- ID:
- ivo://CDS.VizieR/J/ApJS/135/155
- Title:
- Radio identification of 3EG EGRET sources
- Short Name:
- J/ApJS/135/155
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The method of Mattox et al. (1996ApJ...461..396M) for identifying EGRET sources with 5GHz radio sources has been applied to the 3EG EGRET catalog of Hartman et al. (1999, Cat. <J/ApJS/123/79>). Complete results are tabulated. We tabulate separately 46 EGRET sources with radio identifications which we expect to have a high probability of being correct. We suggest that these sources are appropriate for most studies of the properties of {gamma}-ray blazars as a class. All but one of these 46 sources were classified by Hartman et al. (1999, Cat. <J/ApJS/123/79>) as high-confidence identifications; and the additional source was classified by Hartman et al. (1999, Cat. <J/ApJS/123/79>) as a plausible identification. We also tabulate separately 37 additional "plausible identifications of EGRET sources with radio sources." These less secure possibilities include the remaining 21 "high-confidence identifications" of Hartman et al. (1999, Cat. <J/ApJS/123/79>), three of the 27 "lower confidence potential blazar identifications" of Hartman et al. (1999, Cat. <J/ApJS/123/79>), and an additional 15 plausible identifications which have not been suggested previously. Many of these sources require new radio and optical observations to establish them as blazars. We suggest that the 23 "lower-confidence potential blazar identifications" of Hartman et al. (1999, Cat. <J/ApJS/123/79>) which we do not find plausible should not be used in studies of the properties of the EGRET blazars. For this analysis, we have made elliptical fits to the 95% confidence contours of the position uncertainty regions of the 3EG sources.
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- ID:
- ivo://CDS.VizieR/J/ApJ/481/95
- Title:
- Radio identification of EGRET sources
- Short Name:
- J/ApJ/481/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a method to assess the reliability of the identification of EGRET sources with extragalactic radio sources. We verify that EGRET is detecting the blazar class of active galactic nuclei (AGNs). However many published identifications are found to be questionable. We provide a table of 42 blazars that we expect to be robust identifications of EGRET sources. This includes one previously unidentified EGRET source, the lensed AGN PKS 1830-210, near the direction of the Galactic center. We provide the best available positions for 16 more radio sources that are also potential identifications for previously unidentified EGRET sources. All high Galactic latitude EGRET sources (|b|>3) that demonstrate significant variability can be identified with flat-spectrum radio sources. This suggests that EGRET is not detecting any type of AGN other than blazars. This identification method has been used to establish with 99.998% confidence that the peak gamma-ray flux of a blazar is correlated with its average 5GHz radio flux. An even better correlation is seen between gamma-ray flux and the 2.29GHz flux density measured with VLBI at the base of the radio jet. Also, using high-confidence identifications, we find that the radio sources identified with EGRET sources have greater correlated VLBI flux densities than the parent population of flat radio spectrum sources.
- ID:
- ivo://CDS.VizieR/J/A+A/596/A45
- Title:
- Radio light curves of 8 AGN
- Short Name:
- J/A+A/596/A45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To fully exploit the scientific potential of the Fermi mission for the physics of active galactic nuclei (AGN), we initiated the F-GAMMA programme. Between 2007 and 2015 the F-GAMMA was the prime provider of complementary multi-frequency monitoring in the radio regime. Aims. We quantify the radio variability of {gamma}-ray blazars. We investigate its dependence on source class and examine whether the radio variability is related to the {gamma}-ray loudness. Finally, we assess the validity of a putative correlation between the two bands. Methods. The F-GAMMA performed monthly monitoring of a sample of about 60 sources at up to twelve radio frequencies between 2.64 and 228.39GHz. We perform a time series analysis on the first 2.5-yr data set to obtain variability parameters. A maximum likelihood analysis is used to assess the significance of a correlation between radio and {gamma}-ray fluxes. We present light curves and spectra (coherent within ten days) obtained with the Effelsberg 100m and IRAM 30m telescopes. All sources are variable across all frequency bands with amplitudes increasing with frequency up to rest frame frequencies of around 60-80GHz as expected by shock-in-jet models. Compared to flat-spectrum radio quasars (FSRQs), BL Lacertae objects (BL Lacs) show systematically lower variability amplitudes, brightness temperatures, and Doppler factors at lower frequencies, while the difference vanishes towards higher ones. The time scales appear similar for the two classes. The distribution of spectral indices appears flatter or more inverted at higher frequencies for BL Lacs. Evolving synchrotron self-absorbed components can naturally account for the observed spectral variability. We find that the Fermi-detected sources show larger variability amplitudes, brightness temperatures, and Doppler factors than non-detected ones. Flux densities at 86.2 and 142.3GHz correlate with 1GeV fluxes at a significance level better than 3{sigma}, implying that {gamma} rays are produced very close to the mm-band emission region.
