- ID:
- ivo://CDS.VizieR/J/A+A/649/A113
- Title:
- ISOSS22478 and ISOSS23053 images
- Short Name:
- J/A+A/649/A113
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The formation of high-mass star-forming regions from their parental gas cloud and the subsequent fragmentation processes lie at the heart of star formation research. We aim to study the dynamical and fragmentation properties at very early evolutionary stages of high-mass star formation. Employing the NOrthern Extended Millimeter Array (NOEMA) and the IRAM 30m telescope, we observe two young high-mass star-forming regions, ISOSS22478 and ISOSS23053, in the 1.3mm continuum and spectral line emission at high angular resolution (~0.8''). Resolving altogether 29 cores that are largely located along filament-like structures, we find that these cores follow a mass-size relation of approximately M~r^3^, corresponding to a constant mean density of roughly 10^6cm^-3^. The correlation of the core masses with their nearest neighbor separations is consistent with thermal Jeans fragmentation. Although the kinematics of the two regions appear very different at first sight -- multiple velocity components along filaments in ISOSS22478 versus a steep velocity gradient of more than 50km/s/pc in ISOSS23053 -- the findings can all be explained in the framework of a dynamical cloud collapse scenario. While our data are consistent with a dynamical cloud collapse scenario and subsequent thermal Jeans fragmentation, the importance of additional environmental properties -- e.g., the magnetization of the gas or external shocks triggering converging gas flows -- is still less well constrained and requires future investigation.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/846/98
- Title:
- Jet kinematics of blazars at 43GHz with the VLBA
- Short Name:
- J/ApJ/846/98
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the parsec-scale jet kinematics from 2007 June to 2013 January of a sample of {gamma}-ray bright blazars monitored roughly monthly with the Very Long Baseline Array at 43GHz. In a total of 1929 images, we measure apparent speeds of 252 emission knots in 21 quasars, 12 BL Lacertae objects (BLLacs), and 3 radio galaxies, ranging from 0.02c to 78c; 21% of the knots are quasi-stationary. Approximately one-third of the moving knots execute non-ballistic motions, with the quasars exhibiting acceleration along the jet within 5pc (projected) of the core, and knots in BLLacs tending to decelerate near the core. Using the apparent speeds of the components and the timescales of variability from their light curves, we derive the physical parameters of 120 superluminal knots, including variability Doppler factors, Lorentz factors, and viewing angles. We estimate the half-opening angle of each jet based on the projected opening angle and scatter of intrinsic viewing angles of knots. We determine characteristic values of the physical parameters for each jet and active galactic nucleus class based on the range of values obtained for individual features. We calculate the intrinsic brightness temperatures of the cores, T_b,int_^core^, at all epochs, finding that the radio galaxies usually maintain equipartition conditions in the cores, while ~30% of T_b,int_^core^ measurements in the quasars and BLLacs deviate from equipartition values by a factor >10. This probably occurs during transient events connected with active states.
- ID:
- ivo://CDS.VizieR/J/A+AS/101/513
- Title:
- JHKLM photometry of C stars
- Short Name:
- J/A+AS/101/513
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present J H K L M photometry for 25 Carbon stars, and 450, 600, 800 and 1100 {mu}m for 12 carbon stars and the S-star W Aql. Carbon stars reside on a different part of the [12-25], [K-L] diagram than O-rich stars. Our work confirms earlier observations and shows this relation to hold up at least [K-L] ~ 8mag.
- ID:
- ivo://CDS.VizieR/J/ApJ/871/215
- Title:
- JVLA rotation measures of Smith cloud bckg sources
- Short Name:
- J/ApJ/871/215
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Smith Cloud is a high-velocity cloud with an orbit suggesting it has made at least one passage through the Milky Way disk. A magnetic field found around this cloud has been thought to provide extra stability as it passes through the Galactic halo. We use the Karl G. Jansky Very Large Array to measure Faraday rotation measures (RMs) toward 1105 extragalactic background point sources behind and next to the Smith Cloud to constrain the detailed geometry and strength of its magnetic field. The RM pattern across the cloud gives the detailed morphology of the magnetic field structure, which indicates a field draped over the ionized gas and compressed at the head of the cloud. We constrain the peak line-of-sight magnetic field strength to >~+5{mu}G and create a model of the magnetic field to demonstrate that a draped configuration can qualitatively explain the morphology of the observed RMs.
- ID:
- ivo://CDS.VizieR/J/ApJ/810/L9
- Title:
- 1.5Jy MOJAVE AGN sample and 3FGL data
- Short Name:
- J/ApJ/810/L9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use the complete MOJAVE 1.5Jy sample of active galactic nuclei (AGNs) to examine the gamma-ray detection statistics of the brightest radio-loud blazars in the northern sky. We find that 23% of these AGNs were not detected above 0.1GeV by the Fermi-LAT during the four-year 3FGL catalog period partly because of an instrumental selection effect and partly due to their lower Doppler boosting factors. Blazars with synchrotron peaks in their spectral energy distributions located below 10^13.4^Hz also tend to have high-energy peaks that lie below the 0.1GeV threshold of the LAT, and are thus less likely to be detected by Fermi. The non-detected AGNs in the 1.5Jy sample also have significantly lower 15GHz radio modulation indices and apparent jet speeds, indicating that they have lower than average Doppler factors. Since the effective amount of relativistic Doppler boosting is enhanced in gamma-rays (particularly in the case of external inverse-Compton scattering), this makes them less likely to appear in the 3FGL catalog. Based on their observed properties, we have identified several bright radio-selected blazars that are strong candidates for future detection by Fermi.
