Core Velocity Dispersion Research Articles

Gravitational formation times and stellar mass distributions for stars of mass 0.3-30 solar masses

The width of the 1.3 cm line of NH 3 in a dense core is related by simple power laws to the luminosity and mass of the most massive star associated with the core. These relations link the mass of the star to the initial conditions in the gas which formed the star. At the size scale ∼0.1 pc of NH 3 line observations, the effects of stellar winds on the core velocity dispersion are estimated from observations of cores with and without stars, and from the dependence of the wind momentum flux on stellar luminosity

Dynamical study of the LMC globular cluster NGC 1978 from core velocity dispersion

The projected velocity dispersion in the core of the Large Magellanic Cloud (LMC) intermediate-age globular cluster NGC 1978 is deduced from integrated light spectra. A numerical cross-correlation technique gives a projected velocity dispersion σp(core) = 5.8±1.2 km s−1. Multimass anisotropic King-Michie dynamical models are applied to the observational constraints given by the surface brightness profile and the above central projected velocity dispersion. Depending on the model, the values obtained for the total mass of the cluster range from 0.36 to 1.44 106M⊙, corresponding to mass-to-light ratios M/LV ranging from 1.2 to 4.2 (M/LV)⊙, values typical of galactic globular clusters.

Clouds, cores, and stars in the nearest molecular complexes

The properties and structure of six molecular complexes within 500 pc of the Sun are described and compared. They are generally organized into elongated filaments which appear connected to less elongated, more massive clouds. Their prominent star clusters tend to be located in the massive clouds rather than in the filaments. The complexes have similar structure, but big differences in scale, from a few pc to some 30 pc. They show a pattern of regional virial equilibrium, where the massive, centrally located clouds are close to virial equilibrium, while the less massive filaments and other small clouds have too little mass to bind their observed internal motions. Complexes can be ranked according to increasing size, mass, core mass, and the mass and number of the associated stars: they range from Lupus to Taurus to Ophiuchus to Perseus to Orion B to Orion A. The cores in nearby complexes tend to have maps which are elongated, rather than round. The core size, velocity dispersion, and column density of most cores are consistent with virial equilibrium. Cores in Orion tend to exceed cores in Taurus in their line width, size, temperature, mass, and in the mass of the associated star, if any. Stars in Orion tend to be more numerous and more massive than in Taurus, while those in Taurus tend to be more numerous and more massive than in Lupus. The mass of a core tends to increase with the mass of the cloud where it is found, with the mass of the star cluster with which it is associated, and with its proximity to a star cluster. These properties suggest that complexes and their constituent cores and clusters develop together over time, perhaps according to the depth of the gravitational well of the complex.

Clouds, cores, and stars in the nearest molecular complexes

The properties and structure of six molecular complexes within 500 pc of the Sun are described and compared. They are generally organized into elongated filaments which appear connected to less elongated, more massive clouds. Their prominent star clusters tend to be located in the massive clouds rather than in the filaments. The complexes have similar structure, but big differences in scale, from a few pc to some 30 pc. They show a pattern of regional virial equilibrium, where the massive, centrally located clouds are close to virial equilibrium, while the less massive filaments and other small clouds have too little mass to bind their observed internal motions. Complexes can be ranked according to increasing size, mass, core mass, and the mass and number of the associated stars: they range from Lupus to Taurus to Ophiuchus to Perseus to Orion B to Orion A. The cores in nearby complexes tend to have maps which are elongated, rather than round. The core size, velocity dispersion, and column density of most cores are consistent with virial equilibrium. Cores in Orion tend to exceed cores in Taurus in their line width, size, temperature, mass, and in the mass of the associated star, if any. Stars in Orion tend to be more numerous and more massive than in Taurus, while those in Taurus tend to be more numerous and more massive than in Lupus. The mass of a core tends to increase with the mass of the cloud where it is found, with the mass of the star cluster with which it is associated, and with its proximity to a star cluster. These properties suggest that complexes and their constituent cores and clusters develop together over time, perhaps according to the depth of the gravitational well of the complex.

SUBSTRUCTURE WITHIN CLUSTERS OF GALAXIES.

ABSTRACT Surface number density contour maps based on Dressler's (1976, 1980) studies of 65 rich clusters are presented to demonstrate the frequent occurrence of substructure in these dense systems. A prescription is given for examining the significance of such structure and it is shown that structure on scales equal to or larger than 0.24 Mpc (H0 = 100 km/s Mpc) is present in approximately 40% of the clusters in this sample. Many of the remaining clusters are elongated. The contour plots are useful for comparison with X-ray surface brightness maps. Together with available velocity data, they also serve warning that many rich clusters may not be simply characterized by a single core radius and velocity dispersion.

CCD photometry of the nuclei of three supergiant elliptical galaxies - Evidence for a supermassive object in the center of the radio galaxy NGC 6251

view Abstract Citations (63) References (11) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS CCD photometry of the nuclei of three supergiant elliptical galaxies: evidence for a supermassive object in the center of the radio galaxy NGC 6251. Young, P. J. ; Sargent, W. L. W. ; Kristian, J. ; Westphal, J. A. Abstract We have analyzed charged coupled device (CCD) photometry in the g and r bands of three supergiant elliptical galaxies: NGC 4874 and NGC 4889 in the Coma cluster, and the radio galaxy NGC 6251. The profiles of NGC 4874 and NGC 4889 are closely fitted by King models. The profile of NGC 6251 cannot be fitted by a King model, nor by a King model plus a central point luminosity source (the presence of which is suggested by a blue trend in the colors at small radii). The previously studied profile of M87, when convolved with an appropriate Gaussian function to allow for the difference in distance, closely resembles the profile of NGC 6251 (but not those of NGC 4874 or NGC 4889). NGC 6251 was successfully fitted with a luminosity profile containing both a point luminosity source and a central point mass. The value of this point mass cannot be determined without additional dynamical data. However, if the core velocity dispersion is similar to that of other giant ellipticals of the same absolute magnitude, the point mass is likely to be about 2.4 x l0 M0, similar to the value reported earlier for M87. The data are also used to derive upper limits for possible central point masses in NGC 4874 and NGC 4889. Subject headings: galaxies: individual - galaxies: nuclei - galaxies: photometry - galaxies: structure Publication: The Astrophysical Journal Pub Date: November 1979 DOI: 10.1086/157474 Bibcode: 1979ApJ...234...76Y Keywords: Astronomical Photometry; Charge Coupled Devices; Elliptical Galaxies; Galactic Nuclei; Radio Galaxies; Ellipticity; Luminous Intensity; Supermassive Stars; Astrophysics; Giant Galaxies:Photometry; Giant Galaxies:Structure; Photometry:Radio Galaxies; Radio Galaxies:Structure full text sources ADS | data products NED (3)