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Start Over Subject radio astronomy Content Level Research
1901. WMAP 3-yr sources at 16 and 33GHz
ID:
ivo://CDS.VizieR/J/MNRAS/400/984
Title:
WMAP 3-yr sources at 16 and 33GHz
Short Name:
J/MNRAS/400/984
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present follow-up observations of 97 point sources from the Wilkinson Microwave Anisotropy Probe (WMAP) 3-yr data, contained within the New Extragalactic WMAP Point Source catalogue between -4{deg}<=DE<=60{deg}; the sources form a flux-density-limited sample complete to 1.1Jy (~5{sigma}) at 33GHz. Our observations were made at 16GHz using the Arcminute Microkelvin Imager and at 33GHz with the Very Small Array (VSA).
1902. WMAP 3-yr sources at 16 and 33GHz. II.
ID:
ivo://CDS.VizieR/J/MNRAS/400/995
Title:
WMAP 3-yr sources at 16 and 33GHz. II.
Short Name:
J/MNRAS/400/995
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using the Arcminute Microkelvin Imager (AMI) at 16GHz and the Very Small Array (VSA) at 33GHz to make follow-up observations of sources in the New Extragalactic WMAP Point Source catalogue, we have investigated the flux density variability in a complete sample of 97 sources over time-scales of a few months to ~1.5yr.
1903. W43-MM1 ALMA ^12^CO(2-1) datacube
ID:
ivo://CDS.VizieR/J/A+A/636/A38
Title:
W43-MM1 ALMA ^12^CO(2-1) datacube
Short Name:
J/A+A/636/A38
Date:
21 Oct 2021
Publisher:
CDS
Description:
The accretion history of protostars remains widely mysterious even though it represents one of the best ways to understand the protostellar collapse that leads to the formation of stars. Molecular outflows, which are easier to detect than the direct accretion onto the prostellar embryo, are here used to characterize the protostellar accretion phase in W43-MM1. The W43-MM1 protocluster hosts a sufficient number of protostars to statistically investigate molecular outflows in a single, homogeneous region. We used the CO(2-1) and SiO(5-4) line datacubes, taken as part of an ALMA mosaic with a 2000 AU resolution, to search for protostellar outflows, evaluate the influence that the environment has on these outflows' characteristics and put constraints on outflow variability in W43-MM1. We discovered a rich cluster of 46 outflow lobes, driven by 27 protostars with masses of 1-100M_{sun}_. The complex environment inside which these outflow lobes develop has a definite influence on their length, limiting the validity of using outflow's dynamical timescales as a proxy of the ejection timescale in clouds with high dynamics and varying conditions. We performed a detailed study of Position-Velocity (PV) diagrams of outflows that revealed clear events of episodic ejection. The time variability of W43-MM1 outflows is a general trend and is more generally observed than in nearby, low- to intermediate-mass star-forming regions. The typical timescale found between two ejecta, ~500yr, is consistent with that found in nearby protostars. If ejection episodicity reflects variability in the accretion process, either protostellar accretion is more variable or episodicity is easier to detect in high-mass star-forming regions than in nearby clouds. The timescale found between accretion events could be resulting from instabilities, associated with bursts of inflowing gas arising from the close dynamical environment of highmass star-forming cores.
1904. W49N H2O maser outflow: distance and kinematics
ID:
ivo://CDS.VizieR/J/ApJ/393/149
Title:
W49N H2O maser outflow: distance and kinematics
Short Name:
J/ApJ/393/149
Date:
21 Oct 2021
Publisher:
CDS
Description:
Study of the motions of 105 H2O maser features clustered around a newly formed star in W49N yields the kinematics of the gas flow, the distance to the source, and the spatial scale of the Milky Way. We find that the maser outflow is bipolar, with an opening angle of ~60deg and an inclination of ~40deg to the line of sight. The expansion has a constant velocity of ~18 km/s out to a radius of 0.1pc, beyond which the outflow velocity increases to greater than 200 km/s. This increase may be due to interaction with ambient material. A rotation is also present; this rotation is nearly perpendicular to the outflow axis. The rotation may be due to ram pressure from ambient material; rotation of the ring of H II regions described by Welch et al. could produce such nonradial motion. Comparison of Doppler velocities and proper motions yields a distance of 11.4+/-1.2 kpc for the maser cluster. Combining this with a kinematic distance for W49N from Galactic rotation, we obtain a value of R0, the distance to the Galactic center, of 8.1+/-1.1 kpc.