- ID:
- ivo://CDS.VizieR/J/A+AS/131/11
- Title:
- Radio sources related to gamma-ray emission
- Short Name:
- J/A+AS/131/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table 2 lists the individual flux density measurements for 47 radio sources as observed with the Effelsberg 100-m telescope.
- ID:
- ivo://CDS.VizieR/J/ApJ/731/103
- Title:
- Redshift catalog for Swift long GRBs
- Short Name:
- J/ApJ/731/103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of the redshifts for most long-duration gamma-ray bursts (GRBs) by Swift from 2004 December 20 to 2008 July 23 (258 bursts in total). All available information is collected, including spectroscopic redshifts, photometric redshift limits, and redshifts calculated from various luminosity relations. Error bars for the redshifts derived from the luminosity relations are asymmetric, with tails extended to the high-redshift end, and this effect is evaluated by looking at the 30% of Swift bursts with spectroscopic redshifts. A simulation is performed to eliminate this asymmetric effect, and the resultant redshift distribution is deconvolved. We test and confirm this simulation on the sample of bursts with known spectroscopic redshifts and then apply it to the 70% of Swift bursts that do not have spectroscopic measures. A final intrinsic redshift distribution is then made for almost all Swift bursts, and the efficiency of the spectroscopic detections is evaluated. The efficiency of spectroscopic redshifts varies from near unity at low redshift to 0.5 at z=1, to near 0.3 at z=4, and to 0.1 at z=6. We also find that the fraction of GRBs with z>5 is ~10%, and this fraction is compared with simulations from a cosmological model.
- ID:
- ivo://CDS.VizieR/J/ApJ/780/73
- Title:
- Redshifts of BL Lac objects from Fermi
- Short Name:
- J/ApJ/780/73
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Fermi has provided the largest sample of {gamma}-ray-selected blazars to date. In this work we use a uniformly selected set of 211 BL Lacertae (BL Lac) objects detected by Fermi during its first year of operation. We obtained redshift constraints for 206 out of the 211 BL Lac objects in our sample, making it the largest and most complete sample of BL Lac objects available in the literature. We use this sample to determine the luminosity function of BL Lac objects and its evolution with cosmic time. We find that for most BL Lac classes the evolution is positive, with a space density peaking at modest redshift (z{approx}1.2). Low-luminosity, high-synchrotron-peaked (HSP) BL Lac objects are an exception, showing strong negative evolution, with number density increasing for z<~0.5. Since this rise corresponds to a drop-off in the density of flat-spectrum radio quasars (FSRQs), a possible interpretation is that these HSPs represent an accretion-starved end state of an earlier merger-driven gas-rich phase. We additionally find that the known BL Lac correlation between luminosity and photon spectral index persists after correction for the substantial observational selection effects with implications for the so-called "blazar sequence." Finally, by estimating the beaming corrections to the luminosity function, we find that BL Lac objects have an average Lorentz factor of {gamma}=6.1_-0.8_^+1.1^, and that most are seen within 10{deg} of the jet axis.
