scholarly journals Detailed near-IR stellar abundances of red giants in the Inner Bulge and Galactic Center

2017 ◽  
Vol 13 (S334) ◽  
pp. 82-85
Author(s):  
N. Ryde ◽  
R. M. Rich ◽  
B. Thorsbro ◽  
M. Schultheis ◽  
T. K. Fritz ◽  
...  
Keyword(s):  
Stellar Population ◽  
Galactic Center ◽  
Galactic Plane ◽  
Star Cluster ◽  
High Dispersion ◽  
Red Giants ◽  
Galactic Bulge ◽  
Stellar Abundances ◽  
Near Ir ◽  
K Band

AbstractOwing to their extreme crowding and high and variable extinction, stars in the Galactic Bulge, within ±2° of the Galactic plane, and especially those in the Nuclear Star Cluster, have only rarely been targeted for an analyses of their detailed abundances. There is also some disagreement about the high end of the abundance scale for these stars. It is now possible to obtain high dispersion, high S/N spectra in the infrared K band (~2.0 − 2.4 µm) for these giants; we report our progress at Keck and VLT in using these spectra to infer the composition of this stellar population.

scholarly journals Space Distribution of Red Giants and the Galactic Structure

1984 ◽  
Vol 78 ◽  
pp. 257-260
Author(s):  
K. Ishida
Keyword(s):  
Galactic Structure ◽  
Space Distribution ◽  
Red Giants ◽  
Stellar Content ◽  
Late Type ◽  
Ir Radiation ◽  
Near Ir ◽  
The Galaxy ◽  
K Band

AbstractStellar content contributing to near IR radiation do not show radial differentiation in the Galaxy. Late-type giants and supergiants supply about 70% of the total volume emissivity at the K band, in the solar vicinity within 1 kpc, and also at the distance of several kpc in the Scutum region.

scholarly journals Stellar parameters in the bulge cluster NGC 6553

1997 ◽  
Vol 189 ◽  
pp. 203-206 ◽  
Author(s):  
B. Barbuy ◽  
S. Ortolani ◽  
E. Bica ◽  
A. Renzini ◽  
M.D. Guarnieri
Keyword(s):  
Globular Clusters ◽  
Stellar Population ◽  
Spectroscopic Analysis ◽  
Galactic Center ◽  
Stellar Populations ◽  
The Sun ◽  
Galactic Bulge ◽  
Complete Understanding ◽  
Luminosity Functions ◽  
Bulge Formation

Globular clusters in the Galactic bulge form a flattened system, extending from the Galactic center to about 4.5 kpc from the Sun (Barbuy et al. 1997). A study of abundance ratios in these clusters is very important for a more complete understanding of the bulge formation. In this work we present a spectroscopic analysis of individual stars in NGC 6553. This cluster is a key one because it is located at d⊙ ≍ 5.1 kpc, therefore relatively close to us, and at the same time it is representative of the Galactic bulge stellar population: (a) Ortolani et al. (1995) showed that NGC 6553 and NGC 6528 show very similar Colour-Magnitude Diagrams (CMDs), and NGC 6528 is located at d⊙ ≍ 7.83 kpc, very close to the Galactic center; (b) the stellar populations of the Baade Window is also very similar to that of NGC 6553 and NGC 6528 as Ortolani et al. (1995) have shown by comparing their luminosity functions.

scholarly journals Structure and kinematics of Type II Cepheids in the Galactic bulge based on near-infrared VVV data

2018 ◽  
Vol 619 ◽  
pp. A51 ◽  
Author(s):  
V. F. Braga ◽  
A. Bhardwaj ◽  
R. Contreras Ramos ◽  
D. Minniti ◽  
G. Bono ◽  
...  
Keyword(s):  
Proper Motion ◽  
Stellar Population ◽  
Near Infrared ◽  
Galactic Center ◽  
Tangential Velocity ◽  
Type Ii ◽  
Galactic Bulge ◽  
Rr Lyrae ◽  
Sgr A ◽  
Kinematic Properties

