- ID:
- ivo://nasa.heasarc/wsrtgp
- Title:
- WSRT Galactic Plane Compact 327-MHz Source Catalog
- Short Name:
- WSRTGP
- Date:
- 14 Feb 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The Westerbork Synthesis Radio Telescope (WSRT) in the Netherlands has been used to survey the section of the galactic plane from +42 to +92 degrees Galactic Longitude l at a radio frequency of 327 MHz. Twenty-three overlapping synthesis fields were observed in the Galactic Latitude b band of |b| < 1.6 degrees. Each field was observed at two epochs, several years apart, to identify variable sources. Intensity data from the separate epochs were combined, and the resulting images mosaicked to produce a single image of the entire survey region. The sensitivity of the mosaic is typically a few mJy, corresponding to a detection level as low as 10 mJy/beam. The spatial resolution is 1' by 1' * cosec(Dec). The survey image provided the first high resolution view of the Galaxy at low radio frequencies, and included sections of the Sagittarius and Cygnus arms. These sections contain numerous extended features, among them supernova remnants, H II regions, "bubbles" of thermal emission, and large patches of amorphous galactic thermal emission. The inter-arm region is characterized by lower densities of extended features, but numerous discrete compact radio sources, most of which are background objects such as quasars and other types of active galactic nuclei. However, the resolution, sensitivity and low frequency of this survey make it ideal for detecting weak, non-thermal compact galactic sources, e.g. compact, low surface brightness SNRs and radio stars. Inspection of the survey image has produced a catalog of nearly 4000 discrete sources with sizes of less than about 3'. Gaussian model parameters for each compact source in the mosaicked images were obtained using the AIPS routine IMFIT. The background-removed intensity distribution of each source was fitted by a 2-dimensional Gaussian, parametrized by the source position, peak intensity, major and minor axes, and the position angle of the major axis. The catalog contains all sources having peak intensity > 5 times the rms noise level measured in the surrounding area of the image, and lists RA, Dec, flux density, and, if the source is resolved, the deconvolved major and minor axis and the position angle of the source. Sources were identified based on visual inspection of the images. In practice, a source had to have dimensions of less than a few arcminutes to be classified as a compact source. Most (85%) of the sources are either unresolved or only slightly resolved (major axis < 60"), but some sources have dimensions as large as 6'. A source was considered resolved if the area of its Gaussian model was greater than the area of the beam by more than 4 times its uncertainty. Approximately 15% of the sources are resolved, with dimensions of 1'- 3'. The spatial distribution of resolved sources shows concentrations toward the spiral arms and follows the warping of the Galactic disk over the length of the survey region, indicating that a sizable fraction is Galactic. In the reference paper, spectral indices are calculated for 1313 sources detected in other radio surveys at frequencies greater than 408 MHz. The resolved sources exhibit a bimodal spectral index distribution, with distinct non-thermal and thermal populations. Comparison with the IRAS Point Source Catalogue results in 118 identifications between WSRT and IRAS sources, which are listed in Table 1 of the reference paper. Most of these are thermal radio sources associated with compact Galactic objects such as H II regions and planetary nebulae. A search for variability among 2148 of the compact sources has resulted in 29 candidate low-frequency variable sources, which are listed in Table 2 of the reference paper. See the project website at <a href="http://www.ras.ucalgary.ca/wsrt_survey.html">http://www.ras.ucalgary.ca/wsrt_survey.html</a> for the WSRTGP images available in JPEG, PostScript, and FITS formats. This table was created by the HEASARC in February 2012 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJS/107/239">CDS Catalog J/ApJS/107/239</a> file wsrt.dat. This is a service provided by NASA HEASARC .
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/561/A28
- Title:
- WSRT HI data cubes of the dwarf galaxy UGCA 105
- Short Name:
- J/A+A/561/A28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Owing to their shallow stellar potential, dwarf galaxies possess thick gas disks, which makes them good candidates for studies of the galactic vertical kinematical structure. We present 21cm line observations of the isolated nearby dwarf irregular galaxy UGCA 105, taken with the Westerbork Synthesis Radio Telescope (WSRT), and analyse the geometry of its neutral hydrogen (HI) disk and its kinematics. The galaxy shows a fragmented HI distribution. It is more extended than the optical disk, and hence allows one to determine its kinematics out to very large galacto- centric distances. The HI kinematics and morphology are well-ordered and symmetric for an irregular galaxy. The HI is sufficiently extended to observe a substantial amount of differential rotation. Moreover, UGCA 105 shows strong signatures for the presence of a kinematically anomalous gas component. Performing tilted-ring modelling by use of the least-squares fitting routine TiRiFiC, we found that the HI disk of UGCA 105 has a moderately warped and diffuse outermost part. Probing a wide range of parameter combinations, we succeeded in modelling the data cube as a disk with a strong vertical gradient in rotation velocity (~-60km/s/kpc), as well as vertically increasing inwards motion (~-70km/s/kpc) within the radius of the stellar disk. The inferred radial gas inflow amounts to 0.06M_{sun}_/yr, which is similar to the star formation rate of the galaxy. The observed kinematics are hence compatible with direct or indirect accretion from the intergalactic medium, an extreme backflow of material that has formerly been expelled from the disk, or a combination of both.
