- ID:
- ivo://CDS.VizieR/J/ApJ/897/177
- Title:
- 142 high-redshift blazars at the cosmic dawn
- Short Name:
- J/ApJ/897/177
- Date:
- 11 Mar 2022
- Publisher:
- CDS
- Description:
- The uncharted territory of the high-redshift (z>~3) universe holds the key to understanding the evolution of quasars. In an attempt to identify the most extreme members of the quasar population, that is, blazars, we have carried out a multiwavelength study of a large sample of radio-loud quasars beyond z=3. Our sample consists of nine {gamma}-ray-detected blazars and 133 candidate blazars selected based on the flatness of their soft X-ray spectra (0.3-10keV photon index <~1.75), including 15 with Nuclear Spectroscopic Telescope Array (NuSTAR) observations. The application of the likelihood profile stacking technique reveals that the high-redshift blazars are faint {gamma}-ray emitters with steep spectra. The high-redshift blazars host massive black holes (<logM_BH,M{odot}_>>9) and luminous accretion disks (<L_disk_>>10^46^erg/s). Their broadband spectral energy distributions are found to be dominated by high-energy radiation, indicating their jets are among the most luminous ones. Focusing on the sources exhibiting resolved X-ray jets (as observed with the Chandra satellite), we find the bulk Lorentz factor to be larger with respect to other z>3 blazars, indicating faster moving jets. We conclude that the presented list of high-redshift blazars may act as a reservoir for follow-up observations, such as with NuSTAR, to understand the evolution of relativistic jets at the dawn of the universe.
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142. 3HSP blazars catalog
- ID:
- ivo://CDS.VizieR/J/A+A/632/A77
- Title:
- 3HSP blazars catalog
- Short Name:
- J/A+A/632/A77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-synchrotron peaked blazars (HSPs or HBLs) play a central role in very high-energy (VHE) {gamma}-ray astronomy, and likely in neutrino astronomy. Currently, the largest compilation of HSP blazars, the 2WHSP sample, includes 1691 sources, but it is not complete in the radio or in the X-ray band. In order to provide a larger and more accurate set of HSP blazars that is useful for future statistical studies and to plan for VHE/TeV observations, we present the 3HSP catalogue, the largest sample of extreme and high-synchrotron peaked (EHSP; HSP) blazars and blazar candidates. We implemented several ways to improve the size and the completeness of the 2WHSP catalogue and reduced the selection biases to be taken into consideration in population studies. By discarding the IR constraint and relaxing the radio-IR and IR-X-ray slope criteria, we were able to select more sources with peak close to the 10^15^Hz threshold and objects where the host galaxy dominates the flux. The selection of extra sources now commences with a crossmatching between radio and X-ray surveys, applying a simple flux ratio cut. We also considered Fermi-LAT catalogues to find reasonable HSP-candidates that are detected in the {gamma}-ray band but are not included in X-ray or radio source catalogues. The new method, and the use of newly available multi-frequency data, allowed us to add 395 sources to the sample, to remove 73 2WHSP sources that were previously agged as uncertain and could not be confirmed as genuine HSP blazars, and to update parameters obtained by fitting the synchrotron component. The 3HSP catalogue includes 2013 sources, 88% of which with a redshift estimation, a much higher percentage than in any other list of HSP blazars. All new {gamma}-ray detections are described in the First and Second Brazil ICRANet {gamma}-ray blazar catalogues (1BIGB & 2BIGB) also taking into account the 4FGL list of {gamma}-ray sources published by the Fermi Large Area Telescope (Fermi-LAT) team. Moreover, the cross-matching between the 2WHSP, 2FHL HSP, and IceCube neutrino positions suggests that HSPs are likely counterparts of neutrino events, which implies the 3HSP catalogue is also useful in that respect. The 3HSP catalogue shows improved completeness compared to its predecessors, the 1WHSP and 2WHSP catalogues, and follows the track of their increasing relevance for VHE astronomy.
