PG3, A field in the Bulge of Our Galaxy: Description of a Galactic Model

1993 ◽  
pp. 319-322
Author(s):  
Y. K. Ng ◽  
G. Bertelli ◽  
C. Chiosi ◽  
A. Bressan ◽  
H. Habing ◽  
...  
Keyword(s):  
Galactic Model

scholarly journals Estimation of Galactic Model Parameters by Interval Method

1996 ◽  
Vol 169 ◽  
pp. 713-714
Author(s):  
S. A. Kutuzov
Keyword(s):  
Mutual Interaction ◽  
Component Model ◽  
Model Parameters ◽  
Interval Method ◽  
Two Component ◽  
The Galaxy ◽  
Galactic Model

The interval method of estimating model parameters (MPs) for the Galaxy was suggested earlier (Kutuzov 1988). Intervals are proposed to be used both for observational estimates of galactic parameters (GPs) and for the values of MPs. In this work we consider a model as a tool for studying mutual interaction of GPs. Two-component model is considered (Kutuzov, Ossipkov 1989). We have to estimate the array P of eight MPs.

scholarly journals Estimation of Galactic model parameters in high latitudes with the SDSS and SCUSS

2013 ◽  
Vol 9 (S298) ◽  
pp. 404-404
Author(s):  
Cuihua Du ◽  
Yunpeng Jia ◽  
Xiyan Peng
Keyword(s):  
Model Parameters ◽  
High Latitudes ◽  
The South ◽  
Statistical Errors ◽  
Count Method ◽  
Sky Survey ◽  
Star Count ◽  
The Galaxy ◽  
Galactic Model

AbstractBased on the South Galactic Cap U-band Sky Survey (SCUSS) and SDSS observation, we adopted the star-count method to analyze the stellar distribution in different directions of the Galaxy. We find that these model parameters may be variable with observed direction, which cannot simply be attributed to statistical errors.

scholarly journals Estimation of absolute magnitude-dependent Galactic model parameters in intermediate latitude with SDSS and SCUSS

2014 ◽  
Vol 441 (1) ◽  
pp. 503-512 ◽  
Author(s):  
Yunpeng Jia ◽  
Cuihua Du ◽  
Zhenyu Wu ◽  
Xiyan Peng ◽  
Jun Ma ◽  
...  
Keyword(s):  
Absolute Magnitude ◽  
Model Parameters ◽  
Galactic Model

scholarly journals The Magellanic System: the puzzle of the leading gas stream

2019 ◽  
Vol 488 (1) ◽  
pp. 918-938 ◽  
Author(s):  
Thor Tepper-García ◽  
Joss Bland-Hawthorn ◽  
Marcel S Pawlowski ◽  
Tobias K Fritz
Keyword(s):  
Hydrodynamic Interaction ◽  
The Galaxy ◽  
Galactic Model ◽  
Coronal Density ◽  
Coronal Rotation ◽  
Cool Gas ◽  
Hot Corona ◽  
Magellanic Stream ◽  
First Time ◽  
Gas Bearing

ABSTRACT The Magellanic Clouds (MCs) are the most massive gas-bearing systems falling into the Galaxy at the present epoch. They show clear signs of interaction, manifested in particular by the Magellanic Stream, a spectacular gaseous wake that trails from the MCs extending more than 150° across the sky. Ahead of the MCs is the ‘Leading Arm’ usually interpreted as the tidal counterpart of the Magellanic Stream, an assumption we now call into question. We revisit the formation of these gaseous structures in a first-infall scenario, including for the first time a Galactic model with a weakly magnetized, spinning hot corona. In agreement with previous studies, we recover the location and the extension of the Stream on the sky. In contrast, we find that the formation of the Leading Arm – that is otherwise present in models without a corona – is inhibited by the hydrodynamic interaction with the hot component. These results hold with or without coronal rotation or a weak, ambient magnetic field. Since the existence of the hot corona is well established, we are led to two possible interpretations: (i) the Leading Arm survives because the coronal density beyond 20 kpc is a factor ≳10 lower than required by conventional spheroidal coronal X-ray models, in line with recent claims of rapid coronal rotation; or (ii) the ‘Leading Arm’ is cool gas trailing from a frontrunner, a satellite moving ahead of the MCs, consistent with its higher metallicity compared to the trailing stream. Both scenarios raise issues that we discuss.