23553. 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.
- ID:
- ivo://CDS.VizieR/J/A+A/527/A90
- Title:
- WSRT Virgo HI filament survey
- Short Name:
- J/A+A/527/A90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations of neutral hydrogen can provide a wealth of information about the kinematics of galaxies. To learn more about the large-scale structures and accretion processes, the extended environment of galaxies have to be observed. Numerical simulations predict a cosmic web of extended structures and gaseous filaments. To observe the direct vicinity of galaxies, column densities have to be achieved that probe the regime of Lyman limit systems. Typically, HI observations are limited to a brightness sensitivity of N_HI_~10^19^cm^-2^, but this has to be improved by ~2 orders of magnitude. With the Westerbork Synthesis Radio Telescope (WSRT), we mapped the galaxy filament connecting the Virgo Cluster with the Local Group. About 1500 square degrees on the sky was surveyed with Nyquist sampled pointings. By using the WSRT antennas as single-dish telescopes instead of the more conventional interferometer, we were very sensitive to extended emission. The survey consists of a total of 22000 pointings, and each pointing was observed for two minutes with 14 antennas.
- ID:
- ivo://CDS.VizieR/J/A+A/528/A28
- Title:
- WSRT Virgo HI filament survey. II.
- Short Name:
- J/A+A/528/A28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The extended environment of galaxies contains a wealth of information about the formation and life cycle of galaxies which are regulated by accretion and feedback processes. Observations of neutral hydrogen are routinely used to image the high brightness disks of galaxies and to study their kinematics. Deeper observations will give more insight into the distribution of diffuse gas in the extended halo of the galaxies and the inter-galactic medium, where numerical simulations predict a cosmic web of extended structures and gaseous filaments. To observe the extended environment of galaxies, column density sensitivities have to be achieved that probe the regime of Lyman limit systems. HI observations are typically limited to a brightness sensitivity of NHI~10^19^cm^-2^, but this must be improved upon by ~2 orders of magnitude.
- ID:
- ivo://CDS.VizieR/J/A+A/417/421
- Title:
- WSRT wide-field HI survey. II.
- Short Name:
- J/A+A/417/421
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used the Westerbork array to carry out an unbiased wide-field survey for HI emission features, achieving an RMS sensitivity of about 18mJy/Beam at a velocity resolution of 17km/s over 1800deg^2^ and between -1000<VHel<+6500km/s. The primary data consists of auto-correlation spectra with an effective angular resolution of 49' FWHM. The survey region is centered approximately on the position of Messier 31 and is Nyquist-sampled over 60x30deg in RAxDE. In this paper we present our HI detections at negative velocities which could be distinguished from the Galactic foreground. Fully 29% of the entire survey area has high velocity HI emission at a column density exceeding our 3-sigma limit of about 1.5x10^17cm^-2 over 30km/s. We tabulate the properties of 95 discrete HVC components in the field, corresponding to more than an order of magnitude increase in number over that known previously. The distribution of discrete object number with flux density has an inflection point near 12Jy.km/s which may correspond to a characteristic mass and distance for this population. A complete description of the observations and general methods of data reduction has already been given in Paper I (Braun et al., Cat. <J/A+A/406/829>).
- 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.
