scholarly journals Spatial Distribution of Globular Clusters in M 31

1988 ◽  
Vol 126 ◽  
pp. 551-552
Author(s):  
Jun-Ichi Watanabe ◽  
Tomohiko Yamagata

The spatial distribution of globular clusters in M 31 has been analyzed using the catalogues of Sargent et al. (1977) and Crampton et al. (1985). It is concluded that the globular clusters within the distance of 54′ from the center of M 31 show an elliptical distribution aligned to the major axis of the disk. This is similar to the distribution of metal-rich clusters in our galaxy.

Author(s):  
Jorge Peñarrubia

Abstract This paper uses statistical and N-body methods to explore a new mechanism to form binary stars with extremely large separations (≳ 0.1 pc), whose origin is poorly understood. Here, ultra-wide binaries arise via chance entrapment of unrelated stars in tidal streams of disrupting clusters. It is shown that (i) the formation of ultra-wide binaries is not limited to the lifetime of a cluster, but continues after the progenitor is fully disrupted, (ii) the formation rate is proportional to the local phase-space density of the tidal tails, (iii) the semimajor axis distribution scales as p(a)da ∼ a1/2da at a ≪ D, where D is the mean interstellar distance, and (vi) the eccentricity distribution is close to thermal, p(e)de = 2ede. Owing to their low binding energies, ultra-wide binaries can be disrupted by both the smooth tidal field and passing substructures. The time-scale on which tidal fluctuations dominate over the mean field is inversely proportional to the local density of compact substructures. Monte-Carlo experiments show that binaries subject to tidal evaporation follow p(a)da ∼ a−1da at a ≳ apeak, known as Öpik’s law, with a peak semi-major axis that contracts with time as apeak ∼ t−3/4. In contrast, a smooth Galactic potential introduces a sharp truncation at the tidal radius, p(a) ∼ 0 at a ≳ rt. The scaling relations of young clusters suggest that most ultra-wide binaries arise from the disruption of low-mass systems. Streams of globular clusters may be the birthplace of hundreds of ultra-wide binaries, making them ideal laboratories to probe clumpiness in the Galactic halo.


2006 ◽  
Vol 449 (1) ◽  
pp. 143-149 ◽  
Author(s):  
J. Ma ◽  
X. Zhou ◽  
D. Burstein ◽  
Y. Yang ◽  
Z. Fan ◽  
...  

1996 ◽  
Vol 169 ◽  
pp. 669-680
Author(s):  
F.D.A. Hartwick

The spatial distribution of the outlying satellites of the Galaxy has been determined by fitting a three dimensional surface to the positions of 10 companion galaxies and 13 distant globular clusters. Both groups show a highly flattened distribution whose minor axes are aligned to within ∼ 5°. The combined group of 23 objects shows a triaxial distribution with semimajor axis extending ∼ 400 kpc. The minor axis is inclined at ∼ 76° to the Galactic poles. There is a suggestion of a nested hierarchy consisting of satellite galaxies, globular clusters, and distant halo field stars, in order of decreasing spatial extension.


1993 ◽  
Vol 153 ◽  
pp. 323-324
Author(s):  
B. Barbuy ◽  
E. Bica ◽  
S. Ortolani

We have obtained CCD BVRI colour-magnitude diagrams for a series of disk globular clusters, improving parameters and detecting a new one: Lyngå 7. Using the magnitude difference between turn-off and horizontal branch Δ(TO-HB) as an age discriminator, and their spatial distribution we compare old disk open clusters, young halo globular clusters, and metal-rich disk globular clusters, obtaining clues to the Galaxy formation process.


1970 ◽  
Vol 38 ◽  
pp. 51-60
Author(s):  
J. Einasto ◽  
U. Rümmel

A model for the Andromeda galaxy, M 31, has been derived from the available radio, photometric, and spectroscopic data. The model consists of four components – the nucleus, the bulge, the disc, and the flat component.For all components the following functions have been found: the mass density; the mass-to-light ratio; the velocity dispersions in three perpendicular directions (for the plane of symmetry and the axis of the galaxy); the deviation angle of the major axis of the velocity ellipsoid from the plane of symmetry; the centroid velocity (for the plane of symmetry).Our model differs in two points from the models obtained by other authors: the central concentration of mass is higher (in the nucleus the mass-to-light ratio is about 170), and the total mass of the galaxy (200 × 109 solar masses) is smaller. The differences can be explained by different rotation curves adopted, and by attributing more weight to photometric and spectroscopic data in the case of our model.


2019 ◽  
Vol 623 ◽  
pp. A65 ◽  
Author(s):  
Song Wang ◽  
Jun Ma ◽  
Jifeng Liu

In this paper, we present photometry of 53 globular clusters (GCs) in the M 31 outer halo, including the GALEX far-ultraviolet (FUV) and near-ultraviolet (NUV), SDSS ugriz, 15 intermediate-band filters of BATC, and 2MASS JHKs bands. By comparing the multicolour photometry with stellar population synthesis models, we determine the metallicities, ages, and masses for these GCs, aiming to probe the merging/accretion history of M 31. We find no clear trend of metallicity and mass with the de-projected radius. The halo GCs younger than ∼8 Gyr are mostly located at the de-projected radii around 100 kpc, but this may be due to a selection effect. We also find that the halo GCs have consistent metallicities with their spatially associated substructures, which provides further evidence of the physical association between them. Both the disc and halo GCs in M 31 show a bimodal luminosity distribution. However, we should emphasise that there are more faint halo GCs which are not seen in the disc. The bimodal luminosity function of the halo GCs may reflect a different origin or evolution environment in their original hosts. The M 31 halo GCs include one intermediate metallicity group (−1.5 < [Fe/H] < −0.4) and one metal-poor group ([Fe/H] < −1.5), while the disc GCs have one metal-rich group more. There are considerable differences between the halo GCs in M 31 and the Milky Way (MW). The total number of GCs in M 31 is approximately three times greater than in the MW, however M 31 has about six times more halo GCs than the MW. Compared to the halo GCs of M 31, those of the MW are mostly metal-poor. Both the numerous halo GCs and the higher-metallicity component are suggestive of an active merger history of M 31.


2011 ◽  
Vol 531 ◽  
pp. A155 ◽  
Author(s):  
S. Perina ◽  
S. Galleti ◽  
F. Fusi Pecci ◽  
M. Bellazzini ◽  
L. Federici ◽  
...  
Keyword(s):  

2009 ◽  
Vol 500 (2) ◽  
pp. 769-779 ◽  
Author(s):  
M. Henze ◽  
W. Pietsch ◽  
F. Haberl ◽  
G. Sala ◽  
R. Quimby ◽  
...  
Keyword(s):  
X Ray ◽  

2004 ◽  
Vol 194 ◽  
pp. 240-240
Author(s):  
James D. Neill ◽  
Michael M. Shara ◽  
Elaine Halbedel ◽  
Viktor Malnushenko

A spatially complete Hα survey of M81 for novae was conducted continuously over a 5 month interval using the Calypso Telescope at Kitt Peak, AZ. A raw nova rate for M81 gives 23 yr–1 which is a lower limit. Monte Carlo simulations using nova light curves and survey frame limits yield a nova rate of . Using this value and the K-band photometry for M81 from the 2MASS Large Galaxy Atlas of Jarret et al. (2003) gives a luminosity specific nova rate of .The spatial distribution of the novae follows the bulge light much better than the disk or total light according to KS tests of their radial distribution. The asymmetric nova distribution across the major axis line of M81 implies a bulge-to-disk nova ratio of > 9 and supports the idea that novae originate primarily in older stellar populations.


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