The GIRAFFE Inner Bulge Survey (GIBS) Gonzalez, O A; Zoccali, M; Vasquez, S ...
Astronomy and astrophysics (Berlin),
12/2015, Volume:
584
Journal Article
Peer reviewed
Open access
We investigate metallicity and alpha-element abundance gradients along a Galactic longitude strip, at latitude b ~ -4degrees, with the aim of providing observational constraints for the structure and ...origin of the Milky Way bulge. To the sample we added another ~400 stars in Baade's Window at (l,b) = (1degree,-4degrees), observed with the identical instrumental configuration: FLAMES GIRAFFE in Medusa mode with HR13 setup. We constructed the metallicity distributions for the entire sample, and for each field individually, in order to investigate the presence of gradients or field-to-field variations in the shape of the distributions. The metallicity distributions in the five fields are consistent with being drawn from a single parent population, indicating the absence of a gradient along the major axis of the Galactic bar. We found no variation in alpha-element abundance distributions between different fields.
Terzan 5 is a globular cluster-like stellar system in the Galactic bulge which has been recently found to harbor two stellar populations with different iron content and probably different ages. This ...discovery suggests that Terzan 5 may be the relic of a primordial building block that contributed to the formation of the Galactic bulge. Here we present a re-determination of the structural parameters (center of gravity, density and surface brightness profiles, total luminosity, and mass) of Terzan 5, as obtained from the combination of high-resolution (ESO-MAD and Hubble Space Telescope ACS-WFC) and wide-field (ESO-WFI) observations. We find that Terzan 5 is significantly less concentrated and more massive than previously thought. Still it has the largest collision rate of any stellar aggregate in the Galaxy. We discuss the impact of these findings on the exceptional population of millisecond pulsars harbored in this stellar system.
The period–metallicity–K-band luminosity (PLK) relation for RR Lyrae stars in 15 Galactic globular clusters and in the Large Magellanic Cloud (LMC) globular cluster Reticulum has been derived. It is ...based on accurate near-infrared (K) photometry combined with Two-Micron All-Sky Survey (2MASS) and other literature data. The PLK relation has been calibrated and compared with the previous empirical and theoretical determinations in literature. The zero point of the absolute calibration has been obtained from the K magnitude of RR Lyr whose distance modulus has been measured via trigonometric parallax with Hubble Space Telescope (HST). Using this relation, we obtain a distance modulus to the LMC of (m−M)0= 18.54 ± 0.15 mag, in good agreement with recent determinations based on the analysis of Cepheid variable stars.
Aims. We use the VVV survey observations in bulge regions close to the Galactic plane to trace the bar inclination at the Galactic latitude b ~ ±1 and to investigate a distinct structure in the ...inner regions of the bar that was previously detected at positive latitude (b = +1). Methods. We use the (J − Ks) colors of the red clump stars to obtain reddening values on 6 × 6 arcmin scale, minimizing the problems arising from differential extinction. Dereddened magnitudes are then used to build the luminosity function of the bulge in regions of ~0.4 sq deg to obtain the mean red clump magnitudes. These are used as distance indicators to trace the bar structure. Results. The luminosity function clearly shows the red clump mean magnitude variation with longitude, as expected from a large scale bar oriented towards us at positive Galactic longitude, with a dereddened magnitude varying from Ks0 = 13.4 at l = −10° to Ks0 = 12.4 at l = +10°. We detect a change in the orientation of the bar in the central regions with |l| < 4° at b = ±1°, in agreement with results obtained at positive latitudes by other authors. Our results are based on a different dataset and at different latitude, which shows that this change in the bar orientation is real. This suggests that there is an inner structure distinct to the large-scale Galactic bar, with a different orientation angle. This inner structure could be a secondary, inner bar, with a semi-major axis of ~500 pc that is symmetric with respect to the Galactic plane.
Context. Multiple stellar populations of different ages and metallicities reside in the Galactic bulge that trace its structure and provide clues to its formation and evolution. Aims. We present the ...near-infrared observations of population II Cepheids in the Galactic bulge from VISTA Variables in the Vía Láctea (VVV) survey. The JHKs photometry together with optical data from Optical Gravitational Lensing Experiment (OGLE) survey provide an independent estimate of the distance to the Galactic centre. The old, metal-poor and low-mass population II Cepheids are also investigated as useful tracers for the structure of the Galactic bulge. Methods. We identify 340 population II Cepheids in the VVV survey Galactic bulge catalogue based on their match with the OGLE-III Catalogue. The single-epoch JH and multi-epoch Ks observations complement the accurate periods and optical (VI) mean-magnitudes from OGLE. The sample consisting of BL Herculis and W Virginis subtypes is used to derive period-luminosity relations after correcting mean-magnitudes for the extinction. Our Ks-band period-luminosity relation, Ks = −2.189(0.056) log (P)−1 + 11.187(0.032), is consistent with published work for BL Herculis and W Virginis variables in the Large Magellanic Cloud. Results. We present a combined OGLE-III and VVV catalogue with periods, classification, mean magnitudes, and extinction for 264 Galactic bulge population II Cepheids that have good-quality Ks-band light curves. The absolute magnitudes for population II Cepheids and RR Lyraes calibrated using Gaia and Hubble Space Telescope parallaxes, together with calibrated magnitudes for Large Magellanic Cloud population II Cepheids, are used to obtain a distance to the Galactic centre, R0 = 8.34 ± 0.03(stat.) ± 0.41(syst.), which changes by + 0.05-0.25 with different extinction laws. While noting the limitation of small number statistics, we find that the present sample of population II Cepheids in the Galactic bulge shows a nearly spheroidal spatial distribution, similar to metal-poor RR Lyrae variables. We do not find evidence of the inclined bar as traced by the metal-rich red-clump stars. Conclusions. Population II Cepheid and RR Lyrae variables follow similar period-luminosity relations and trace the same metal-poor old population in the Galactic bulge. The number density for population II Cepheids is more limited as compared to abundant RR Lyraes but they are bright and exhibit a wide range in period that provides a robust period-luminosity relation for an accurate estimate of the distance to the Galactic centre.
