arXiv subjects

Rashid Sunyaev

Publications and source records attributed to Rashid Sunyaev.

At least 55 records · Page 3Linked to original sources

arXiv2019

A High-resolution SZ View of the Warm-Hot Universe

The Sunyaev-Zeldovich (SZ) effect was first predicted nearly five decades ago, but has only recently become a mature tool for performing high resolution studies of the warm and hot ionized gas in and between galaxies, groups, and clusters. Galaxy groups and clusters are powerful probes of cosmology, and they also serve as hosts for roughly half of the galaxies in the Universe. In this white paper, we outline the advances in our understanding of thermodynamic and kinematic properties of the warm-hot universe that can come in the next decade through spatially and spectrally resolved measurements of the SZ effects. Many of these advances will be enabled through new/upcoming millimeter/submillimeter (mm/submm) instrumentation on existing facilities, but truly transformative advances will require construction of new facilities with larger fields of view and broad spectral coverage of the mm/submm bands.

astro-ph.CO↗

arXiv2018

FUV line emission, gas kinematics, and discovery of [Fe XXI] $λ$1354.1 in the sightline towards a filament in M87

We present new HST-COS G130M spectroscopy for a sightline toward a filament projected 1.9 kpc from the nucleus of M87. The combination of the sensitivity of COS and the proximity of M87 allows us to study the structure of this filament in unparalleled detail. We propose that the filament is composed of many cold clumps, each surrounded by an FUV-emitting boundary layer, with the filament having a radius $r_c \sim 10$ pc and the clumps filling the cylinder with a low volume filling factor. The observed velocity dispersion in emission lines from the filament results from the random motions of these clumps within the filament. We measure fluxes and kinematics for emission lines of Ly$α$, C II $λ$1335, and N V $\lambda1238$. We associate these three lines, as well as archival measurements of H$α$, C IV $λ$1549, and He II $λ$1640, with a multitemperature boundary layer around clumps which are moving with supersonic random motions in the filament. This boundary layer is a significant coolant of the hot gas. We show that the [C II] $λ$158$μ$m flux observed by Herschel-PACS from this region implies the existence of a massive cold ($T \sim 10^3$ K) component in the filament which contains significantly more mass than the FUV-emitting boundary layer. We also detect [Fe XXI] $λ$1354 in emission at $4-5σ$. This line is emitted from 1 keV ($T \approx 10^7$ K) plasma, and we use it to measure the bulk radial velocity and velocity dispersion of the plasma at this temperature. In contrast to the intermediate-temperature FUV lines, [\ion{Fe}{xxi}] is blueshifted relative to M87 and matches the bulk velocity of a nearby filament to the south. We hypothesize that this line arises from the approaching face of the radio bubble expanding through this sightline, while the filament lies on the receding side of the bubble. (abstract is abridged)

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arXiv2018

Probing large-scale structure with large samples of X-ray selected AGN: I Baryonic acoustic oscillations

We investigate the potential of large X-ray-selected AGN samples for detecting baryonic acoustic oscillations (BAO). Though AGN selection in X-ray band is very clean and efficient, it does not provide redshift information, and thus needs to be complemented with an optical follow-up. The main focus of this study is (i) to find the requirements needed for the quality of the optical follow-up and (ii) to formulate the optimal strategy of the X-ray survey, in order to detect the BAO. We demonstrate that redshift accuracy of $σ_0=10^{-2}$ at $z=1$ and the catastrophic failure rate of $f_{\rm fail}\lesssim 30\%$ are sufficient for a reliable detection of BAO in future X-ray surveys. Spectroscopic quality redshifts ($σ_0=10^{-3}$ and $f_{\rm fail}\sim 0$) will boost the confidence level of the BAO detection by a factor of $\sim 2$. For meaningful detection of BAO, X-ray surveys of moderate depth of $F_{\rm lim}\sim {\rm few~} 10^{-15}$ erg/s/cm$^2$ covering sky area from a few hundred to $\sim$ten thousand square degrees are required. The optimal strategy for the BAO detection does not necessarily require full sky coverage. For example, in a 1000-day long survey by an eROSITA type telescope, an optimal strategy would be to survey a sky area of $\sim 9000$ deg$^2$, yielding a $\sim 16σ$ BAO detection. A similar detection will be achieved by ATHENA+ or WFXT class telescopes in a survey with a duration of 100 days, covering a similar sky area. XMM-Newton can achieve a marginal BAO detection in a 100-day survey covering $\sim 400$ deg$^2$. These surveys would demand a moderate-to-high cost in terms the optical follow-ups, requiring determination of redshifts of $\sim 10^5$ (XMM-Newton) to $\sim 3\times 10^6$ objects (eROSITA, ATHENA+, and WFXT) in these sky areas.

