scholarly journals Recombination Lines near 8·9 GHz of Strong Sources in the Southern Milky Way

1975 ◽  
Vol 28 (2) ◽  
pp. 185 ◽  
Author(s):  
RX McGee ◽  
Lynette M Newton ◽  
RA Batchelor
Keyword(s):  
Radial Velocity ◽  
Flux Density ◽  
Milky Way ◽  
Large Magellanic Cloud ◽  
Abundance Ratio ◽  
Source Size ◽  
Temperature Line ◽  
Line Half Width ◽  
Intensity Ratios ◽  
Line Temperature

Seventeen intense nebulae in the southern Milky Way have been surveyed for their radio recombination lines of hydrogen and helium, H 90IX, He 9OIX, H 113ft, H 129y, and of elements heavier than helium, X901X. The H901X line for 30Doradus in the Large Magellanic Cloud was also observed. Data on source size, flux density, continuum temperature, line temperature, line half-width and radial velocity are used to derive information about the sources. This information includes electron temperatures and turbulent velocities, the abundance ratio of singly ionized helium to ionized hydrogen, and the intensity ratios of ft and y lines to IX lines. The lines from elements heavier than helium are discussed.

scholarly journals The Ballistic Particle Model

1983 ◽  
Vol 100 ◽  
pp. 133-134
Author(s):  
Frank N. Bash
Keyword(s):  
Radial Velocity ◽  
Gravitational Potential ◽  
Molecular Clouds ◽  
Milky Way ◽  
Terminal Velocity ◽  
Particle Model ◽  
The Sun ◽  
Giant Molecular Clouds ◽  
Spiral Pattern ◽  
Armed Spiral

Bash and Peters (1976) suggested that giant molecular clouds (GMC's) can be viewed as ballistic particles launched from the two-armed spiral-shock (TASS) wave with orbits influenced only by the overall galactic gravitational potential perturbed by the spiral gravitational potential in the arms. For GMC's in the Milky Way, the model predicts that the radial velocity observed from the Sun increases with age (time since launch). We showed that the terminal velocity of CO observed from l ≃ 30° to l ≃ 60° can be understood if all GMC's are born in the spiral pattern given by Yuan (1969) and live 30 × 106 yrs. Older GMC's were predicted to have radial velocities which exceed observed terminal velocities.

scholarly journals The mass of the Milky Way out to 100 kpc using halo stars

2020 ◽  
Author(s):  
Alis J Deason ◽  
Denis Erkal ◽  
Vasily Belokurov ◽  
Azadeh Fattahi ◽  
Facundo A Gómez ◽  
...  
Keyword(s):  
Distribution Function ◽  
Mass Concentration ◽  
Milky Way ◽  
Function Analysis ◽  
Large Magellanic Cloud ◽  
Systematic Bias ◽  
Cosmological Simulations ◽  
Halo Stars ◽  
Systematic Effects ◽  
Mass Estimate

Abstract We use a distribution function analysis to estimate the mass of the Milky Way out to 100 kpc using a large sample of halo stars. These stars are compiled from the literature, and the vast majority ($\sim \! 98\%$) have 6D phase-space information. We pay particular attention to systematic effects, such as the dynamical influence of the Large Magellanic Cloud (LMC), and the effect of unrelaxed substructure. The LMC biases the (pre-LMC infall) halo mass estimates towards higher values, while realistic stellar halos from cosmological simulations tend to underestimate the true halo mass. After applying our method to the Milky Way data we find a mass within 100 kpc of M( < 100kpc) = 6.07 ± 0.29(stat.) ± 1.21(sys.) × 1011M⊙. For this estimate, we have approximately corrected for the reflex motion induced by the LMC using the Erkal et al. model, which assumes a rigid potential for the LMC and MW. Furthermore, stars that likely belong to the Sagittarius stream are removed, and we include a 5% systematic bias, and a 20% systematic uncertainty based on our tests with cosmological simulations. Assuming the mass-concentration relation for Navarro-Frenk-White haloes, our mass estimate favours a total (pre-LMC infall) Milky Way mass of M200c = 1.01 ± 0.24 × 1012M⊙, or (post-LMC infall) mass of M200c = 1.16 ± 0.24 × 1012 M⊙ when a 1.5 × 1011M⊙ mass of a rigid LMC is included.

