scholarly journals Candidate Hypervelocity Red Clump Stars in the Galactic Bulge Found Using the VVV and Gaia Surveys

2019 ◽  
Vol 887 (2) ◽  
pp. L39
Author(s):  
Alonso Luna ◽  
Dante Minniti ◽  
Javier Alonso-García
Keyword(s):  
Galactic Bulge ◽  
Red Clump

scholarly journals Non-parametric density reconstruction of the Galactic bulge area using red clump stars in the VVV survey

2020 ◽  
Vol 499 (2) ◽  
pp. 1937-1947
Author(s):  
Dylan Paterson ◽  
Brendan Coleman ◽  
Chris Gordon
Keyword(s):  
Parametric Method ◽  
Major Axis ◽  
Galactic Bulge ◽  
Buckling Instability ◽  
Giant Stars ◽  
Red Clump ◽  
Red Giant ◽  
High Resolution Reconstruction ◽  
Spiral Arm ◽  
Non Parametric

ABSTRACT Studies of the red clump giant population in the inner Milky Way suggest the Galactic bulge/bar has a boxy/peanut/X-shaped structure as predicted by its formation via a disc buckling instability. We used a non-parametric method of estimating the Galactic bulge morphology that is based on maximum entropy regularization. This enabled us to extract the 3D distribution of the red giant stars in the bulge from deep photometric catalogues of the VISTA Variables in the Via Lactea survey. Our high-resolution reconstruction confirms the well-known boxy/peanut/X-shaped structure of the bulge. We also find spiral arm structures that extend to around 3 kpc in front of and behind the bulge and are on different sides of the bulge major axis. We show that the detection of these structures is robust to the uncertainties in the luminosity function.

New VIRAC proper motion maps show signature of galactic boxy/peanut bulge

2019 ◽  
Vol 14 (S353) ◽  
pp. 29-30
Author(s):  
Jonathan P. Clarke ◽  
Christopher Wegg ◽  
Ortwin Gerhard ◽  
Leigh C. Smith ◽  
Phil W. Lucas ◽  
...  
Keyword(s):  
Proper Motion ◽  
Dynamical Model ◽  
Line Of Sight ◽  
Selection Function ◽  
Kinematic Structure ◽  
Proper Motions ◽  
Galactic Bulge ◽  
Bulge Region ◽  
Pattern Speed ◽  
Red Clump

AbstractWe have derived absolute proper motions of stars in the Galactic bulge region combining the VVV InfraRed Astrometric Catalogue (VIRAC) and Gaia. We use the proper motions to study the kinematic structure of the bulge both integrated along the line-of-sight and in magnitude intervals using red clump stars as standard candles. In parallel we compare to a made-to-measure barred dynamical model, folding in the VIRAC selection function, to understand and interpret the structures that we observe. The barred dynamical model, which contains a boxy/peanut bulge, and has a pattern speed of 37.5 kms−1 kpc−1, is able to reproduce all structures impressively well.

scholarly journals Evidence for the Galactic Bar from the Two Color Photometry of the Bulge Red Clump Stars

1996 ◽  
Vol 169 ◽  
pp. 103-109
Author(s):  
K. Z. Stanek ◽  
M. Mateo ◽  
A. Udalski ◽  
M. Szymański ◽  
J. Kałużny ◽  
...  
Keyword(s):  
Data Base ◽  
Gravitational Lensing ◽  
Galactic Bulge ◽  
Gravitational Microlensing ◽  
Huge Data ◽  
Red Clump

The Optical Gravitational Lensing Experiment (OGLE, Udalski et al. 1994a; Paczynski et al. 1994b – these proceedings; and references therein) is an extensive photometric search for the rare cases of gravitational microlensing of Galactic bulge stars by foreground objects. It provides a huge data base (Szymański & Udalski 1993), from which color-magnitude diagrams have been compiled (Udalski et al. 1993, 1994b). Here we discuss the use a of well-defined population of bulge red clump stars to investigate the presence of the bar in our Galaxy. The results of our earlier studies are described by Stanek et al. (1994).

scholarly journals Chemical Composition of the Galactic Bulge in Baade's Window

2009 ◽  
Vol 5 (S265) ◽  
pp. 279-284 ◽  
Author(s):  
Andrew McWilliam ◽  
Jon Fulbright ◽  
R. Michael Rich
Keyword(s):  
Chemical Composition ◽  
Massive Stars ◽  
Galactic Bulge ◽  
Rapid Formation ◽  
The Mean ◽  
Red Clump

