Abundance Patterns in Stars in the Bulge and Galactic Center

We discuss oxygen and iron abundance patterns in K and M red-giant members of the Galactic bulge and in the young and massive M-type stars inhabiting the very center of the Milky Way. The abundance results from the different bulge studies in the literature, both in the optical and the infrared, indicate that the [O/Fe]-[Fe/H] relation in the bulge does not follow the disk relation, with [O/Fe] values falling above those of the disk. Based on these elevated values of [O/Fe] extending to large Fe abundances, it is suggested that the bulge underwent a rapid chemical enrichment with perhaps a top-heavy initial mass function. The Galactic Center stars reveal a nearly uniform and slightly elevated (relative to solar) iron abundance for a studied sample which is composed of 10 red giants and supergiants. Perhaps of more significance is the fact that the young Galactic Center M-type stars show abundance patterns that are reminiscent of those observed for the bulge population and contain enhanced abundance ratios of alpha-elements relative to either the Sun or Milky Way disk at near-solar metallicities.Comment: requires iaus.cls; to appear in Formation and Evolution of Galaxy Bulges, Proceedings IAU Symposium No. 245, 2007, M. Bureau et al. eds., in pres

HST NICMOS Photometry of the reddened bulge globular clusters NGC 6528, Terzan 5, Liller 1, UKS 1 and Terzan 4

We present results from NICMOS Hubble Space Telescope observations of the reddened bulge globular clusters NGC 6528, Terzan 5, Liller 1, UKS 1 and Terzan 4, obtained through the filters F110W and F160W (nearly equivalent to J and H). For the first time the turnoff region of Liller 1 and the main sequence of Terzan 5 and Terzan 4 are reached, as well as the horizontal branch of UKS 1. The magnitude difference between the turnoff and the red horizontal branch $\Delta m_{110}=m_{110}^{HB}- m_{110}^{TO}$ is used as an age indicator. From comparisons with new isochrones in the NICMOS photometric system, we conclude that the two metal-rich clusters NGC 6528 and Terzan 5 are coeval within uncertainties ($\sim 20$) with 47 Tucanae. Liller 1 and UKS 1 are confirmed as metal-rich globular clusters. Terzan 4 is confirmed as an interesting case of a metal-poor cluster in the bulge with a blue horizontal branch.Comment: 7 pages, 6 figures, accepted for publication in A&

The Red Giant Branch in Near-Infrared Colour-Magnitude Diagrams. II: The luminosity of the Bump and the Tip

We present new empirical calibrations of the Red Giant Branch (RGB) Bump and Tip based on a homogeneous near-Infrared database of 24 Galactic Globular Clusters. The luminosities of the RGB Bump and Tip in the J, H and K bands and their dependence on the cluster metallicity have been studied, yielding empirical relationships. By using recent transformations between the observational and theoretical planes, we also derived similar calibrations in terms of bolometric luminosity. Direct comparison between updated theoretical models and observations show an excellent agreement. The empirical calibration of the RGB Tip luminosity in the near-Infrared passbands presented here is a fundamental tool to derive distances to far galaxies beyond the Local Group, in view of using the new ground-based adaptive optics facilities and, in the next future, the James Webb Space Telescope.Comment: 7 pages, 7 figures, accepted for publication in MNRA

Mass Loss From Planetary Nebulae in Elliptical Galaxies

Early-type galaxies possess a dilute hot (2-10E6 K) gas that is probably the thermalized ejecta of the mass loss from evolving stars. We investigate the processes by which the mass loss from orbiting stars interacts with the stationary hot gas for the case of the mass ejected in a planetary nebula event. Numerical hydrodynamic simulations show that at first, the ejecta expands nearly symmetrically, with an upstream bow shock in the hot ambient gas. At later times, the flow past the ejecta creates fluid instabilities that cause about half of the ejecta to separate and the other half to flow more slowly downstream in a narrow wake. When radiative cooling is included, most of the material in the wake (>80%) remains below 1E5 K while the separated ejecta is hotter (1E5-1E6 K). The separated ejecta is still less than one-quarter the temperature of the ambient medium and the only way it will reach the temperature of the ambient medium is through turbulent mixing (after the material has left the grid). These calculations suggest that a significant fraction of the planetary nebula ejecta may not become part of the hot ambient material. This is in contrast to our previous calculations for continuous mass loss from giant stars in which most of the mass loss became hot gas. We speculate that detectable OVI emission may be produced, but more sophisticated calculations will be required to determine the emission spectrum and to better define the fraction of cooled material.Comment: 34 pages with 20 figures. Higher quality figures are in the ApJ versio