Context. Type II Cepheids (T2Cs) are radially pulsating variables that trace old stellar populations and provide distance estimates through their period-luminosity (PL) relation. Aims. We trace the structure of old stellar population in the Galactic bulge using new distance estimates and kinematic properties of T2Cs. Methods. We present new near-infrared photometry of T2Cs in the bulge from the VISTA Variables in the Vía Láctea survey (VVV). We provide the largest sample (894 stars) of T2Cs with JHKs observations that have accurate periods from the Optical Gravitational Lensing Experiment (OGLE) catalog. Our analysis makes use of the Ks-band time-series observations to estimate mean magnitudes and individual distances by means of the PL relation. To constrain the kinematic properties of our targets, we complement our analysis with proper motions based on both the VVV and Gaia Data Release 2. Results. We derive an empirical Ks-band PL relation that depends on Galactic longitude and latitude: Ks0 = (10.66 ± 0.02) − (2.21 ± 0.03)·(log P−1.2)−(0.020±0.003)·l+(0.050±0.008)·|b| mag; individual extinction corrections are based on a 3D reddening map. Our targets display a centrally concentrated distribution, with solid evidence of ellipsoidal symmetry – similar to the RR Lyræ ellipsoid – and a few halo outliers up to ≳100 kpc. We obtain a distance from the Galactic center of R0 = 8.46 ± 0.03(stat.) ± 0.11(syst.) kpc. We also find evidence that the bulge T2Cs belong to a kinematically hot population, as the tangential velocity components (συl∗ = 104.2 ± 3.0kms−1 and συb = 96.8 ± 5.5kms−1) agree within 1.2σ. Moreover, the difference between absolute and relative proper motion is in good agreement with the proper motion of Sgr A✻ from VLBA measures. Conclusions. We conclude that bulge T2Cs display an ellipsoidal spatial distribution and have kinematics similar to RR Lyræ stars, which are other tracers of the old, low-mass stellar population. T2Cs also provide an estimate of R0 that agrees excellently well with the literature, taking account of the reddening law.

scholarly journals The Near-IR Extinction Law

2009 ◽  
Vol 5 (H15) ◽  
pp. 784-784
Author(s):  
Joseph J. Stead ◽  
Melvin G. Hoare
Keyword(s):  
Power Law ◽  
Stellar Population ◽  
Galactic Plane ◽  
Line Of Sight ◽  
Population Synthesis ◽  
Near Ir ◽  
Stellar Population Synthesis

AbstractWe show that the power-law slope of the near-IR extinction law is significantly steeper than previously thought. Simulated colour-colour diagrams including a stellar population synthesis, realistic extinction distribution along the line-of-sight and synthesis through the filter profiles are compared to data from the UKIDSS Galactic Plane Survey. The slope of extinction with wavelength is found to be 2.14 ± 0.05 for total visual extinctions up to about 25 magnitudes and for a number of locations.

scholarly journals Observational constraints on the formation and evolution of the Milky Way nuclear star cluster with Keck and Gemini

2016 ◽  
Vol 11 (S322) ◽  
pp. 222-230
Author(s):  
Tuan Do ◽  
Andrea Ghez ◽  
Mark Morris ◽  
Jessica Lu ◽  
Samantha Chappell ◽  
...  
Keyword(s):  
Stellar Population ◽  
Galactic Center ◽  
Compact Star ◽  
Theoretical Work ◽  
Star Cluster ◽  
Three Dimensions ◽  
Spectroscopic Observations ◽  
Solar Metallicity ◽  
Formation And Evolution ◽  
Central Parsec

AbstractWe summarize work on the central parsec of the Galactic center based on imaging and spectroscopic observations at the Keck and Gemini telescopes. These observations include stellar positions in two dimension and the velocity in three dimensions. Spectroscopic observations also enables measurements of the physical properties of individual stars, such as the spectral type and in some cases the effective temperature, metallicity, and surface gravity. These observations show a complex stellar population with a young (4-6 Myr) compact star cluster in the central 0.5 pc embedded in in an older and much more massive nuclear star cluster. Surprisingly, the old late-type giants do not show a cusp profile as long been expected from theoretical work. The majority of the stars have higher than solar metallicity, with only about 6% of the stars having [M/Fe] < −0.5, which is consistent with an origin from the MW disk.

scholarly journals 1.9. Globular clusters within 5° of the Galactic center

1998 ◽  
Vol 184 ◽  
pp. 33-34
Author(s):  
B. Barbuy ◽  
E. Bica ◽  
S. Ortolani
Keyword(s):  
Spatial Distribution ◽  
Globular Clusters ◽  
Stellar Population ◽  
Galactic Center ◽  
Observational Constraints ◽  
Galactic Bulge ◽  
Very Old

