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851. TANAMI II. Additional sources
ID:
ivo://CDS.VizieR/J/A+A/610/A1
Title:
TANAMI II. Additional sources
Short Name:
J/A+A/610/A1
Date:
21 Oct 2021
Publisher:
CDS
Description:
TANAMI is a multiwavelength program monitoring active galactic nuclei (AGN) south of -30{deg} declination including high-resolution Very Long Baseline Interferometry (VLBI) imaging, radio, optical/UV, X-ray and {gamma}-ray studies. We have previously published first-epoch 8.4GHz VLBI images of the parsec-scale structure of the initial sample. In this paper, we present images of 39 additional sources. The full sample comprises most of the radio- and {gamma}-ray brightest AGN in the southern quarter of the sky, overlapping with the region from which high-energy (>100TeV) neutrino events have been found. We characterize the parsec-scale radio properties of the jets and compare with the quasi-simultaneous Fermi/LAT {gamma}-ray data. Furthermore, we study the jet properties of sources which are in positional coincidence with high-energy neutrino events as compared to the full sample. We test the positional agreement of high-energy neutrino events with various AGN samples. TANAMI VLBI observations at 8.4GHz are made with Southern-Hemisphere radio telescopes located in Australia, Antarctica, Chile, New Zealand, and South Africa. Our observations yield the first images of many jets below -30{deg} declination at milliarcsecond resolution. We find that {gamma}-ray loud TANAMI sources tend to be more compact on parsec-scales and have higher core brightness temperatures than {gamma}-ray faint jets, indicating higher Doppler factors. No significant structural difference is found between sources in positional coincidence with high-energy neutrino events and other TANAMI jets. The 22 {gamma}-ray brightest AGN in the TANAMI sky show only a weak positional agreement with high-energy neutrinos demonstrating that the >100TeV IceCube signal is not simply dominated by a small number of the {gamma}-ray brightest blazars. Instead, a larger number of sources have to contribute to the signal with each individual source having only a small Poisson probability for producing an event in multi-year integrations of current neutrino detectors.
852. TANAMI monitoring of Centaurus A.
ID:
ivo://CDS.VizieR/J/A+A/569/A115
Title:
TANAMI monitoring of Centaurus A.
Short Name:
J/A+A/569/A115
Date:
21 Oct 2021
Publisher:
CDS
Description:
Centaurus A (Cen A) is the closest radio-loud active galactic nucleus. Very Long Baseline Interferometry (VLBI) enables us to study the spectral and kinematic behavior of the radio jet-counterjet system on milliarcsecond scales, providing essential information for jet emission and propagation models. In the framework of the TANAMI monitoring, we investigate the kinematics and complex structure of Cen A on subparsec scales. We have been studying the evolution of the central parsec jet structure of Cen A for over 3.5-years. The proper motion analysis of individual jet components allows us to constrain jet formation and propagation and to test the proposed correlation of increased high-energy flux with jet ejection events. Cen A is an exceptional laboratory for such a detailed study because its proximity translates to unrivaled linear resolution, where one milliarcsecond corresponds to 0.018pc. As a target of the southern-hemisphere VLBI monitoring program TANAMI, observations of Cen A are done approximately every six months at 8.4GHz with the Australian Long Baseline Array (LBA) and associated telescopes in Antarctica, Chile, New Zealand, and South Africa, complemented by quasi-simultaneous 22.3GHz observations. The first seven epochs of high-resolution TANAMI VLBI observations at 8.4GHz of Cen A are presented, resolving the jet on (sub-)milliarcsecond scales. They show a differential motion of the subparsec scale jet with significantly higher component speeds farther downstream where the jet becomes optically thin. We determined apparent component speeds within a range of 0.1c to 0.3c and identified long-term stable features. In combination with the jet-to-counterjet ratio, we can constrain the angle to the line of sight to {theta}~12{deg}-45{deg}. The high-resolution kinematics are best explained by a spine-sheath structure supported by the downstream acceleration occurring where the jet becomes optically thin. On top of the underlying, continuous flow, TANAMI observations clearly resolve individual jet features. The flow appears to be interrupted by an obstacle causing a local decrease in surface brightness and circumfluent jet behavior. We propose a jet-star interaction scenario to explain this appearance. The comparison of jet ejection times to high X-ray flux phases yields a partial overlap of the onset of the X-ray emission and increasing jet activity, but the limited data do not support a robust correlation.