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arXiv2017

Studying the ICM in clusters of galaxies via surface brightness fluctuations of the cosmic X-ray background

We study the surface brightness fluctuations of the cosmic X-ray background (CXB) using Chandra data of XBOOTES. After masking out resolved sources we compute the power spectrum of fluctuations of the unresolved CXB for angular scales from ~2 arcsec to ~3 deg. The non-trivial large-scale structure (LSS) signal dominates over the shot-noise of unresolved point sources at all scales above ~1 arcmin and is produced mainly by the intracluster medium (ICM) of unresolved clusters and groups of galaxies, as shown in our previous publication. The shot-noise-subtracted power spectrum of CXB fluctuations has a power-law shape with the slope of $Γ= 0.96 \pm 0.06$. Its energy spectrum is well described by the redshifted emission spectrum of optically-thin plasma with the best-fit temperature of $T \approx 1.3$ keV and the best-fit redshift of $z \approx 0.40$. They are in good agreement with theoretical expectations based on the X-ray luminosity function and scaling relations of clusters. From these values we estimate the typical mass and luminosity of the objects responsible for CXB fluctuations, $M_{500} \sim 10^{13.6}\,{\rm M}_{\odot}/h$ and $L_{0.5-2.0\,{\rm keV}} \sim 10^{42.5}$ erg/s. On the other hand, the flux-weighted mean temperature and redshift of resolved clusters are $T \approx 2.4$ keV and $z \approx 0.23$, confirming that fluctuations of unresolved CXB are caused by cooler (i.e. less massive) and more distant clusters, as expected. We show that the power spectrum shape is sensitive to the ICM structure all the way to the outskirts, out to $\sim{\rm few}\times R_{500}$. We also look for possible contribution of the warm-hot intergalactic medium (WHIM) to the observed CXB fluctuations. Our results underline the significant diagnostics potential of the CXB fluctuation analysis in studying the ICM structure in clusters.

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arXiv2017

New hard X-ray sources discovered in the ongoing INTEGRAL Galactic Plane survey after 14 years of observations

The International Gamma-Ray Astrophysics Laboratory (INTEGRAL) continues to successfully work in orbit after its launch in 2002. The mission provides the deepest ever survey of hard X-ray sources throughout the Galaxy at energies above 20 keV. We report on a catalogue of new hard X-ray source candidates based on the latest sky maps comprising 14 years of data acquired with the IBIS telescope onboard INTEGRAL in the Galactic Plane (|b|<17.5 deg). The current catalogue includes in total 72 hard X-ray sources detected at S/N>4.7 sigma and not known to previous INTEGRAL surveys. Among them, 31 objects have also been detected in the on-going all-sky survey by the BAT telescope of the Swift observatory. For 26 sources on the list, we suggest possible identifications: 21 active galactic nuclei, two cataclysmic variables, two isolated pulsars or pulsar wind nebulae, and one supernova remnant; 46 sources from the catalogue remain unclassified.

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arXiv2016

Can AGN and galaxy clusters explain the surface brightness fluctuations of the cosmic X-ray background?

