scholarly journals Marseille Observatory Hα Survey of the Southern Galactic Plane and Magellanic Clouds

1998 ◽  
Vol 15 (1) ◽  
pp. 9-13 ◽  
Author(s):  
D. Russeil ◽  
Y. M. Georgelin ◽  
P. Amram ◽  
Y. P. Georgelin ◽  
A. Laval ◽  
...  
Keyword(s):  
Spiral Structure ◽  
Galactic Plane ◽  
Hii Regions ◽  
Magellanic Clouds ◽  
Spectral Information ◽  
Fourth Quadrant ◽  
Diffuse Emission ◽  
Gas Kinematics ◽  
Fabry Perot

AbstractThe ionised gas regions, which are the main tracers of the spiral arms, can be used for the study and determination of the spiral structure of our Galaxy. Towards this goal, the Marseille Observatory elaborated and developed an instrument, using a scanning Fabry–Perot interferometer, particularly suited for the observation of extended objects. A survey of the southern Galactic plane then started at the beginning of 1990. The major instrumental aim is to obtain spectral information, and therefore the ionised gas kinematics, in each pixel of the observed fields. Already 300 fields of 38′×38′ have been observed in Hα with a spatial resolution of 9″×9″, covering almost the entire fourth quadrant of the Galactic plane, and numerous discrete HII regions have been detected, as well as diffuse emission which is widely distributed. Also, the Magellanic Clouds have been studied using the same instrument.

scholarly journals Observational Aspects of Supernova Remnants

1974 ◽  
Vol 60 ◽  
pp. 311-327 ◽  
Author(s):  
B. Y. Mills
Keyword(s):  
Radio Source ◽  
Supernova Remnants ◽  
Galactic Plane ◽  
Great Majority ◽  
Magellanic Clouds ◽  
X Ray ◽  
Yield Information ◽  
Show Evidence ◽  
Good Determination

A supernova event may lead to four observable features: a pulsar, an expanding nebulosity, a radio source and an X-ray source. The great majority of supernovae do not produce observable pulsars, and discussion is restricted largely to the other features. An increasing number of X-ray sources is now being detected and the structure and spectrum of the stronger sources investigated; these observations yield information about the physical state of the remnant. Recently, 11 new optical and radio remnants have been found in the Magellanic Clouds. These have led to a good determination of the Σ – D relation, thus providing a more reliable distance scale for galactic SNR, but have also shown that a one-to-one correspondence between a radio source and a supernova event is questionable. When these remnants are combined with corrected earlier catalogues and a new southern catalogue containing a high proportion of distant old remnants the number of known SNR is about 150. The evolution of galactic SNR may be investigated empirically, and although the derived rate of occurrence is very uncertain a rate of about 2 supernovae per century is consistent with most determinations. The galactic SNR are distributed rather like the radio disc emission, but more closely confined to the galactic plane, and selected SNR show evidence of a spiral pattern.

scholarly journals Hα Survey of the Milky Way and Magellanic Clouds

1994 ◽  
Vol 161 ◽  
pp. 503-507
Author(s):  
M. Marcelin ◽  
P. Amram ◽  
J. Boulesteix ◽  
Y.M. Georgelin ◽  
Y.P. Georgelin ◽  
...  
Keyword(s):  
Milky Way ◽  
Spiral Structure ◽  
Hii Regions ◽  
Magellanic Clouds

In 1990 we began an Ha survey of the Milky Way and the Magellanic clouds at ESO La Silla with a 36 cm telescope. The main goal of this survey is to study in detail complexes of HII regions, as well as the global spiral structure of our Galaxy.

scholarly journals Kinematic Study of the Northwestern Part of the Bar of the LMC

1999 ◽  
Vol 190 ◽  
pp. 152-153
Author(s):  
P. Ambrocio-Cruz ◽  
A. Laval ◽  
M. Marcelin ◽  
P. Amram
Keyword(s):  
Hii Regions ◽  
Magellanic Clouds ◽  
Northwestern Part ◽  
Ionized Gas ◽  
European Southern Observatory ◽  
Kinematic Study ◽  
Fabry Perot

