- ID:
- ivo://CDS.VizieR/J/ApJ/900/125
- Title:
- Radio properties of Swift/BAT AGNs
- Short Name:
- J/ApJ/900/125
- Date:
- 02 Feb 2022 09:04:43
- Publisher:
- CDS
- Description:
- We address the very large diversity of jet production efficiency in active galactic nuclei (AGNs) by using data on low-redshift AGNs selected from the Swift/BAT catalog and having black hole (BH) masses larger than 10^8.5^M_{sun}_. Most of these AGNs accrete at intermediate rates and have bolometric luminosities dominated by mid-IR radiation. Our sample contains 14% radio-loud (RL), 6% radio-intermediate, and 80% radio-quiet (RQ) AGNs. All RL objects are found to have extended radio structures, and most of them have classical FR II morphology. Converting their radio loudness to jet production efficiency, we find that the median of this efficiency is on the order of ({epsilon}_d_/0.1)%, where {epsilon}_d_=L_bol_/(dM/dt)c^2^ is the radiation efficiency of the accretion disk. Without knowing the contribution of jets to the radio emission in RQ AGNs, we are only able to estimate their efficiencies using upper limits. Their median is found to be 0.002({epsilon}_d_/0.1)%. Our results suggest that some threshold conditions must be satisfied to allow the production of strong, relativistic jets in RL AGNs. We discuss several possible scenarios and argue that the production of collimated, relativistic jets must involve the Blandford-Znajek mechanism and can be activated only in those AGNs whose lifetime is longer than the time required to enter the magnetically arrested disk (MAD). Presuming that MAD is required to collimate relativistic jets, we expect that the weak nonrelativistic jets observed in some RQ AGNs are produced by accretion disks rather than by rotating BHs.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/466/921
- Title:
- Radio properties of z < 0.3 quasars
- Short Name:
- J/MNRAS/466/921
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To better constrain the hypotheses proposed to explain why only a few quasars are radio loud (R_L_), we compare the characteristics of 1958 nearby (z<=0.3) SDSS (Sloan Digital Sky Survey) quasars, covered by the FIRST (Faint Images of the Radio Sky at Twenty Centimeters) and NVSS (NRAO VLA Sky Survey) radio surveys. Only 22 per cent are R_L_ with log(L_1.4GHz_)>=22.5W/Hz, the majority being compact (C), weak radio sources (WRS), with log(L_1.4GHz_)<24.5W/Hz. 15 per cent of the RL quasars have extended radio morphologies: 3 per cent have a core and a jet (J), 2 per cent have a core with one lobe (L), and 10 per cent have a core with two lobes (T), the majority being powerful radio sources (PRS), with log(L_1.4GHz_)>=24.5W/Hz. In general, RL quasars have higher bolometric luminosities and ionization powers than radio-quiet (RQ) quasars. The WRS have comparable black hole (BH) masses as the RQ quasars, but higher accretion rates or radiative efficiencies. The PRS have higher BH masses than the WRS, but comparable accretion rates or radiative efficiencies. The WRS also have higher FWHM_{[OIII]} than the PRS, consistent with a coupling of the spectral characteristics of the quasars with their radio morphologies. Inspecting the SDSS images and applying a neighbour search algorithm reveal no difference between the RQ and RL quasars of their host galaxies, environments, and interaction. Our results prompt the conjecture that the phenomenon that sparks the RL phase in quasars is transient, intrinsic to the active galactic nuclei, and stochastic, due to the chaotic nature of the accretion process of matter on to the BHs.
