scholarly journals Large-scale Mapping of the Galaxy by IRAS

1985 ◽  
Vol 106 ◽  
pp. 219-222
Author(s):  
T.N. Gautier ◽  
M. G. Hauser
Keyword(s):  
Large Scale ◽  
Milky Way ◽  
Spatial Scales ◽  
High Sensitivity ◽  
The Galaxy ◽  
Infrared Astronomical Satellite ◽  
Interstellar Material ◽  
Map Resolution ◽  
Astronomical Satellite ◽  
Excellent Stability

The Infrared Astronomical Satellite (IRAS), launched 1983 January 25, has been conducting a high-sensitivity, high-resolution all-sky photometric survey at wavelengths of 12, 25, 60, and 100 μm in the infrared. One of the data products from the survey will be a map of the entire Milky Way within latitude limits of 10 degrees at a resolution of 4 arcminutes. Since the IRAS detector system is DC-coupled and has demonstrated excellent stability, this map will contain reliable information on all spatial scales larger than the map resolution. The extremely high sensitivity of the IRAS instrument for the detection of interstellar material in the survey mode is illustrated here in terms of visual extinction and dust and gas column densities.

scholarly journals Distribution of CO in the Southern Milky Way and large-scale structure in the Galaxy

1985 ◽  
Vol 106 ◽  
pp. 203-204
Author(s):  
W.H. Mccutcheon ◽  
B. J. Robinson ◽  
R. N. Manchester ◽  
J. B. Whiteoak
Keyword(s):  
Large Scale ◽  
Milky Way ◽  
Galactic Plane ◽  
Large Scale Structure ◽  
Sampling Interval ◽  
Scale Structure ◽  
Plane Region ◽  
The Galaxy ◽  
Csiro Division

The southern galactic-plane region, in the ranges 294° ≤ 1 ≤ 358°, −0°.075 ≤ b ≤ 0°.075, has been surveyed in the J = 1–0 line of 12CO with a sampling interval of 3′ arc. Observations were made with the 4-metre telescope at the CSIRO Division of Radiophysics in 1980 and 1981. Details of equipment and observing procedure are given in Robinson et al. (1982, 1983); see also McCutcheon et al. (1983).

scholarly journals Galactic Plane Surveys at Low Frequencies

2002 ◽  
Vol 199 ◽  
pp. 251-258
Author(s):  
A.R. Taylor
Keyword(s):  
Interstellar Medium ◽  
Atomic Hydrogen ◽  
Angular Resolution ◽  
Spatial Scales ◽  
High Sensitivity ◽  
Hydrogen Gas ◽  
Dimensional Structure ◽  
High Angular Resolution ◽  
Wide Field ◽  
The Galaxy

Until recently, high angular resolution and high sensitivity surveys of the radio emission from the plane of our Galaxy were available only at frequencies of several GHz, where large single dish radio telescopes provide arcminute scale angular resolution. At these frequencies thermal radiation from HII regions and diffuse ionized gas comprise a major component of the Galactic emission. Advances in wide field interferometric imaging techniques now make it possible to carry out high sensitivity surveys of the Galaxy with arcminute scale angular resolution at 1.4 GHz and below. Over the past few years initial synthesis surveys have been made. More ambitious surveys that combined sensitive continuum observations with full polarimetry and images of the 3-dimensional structure of atomic hydrogen gas at pc scales are currently underway in the northern (DRAO) and southern (ATNF) hemispheres. The interstellar medium of the Galaxy contains structure on all spatial scales, and these surveys combined data from aperture synthesis telescopes and signal dish antennas to provide full spatial frequency coverage to the resolution limit. Preliminary results reveal wide-spread features and processes in the the interstellar medium that are not readily visible by other means, including, for example, unusual atomic hydrogen structures related to the vertical transfer of matter and radiation between the disk and halo of the Galaxy, Faraday rotation structures that allow study of the magnetic field and diffuse ionized component in the plane of the Galaxy, and a cold atomic phase of the neutral medium that may provide a link between global shock phenomena in the galaxy and the formation of molecular clouds.

scholarly journals Searching for observational evidence of radial mixing in the Milky Way disk

2012 ◽  
Vol 10 (H16) ◽  
pp. 356-356
Author(s):  
Misha Haywood
Keyword(s):  
Large Scale ◽  
Milky Way ◽  
Theoretical Studies ◽  
Secular Evolution ◽  
Chemical Gradients ◽  
Current State ◽  
The Galaxy ◽  
The Subject ◽  
The Mean ◽  
State Of Affairs