We have been conducting a Fabry-Perot kinematic survey of ionized gas in the Magellanic Clouds in the Hα and [O III]λ5007 lines, using a 36-cm telescope at the European Southern Observatory. This poster presents our kinematic study of HII regions located at the northwestern parts of the LMC bar.

scholarly journals Determination of Galactic spiral structure at radiofrequencies

1985 ◽  
Vol 106 ◽  
pp. 283-300 ◽  
Author(s):  
H. S. Liszt
Keyword(s):  
Spiral Structure ◽  
Hii Regions ◽  
Galactic Structure ◽  
Spiral Pattern ◽  
Galactic Spiral Structure ◽  
Galactic Spiral ◽  
Adequate Method

We consider some results of attempts to trace the pattern of galactic spiral structure in HII regions, HI, and CO. There is really no adequate method available for solving this problem, a fact reflected in the lack of consensus regarding the “correct” spiral pattern. The newly-begun process of deriving galactic structure in CO seems to be recapitulating the history laid down by HI observers.

scholarly journals Modelling the Galactic very-high-energy γ-ray source population

2020 ◽  
Vol 643 ◽  
pp. A137
Author(s):  
Constantin Steppa ◽  
Kathrin Egberts
Keyword(s):  
Large Scale ◽  
Spiral Structure ◽  
Galactic Plane ◽  
High Energy ◽  
Source Distribution ◽  
Source Population ◽  
Diffuse Emission ◽  
Data Set ◽  
Very High Energy ◽  
Very High

Context. The High Energy Stereoscopic System Galactic plane survey (HGPS) is to date the most comprehensive census of Galactic γ-ray sources at very high energies (VHE; 100 GeV ≤ E ≤ 100 TeV). As a consequence of the limited sensitivity of this survey, the 78 detected γ-ray sources comprise only a small and biased subsample of the overall population. The larger part consists of currently unresolved sources, which contribute to large-scale diffuse emission to a still uncertain amount. Aims. We study the VHE γ-ray source population in the Milky Way. For this purpose population-synthesis models are derived based on the distributions of source positions, extents, and luminosities. Methods. Several azimuth-symmetric and spiral-arm models are compared for spatial source distribution. The luminosity and radius function of the population are derived from the source properties of the HGPS data set and are corrected for the sensitivity bias of the HGPS. Based on these models, VHE source populations are simulated and the subsets of sources detectable according to the HGPS are compared with HGPS sources. Results. The power-law indices of luminosity and radius functions are determined to range between −1.6 and −1.9 for luminosity and −1.1 and −1.6 for radius. A two-arm spiral structure with central bar is discarded as spatial distribution of VHE sources, while azimuth-symmetric distributions and a distribution following a four-arm spiral structure without bar describe the HGPS data reasonably well. The total number of Galactic VHE sources is predicted to be in the range from 800 to 7000 with a total luminosity and flux of (1.6 − 6.3) × 1036 ph s−1 and (3 − 15) × 10−10 ph cm−2 s−1, respectively. Conclusions. Depending on the model, the HGPS sample accounts for (68 − 87)% of the emission of the population in the scanned region. This suggests that unresolved sources represent a critical component of the diffuse emission measurable in the HGPS. With the foreseen jump in sensitivity of the Cherenkov Telescope Array, the number of detectable sources is predicted to increase by a factor between 5 and 9.

scholarly journals Periastron Observations of the PSR B1259-63/SS 2883 Binary System

1996 ◽  
Vol 165 ◽  
pp. 263-269
Author(s):  
Simon Johnston
Keyword(s):  
Galactic Plane ◽  
Radio Spectrum ◽  
Wide Frequency Range ◽  
Optical Observations ◽  
Rotation Measure ◽  
Linearly Polarized ◽  
Be Star ◽  
Frequency Survey ◽  
The Magnetic Field

