The Near-Infrared Photometric Properties of Bright Giants in the Central Regions of the Galactic Bulge

Images recorded through broad (J, H, K), and narrow (CO, and 2.2micron continuum) band filters are used to investigate the photometric properties of bright (K < 13.5) stars in a 6 x 6 arcmin field centered on the SgrA complex. The giant branch ridgelines in the (K, J-K) and (K, H-K) color-magnitude diagrams are well matched by the Baade's Window (BW) M giant sequence if the mean extinction is A_K ~ 2.8 mag. Extinction measurements for individual stars are estimated using the M_K versus infrared color relations defined by M giants in BW, and the majority of stars have A_K between 2.0 and 3.5 mag. The extinction is locally high in the SgrA complex, where A_K ~ 3.1 mag. Reddening-corrected CO indices, CO_o, are derived for over 1300 stars with J, H, and K brightnesses, and over 5300 stars with H and K brightnesses. The distribution of CO_o values for stars with K_o between 11.25 and 7.25 can be reproduced using the M_K versus CO_o relation defined by M giants in BW. The data thus suggest that the most metal-rich giants in the central regions of the bulge and in BW have similar photometric properties and 2.3micron CO strengths. Hence, it appears that the central region of the bulge does not contain a population of stars that are significantly more metal-rich than what is seen in BW.Comment: 29 pages, including 14 figure

Theory of Stellar Population Synthesis with an application to N-Body simulations

Aims. We present here a new theoretical approach to population synthesis. The aim is to predict colour magnitude diagrams (CMDs) for huge numbers of stars. With this method we generate synthetic CMDs for N-body simulations of galaxies. Sophisticated hydrodynamic N-body models of galaxies require equal quality simulations of the photometric properties of their stellar content. The only prerequisite for the method to work is very little information on the star formation and chemical enrichment histories, i.e. the age and metallicity of all star-particles as a function of time. The method takes into account the gap between the mass of real stars and that of the star-particles in N-body simulations, which best correspond to the mass of star clusters with different age and metallicity, i.e. a manifold of single stellar sopulations (SSP). Methods. The theory extends the concept of SSP to include the phase-space (position and velocity) of each star. Furthermore, it accelerates the building up of simulated CMD by using a database of theoretical SSPs that extends to all ages and metallicities of interest. Finally, it uses the concept of distribution functions to build up the CMD. The technique is independent of the mass resolution and the way the N-body simulation has been calculated. This allows us to generate CMDs for simulated stellar systems of any kind: from open clusters to globular clusters, dwarf galaxies, or spiral and elliptical galaxies. Results. The new theory is applied to an N-body simulation of a disc galaxy to test its performance and highlight its flexibility.Comment: accepted for publication in A&

Lausannevirus Seroprevalence among Asymptomatic Young Adults.

Objectives: The giant Lausannevirus was recently identified as a parasite of amoeba that replicates rapidly in these professional phagocytes. This study aimed at assessing Lausannevirus seroprevalence among asymptomatic young men in Switzerland and hopefully identifying possible sources of contact with this giant virus. Methods: The presence of anti-Lausannevirus antibodies was assessed in sera from 517 asymptomatic volunteers who filled a detailed questionnaire. The coreactivity between Lausannevirus and amoeba-resisting bacteria was assessed. Results: Lausannevirus prevalence ranged from 1.74 to 2.51%. Sporadic condom use or multiple sexual partners, although frequent (53.97 and 60.35%, respectively), were not associated with anti-Lausannevirus antibodies. On the contrary, frequent outdoor sport practice as well as milk consumption were significantly associated with positive Lausannevirus serologies (p = 0.0066 and 0.028, respectively). Coreactivity analyses revealed an association between Criblamydia sequanensis (an amoeba-resisting bacterium present in water environments) and Lausannevirus seropositivity (p = 0.001). Conclusions: Lausannevirus seroprevalence is low in asymptomatic Swiss men. However, the association between virus seropositivity and frequent sport practice suggests that this member of the Megavirales may be transmitted by aerosols and/or exposure to specific outdoor environments. Milk intake was also associated with seropositivity. Whether the coreactivity observed for C. sequanensis and Lausannevirus reflects a common mode of acquisition or some unexpected cross-reactivity remains to be determined. © 2013 S. Karger AG, Basel