- ID:
- ivo://CDS.VizieR/J/ApJS/165/338
- Title:
- Radio recombination lines in HII regions
- Short Name:
- J/ApJS/165/338
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report radio recombination line (RRL) and continuum observations of a sample of 106 Galactic HII regions made with the NRAO 140 Foot (43m) radio telescope in Green Bank, West Virginia. We believe this to be the most sensitive RRL survey ever made for a sample this large. Most of our source integration times range between 6 and 90 hr, yielding typical rms noise levels of ~1.0-3.5mK. Our data result from two different experiments performed, calibrated, and analyzed in similar ways. A CII survey was made at the 3.5cm wavelength to obtain accurate measurements of carbon radio recombination lines. When combined with atomic (CI) and molecular (CO) data, these measurements will constrain the composition, structure, kinematics, and physical properties of the photodissociation regions that lie on the edges of HII regions. A second survey was made at the 3.5cm wavelength to determine the abundance of ^3^He in the interstellar medium of the Milky Way. Together with measurements of the ^3^He^+^ hyperfine line, we get high-precision RRL parameters for H, ^4^He, and C. Here we discuss significant improvements in these data with both longer integrations and newly observed sources.
- ID:
- ivo://CDS.VizieR/J/A+A/171/261
- Title:
- Radio Recombination Lines of Southern HII Regions
- Short Name:
- J/A+A/171/261
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We tabulate velocities and other parameters of hydrogen recombination lines near 5GHz (H109{alpha} and H110{alpha}) for 316 HII regions observed with the Parkes 64-m radio telescope. Results of a new search for formaldehyde absorption are also listed. Source selection was based on the 5GHz continuum southern galactic plane survey of Haynes et al. (1978, 1979). Data is given for most H II regions in the galactic longitude range 210 to 360 degrees that show 5GHz continuum brightness temperature exceeding 1K (as observed with the 4 arcminute beam of the Parkes 64-m telescope), together with a selection of sources that are weaker or outside of this longitude range. Tabulated data include source coordinates, peak brightness, flux density, and angular size from the 5GHz continuum survey; radial velocities of detected formaldehyde absorption lines; recombination line peak brightness, radial velocity, and line width; derived electron temperature assuming LTE; derived kinematic distance from the Sun and galactocentric radius; and presence or absence of a visible optical counterpart. In cases where kinematic distance is ambiguous, both near and far distances are tabulated; a flag is given if there is a strong preference for near or far distance based on information such as H I or H2CO absorption measurements or visibility of an optical counterpart. Many of these radio HII regions lie beyond the range of optical detection, at distances exceeding several kpc; they thus provide a comprehensive coverage of the southern HII regions in the Galaxy over the longitude range 210 to 360 degrees and constitute a vital data base for the study of galactic structure.
1395. Radio reference frame
- ID:
- ivo://CDS.VizieR/J/AJ/110/880
- Title:
- Radio reference frame
- Short Name:
- J/AJ/110/880
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A catalogue is presented based on the radio positions of 436 extragalactic sources distributed over the entire sky. The positional accuracy of the sources is better than 3 milliarcsec (mas) in both coordinates, with the majority of the sources having errors better than 1mas. This catalogue is based upon a general solution of all applicable dual frequency 2.3 and 8.4GHz Mark-III VLBI data available through the end of 1993 consisting of 1,015,292 pairs of group delay and phase delay rate observations. Details and positions are also given for an additional 124 objects that either need further observation or are currently unsuitable for the definition of a reference frame. The final orientation of the catalogue has been obtained by a rotation of the positions into the system of the International Earth Rotation Service and is consistent with the FK5 J2000.0 optical system, within the limits of the link accuracy.
- ID:
- ivo://CDS.VizieR/J/ApJ/882/69
- Title:
- Radio relic merging galaxy cluster substructures
- Short Name:
- J/ApJ/882/69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Golovich et al. (2019, J/ApJS/240/39) present an optical imaging and spectroscopic survey of 29 radio relic merging galaxy clusters. In this paper, we study this survey to identify substructure and quantify the dynamics of the mergers. Using a combined photometric and spectroscopic approach, we identify the minimum number of substructures in each system to describe the galaxy populations and estimate the line-of-sight velocity difference between likely merging subclusters. We find that the line-of-sight velocity components of the mergers are typically small compared with the maximum 3D relative velocity (usually <1000km/s and often consistent with zero). We also compare our systems to n-body simulation analogs and estimate the viewing angle of the clean mergers in our ensemble. We find that the median system's separation vector lies within 40{deg} (17{deg}) at a 90% (50%) confidence level. This suggests that the merger axes of these systems are generally in or near the plane of the sky, matching findings in magnetohydrodynamical simulations. In 28 of the 29 systems we identify substructures in the galaxy population aligned with the radio relic(s) and presumed associated merger-induced shock. From this ensemble, we identify eight systems to include in a "gold" sample that is prime for further observation, modeling, and simulation study. Additional papers will present weak-lensing mass maps and dynamical modeling for each merging system, ultimately leading to new insight into a wide range of astrophysical phenomena at some of the largest scales in the universe.