We present the first abundance analysis based on high-resolution infrared (IR) echelle spectra of NGC 6569 and 6624, two moderately reddened globular clusters located in the outer bulge of the ...Galaxy.
We find Fe/H=−0.79 ± 0.02 and −0.69 ± 0.02 dex for NGC 6569 and 6624, respectively, and an average α-element enhancement of ≈+0.43 ± 0.02 and +0.39 ± 0.02 dex, consistent with previous measurements on other metal-rich bulge clusters. We measure accurate radial velocities of 〈v
r〉=−47 ± 4 and +51 ± 3 km s−1 and velocity dispersions of ≈8 and 6 km s−1 for NGC 6569 and 6624, respectively.
Finally, we find very low 12C/13C isotopic ratio (≤7 in NGC 6624 and ≈5 in NGC 6569), confirming the presence of extramixing mechanisms during the red giant branch evolution phase.
Amyotrophic lateral sclerosis (ALS) is considered a multisystem degenerative disease due to its autonomic dysfunction effects. Autonomic cardiac control disorders can be seen in ALS and influence the ...quality of life and the life expectancy of affected individuals. We evaluated heart rate variability in subjects with ALS and with variable lung capacity.
We conducted a prospective cross-sectional study performed in 42 subjects with ALS. The subjects were classified into 2 groups according to their FVC: (FVC > 50% of the predicted value
= 19 and FVC < 50% of the predicted value
= 23). Heart rate was recorded at rest during spontaneous breathing by using a heart rate monitor. Linear indices in the time and frequency domains were analyzed, and non-linear analysis was performed by using Poincaré plots.
The results showed a decrease of heart rate variability in the subjects with lower lung capacity and who needed ventilatory support. Qualitative analysis when using the plots supported the quantitative analysis, wherein the group with a lower lung capacity showed reduced heart rate variability. No significant differences were found in the other heart rate variability indices.
The subjects with ALS and with decreased pulmonary capacity had reduced heart rate variability.
ABSTRACT
Recent wide-area surveys have enabled us to study the Milky Way with unprecedented detail. Its inner regions, hidden behind dust and gas, have been partially unveiled with the arrival of ...near-infrared (IR) photometric and spectroscopic data sets. Among recent discoveries, there is a population of low-mass globular clusters, known to be missing, especially towards the Galactic bulge. In this work, five new low-luminosity globular clusters located towards the bulge area are presented. They were discovered by searching for groups in the multidimensional space of coordinates, colours, and proper motions from the Gaia EDR3 catalogue and later confirmed with deeper VVV survey near-IR photometry. The clusters show well-defined red giant branches and, in some cases, horizontal branches with their members forming a dynamically coherent structure in proper motion space. Four of them were confirmed by spectroscopic follow-up with the MUSE instrument on the ESO VLT. Photometric parameters were derived, and when available, metallicities, radial velocities, and orbits were determined. The new clusters Gran 1 and 5 are bulge globular clusters, while Gran 2, 3 and 4 present halo-like properties. Preliminary orbits indicate that Gran 1 might be related to the Main Progenitor, or the so-called ‘low-energy’ group, while Gran 2, 3 and 5 appears to follow the Gaia-Enceladus/Sausage structure. This study demonstrates that the Gaia proper motions, combined with the spectroscopic follow-up and colour–magnitude diagrams, are required to confirm the nature of cluster candidates towards the inner Galaxy. High stellar crowding and differential extinction may hide other low-luminosity clusters.
ABSTRACT
Like most spiral galaxies, the Milky Way contains a population of blue, metal-poor globular clusters and another of red, metal-rich ones. Most of the latter belong to the bulge, and ...therefore they are poorly studied compared to the blue (halo) ones because they suffer higher extinction and larger contamination from field stars. These intrinsic difficulties, together with a lack of low-mass bulge globular clusters, are reasons to believe that their census is not complete yet. Indeed, a few new clusters have been confirmed in the last few years. One of them is VVV CL001, the subject of the present study. We present a new spectroscopic analysis of the recently confirmed globular cluster VVV CL001, made by means of MUSE@VLT integral field data. Individual spectra were extracted for stars in the VVV CL001 field. Radial velocities were derived by cross-correlation with synthetic templates. Coupled with proper motions from the VVV (VISTA Variables in the Vía Láctea) survey, these data allow us to select 55 potential cluster members, for which we derive metallicities using the public code
The Cannon. The mean radial velocity of the cluster is Vhelio = −324.9 ± 0.8 km s−1, as estimated from 55 cluster members. This high velocity, together with a low metallicity Fe/H = −2.04 ± 0.02 dex, suggests that VVV CL001 could be a very old cluster. The estimated distance is d = 8.23 ± 0.46 kpc, placing the cluster in the Galactic bulge. Furthermore, both its current position and the orbital parameters suggest that VVV CL001 is most probably a bulge globular cluster.
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