- ID:
- ivo://CDS.VizieR/J/ApJS/256/40
- Title:
- HST imaging survey of low-z Swift-BAT AGNs
- Short Name:
- J/ApJS/256/40
- Date:
- 03 Mar 2022 00:28:07
- Publisher:
- CDS
- Description:
- We present initial results from a Hubble Space Telescope snapshot imaging survey of the host galaxies of Swift-BAT active galactic nuclei (AGN) at z<0.1. The hard X-ray selection makes this sample relatively unbiased in terms of obscuration, compared to optical AGN selection methods. The high-resolution images of 154 target AGN enable us to investigate the detailed photometric structure of the host galaxies, such as the Hubble type and merging features. We find 48% and 44% of the sample to be hosted by early-type and late-type galaxies, respectively. The host galaxies of the remaining 8% of the sample are classified as peculiar galaxies because they are heavily disturbed. Only a minor fraction of host galaxies (18%-25%) exhibit merging features (e.g., tidal tails, shells, or major disturbance). The merging fraction increases strongly as a function of bolometric AGN luminosity, revealing that merging plays an important role in triggering luminous AGN in this sample. However, the merging fraction is weakly correlated with the Eddington ratio, suggesting that merging does not necessarily lead to an enhanced Eddington ratio. Type 1 and Type 2 AGN are almost indistinguishable in terms of their Hubble type distribution and merging fraction. However, the merging fraction of Type 2 AGN peaks at a lower bolometric luminosity compared with those of Type 1 AGN. This result may imply that the triggering mechanism and evolutionary stages of Type 1 and Type 2 AGN are not identical.
- ID:
- ivo://CDS.VizieR/J/ApJS/254/26
- Title:
- Identifying 3FHL. V. CTIO-COSMOS spectra
- Short Name:
- J/ApJS/254/26
- Date:
- 19 Jan 2022 00:35:09
- Publisher:
- CDS
- Description:
- As a follow-up to the optical spectroscopic campaign aimed at achieving completeness in the Third Catalog of Hard Fermi-LAT Sources (3FHL), we present here the results of a sample of 28 blazars of an uncertain type observed using the 4m telescope at Cerro Tololo Inter-American Observatory in Chile. Out of these 28 sources, we find that 25 are BL Lacertae objects (BL Lacs) and 3 are flat-spectrum radio quasars (FSRQs). We measure redshifts or lower limits for 16 of these blazars, and it is observed that the 12 remaining blazars have featureless optical spectra. These results are part of a more extended optical spectroscopy follow-up campaign for 3FHL blazars, where, until now, 51 blazars of an uncertain type have been classified into BL Lac and FSRQ categories. Furthermore, this campaign has resulted in redshift measurements and lower limits for 15 of these sources. Our results contribute toward attaining a complete sample of blazars above 10 GeV, which then will be crucial in extending our knowledge on blazar emission mechanisms and the extragalactic background light.
- ID:
- ivo://CDS.VizieR/J/A+A/562/A70
- Title:
- Imaging GRB 980425 in millimetic and submm
- Short Name:
- J/A+A/562/A70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Gamma-ray bursts (GRBs) have been proposed as a tool to study star formation in the Universe, so it is crucial to investigate whether their host galaxies and immediate environments are in any way special compared with other star-forming galaxies. Here we present spatially resolved maps of dust emission of the host galaxy of the closest known GRB 980425 at z=0.0085 using our new high-resolution observations from Herschel, APEX, ALMA and ATCA. We modeled the spectral energy distributions of the host and of the star-forming region displaying the Wolf-Rayet signatures in the spectrum (WR region), located 800pc away from the GRB position. The host is characterised by low dust content and high fraction of UV-visible star-formation, similar to other dwarf galaxies. Such galaxies are abundant in the local universe, so it is not surprising to find a GRB in one of them, assuming the correspondence between the GRB rate and star-formation. The WR region contributes substantially to the host emission at the far-infrared, millimeter and radio wavelengths and we propose this to be a consequence of its high gas density. If dense environments are also found close to the positions of other GRBs, then the ISM density should also be considered as an important factor influencing whether a given stellar population can produce a GRB, in a similar way as metallicity.