853. TANAMI radio galaxies I
ID:
ivo://CDS.VizieR/J/A+A/627/A148
Title:
TANAMI radio galaxies I
Short Name:
J/A+A/627/A148
Date:
21 Oct 2021
Publisher:
CDS
Description:
In the framework of the TANAMI multi-wavelength and VLBI monitoring, we study the evolution of the parsec-scale radio emission in radio galaxies in the southern hemisphere and their relationship to the gamma-ray properties of the sources. Our study investigates systematically, for the first time, the relationship between the two energy regimes in radio galaxies. In this first paper, we focus on Fermi-LAT-detected sources. The TANAMI program monitors a large sample of radio-loud AGN at 8.4GHz and 22.3GHz with the Australian Long Baseline Array(LBA) and associated telescopes in Antarctica, Chile, New Zealand and South Africa. We perform a kinematic analysis for five gamma-ray detected radio galaxies using multi-epoch 8.4 GHz VLBI images, deriving limits on intrinsic jet parameters such as speed and viewing angle. We analyzed103 months of Fermi-LAT data in order to study possible connections between the gamma-ray properties and the pc-scale jets of Fermi-LAT-detected radio galaxies, both in terms of variability and average properties. We discuss the individual source results and draw preliminary conclusions on sample properties including published VLBI results from the MOJAVE survey, with a total of fifteen sources. We find that the first gamma-ray detection of Pictor A might be associated with the passage of a new VLBI component through the radio core, which appears to be a defining feature of high-energy emitting Fanaroff-Riley type II radio galaxies. For the peculiar AGN PKS 0521-36, we detect subluminal parsec-scale jet motions, and we confirm the presence of fast gamma-ray variability in the source down to timescales of 6 hours, which is not accompanied by variations in the VLBI jet. We robustly confirm the presence of significant superluminal motion, up to {beta}_app_~3, in the jet of the TeV radio galaxy PKS 0625-35. Our VLBI results constrain the jet viewing angle to be {theta}<53{deg}, allowing for the possibility of a closely aligned jet. Finally, by analyzing the first pc-scale multi-epoch images of the prototypical Compact Symmetric Object (CSO) PKS 1718-649, we place an upper limit on the separation speed between the two mini-lobes, which in turn allows us to derive a lower limit on the age of the source.Conclusions.We can draw some preliminary conclusions on the relationship between pc-scale jets and gamma-ray emission in radio galaxies, basedonFermi-LAT-detected sources with available multi-epoch VLBI measurements. We find that the VLBI core flux density correlates with the gamma-ray flux, as seen in blazars. On the other hand, the gamma-ray luminosity does not show any dependence on the core brightness temperature and core dominance, two common indicators of jet Doppler boosting. This seems to indicate that gamma-ray emission in radio galaxies is not driven by orientation-dependent effects, as in blazars, which is consistent with the unified model of jetted AGN.
854. TANAMI radio galaxies II
ID:
ivo://CDS.VizieR/J/A+A/641/A152
Title:
TANAMI radio galaxies II
Short Name:
J/A+A/641/A152
Date:
21 Oct 2021
Publisher:
CDS
Description:
This is the second paper in our series studying the evolution of parsec-scale radio emission in radio galaxies in the southern hemisphere. Following our study of the radio and high-energy properties of gamma-ray-emitting sources, here we investigate the kinematic and spectral properties of the parsec-scale jets of radio galaxies that have not yet been detected by the Fermi Large Area Telescope (Fermi-LAT) instrument on board NASA's Fermi Gamma-ray Space Telescope. For many sources, these results represent the first milliarcsecond resolution information in the literature. These studies were conducted within the framework of the Tracking Active Nuclei with Austral Milliarcsecond Interferometry (TANAMI) monitoring program and in the context of high-energy gamma-ray observations from Fermi-LAT. We take advantage of the regular 8.4GHz and 22.3GHz Very Long Baseline Interferometry (VLBI) observations provided by the TANAMI monitoring program, and explore the kinematic properties of six gamma-ray-faint radio galaxies. We complement this with ~8.5 years of Fermi-LAT data, deriving updated upper limits on the gamma-ray emission from this subsample of TANAMI radio galaxies. We include publicly available VLBI kinematics of gamma-ray-quiet radio galaxies monitored by the MOJAVE program and perform a consistent Fermi-LAT analysis. We combine these results with those from our previous paper to construct the largest sample of radio galaxies with combined VLBI and gamma-ray measurements to date. The connection between parsec-scale jet emission and high-energy properties in the misaligned jets of radio galaxies is explored. We report for the first time evidence of superluminal motion up to beta_app_=3.6 in the jet of the gamma-ray-faint radio galaxy PKS 2153-69. We find a clear trend of higher apparent speed as a function of distance from the jet core, which indicates that the jet is still being accelerated on scales of tens of parsecs, or ~10^5^R_{sun}_, corresponding to the end of the collimation and acceleration zone in nearby radio galaxies. We find evidence of subluminal apparent motion in the jets of PKS 1258-321 and IC 4296, and no measurable apparent motion for PKS 1549-79, PKS 1733-565 and PKS 2027-308. For all these sources, TANAMI provides the first multi-epoch kinematic analysis on parsec scales. We then compare the VLBI properties of gamma-ray-detected and undetected radio galaxies, and find that the two populations show a significantly different distribution of median core flux density, and, possibly, of median core brightness temperature. In terms of correlation between VLBI and gamma-ray properties, we find a significant correlation between median core flux density and gamma-ray flux, but no correlation with typical Doppler boosting indicators such as median core brightness temperature and core dominance. Our study suggests that high-energy emission from radio galaxies is related to parsec-scale radio emission from the inner jet, but is not driven by Doppler boosting effects, in contrast to the situation in their blazar counterparts. This implies that gamma-ray loudness does not necessarily reflect a higher prevalence of boosting effects.