- ID:
- ivo://CDS.VizieR/J/AJ/137/3869
- Title:
- Radio SNRs in 4 irregular galaxies
- Short Name:
- J/AJ/137/3869
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We survey four nearby irregular galaxies for radio supernova remnants (SNRs) using deep (1{sigma}~20uJy), high-resolution (~20pc) Very Large Array continuum data at 20, 6, and 3.6cm. We identify discrete sources in these galaxies and use radio spectral indices and H{alpha} images to categorize them as SNRs, HII regions, or background radio galaxies. Our classifications are generally in good agreement with the literature. We identify a total of 43 SNR candidates: 23 in NGC 1569, seven in NGC 4214, five in NGC 2366, and eight in NGC 4449. Only one SNR - the well-studied object J1228+441 in NGC 4449 - is more luminous at 20cm than Cas A. By comparing the total thermal flux density in each galaxy with that localized in HII regions, we conclude that a significant fraction must be in a diffuse component or in low-luminosity HII regions.
- ID:
- ivo://CDS.VizieR/J/ApJ/703/370
- Title:
- Radio SNRs in nearby galaxies
- Short Name:
- J/ApJ/703/370
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We compile radio supernova remnant (SNR) samples from the literature for 19 nearby galaxies ranging from the SMC to Arp 220, and use this data to constrain the SNR luminosity function (LF) at 20cm. We find that radio SNR populations are strikingly similar across galaxies. The LF can be described as a power law with constant index and scaling proportional to a galaxy's star formation rate (SFR). Unlike previous authors, we do not find any dependence of SNR luminosity on a galaxy's global interstellar medium density. The observed correlation between the luminosity of a galaxy's brightest SNR and a galaxy's SFR can be completely explained by statistical effects, wherein galaxies with higher SFR more thoroughly sample the high-luminosity end of the SNR LF. The LF is well fitted by a model of SNR synchrotron emission which includes diffusive shock acceleration and magnetic field amplification, if we assume that all remnants are undergoing adiabatic expansion, the densities of star-forming regions are similar across galaxies, and the efficiency of cosmic ray production is constant.
- ID:
- ivo://CDS.VizieR/J/A+A/506/1477
- Title:
- Radio source distribution
- Short Name:
- J/A+A/506/1477
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Information on physical characteristics of astrometric radio sources, such as magnitude and redshift, is of great importance for many astronomical studies. However, data usually used in radio astrometry is often incomplete and outdated. Our purpose is to study the optical characteristics of more than 4000 radio sources observed by the astrometric VLBI technique since 1979. We also studied the effect of the asymmetry in the distribution of the reference radio sources on the correlation matrices between vector spherical harmonics of the first and second degrees. The radio source characteristics were mainly taken from the NASA/IPAC Extragalactic Database (NED). Characteristics of the gravitational lenses were checked with the CfA-Arizona Space Telescope LEns Survey. SIMBAD and HyperLeda databases were also used to clarify the characteristics of some objects. Also we simulated and investigated a list of 4000 radio sources evenly distributed around the celestial sphere. We estimated the correlation matrices between the vector spherical harmonics using the real as well as modelled distribution of the radio sources.
- ID:
- ivo://CDS.VizieR/J/ApJS/13/65
- Title:
- Radio source flux densities at 750 & 1400MHz
- Short Name:
- J/ApJS/13/65
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Positions and flux densities at 750 and 1400MHz of 726 radio sources, measured with the 300-foot telescope, are given. Most of the positions are accurate to about +/-30" in each coordinate.