- ID:
- ivo://CDS.VizieR/J/A+A/475/775
- Title:
- INTEGRAL all-sky survey of hard X-ray sources
- Short Name:
- J/A+A/475/775
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of an all-sky hard X-ray survey based on almost four years of observations with the IBIS telescope onboard the INTEGRAL observatory. The dead time-corrected exposure of the survey is about 33Ms. Approximately 12% and 80% of the sky has been covered to limiting fluxes lower than 1 and 5mCrab, respectively. Our catalog of detected sources includes 403 objects, 316 of which exceed a 5{sigma} detection threshold on the time-averaged map of the sky, and the rest were detected in various subsamples of exposures.
- ID:
- ivo://CDS.VizieR/J/A+A/523/A61
- Title:
- INTEGRAL all-sky survey of hard X-ray sources
- Short Name:
- J/A+A/523/A61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper is the second in a series devoted to the hard X-ray (17-60keV) whole sky survey performed by the INTEGRAL observatory over seven years. Here we present a catalog of detected sources that includes 521 objects, 449 of which exceed a 5{sigma} detection threshold on the time-averaged map of the sky, and 53 were detected in various subsamples of exposures. Among the identified sources with known and suspected nature, 262 are Galactic (101 low-mass X-ray binaries, 94 high-mass X-ray binaries, 37 cataclysmic variables, and 30 of other types) and 221 are extragalactic, including 217 active galactic nuclei (AGNs) and 4 galaxy clusters. The extragalactic (|b|>5deg) and Galactic (|b|<5deg) persistently detected source samples have high identification completeness (respectively ~96% and ~93%) and are valuable for population studies.
- ID:
- ivo://CDS.VizieR/J/MNRAS/426/1750
- Title:
- INTEGRAL/IBIS AGN catalogue
- Short Name:
- J/MNRAS/426/1750
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this work we present the most comprehensive INTEGRAL active galactic nucleus (AGN) sample. It lists 272 AGN for which we have secure optical identifications, precise optical spectroscopy and measured redshift values plus X-ray spectral information, i.e. 2-10 and 20-100keV fluxes plus column density. Here we mainly use this sample to study the absorption properties of active galaxies, to probe new AGN classes and to test the AGN unification scheme.
- ID:
- ivo://CDS.VizieR/J/ApJ/649/L9
- Title:
- INTEGRAL IBIS census of the sky beyond 100keV
- Short Name:
- J/ApJ/649/L9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the first census of INTEGRAL IBIS detections (>~4{sigma} significance) above 100keV based on the Core Program and public open-time observations up to 2005 April. There are 49 sources detected in the 100-150keV band, of which 14 are also seen in the 150-300keV range. The low-energy sample is dominated by X-ray binary systems of both low and high mass but also includes 10 active galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/545/A27
- Title:
- INTEGRAL/IBIS 9-year Galactic hard X-ray survey
- Short Name:
- J/A+A/545/A27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present sky images, sensitivity maps, and catalogs of detected sources in the three energy bands 17-60, 17-35, and 35-80keV in the Galactic plane at |b|<17.5 degrees. The total number of sources in the reference 17-60keV band includes 402 objects exceeding a 4.7{sigma} detection threshold on the nine-year time-averaged map. Among the identified sources with known and tentatively identified natures, 253 are Galactic objects (108 low-mass X-ray binaries, 82 high-mass X-ray binaries, 36 cataclysmic variables, and 27 are of other types), and 115 are extragalactic objects, including 112 active galactic nuclei (AGNs) and 3 galaxy clusters. The sample of Galactic sources with S/N>4.7 sigma has an identification completeness of ~92%, which is valuable for population studies. Since the survey is based on the nine-year sky maps, it is optimized for persistent sources and may be biased against finding transients.