AbstractSecular evolution in disks through angular momentum redistribution of stars induce radial mixing of their orbits. While theoretical studies and simulations now abound on the subject - with various predicted effects: disks growth, flattening of metallicity gradients, possible reversing of the mean age as a function of radius in disk, etc, observational evidences remain sparse. In the Galaxy, possible signatures are searched for in the local distributions of velocities, abundances and ages, or in the variation of large scale chemical gradients with time. I will present the current state of affairs and discuss what kind of evidences is available from data in the Milky Way.

scholarly journals A bisymmetric spiral magnetic field in the Milky Way

1985 ◽  
Vol 106 ◽  
pp. 251-252
Author(s):  
Y. Sofue ◽  
M. Fujimoto
Keyword(s):  
Magnetic Field ◽  
Faraday Rotation ◽  
Large Scale ◽  
Milky Way ◽  
Radio Sources ◽  
Extragalactic Radio Sources ◽  
Large Scale Magnetic Field ◽  
Rotation Measure ◽  
The Galaxy ◽  
Field Lines

The distribution of Faraday rotation measure (RM) of extragalactic radio sources shows that a large-scale magnetic field in the Galaxy is oriented along the spiral arms. The field lines change direction from one arm to the next in the inter-arm region.

scholarly journals A kinematic confirmation of the hidden Vela supercluster

2019 ◽  
Vol 490 (1) ◽  
pp. L57-L61 ◽  
Author(s):  
Hélène M Courtois ◽  
Renée C Kraan-Korteweg ◽  
Alexandra Dupuy ◽  
Romain Graziani ◽  
Noam I Libeskind
Keyword(s):  
Excellent Agreement ◽  
Mass Concentration ◽  
Large Scale ◽  
Milky Way ◽  
Large Scale Structure ◽  
Peculiar Velocity ◽  
The Galaxy ◽  
Zone Of Avoidance ◽  
First Time ◽  
The Universe

ABSTRACT The Universe region obscured by the Milky Way is very large and only future blind large H i redshift, and targeted peculiar surveys on the outer borders will determine how much mass is hidden there. Meanwhile, we apply for the first time two independent techniques to the galaxy peculiar velocity catalogue CosmicFlows−3 in order to explore for the kinematic signature of a specific large-scale structure hidden behind this zone: the Vela supercluster at cz ∼18 000 km s−1. Using the gravitational velocity and density contrast fields, we find excellent agreement when comparing our results to the Vela object as traced in redshift space. The article provides the first kinematic evidence of a major mass concentration (knot of the Cosmic Web) located in the direction behind Vela constellation, pin pointing that the Zone of Avoidance should be surveyed in detail in the future.

scholarly journals The Apache Point Observatory Galactic Evolution Experiment (APOGEE)

2009 ◽  
Vol 5 (S262) ◽  
pp. 428-429
Author(s):  
Ricardo P. Schiavon ◽  
Steven R. Majewski
Keyword(s):  
Large Scale ◽  
Near Infrared ◽  
Milky Way ◽  
Galactic Evolution ◽  
Sloan Digital Sky Survey ◽  
Elemental Abundances ◽  
Sky Survey ◽  
The Galaxy ◽  
Evolution Experiment ◽  
Under Construction

AbstractThe Apache Point Observatory Galactic Evolution Experiment (APOGEE) is a large scale, high-resolution, near-infrared spectroscopic survey of Milky Way stellar populations and one of the four experiments in the Sloan Digital Sky Survey III (SDSS-III). APOGEE will be based on a new multi-fiber cryogenic spectrograph, currently under construction, expected to begin survey observations on the 2.5 m Sloan telescope in the Spring of 2011. APOGEE will measure high-precision radial velocities and elemental abundances for ~15 elements for ~ 105 stars, and is expected to shed new light on the processes that led to the formation of the Galaxy.

