scholarly journals A Radio Survey of the Southern Milky Way at a Frequency of 1440 Mc/s. I. The Isophotes and the Discrete Sources

1962 ◽  
Vol 15 (3) ◽  
pp. 354 ◽  
Author(s):  
DS Mathewson ◽  
JR Healey ◽  
JM Rome
Keyword(s):  
Milky Way ◽  
Galactic Disk ◽  
Spectral Characteristics ◽  
Radio Sources ◽  
Spectral Indices ◽  
Thermal Radio ◽  
Background Emission ◽  
Optical Identifications ◽  
Half Power ◽  
The Continuum

The 1440 Mc/s isophotes of the Southern Milky Way are presented which were obtained with an aerial beam 50' of arc at half-power points. The positions and intensities of the discrete sources resolved from the background emission are listed together with their spectral characteristics determined by comparison with the 85 -5 Mc/s Mills-Cross survey. Of 74 sources, 54 are found to have spectral indices consistent with the assumption that they radiate thermally_ Twelve new identifications of these thermal radio sources haye been made with emission nebulae by comparison with the Stromlo Atlas of Hex emission. The remaining twenty sources have nonthermal spectral indices and no new optical identifications have been made_ The continuum background emission from the galactic disk is discussed in a second paper.

scholarly journals VLBI Observations of Central Region in NGC 3079

1998 ◽  
Vol 164 ◽  
pp. 219-220 ◽  
Author(s):  
Satoko Satoh ◽  
M. Inoue ◽  
N. Nakai ◽  
K. M. Shibata ◽  
S. Kameno ◽  
...  
Keyword(s):  
Galactic Disk ◽  
Rotating Disk ◽  
Spectral Indices ◽  
Clear Indication ◽  
Central Mass ◽  
Vlbi Observations ◽  
The Galaxy ◽  
Absorption Features ◽  
Water Maser ◽  
The Continuum

AbstractWe present multi-frequency observations towards the nucleus of NGC 3079 using both Japan VLBI Network (J-Net) and the VLBA including phased VLA and Effelsberg. We detected two continuum components at 1.4 and 8.4 GHz, and determined the spectral indices for each component. Further, we found several H ɪ absorption features towards the continuum components whose velocity gradient is opposite to the galaxy rotation. Assuming rotation, the central mass is estimated to be 3 × 106M⊙. The water maser distribution extends in North-South direction along the galactic disk, while no clear indication of a Keplerian rotating disk was found.

scholarly journals Pulsars as excellent probes for the magnetic structure in our Milky Way

2012 ◽  
Vol 8 (S291) ◽  
pp. 223-228
Author(s):  
JinLin Han
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Field Strength ◽  
Magnetic Structure ◽  
Milky Way ◽  
Galactic Disk ◽  
Radio Sources ◽  
Advantages And Disadvantages ◽  
Small Scales ◽  
Dispersion Measures

AbstractIn this invited talk, I first discuss the advantages and disadvantages of many probes for the magnetic fields of the Milky Way. I conclude that pulsars are the best probes for the magnetic structure in our Galaxy, because magnetic field strength and directions can be derived from their dispersion measures (DMs) and rotation measures (RMs). Using the pulsars as probes, magnetic field structures in the Galactic disk, especially the field reversals between the arms and interarm regions, can be well revealed from the distribution of RM data. The field strengths on large scales and small scales can be derived from RM and DM data. RMs of extragalactic radio sources can be used as the indication of magnetic field directions in the spiral tangential regions, and can be used as probes for the magnetic fields in the regions farther away than pulsars when their median RMs are compared with pulsar RMs.

scholarly journals The Radio Continuum of the Large Magellanic Cloud. IV. Spectra of Sources

1972 ◽  
Vol 25 (5) ◽  
pp. 619 ◽  
Author(s):  
RX McGee ◽  
Lynette M Newton
Keyword(s):  
Supernova Remnants ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Radio Continuum ◽  
Radio Sources ◽  
Spectral Indices ◽  
Class 1 ◽  
Background Continuum ◽  
Continuum Radio ◽  
The Continuum

The continuum radio sources in the direction of the Large Magellanic Cloud are classified in terms of their spectral indices. Of 52 sources for which spectral data were available three distinct classes exist: (1) sources with spectral indices = ?0�20, of which 21 out of 23 have been identified with HII regions in the Henize catalogue; (2) sources with spectral indices < ?0�20 that have been identified with Henize objects, of which it is possible that many are supernova remnants; and (3) sources with spectral indices < ?0�20 that have not been identified with optical objects and are considered to be outside the LMC. Six "double sources" with one member belonging to class (1) and the other to class (2) were found. The background continuum radiation is also discussed.

scholarly journals 5 GHz Continuum Radiation from Southern Hemisphere Galactic HII Regions

