The Infrared Ca II triplet as metallicity indicator

From observations of almost 500 RGB stars in 29 Galactic open and globular clusters, we have investigated the behaviour of the infrared Ca II triplet (8498, 8542 and 8662 \AA) in the age range 13$\leq$Age/Gyr$\leq$0.25 and the metallicity range $-2.2\leq$ [Fe/H] $\leq$+0.47. These are the widest ranges of ages and metallicities in which the behaviour of the Ca II triplet lines has been investigated in a homogeneous way. We report the first empirical study of the variation of the CaII triplet lines strength, for given metallicities, with respect to luminosity. We find that the sequence defined by each cluster in the Luminosity-$\Sigma$Ca plane is not exactly linear. However, when only stars in a small magnitude interval are observed, the sequences can be considered as linear. We have studied the the Ca II triplet lines on three metallicities scales. While a linear correlation between the reduced equivalent width ($W'_V$ or $W'_I$) versus metallicity is found in the \citet{cg97} and \citet{ki03} scales, a second order term needs to be added when the \citet{zw84} scale is adopted. We investigate the role of age from the wide range of ages covered by our sample. We find that age has a weak influence on the final relationship. Finally, the relationship derived here is used to estimate the metallicities of three poorly studied open clusters: Berkeley 39, Trumpler 5 and Collinder 110. For the latter, the metallicity derived here is the first spectroscopic estimate available.Comment: 52 pages, 16 figures, accepted for publication in Astronomical Journa

Kinematics of the Galactic Globular Cluster System: New Radial Velocities for Clusters in the Direction of the Inner Galaxy

HIRES on the Keck I telescope has been used to measure the first radial velocities for stars belonging to eleven, heavily-reddened globular clusters in the direction of the inner Galaxy. The question of kinematic substructuring among the Galactic globular cluster system is investigated using an updated catalog of globular cluster distances, metallicities and velocities. It is found that the population of metal-rich globular clusters shows significant rotation at all Galactocentric radii. For the metal-rich clusters within 4 kpc of the Galactic center, the measured rotation velocity and line-of-sight velocity dispersion are similar to those of bulge field stars. We investigate claims that the metal-rich clusters are associated with the central Galactic bar by comparing the kinematics of the innermost clusters to that of the atomic hydrogen in the inner Galaxy. The longitude-velocity diagram of both metal-rich and metal-poor clusters bears a remarkable similarity to that of the gas, including the same non-circular motions which have traditionally been interpreted as evidence for a Galactic bar, or, alternatively, a non-axisymmetric bulge. However, uncertainties in the existing three-dimensional Galactocentric positions for most of the clusters do not yet allow an unambiguous discrimination between the competing scenarios of membership in a rigidly rotating bar, or in a bulge which is an oblate isotropic rotator. We conclude that the majority of metal-rich clusters within the central 4 kpc of the Galaxy are probably associated with the bulge/bar, and not the thick disk. (ABRIDGED)Comment: 18 pages, including 7 of 13 postscript figures. Figures 1-6 available at http://astro.caltech.edu/~pc. Accepted for publication in the Astronomical Journa

CCD Photometry of Galactic Globular Clusters. IV. The NGC 1851 RR Lyraes

The variable star population of the galactic globular cluster NGC 1851 (C0512-400) has been studied by CCD photometry, from observations made in the B, V, and I bands during 1993-4. Light curves are presented for 29 variables, seven of which are new discoveries. The behavior of the RR lyraes in the period-temperature diagram appears normal when compared to clusters which bracket the NGC 1851 metallicity. Reddening and metallicity are re-evaluated, with no compelling evidence to change from accepted values. Photometry for stars within an annulus with radii 80 and 260 arcsec agrees to better than 0.02 mag in all colors with extensive earlier photometry, to at least V = 18.5. Instability strip boundary positions for several clusters shows a trend for the red boundary to move to redder colors as the metallicity increases.Comment: 29 pages, 9 figures, accepted by A.

