Hard X-ray properties of radio-selected blazars

Abstract

Context. Hard X-ray properties of beamed AGN have been published in the 105-month Swift/BAT catalog, but there have not been any studies carried out so far on a well-defined, radio-selected sample of low-peaked blazars in the hard X-ray band. Aims. Using the statistically complete MOJAVE-1 sample, we aim to determine the hard X-ray properties of radio-selected blazars, including the enigmatic group of gamma-ray-faint blazars. Additionally, we aim to determine the contribution of radio-selected lowpeaked blazars to the diffuse CXB. Methods. We determined photon indices, fluxes, and luminosities in the range of 20 keV -100 keV of the X-ray spectra of blazars and other extragalactic jets from the MOJAVE-1 sample, derived from the 105-month Swift/BAT survey. We calculated log N-log S distributions and determined the luminosity functions.Results. The majority of the MOJAVE-1 blazars are found to be hard X-ray emitters albeit many at low count rates. The log Nlog S distribution for the hard X-ray emission of radio-selected blazars is clearly non-Euclidean, in contrast to the radio flux density distribution. Approximately 0.2% of the CXB in the 20 keV -100 keV band can be resolved into MOJAVE-1 blazars. Conclusions. The peculiar log N-log S distribution disparity might be attributed to different evolutionary paths in the X-ray and radio bands, as tested by luminosity-function modeling. X-ray variability can be ruled out as the dominant contributor. Low-peaked blazars constitute an intrinsically different source population in terms of CXB contribution compared to similar studies of X-ray-selected blazars. The hard X-ray flux and spectral index can serve as a good proxy for the gamma-ray detection probability of individual sources. Future observations combining deep X-ray survey, for example, with eROSITA, and targeted gamma-ray observations with CTA can benefit strongly from the tight connection between these high-energy bands for the different blazar sub-classes. 1 arXiv:2004.00477v1 [astro-ph.HE] 1 Apr 2020 M. Langejahn et al.: Hard X-ray properties of radio-selected blazars quasars (FSRQ), out of 1632 sources, including 114 unclassified AGN and an additional 129 unidentified sources. The recent 4FGL catalog of the gamma-ray all-sky survey from Fermi/LAT (The Fermi-LAT collaboration 2019) alone contains 1102 BL Lac type and 681 FSRQ type blazars out of a total of 2940 associated blazars and blazar candidates.In this work, we perform a detailed analysis of X-ray data from the most recent Swift/BAT survey maps for the radioselected MOJAVE-1 (Monitoring Of Jets in Active galactic nuclei with VLBA Experiments) beamed AGN sample. We report the hard X-ray characteristics in the 20 keV -100 keV band of this statistically complete extragalactic jet sample, which is mostly composed of blazars.This paper is structured as follows: Sect. 2 gives a short introduction to the MOJAVE program as well as the Swift mission and describes the object samples and data basis we used. The analysis, including the applied methods and assumptions...

The Impact of the CMB on the Evolution of high-z Blazars

“…4 the X-ray space density obtained from the integration of the XLF considering the effect of CMB (solid red line). The shaded areas show the expected evolutions assuming a different photon index (Γ in the range 1.5-1.6, the median values observed at energies 20-100 keV in a radio selected sample of blazars, Langejahn et al 2020) and a different distribution of the logA 0 parameter which can still well reproduce the observed C19 X/R ratios (p-value>0.7, see section 3). As it is clear from Fig.…”

The first hard X-ray spectral catalogue of Blazars observed by NuSTAR

“…However, Pal et al (2020) reported a strong soft X-ray excess in the X-ray spectrum of OJ287 using XMM-Newton observations. Furthermore, Langejahn et al (2020) showed that the Swift-BAT spectrum (20-100 keV) is well-described by a power-law with Γ = 1.31, using the 105months Swift-BAT survey. NuSTAR observed OJ287 twice during two major flare events detected by Swift (in 2017 and 2020): although the 3.0-10.0 keV X-ray flux was similar ( 3.5 × 10 −12 erg cm −2 s −1 ) during these observations, the photon index varied.…”