- ID:
- ivo://CDS.VizieR/J/AJ/158/31
- Title:
- Kepler K2 mission fields 3-5: radio continuum survey
- Short Name:
- J/AJ/158/31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Murchison Widefield Array (MWA) monitoring of the Kepler K2 mission fields 3, 4, and 5 at frequencies of 155 and 186 MHz, from observations contemporaneous with the K2 observations. This work follows from previous MWA and Giant Metrewave Radio Telescope (GMRT) surveys of field 1, with the current work benefiting from a range of improvements in the data processing and analysis. We continue to build a body of systematic low-frequency blind surveys overlapping with transient/variable survey fields at other wavelengths, providing multiwavelength data for object classes such as flare stars. From the current work, we detect no variable objects at a surface density above 2x10^-4^ per square degree, at flux densities of ~500 mJy, and an observation cadence of days to weeks, representing almost an order of magnitude decrease in the measured upper limits compared to previous results in this part of observational parameter space. This continues to show that radio transients at meter and centimeter wavelengths are rare.
- ID:
- ivo://CDS.VizieR/J/ApJ/699/1153
- Title:
- Kinematic distances to GRS molecular clouds
- Short Name:
- J/ApJ/699/1153
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Kinematic distances to 750 molecular clouds identified in the ^13^COJ=1-0 Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey (GRS) are derived assuming the Clemens rotation curve of the Galaxy. The kinematic distance ambiguity is resolved by examining the presence of HI self-absorption toward the ^13^CO emission peak of each cloud using the Very Large Array Galactic Plane Survey. We also identify 21cm continuum sources embedded in the GRS clouds in order to use absorption features in the HI 21cm continuum to distinguish between near and far kinematic distances. The Galactic distribution of GRS clouds is consistent with a four-arm model of the Milky Way. The locations of the Scutum-Crux and Perseus arms traced by GRS clouds match star-count data from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire star-count data. We conclude that molecular clouds must form in spiral arms and be short-lived (lifetimes <10^7^yr) in order to explain the absence of massive, ^13^CO bright molecular clouds in the interarm space.
- ID:
- ivo://CDS.VizieR/J/ApJ/609/539
- Title:
- Kinematics of parsec-scale radio jets
- Short Name:
- J/ApJ/609/539
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of a 15GHz (2cm) multi-epoch Very Long Baseline Array (VLBA) program, begun in 1994 to study the outflow in radio jets ejected from quasars and active galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/829/119
- Title:
- Known pulsars identified in the TGSS ADR
- Short Name:
- J/ApJ/829/119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used the 150MHz radio continuum survey (TGSS ADR) from the Giant Metrewave Radio Telescope (GMRT) to search for phase-averaged emission toward all well-localized radio pulsars north of -53{deg} decl. We detect emission toward 200 pulsars with high confidence (>=5{sigma}) and another 88 pulsars at fainter levels. We show that most of our identifications are likely from pulsars, except for a small number where the measured flux density is confused by an associated supernova or pulsar-wind nebula, or a globular cluster. We investigate the radio properties of the 150MHz sample and find an unusually high number of gamma-ray binary millisecond pulsars with very steep spectral indices. We also note a discrepancy in the measured flux densities between GMRT and LOFAR pulsar samples, suggesting that the flux density scale for the LOFAR pulsar sample may be in error by approximately a factor of two. We carry out a separate search of 30 well-localized gamma-ray, radio-quiet pulsars in an effort to detect a widening of the radio beam into the line of sight at lower frequencies. No steep-spectrum emission was detected either toward individual pulsars or in a weighted stack of all 30 images.
- ID:
- ivo://CDS.VizieR/J/ApJS/228/22
- Title:
- Korean VLBI Network Calibrator Survey (KVNCS). I.
- Short Name:
- J/ApJS/228/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the catalog of the KVN Calibrator Survey (KVNCS). This first part of the KVNCS is a single-dish radio survey simultaneously conducted at 22 (K band) and 43GHz (Q band) using the Korean VLBI Network (KVN) from 2009 to 2011. A total of 2045 sources are selected from the VLBA Calibrator Survey with an extrapolated flux density limit of 100mJy at the K band. The KVNCS contains 1533 sources in the K band with a flux density limit of 70mJy and 553 sources in the Q band with a flux density limit of 120mJy; it covers the whole sky down to -32.5{deg} in decl. We detected 513 sources simultaneously in the K and Q bands; ~76% of them are flat-spectrum sources (-0.5<={alpha}<=0.5). From the flux-flux relationship, we anticipated that most of the radiation of many of the sources comes from the compact components. The sources listed in the KVNCS therefore are strong candidates for high-frequency VLBI calibrators.