Clues on the evolution of the Carina dwarf spheroidal galaxy from the color distribution of its red giant stars

The thin red giant branch (RGB) of the Carina dwarf spheroidal galaxy appears at first sight quite puzzling and seemingly in contrast with the presence of several distinct bursts of star formation. In this Letter, we provide a measurement of the color spread of red giant stars in Carina based on new BVI wide-field observations, and model the width of the RGB by means of synthetic color-magnitude diagrams. The measured color spread, Sigma{V-I}=0.021 +/- 0.005, is quite naturally accounted for by the star-formation history of the galaxy. The thin RGB appears to be essentially related to the limited age range of its dominant stellar populations, with no need for a metallicity dispersion at a given age. This result is relatively robust with respect to changes in the assumed age-metallicity relation, as long as the mean metallicity over the galaxy lifetime matches the observed value ([Fe/H] = -1.91 +/- 0.12 after correction for the age effects). This analysis of photometric data also sets some constraints on the chemical evolution of Carina by indicating that the chemical abundance of the interstellar medium in Carina remained low throughout each episode of star formation even though these episodes occurred over many Gyr.Comment: 4 pages, 3 figures, accepted for publication in the Astrophysical Journal Letter

Lupus-TR-3b: A Low-Mass Transiting Hot Jupiter in the Galactic Plane?

We present a strong case for a transiting Hot Jupiter planet identified during a single-field transit survey towards the Lupus Galactic plane. The object, Lupus-TR-3b, transits a V=17.4 K1V host star every 3.91405d. Spectroscopy and stellar colors indicate a host star with effective temperature 5000 +/- 150K, with a stellar mass and radius of 0.87 +/- 0.04M_sun and 0.82 +/- 0.05R_sun, respectively. Limb-darkened transit fitting yields a companion radius of 0.89 +/- 0.07R_J and an orbital inclination of 88.3 +1.3/-0.8 deg. Magellan 6.5m MIKE radial velocity measurements reveal a 2.4 sigma K=114 +/- 25m/s sinusoidal variation in phase with the transit ephemeris. The resulting mass is 0.81 +/- 0.18M_J and density 1.4 +/- 0.4g/cm^3. Y-band PANIC image deconvolution reveal a V>=21 red neighbor 0.4'' away which, although highly unlikely, we cannot conclusively rule out as a blended binary with current data. However, blend simulations show that only the most unusual binary system can reproduce our observations. This object is very likely a planet, detected from a highly efficient observational strategy. Lupus-TR-3b constitutes the faintest ground-based detection to date, and one of the lowest mass Hot Jupiters known.Comment: 4 pages, 4 figures, accepted for publication in ApJ

The Peak Brightness and Spatial Distribution of AGB Stars Near the Nucleus of M32

The bright stellar content near the center of the Local Group elliptical galaxy M32 is investigated with 0.12 arcsec FWHM H and K images obtained with the Gemini Mauna Kea telescope. Stars with K = 15.5, which are likely evolving near the tip of the asymptotic giant branch (AGB), are resolved to within 2 arcsec of the nucleus, and it is concluded that the peak stellar brightness near the center of M32 is similar to that in the outer regions of the galaxy. Moreover, the projected density of bright AGB stars follows the visible light profile to within 2 arcsec of the nucleus, indicating that the brightest stars are well mixed throughout the galaxy. Thus, there is no evidence for an age gradient, and the radial variations in spectroscopic indices and ultraviolet colors that have been detected previously must be due to metallicity and/or some other parameter. We suggest that either the bright AGB stars formed as part of a highly uniform and coherent galaxy-wide episode of star formation, or they originated in a separate system that merged with M32.Comment: 9 pages of text, 3 figures. ApJ (Letters) in pres

