scholarly journals Survey of OH Masers at 1665 and 1667 MHz. I. Galactic Longitudes 326° to 40°

1980 ◽  
Vol 33 (3) ◽  
pp. 639 ◽  
Author(s):  
JL Caswell ◽  
RF Haynes ◽  
WM Goss
Keyword(s):  
Supernova Remnants ◽  
Luminosity Function ◽  
Galactic Plane ◽  
Line Emission ◽  
Zeeman Splitting ◽  
State Transitions ◽  
Line Profiles ◽  
Polarization Data ◽  
Hii Region ◽  
Nonthermal Radio

The galactic plane between longitudes 3260 and 3400 has been searched for OH emiSSIOn and bsorption on the 1665 and 1667 MHz transitions. Forty main-line emission sources were detected (27 new ones, 13 previously known), and these constitute a sample complete to a weIl-defined lower intensity limit in this region of sky. Line profiles of all sources are shown and the statistics on variability and on the intensity ratios of the ground state transitions are summarized. The completeness of the sample encouraged us to make a first attempt to construct a luminosity function and to estimate the total number of such masers in our Galaxy. A study of the velocity structures showed these to be extremely varied, but none exceed a total range of 25 km s -1; combined velocity and polarization data are compatible with a Zeeman splitting origin for the circular polarization, and with this interpretation several sources yield an estimate for the line-of-sight magnetic field strength of a few mG. Preliminary investigations of the associations with other celestial objects indicate that many of the masers are loosely associated with HII region complexes, but in at least eight instances no HII regions have yet been detected; of these eight masers, two may be associated with supernova remnants and one with an unidentified nonthermal radio source.

scholarly journals Survey of OH Masers at 1665 MHz. II. Galactic Longitude 340o to the Galactic Centre

1983 ◽  
Vol 36 (3) ◽  
pp. 361 ◽  
Author(s):  
JL Caswell ◽  
RF Haynes
Keyword(s):  
Ground State ◽  
Galactic Plane ◽  
Line Emission ◽  
State Transitions ◽  
Galactic Centre ◽  
Emission Sources ◽  
Type I ◽  
Type Ii ◽  
Formation Type ◽  
Galactic Longitude

The galactic plane from longitude 340� through the galactic centre to longitude + 2� has been searched for OH on the 1665 MHz transition. Forty-nine OH maser emission sources were detected and these have now been studied on all four OH ground-state transitions. Most of the masers are associated with regions of star formation (type I) while three may be examples of late-type stars (type II OH/IR) with unusually strong main-line emission

scholarly journals Radio emission during the formation of stellar clusters in M 33

2020 ◽  
Vol 639 ◽  
pp. A27
Author(s):  
Edvige Corbelli ◽  
Jonathan Braine ◽  
Fatemeh S. Tabatabaei
Keyword(s):  
Radio Emission ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Supernova Remnants ◽  
Line Emission ◽  
Radio Continuum ◽  
Stellar Clusters ◽  
Nonthermal Radio ◽  
Early Formation ◽  
5 Ghz

Aims. We investigate thermal and nonthermal radio emission associated with the early formation and evolution phases of young stellar clusters (YSCs) selected by their mid-infrared (MIR) emission at 24 μm in M 33. We consider regions in their early formation period, which are compact and totally embedded in the molecular cloud, and in the more evolved and exposed phase. Methods. Thanks to recent radio continuum surveys between 1.4 and 6.3 GHz we are able to find radio source counterparts to more than 300 star forming regions of M 33. We identify the thermal free–free component for YSCs and their associated molecular complexes using the Hα line emission. Results. A cross-correlation of MIR and radio continuum is established from bright to very faint sources, with the MIR-to-radio emission ratio that shows a slow radial decline throughout the M 33 disk. We confirm the nature of candidate embedded sources by recovering the associated faint radio continuum luminosities. By selecting exposed YSCs with reliable Hα flux, we establish and discuss the tight relation between Hα and the total radio continuum at 5 GHz over four orders of magnitude. This holds for individual YSCs as well as for the giant molecular clouds hosting them, and allows us to calibrate the radio continuum–star formation rate relation at small scales. On average, about half of the radio emission at 5 GHz in YSCs is nonthermal with large scatter. For exposed but compact YSCs and their molecular clouds, the nonthermal radio continuum fraction increases with source brightness, while for large HII regions the nonthermal fraction is lower and shows no clear trend. This has been found for YSCs with and without identified supernova remnants and underlines the possible role of massive stars in triggering particle acceleration through winds and shocks: these particles diffuse throughout the native molecular cloud prior to cloud dispersal.

