The spectrum of the cosmic X-ray background observed by RTXE/PCA

Revnivtsev, M.; Gilfanov, M.; Sunyaev, R.; Jahoda, K.; Markwardt, C.

doi:10.1051/0004-6361:20031386

Cited by 115 publications

(127 citation statements)

References 32 publications

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“…We found that the normalization of the powerlaw component expected from deep CXB studies using several different satellites is lower by factors 0.77-0.62 compared to our best fit normalization. We then froze the powerlaw normalization to the highest (Vecchi et al 1999) and lowest (Revnivtsev et al 2003) normalization we found in the literature, resulting in temperatures 6.08 +0.98 −0.82 and 6.84 +1.17 −0.72 keV, respectively, in the third bin. This procedure results in worse fits but note that, in the latter case, the temperature is significantly hotter than when leaving the powerlaw normalization free.…”

Section: Discussionmentioning

confidence: 99%

Suzakumeasurement of Abell 2204's intracluster gas temperature profile out to 1800 kpc

Reiprich

Hudson

Zhang

et al. 2009

A&A

105

102

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Context. Measurements of intracluster gas temperatures out to large radii, where much of the galaxy cluster mass resides, are important for using clusters for precision cosmology and for studies of cluster physics. Previous attempts to measure robust temperatures at cluster virial radii have failed. Aims. The goal of this work is to measure the temperature profile of the very relaxed symmetric galaxy cluster Abell 2204 out to large radii, possibly reaching the virial radius. Methods. Taking advantage of its low particle background due to its low-Earth orbit, Suzaku data are used to measure the outer temperature profile of Abell 2204. These data are combined with Chandra and XMM-Newton data of the same cluster to make the connection to the inner regions, unresolved by Suzaku, and to determine the smearing due to Suzaku's point spread function. Results. The temperature profile of Abell 2204 is determined from ∼10 kpc to ∼1800 kpc, close to an estimate of r 200 (the approximation to the virial radius). The temperature rises steeply from below 4 keV in the very center up to more than 8 keV in the intermediate range and then decreases again to about 4 keV at the largest radii. Varying the measured particle background normalization artificially by ±10% does not change the results significantly. Several additional systematic effects are quantified, e.g., those due to the point spread function and astrophysical fore-and backgrounds. Predictions for outer temperature profiles based on hydrodynamic simulations show good agreement. In particular, we find the observed temperature profile to be slightly steeper but consistent with a drop of a factor of 0.6 from 0.3 r 200 to r 200 , as predicted by simulations. Conclusions. Intracluster gas temperature measurements up to r 200 seem feasible with Suzaku, after a careful analysis of the different background components and the effects of the point spread function. Such measurements now need to be performed for a statistical sample of clusters. The result obtained here indicates that numerical simulations capture the intracluster gas physics well in cluster outskirts.

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Section: Discussionmentioning

confidence: 99%

Suzakumeasurement of Abell 2204's intracluster gas temperature profile out to 1800 kpc

Reiprich

Hudson

Zhang

et al. 2009

A&A

105

102

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“…It can be seen that there is some energy dependence in the difference, hence scaling the spectrum by the total counts may not be enough. It is known that the cosmic X-ray background which is the main contributor to the LAXPC background, has spatial fluctuation of about 7% (1σ) (Revnivtsev et al 2003) in the 2-10 keV band. These fluctuations cannot be modelled and set the flux limit below which faint sources may not be observable.…”

Section: The Detector Backgroundmentioning

confidence: 99%

Calibration of the Large Area X-Ray Proportional Counter (LAXPC) Instrument on board AstroSat

Antia

Yadav

Agrawal

et al. 2017

ApJS

194

120

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We present the calibration and background model for the Large Area X-ray Proportional Counter (LAXPC) detectors on-board AstroSat. LAXPC instrument has three nominally identical detectors to achieve large collecting area. These detectors are independent of each other and in the event analysis mode, they record the arrival time and energy of each photon that is detected. The detectors have a time-resolution of 10 µs and a dead-time of about 42 µs. This makes LAXPC ideal for timing studies. The energy resolution and peak channel to energy mapping were obtained from calibration on ground using radioactive sources coupled with GEANT4 simulations of the detectors. The response matrix was further refined from observations of the Crab after launch. At around 20 keV the energy resolution of detector is 10-15%, while the combined effective area of the 3 detectors is about 6000 cm 2 .

