- ID:
- ivo://CDS.VizieR/J/ApJ/753/62
- Title:
- Kinematic distance ambiguity in HII regions
- Short Name:
- J/ApJ/753/62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using H I absorption spectra from the International Galactic Plane Survey, a new method is implemented to resolve the kinematic distance ambiguity for 75 H II regions with known systemic velocities from radio recombination lines. A further 40 kinematic distance determinations are made for H II region candidates without known systemic velocities through an investigation of the presence of H I absorption around the terminal velocity. New kinematic distance determinations can be used to further constrain spiral arm parameters and the location and extent of other structures in the Milky Way disk. H I absorption toward continuum sources beyond the solar circle is also investigated. Follow-up studies of H I at higher resolution than the 1' to 2' of existing Galactic Plane Surveys will provide kinematic distances to many more H II regions on the far side of the Galactic center. On the basis of the velocity channel summation technique developed in this paper, a much larger sample of H II regions will be analyzed in a future paper to remove the near-far distance ambiguity.
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- 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/A+A/327/1177
- Title:
- Kinematics and electron temperatures in Orion A
- Short Name:
- J/A+A/327/1177
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A map of the core of Orion A, with a 42" resolution in the 64{alpha} recombination line of hydrogen, covering ~5' by ~5', is presented. The V_lsr_ distribution shows a complex variation about the center of the ionized gas emission: From {DELTA}{alpha}=-200" to +300", the V_lsr_ varies from -5km/s to +2km/s then to -4km/s, finally rising to +3km/s. A search for cold (T_e_~3000K) ionized gas toward the KL nebula has revealed no measurable differences in T_e_ between this region and other parts of Orion A. The average T_e_ from our data is 8300+/-200K. We find no significant difference between T_e_ values determined from radio recombination lines and those determined from forbidden optical lines of [O III], although the T_e_ value from Balmer decrement data is markedly lower. The turbulent velocity varies by <5% over the region mapped. On the basis of our 2.45' resolution, high dynamic range 6cm continuum map, we find that the emission falls off faster in the East than in the West. We find support for the model in which Orion A is ionization bounded in the East but density bounded in the West. The ionized gas in the West is flowing in the direction of the Sun, while the more positive V_lsr_ values in the east may be caused by the flow of ionized gas off the foreground Dark Bay. This ionized region may have little fine scale structure, since there is little continuum emission in interferometer maps.
- 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/MNRAS/355/20
- Title:
- K magnitudes of 74MHz radio sources
- Short Name:
- J/MNRAS/355/20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we present near-infrared K-band imaging of a sample of ultra-steep-spectrum (USS) radio sources selected at 74-MHz. The dual selection criteria of low frequency and USS mean that we should be sensitive to the highest-redshift (z>5) radio galaxies. We have obtained K-band magnitudes for all of the objects in our sample of 26 and discuss the properties of each.
- 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/MNRAS/426/2107
- Title:
- KNoWS pilot bright sample
- Short Name:
- J/MNRAS/426/2107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- During 2010-11, the Medicina 32-m dish hosted the seven-feed 18-26.5GHz receiver built for the Sardinia Radio Telescope, with the goal to perform its commissioning. This opportunity was exploited to carry out a pilot survey at 20GHz over the area for {delta}>+72.3{deg}. This paper describes all the phases of the observations, as they were performed using new hardware and software facilities. The map-making and source extraction procedures are illustrated. A customized data reduction tool was used during the follow-up phase, which produced a list of 73 confirmed sources down to a flux density of 115mJy. The resulting catalogue, presented here, is complete above 200mJy. Source counts are in agreement with those provided by the Australia Telescope 20GHz (AT20G) survey. This pilot activity paves the way for a larger project, the K-band Northern Wide Survey (KNoWS), whose final aim is to survey the whole Northern hemisphere down to a flux limit of 50mJy (5{sigma}).
- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/601/A80
- Title:
- LABOCA 345GHz observations of Sgr A*
- Short Name:
- J/A+A/601/A80
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on a statistical analysis of the 345GHz submillimeter (submm) and 100GHz radio flux density distribution of Sagittarius A* (Sgr A*). The submm data set consists of 345GHz data obtained from different Large Apex Bolometer Camera (LABOCA) campaigns between 2008 and 2014, and additional literature data from 2004 to 2009 at comparable wavelengths. The radio observations were carried out with the Australia Telescope Compact Array (ATCA) between 2010 and 2014. We used a combined maximum likelihood estimator (MLE) and Kolmogorov-Smirnov (KS) statistics method to test for a possible power-law distribution in the high flux density excursions (flares) at both wavebands. We find that both flux density distributions can be described by a shifted power-law of the form p(x){prop.to}(x-S)^-{alpha}^ with {alpha}~4 (submm: {alpha}=4.0+/-1.7, radio: {alpha}=4.7+/-0.8). The same power-law index was previously found for the near-infrared (NIR) flux density distribution. These results may strengthen our preferred flare emission model: a combined synchrotron self-Compton (SSC) and adiabatically expanding self-absorbed synchrotron blob model where the flaring activity across all wavebands stem from the same source components and the variable emission can be described by a single state red noise process. Within the framework of the expanding blob model the similarity of the radio and the submm flux density distribution may also narrow down possible initial synchrotron turnover {nu}_0_ to be mainly around 350GHz and possible expansion velocities v_exp_ to be predominantly around 0.01c.
- ID:
- ivo://svo.laeff/laeff
- Title:
- Laboratorio de Astrofisica Espacial y Fisica Fundemental
- Short Name:
- LAEFF
- Date:
- 04 Apr 2008 11:10:03
- Publisher:
- INTA/LAEFF
- Description:
- LAEFF (Laboratory for Space Astrophysics and Theoretical Physics) was founded in 1991 as a collaboration between INTA, CSIC and ESA, and was located at VILSPA to allow for closer interaction with the ESA astronomical activities (IUE, ISO, XMM,...). Research at LAEFF is carried out in different areas of astrophysics, as astroparticle physics, interstellar medium, brown dwarfs and solar, stellar and extragalactic physics. LAEFF is also responsible for the radio astronomical use of the antennas in the Robledo de Chavela station. LAEFF participates in the development of diferent space projects such as OMC-INTEGRAL, EURD, LEGRI and EDDINGTON. LAEFF is also involved in the development and maintenance of Astronomical Data Archives of space missions (INES, OMC) and ground-based telescopes (GAUDI) in the framework of the Virtual Observatory project.