scholarly journals 6 cm Observations of Nonthermal Radio Sources Near the Galactic Plane

1969 ◽  
Vol 22 (5) ◽  
pp. 613 ◽  
Author(s):  
DK Milne
Keyword(s):  
Supernova Remnants ◽  
Galactic Plane ◽  
Brightness Distribution ◽  
Radio Sources ◽  
Nonthermal Radio

Brightness distributions and flux densities at 5000 MHz are presented for 17 nonthermal sources (possible supernova remnants) together with their spectra derived from these and other observations. For most sources a comparison has been made between the brightness distribution at 5000 MHz and that obtained with comparable resolution at 408 MHz with the Molonglo 1 mile Cross.

scholarly journals Unusually Wide, High-Velocity Radio Recombination Lines from G0.15–0.05 in the Radio Arc

1989 ◽  
Vol 136 ◽  
pp. 275-280 ◽  
Author(s):  
F. Yusef-Zadeh ◽  
Mark Morris ◽  
J. H. van Gorkom
Keyword(s):  
Radial Velocity ◽  
Galactic Center ◽  
Galactic Plane ◽  
Line Profiles ◽  
Recombination Line ◽  
Ionized Gas ◽  
Hii Region ◽  
Sgr A ◽  
Relativistic Particles ◽  
Kinematic Properties

The H92αrecombination line was observed at 8 GHz toward the “pistol-shaped” HII region G0.15–0.05 using the VLA2in its most compact configuration. The line profiles of individual components of this source peak at VLSR=123 km/s and have total line widths of ~90 km/s. The kinematical structure of the “pistol” is unusual in that much of the neutral and ionized gas in this region is seen predominantly at either +50 or +20 km/s. The line width and radial velocity are the largest found in the Galactic center region with the exception of Sgr A West. We also found gas at VLSR=140 km/s associated with G0.18–0.04: the sickle-shaped feature which surrounds G0.15–0.05. The kinematic properties of G0.18–0.04 and G0.15–0.05 suggest that these two features are components of a single, but complex thermal system interacting with the nonthermal filaments of the radio Arc. In this regard, the width of the broad recombination line from G0.15–0.05, and its large radial velocity, might be explained as the interaction of streaming relativistic particles in the nonthermal filaments of the Arc impacting upon ambient gas clouds lying in the Galactic plane.

scholarly journals Corrigendum: Classification of Supernova Remnants and HII Regions from their Recombination Line Emission

1973 ◽  
Vol 26 (2) ◽  
pp. 267 ◽  
Author(s):  
JR Dickel ◽  
DK Milne
Keyword(s):  
Supernova Remnants ◽  
Supernova Remnant ◽  
Line Emission ◽  
Hii Regions ◽  
Recombination Line ◽  
Hii Region ◽  
Galactic Source ◽  
Source Number

The galactic source number designations G35'6-0'4 and G35�5-0�0 in Table 1 should be interchanged. Thus G35'6-0'4 is the supernova remnant and G35�5 -0�0 appears to be an HII region. The authors thank Dr. T Velusamy for calling this error to their attention.

scholarly journals Supernova Remnants in Giant HII Regions

1988 ◽  
Vol 101 ◽  
pp. 201-204
Author(s):  
You-Hua Chu ◽  
Robert C. Kennicutt
Keyword(s):  
Supernova Remnants ◽  
Detection Rate ◽  
Massive Stars ◽  
Line Emission ◽  
Hii Regions ◽  
Radio Continuum ◽  
Hii Region ◽  
The Core ◽  
Large Numbers ◽  
Optical Line

Giant HII regions contain large numbers of massive stars, and hence are expected to contain large numbers of SNRs. Until recently, however, only a few SNRs have been identified in extragalactic giant HII regions. Moreover, most of these SNRs are located at the outskirts of HII regions, instead of the core where most of the stars are located. The low detection rate and the outlying locations of the SNRs may be due to: 1) observational difficulties - the background HII regions are much more luminous than the SNRs in both optical line emission and radio continuum; 2) intrinsic invisibility of SNRs - stellar wind and SNRs may have created a supershell (Mac Low and McCray 1987), and the core of a giant HII region is filled with hot tenuous coronal gas; or 3) a genuine deficiency of supernovae and SNRs in the HII regions (Sramek and Weedman 1986).