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“…A number of models have been developed to reconstruct the spectrum of the X-ray background (Comastri et al 1995;Gilli et al 2007;Treister et al 2009;Ballantyne et al 2011;Akylas et al 2012;Ueda et al 2014). All these models require a substantial number of Compton-thick AGN to reproduce the peak of the spectrum between 20 and 30 keV (Marshall et al 1980a;Gruber et al 1999;Revnivtsev et al 2003;Frontera et al 2007;Ajello et al 2008;Moretti et al 2009;Türler et al 2010). However, the exact number is still unconstrained with the various models predicting a fraction of Compton-thick AGN between 10 and 35% of the total AGN population.…”

Section: Introductionmentioning

confidence: 99%

Compton-thick AGN in the 70-monthSwift-BAT All-Sky Hard X-ray Survey: A Bayesian approach

Akylas

Georgantopoulos

Ranalli

et al. 2016

A&A

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The 70-month Swift/BAT catalogue provides a sensitive view of the extragalactic X-ray sky at hard energies (>10 keV) containing about 800 active galactic nuclei (AGN). We explore its content in heavily obscured, Compton-thick AGN by combining the BAT (14-195 keV) with the lower energy XRT (0.3-10 keV) data. We apply a Bayesian methodology using Markov chains to estimate the exact probability distribution of the column density for each source. We find 53 possible Compton-thick sources (probability range 3 -100%) translating to a ∼7% fraction of the AGN in our sample. We derive the first parametric luminosity function of Compton-thick AGN. The unabsorbed luminosity function can be represented by a double power law with a break at L ∼ 2 × 10 42 ergs s −1 in the 20-40 keV band. The Compton-thick AGN contribute ∼17% of the total AGN emissivity. We derive an accurate Compton-thick number count distribution taking into account the exact probability of a source being Compton-thick and the flux uncertainties. This number count distribution is critical for the calibration of the X-ray background synthesis models, i.e. for constraining the intrinsic fraction of Compton-thick AGN. We find that the number counts distribution in the 14-195 keV band agrees well with our models which adopt a low intrinsic fraction of Compton-thick AGN (∼ 12%) among the total AGN population and a reflected emission of ∼ 5%. In the extreme case of zero reflection, the number counts can be modelled with a fraction of at most 30% Compton-thick AGN of the total AGN population and no reflection. Moreover, we compare our X-ray background synthesis models with the number counts in the softer 2-10 keV band. This band is more sensitive to the reflected component and thus helps us to break the degeneracy between the fraction of Compton-thick AGN and the reflection emission. The number counts in the 2-10 keV band are well above the models which assume a 30% Compton-thick AGN fraction and zero reflection, while they are in better agreement with models assuming 12% Compton-thick fraction and 5% reflection. The only viable alternative for models invoking a high number of Compton-thick AGN is to assume evolution in their number with redshift. For example, in the zero reflection model the intrinsic fraction of Compton-thick AGN should rise from 30% at redshift z∼ 0 to about 50% at a redshift of z=1.1.

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The spectrum of the cosmic X-ray background observed by RTXE/PCA

Cited by 115 publications

References 32 publications

Suzakumeasurement of Abell 2204's intracluster gas temperature profile out to 1800 kpc

Suzakumeasurement of Abell 2204's intracluster gas temperature profile out to 1800 kpc

Calibration of the Large Area X-Ray Proportional Counter (LAXPC) Instrument on board AstroSat

Compton-thick AGN in the 70-monthSwift-BAT All-Sky Hard X-ray Survey: A Bayesian approach

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