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- ID:
- ivo://CDS.VizieR/J/ApJ/851/33
- Title:
- Multi-wavelength analysis of CGRaBS blazars
- Short Name:
- J/ApJ/851/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a multi-frequency, time-averaged analysis of blazars included in the Candidate Gamma-ray Blazar Survey catalog. Our sample consists of 324 {gamma}-ray detected ({gamma}-ray loud) and 191 {gamma}-ray undetected ({gamma}-ray quiet) blazars; we consider all the data up to 2016 April 1. We find that both the {gamma}-ray loud and {gamma}-ray quiet blazar populations occupy similar regions in the WISE color-color diagram, and {gamma}-ray loud sources are brighter in the radio and X-ray bands. A simple one-zone synchrotron inverse-Compton emission model is applied to derive the physical properties of both populations. We find that the central black hole mass and accretion disk luminosity (L_disk_) computed from the modeling of the optical-UV emission with a Shakura-Sunyaev disk reasonably matches that estimated from the optical spectroscopic emission-line information. A significantly larger Doppler boosting in the {gamma}-ray loud blazars is noted, and their jets are more radiatively efficient. On the other hand, the {gamma}-ray quiet objects are more MeV-peaked and thus could be potential targets for next-generation MeV missions. Our results confirm earlier findings about the accretion-jet connection in blazars; however, many of the {gamma}-ray quiet blazars tend to deviate from the recent claim that the jet power exceeds L_disk_ in blazars. A broadband study, considering a larger set of {gamma}-ray quiet objects and also including BL Lacs, will be needed to confirm/reject this hypothesis as well as to verify the evolution of the powerful high-redshift blazars into their low-power nearby counterparts.
- ID:
- ivo://CDS.VizieR/J/A+A/641/A62
- Title:
- Multi-wavelength census of blazars
- Short Name:
- J/A+A/641/A62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Blazars are the rarest and most powerful active galactic nuclei, playing a crucial and growing role in today multi-frequency and multi-messenger astrophysics. They dominate the high-energy extragalactic sky and recently have been associated to high-energy astrophysical neutrinos, and they may be among the accelerators of the ultra-high energy cosmic rays. Current blazar catalogs, however, are incomplete and particularly depleted at low Galactic latitudes. We aim at augmenting the current blazar census starting from a sample of ALMA calibrators that provides more homogeneous sky coverage, especially at low Galactic latitudes, to build a catalog of blazar candidates that can provide candidate counterparts to unassociated gamma-ray sources and to sources of high-energy neutrino emission or ultra-high energy cosmic rays. Starting from the ALMA Calibrator Catalog we built a catalog of 1580 blazar candidates (ALMA Blazar Candidates) for which we collect multi-wavelength information, including Gaia photometric, parallax and proper motion data, SDSS and LAMOST photometric and spectral data, WISE photometric data, X-ray (Swift-XRT, Chandra-ACIS and XMM-Newton-EPIC) count-rates and spectra, and Fermi-LAT fluxes and spectral slopes. We also compared our ALMA Blazar Candidates with existing blazar catalogs, like 4FGL, 3HSP, WIBRaLS2 and the KDEBLLACS. The ALMA Blazar Candidates catalogue fills the lack of low Galactic latitude sources in current blazar catalogues. Cross-matching this catalog with Gaia DR2, SDSS DR12, LAMOST DR5, AllWISE and 4FGL catalogues we obtained 805, 295, 31, 1311 and 259 matches, respectively. ALMA Blazar Candidates are significantly dimmer than known blazars in Gaia g band, while the difference in the Gaia b-r colour between the two populations is less pronounced. Also, ALMA Blazar Candidates sources appear bluer in SDSS than known blazars, although with low statistical significance. Most ALMA Blazar Candidates classified as QSO and BL Lac fall into the SDSS colour regions of low redshift quasars, with some QSOs entering the regions of higher redshift quasars. We collected 110 optical spectra in SDSS DR12 and LAMOST DR5, which mostly classify the corresponding sources as QSO (98), while 12 sources resulted galactic objects. Regarding WISE colours, we found that ABC sources are significantly bluer than known blazars in the w2-w3 and w3-w4 colours. In X-rays we detected 173 ALMA Blazar Candidates, and we were able to extract a X-ray spectra for 92 of them. Our sources are on average similar in X-rays to known blazar in terms of count-rates and spectral slopes, implying that our sample is covering the same region of the blazar parameter space in this band. A comparison of gamma-ray properties shown that ALMA Blazar Candidates are on average dimmer, and their gamma-ray spectra are softer than known blazars, indicating a significant contribution of FSRQ sources. Making use of WISE colours, we classified 715 ALMA Blazar Candidates as candidate gamma-ray blazar of different classes. We built a new catalogue of 1580 candidate blazars with a rich multi-wavelength data-set, filling the lack of low Galactic latitude sources in current blazar catalogues. This will be particularly important to identify the source population of high energy neutrinos or ultra-high energy cosmic rays, or to verify the Gaia optical reference frame. In addition, ALMA Blazar Candidates can be investigated both through optical spectroscopic observation campaigns or through repeated photometric observations for variability studies. In this context, the data collected by the upcoming LSST surveys will provide a key tool to investigate the possible blazar nature of these sources.
