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- ID:
- ivo://CDS.VizieR/J/ApJ/867/131
- Title:
- Blazar candidates behind the Magellanic Clouds
- Short Name:
- J/ApJ/867/131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the identification of blazar candidates behind the Magellanic Clouds. The objects were selected from the Magellanic Quasars Survey (MQS), which targeted the entire Large Magellanic Cloud (LMC) and 70% of the Small Magellanic Cloud (SMC). Among the 758 MQS quasars and 898 of the unidentified (featureless spectra) objects, we identified a sample of 44 blazar candidates, including 27 flat-spectrum radio quasars and 17 BL Lacertae objects, respectively. All the blazar candidates from our sample were identified with respect to their radio, optical, and midinfrared properties. The newly selected blazar candidates possess the long-term, multicolor photometric data from the Optical Gravitational Lensing Experiment, multicolor midinfrared observations, and archival radio data for one frequency at least. In addition, for nine of them, the radio polarization data are available. With such data, these objects can be used to study the physics behind the blazar variability detected in the optical and midinfrared bands, as a tool to investigate magnetic field geometry of the LMC and SMC, and as an exemplary sample of point-like sources most likely detectable in the {gamma}-ray range with the newly emerging Cherenkov Telescope Array.
- ID:
- ivo://CDS.VizieR/J/ApJ/609/564
- Title:
- Blazar counterparts for 3EG sources
- Short Name:
- J/ApJ/609/564
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Supplementing existing survey data with Very Large Array (VLA) observations, we have extended {gamma}-ray counterpart identifications down to decl.=-40{deg} using our "figure-of-merit" approach. We find blazar counterparts for 70% of EGRET sources above decl.=-40{deg} away from the Galaxy. Spectroscopic confirmation is in progress, and spectra for 24 sources are presented here. We find evidence that increased exposure in the bulge region allowed EGRET to detect relatively faint blazars; a clear excess of nonblazar objects in this region, however, argues for an additional (new) source class.
- ID:
- ivo://CDS.VizieR/J/A+A/556/A71
- Title:
- Blazar 0836+710 long-term multiwavelength studies
- Short Name:
- J/A+A/556/A71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The observation of gamma-ray flares from blazar 0836+710 in 2011, following a period of quiescence, offered an opportunity to study correlated activity at different wavelengths for a high-redshift (z=2.218) active galactic nucleus. Optical and radio monitoring, plus Fermi-LAT gamma-ray monitoring provided 2008-2012 coverage, while Swift offered auxiliary optical, ultraviolet, and X-ray information. Other contemporaneous observations were used to construct a broad-band spectral energy distribution.
- ID:
- ivo://CDS.VizieR/J/ApJ/901/3
- Title:
- Blazar Radio and Optical Survey (BROS)
- Short Name:
- J/ApJ/901/3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Utilizing the latest and the most sensitive radio and optical catalogs, we completed a new blazar candidate catalog, Blazar Radio and Optical Survey (BROS), which includes 88211 sources located at decl. {delta}>-40{deg} and outside the galactic plane (|b|>10{deg}). We list compact flat-spectrum radio sources of {alpha}>-0.6 ({alpha} is defined as F_{nu}_{prop.to}{nu}^{alpha}^) from 0.15GHz TGSS to 1.4GHz NVSS catalogs. We further identify optical counterparts of the selected sources by cross-matching with Pan-STARRS1 photometric data. Color-color and color-magnitude plots for the selected BROS sources clearly show two distinct populations, a "quasar-like" population consisting of both flat-spectrum radio quasars and BL Lac type objects. On the other hand, an "elliptical-like" population of mostly BL Lac type objects is buried in the elliptical galaxy. The latter population is also reported in previous catalogs, but the BROS catalog provided a new larger sample of this population, due to the lower radio flux threshold of our selection. Model calculations show that the "elliptical-like" population consists of elliptical galaxies located at redshift z<=0.5, which is also supported by the logN-logS distribution of the power-law index of 1.49+/-0.05. This BROS catalog is useful for identifying the electromagnetic counterparts of ultra-high-energy cosmic rays and PeV neutrinos recently detected by IceCube, as well as nearby BL Lac objects detectable by future high-sensitivity TeV telescopes, such as the Cherenkov Telescope Array.
- ID:
- ivo://CDS.VizieR/J/PASJ/55/947
- Title:
- Blazars and Seyfert galaxies accretion rates
- Short Name:
- J/PASJ/55/947
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Accretion rates and their correlation with cosmological redshifts for a sample of blazars and Seyfert galaxies are presented. The sample includes 77 blazars (28 FSRQs, 26 LBLs, and 23 HBLs) and 60 Seyfert galaxies, of which the extended spectral energy distribution information and redshifts are available. Within the framework of accreting black holes, the accretion rates for these sources were estimated based on their bolometric luminosities.