scholarly journals The H.E.S.S. Galactic Plane Survey

2009 ◽  
Vol 5 (H15) ◽  
pp. 808-808
Author(s):  
Emma de Oña-Wilhelmi
Keyword(s):  
Supernova Remnants ◽  
Binary Systems ◽  
Galactic Plane ◽  
Giant Molecular Clouds ◽  
Pulsar Wind Nebulae ◽  
Compact Binary ◽  
Pulsar Wind ◽  
Star Formation Regions ◽  
Galactic Sources ◽  
Gps Observations

AbstractThe H.E.S.S. Galactic Plane Survey (GPS) has revealed a large number of Galactic Sources, including Pulsar Wind Nebulae (PWN), Supernova Remnants (SNRs), giant molecular clouds, star formation regions and compact binary systems, as well as a number of unidentified objects, or dark sources, for which no obvious counterparts at other wavelengths have yet been found. We will review the latest results from the GPS observations and discuss the most interesting cases.

scholarly journals Modeling far-infrared line emission from the HII region S125

2003 ◽  
Vol 406 (1) ◽  
pp. 155-164 ◽  
Author(s):  
P. A. Aannestad ◽  
R. J. Emery
Keyword(s):  
Line Emission ◽  
Far Infrared ◽  
Hii Region

scholarly journals The Hα line emission of the Be star β Psc: the last 40 yr

2020 ◽  
Vol 501 (1) ◽  
pp. 747-755
Author(s):  
Ronaldo S Levenhagen ◽  
Marcos P Diaz ◽  
Eduardo B Amôres ◽  
Nelson V Leister
Keyword(s):  
Additional Data ◽  
State Of The Art ◽  
Spectral Energy Distribution ◽  
Line Emission ◽  
Spectral Energy ◽  
Line Profiles ◽  
Gas Density ◽  
Geometric Deformation ◽  
Be Star ◽  
Effects Of Rotation

ABSTRACT A study on the photosphere and disc of the Be star β Psc is presented. We recover almost 40 yr of high-resolution spectroscopic observations and additional data gathered from the BeSS data base. We evaluate the photospheric parameters from the spectral energy distribution (SED) and fittings of state-of-the-art non-LTE model atmospheres to observed helium, carbon, silicon, and magnesium line profiles. Our models include the stellar geometric deformation as well as the co-latitude dependence of temperature and gravity, aiming to derive the effects of rotation on the stellar parameters. We estimate the circumstellar disc parameters from the fitting of models assuming different disc properties, namely its radius and gas density profile. The disc inclination angle i is constrained from the fittings of He i 4471 Å, Mg ii 4481 Å, C ii 4267 Å,  and Si ii 4128, 4132 Å  lines with gravity darkened models. Our findings, based on model fittings, suggest that during the last 40 yr, the disc radius changed within the interval 5.5 ≤ Rd ≤ 7.8 $R/R_{*}\,$, the disc base gas density within 5 × 10−13 ≤ ρ ≤ 1 × 10−12 g cm−3, while the radial power-law density index m assumed values between 2.0 and 2.3. These results are in agreement with recent works dealing with spectroscopic and interferometric measurements of this object.

scholarly journals High-resolution studies of the galactic equator region

1964 ◽  
Vol 20 ◽  
pp. 81-85 ◽  
Author(s):  
F. J. Kerr
Keyword(s):  
Fine Structure ◽  
Line Emission ◽  
Paper Tape ◽  
Great Variability ◽  
Line Profiles ◽  
Sample Group ◽  
Large Program ◽  
Point To Point ◽  
Adjacent Channels ◽  
The University

A large program of observations is being undertaken with the 210-foot telescope at Parkes, to study the fine structure of the 21-cm line emission in the region of the galactic equator. With the aid of a multi-channel receiver, H-line profiles have been obtained every 6 min of arc (i.e. every half-beamwidth) along the equator from lII=300 to 60°, and also from bII = −3 to +3° along a number of constant-longitude lines. The bandwidth of each channel of the receiver is equivalent to 8 · 0 km/sec, with a spacing of 7 · 0 km/sec between the centres of adjacent channels. The data have been recorded on punched paper tape, and the main reduction is being carried out on the SILLIAC computer of the University of Sydney. A sample group of profiles, illustrating the great variability from point to point, has been published previously (Kerr 1962b).

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