- ID:
- ivo://CDS.VizieR/J/AJ/144/101
- Title:
- Multiwavelength data of IRAS 20050+2720 young SFR
- Short Name:
- J/AJ/144/101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- IRAS 20050+2720 is young star-forming region at a distance of 700pc without apparent high-mass stars. We present results of our multi-wavelength study of IRAS 20050+2720 which includes observations by Chandra and Spitzer, and Two Micron All Sky Survey and UBVRI photometry. In total, about 300 young stellar objects (YSOs) in different evolutionary stages are found. We characterize the distribution of YSOs in this region using a minimum spanning tree analysis. We newly identify a second cluster core, which consists mostly of class II objects, about 10' from the center of the cloud. YSOs of earlier evolutionary stages are more clustered than more evolved objects. The X-ray luminosity function (XLF) of IRAS 20050+2720 is roughly lognormal, but steeper than the XLF of the more massive Orion Nebula complex. IRAS 20050+2720 shows a lower N_H_/A_K_ ratio compared with the diffuse interstellar medium.
- ID:
- ivo://CDS.VizieR/J/ApJ/712/405
- Title:
- Multiwavelength observations of 3C 454.3 III.
- Short Name:
- J/ApJ/712/405
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on 18 months of multiwavelength observations of the blazar 3C 454.3 (Crazy Diamond) carried out in the period 2007 July-2009 January. During the 2008 May-2009 January period, the source average flux was highly variable, with a clear fading trend toward the end of the period, from an average {gamma}-ray flux F_E>100MeV_>~200x10^-8^photons/cm^2^/s in 2008 May-June, to F_E>100MeV_~80x10^-8^photons/cm^-2^/s in 2008 October-2009 January. In 2007 July-August and 2008 May-June, 3C 454.3 was monitored by Rossi X-ray Timing Explorer (RXTE). We also carried out simultaneous Swift observations during all AGILE campaigns. Swift/XRT detected 3C 454.3 with an observed flux in the 2-10keV energy band in the range (0.9-7.5)x10^-11^erg/cm^2^/s and a photon index in the range {Gamma}_XRT_=1.33-2.04. In the 15-150keV energy band, when detected, the source has an average flux of about 5mCrab. GASP-WEBT monitored 3C 454.3 during the whole 2007-2008 period in the radio, millimeter, near-IR, and optical bands. The observations show an extremely variable behavior at all frequencies, with flux peaks almost simultaneous with those at higher energies. An analysis of 15GHz and 43GHz VLBI core radio flux observations in the period 2007 July-2009 February shows an increasing trend of the core radio flux, anti-correlated with the higher frequency data, allowing us to derive the value of the source magnetic field.
- ID:
- ivo://CDS.VizieR/J/ApJ/816/53
- Title:
- Multiwavelength obs. of BL Lac in 2012-2013
- Short Name:
- J/ApJ/816/53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- BL Lac, the eponymous blazar, flared to historically high levels at millimeter, infrared, X-ray, and gamma-ray wavelengths in 2012. We present observations made with Herschel, Swift, NuSTAR, Fermi, the Submillimeter Array, CARMA, and the VLBA in 2012-2013, including three months with nearly daily sampling at several wavebands. We have also conducted an intensive campaign of 30 hr with every-orbit observations by Swift and NuSTAR, accompanied by Herschel, and Fermi observations. The source was highly variable at all bands. Time lags, correlations between bands, and the changing shapes of the spectral energy distributions can be explained by synchrotron radiation and inverse Compton emission from nonthermal seed photons originating from within the jet. The passage of four new superluminal very long baseline interferometry knots through the core and two stationary knots about 4 pc downstream accompanied the high flaring in 2012-2013. The seed photons for inverse Compton scattering may arise from the stationary knots and from a Mach disk near the core where relatively slow-moving plasma generates intense nonthermal radiation. The 95 spectral energy distributions obtained on consecutive days form the most densely sampled, broad wavelength coverage for any blazar. The observed spectral energy distributions and multi-waveband light curves are similar to simulated spectral energy distributions and light curves generated with a model in which turbulent plasma crosses a conical shock with a Mach disk.
