AGN and QSOs in the eROSITA All-Sky Survey

Abstract

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 active galactic nuclei (AGN) and quasars/quasi-stellar objects (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 about 1 × 10 −14 erg s −1 cm −2 will be achieved in the 0.5−2.0 keV band. With this sensitivity, eROSITA is expected to detect about 3 million AGN on the extragalactic sky (|b| > 10 • ). The median redshift of the eRASS AGN will be z ≈ 1 with approximately 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 2000−30 000 AGN beyond redshift z = 4, the exact numbers depend on the poorly known behavior of the AGN XLF in the high-redshift and high-luminosity regimes. Of the detected AGN, the brightest 10% will be detected with more than ≈38 counts per point-spread-function (half-energy width), while the faintest 10% will have fewer than ≈9 counts. The optical counterparts of approximately 95% of the AGN will be brighter than I AB = 22.5 mag. 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 0.5−2.0 keV sensitivity of ≈2 × 10 −14 to ≈2 × 10 −13 erg s −1 cm −2 , respectively.

AGNs and Their Host Galaxies in the Local Universe: Two Mass-independent Eddington Ratio Distribution Functions Characterize Black Hole Growth

“…At lower energies, the Chandra and XMMNewton coverage of SDSS Stripe 82 (Stripe 82X; flux limit ∼ 10 −15 erg s −1 cm −2 ; LaMassa et al 2013a,b) will be probing fainter luminosities than Swift-BAT. In the near future, eROSITA , and specifically the eROSITA all-sky survey (eRASS; flux limit ∼ 10 −14 erg s −1 cm −2 ), will be able to significantly increase the number of soft X-ray detected AGN (Kolodzig et al 2013). Compared to eRASS, ATHENA will be probing even fainter luminosities over a wider redshift range and area, in the far future (flux limit ∼ 10 −17 erg s −1 cm −2 ; Aird et al 2013b;Georgakakis et al 2013).…”

AGN and QSOs in the eROSITA All-Sky Survey

“…In our previous work (Kolodzig et al 2013), we have studied the statistical properties of the AGN sample of eRASS and will adopt these results here. In the current work, we focus on the AGN detected in the soft-energy band (0.5−2.0 keV) and on the extragalactic sky (|b| > 10…”

“…In the following calculations we assumed the four-year average sensitivity of 1.1 × 10 −14 erg s −1 cm −2 adopted in Kolodzig et al (2013 , Table 1). …”

Optical spectroscopy of candidates for quasars at 3 < z < 5.5 from the XMM-newton X-ray survey. A distant X-ray quasar at z = 5.08

“…Consequently, it will be possible to detect several new optically bright quasars at z > 5 with an X-ray luminosity higher than ∼ 10 45 erg/s in these fields. At the same time, the total number of quasars at z > 5 discovered by the eROSITA telescope near the ecliptic poles may turn out to be much greater (tens or even hundreds; Kolodzig et al 2013), but most of them will most likely be fainter than the SDSS sensitivity threshold. Deeper optical surveys, for example, PanSTARRS Hodapp et al (2004) and the sky surveys conducted by the Hyper Suprime-Cam (Miyazaki et al, 2012) at the 8-m Subaru telescope, will be required for their identification.…”