Distribution of CO in the Southern Milky Way and Large-Scale Structure in the Galaxy

1985 ◽  
pp. 203-204
Author(s):  
W. H. McCutcheon ◽  
B. J. Robinson ◽  
R. N. Manchester ◽  
J. B. Whiteoak
Keyword(s):  
Large Scale ◽  
Milky Way ◽  
Large Scale Structure ◽  
Scale Structure ◽  
The Galaxy

scholarly journals Low-frequency measurements of synchrotron absorbing HII regions and modeling of observed synchrotron emissivity

2019 ◽  
Vol 621 ◽  
pp. A127 ◽  
Author(s):  
I. M. Polderman ◽  
M. Haverkorn ◽  
T. R. Jaffe ◽  
M. I. R. Alves
Keyword(s):  
Synchrotron Radiation ◽  
Magnetic Fields ◽  
Large Scale ◽  
Milky Way ◽  
Galactic Center ◽  
Three Dimensional ◽  
Low Frequency ◽  
Hii Regions ◽  
The Galaxy ◽  
Absorption Measurements

Context. Cosmic rays (CRs) and magnetic fields are dynamically important components in the Galaxy, and their energy densities are comparable to that of the turbulent interstellar gas. The interaction of CRs and Galactic magnetic fields (GMF) produces synchrotron radiation clearly visible in the radio regime. Detailed measurements of synchrotron radiation averaged over the line-of-sight (LOS), so-called synchrotron emissivities, can be used as a tracer of the CR density and GMF strength. Aims. Our aim is to model the synchrotron emissivity in the Milky Way using a three-dimensional dataset instead of LOS-integrated intensity maps on the sky. Methods. Using absorbed HII regions, we measured the synchrotron emissivity over a part of the LOS through the Galaxy, changing from a two-dimensional to a three-dimensional view. Performing these measurements on a large scale is one of the new applications of the window opened by current low-frequency arrays. Using various simple axisymmetric emissivity models and a number of GMF-based emissivity models, we were able to simulate the synchrotron emissivities and compare them to the observed values in the catalog. Results. We present a catalog of low-frequency absorption measurements of HII regions, their distances and electron temperatures, compiled from literature. These data show that the axisymmetric emissivity models are not complex enough, but the GMF-based emissivity models deliver a reasonable fit. These models suggest that the fit can be improved by either an enhanced synchrotron emissivity in the outer reaches of the Milky Way or an emissivity drop near the Galactic center. Conclusions. Current GMF models plus a constant CR density model cannot explain low-frequency absorption measurements, but the fits improved with slight (ad hoc) adaptations. It is clear that more detailed models are needed, but the current results are very promising.

scholarly journals Monte Carlo Simulations of the Galaxy at 12 μm: Implications for Galactic Structure

1990 ◽  
Vol 139 ◽  
pp. 121-122
Author(s):  
K. Volk ◽  
R. J. Wainscoat ◽  
M. Cohen ◽  
H. J. Walker ◽  
D. E. Schwartz
Keyword(s):  
Luminosity Function ◽  
Galactic Plane ◽  
Galactic Disk ◽  
Geometrical Parameters ◽  
Spiral Arms ◽  
Star Count ◽  
The Galaxy ◽  
Infrared Astronomical Satellite ◽  
Astronomical Satellite ◽  
Exponential Disk

We present an all-sky star count model at 12 μm based upon the Infrared Astronomical Satellite (IRAS) observations that characterize both the 12 μm luminosity function and the geometrical parameters of the galaxy. The model includes five galactic components: the bulge, the spheroid, the exponential disk, the spiral arms, and the molecular ring. The distribution of the brighter IRAS sources along the galactic plane required that the model include sources within the spiral arms and the molecular ring to produce an acceptable fit. We do not support the conclusion of Habing (1988) that the galactic disk ends just outside the solar circle, and do not require a thick disk to match the observations. We suggest that Habing's sample includes IRAS sources in the spiral arms but his model for the galactic disk does not include this critical component.

scholarly journals Investigation of Galactic Structure with Denis Star Counts

1998 ◽  
Vol 179 ◽  
pp. 231-233
Author(s):  
S. Ruphy
Keyword(s):  
Large Scale ◽  
Near Infrared ◽  
High Sensitivity ◽  
Interstellar Extinction ◽  
Galactic Structure ◽  
The Galaxy ◽  
Infrared Star ◽  
Red Giant ◽  
First Time ◽  
Infrared Star Counts

Thanks to the DENIS program (Deep Near-Infrared Survey of the Southern Sky), relatively deep near-infrared star counts are now available for the first time on a large scale. The basic method to interpret star counts in terms of galactic structure is to compare them with predictions given by models of the point source sky. Of particular promise are studies with DENIS of the spatial distribution of evolved stars in our Galaxy, thanks to its high sensitivity to red giant and to the much lower interstellar extinction that hampers visual observations of far-away stars in the disc of our Galaxy. In this paper, I present a sample of extensive comparisons between two models of the Galaxy and DENIS star counts (Ruphy 1996). I will focus on the analysis of star counts in the anticenter direction, that leads to new values for the distance of the cutoff and the radial scale length of the stellar disc.

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