The knowledge of age and spatial distribution of stars in the Galactic bulge require observational constraints to establish whether its stellar population is very old (Larson 1990) or is a younger, disk-like component (Raha et al. 1992), and if its shape is spherical or extended, or perhaps a bar (Blitz & Spergel 1991). Yet other possibilities are a flattened bulge or a disk-like system (Zinn 1985; Armandroff 1989; Ortolani et al. 1993; Minniti 1995).

scholarly journals Morphology of the Galactic Bulge from COBE DIRBE Observations

1996 ◽  
Vol 169 ◽  
pp. 61-69
Author(s):  
E. Dwek
Keyword(s):  
Interstellar Dust ◽  
Galactic Center ◽  
Galactic Plane ◽  
Star Formation History ◽  
Galactic Bulge ◽  
Stellar Content ◽  
The Galaxy ◽  
Infrared Background ◽  
History Of ◽  
Sweeping Gas

The Diffuse Infrared Background Experiment (DIRBE) on-board the Cosmic Background Explorer (COBE) satellite has provided striking new images of the Galactic bulge at effective wavelengths of 1.25, 2.2, 3.5, and 4.9μ (Hauser 1993, plate 3; Arendt et al. 1994; Weiland et al. 1994). The bulge, defined here as the spheroid within the |l| < 20° and |b| < 10° region around the Galactic center, and its stellar content have been subjects of considerable interest since they contain important clues about the dynamical and star-formation history of our Galaxy. The morphology of the Galactic bulge is much harder to ascertain than that of bulges in many external galaxies, because of our location in the Galactic plane amid the obscuration by interstellar dust. In spite of this difficulty, there has recently been an accumulating body of evidence that the stellar distribution in the bulge is bar shaped, i.e. that the bulge is not rotationally symmetric in the plane of the disk (see Blitz 1993 for a review of the subject). The existence of a bar in our Galaxy would have important implications for the dynamics of the Galaxy. A bar would provide a mechanism for sweeping gas from the disk into the Galactic center “feeding” a central black hole (e.g. Shlosman, Frank, & Begelman 1989). It would also provide a mechanism for generating spiral arms, and a basis for estimating the mass of the halo relative to that of the disk (e.g. Combes & Sanders 1981 and references therein).

scholarly journals Unveiling the Secrets of the Galactic bulge through stellar abundances in the near-IR: a VLT/Crires project

2008 ◽  
Vol 4 (S254) ◽  
pp. 159-164
Author(s):  
Nils Ryde
Keyword(s):  
Milky Way ◽  
Line Of Sight ◽  
Galactic Bulge ◽  
Stellar Abundances ◽  
Preliminary Results ◽  
Elemental Abundances ◽  
Near Ir ◽  
Visual Extinction ◽  
Formation And Evolution

AbstractThe formation and evolution of the Milky Way bulge can be constrained by studying elemental abundances of bulge stars. Due to the large and variable visual extinction in the line-of-sight towards the bulge, an analysis in the near-IR is preferred. Here, I will present some preliminary results of an on-going project in which elemental abundances, especially those of the C, N, and O elements, of bulge stars are investigated by analysing CRIRES spectra observed with the VLT.

Metallicity of Red Giants in the Galactic Bulge from Near-Infrared Spectroscopy

2000 ◽  
Vol 120 (2) ◽  
pp. 833-844 ◽  
Author(s):  
Solange V. Ramírez ◽  
Andrew W. Stephens ◽  
Jay A. Frogel ◽  
D. L. DePoy
Keyword(s):  
Infrared Spectroscopy ◽  
Near Infrared Spectroscopy ◽  
Near Infrared ◽  
Red Giants ◽  
Galactic Bulge

scholarly journals Observations and Models for Red Giants with Unusual Dust

1989 ◽  
Vol 106 ◽  
pp. 367-367
Author(s):  
Ian Griffin ◽  
C.J. Skinner ◽  
B.R. Whitmore
Keyword(s):  
Service Time ◽  
Dust Emission ◽  
Red Giants ◽  
Carbon Stars ◽  
Near Ir ◽  
Medium Resolution ◽  
Silicate Feature ◽  
L Band ◽  
M Stars ◽  
Selection Of

We present near IR (H, K and L band) medium resolution (ƛ/Δƛ ∼ 600) spectra for a selection of 9 red giants which have previously been shown to exhibit anomalous dust emission as characterised by their IRAS LRS spectra. The objects observed (during UKIRT and AAT service time) include Carbon stars whose LRS spectra show the 9.7μm silicate feature and also M stars whose LRS spectra display an 11.3μm feature similar to that usually associated with emission from SiC dust grains.

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