Abstract1. McWilliam and Zoccali (2009) show the existence of two Red Clump populations towards the Galactic bulge, based on 2MASS data. 2.Measured [Mg/Fe], [Al/Fe], and [La/Eu] ratios in the bulge are consistent with a rapid formation timescale (<1Gyr), which also requires a slightly top-heavy IMF to reproduce the mean bulge metallicity. The [C/O] and [O/Fe] ratios are consistent if their predicted metal-dependent yields from massive stars with winds are considered. The decline in explosive [α/Fe] (Si, Ca, and Ti) can only be understood if their yields also decline with metallicity above [Fe/H]~−1.

scholarly journals SEPARATING THE CONJOINED RED CLUMP IN THE GALACTIC BULGE: KINEMATICS AND ABUNDANCES

2011 ◽  
Vol 732 (2) ◽  
pp. L36 ◽  
Author(s):  
Roberto De Propris ◽  
R. Michael Rich ◽  
Andrea Kunder ◽  
Christian I. Johnson ◽  
Andreas Koch ◽  
...  
Keyword(s):  
Galactic Bulge ◽  
Red Clump

scholarly journals Distribution of red clump stars does not support the X-shaped Galactic bulge

2019 ◽  
Vol 627 ◽  
pp. A3 ◽  
Author(s):  
M. López-Corredoira ◽  
Y.-W. Lee ◽  
F. Garzón ◽  
D. Lim
Keyword(s):  
Density Distribution ◽  
Near Infrared ◽  
Absolute Magnitude ◽  
Line Of Sight ◽  
Galactic Bulge ◽  
Double Peak ◽  
The Absolute ◽  
The Difference ◽  
Red Clump ◽  
Two Peaks

Context. Claims of an X-shaped Galactic bulge were based on the assumption of red clump stars as standard candles in some lines of sight crossing the off-plane bulge. However, some doubts have been cast on whether the two peaks in star counts along the line of sight really represent a double peak in the density distribution, or whether there is something wrong with the assumption of a unique constant absolute magnitude for all of these stars. Aims. With the advent of Gaia-DR2 parallaxes in combination with near-infrared VISTA-VVV data, we are able to check which of the hypotheses is correct. Methods. We calculated the median absolute magnitude MK corresponding to both peaks of putative red clumps in seven lines of sight with the lowest extinction in the interesting coordinates’ range. Results. The difference between the absolute magnitude of the bright and the faint peak is ΔMK ≈ 0.4. The selected stars in both peaks cannot be represented by the same red clump giants with constant MK ≈ −1.6. Conclusions. The hypothesis that the bulge contains an X-shape is based on the assumption that the faint and bright peaks of the density distribution towards the bulge are dominated by standard red clump stars. However, we show that both the faint and bright peaks cannot be dominated by standard red clump stars simultaneously.

scholarly journals Modelling the Galactic Bar using Red Clump Stars

1996 ◽  
Vol 157 ◽  
pp. 545-548 ◽  
Author(s):  
K. Z. Stanek ◽  
M. Mateo ◽  
A. Udalski ◽  
M. Szymański ◽  
J. Kałuzny ◽  
...  
Keyword(s):  
Line Of Sight ◽  
Galactic Bulge ◽  
Preliminary Results ◽  
Gravitational Microlensing ◽  
Luminosity Functions ◽  
Red Clump ◽  
Additional Constraints ◽  
Galactic Longitude

AbstractThe color-magnitude diagrams of ~ 1 × 106 stars obtained for 19 fields towards the Galactic bulge with the OGLE project reveal a well-defined population of bulge red clump stars. We found that the distributions of the extinction-adjusted apparent magnitudes of red clump stars in fields lying at ι = ±5° in galactic longitude differ by ∼ 0.4 mag. A plausible explanation of this observed difference in the luminosity distribution is that the Galactic bulge is a triaxial structure, or a bar, which is inclined to the line of sight by no more than 45°. The part of the bar at the positive galactic longitude is closer to us. Work is now under way to model the Galactic bar by fitting the observed luminosity functions in the red clump region for various fields. Preliminary results indicate that the angle of the inclination of the bar to the line of sight can be as small as ∼ 20°. Gravitational microlensing can provide us with additional constraints on the structure of the Galactic bar.

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