scholarly journals Chemical Abundances of Seven Outer Halo M31 Globular Clusters from the Pan-Andromeda Archaeological Survey

2016 ◽  
Vol 11 (S321) ◽  
pp. 10-12
Author(s):  
Charli M. Sakari
Keyword(s):  
Globular Clusters ◽  
Milky Way ◽  
Dwarf Galaxy ◽  
Large Magellanic Cloud ◽  
Archaeological Survey ◽  
Chemical Abundances ◽  
Light Spectra ◽  
Sigma Level ◽  
Stellar Streams ◽  
Detailed Chemical

AbstractObservations of stellar streams in M31’s outer halo suggest that M31 is actively accreting several dwarf galaxies and their globular clusters (GCs). Detailed abundances can chemically link clusters to their birth environments, establishing whether or not a GC has been accreted from a satellite dwarf galaxy. This talk presents the detailed chemical abundances of seven M31 outer halo GCs (with projected distances from M31 greater than 30 kpc), as derived from high-resolution integrated-light spectra taken with the Hobby Eberly Telescope. Five of these clusters were recently discovered in the Pan-Andromeda Archaeological Survey (PAndAS)—this talk presents the first determinations of integrated Fe, Na, Mg, Ca, Ti, Ni, Ba, and Eu abundances for these clusters. Four of the target clusters (PA06, PA53, PA54, and PA56) are metal-poor ([Fe/H] < -1.5), α-enhanced (though they are possibly less alpha-enhanced than Milky Way stars at the 1 sigma level), and show signs of star-to-star Na and Mg variations. The other three GCs (H10, H23, and PA17) are more metal-rich, with metallicities ranging from [Fe/H] = -1.4 to -0.9. While H23 is chemically similar to Milky Way field stars, Milky Way GCs, and other M31 clusters, H10 and PA17 have moderately-low [Ca/Fe], compared to Milky Way field stars and clusters. Additionally, PA17’s high [Mg/Ca] and [Ba/Eu] ratios are distinct from Milky Way stars, and are in better agreement with the stars and clusters in the Large Magellanic Cloud (LMC). None of the clusters studied here can be conclusively linked to any of the identified streams from PAndAS; however, based on their locations, kinematics, metallicities, and detailed abundances, the most metal-rich PAndAS clusters H23 and PA17 may be associated with the progenitor of the Giant Stellar Stream, H10 may be associated with the SW Cloud, and PA53 and PA56 may be associated with the Eastern Cloud.

scholarly journals Theoretical fit of Cepheid light and radial velocity curves in the Large Magellanic Cloud cluster NGC 1866

2012 ◽  
Vol 428 (3) ◽  
pp. 2185-2197 ◽  
Author(s):  
M. Marconi ◽  
R. Molinaro ◽  
V. Ripepi ◽  
I. Musella ◽  
E. Brocato
Keyword(s):  
Radial Velocity ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Cloud Cluster

scholarly journals Local Stellar Kinematics from RAVE data—VII. Metallicity Gradients from Red Clump Stars

2016 ◽  
Vol 33 ◽  
Author(s):  
Ö. Önal Taş ◽  
S. Bilir ◽  
G. M. Seabroke ◽  
S. Karaali ◽  
S. Ak ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Milky Way ◽  
Absolute Magnitude ◽  
Selection Effects ◽  
Stellar Kinematics ◽  
Experiment Data ◽  
Radial Gradient ◽  
Data Release ◽  
The Difference ◽  
Red Clump