1905. W49N H2O masers
ID:
ivo://CDS.VizieR/J/ApJ/429/253
Title:
W49N H2O masers
Short Name:
J/ApJ/429/253
Date:
21 Oct 2021
Publisher:
CDS
Description:
VLBI observations of a H2O maser were done at five epochs in 1980-82 with a 5 station VLBI network (see 1992ApJ...393..149G). A model was fitted to each peak in any spectral channel exceeding 5 times the rms background. The minimum level of this background, due to system noise at the antennas, was about 0.2Jy at each epoch. The model parameters include right ascension and declination offset (x, y) relative to a reference position; the total flux density, S; and the angular diameter {theta}_H_, of the best-fitting Gaussian distribution of intensity. The fitted parameters are in table1.
1906. W51 North ALMA 1.3 and 3mm images
ID:
ivo://CDS.VizieR/J/A+A/657/A30
Title:
W51 North ALMA 1.3 and 3mm images
Short Name:
J/A+A/657/A30
Date:
21 Mar 2022 09:31:18
Publisher:
CDS
Description:
The fragmentation process in massive star-forming regions is one of the contemporary problems in astrophysics, and several physical processes have been proposed to control the fragmentation including turbulence, magnetic field, rotation, stellar feedback, and gravity. However, the fragmentation process has been poorly studied at small spatial scales well below 1000AU. W51 IRS2 is a well known massive star-forming region whose fragmentation properties have not been well investigated yet. We aim to use ALMA (Atacama Large Millimeter and Submillimeter Array) high angular resolution data to identify the fragments in W51 IRS2 and to study the fragmentation properties on a spatial scale of 0.04" (200AU). We used ALMA data of W51 IRS2 from three projects, which give an angular resolution of 0.028" (144AU) at millimeter wavelengths. The continuum images reveal significant substructure in an east-west ridge, where both W51 North and W51d2 are embedded. A spectral index map has been generated from the 3 and 1.3mm high-resolution continuum images.We identified compact fragments by using uv-range constrained 1.3mm continuum data. A Mean Surface Density of Companions (MSDC) analysis has been performed to study the separations between fragments. A total number of 33 continuum sources are identified and 29 out of them are defined as fragments in the surveyed region.The MSDC analysis reveals two breaks corresponding to spatial sales of 1845AU and 7346AU, indicative of a two-level clustering phenomenon, along with a linear regime below 1845AU, mostly associated with W51 North, whose slope is consistent with the slope for the clustering regime of other cluster-like regions in the Galaxy. The typical masses and separations of the fragments as well as the relation between density and number of fragments can be explained through a thermal Jeans process operating at high temperatures of 200-400K, consistent with previous measurements of the temperature in the region, and produced by the nearby massive stars. Therefore, although W51 IRS2 seems to be undergoing a thermally inhibited fragmentation phase, this does not seem to prevent the formation of a protocluster associated with W51 North.
1907. W3(OH) high angular resolution 7mm images
ID:
ivo://CDS.VizieR/J/A+A/567/L5
Title:
W3(OH) high angular resolution 7mm images
Short Name:
J/A+A/567/L5
Date:
21 Oct 2021
Publisher:
CDS
Description:
Recent high angular resolution radio observations of the ultracompact Hii region W3(OH) confirm the presence of an extremely compact (0.05"), time-variable source near its center. We use new, sensitive high angular resolution observations of radio continuum and recombination lines to study the compact source in W3(OH) and the ultracompact HII region itself. We reduced and analyzed extensive Jansky Very Large Array observations of W3(OH) in the continuum at 41.0GHz and in the H54{alpha} and He54{alpha} lines.