PSR B1259-63 is a 47-millisecond pulsar which was discovered in a high frequency survey of the galactic plane (Johnston et al. 1992a) and was subsequently found to be in a highly eccentric orbit with a main-sequence Be star known as SS 2883 (Johnston et al. 1992b). Radio observations of the pulsar led to a phase connected timing solution which predicted the epoch of periastron to be 1994 January 9 (MJD 49361.2); optical observations of the Be star led to a determination of its mass and of the size of its circumstellar disk (Johnston et al. 1994a): the star is of approximate spectral type B1e, with mass 10 M⊙ and radius 6 R⊙. If this mass is correct and the pulsar has a mass of 1.4 M⊙, then the inclination angle of the plane of the orbit with respect to the sky is 35°. This pulsar has an unusually flat radio spectrum compared to most pulsars, which makes it easily detectable up to 8.4 GHz. The narrow pulse permits dispersion and scattering measurements for studying the ionized plasma in the system. Moreover, the pulses are highly linearly polarized and permit determination of the rotation measure (RM), allowing measurements of the magnetic field along the line of sight. The 3.5-yr orbit of the pulsar around its companion thus provides us with an excellent probe of the stellar wind of the Be star over a wide frequency range.

scholarly journals An overview of the structure and kinematics of the Magellanic Clouds

1991 ◽  
Vol 148 ◽  
pp. 15-23 ◽  
Author(s):  
B. E. Westerlund
Keyword(s):  
Star Formation ◽  
Observational Data ◽  
Spiral Structure ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Magellanic Clouds ◽  
Line Of Sight ◽  
Small Magellanic Cloud ◽  
Complex Velocity ◽  
The Past

A vast amount of observational data concerning the structure and kinematics of the Magellanic Clouds is now available. Many basic quantities (e.g. distances and geometry) are, however, not yet sufficiently well determined. Interactions between the Small Magellanic Cloud (SMC), the Large Magellanic Cloud (LMC) and our Galaxy have dominated the evolution of the Clouds, causing bursts of star formation which, together with stochastic self-propagating star formation, produced the observed structures. In the youngest generation in the LMC it is seen as an intricate pattern imitating a fragmented spiral structure. In the SMC much of the fragmentation is along the line of sight complicating the reconstruction of its history. The violent events in the past are also recognizable in complex velocity patterns which make the analysis of the kinematics of the Clouds difficult.

Discovery of Three Large HII Regions in the Galactic Plane

2008 ◽  
Vol 8 (5) ◽  
pp. 575-579 ◽  
Author(s):  
Wei-Bin Shi ◽  
Xiao-Hui Sun ◽  
Jin-Lin Han ◽  
Xu-Yang Gao ◽  
Li Xiao
Keyword(s):  
Galactic Plane ◽  
Hii Regions

scholarly journals Hybrid 3-D Spectrophotometry of Emission-Line Nebulae at Ohio State

1995 ◽  
Vol 149 ◽  
pp. 167-171
Author(s):  
Richard W. Pogge ◽  
Nancy Joanne Lame
Keyword(s):  
Emission Line ◽  
Planetary Nebulae ◽  
Hii Regions ◽  
Ohio State University ◽  
State University ◽  
Considerable Success ◽  
Fabry Perot ◽  
The Ohio State University ◽  
Scientific Results ◽  
Narrowband Filter

AbstractA program of 3-D spectrophotometry of emission nebulae being carried out at the Ohio State University will be described. We have had considerable success combining Fabry-Perot imaging, long-slit spectroscopy, and narrowband filter imaging into a hybrid 3-D spectroscopic approach that we have used to obtain detailed spectrophotometric maps of the density, temperature, extinction, and ionization in HII regions and Planetary Nebulae. The centerpiece instrument of this effort, the OSU Imaging Fabry-Perot Spectrograph (IFPS), will be described, and scientific results illustrative of our work will be presented.

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