scholarly journals 20cm VLA radio-continuum study of M31: Images and point source catalogues

2012 ◽  
pp. 41-68 ◽  
Author(s):  
T.J. Galvin ◽  
M.D. Filipovic ◽  
E.J. Crawford ◽  
N.F.H. Tothill ◽  
G.F. Wong ◽  
...  
Keyword(s):  
High Resolution ◽  
Angular Resolution ◽  
High Sensitivity ◽  
Radio Continuum ◽  
High Angular Resolution ◽  
Radio Sources ◽  
Large Array ◽  
Complete Sample ◽  
Very Large Array ◽  
Discrete Radio Sources

We present a series of new high-sensitivity and high-resolution radio-continuum images of M31 at ?=20 cm (?=1.4 GHz). These new images were produced by merging archived 20 cm radio-continuum observations from the Very Large Array (VLA) telescope. Images presented here are sensitive to rms=60 ?Jy and feature high angular resolution (<10??). A complete sample of discrete radio sources have been catalogued and analyzed across 17 individual VLA projects. We identified a total of 864 unique discrete radio sources across the field of M31. One of the most prominent regions in M31 is the ring feature for which we estimated total integrated flux of 706 mJy at ?=20 cm. We compare here detected sources to those listed in Gelfand et al. (2004) at ?=92 cm and find 118 sources in common to both surveys. The majority (61%) of these sources exhibit a spectral index of ? <-0.6 indicating that their emission is predominantly non-thermal in nature, that is more typical for background objects.

scholarly journals Low frequency (74 MHz) radio continuum observations of the inner 13° × 7° of the Galactic center

2013 ◽  
Vol 9 (S303) ◽  
pp. 464-466
Author(s):  
M. Rickert ◽  
F. Yusef-Zadeh ◽  
C. Brogan
Keyword(s):  
High Resolution ◽  
Molecular Cloud ◽  
Supernova Remnant ◽  
Galactic Center ◽  
Low Frequency ◽  
Radio Continuum ◽  
Large Array ◽  
Very Large Array ◽  
Image Displays ◽  
Western Side

AbstractWe analyze a high resolution (114″ × 60″) 74 MHz image of the Galactic center taken with the Very Large Array (VLA). We have identified several absorption and emission features in this region, and we discuss preliminary results of two Galactic center sources: the Sgr D complex (G1.1–0.1) and the Galactic center lobe (GCL).The 74 MHz image displays the thermal and nonthermal components of Sgr D and we argue the Sgr D supernova remnant (SNR) is consistent with an interaction with a nearby molecular cloud and the location of the Sgr D Hii region on the near side of the Galactic center. The image also suggests that the emission from the eastern side of the GCL contains a mixture of both thermal and nonthermal sources, whereas the western side is primarily thermal.

scholarly journals A multifrequency study of the active star forming region NGC 6357

2006 ◽  
Vol 2 (S237) ◽  
pp. 400-400
Author(s):  
C. E. Cappa ◽  
R. H. Barbá ◽  
M. Arnal ◽  
N. Duronea ◽  
E. Fernández Lajús ◽  
...  
Keyword(s):  
Angular Resolution ◽  
Massive Stars ◽  
Radio Continuum ◽  
Large Array ◽  
Schmidt Telescope ◽  
Ionized Gas ◽  
Very Large Array ◽  
Active Star ◽  
Star Forming ◽  
Spiral Arm

To investigate the interaction of the massive stars with the gas and dust in the active star forming region NGC 6357, located in the Sagittarius spiral arm at a distance of 1.7-2.6 kpc (Massey et al. 2001), we analyzed the distribution of the neutral and ionized gas, and that of the dust, based on Hα, [OIII] and [SII] images obtained with the Curtis-Schmidt telescope at CTIO, radio continuum observations at 1.465 MHz obtained with the Very Large Array (NRAO) in the DnC configuration (synthesized beam = 38″), Hi data from the Parkes survey (angular resolution = 15′), CO(1-0) observations obtained with the Nanten radiotelescope at Las Campanas Observatory (angular resolution = 2.7′), and IR images in the four MSX bands (angular resolution = 18.3″).

scholarly journals Near-IR Solar Coronal Observations with New-Technology Reflecting Coronographs

1994 ◽  
Vol 154 ◽  
pp. 603-608
Author(s):  
Raymond N. Smartt ◽  
Serge Koutchmy ◽  
Jacques-Clair NoëNs
Keyword(s):  
High Resolution ◽  
Angular Resolution ◽  
High Sensitivity ◽  
Field Measurements ◽  
Coronal Magnetic Field ◽  
Photon Flux ◽  
Objective Lens ◽  
High Angular Resolution ◽  
Intrinsic Polarization ◽  
Near Ir