1908. WR11 field at decimeter wavelengths
ID:
ivo://CDS.VizieR/J/A+A/625/A99
Title:
WR11 field at decimeter wavelengths
Short Name:
J/A+A/625/A99
Date:
21 Oct 2021
Publisher:
CDS
Description:
The massive binary system WR 11 ({gamma}^2^-Velorum) has recently been proposed as the counterpart of a Fermi source. If this association is correct, this system would be the second colliding wind binary detected in GeV {gamma}-rays. However, the reported flux measurements from 1.4 to 8.64 GHz fail to establish the presence of nonthermal (synchrotron) emission from this source. Moreover, WR 11 is not the only radio source within the Fermi detection box. Other possible counterparts have been identified in archival data, some of which present strong nonthermal radio emission. We conducted arcsec-resolution observations toward WR 11 at very low frequencies (150-1400 MHz) where the nonthermal emission - if existent and not absorbed - is expected to dominate. We present a catalog of more than 400 radio emitters, among which a significant portion are detected at more than one frequency, including limited spectral index information. Twenty-one of these radio emitters are located within the Fermi significant emission. A search for counterparts for this last group pointed at MOST 0808-471; this source is 2' away from WR 11 and is a promising candidate for high-energy emission, having a resolved structure along 325-1390 MHz. For this source, we reprocessed archive interferometric data up to 22.3 GHz and obtained a nonthermal radio spectral index of -0.97+/-0.09. However, multiwavelength observations of this source are required to establish its nature and to assess whether it can produce (part of) the observed {gamma}-rays. WR 11 spectrum follows a spectral index of 0.74+/-0.03 from 150 to 230 GHz, consistent with thermal emission. We interpret that any putative synchrotron radiation from the colliding-wind region of this relatively short-period system is absorbed in the photospheres of the individual components. Notwithstanding, the new radio data allowed us to derive a mass-loss rate of 2.5x10^-5^ M_{sun}_/yr, which, according to the latest models for {gamma}-ray emission in WR 11, would suffice to provide the required kinetic power to feed nonthermal radiation processes.
1909. WSRT survey of Cygnus OB2
ID:
ivo://CDS.VizieR/J/ApJS/149/123
Title:
WSRT survey of Cygnus OB2
Short Name:
J/ApJS/149/123
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a radio continuum survey at 1400 and 350 MHz of a region of 2{deg}x2{deg} centered on the Cygnus OB2 association (d=1.7kpc), using the Westerbork Synthesis Radio Telescope (WSRT) with angular resolutions of, respectively, 13" and 55". The resulting 5{sigma} flux-density limits of, respectively, ~2mJy and ~10-15mJy are a significant improvement over previous surveys. We detected 210 discrete sources with sizes less than 1.9{theta}beam (beam size), 98 of which at both frequencies. We also detected 28 resolved sources (sizes>1.9{theta}beam) still having well-defined peak intensities. The observed spectral index {alpha}^1400^_350_ distribution and source count strongly suggest an excess of sources of Galactic origin in the direction of Cyg OB2.
1910. WSRT ZoA Perseus-Pisces. HI catalogue
ID:
ivo://CDS.VizieR/J/MNRAS/460/923
Title:
WSRT ZoA Perseus-Pisces. HI catalogue
Short Name:
J/MNRAS/460/923
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results of a blind 21cm HI-line imaging survey of a galaxy overdensity located behind the Milky Way at l, b ~= 160{deg}, 0.5{deg}. The overdensity corresponds to a zone-of-avoidance crossing of the Perseus-Pisces Supercluster filament. Although it is known that this filament contains an X-ray galaxy cluster (3C 129) hosting two strong radio galaxies, little is known about galaxies associated with this potentially rich cluster because of the high Galactic dust extinction. We mapped a sky area of ~9.6 deg^2^ using the Westerbork Synthesis Radio Telescope in a hexagonal mosaic of 35 pointings observed for 12h each, in the radial velocity range cz=2400-16600km/s. The survey has a sensitivity of 0.36mJy/beam rms at a velocity resolution of 16.5km/s. We detected 211 galaxies, 62 per cent of which have a near-infrared counterpart in the UKIDSS Galactic Plane Survey. We present a catalogue of the HI properties and an HI atlas containing total intensity maps, position-velocity diagrams, global HI profiles and UKIDSS counterpart images. For the resolved galaxies we also present HI velocity fields and radial HI surface density profiles. A brief analysis of the structures outlined by these galaxies finds that 87 of them lie at the distance of the Perseus-Pisces Supercluster (cz~4000-8000km/s) and seem to form part of the 3C 129 cluster. Further 72 detections trace an overdensity at a velocity of cz~=10000km/s and seem to coincide with a structure predicted from mass density reconstructions in the first 2MASS Redshift Survey.