855. TESS light curve of AGN NGC 4395
ID:
ivo://CDS.VizieR/J/ApJ/899/136
Title:
TESS light curve of AGN NGC 4395
Short Name:
J/ApJ/899/136
Date:
03 Dec 2021 13:06:51
Publisher:
CDS
Description:
We present optical light curves from the Transiting Exoplanet Survey Satellite (TESS) for the archetypical dwarf active galactic nucleus (AGN) in the nearby galaxy NGC 4395 hosting a ~105M{sun} supermassive black hole (SMBH). Significant variability is detected on timescales from weeks to hours before reaching the background noise level. The ~month-long, 30 minute-cadence, high-precision TESS light curve can be well fit by a simple damped random walk (DRW) model, with the damping timescale {tau}DRW constrained to be 2.3_-0.7_^+1.8^days (1{sigma}). NGC 4395 lies almost exactly on the extrapolation of the {tau }_DRW_-M_BH_ relation measured for AGNs with BH masses that are more than three orders of magnitude larger. The optical variability periodogram can be well fit by a broken power law with the high-frequency slope (-1.88{+/-}0.15) and the characteristic timescale ({tau}_br_=1/(2{pi}f_br_)=1.4_-0.5_^+1.9^days) consistent with the DRW model within 1{sigma}. This work demonstrates the power of TESS light curves in identifying low-mass accreting SMBHs with optical variability, and a potential global {tau}_DRW}_-M_BH_ relation that can be used to estimate SMBH masses with optical variability measurements.
856. The 2BIGB gamma-ray blazars catalog
ID:
ivo://CDS.VizieR/J/MNRAS/493/2438
Title:
The 2BIGB gamma-ray blazars catalog
Short Name:
J/MNRAS/493/2438
Date:
21 Oct 2021
Publisher:
CDS
Description:
This paper presents the results of a {gamma}-ray likelihood analysis over all the extreme and high synchrotron peak blazars (EHSP and HSP) from the 3HSP catalogue. We investigate 2013 multifrequency positions under the eyes of Fermi Large Area Telescope, considering 11yr of observations in the energy range between 500MeV and 500GeV, which results in 1160 {gamma}-ray signatures detected down to the TS=9 threshold. The detections include 235 additional sources concerning the Fermi Large Area Telescope Fourth Source Catalog (4FGL), all confirmed via high-energy TS (Test Statistic) maps, and represent an improvement of ~25% for the number of EHSP and HSP currently described in {gamma}-rays. We build the {gamma}-ray spectral energy distribution (SED) for all the 1160 2BIGB sources, plot the corresponding {gamma}-ray logN-logS, and measure their total contribution to the extragalactic gamma-ray background, which reaches up to ~33% at 100GeV. Also, we show that the {gamma}-ray detectability improves according to the synchrotron peak flux as represented by the figure of merit parameter, and note that the search for TeV peaked blazars may benefit from considering HSP and EHSP as a whole, instead of EHSPs only. The 2BIGB acronym stands for 'Second Brazil-ICRANet Gamma-ray Blazars' catalogue.
857. The black hole-bulge relationship
ID:
ivo://CDS.VizieR/J/AJ/135/928
Title:
The black hole-bulge relationship
Short Name:
J/AJ/135/928
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have measured the stellar velocity dispersions ({sigma}_*_) and estimated the central black hole (BH) masses for over 900 broad-line active galactic nuclei (AGNs) observed with the Sloan Digital Sky Survey. The sample includes objects which have redshifts up to z=0.452, high-quality spectra, and host galaxy spectra dominated by an early-type (bulge) component. The AGN and host galaxy spectral components were decomposed using an eigenspectrum technique. The BH masses (M_BH_) were estimated from the AGN broad-line widths, and the velocity dispersions were measured from the stellar absorption spectra of the host galaxies. The range of black hole masses covered by the sample is approximately 10^6^<M_BH_<10^9^M_{sun}_. We find no significant evolution in the M_BH_-{sigma}_*_ relation with redshift, up to z~0.4, after controlling for possible dependences on other variables. Interested readers can contact the authors to obtain the eigenspectrum decomposition coefficients of our objects.
