminosity RQQs there is neither evidence for iron line emission nor the reflection component expected from disc reflection models. These observations can be explained by an increase in the quasar accretion rate with luminosity, leading to an increase in the ionization state of the surface layers of the disc. The occurrence of ionized or ‘warm’ absorbers is rare in this sample, with only five detections in low-z objects. However, excess neutral X-ray absorption is found towards several of the high-z, predominantly radio-loud, quasars. Although found to increase with quasar redshift, this ‘intrinsic’ absorption may be associated with radio-loud active galactic nuclei.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/bc93ce28c404a1a1ea5eec1c3cbc3ffa7296184e

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Citations in the corpus

The Cosmic Lens All-Sky Survey - II. Gravitational lens candidate selection and follow-up (2002, background): “The system has been detected in X-rays (Chartas, 2000; Reeves & Turner, 2000).”
THREE-YEAR SWIFT–BAT SURVEY OF ACTIVE GALACTIC NUCLEI: RECONCILING THEORY AND OBSERVATIONS? (2010, background): “The correlation between the 2–10 keV photon index and the luminosity was found not to be significant in many papers (Reeves & Turner 2000; Bianchi et al. 2009a), and the significance is generally low also in the works where it is claimed as real (Dai et al. 2004; Saez et al. 2008).”
Are Quasar Jets Dominated by Poynting Flux? (2005, background): “Spectra below the break are hard, with a power-law index of the energy flux, F−αν , in the range 0.3 ≤ α ≤ 0.8 (Reeves & Turner 2000; Donato et al. 2001; Giommi et al. 2002).”
X-RAY SPECTRAL PROPERTIES OF THE BAT AGN SAMPLE (2008, unknown): “XMM Winter et al. (2008) 11.95 8924 26 RBS 476 03 49 23.2 -11 59 26.9 BL Lac – ASCA Reeves & Turner (2000) 109000 27 PGC 13946 03 50 23.8 -50 18 35.6 ?”
Cosmological Evolution of the Hard X-Ray Active Galactic Nucleus Luminosity Function and the Origin of the Hard X-Ray Background (2003, background): “There are arguments that the relative strength of the reflection component (apparently) decreases with the luminosity (e.g., Lawson & Turner 1997; Reeves & Turner 2000), is smaller in radio loud AGNs than radio quite ones (Zdziarski et al. 1995), and may be even different between Seyfert 1 and…”
X-Ray Spectroscopy of Quasi-Stellar Objects with Broad Ultraviolet Absorption Lines (2001, unknown): “…versus redshift is shown in Figure 2a. Excluding the apparent outlier H 1413+117, the mean photon index for our sample is Γ = 2.01 ± 0.13, entirely consistent with the range of Γ measured for large samples of low and high luminosity radio-quiet QSOs (e.g., George et al. 2000; Reeves & Turner 2000).”
Modeling the Radio Background from the First Black Holes at Cosmic Dawn: Implications for the 21 cm Absorption Amplitude (2018, background): “…energies (which are redshifted into the 0.5–2 keV band by z= 0) by assuming an X-ray spectral index of 0.9, typical of AGNs (Nandra & Pounds 1994; Reeves & Turner 2000; Page et al. 2005; Piconcelli et al. 2005), and a minimal X-ray energy of 0.5 keV due to self-absorption by the interstellar…”
BAT AGN Spectroscopic Survey. V. X-Ray Properties of the Swift/BAT 70-month AGN Catalog (2017, result): “%) studying X-ray observations of smaller samples of Swift/BAT AGN, and with previous works carried out with ASCA (∼ 40%, Reeves & Turner 2000).”
CAIXA: a catalogue of AGN in the XMM-Newton archive - II. Multiwavelength correlations (2009, background): “In particular, in the literature there are claims of a correlation between Γh and the 2–10 keV luminosity (e.g. Dai et al. 2004; Saez et al. 2008), but there are also several studies that do not find such a correlation (e.g. Reeves & Turner 2000; George et al. 2000; Winter et al. 2009).”
A Classic Type 2 QSO (2001, background): “We note that the absorption seen in CDF-S 202 of NHe1024 cm 2 is common for type 2 objects (Maiolino et al. 1998; Risaliti, Maiolino, & Salvati 1999) but not for type 1 objects (Reeves & Turner 2000).”
First X-ray-based statistical tests for clumpy-torus models: eclipse events from 230 years of monitoring of Seyfert AGN (2014, background): “Reeves & Turner (2000), fitting ASCA spectra obtained in 1993 November– December, found NH 1 × 1020 cm−2, implying an upper limit for the duration of the event of ∼ 4.5 yr.”
Quasars: the characteristic spectrum and the induced radiative heating (2003, background): “In particular, the 1–20 keV spectra of both radio-quiet and radio-loud type 1 quasars are characterized by α ≈ 0.8 (Lawson & Turner 1997; Reeves & Turner 2000; Hasenkopf, Smabruna & Eracleous 2002).”
Spectral Energy Distributions and Multiwavelength Selection of Type 1 Quasars (2006, result): “We then assume a flat (in νfν space, which has αx = −1.0) spectrum between 0.1 and 10 keV, roughly consistent with Reeves & Turner (2000) and George et al. (2000).”
The Hard X-Ray Spectral Slope as an Accretion Rate Indicator in Radio-quiet Active Galactic Nuclei (2006, background): “…(z 0.5) type 1 radio-quiet quasars (RQQs) have consistently shown thatG ∼ 2.0 0.5, and some of those studies confirmed the Brandt et al. (1997) G–FWHM(Hb) relationship (e.g., Leighly 1999; Reeves & Turner 2000; Porquet et al. 2004; Piconcelli et al. 2005, hereafter P05; Brocksopp et al. 2006).”
The Hard X-Ray Spectrum as a Probe for Black Hole Growth in Radio-Quiet Active Galactic Nuclei (2008, background): “…X-ray studies of nearby (z <∼ 0.5) unobscured RQ AGNs have confirmed the Brandt et al. (1997) Γ-FWHM(Hβ ) anticorrelation (e.g., Leighly 1999; Reeves & Turner 2000; Porquet et al. 2004; Piconcelli et al. 2005; Brocksopp et al. 2006), and others have found significant correlations betweenΓ…”
X-Ray Emission from Radio-Quiet Quasars in the Sloan Digital Sky Survey Early Data Release: The αox Dependence upon Ultraviolet Luminosity (2002, background): “Samples of z 0–2 RQQs are well fitted in the 2–10 keV band by power-law continua with C = 1.7–2.3 (e.g., George et al. 2000; Mineo et al. 2000; Reeves & Turner 2000).”
The synthesis of the cosmic X-ray background in the Chandra and XMM-Newton era (2006, background): “Also, a large obscured QSOs fraction (RQ ≥ 2) does not provide an acceptable solution.”