Near-Infrared photometry and spectroscopy of NGC 6539 and UKS 1: two intermediate metallicity Bulge Globular Clusters

Using the SofI imager at ESO/NTT and NIRSPEC spectrograph at KeckII, we have obtained J,K images and echelle spectra covering the range 1.5 - 1.8 micron for the intermediate metallicity Bulge globular clusters NGC6539 and UKS1. We find [Fe/H]=-0.76 and -0.78, respectively, and an average alpha-enhancement of +0.44 dex and +0.31 dex, consistent with previous measurements of metal rich Bulge clusters, and favoring the scenario of rapid chemical enrichment. We also measure very low 12C/13C=4.5 +/-1 isotopic ratios in both clusters, suggesting that extra-mixing mechanisms due to cool bottom processing are at work during the evolution along the Red Giant Branch. Finally, we measure accurate radial velocities of =+31 +/-4Km/s and =+57 +/-6Km/s and velocity dispersion of about 8 Km/s and 11 Km/s for NGC6539 and UKS1, respectively.Comment: 10 pages, 7 figures, accepted for publication at MNRA

Towards the absolute planes: a new calibration of the Bolometric Corrections and Temperature scales for Population II Giants

We present new determinations of bolometric corrections and effective temperature scales as a function of infrared and optical colors, using a large database of photometric observations of about 6500 Population II giants in Galactic Globular Clusters (GGCs), covering a wide range in metallicity (-2.0<[Fe/H]<0.0). New relations for BC_K vs (V-K), (J-K) and BC_V vs (B-V), (V-I), (V-J), and new calibrations for T_eff, using both an empirical relation and model atmospheres, are provided. Moreover, an empirical relation to derive the R parameter of the Infrared Flux Method as a function of the stellar temperature is also presented.Comment: 10 pages, 12 .ps figures, MN Latex, accepted by MNRA

No evidence of chemical anomalies in the bimodal turnoff cluster NGC 1806 in the LMC

We have studied the chemical composition of NGC 1806, a massive, intermediate-age globular cluster that shows a double main sequence turnoff. We analyzed a sample of high-resolution spectra (secured with FLAMES at the Very Large Telescope) for 8 giant stars, members of the cluster, finding an average iron content of [Fe/H]=--0.60 +- 0.01 dex and no evidence of intrinsic star-to-star variations in the abundances of light elements (Na, O, Mg, Al). Also, the (m_(F814W); m_(F336W)-m_(F814W)) color-magnitude diagram obtained by combining optical and near-UV Hubble Space Telescope photometry exhibits a narrow red giant branch, thus ruling out intrinsic variations of C and N abundances in the cluster. These findings demonstrate that NGC 1806 does not harbor chemically distinct sub-populations, at variance with what was found in old globular clusters. In turn, this indicates that the double main sequence turnoff phenomenon cannot be explained in the context of the self-enrichment processes usually invoked to explain the chemical anomalies observed in old globulars. Other solutions (i.e., stellar rotation, merging between clusters or collisions with giant molecular clouds) should be envisaged to explain this class of globulars.Comment: Accepted for publication by ApJ Letters; 15 pages, 4 figures, 1 tabl

High resolution infrared spectra of bulge globular clusters: Liller~1 and NGC 6553

Using the NIRSPEC spectrograph at Keck II, we have obtained echelle spectra covering the range 1.5-1.8um for 2 of the brightest giants in Liller 1 and NGC 6553, old metal rich globular clusters in the Galactic bulge. We use spectrum synthesis for the abundance analysis, and find [Fe/H]=-0.3 +/- 0.2 and [O/H]=+0.3 +/- 0.2 dex. The composition of the clusters is similar to that of field stars in the bulge and is consistent with a sceanrio in which the clusters formed early, with rapid enrichment. We have dificulty achieveing a good fit to the spectrum of NGC 6553 using either the low or the high values recently reported in the literature, unless unusually large, or no alpha-element enhancements are adopted, respectively.Comment: To appear in the Astronomical Journal, March 200

A framework for distributed interaction in intelligent environments

Ubiquitous computing is extending its applications to an increasing number of domains. "Monolithic" approaches use centralised systems, controlling devices and users' requests. A different solution can be found in works proposing "distributed" intelligent devices that communicate, without a central reasoner, creating little communities to support the user. If the former approach uses all the available sensors being more easily context-aware, the latter is scalable and naturally supports multiple users. In this work we introduce a model for a distributed network of entities in Intelligent Environments. Each node satisfies users' requests through Natural User Interfaces. If a node cannot produce the expected output, it communicates with others in the network, generating paths where the final target is undetermined and intermediate nodes do not understand the request; this is the focus of our work. The system learns parameters and connections in the initial topology. We tested the system in two scenarios. Our approach finds paths close to the optimum with reasonable connections

A near-infrared spectroscopic screening of the red giant populations in omega Centauri

Near-infrared spectra of 21 giants in omega Centauri, spanning the whole range of metallicities observed in this cluster, are presented. This work is part of a coordinated photometric and spectroscopic campaign in the optical and in the infrared, aimed at studying the complex stellar population of omega Centauri and understanding its formation and chemical evolution. By analyzing the several CO and OH molecular bands and atomic lines in the spectra of the selected giants, metal abundances and abundance ratios have been obtained. The existence of three major metallicity regimes at [Fe/H]=-1.6, -1.2 and [Fe/H]<-0.5 has been confirmed. The most metal-rich stars in our sample show a lower (if any) alpha-enhancement when compared to the more metal-poor components, suggesting that they should have formed in a medium significantly polluted by type Ia supernova ejecta. Isotopic carbon abundances have been also inferred, providing an average 13C/12C=4, which clearly indicates that extra-mixing processes occurred in the stellar interiors during the ascent on the Red Giant Branch.Comment: 22 pages, 7 .ps figures. aastex. Accepted for pubilcation in the Astrophysical Journa

Probing the Galactic Bulge with deep Adaptive Optics imaging: the age of NGC 6440

We present first results of a pilot project aimed at exploiting the potentiality of ground based adaptive optics imaging in the near infrared to determine the age of stellar clusters in the Galactic Bulge. We have used a combination of high resolution adaptive optics (ESO-VLT NAOS-CONICA) and wide-field (ESO-NTT-SOFI) photometry of the metal rich globular cluster NGC 6440 located towards the inner Bulge, to compute a deep color magnitude diagram from the tip of the Red Giant Branch down to J~22$, two magnitudes below the Main Sequence Turn Off (TO). The magnitude difference between the TO level and the red Horizontal Branch has been used as an age indicator. It is the first time that such a measurement for a bulge globular cluster has been obtained with a ground based telescope. From a direct comparison with 47 Tuc and with a set of theoretical isochrones, we concluded that NGC 6440 is old and likely coeval to 47 Tuc. This result adds a new evidence that the Galactic Bulge is ~2 Gyr younger at most than the pristine, metal poor population of the Galactic Halo