2,333 research outputs found
NTT infrared imaging of star cluster candidates towards the central parts of the Galaxy
We address the issue whether the central parts of the Galaxy harbour young
clusters other than Arches, Quintuplet and the Nuclear Young Cluster. A large
sample of centrally projected cluster candidates has been recently identified
from the 2MASS J, H and Ks Atlas. We provide a catalogue of higher angular
resolution and deeper images for 57 2MASS cluster candidates, obtained with the
near-IR camera SOFI at the ESO NTT telescope. We classify 10 objects as star
clusters, some of them deeply embedded in gas and/or dust clouds. Three other
objects are probably star clusters, although the presence of dust in the field
does not exclude the possibility of their being field stars seen through
low-absorption regions. Eleven objects are concentrations of stars in areas of
little or no gas, and are classified as dissolving cluster candidates. Finally,
31 objects turned out to be the blend of a few bright stars, not resolved as
such in the low resolution 2MASS images. By combining the above results with
other known objects we provide an updated sample of 42 embedded clusters and
candidates projected within 7 degrees. As a first step we study Object 11 of
Dutra & Bica (2000) projected at approximately 1 degree from the nucleus. We
present H and Ks photometry and study the colour-magnitude diagram and
luminosity function. Object 11 appears to be a less massive cluster than Arches
or Quintuplet, and it is located at a distance from the Sun d=8 kpc, with a
visual absorption Av=15.Comment: accepted to A&A, 9 pages, 10 figure
New infrared star clusters in the Northern and Equatorial Milky Way with 2MASS
We carried out a survey of infrared star clusters and stellar groups on the
2MASS J, H and K_s all-sky release Atlas in the Northern and Equatorial Milky
Way (350 < l < 360, 0 < l < 230). The search in this zone complements that in
the Southern Milky Way (Dutra et al. 2003a). The method concentrates efforts on
the directions of known optical and radio nebulae. The present study provides
167 new infrared clusters, stellar groups and candidates. Combining the two
studies for the whole Milky Way, 346 infrared clusters, stellar groups and
candidates were discovered, whereas 315 objects were previously known. They
constitute an important new sample for future detailed studies.Comment: Accepted to Astronomy and Astrophysic
Vacuumless kinks systems from vacuum ones, an example
Some years ago, Cho and Vilenkin, introduced a model which presents
topological solutions, despite not having degenerate vacua as is usually
expected. Here we present a new model with topological defects, connecting
degenerate vacua but which in a certain limit recovers precisely the one
proposed originally by Cho and Vilenkin. In other words, we found a kind of
parent model for the so called vacuumless model. Then the idea is extended to a
model recently introduced by Bazeia et al. Finally, we trace some comments the
case of the Liouville model.Comment: 11 pages, 4 figure
Zero-energy states for a class of quasi-exactly solvable rational potentials
Quasi-exactly solvable rational potentials with known zero-energy solutions
of the Schro\" odinger equation are constructed by starting from exactly
solvable potentials for which the Schr\" odinger equation admits an so(2,1)
potential algebra. For some of them, the zero-energy wave function is shown to
be normalizable and to describe a bound state.Comment: LaTeX, 13 pages, 2 figures on request, to appear in Phys. Lett.
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