- ID:
- ivo://nasa.heasarc/w40sfrcxo
- Title:
- W 40 Star-Forming Region Chandra X-Ray Point Source Catalog
- Short Name:
- W40SFRCXO
- Date:
- 14 Feb 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The young stellar cluster illuminating the W40 H II region, one of the nearest massive star-forming regions (SFRs), has been observed with the ACIS detector on board the Chandra X-ray Observatory. Due to its high obscuration, this is a poorly studied stellar cluster with only a handful of bright stars visible in the optical band, including three OB stars identified as primary excitation sources. The authors detect 225 X-ray sources, of which 85% are confidently identified as young stellar members of the region. Two potential distances of the cluster, 260 pc and 600 pc, are used in the paper. Supposing the X-ray luminosity function of SFRs to be universal, it supports a 600 pc distance as a lower limit for W40 and a total population of at least 600 stars down to 0.1 M<sub>sun</sub> under the assumption of a coeval population with a uniform obscuration. In fact, there is strong spatial variation in K<sub>s</sub>-band-excess disk fraction and non-uniform obscuration due to a dust lane that is identified in absorption in optical, infrared, and X-ray. The dust lane is likely part of a ring of material which includes the molecular core within W40. In contrast to the likely ongoing star formation in the dust lane, the molecular core is inactive. The star cluster has a spherical morphology, an isothermal sphere density profile, and mass segregation down to 1.5 M<sub>sun</sub>. However, other cluster properties, including a <= 1 Myr age estimate and ongoing star formation, indicate that the cluster is not dynamically relaxed. X-ray diffuse emission and a powerful flare from a young stellar object are also reported in the reference paper. This table was created by the HEASARC in March 2011 based on electronic versions of Tables, 1, 2 and 4 of the reference paper which were obtained from the ApJ web site. This is a service provided by NASA HEASARC .
- ID:
- ivo://CDS.VizieR/J/A+AS/124/205
- Title:
- W3 star-forming region 345 GHz survey
- Short Name:
- J/A+AS/124/205
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results are presented of the 345 GHz spectral survey toward three sources in the W 3 Giant Molecular Cloud: W 3 IRS4, W 3 IRS5 and W 3(H_2_O). Nearly 90% of the atmospheric window between 334 and 365GHz has been scanned using the James Clerk Maxwell Telescope (JCMT) down to a noise level of ~80mK per resolution element. These observations are complemented by a large amount of data in the 230GHz atmospheric window. From this data set physical conditions and beam-averaged column densities are derived for more than 14 chemically different species (over 24 different isotopes). The physical parameters derived in Paper I (Helmich et al., 1994A&A...283..626H) are confirmed by the analysis of the excitation of other species, although there is evidence that the silicon- and sulfur-bearing molecules exist in a somewhat denser and warmer environment. The densities are high, >=10^6^cm^-3^, in the three sources and the kinetic temperatures for the bulk of the gas range from 55K for IRS4 to 220K for W 3(H_2_O). The chemical differences between the three sources are very striking: silicon- and sulfur-bearing molecules such as SiO and SO_2_ are prominent toward IRS5, whereas organic molecules like CH_3_OH, CH_3_OCH_3_ and CH_3_OCHO are at least an order of magnitude more abundant toward W 3(H_2_O). Vibrationally excited molecules are also detected toward this source. Only simple molecules are found toward IRS4. The data provide constraints on the amount of deuterium fractionation and the ionization fraction in the observed regions as well. These chemical characteristics are discussed in the context of an evolutionary sequence, in which IRS5 is the youngest, W 3(H_2_O) somewhat older and IRS4, although still enigmatic, the oldest.
- ID:
- ivo://CDS.VizieR/J/MNRAS/373/1483
- Title:
- W UMa type and CAB stars dynamical evolution
- Short Name:
- J/MNRAS/373/1483
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Orbital angular momentum (OAM, Jo), systemic mass (M) and orbital period (P) distributions of chromospherically active binaries (CAB) and W Ursae Majoris (W UMa) systems were investigated. The diagrams of and logJo-logP, logM-logP and logJo-logM were formed from 119 CAB and 102 W UMa stars. The log Jo-logM diagram is found to be most meaningful in demonstrating dynamical evolution of binary star orbits. A slightly curved borderline (contact border) separating the detached and the contact systems was discovered on the logJo-logM diagram. Since the orbital size (a) and period (P) of binaries are determined by their current Jo, M and mass ratio, q, the rates of OAM loss (dlogJo/dt) and mass loss (dlogM/dt) are primary parameters to determine the direction and the speed of the dynamical evolution. A detached system becomes a contact system if its own dynamical evolution enables it to pass the contact border on the logJo-logM diagram. The evolution of q for a mass-losing detached system is unknown unless the mass-loss rate for each component is known. Assuming q is constant in the first approximation and using the mean decreasing rates of Jo and M from the kinematical ages of CAB stars, it has been predicted that 11, 23 and 39 per cent of current CAB stars would transform to W UMa systems if their nuclear evolution permits them to live 2, 4 and 6Gyr, respectively.