858. The Chandra COSMOS survey. III.
ID:
ivo://CDS.VizieR/J/ApJS/201/30
Title:
The Chandra COSMOS survey. III.
Short Name:
J/ApJS/201/30
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Chandra COSMOS Survey (C-COSMOS) is a large, 1.8Ms, Chandra program that has imaged the central 0.9deg^2^ of the COSMOS field down to limiting depths of 1.9x10^-16^erg/cm^2^/s in the soft (0.5-2keV) band, 7.3x10^-16^erg/cm^2^/s in the hard (2-10keV) band, and 5.7x10^-16^erg/cm^2^/s in the full (0.5-10keV) band. In this paper we report the i, K, and 3.6um identifications of the 1761 X-ray point sources. We use the likelihood ratio technique to derive the association of optical/infrared counterparts for 97% of the X-ray sources. For most of the remaining 3%, the presence of multiple counterparts or the faintness of the possible counterpart prevented a unique association. For only 10 X-ray sources we were not able to associate a counterpart, mostly due to the presence of a very bright field source close by. Only two sources are truly empty fields. The full catalog, including spectroscopic and photometric redshifts and classification described here in detail, is available online.
859. The COS CGM compendium. I. Initial results
ID:
ivo://CDS.VizieR/J/ApJ/866/33
Title:
The COS CGM compendium. I. Initial results
Short Name:
J/ApJ/866/33
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a neutral hydrogen-selected absorption-line survey of gas with HI column densities 15<logN_HI_<19 at z<~1 using the Cosmic Origins Spectrograph on the Hubble Space Telescope. Our main aim is to determine the metallicity distribution of these absorbers. Our sample consists of 224 absorbers selected on the basis of their HI absorption strength. Here we discuss the properties of our survey and the immediate empirical results. We find singly and doubly ionized metal species, and HI typically have similar velocity profiles, implying they probe gas in the same or similar environments. The ionic ratios (e.g., N_CII_/N_CIII_, N_OI_/N_CII_) indicate that the gas in these absorbers is largely ionized, and the ionization conditions are quite comparable across the sampled N_HI_ range. The Doppler parameters of the HI imply T<~5x10^4^K on average, consistent with the gas being photoionized. The MgII column densities span >2 orders of magnitude at any given N_HI_, indicating a wide range of metallicities (from solar to <1/100 solar). In the range of 16.2<~logN_HI_<~17, there is a gap in the N_MgII_ distribution corresponding to gas with ~10% solar metallicity, consistent with the gap seen in the previously identified bimodal metallicity distribution in this column density regime. Less than 3% of the absorbers in our sample show no detectable metal absorption, implying that truly pristine gas at z<~1 is uncommon. We find <[FeII/MgII]>=-0.4+/-0.3, and since {alpha}-enhancement can affect this ratio, dust depletion is extremely mild.
860. The cosmic TeV gamma-ray background spectrum
ID:
ivo://CDS.VizieR/J/ApJ/818/187
Title:
The cosmic TeV gamma-ray background spectrum
Short Name:
J/ApJ/818/187
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Fermi gamma-ray space telescope has revolutionized our understanding of the cosmic gamma-ray background radiation in the GeV band. However, investigation on the cosmic TeV gamma-ray background radiation still remains sparse. Here, we report the lower bound on the cosmic TeV gamma-ray background spectrum placed by the cumulative flux of individual detected extragalactic TeV sources including blazars, radio galaxies, and starburst galaxies. The current limit on the cosmic TeV gamma-ray background above 0.1TeV is obtained as 2.8x10^-8^(E/100GeV)^-0.55^exp(-E/2100GeV)[GeV/cm2/s/sr] <E^2^dN/dE<1.1x10^-7^(E/100GeV)^-0.49^[GeV/cm2/s/sr], where the upper bound is set by requirement that the cascade flux from the cosmic TeV gamma-ray background radiation can not exceed the measured cosmic GeV gamma-ray background spectrum. Two nearby blazars, Mrk421 and Mrk501, explain ~70% of the cumulative background flux at 0.8-4TeV, while extreme blazars start to dominate at higher energies. We also provide the cumulative background flux from each population, i.e., blazars, radio galaxies, and starburst galaxies which will be the minimum requirement for their contribution to the cosmic TeV gamma-ray background radiation.