1968 ◽  
Vol 21 (6) ◽  
pp. 881 ◽  
Author(s):  
FF Gardner ◽  
M Morimoto
Keyword(s):  
Southern Hemisphere ◽  
Hii Regions ◽  
Radio Sources ◽  
Positional Accuracy ◽  
Continuum Radiation ◽  
Thermal Radio ◽  
5 Ghz ◽  
Better Than ◽  
The Continuum

The continuum radiation from about 36 southern thermal radio sources has been surveyed at 6 cm wavelength with a beamwidth of 4'�2 arc, and maps are shown for 28 of these. The positional accuracy is better than l' arc.

scholarly journals A Radio Survey of the Southern Milky Way at a Frequency of 1440 Mc/s. II. The Continuum Emission from the Galactic Disk

1962 ◽  
Vol 15 (3) ◽  
pp. 369 ◽  
Author(s):  
DS Mathewson ◽  
JR Healey ◽  
JM Rome
Keyword(s):  
Milky Way ◽  
Spiral Structure ◽  
Galactic Disk ◽  
Neutral Hydrogen ◽  
Continuum Emission ◽  
Nonthermal Radiation ◽  
The Galaxy ◽  
Disk Component ◽  
Good Agreement ◽  
The Continuum

The 1440 Mcls survey (Part I of this series) has been used in conjunction with the 85�5Mc/s survey of Hill, Slee, and Mills (1958) to delineate the distribution of the thermal and nonthermal radiation from the disk component of the Southern Milky Way and so complete an investigation commenced by the Northern Hemisphere observers Westerhout (Leiden) and Large, Mathewson, and Haslam (Jodrell Bank). Results of the analysis show an intense concent,ration of ionized hydrogen in an irregular spiral structure in the inner regions of the Galaxy. From lII=256� to 88�, good agreement was obtained between the longitudes at which concentrations of neutral hydrogen were found to occur from H-line studies and the longitudes at which the ionized hydrogen was concentrated. The steps in the longitude distribution of the 85�5 Mcls radiation which Mills used to delineate the spiral arms of the Galaxy were not all visible in the longitude distribution of the nonthermal component obtained from this present analysis. It is believed that three of Mills's steps are thermal in origin.

scholarly journals Remarkable Symmetries in the Milky Way Disc's Magnetic Field

2011 ◽  
Vol 28 (2) ◽  
pp. 171-176 ◽  
Author(s):  
P. P. Kronberg ◽  
K. J. Newton-McGee
Keyword(s):  
Magnetic Structure ◽  
Large Scale ◽  
Milky Way ◽  
Galactic Center ◽  
Galactic Plane ◽  
Galactic Disk ◽  
Field Structure ◽  
Field Pattern ◽  
Close Coupling ◽  
Sign Change

AbstractWe apply a new, expanded compilation of extragalactic source Faraday rotation measures (RM) to investigate the broad underlying magnetic structure of the Galactic disk at latitudes ∣b∣ ≲15° over all longitudes l, where our total number of RMs is comparable to those in the combined Canadian Galactic Plane Survey (CGPS) at ∣b∣ < 4° and the Southern Galactic Plane (SGPS) ∣b∣<1.5°. We report newly revealed, remarkably coherent patterns of RM at ∣b∣≲15° from l∼270° to ∼90° and RM(l) features of unprecedented clarity that replicate in l with opposite sign on opposite sides of the Galactic center. They confirm a highly patterned bisymmetric field structure toward the inner disc, an axisymmetic pattern toward the outer disc, and a very close coupling between the CGPS/SGPS RMs at ∣b∣≲3° (‘mid-plane’) and our new RMs up to ∣b∣∼15° (‘near-plane’). Our analysis also shows the vertical height of the coherent component of the disc field above the Galactic disc's mid-plane—to be ∼1.5 kpc out to ∼6 kpc from the Sun. This identifies the approximate height of a transition layer to the halo field structure. We find no RM sign change across the plane within ∣b∣∼15° in any longitude range. The prevailing disc field pattern and its striking degree of large-scale ordering confirm that our side of the Milky Way has a very organized underlying magnetic structure, for which the inward spiral pitch angle is 5.5°±1° at all ∣b∣ up to ∼12° in the inner semicircle of Galactic longitudes. It decreases to ∼0° toward the anticentre.

scholarly journals The magnetic structure of our Galaxy: a review of observations

2008 ◽  
Vol 4 (S259) ◽  
pp. 455-466 ◽  
Author(s):  
JinLin Han
Keyword(s):  
Magnetic Fields ◽  
Magnetic Structure ◽  
Large Scale ◽  
Galactic Halo ◽  
Galactic Center ◽  
Galactic Plane ◽  
Galactic Disk ◽  
Dust Emission ◽  
Measure Data ◽  
Radio Sources