Zinc abundances in Galactic bulge field red giants: implications for DLA systems

Zinc in stars is an important reference element because it is a proxy to Fe in studies of damped Lyman-alpha systems, permitting a comparison of chemical evolution histories of bulge stellar populations and DLAs. In terms of nucleosynthesis, it behaves as an alpha element because it is enhanced in metal-poor stars. The aim of this work is to derive the iron-peak element Zn abundances in 56 bulge giants from high resolution spectra. These results are compared with data from other bulge samples, as well as from disk and halo stars, and damped Lyman-alpha systems, in order to better understand the chemical evolution in these environments. High-resolution spectra were obtained using FLAMES+UVES on the Very Large Telescope. We find [Zn/Fe]=+0.24+-0.02 in the range -1.3 < [Fe/H] < -0.5 and [Zn/Fe]=+0.06+-0.02 in the range -0.5 < [Fe/H] -0.1, it shows a spread of -0.60 < [Zn/Fe] < +0.15, with most of these stars having low [Zn/Fe]<0.0. These low zinc abundances at the high metallicity end of the bulge define a decreasing trend in [Zn/Fe] with increasing metallicities. A comparison with Zn abundances in DLA systems is presented, where a dust-depletion correction was applied for both Zn and Fe. Finally, we present a chemical evolution model of Zn enrichment in massive spheroids, representing a typical classical bulge.Comment: Accepted in Astronomy & Astrophysics, in press Date of acceptance: 13/05/2015. 19 pages, 14 Figs in Astronomy & Astrophysics, 201

Proper motions in the VVV Survey: Results for more than 15 million stars across NGC 6544

Context: In the last six years, the VVV survey mapped 562 sq. deg. across the bulge and southern disk of the Galaxy. However, a detailed study of these regions, which includes $\sim 36$ globular clusters (GCs) and thousands of open clusters is by no means an easy challenge. High differential reddening and severe crowding along the line of sight makes highly hamper to reliably distinguish stars belonging to different populations and/or systems. Aims: The aim of this study is to separate stars that likely belong to the Galactic GC NGC 6544 from its surrounding field by means of proper motion (PM) techniques. Methods: This work was based upon a new astrometric reduction method optimized for images of the VVV survey. Results: Photometry over the six years baseline of the survey allowed us to obtain a mean precision of $\sim0.51$ mas/yr, in each PM coordinate, for stars with Ks < 15 mag. In the area studied here, cluster stars separate very well from field stars, down to the main sequence turnoff and below, allowing us to derive for the first time the absolute PM of NGC 6544. Isochrone fitting on the clean and differential reddening corrected cluster color magnitude diagram yields an age of $\sim$ 11-13 Gyr, and metallicity [Fe/H] = -1.5 dex, in agreement with previous studies restricted to the cluster core. We were able to derive the cluster orbit assuming an axisymmetric model of the Galaxy and conclude that NGC 6544 is likely a halo GC. We have not detected tidal tail signatures associated to the cluster, but a remarkable elongation in the galactic center direction has been found. The precision achieved in the PM determination also allows us to separate bulge stars from foreground disk stars, enabling the kinematical selection of bona fide bulge stars across the whole survey area. Our results show that VVV data is perfectly suitable for this kind of analysis.Comment: 13 pages, 12 figures, accepted in A&

Surgical site infections in treatment of musculoskeletal tumors: experience from a single oncologic orthopedic institution

Objective: Limb-sparing surgery is the mainstay treatment for musculoskeletal tumors thanks to advances in surgical techniques, imaging modalities and multimodal therapies. As patients survive longer, plastic reconstructive procedures and revision surgery are increasingly required after tumor excision. Infection rate is reported to be up to 20% after prosthetic replacement and 30-44% after pelvic resection. The purpose of this study was to investigate the incidence of surgical site infections (SSIs), identifying the causative microrganisms related to specific surgical procedures and significant risk factors for SSIs. Methods: We retrospectively reviewed 723 interventions performed between 2009 and 2015 for oncological conditions. Non neoplastic lesions, aseptic wound complications, non-skeletally mature patients were excluded. Standardised antibiotic prophylaxis was used for different surgical procedures and maintained until removal of surgical drains. Results: Without considering tumor types and surgical sites, the overall infection rate was 8.7% (63/724). Infection occurred in prosthetic reconstruction with an incidence rate of 7.8%, whereas almost half of patients having undergone pelvic surgery got infected and about 20% of patients with spinal surgery and amputations were infected. Pelvic location, malignancy and radiotherapy were related to a major risk of SSI. The causative pathogens were detected in all examined cases. The most frequent pathogens detected by culture included Staphylococcus aureus (27 cases, 47.4%) and S. epidermidis (10 cases, 17.5%). Among the S. aureus cases, 10/27 cases (37%) were methicillin-resistant S. aureus (MRSA). Sixty-three out of 130 microbial isolations (47.7%) were nosocomial ALERT organisms. Conclusion: Oncologic orthopedic surgery is burdened by frequent and challenging SSIs because of extensive soft tissues dissection, long operative times and poor skin conditions. Patients are immunosuppressed and often have concomitant comorbidities predisposing to SSIs. Monitoring of local bacterial aetiology of SSIs could help orthopedic oncologic specialized centres in achieving the optimisation of antibiotic prophylactic regimens