Dwarf Cepheids in the Carina Dwarf Spheroidal Galaxy

We have discovered 20 dwarf Cepheids (DC) in the Carina dSph galaxy from the analysis of individual CCD images obtained for a deep photometric study of the system. These short-period pulsating variable stars are by far the most distant (~100 kpc) and faintest (V ~ 23.0) DCs known. The Carina DCs obey a well-defined period-luminosity relation, allowing us to readily distinguish between overtone and fundamental pulsators in nearly every case. Unlike RR Lyr stars, the pulsation mode turns out to be uncorrelated with light-curve shape, nor do the overtone pulsators tend towards shorter periods compared to the fundamental pulsators. Using the period-luminosity (PL) relations from Nemec et al. (1994 AJ, 108, 222) and McNamara (1995, AJ, 109, 1751), we derive (m-M)_0 = 20.06 +/- 0.12, for E(B-V) = 0.025 and [Fe/H] = -2.0, in good agreement with recent, independent estimates of the distance/reddening of Carina. The error reflects the uncertainties in the DC distance scale, and in the metallicity and reddening of Carina. The frequency of DCs among upper main sequence stars in Carina is approximately 3%. The ratio of dwarf Cepheids to RR Lyr stars in Carina is 0.13 +/- 0.10, though this result is highly sensitive to the star-formation history of Carina and the evolution of the Horizontal Branch. We discuss how DCs may be useful to search effectively for substructure in the Galactic halo out to Galactocentric distances of ~100 kpc.Comment: 20 pages of text, 7 figure

An Examination of Student and Faculty Perceptions Regarding Music Education Transfer Student Preparedness and Experiences

Transfer students account for growing numbers in four-year music education programs. To better understand this increasing population of students, researchers employed parallel method design. One strand investigated music education faculty members’ (n = 83) perceptions of transfer student preparedness, procedures, and expectations to understand admissions processes (e.g., curricula, assessments) employed to evaluate incoming transfer students. The other strand examined music education transfer students’ (n = 12) academic, social, and personal preparedness to study music education in a comprehensive four-year music education program. The following research questions served as a guide for data collection and analysis: (a) What themes emerged for students throughout the investigation of the transfer process? (b) What are transfer students’ perceptions of academic and musical preparedness once making the transition to four-year institutions? and (c) What are college professors’ perceptions of transfer students’ academic and musical preparedness upon arrival at four-year institutions? Findings from both student and faculty perspectives suggest that transfer students exhibit three common concerns throughout the transfer process. These concerns were academic, social, and personal. Further, transfer students’ preparedness also emerged as a theme mentioned by music faculty as an obstacle for incoming students. Themes also included performance on departmental diagnostic assessments, various modes of communication among music faculty (i.e., applied, classroom), students, and university/college administrative personnel. Researchers provide an analysis and suggestions for addressing these concerns from multiple perspectives as well as suggestions for future research

Re-examination of the possible tidal stream in front of the LMC

It has recently been suggested that the stars in a vertical extension of the red clump feature seen in LMC color-magnitude diagrams could belong to a tidal stream of material located in front of that galaxy. If this claim is correct, this foreground concentration of stars could contribute significantly to the rate of gravitational microlensing events observed in the LMC microlensing experiments. Here we present radial velocity measurements of stars in this so-called ``vertical red clump'' (VRC) population. The observed stellar sample, it transpires, has typical LMC kinematics. It is shown that it is improbable that an intervening tidal stream should have the same distribution of radial velocities as the LMC, which is consistent with an earlier study that showed that the VRC feature is more likely a young stellar population in the main body of that galaxy. However, the kinematic data do not discriminate against the possibility that the VRC is an LMC halo population.Comment: 10 pages, 3 figures, 1 table. Accepted for publication in ApJ

Baade's red sheet resolved into stars with HST in the Blue Compact Dwarf Galaxy VII Zw 403

HST WFPC2 observations of the nearby Blue Compact Dwarf Galaxy VII~Zw~403 (= UGC 6456) resolve single stars down to M$_I$$\approx$-2.5, deep enough to identify red giants. This population has a more uniform spatial distribution than the young main-sequence stars and supergiants, forming the structure known as "Baade's red sheet". We conclude that VII~Zw~403 is not a primeval galaxy.Comment: submitted to: ApJ Letter