Fluctuations of the surface brightness of cosmic X-ray background (CXB) carry unique information about faint and low luminosity source populations, which is inaccessible for conventional large-scale structure (LSS) studies based on resolved sources. We used Chandra data of the XBOOTES field ($\sim9\,\mathrm{deg^2}$) to conduct the most accurate measurement to date of the power spectrum of fluctuations of the unresolved CXB on the angular scales of $\sim3\,$arcsec $-$ $\sim17\,$arcmin. We find that at sub-arcmin angular scales, the power spectrum is consistent with the AGN shot noise, without much need for any significant contribution from their one-halo term. This is consistent with the theoretical expectation that low-luminosity AGN reside alone in their dark matter halos. However, at larger angular scales we detect a significant LSS signal above the AGN shot noise. Its power spectrum, obtained after subtracting the AGN shot noise, follows a power law with the slope of $-0.8\pm0.1$ and its amplitude is much larger than what can be plausibly explained by the two-halo term of AGN. We demonstrate that the detected LSS signal is produced by unresolved clusters and groups of galaxies. For the flux limit of the XBOOTES survey, their flux-weighted mean redshift equals $\left \sim0.3$, and the mean temperature of their intracluster medium (ICM), $\left \approx 1.4$ keV, corresponds to the mass of $M_{500} \sim 10^{13.5}\,\mathrm{M}_\odot$. The power spectrum of CXB fluctuations carries information about the redshift distribution of these objects and the spatial structure of their ICM on the linear scales of up to $\sim$Mpc, i.e. of the order of the virial radius.

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arXiv2016

SZ effects in the Magneticum Pathfinder Simulation: Comparison with the Planck, SPT, and ACT results

We calculate the one-point probability density distribution functions (PDF) and the power spectra of the thermal and kinetic Sunyaev-Zeldovich (tSZ and kSZ) effects and the mean Compton Y parameter using the Magneticum Pathfinder simulations, state-of-the-art cosmological hydrodynamical simulations of a large cosmological volume of (896 Mpc/h)^3. These simulations follow in detail the thermal and chemical evolution of the intracluster medium as well as the evolution of super-massive black holes and their associated feedback processes. We construct full-sky maps of tSZ and kSZ from the light-cones out to z=0.17, and one realization of 8.8x8.8 degree wide, deep light-cone out to z=5.2. The local universe at z<0.027 is simulated by a constrained realisation. The tail of the one-point PDF of tSZ from the deep light-cone follows a power-law shape with an index of -3.2. Once convolved with the effective beam of Planck, it agrees with the PDF measured by Planck. The predicted tSZ power spectrum agrees with that of the Planck data at all multipoles up to l~1000, once the calculations are scaled to the Planck 2015 cosmological parameters with Ω_m=0.308 and σ_8=0.8149. Consistent with the results in the literature, however, we continue to find the tSZ power spectrum at l=3000 that is significantly larger than that estimated from the high-resolution ground-based data. The simulation predicts the mean fluctuating Compton Y value of =1.18x10^{-6} for Ω_m=0.272 and σ_8=0.809. Nearly half (~ 5x10^{-7}) of the signal comes from halos below a virial mass of 10^{13}M_\odot/h. Scaling this to the Planck 2015 parameters, we find =1.57x10^{-6}. The PDF and the power spectrum of kSZ from our simulation agree broadly with the previous work.

astro-ph.CO↗

arXiv2016

Searching for FUV line emission from $10^7$ K gas in massive elliptical galaxies and galaxy clusters as a tracer of turbulent velocities

Non-thermal pressure from turbulence and bulk flows is a fundamental ingredient in hot gaseous halos, and in the intracluster medium it will be measured through emission line kinematics with calorimeters on future X-ray spacecraft. In this paper we present a complementary method for measuring these effects, using forbidden FUV emission lines of highly ionized Iron which trace $10^7$ K gas. The brightest of these is [Fe XXI] $λ$1354.1. We search for these lines in archival HST-COS spectra from the well-known elliptical galaxies M87 and NGC4696, which harbor large reservoirs of $10^7$ K gas. We report a 2.2$σ$ feature which we attribute to [Fe XXI] from a filament in M87, and positive residuals in the nuclei of M87 and NGC4696, for which the 90\% upper limits on the line flux are close to the predicted fluxes based on X-ray observations. In a newer reduction of the data from the Hubble Spectroscopic Legacy Archive, these limits become tighter and the [Fe XXI] feature reaches a formal significance of 5.3$σ$, neglecting uncertainty in fitting the continuum. Using our constraints, we perform emission measure analysis, constraining the characteristic path length and column density of the $\sim10^7$ K gas. We also examine several sightlines towards filaments or cooling flows in other galaxy clusters, for which the fraction of gas at $10^7$ K is unknown, and place upper limits on its emission measure in each case. A medium-resolution HST-COS observation of the M87 filament for $\sim$10 orbits would confirm our detection of [Fe XXI] and measure its width.