On the Iron content of NGC 1978 in the LMC: a metal rich, chemically homogeneous cluster

We present a detailed abundance analysis of giant stars in NGC 1978, a massive, intermediate-age stellar cluster in the Large Magellanic Cloud, characterized by a high ellipticity and suspected to have a metallicity spread. We analyzed 11 giants, all cluster members, by using high resolution spectra acquired with the UVES/FLAMES spectrograph at the ESO-Very Large Telescope. We find an iron content of [Fe/H]=-0.38 dex with very low (0.07 dex) dispersion, and a mean heliocentric radial velocity Vr=293.1 (with an error of 0.9 km/s) and a velocity dispersion (3.1 km/s), thus excluding the presence of a significant metallicity, as well as velocity, spread within the cluster.Comment: 14 pages, 4 figures, accepted for publication by Apj

Variable Stars in the Unusual, Metal-Rich Globular Cluster NGC 6388

We have undertaken a search for variable stars in the metal-rich globular cluster NGC 6388 using time-series BV photometry. Twenty-eight new variables were found in this survey, increasing the total number of variables found near NGC 6388 to ~57. A significant number of the variables are RR Lyrae (~14), most of which are probable cluster members. The periods of the fundamental mode RR Lyrae are shown to be unusually long compared to metal-rich field stars. The existence of these long period RRab stars suggests that the horizontal branch of NGC 6388 is unusually bright. This implies that the metallicity-luminosity relationship for RR Lyrae stars is not universal if the RR Lyrae in NGC 6388 are indeed metal-rich. We consider the alternative possibility that the stars in NGC 6388 may span a range in [Fe/H]. Four candidate Population II Cepheids were also found. If they are members of the cluster, NGC 6388 would be the most metal-rich globular cluster to contain Population II Cepheids. The mean V magnitude of the RR Lyrae is found to be 16.85+/-0.05 resulting in a distance of 9.0 to 10.3 kpc, for a range of assumed values of for RR Lyrae. We determine the reddening of the cluster to be E(B-V)=0.40+/-0.03 mag, with differential reddening across the face of the cluster. We discuss the difficulty in determining the Oosterhoff classification of NGC 6388 and NGC 6441 due to the unusual nature of their RR Lyrae, and address evolutionary constraints on a recent suggestion that they are of Oosterhoff type II.Comment: 35 pages, 16 figures, emulateapj5/apjfonts style. Astronomical Journal, in press. We recommend the interested reader to download instead the preprint with full-resolution figures, which can be found at http://www.noao.edu/noao/staff/pritzl/clusters.htm

Near Infrared properties of 12 Globular Clusters toward the inner Bulge of the Galaxy

We present near-IR Colour-Magnitude diagrams and physical parameters for a sample of 12 galactic globular clusters located toward the inner Bulge region. For each cluster we provide measurements of the reddening, distance, photometric metallicity, luminosity of the horizontal branch red clump, and of the red giant branch bump and tip. The sample discussed here together with that presented in Valenti, Ferraro & Origlia (2007) represent the largest homogeneous catalog of Bulge globular clusters (comprising ~ 80% of the entire Bulge cluster population) ever studied. The compilation is available in electronic form on the World Wide Web (http://www.bo.astro.it/~GC/ir_archive)Comment: 2 pages, 13 figures, 4 tables, accepted for publication in MNRA

An international multidisciplinary consensus statement on fasting before procedural sedation in adults and children

The multidisciplinary International Committee for the Advancement of Procedural Sedation presents the first fasting and aspiration prevention recommendations specific to procedural sedation, based on an extensive review of the literature. These were developed using Delphi methodology and assessment of the robustness of the available evidence. The literature evidence is clear that fasting, as currently practiced, often substantially exceeds recommended time thresholds and has known adverse consequences, for example, irritability, dehydration and hypoglycaemia. Fasting does not guarantee an empty stomach, and there is no observed association between aspiration and compliance with common fasting guidelines. The probability of clinically important aspiration during procedural sedation is negligible. In the post-1984 literature there are no published reports of aspiration-associated mortality in children, no reports of death in healthy adults (ASA physical status 1 or 2) and just nine reported deaths in adults of ASA physical status 3 or above. Current concerns about aspiration are out of proportion to the actual risk. Given the lower observed frequency of aspiration and mortality than during general anaesthesia, and the theoretical basis for assuming a lesser risk, fasting strategies in procedural sedation can reasonably be less restrictive. We present a consensus-derived algorithm in which each patient is first risk-stratified during their pre-sedation assessment, using evidence-based factors relating to patient characteristics, comorbidities, the nature of the procedure and the nature of the anticipated sedation technique. Graded fasting precautions for liquids and solids are then recommended for elective procedures based upon this categorisation of negligible, mild or moderate aspiration risk. This consensus statement can serve as a resource to practitioners and policymakers who perform and oversee procedural sedation in patients of all ages, worldwide

Structures in surface-brightness profiles of LMC and SMC star clusters: evidence of mergers?