1907. Blazar sequence
- ID:
- ivo://CDS.VizieR/J/MNRAS/451/2750
- Title:
- Blazar sequence
- Short Name:
- J/MNRAS/451/2750
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on a large Fermi blazar sample, the blazar sequence (synchrotron peak frequency {nu}_peak_ versus synchrotron peak luminosity L_peak_) is revisited. It is found that there is significant anticorrelation between {nu}_peak_ and L_peak_ for blazars. However, after Doppler correction the anticorrelation disappears. The jet cavity power (P_jet_) is estimated from the extended radio luminosity so that it is free of beaming effects. We find that there are significant anticorrelations between P_jet_ and the beam-corrected {nu}_peak_' for both blazars and radio galaxies, which supports the blazar sequence and the unification of blazars and radio galaxies (an alternative relationship is the correlation between jet power and {gamma}-ray photon index).
- ID:
- ivo://CDS.VizieR/J/MNRAS/351/83
- Title:
- Blazars equivalent widths and radio luminosity
- Short Name:
- J/MNRAS/351/83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Blazars are currently separated into BL Lacertae objects (BL Lacs) and flat spectrum radio quasars based on the strength of their emission lines. This is performed rather arbitrarily by defining a diagonal line in the Ca H&K break value-equivalent width plane, following Marcha et al. (1996MNRAS.281..425M). We readdress this problem and put the classification scheme for blazars on firm physical grounds. We study ~100 blazars and radio galaxies from the Deep X-ray Radio Blazar Survey (DXRBS, Cat. <J/AJ/115/1253> and <J/MNRAS/323/757>) and 2-Jy radio survey and find a significant bimodality for the narrow emission line [OIII]{lambda}5007. This suggests the presence of two physically distinct classes of radio-loud active galactic nuclei (AGN). We show that all radio-loud AGN, blazars and radio galaxies, can be effectively separated into weak- and strong-lined sources using the [OIII]{lambda}5007-[OII]{lambda}3727 equivalent width plane. This plane allows one to disentangle orientation effects from intrinsic variations in radio-loud AGN. Based on DXRBS, the strongly beamed sources of the new class of weak-lined radio-loud AGN are made up of BL Lacs at the ~75 per cent level, whereas those of the strong-lined radio-loud AGN include mostly (~97 per cent) quasars.
- ID:
- ivo://CDS.VizieR/J/A+A/520/A47
- Title:
- Blazars in the Swift-BAT hard X-ray sky
- Short Name:
- J/A+A/520/A47
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a study on the blazar content in the 15-150keV map of the entire sky obtained analyzing 39 months of data collected by the BAT telescope aboard the Swift satellite. We performed a cross-correlation of the significance map, obtained with a dedicated highly efficient algorithm (Segreto et al., 2010A&A...510A..47S) for data processing and image reconstruction of the BAT survey data, with the blazar population of the Roma-BZCAT (Massaro et al., 2009, Cat. J/A+A/495/691). After corrections for source confusion and spurious detections, we found significance excesses higher than two standard deviations for 304 sources; the corresponding fraction of expected spurious associations is about 20%. We selected hard X-ray blazars according to their significance level and carried out a statistical analysis to characterise their emission properties. A sample of 121 blazars detected at a significance level sigma>3 is discussed in greater detail. The fraction of blazars with uncertain classification in this sample is considerable, more than twice with respect to the percentage obtained considering all the blazars classified in the Roma-BZCAT. We attribute the X-ray flux of the majority of selected BL Lac objects to the synchrotron emission.
- ID:
- ivo://CDS.VizieR/J/ApJ/752/61
- Title:
- Blazars in unidentified {gamma}-ray sources
- Short Name:
- J/ApJ/752/61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- One of the main scientific objectives of the ongoing Fermi mission is unveiling the nature of unidentified {gamma}-ray sources (UGSs). Despite the major improvements of Fermi in the localization of {gamma}-ray sources with respect to the past {gamma}-ray missions, about one-third of the Fermi-detected objects are still not associated with low-energy counterparts. Recently, using the Wide-field Infrared Survey Explorer survey, we discovered that blazars, the rarest class of active galactic nuclei and the largest population of {gamma}-ray sources, can be recognized and separated from other extragalactic sources on the basis of their infrared (IR) colors. Based on this result, we designed an association method for the {gamma}-ray sources to recognize if there is a blazar candidate within the positional uncertainty region of a generic {gamma}-ray source. With this new IR diagnostic tool, we searched for {gamma}-ray blazar candidates associated with the UGS sample of the second Fermi {gamma}-ray LAT catalog (2FGL). We found that our method associates at least one {gamma}-ray blazar candidate as a counterpart to each of 156 out of 313 UGSs analyzed. These new low-energy candidates have the same IR properties as the blazars associated with {gamma}-ray sources in the 2FGL catalog.