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arXiv2015

Probing the clumping structure of Giant Molecular Clouds through the spectrum, polarisation and morphology of X-ray Reflection Nebulae

We suggest a method for probing global properties of clump populations in Giant Molecular Clouds (GMCs) in the case where these act as X-ray reflection nebulae (XRNe), based on the study of the clumping's overall effect on the reflected X-ray signal, in particular on the Fe K-alpha line's shoulder. We consider the particular case of Sgr B2, one of the brightest and most massive XRN in our Galaxy. We parametrise the gas distribution inside the cloud using a simple clumping model, with the slope of the clump mass function (alpha), the minimum clump mass (m_{min}), the fraction of the cloud's mass contained in clumps (f_{DGMF}), and the mass-size relation of individual clumps as free parameters, and investigate how these affect the reflected X-ray spectrum. In the case of very dense clumps, similar to those presently observed in Sgr B2, these occupy a small volume of the cloud and present a small projected area to the incoming X-ray radiation. We find that these contribute negligibly to the scattered X-rays. Clump populations with volume filling factors of > 10^{-3}, do leave observational signatures, that are sensitive to the clump model parameters, in the reflected spectrum and polarisation. Future high-resolution X-ray observations could therefore complement the traditional optical and radio observations of these GMCs, and prove to be a powerful probe in the study of their internal structure. Finally, clumps in GMCs should be visible both as bright spots and regions of heavy absorption in high resolution X-ray observations. We therefore further study the time-evolution of the X-ray morphology, under illumination by a transient source, as a probe of the 3d distribution and column density of individual clumps by future X-ray observatories.

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arXiv2015

Preheating of the Universe by cosmic rays from primordial supernovae at the beginning of cosmic reionization

The 21-cm signal from the cosmic reionization epoch can shed light on the history of heating of the primordial intergalactic medium (IGM) at z~30-10. It has been suggested that X-rays from the first accreting black holes could significantly heat the Universe at these early epochs. Here we propose another IGM heating mechanism associated with the first stars. As known from previous work, the remnants of powerful supernovae (SNe) ending the lives of massive Population III stars could readily expand out of their host dark matter minihalos into the surrounding IGM, aided by the preceeding photoevaporation of the halo's gas by the UV radiation from the progenitor star. We argue that during the evolution of such a remnant a significant fraction of the SN kinetic energy can be put into low-energy (E<30 MeV) cosmic rays that will eventually escape into the IGM. These subrelativistic cosmic rays could propagate through the Universe and heat the IGM by ~10-100 K by z~15, before more powerful reionization/heating mechanisms associated with the first galaxies and quasars came into play. Future 21-cm observations could thus constrain the energetics of the first supernovae and provide information on the magnetic fields in the primordial IGM.

astro-ph.CO↗

arXiv2015

Constraints on $μ$-distortion fluctuations and primordial non-Gaussianity from Planck data