The LMC and SMC are rich in binary star clusters, and some mergers are expected. It is important to characterize single clusters, binary clusters and candidates to mergers. We selected a sample of star clusters in each Cloud with this aim. Surface photometry of 25 SMC and 22 LMC star clusters was carried with the ESO Danish 1.54 m telescope. 23 clusters were observed for the first time for these purposes. We fitted Elson, Fall and Freeman (1987, EFF) profiles to the data, deriving structural parameters, luminosities and masses. We also use isophotal maps to constrain candidates to cluster interactions.} {The structural parameters, luminosities and masses presented good agreement with those in the literature. Three binary clusters in the sample have a double profile. Four clusters (NGC 376, K 50, K 54 and NGC 1810) do not have companions and present as well important deviations from EFF profiles. The present sample contains blue and red Magellanic clusters. Extended EFF profiles were detected in some blue clusters. We find evidence that important deviations from the body of EFF profiles might be used as a tool to detect cluster mergers.Comment: 16 pages and 8 figures. Accepted by A&

Chemical Abundances Of Three Metal-Poor Globular Clusters (NGC 6287, NGC 6293, And NGC 6541) In The Inner Halo

We present a chemical abundance study of three inner old halo clusters NGC 6287, NGC 6293, and NGC 6541, finding [Fe/H] = -2.01 +/- 0.05, -1.99 +/- 0.02, and -1.76 +/- 0.02, respectively, and our metallicity measurements are in good agreement with previous estimates. The mean alpha-element abundances of our program clusters are in good agreement with other globular clusters, confirming previous results. However, the individual alpha-elements appear to follow different trends. The silicon abundances of the inner halo clusters appear to be enhanced and the titanium abundances appear to be depleted compared to the intermediate halo clusters. Our results also appear to oppose to those of metal-rich bulge giants studied by McWilliam and Rich, who found that bulge giants are titanium enhanced and silicon deficient. In particular, [Si/Ti] ratios appear to be related to Galactocentric distances,in the sense that [Si/Ti] ratios decrease with Galactocentric distance. We propose that contributions from different masses of the SNe II progenitors that enriched proto-globular cluster clouds' elemental abundances and the different initial physical environments surrounding the proto-globular clusters clouds are responsible for this gradient in [Si/Ti] ratios versus Galactocentric distances of the "old halo" globular clusters. On the other hand, our program clusters' enhanced s-process elemental abundances suggest that the formation timescale of our program clusters might be as short as a few times 10^8 yr after the star formation is initiated in the Galaxy's central regions, if the s-process site is intermediate mass AGB stars.Comment: Accepted for publication in AJ (Sept. 2002

A Database of 2MASS Near-Infrared Colors of Magellanic Cloud Star Clusters

The (rest-frame) near-IR domain contains important stellar population diagnostics and is often used to estimate masses of galaxies at low as well as high redshifts. However, many stellar population models are still relatively poorly calibrated in this part of the spectrum. To allow an improvement of this calibration we present a new database of integrated near-infrared JHKs magnitudes for 75 star clusters in the Magellanic Clouds, using the 2-Micron All-Sky Survey (2MASS). The majority of the clusters in our sample have robust age and metallicity estimates from color-magnitude diagrams available in the literature, and populate a range of ages from 10 Myr to 15 Gyr and a range in [Fe/H] from -2.17 to +0.01 dex. A comparison with matched star clusters in the 2MASS Extended Source Catalog (XSC) reveals that the XSC only provides a good fit to the unresolved component of the cluster stellar population. We also compare our results with the often-cited single-channel JHK photometry of Persson and collaborators, and find significant differences, especially for their 30"-diameter apertures up to ~2.5 mag in the K-band, more than 1 mag in J-K, and up to 0.5 mag in H-K. Using simulations to center apertures based on maximum light throughput (as performed by Persson et al, we show that these differences can be attributed to near-IR-bright cluster stars (e.g., Carbon stars) located away from the true center of the star clusters. The wide age and metallicity coverage of our integrated JHKs photometry sample constitutes a fundamental dataset for testing population synthesis model predictions, and for direct comparison with near-IR observations of distant stellar populations.Comment: AJ August 2006 issue, 67 pages, 8 tables, 17 figure