<i>XMM-Newton</i>Observations of High-Redshift Quasars

Grupe, D.; Mathur, S.; Wilkes, B. J.; Osmer, Patrick S.

doi:10.1086/498260

Cited by 42 publications

(64 citation statements)

References 101 publications

(168 reference statements)

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“…Remarkably, such a value is very similar to those reported from XMM-Newton observations of all the other obscured Blazars at high z for which, bearing in mind the small number statistics, the measured column densities of the absorbers seem to narrowly cluster around N H ≈ 10 22 cm −2 (e.g. F03; W04; Yuan et al 2005;Grupe et al 2005). N H values 10 22 cm −2 are, however, hard to detect at high redshifts and, hence, a selection effect is likely present.…”

Section: Discussionsupporting

confidence: 86%

XMM-Newton discovery of soft X-ray absorption in the high-z superluminous Blazar RBS 315

Piconcelli¹,

Guainazzi²

2005

A&A

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We present the analysis and the results of a 20 ks XMM-Newton observation of the extremely X-ray loud (L X ≈ 5 × 10 47 erg s −1 ) flatspectrum radio quasar RBS 315 at a redshift of 2.69. This EPIC observation has allowed us to strongly constrain the slope of the continuum (Γ = 1.23 ± 0.01) as well as to discover the presence of a sharp drop below ≈2 keV in its spectrum. Such a flat photon index and the huge luminosity suggest that the X-ray emission is due to the low energy tail of the Comptonized spectrum, produced from plasma in a relativistic jet oriented close to our line of sight. Even though the hypothesis of a break in the continuum cannot be completely discarded as an explanation of the soft X-ray cutoff, the presence of intrinsic absorption appears more plausible. Spectral fits with cold (N +38−12 erg cm −2 s −1 ) absorbers are statistically indistinguishable. Remarkably, our results are very similar to those reported so far for other absorbed high-z Blazars observed by XMM-Newton. The existence of this "homogeneous" class of jet-dominated superluminous obscured QSOs at high z therefore could be important in the context of the formation and cosmological evolution of radio-loud objects.

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Section: Discussionsupporting

confidence: 86%

XMM-Newton discovery of soft X-ray absorption in the high-z superluminous Blazar RBS 315

Piconcelli¹,

Guainazzi²

2005

A&A

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“…The 1–10 keV part of the observed spectra of AGN is usually modelled as a simple power law with exponential lower and upper cut‐offs specified by ν min and ν max , respectively, where f (ν) is the flux per unit frequency interval and α(>0) is the energy spectral index. For most quasars, the X‐ray spectral index lies in the range 0.7 < α < 0.9 as shown by Wilkes & Elvis (1987) and also recently by Grupe et al (2006) and Lopez (2006). However, some objects show extreme values like α < 0 or α > 2.…”

Section: Constraints and Assumptionssupporting

confidence: 61%

Properties of warm absorbers in active galaxies: a systematic stability curve analysis

Chakravorty

Kembhavi

Elvis

et al. 2009

Monthly Notices of the Royal Astronomical Society

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Signatures of warm absorbers are seen in soft X‐ray spectra of about half of all type 1 Seyfert galaxies observed and in some quasars and blazars. We use the thermal equilibrium curve to study the influence of the shape of the ionizing continuum, density and the chemical composition of the absorbing gas on the existence and nature of the warm absorbers. We describe circumstances in which a stable warm absorber can exist as a multiphase medium or one with continuous variation in pressure. In particular, we find the following results: (i) the warm absorber exists only if the spectral index of the X‐ray power‐law ionizing continuum α > 0.2 and has a multiphase nature if α∼ 0.8, which interestingly is the spectral index for most of the observed type 1 Seyfert galaxies; (ii) thermal and ionization states of highly dense warm absorbers are sensitive to their density if the ionizing continuum is sufficiently soft, i.e. dominated by the ultraviolet; (iii) absorbing gas with super‐solar metallicity is more likely to have a multiphase nature and (iv) the nature of the warm absorber is significantly influenced by the absence of iron and associated elements which are produced in the later stages of star formation history in Type Ia supernovae.

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“…Numerous previous studies have searched for a luminosity and redshift dependence of ox ¼ À0:384 log L X /L UV , the ratio of X-ray to UV/optical flux (e.g., Avni & Tananbaum 1982;Wilkes et al 1994;Yuan et al 1998;Vignali et al 2003a;Strateva et al 2005;Steffen et al 2006;, and À X , the X-ray spectra slope (e.g., Reeves & Turner 2000;Bechtold et al 2003;Dai et al 2004;Risaliti & Elvis 2005;Grupe et al 2006). Most studies have found a correlation between ox and UV luminosity, L UV , while the existence of a correlation between ox and z is still a matter of debate (e.g., Bechtold et al 2003;Vignali et al 2003a;Steffen et al 2006;Just et al 2007;.…”

Section: Introductionmentioning

confidence: 99%

Observational Constraints on the Dependence of Radio‐Quiet Quasar X‐Ray Emission on Black Hole Mass and Accretion Rate

Kelly

Bechtold

Trump

et al. 2008

ASTROPHYS J SUPPL S

126

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In this work we use a sample of 318 radio-quiet quasars (RQQs) to investigate the dependence of the ratio of optical/UV flux to X-ray flux, ox , and the X-ray photon index, À X , on black hole mass, UV relative to Eddington luminosity, and X-ray relative to Eddington luminosity. Our sample is drawn from the literature, with X-ray data from ROSAT and Chandra, and optical data mostly from the SDSS; 153 of these sources have estimates of À X from Chandra. We estimate M BH using standard estimates derived from the H, Mg ii, and C iv broad emission lines. Our sample spans a broad range in black hole mass (10 6 P M BH /M P 10 10 ), redshift (0 < z < 4:8), and luminosity (10 43 P kL k (2500 8)½ergs s À1 P 10 48 ). We find that ox increases with increasing M BH and L UV /L Edd and decreases with increasing L X /L Edd . In addition, we confirm the correlation seen in previous studies between À X and M BH and both L UV /L Edd and L X /L Edd ; however, we also find evidence that the dependence of À X of these quantities is not monotonic, changing sign at M BH $ 3 ; 10 8 M . We argue that the ox correlations imply that the fraction of bolometric luminosity emitted by the accretion disk, as compared to the corona, increases with increasing accretion rate relative to the Eddington rate,ṁ. In addition, we argue that the À X trends are caused by a dependence of X-ray spectral index onṁ. We discuss our results within the context of accretion models with Comptonizing corona and discuss the implications of the ox correlations for quasar feedback. To date, this is the largest study of the dependence of RQQ X-ray parameters on black hole mass and related quantities, and the first to attempt to correct for the large statistical uncertainty in the broad-line mass estimates.

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XMM-NewtonObservations of High-Redshift Quasars

Cited by 42 publications

References 101 publications

XMM-Newton discovery of soft X-ray absorption in the high-z superluminous Blazar RBS 315

XMM-Newton discovery of soft X-ray absorption in the high-z superluminous Blazar RBS 315

Properties of warm absorbers in active galaxies: a systematic stability curve analysis

Observational Constraints on the Dependence of Radio‐Quiet Quasar X‐Ray Emission on Black Hole Mass and Accretion Rate

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