scholarly journals The Galactic Distribution of Electron Density Microstructure Inferred from Radio Scattering Observations

2001 ◽  
Vol 182 ◽  
pp. 11-16
Author(s):  
James Cordes
Keyword(s):  
Interstellar Medium ◽  
Radio Wave ◽  
Electron Density ◽  
Wave Scattering ◽  
Galactic Model ◽  
Dispersion Measures ◽  
Pulse Broadening ◽  
Galactic Distribution

AbstractI first review the observables and optics of interstellar seeing associated with radio wave scattering in the interstellar medium. I then describe the Galactic distribution of electron density and its fluctuations, as inferred from a number of observables, including angular and pulse broadening, diffractive scintillations, and dispersion measures. Propects for improving the Galactic model are outlined.

scholarly journals Influence of galactic arm scale dynamics on the molecular composition of the cold and dense ISM III. Elemental depletion and shortcomings of the current physico-chemical models

2020 ◽  
Vol 497 (2) ◽  
pp. 2309-2319
Author(s):  
V Wakelam ◽  
W Iqbal ◽  
J-P Melisse ◽  
P Gratier ◽  
M Ruaud ◽  
...  
Keyword(s):  
Gas Phase ◽  
Molecular Form ◽  
Dense Medium ◽  
Chemical Model ◽  
Physical Conditions ◽  
Dense Cores ◽  
Chemical Models ◽  
Physico Chemical ◽  
Galactic Model ◽  
Elemental Depletion

ABSTRACT We present a study of the elemental depletion in the interstellar medium. We combined the results of a Galactic model describing the gas physical conditions during the formation of dense cores with a full-gas-grain chemical model. During the transition between diffuse and dense medium, the reservoirs of elements, initially atomic in the gas, are gradually depleted on dust grains (with a phase of neutralization for those which are ions). This process becomes efficient when the density is larger than 100 cm−3. If the dense material goes back into diffuse conditions, these elements are brought back in the gas phase because of photo-dissociations of the molecules on the ices, followed by thermal desorption from the grains. Nothing remains on the grains for densities below 10 cm−3 or in the gas phase in a molecular form. One exception is chlorine, which is efficiently converted at low density. Our current gas–grain chemical model is not able to reproduce the depletion of atoms observed in the diffuse medium except for Cl, which gas abundance follows the observed one in medium with densities smaller than 10 cm−3. This is an indication that crucial processes (involving maybe chemisorption and/or ice irradiation profoundly modifying the nature of the ices) are missing.

scholarly journals High reddening patches in Gaia DR2

2020 ◽  
Vol 634 ◽  
pp. A33
Author(s):  
Leire Beitia-Antero ◽  
Ana Inés Gómez de Castro ◽  
Raúl de la Fuente Marcos
Keyword(s):  
Star Formation ◽  
Milky Way ◽  
Spectroscopic Analysis ◽  
Galactic Halo ◽  
Spiral Galaxies ◽  
Monte Carlo Sampling ◽  
The Other ◽  
Host Galaxies ◽  
Galactic Model ◽  
Gaia Dr2

Context. Deep GALEX UV data show that the extreme outskirts of some spiral galaxies are teeming with star formation. Such young stellar populations evolving so far away from the bulk of their host galaxies challenge our overall understanding of how star formation proceeds at galactic scales. It is at present unclear whether our own Milky Way may also exhibit ongoing and recent star formation beyond the conventional edge of the disk (∼15 kpc). Aims. Using Gaia DR2 data, we aim to determine if such a population is present in the Galactic halo, beyond the nominal radius of the Milky Way disk. Methods. We studied the kinematics of Gaia DR2 sources with parallax values between 1/60 and 1/30 milliarcseconds towards two regions that show abnormally high values of extinction and reddening; the results are compared with predictions from GALAXIA Galactic model. We also plotted the color–magnitude (CM) diagrams with heliocentric distances computed inverting the parallaxes, and studied the effects of the large parallax errors by Monte Carlo sampling. Results. The kinematics point towards a Galactic origin for one of the regions, while the provenance of the stars in the other is not clear. A spectroscopic analysis of some of the sources in the first region confirms that they are located in the halo. The CM diagram of the sources suggests that some of them are young.