- ID:
- ivo://CDS.VizieR/J/ApJ/881/125
- Title:
- 2014-2018 multiwavelength obs. of PKS 1502+106
- Short Name:
- J/ApJ/881/125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The origin of the multiband activities (outbursts/flares) of blazars is still a heavily debated topic. Shock and magnetic reconnection have long been considered as possible triggers of the multiband activities. In this paper, we present an exploration of the origin of multiband activities for a high-redshift (z=1.8385) flat-spectrum radio quasar PKS 1502+106. Utilizing multiband data from radio to {gamma}-ray and optical polarization observations, we investigate two dramatic activities in detail: a {gamma}-ray- dominated outburst in 2015 and an optical-dominated outburst in 2017. Our main results are as follows. (I) A fast {gamma}-ray flare with a flux-doubling timescale as short as 1 hr in 2015 is discovered. Based on the variability timescale, the physical parameters of the flaring region (e.g., minimum Doppler factor, emission region size, etc.) are constrained. At the peak of the flare, the {gamma}-ray spectrum hardens to {Gamma}_{gamma}_=1.82+/-0.04 and exhibits an obvious curvature/break characteristic that is caused by the typical "cooling break." Modeling of multiband spectral energy distributions reveal a very hard electronic energy spectrum with the electronic spectral index of 1.07+/-0.53. This result suggests that this fast {gamma}-ray flare may be triggered by magnetic reconnection. (II) During the outburst in 2017, the degree of optical polarization and optical fluxes showed a very tight correlation. By analyzing the Stokes parameters of polarization observations, our results show that this outburst could be triggered by a transverse shock with a compression ratio of {eta}>2.2, and the magnetic field intensity of the shock emission region is about 0.032G.
- ID:
- ivo://CDS.VizieR/J/A+A/507/1277
- Title:
- Multiwavelength photometry of CDFS X-ray sources
- Short Name:
- J/A+A/507/1277
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The co-evolution of host galaxies and the active black holes which reside in their centre is one of the most important topics in modern observational cosmology. Here we present a study of the properties of obscured active galactic nuclei (AGN) detected in the CDFS 1 Ms observation and their host galaxies. We limited the analysis to the MUSIC area, for which deep K-band observations obtained with ISAAC@VLT are available, ensuring accurate identifications of the counterparts of the X-ray sources as well as reliable determination of photometric redshifts and galaxy parameters, such as stellar masses and star formation rates. In particular, we: 1) refined the X-ray/infrared/optical association of 179 sources in the MUSIC area detected in the Chandra observation; 2) studied the host galaxies observed and rest frame colors and properties.
- ID:
- ivo://CDS.VizieR/J/A+A/392/795
- Title:
- Multi-wavelength study of 2 galaxy clusters
- Short Name:
- J/A+A/392/795
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from optical, X-ray and radio observations of two X-ray bright (L_X_~10^45^erg/s) galaxy clusters. Abell 1451 is at redshift z=0.1989 and has line-of-sight velocity dispersion {sigma}_V_=1330km/s as measured from 57 cluster galaxies. It has regular X-ray emission without signs of substructure, a Gaussian velocity distribution, lack of a cooling flow region and significant deviations from the observed scaling laws between luminosity, temperature and velocity dispersion, indicating a possible merging shock. There is only one spectroscopically confirmed cluster radio galaxy, which is close to the X-ray peak. 1RXS J131423.6-251521 (for short RXJ1314-25) has z=0.2474 and {sigma}_V_=1100km/s from 37 galaxies. There are two distinct galaxy groups with a projected separation of ~700kpc. The velocity histogram is bi-modal with a redshift-space separation of ~1700km/s, and the X-ray emission is double peaked. Although there are no spectroscopically confirmed cluster radio galaxies, we have identified a plausible relic source candidate.
- ID:
- ivo://CDS.VizieR/J/MNRAS/391/1279
- Title:
- Multiwavelength study of NGC 7419
- Short Name:
- J/MNRAS/391/1279
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using new UBVRI H{alpha} CCD photometric observations and the archival infrared and X-ray data, we have carried out a multiwavelength study of a Perseus arm young open star cluster NGC 7419. Using XMM-Newton observations, we found several X-ray sources in the cluster region but none of the Herbig Ae/Be stars is detected in X-rays.