Discovery of three optical open clusters in the Galaxy

We report the discovery of three optical open clusters in the Milky Way. Two clusters are in Scutum (Cluster1 at l=18.44 degrees and b=-0.42 degrees, and Cluster2 at l=19.60 degrees and b=-1.02 degrees), thus projected not far from the Galactic center direction, and the other is in Canis Major (Cluster3 at l=235.61 degrees and b=-4.10 degrees), near the anti-center direction. Cluster3 is less populous than Clusters 1 and 2, but presents evidence of being a physical system. The objects were found optically by inspecting maps obtained from the Guide Star Catalogue and images from the Digitized Sky Survey. No previous identification of cluster has been reported in each area so far. The analysis was carried out with 2MASS photometry in J and H. For Cluster1 we derive an age of 25 Myr, a reddening E(B-V)=2.18 and a distance from the Sun 1.64kpc; for Cluster2, age of 500Myr, E(B-V)=0.91 and distance 2.19kpc; finally for Cluster3, age 32-100Myr, E(B-V)=0.94 and distance of 3.93kpc. Luminosity and mass functions are derived for Clusters1 and 2 which, in turn, allowed us to estimate their observed masses as 147 and 89 solar masses, respectively. Estimated total masses, by extrapolating the mass functions to 0.08 solar mass, amount to 382 and 614 solar masses, for the two clusters. Cluster3 has an observed mass of 55 solar masses. The present results indicate that further searches in the optical might still reveal new open clusters, and more so in infrared bands.Comment: accepted to Astronomy and Astrophysics, 9 figure

Interference phenomena, chiral bosons and Lorentz invariance

We have studied the theory of gauged chiral bosons and proposed a general theory, a master action, that encompasses different kinds of gauge field couplings in chiral bosonized theories with first-class chiral constraints. We have fused opposite chiral aspects of this master action using the soldering formalism and applied the final action to several well known models. The Lorentz rotation permitted us to fix conditions on the parameters of this general theory in order to preserve the relativistic invariance. We also have established some conditions on the arbitrary parameter concerned in a chiral Schwinger model with a generalized constraint, investigating both covariance and Lorentz invariance. The results obtained supplements the one that shows the soldering formalism as a new method of mass generation.Comment: 11 pages, RevTex(twocolumn). Final version to appear in Physiscal Review

Information-Entropic Measure of Energy-Degenerate Kinks in Two-Field Models

We investigate the existence and properties of kink-like solitons in a class of models with two interacting scalar fields. In particular, we focus on models that display both double and single-kink solutions, treatable analytically using the Bogomol'nyi--Prasad--Sommerfield bound (BPS). Such models are of interest in applications that include Skyrmions and various superstring-motivated theories. Exploring a region of parameter space where the energy for very different spatially-bound configurations is degenerate, we show that a newly-proposed momentum-space entropic measure called Configurational Entropy (CE) can distinguish between such energy-degenerate spatial profiles. This information-theoretic measure of spatial complexity provides a complementary perspective to situations where strictly energy-based arguments are inconclusive

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