scholarly journals Galactic structure and turbulence, pulsar distances, and the intergalactic medium

2012 ◽  
Vol 8 (S291) ◽  
pp. 211-216 ◽  
Author(s):  
J. M. Cordes
Keyword(s):  
Electron Density ◽  
Intergalactic Medium ◽  
Galactic Structure ◽  
Density Model ◽  
Radio Bursts ◽  
Radio Waves ◽  
Next Generation ◽  
Scattering Measurements ◽  
Galactic Model ◽  
Multi Wavelength

AbstractThis paper summarizes how multi-wavelength measurements will be aggregated to determine Galactic structure in the interstellar medium (ISM) and produce the next-generation electron density model. Fluctuations in density and magnetic field from parsec scales down to about 1000 km cause a number of propagation effects in both radio waves and cosmic rays. Density microstructure appears to include Kolmogorov-like turbulence. The next generation electron-density model, NE2012, will include about double the number of lines of sight with dispersion and scattering measurements and it will be anchored with a much larger number of pulsar parallax distances. The foreground Galactic model is crucial for inferring similar ionized structures in the intergalactic medium (IGM) from scattering measurements on high-z objects. Intergalactic scattering is discussed with reference to distant sources of radio bursts. In particular, the cosmological radio scattering horizon is defined along with its analog for the ISM.

scholarly journals Volume-Limited Dependent Galactic Model Parameters

2007 ◽  
Vol 24 (4) ◽  
pp. 208-219 ◽  
Author(s):  
S. Karaali ◽  
S. Bilir ◽  
E. Yaz ◽  
E. Hamzaoğlu ◽  
R. Buser
Keyword(s):  
Axial Ratio ◽  
Absolute Magnitude ◽  
Model Parameters ◽  
Continuous Transition ◽  
Space Density ◽  
Thick Disc ◽  
The Galaxy ◽  
Galactic Model ◽  
Local Space ◽  
Galactic Longitude

AbstractWe estimate 34 sets of Galactic model parameters for three intermediate-latitude fields with Galactic longitudes l = 60°, l = 90°, and l = 180°, and we discussed their dependence on the volume. Also, we confirm the variation of these parameters with absolute magnitude and Galactic longitude. The star samples in two fields are restricted with bright and unit absolute-magnitude intervals, 4 < Mg ≤ 5, and 5 < Mg ≤ 6, whereas for the third field (l = 60°) a larger absolute-magnitude interval is adopted, 4 < Mg ≤ 10. The limiting apparent magnitudes of the star samples are g0 = 15 and g0 = 22.5 mag, which provide space densities within distances in the line of sight of ∼0.9 and 25 kpc.The Galactic model parameters for the thin disc are not volume dependent. However, the ones for the thick disc and halo do show spectacular trends in their variation with volume, except for the scalelength of the thick disc. The local space density of the thick disc increases, whereas the scaleheight of the same Galactic component decreases monotonically. However, both model parameters approach asymptotic values at large distances.The relative local space density of the halo estimated by fitting the density laws to the space densities evaluated for all volumes is constant, except for the small ones. However it is absolute-magnitude and Galactic longitude dependent. The axial ratio of the halo increases abruptly for the volumes where a thick disc is dominant, whereas it approaches an asymptotic value gradually for larger volumes, indicating a continuous transition from a disc-like structure to a spherical one at the outermost region of the Galaxy. The variation of the Galactic model parameters with absolute magnitude can be explained by their dependence on the stellar luminosity, whereas the variation with volume and Galactic longitude at short distances is a bias in analysis.

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