- ID:
- ivo://CDS.VizieR/J/A+A/629/A131
- Title:
- Reduced X-shooter spectra of GRB 190114A
- Short Name:
- J/A+A/629/A131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the detections of molecular hydrogen (H_2_), vibrationally-excited H_2_ (H_2_*), and neutral atomic carbon (CI), an efficient tracer of molecular gas, in two new afterglow spectra of GRBs 181020A (z=2.938) and 190114A (z=3.376), observed with X-shooter at the Very Large Telescope (VLT). Both host-galaxy absorption systems are characterized by strong damped Lyman-alpha absorbers (DLAs) and substantial amounts of molecular hydrogen with logN(HI,H_2_)=22.20+/-0.05, 20.40+/-0.04 (GRB 181020A) and logN(HI, H_2_)=22.15+/-0.05, 19.44+/-0.04 (GRB 190114A). The DLA metallicites, depletion levels, and dust extinctions are within the typical regimes probed by GRBs with [Zn/H]=-1.57+/-0.06, [Zn/Fe]=0.67+/-0.03, and AV=0.27+/-0.02mag (GRB 181020A) and [Zn/H]=-1.23+/-0.07, [Zn/Fe]=1.06+/-0.08, and AV=0.36+/-0.02mag (GRB 190114A). In addition, we examine the molecular gas content of all known H2-bearing GRB-DLAs and explore the physical conditions and characteristics required to simultaneously probe CI and H_2_*. We confirm that H2 is detected in all CI- and H2*-bearing GRB absorption systems, but that these rarer features are not necessarily detected in all GRB H2 absorbers. We find that a large molecular fraction of f_H2_>~10^-3^ is required for CI to be detected. The defining characteristic for H_2_* to be present is less clear, though a large H_2_ column density is an essential factor. We also find that the observed line profiles of the molecular-gas tracers are kinematically "cold", with small velocity offsets of {delta}v<20km/s from the bulk of the neutral absorbing gas. We then derive the H_2_ excitation temperatures of the molecular gas and find that they are relatively low with Tex~=100-300K, however, there could be evidence of warmer components populating the high-J H_2_ levels in GRBs 181020A and 190114A. Finally, we demonstrate that even though the X-shooter GRB afterglow campaign has been successful in recovering several H2-bearing GRB-host absorbers, this sample is still hampered by a significant dust bias excluding the most dust-obscured H_2_ absorbers from identification. CI and H_2_* could open a potential route to identify molecular gas even in low-metallicity or highly dust-obscured bursts, though they are only efficient tracers for the most H2-rich GRB-host absorption systems.
- ID:
- ivo://CDS.VizieR/J/ApJS/217/2
- Title:
- Refined associations of Fermi/LAT sources
- Short Name:
- J/ApJS/217/2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Fermi-Large Area Telescope (LAT) First Source Catalog (1FGL) was released in 2010 February and the Fermi-LAT 2-Year Source Catalog (2FGL) appeared in 2012 April, based on data from 24 months of operation. Since they were released, many follow up observations of unidentified {gamma}-ray sources have been performed and new procedures for associating {gamma}-ray sources with potential counterparts at other wavelengths have been developed. Here we review and characterize all of the associations as published in the 1FGL and 2FGL catalogs on the basis of multifrequency archival observations. In particular, we located 177 spectra for the low-energy counterparts that were not listed in the previous Fermi catalogs, and in addition we present new spectroscopic observations of eight {gamma}-ray blazar candidates. Based on our investigations, we introduce a new counterpart category of "candidate associations" and propose a refined classification for the candidate low-energy counterparts of the Fermi sources. We compare the 1FGL-assigned counterparts with those listed in 2FGL to determine which unassociated sources became associated in later releases of the Fermi catalogs. We also search for potential counterparts to all of the remaining unassociated Fermi sources. Finally, we prepare a refined and merged list of all of the associations of 1FGL plus 2FGL that includes 2219 unique Fermi objects. This is the most comprehensive and systematic study of all the associations collected for the {gamma}-ray sources available to date. We conclude that 80% of the Fermi sources have at least one known plausible {gamma}-ray emitter within their positional uncertainty regions.
- ID:
- ivo://CDS.VizieR/J/A+A/489/849
- Title:
- Revised catalogue of EGRET gamma-ray sources
- Short Name:
- J/A+A/489/849
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of point gamma-ray sources detected by the EGRET detector on the Compton Gamma Ray Observatory. We used the entire gamma-ray dataset of reprocessed photons at energies above 100MeV and new Galactic interstellar emission models based on CO, HI, dark gas, and interstellar radiation field data. Two different assumptions are used to describe the cosmic-ray distribution in the Galaxy to analyse the systematic uncertainties in source detection and characterization. We applied a 2-dimensional maximum-likelihood detection method similar to that used to analyze the 3rd EGRET catalogue. The revised catalogue lists 188 sources, 14 of which are marked as confused, in contrast to the 271 entries of the 3rd EGRET (3EG) catalogue. We do not detect 107 sources discovered previously because additional structure is present in the interstellar background.
- ID:
- ivo://CDS.VizieR/J/ApJ/784/159
- Title:
- Revisited jet bending in {gamma}-ray AGNs
- Short Name:
- J/ApJ/784/159
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the hypothesis that {gamma}-ray-quiet active galactic nuclei (AGNs) have a greater tendency for jet bending than {gamma}-ray-loud AGNs, revisiting the analysis of Tingay et al. We perform a statistical analysis using a large sample of 351 radio-loud AGNs along with {gamma}-ray identifications from the Fermi Large Area Telescope (LAT). Our results show no statistically significant differences in jet-bending properties between {gamma}-ray-loud and {gamma}-ray-quiet populations, indicating that jet bending is not a significant factor for {gamma}-ray detection in AGNs.