We use the Planck HFI channel maps to make an all sky map of $μ$-distortion fluctuations. Our $μ$-type distortion map is dominated by the $y$-type distortion contamination from the hot gas in the low redshift Universe and we can thus only place upper limits on the $μ$-type distortion fluctuations. For the amplitude of $μ$-type distortions on $10'$ scales we get the limit on root mean square (rms) value $μ_{rms}^{10'}< 6.4\times 10^{-6}$, a limit 14 times stronger than the COBE-FIRAS ($95\%$ confidence) limit on the mean of $< μ> <90\times 10^{-6}$. Using our maps we also place strong upper limits on the auto angular power spectrum of $μ$, $C_{\ell}^{μμ}$ and the cross angular power spectrum of $μ$ with the CMB temperature anisotropies, $C_{\ell}^{μT}$. The strongest observational limits are on the largest scales, $\ell(\ell+1)/(2π)C_{\ell}^{μμ}|_{\ell=2-26}<(2.3\pm 1.0)\times 10^{-12}$ and $\ell(\ell+1)/(2π)C_{\ell}^{μT}|_{\ell=2-26}<(2.6\pm 2.6)\times 10^{-12}~{K}$. Our observational limits can be used to constrain new physics which can create spatially varying energy release in the early Universe between redshifts $5\times 10^4\lesssim z\lesssim 2\times 10^6$. We specifically apply our observational results to constrain the primordial non-Gaussianity of the local type, when the source of $μ$-distortion is Silk damping, for very squeezed configurations with the wavenumber for the short wavelength mode $46 \lesssim k_{S} \lesssim 10^4 ~{Mpc^{-1}}$ and for the long wavelength mode $k_{L}\approx 10^{-3} ~{Mpc^{-1}}$. Our limits on the primordial non-Gaussianity parameters are $f_{NL}<10^5, τ_{NL}<1.4\times 10^{11}$ for $k_{S}/k_{L}\approx 5\times 10^4- 10^7$. We give a new derivation of the evolution of the $μ$-distortion fluctuations. We also introduce mixing of Bose-Einstein spectra and $y^{BE}$-type distortions.

astro-ph.CO↗

arXiv2015

Limits on the fluctuating part of $y$-type distortion monopole from Planck and SPT results

We use the published Planck and SPT cluster catalogs and recently published $y$-distortion maps to put strong observational limits on the contribution of the fluctuating part of the $y$-type distortions to the $y$-distortion monopole. Our bounds are $5.4\times 10^{-8} < \langle y\rangle < 2.2\times 10^{-6}$. Our upper bound is a factor of 6.8 stronger than the currently best upper $95\%$ confidence limit from COBE-FIRAS of $\langle y\rangle <15\times 10^{-6}$. In the standard cosmology, large scale structure is the only source of such distortions and our limits therefore constrain the baryonic physics involved in the formation of the large scale structure. Our lower limit, from the detected clusters in the Planck and SPT catalogs, also implies that a Pixie-like experiment should detect the $y$-distortion monopole at $>27$-$σ$. The biggest sources of uncertainty in our upper limit are the monopole offsets between different HFI channel maps that we estimate to be $<10^{-6}$.

astro-ph.CO↗

arXiv2014

A thin diffuse component of the Galactic Ridge X-ray emission and heating of the interstellar medium contributed by the radiation of Galactic X-ray binaries

We predict a thin (scale height $\sim$ 80 pc) diffuse component of the Galactic Ridge X-ray emission (GRXE) arising from the scattering of the radiation of bright X-ray binaries (XBs) by the interstellar medium (ISM). The morphology of this scattered component is expected to trace the clumpy molecular and HI clouds. We calculate this contribution to the GRXE from known Galactic XBs assuming that they are all persistent. The known XBs sample is incomplete, however, because it is flux limited and spans the lifetime of X-ray astronomy ($\sim 50$ years). We therefore also use a simulated sample of sources, to estimate the diffuse emission we should expect in an optimistic case assuming that the X-ray luminosity of our Galaxy is on average similar to that of other galaxies. In the calculations we also take into account the enhancement of the total scattering cross-section due to coherence effects in the elastic scattering from multi-electron atoms and molecules. This scattered emission can be distinguished from the contribution of low X-ray luminosity stars by the presence of narrow fluorescent K-$α$ lines of Fe, Si, and other abundant elements present in the ISM and by directly resolving the contribution of low X-ray luminosity stars. We find that within $1^\circ$ latitude of the Galactic plane the scattered emission contributes on average $10-30\%$ of the GRXE flux in the case of known sources and over $50\%$ in the case of simulated sources. In the latter case, the scattered component is found to even dominate the stellar emission in certain parts of the Galactic plane. X-rays with energies $\gtrsim 1$ keV from XBs should also penetrate deep inside the HI and molecular clouds, where they are absorbed and heat the ISM. We find that this heating rate dominates the heating by cosmic rays (assuming a solar neighborhood energy density) in a considerable part of the Galaxy. [abridged]