AbstractThe magnetic structure in the Galactic disk, the Galactic center and the Galactic halo can be delineated more clearly than ever before. In the Galactic disk, the magnetic structure has been revealed by starlight polarization within 2 or 3 kpc of the Solar vicinity, by the distribution of the Zeeman splitting of OH masers in two or three nearby spiral arms, and by pulsar dispersion measures and rotation measures in nearly half of the disk. The polarized thermal dust emission of clouds at infrared, mm and submm wavelengths and the diffuse synchrotron emission are also related to the large-scale magnetic field in the disk. The rotation measures of extragalactic radio sources at low Galactic latitudes can be modeled by electron distributions and large-scale magnetic fields. The statistical properties of the magnetized interstellar medium at various scales have been studied using rotation measure data and polarization data. In the Galactic center, the non-thermal filaments indicate poloidal fields. There is no consensus on the field strength, maybe mG, maybe tens of μG. The polarized dust emission and much enhanced rotation measures of background radio sources are probably related to toroidal fields. In the Galactic halo, the antisymmetric RM sky reveals large-scale toroidal fields with reversed directions above and below the Galactic plane. Magnetic fields from all parts of our Galaxy are connected to form a global field structure. More observations are needed to explore the untouched regions and delineate how fields in different parts are connected.

Spectra, optical identifications, and statistics of a complete sample of radio sources at declinations 10°–12°30′

2003 ◽  
Vol 47 (11) ◽  
pp. 903-915 ◽  
Author(s):  
A. G. Gorshkov ◽  
V. K. Konnikova ◽  
M. G. Mingaliev
Keyword(s):  
Radio Sources ◽  
Complete Sample ◽  
Optical Identifications

scholarly journals The constraining effect of gas and the dark matter halo on the vertical stellar distribution of the Milky Way

2018 ◽  
Vol 617 ◽  
pp. A142 ◽  
Author(s):  
S. Sarkar ◽  
C. J. Jog
Keyword(s):  
Dark Matter ◽  
Gravitational Field ◽  
Milky Way ◽  
Galactic Disk ◽  
Outer Region ◽  
Hydrogen Gas ◽  
Dark Matter Halo ◽  
Stellar Disk ◽  
Disk Thickness ◽  
Vertical Density

We study the vertical stellar distribution of the Milky Way thin disk in detail with particular focus on the outer disk. We treat the galactic disk as a gravitationally coupled, three-component system consisting of stars, atomic hydrogen gas, and molecular hydrogen gas in the gravitational field of the dark matter halo. The self-consistent vertical distribution for stars and gas in such a realistic system is obtained for radii between 4–22 kpc. The inclusion of an additional gravitating component constrains the vertical stellar distribution toward the mid-plane, so that the mid-plane density is higher, the disk thickness is reduced, and the vertical density profile is steeper than in the one-component, isothermal, stars-alone case. We show that the stellar distribution is constrained mainly by the gravitational field of gas and dark matter halo in the inner and the outer Galaxy, respectively. We find that the thickness of the stellar disk (measured as the half-width at half-maximum of the vertical density distribution) increases with radius, flaring steeply beyond R = 17 kpc. The disk thickness is reduced by a factor of 3–4 in the outer Galaxy as a result of the gravitational field of the halo, which may help the disk resist distortion at large radii. The disk would flare even more if the effect of dark matter halo were not taken into account. Thus it is crucially important to include the effect of the dark matter halo when determining the vertical structure and dynamics of a galactic disk in the outer region.

scholarly journals A Gaia DR2 view of the open cluster population in the Milky Way

2018 ◽  
Vol 618 ◽  
pp. A93 ◽  
Author(s):  
T. Cantat-Gaudin ◽  
C. Jordi ◽  
A. Vallenari ◽  
A. Bragaglia ◽  
L. Balaguer-Núñez ◽  
...  
Keyword(s):  
Stellar Evolution ◽  
Milky Way ◽  
Galactic Plane ◽  
Galactic Disk ◽  
Open Cluster ◽  
Open Clusters ◽  
Number Of Clusters ◽  
History Of ◽  
Gaia Dr2

Context. Open clusters are convenient probes of the structure and history of the Galactic disk. They are also fundamental to stellar evolution studies. The second Gaia data release contains precise astrometry at the submilliarcsecond level and homogeneous photometry at the mmag level, that can be used to characterise a large number of clusters over the entire sky. Aims. In this study we aim to establish a list of members and derive mean parameters, in particular distances, for as many clusters as possible, making use of Gaia data alone. Methods. We compiled a list of thousands of known or putative clusters from the literature. We then applied an unsupervised membership assignment code, UPMASK, to the Gaia DR2 data contained within the fields of those clusters. Results. We obtained a list of members and cluster parameters for 1229 clusters. As expected, the youngest clusters are seen to be tightly distributed near the Galactic plane and to trace the spiral arms of the Milky Way, while older objects are more uniformly distributed, deviate further from the plane, and tend to be located at larger Galactocentric distances. Thanks to the quality of Gaia DR2 astrometry, the fully homogeneous parameters derived in this study are the most precise to date. Furthermore, we report on the serendipitous discovery of 60 new open clusters in the fields analysed during this study.

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