Emission-line and K-coronal observations in the IR have the significant advantage of reduced sky brightness compared with the visible, while the effects of seeing are also reduced. Moreover, strong lines are available in the near-IR. Examples of the current capabilities of IR coronal observations using conventional Lyot coronagraphs are discussed briefly. Photometric measurements using the two IR lines of Fe XIII (10,747 Å and 10,798 Å), together with the Fe XIII 3,388 Å line, have provided a valuable electron-density diagnostic, but with low-angular-resolution. The 10,747 Å line has high intrinsic polarization. It has been used for extensive coronal magnetic field measurements, but only the direction of the field, and that with modest angular resolution, has been achieved due basically to flux limitations. Such studies suffer from the lack of high angular resolution and high photon flux. Moreover, the chromatic properties of a singlet objective lens preclude simultaneous observations at widely-differing wavelengths of the important inner coronal region. A coronagraph based on a mirror objective avoids such problems. Further, comparatively high-resolution and high-sensitivity arrays are now available with quantum efficiencies up to 90%. Reflecting coronagraphs with advanced arrays then provide the possibility of obtaining high-resolution images in the infrared to carry out a wide variety of studies crucial to many of the outstanding problems in coronal physics. A program for the development of reflecting coronagraphs is described briefly, with an emphasis on applications to IR coronal studies.

scholarly journals A VLA Radio Continuum Survey of Planetary Nebulae

1989 ◽  
Vol 131 ◽  
pp. 60-60
Author(s):  
A. Zijlstra ◽  
S. R. Pottasch ◽  
C. Bignell
Keyword(s):  
High Resolution ◽  
Planetary Nebulae ◽  
Radio Continuum ◽  
Large Array ◽  
Very Large Array

With the Very Large Array it is now possible to make high resolution radio continuum maps with sensitivity less than a milliJansky in an observation of only 5 minutes. We have used this so-called snapshot capability to measure about 400 PN north of declination −35. Most of the measurements were carried out at 6 cm. Some of the stronger sources were observed at several frequencies. Most sources were detected, however many nebulae were too weak to map in detail. The resolution ranges from 1.5″ to 1′, depending on the size of the PN. The selected PN have sizes in the range from 4″ to 6′.

scholarly journals High Resolution & High Sensitivity Spectral-Line Imaging with Multiple Arrays

1994 ◽  
Vol 158 ◽  
pp. 334-336
Author(s):  
V. Migenes ◽  
J.A. Yates ◽  
R.J. Cohen ◽  
M.C. Shepherd ◽  
P.F. Bowers
Keyword(s):  
High Resolution ◽  
Spectral Line ◽  
Spectral Resolution ◽  
High Sensitivity ◽  
Large Array ◽  
Very Large Array ◽  
Line Imaging ◽  
Line Work ◽  
Low Sensitivity ◽  
The Uk

At present there are several radio interferometer arrays ranging from the low-resolution (0.1–1″) high-sensitivity arrays such as the Very Large Array (VLA) to the high-resolution (0.0005–0.1″) low-sensitivity arrays such as MERLIN (though MERLIN, in the UK, is really in between this broad category), EVN, VLBA and SHEVE. Combining high sensitvity and high resolution is prohibitively expensive, because to have the u–v sampling of small arrays would require more and larger antenna elements. Hence high- resolution arrays have poor u–v coverage, decreasing the sensitivity of the instrument. This has a serious effect on spectral-line work, where sensitivity has already been sacrificed in the pursuit of spectral resolution.

scholarly journals VLA observations of water maser emission associated with SVS 13

2002 ◽  
Vol 206 ◽  
pp. 59-62
Author(s):  
Luis F. Rodríguez ◽  
Guillem Anglada ◽  
José M. Torrelles ◽  
J. Eduardo Mendoza-Torres ◽  
Aubrey D. Haschick ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Radio Source ◽  
Angular Resolution ◽  
Radio Continuum ◽  
Large Array ◽  
Maser Emission ◽  
Very Large Array ◽  
Water Maser ◽  
East West ◽  
Made In

The young stellar object SVS 13 has been proposed as the powering source of the HH 7-11 objects. Recent observations have revealed that in the radio continuum (3.6-cm) the source is a binary separated by about 0.3 in the east-west direction. We present Very Large Array observations, made in the highest angular resolution A configuration, of H2O maser emission toward this source. Our data show that the H2O spots appear to be segregated in two velocity groups: a group with radial velocity similar to that of the ambient cloud (VLSR ⋍ 8 km s−1) that is associated with the western radio source, and a blueshifted (by ∼20 km s−1) velocity group that is associated with the eastern radio source. We discuss the possible implications of this observation.