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arXiv2013

Linking X-ray AGN with dark matter halos: a model compatible with AGN luminosity function and large-scale clustering properties

Our goal is to find a minimalistic model that describes the luminosity function and large-scale clustering bias of the X-ray-selected AGN in the general framework of the concordance LCDM model. We assume that a simple population-averaged scaling relation between the AGN X-ray luminosity L_X and the host dark matter halo mass M_h exists. With such a relation, the AGN X-ray luminosity function can be computed from the halo mass function. Using the concordance LCDM halo mass function for the latter, we obtain the M_h-L_X relation required to match the redshift-dependent AGN X-ray luminosity function known from X-ray observations. We find that with a simple power-law-scaling M_h \propto L_X^Γ(z), our model can successfully reproduce the observed X-ray luminosity function. Furthermore, we automatically obtain predictions for the large-scale AGN clustering amplitudes and their dependence on the luminosity and redshift, which seem to be compatible with AGN clustering measurements. Our model also includes the redshift-dependent AGN duty cycle which peaks at the redshift z ~ 1, and its peak value is consistent with unity, suggesting that on average there is no more than one AGN per dark matter halo. For a typical X-ray-selected AGN at z ~ 1, our best-fit M_h-L_X scaling implies low Eddington ratio L_X/L_Edd ~ 10^{-4}-10^{-3} (2-10 keV band, no bolometric correction applied) and correspondingly large mass growth e-folding times, suggesting that the typical X-ray AGN are dominantly fueled via relatively inefficient 'hot-halo' accretion mode.

astro-ph.CO↗

arXiv2013

SRG/eROSITA prospects for the detection of stellar tidal disruption flares

We discuss the potential of the eROSITA telescope on board the Spectrum-Roentgen-Gamma (SRG) observatory to detect stellar tidal disruption events (TDE) during its 4-year all-sky survey. These events are expected to reveal themselves as luminous flares of UV/soft X-ray emission associated with the centres of previously non-active galaxies and fading by few orders of magnitude on time-scales of several months to years. Given that eROSITA will complete an all-sky survey every 6 months and a total of 8 such scans will be performed over the course of the mission, we propose to distinguish TDEs from other X-ray transients using two criteria: I) large (more than a factor of 10) X-ray variation between two subsequent 6-month scans and ii) soft X-ray spectrum. The expected number of TDE candidates is $\sim 10^3$ per scan (with most of the events being new discoveries in a given scan), so that a total of several thousand TDE candidates could be found during the 4-year survey. The actual number may significantly differ from this estimate, since it is based on just a few TDEs observed so far. The eROSITA all-sky survey is expected to be nearly equally sensitive to TDEs occurring near supermassive black holes (SMBH) of mass between $\sim 10^6$ and $\sim 10^7 M_\odot$ and will thus provide a unique census of quiescent SMBHs and associated nuclear stellar cusps in the local Universe ($z\lesssim 0.15$). Information on TDE candidates will be available within a day after their detection and localization by eROSITA, making possible follow-up observations that may reveal peculiar types of TDEs.

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arXiv2013

AGN and QSOs in the eROSITA All-Sky Survey -- Part II: The large-scale structure

The four-year X-ray all-sky survey (eRASS) of the eROSITA telescope aboard the Spektrum-Roentgen-Gamma satellite will detect ~3 million active galactic nuclei (AGN) with a median redshift of z~1 and a typical luminosity of L_(0.5-2.0 keV) ~ 10^(44) erg/s. We show that this unprecedented AGN sample, complemented with redshift information, will supply us with outstanding opportunities for large-scale structure research. For the first time, detailed redshift- and luminosity-resolved studies of the bias factor for X-ray selected AGN will become possible. The eRASS AGN sample will not only improve the redshift- and luminosity-resolution of these studies, but will also expand their luminosity range beyond L_(0.5-2.0 keV) ~ 10^(44) erg/s, thus enabling a direct comparison of the clustering properties of luminous X-ray AGN and optical quasars. These studies will dramatically improve our understanding of the AGN environment, triggering mechanisms, the growth of supermassive black holes and their co-evolution with dark matter halos. The eRASS AGN sample will become a powerful cosmological probe. It will enable detecting baryonic acoustic oscillations (BAOs) for the first time with X-ray selected AGN. With the data from the entire extragalactic sky, BAO will be detected at a >~10sigma confidence level in the full redshift range and with ~8sigma confidence in the 0.8 < z < 2.0 range, which is currently not covered by any existing BAO surveys. To exploit the full potential of the eRASS AGN sample, photometric and spectroscopic surveys of large areas and a sufficient depth will be needed.