AbstractWe investigate the Milky Way Galaxy’s radial and vertical metallicity gradients using a sample of 47 406 red clump stars from the RAdial Velocity Experiment Data Release 4. Distances are calculated by adopting Ks-band absolute magnitude as −1.54±0.04 mag for the sample. The metallicity gradients are calculated with their current orbital positions (Rgc and Z) and with their orbital properties (Rm and zmax): d[Fe/H]/dRgc = −0.047±0.003 dex kpc−1 for |Z| ≤ 0.5 kpc and d[Fe/H]/dRm = −0.025±0.002 dex kpc−1 for zmax ≤ 0.5 kpc. This reaffirms the radial metallicity gradient in the thin disc but highlights that gradients are sensitive to the selection effects caused by the difference between Rgc and Rm. The radial gradient is flat in the distance interval 0.5-1 kpc from the plane and then becomes positive greater than 1 kpc from the plane. The radial metallicity gradients are also eccentricity dependent. We showed that d[Fe/H]/dRm = −0.089±0.010, −0.073±0.007, −0.053±0.004 and −0.044±0.002 dex kpc−1 for ep ≤ 0.05, ep ≤ 0.07, ep ≤ 0.10 and ep ≤ 0.20 sub-samples, respectively, in the distance interval zmax ≤ 0.5 kpc. Similar trend is found for vertical metallicity gradients. Both the radial and vertical metallicity gradients are found to become shallower as the eccentricity of the sample increases. These findings can be used to constrain different formation scenarios of the thick and thin discs.

scholarly journals The interstellar medium of the Magellanic Clouds from absorption lines

1991 ◽  
Vol 148 ◽  
pp. 401-406 ◽  
Author(s):  
Klaas S. De Boer
Keyword(s):  
Interstellar Medium ◽  
Absorption Line ◽  
Milky Way ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Magellanic Clouds ◽  
Absorption Lines ◽  
Small Magellanic Cloud ◽  
General Aspects

General aspects of ISM studies using absorption line studies are given and available data are reviewed. Topics are: galactic foreground gas, individual fields in the Magellanic Clouds (MCs) and MC coronae. Overall investigations are discussed. It is demonstrated that the metals in the gas of the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) are a factor of 3 and 10, respectively, in abundance below solar levels. The depletion pattern in the LMC is similar to that of the Milky Way.

Coravel Radial-Velocity Curves for Cepheids in the Large Magellanic Cloud

1984 ◽  
Vol 88 ◽  
pp. 375-380
Author(s):  
M. Imbert ◽  
J. Andersen ◽  
A. Ardeberg ◽  
C. Bardin ◽  
W. Benz ◽  
...  
Keyword(s):  
Comparative Study ◽  
Radial Velocity ◽  
Stellar Evolution ◽  
Large Magellanic Cloud ◽  
Magellanic Clouds ◽  
Independent Determination ◽  
Fundamental Information ◽  
The Galaxy ◽  
Cepheid Variables

Radii and luminosities for Cepheid variables provide fundamental information on stellar evolution. Such data, obtained by the Baade-Wesselink method, are available and have been used for a number of galactic Cepheids. It is of particular interest to obtain corresponding data for Cepheids in the Magellanic Clouds. Firstly, this allows a comparative study of stellar evolution between the Galaxy and the Magellanic Clouds. Secondly, it provides data for an independent determination of the distance to the Magellanic Clouds.Radial-velocity observations have been made for a total of around 20 Cepheid variables in both the LMC and the SMC. All measurements were made with the photoelectric scanner CORAVEL attached to the Cassegrain focus of the Danish 1.54-m telescope at European Southern Observatory, La Silla, Chile. Observations were made from January 1981 through October 1983. The accuracy of individual radial-velocity observations is of the order of 1 km s−1. The B magnitudes of the six Cepheids presented range from 13.0 to 15.5.

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