AST Parameters and the AST Astrophysics Sub-Committee

1981 ◽  
Vol 4 (2) ◽  
pp. 160-163
Author(s):  
J. B. Whiteoak
Keyword(s):  
Angular Resolution ◽  
Science And Technology ◽  
Steering Committee ◽  
High Angular Resolution ◽  
Large Array ◽  
Design Study ◽  
Very Large Array ◽  
Study Committee ◽  
The Us ◽  
Critical Phase

There is no question that Australian radio astronomers are in urgent need of a telescope which can provide high angular resolution for both line and continuum projects. Planning for the Australian Synthesis Telescope (AST) began in 1975 (see Wellington 1976; Manchester 1977), and with the guidance of the AST Steering Committee and the Design Study Committee the instrument, although it may be overshadowed in some respects by the US Very Large Array (VLA), now has enough unique features to whet the scientific appetites of all Australian astronomers. The planning has reached a critical phase — a proposal, costed at $A17.3 million (in 1980), was submitted to the Minister for Science and technology in February 1981 for funding in the August 1981 budget.

scholarly journals VLA Observations of Orbital Motions in YLW 15

2004 ◽  
Vol 191 ◽  
pp. 137-138
Author(s):  
S. Curiel ◽  
J.M. Girart ◽  
L.F. Rodríguez ◽  
J. Cantó
Keyword(s):  
Binary System ◽  
Total Mass ◽  
Angular Resolution ◽  
High Angular Resolution ◽  
Large Array ◽  
Proper Motions ◽  
Very Large Array

AbstractUsing high angular resolution (~ 03) Very Large Array (VLA) observations made at 3.6 cm during the period 1990 to 2002, we report the detection of proper motions in the components of the binary source YLW 15. We find absolute proper motions of the order of 15 km s-1. In addition, the relative astrometry between the two components reveals orbital proper motions that suggest that the total mass of this binary system is ~ 1.7 M⊙, and that VLA 1 is more massive than VLA 2.

scholarly journals A Sino-German λ6 cm polarisation survey of the Galactic plane

2019 ◽  
Vol 623 ◽  
pp. A105 ◽  
Author(s):  
X. Y. Gao ◽  
P. Reich ◽  
L. G. Hou ◽  
W. Reich ◽  
J. L. Han
Keyword(s):  
Survey Data ◽  
Supernova Remnants ◽  
Large Scale ◽  
Angular Resolution ◽  
Galactic Plane ◽  
Thermal Emission ◽  
Small Diameter ◽  
Radio Continuum ◽  
High Angular Resolution ◽  
Radio Sources

Context. Large-scale radio continuum surveys provide data to get insights into the physical properties of radio sources. H II regions are prominent radio sources produced by thermal emission of ionised gas around young massive stars. Aims. We identify and analyse H II regions in the Sino-German λ6 cm polarisation survey of the Galactic plane. Methods. Objects with flat radio continuum spectra together with infrared and/or Hα emission were identified as H II regions. For H II regions with small apparent sizes, we cross-matched the λ6 cm small-diameter source catalogue with the radio H II region catalogue compiled by Paladini and the infrared H II region catalogue based on the WISE data. Effelsberg λ21 cm and λ11 cm continuum survey data were used to determine source spectra. High angular resolution data from the Canadian Galactic Plane Survey and the NRAO VLA Sky Survey were used to solve the confusion when low angular resolution observations were not sufficient. Extended H II regions were identified by eye by overlaying the Paladini and the WISE H II regions onto the λ6 cm survey images for coincidences. The TT-plot method was employed for spectral index verification. Results. A total of 401 H II regions were identified and their flux densities were determined with the Sino-German λ6 cm survey data. In the surveyed area, 76 pairs of sources are found to be duplicated in the Paladini H II region catalogue, mainly due to the non-distinction of previous observations with different angular resolutions and 78 objects in their catalogue are misclassified as H II regions, being actually planetary nebulae, supernova remnants, or extragalactic sources that have steep spectra. More than 30 H II regions and H II region candidates from our λ6 cm survey data, especially extended ones, do not have counterparts in the WISE H II region catalogue, of which 9 are identified for the first time. Our results imply that some more Galactic H II regions still await to be discovered and the combination of multi-domain observations is important for H II region identification. Based on the newly derived radio continuum spectra and the evidence of infrared emission, the previously identified SNRs G11.1−1.0, G20.4+0.1 and G16.4−0.5 are believed to be H II regions.

Bipolar outflow of gas in the spiral galaxy NGC 3079

1986 ◽  
Vol 64 (4) ◽  
pp. 531-535 ◽  
Author(s):  
Nebojsa Duric ◽  
E. R. Seaquist
Keyword(s):  
Spectral Index ◽  
Spiral Galaxy ◽  
Central Region ◽  
Qualitative Description ◽  
Radio Continuum ◽  
Large Array ◽  
Very Large Array ◽  
Bipolar Outflow ◽  
The Galaxy

Very large array, radio-continuum observations of the edge-on spiral galaxy NGC 3079 are presented. The observations reveal that the nucleus has windlike properties and that the central region of the galaxy exhibits an unusual figure-eight morphology that shows evidence of severe depolarization and a flattening spectral index away from the nucleus. A qualitative description of a model is presented to account for the observed radio properties. It is shown that a wind-driven shock propagating away from the nucleus and focused by the ambient disk gas can give rise to the observed morphology.

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