astro-ph.CO↗

arXiv2013

AGN and QSOs in the eROSITA All-Sky Survey -- Part I: Statistical properties

Context. The main element of the observing program of the Spectrum-Roentgen-Gamma orbital observatory is a four-year all-sky survey, in the course of which the entire sky will be scanned eight times. Aims. We analyze the statistical properties of AGN and QSOs that are expected to be detected in the course of the eROSITA all-sky survey (eRASS). Methods. According to the currently planned survey strategy and based on the parameters of the Galactic and extragalactic X-ray background as well as on the results of the recent calculations of the eROSITA instrumental background, we computed a sensitivity map of the eRASS. Using the best available redshift-dependent AGN X-ray luminosity function (XLF), we computed various characteristics of the eRASS AGN sample, such as their luminosity- and redshift distributions, and the brightness distributions of their optical counterparts. Results. After four years of the survey, a sky-average sensitivity of ~1x10^(-14) erg/s/cm^2 will be achieved in the 0.5-2.0keV band. With this sensitivity, eROSITA is expected to detect ~3 million AGN on the extragalactic sky (|b|>10deg). The median redshift of the eRASS AGN will be z~1 with ~40% of the objects in the z=1-2 redshift range. About 10^4 - 10^5 AGN are predicted beyond redshift z=3 and about 2 000 - 30 000 AGN beyond redshift z=4, the exact numbers depend on the poorly known behavior of the AGN XLF in the high-redshift and luminosity regimes. Of the detected AGN, the brightest 10% will be detected with more than ~38 counts per PSF HEW, while the faintest 10% will have fewer than ~9 counts. The optical counterparts of ~95% of the AGN will be brighter than I_(AB)=22.5mag. The planned scanning strategy will allow one to search for transient events on a timescale of half a year and a few hours with a 0.5-2.0keV sensitivity of ~2x10^(-14) to ~2x10^(-13) erg/s/cm^2, respectively.

astro-ph.CO↗

arXiv2013

PRISM (Polarized Radiation Imaging and Spectroscopy Mission): A White Paper on the Ultimate Polarimetric Spectro-Imaging of the Microwave and Far-Infrared Sky

PRISM (Polarized Radiation Imaging and Spectroscopy Mission) was proposed to ESA in response to the Call for White Papers for the definition of the L2 and L3 Missions in the ESA Science Programme. PRISM would have two instruments: (1) an imager with a 3.5m mirror (cooled to 4K for high performance in the far-infrared---that is, in the Wien part of the CMB blackbody spectrum), and (2) an Fourier Transform Spectrometer (FTS) somewhat like the COBE FIRAS instrument but over three orders of magnitude more sensitive. Highlights of the new science (beyond the obvious target of B-modes from gravity waves generated during inflation) made possible by these two instruments working in tandem include: (1) the ultimate galaxy cluster survey gathering 10e6 clusters extending to large redshift and measuring their peculiar velocities and temperatures (through the kSZ effect and relativistic corrections to the classic y-distortion spectrum, respectively) (2) a detailed investigation into the nature of the cosmic infrared background (CIB) consisting of at present unresolved dusty high-z galaxies, where most of the star formation in the universe took place, (3) searching for distortions from the perfect CMB blackbody spectrum, which will probe a large number of otherwise inaccessible effects (e.g., energy release through decaying dark matter, the primordial power spectrum on very small scales where measurements today are impossible due to erasure from Silk damping and contamination from non-linear cascading of power from larger length scales). These are but a few of the highlights of the new science that will be made possible with PRISM.

astro-ph.CO↗