Radio studies of ionized hydrogen in the southern Milky Way
- Authors: Gaylard, Michael John
- Date: 1990
- Subjects: Interstellar hydrogen Milky Way Astrophysics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5440 , http://hdl.handle.net/10962/d1001993
- Description: This thesis describes the results of a survey of the HI42ɑ recombination line emission at 2.3 GHz from HII regions in the Southern Milky Way, carried out with the 26 m diameter Hartebeesthoek radio telescope. The Galactic Longitude range covered was 290° to 40°. Single recombination lines were detected from 375 positions. Multiple lines were observed towards 90 positions in the inner Galaxy. No line emission could be detected in 28 positions. Continuum antenna temperatures were estimated from drift scans or radio maps observed for the purpose. LTE electron temperatures and turbulent velocities of the HII regions were calculated where possible. The properties of the sample were compared to those observed in HI09ɑ surveys. The lines observed from over 50 positions were first detections, of which half were associated with optically-identified HII regions. In about 150 cases the lines were only the second to be detected from those HII regions. The processes of the radio emission, detection, and analysis were simulated numerically. The detectability of the emission and the magnitude of non-LTE effects and pressure-broadening in multi-component HII regions was predicted and compared to observations. The radio luminosity function of the HII regions was determined over a range of three orders of magnitude in intrinsic brightness for the first time, using techniques which corrected for different types of incompleteness in the samples. The luminosity function was compared to those in five selected spiral galaxies, and shown to lie between those of M33 and M81. An alternate form of the luminosity function was developed for use with a numerical model of the spiral arm structure of the Milky Way. The physical parameters defining the major spiral arms were established by comparing synthesized diagrams of radial velocity versus Galactic Longitude with those actually observed. The faint, extended HII regions S9 and RCW129 in Scorpius, the Barnard Loop in Orion, and S296 in Canis Major were analyzed, using all available data. All the recombination lines from these HII regions were first detections
- Full Text:
- Authors: Gaylard, Michael John
- Date: 1990
- Subjects: Interstellar hydrogen Milky Way Astrophysics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5440 , http://hdl.handle.net/10962/d1001993
- Description: This thesis describes the results of a survey of the HI42ɑ recombination line emission at 2.3 GHz from HII regions in the Southern Milky Way, carried out with the 26 m diameter Hartebeesthoek radio telescope. The Galactic Longitude range covered was 290° to 40°. Single recombination lines were detected from 375 positions. Multiple lines were observed towards 90 positions in the inner Galaxy. No line emission could be detected in 28 positions. Continuum antenna temperatures were estimated from drift scans or radio maps observed for the purpose. LTE electron temperatures and turbulent velocities of the HII regions were calculated where possible. The properties of the sample were compared to those observed in HI09ɑ surveys. The lines observed from over 50 positions were first detections, of which half were associated with optically-identified HII regions. In about 150 cases the lines were only the second to be detected from those HII regions. The processes of the radio emission, detection, and analysis were simulated numerically. The detectability of the emission and the magnitude of non-LTE effects and pressure-broadening in multi-component HII regions was predicted and compared to observations. The radio luminosity function of the HII regions was determined over a range of three orders of magnitude in intrinsic brightness for the first time, using techniques which corrected for different types of incompleteness in the samples. The luminosity function was compared to those in five selected spiral galaxies, and shown to lie between those of M33 and M81. An alternate form of the luminosity function was developed for use with a numerical model of the spiral arm structure of the Milky Way. The physical parameters defining the major spiral arms were established by comparing synthesized diagrams of radial velocity versus Galactic Longitude with those actually observed. The faint, extended HII regions S9 and RCW129 in Scorpius, the Barnard Loop in Orion, and S296 in Canis Major were analyzed, using all available data. All the recombination lines from these HII regions were first detections
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Calibration and interpretation of A 2.3 GHz continuum survey
- Authors: Greybe, Andrew
- Date: 1984
- Subjects: Radio astronomy , Astronomical observatories , Galaxies
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5502 , http://hdl.handle.net/10962/d1007210 , Radio astronomy , Astronomical observatories , Galaxies
- Description: This thesis continues the Rhodes 2.3 GHz Survey of the Southern Sky. It consists of two parts : a data processing part and an astronomical analysis part. In the data processing part the data for the regions 4HR to 15HR, -80° to -61° and 12HR to 23HR . -27° to -7° are presented in contour map format. A beam pattern of the Hartebeesthoek telescope at 13 cm is constructed from drift scans of the radio source TAU A. This is used to investigate the data filtering techniques applied to the Rhodes Survey. It is proposed that a set of widely spaced scans which have been referred to the South Celestial Pole can provide a single calibrated baselevel for the Rhodes Survey. The observing technique and the necessary reduction programs to create a coarse grid of antenna temperatures of the Southern Sky using these observation are developed. Preliminary results for this technique are presented as a map of the region 18HR to 6HR, 90° to 30° with a 5°x5° resolution. On the astronomical side two studies are undertaken. The region 13HR to 23HR, -61° to -7° is searched for large extended areas of emission. 7 features occurring at intermediate galactic latitudes are found. They are interpreted as follows: one of them is the classical HII region surrounding the star Zeta Ophiuchi (l",b")=(6.7°,22.4°), and the rest are combinations of thermal and nonthermal emission from galactic features. The galactic equator profile for 24°> L > -58° is studied. It is dominated by a plateau of emission for L < -26°. This is interpreted as a combination of thermal and nonthermal radiation emitted by a ring of gas symmetric about the galactic centre with a radius of 4 - 6 kpc.
- Full Text:
- Authors: Greybe, Andrew
- Date: 1984
- Subjects: Radio astronomy , Astronomical observatories , Galaxies
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5502 , http://hdl.handle.net/10962/d1007210 , Radio astronomy , Astronomical observatories , Galaxies
- Description: This thesis continues the Rhodes 2.3 GHz Survey of the Southern Sky. It consists of two parts : a data processing part and an astronomical analysis part. In the data processing part the data for the regions 4HR to 15HR, -80° to -61° and 12HR to 23HR . -27° to -7° are presented in contour map format. A beam pattern of the Hartebeesthoek telescope at 13 cm is constructed from drift scans of the radio source TAU A. This is used to investigate the data filtering techniques applied to the Rhodes Survey. It is proposed that a set of widely spaced scans which have been referred to the South Celestial Pole can provide a single calibrated baselevel for the Rhodes Survey. The observing technique and the necessary reduction programs to create a coarse grid of antenna temperatures of the Southern Sky using these observation are developed. Preliminary results for this technique are presented as a map of the region 18HR to 6HR, 90° to 30° with a 5°x5° resolution. On the astronomical side two studies are undertaken. The region 13HR to 23HR, -61° to -7° is searched for large extended areas of emission. 7 features occurring at intermediate galactic latitudes are found. They are interpreted as follows: one of them is the classical HII region surrounding the star Zeta Ophiuchi (l",b")=(6.7°,22.4°), and the rest are combinations of thermal and nonthermal emission from galactic features. The galactic equator profile for 24°> L > -58° is studied. It is dominated by a plateau of emission for L < -26°. This is interpreted as a combination of thermal and nonthermal radiation emitted by a ring of gas symmetric about the galactic centre with a radius of 4 - 6 kpc.
- Full Text:
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