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The color-magnitude diagrams of $\sim 7 \times 10^5$ stars obtained for 12 fields across the Galactic bulge with the OGLE project reveal a well-defined population of bulge red clump giants. We find that the distributions of the apparent…

Astrophysics · Physics 2009-10-28 K. Z. Stanek , A. Udalski , M. Szymanski , J. Kaluzny , M. Kubiak , M. Mateo , W. Krzeminski

By analyzing a N-body simulation of a bulge formed simply via a bar instability mechanism operating on a kinematically cold stellar disk, and by comparing the results of this analysis with the structural and kinematic properties of the main…

Astrophysics of Galaxies · Physics 2015-04-22 P. Di Matteo , A. Gomez , M. Haywood , F. Combes , M. D. Lehnert , M. Ness , O. N. Snaith , D. Katz , B. Semelin

The results of bar-driven mass inflow are directly observable in high-resolution HST observations of their circumnuclear regions. These observations reveal a wealth of structures dominated by dust lanes, often with a spiral-like morphology,…

Astrophysics · Physics 2016-01-27 Paul Martini

The Apache Point Observatory Galactic Evolution Experiment has measured the stellar velocities of red giant stars in the inner Milky Way. We confirm that the line of sight velocity distributions (LOSVDs) in the mid-plane exhibit a second…

Astrophysics of Galaxies · Physics 2015-10-15 Victor P. Debattista , Melissa Ness , Samuel W. F. Earp , David R. Cole

We present evidence for a Galactic North-South asymmetry in the number density and bulk velocity of solar neighborhood stars. The number density profile, which is derived from main-sequence stars in the Sloan Digital Sky Survey, shows a…

Astrophysics of Galaxies · Physics 2015-06-04 Lawrence M. Widrow , Susan Gardner , Brian Yanny , Scott Dodelson , Hsin-Yu Chen

We present the metallicity results from the ARGOS spectroscopic survey of the Galactic bulge. Our aim is to understand the formation of the Galactic bulge: did it form via mergers, as expected from Lambda CDM theory, or from disk…

Astrophysics of Galaxies · Physics 2015-06-12 M. Ness , K. Freeman , E. Athanassoula , E. Wylie de Boer , J. Bland Hawthorn , M. Asplund , G. F. Lewis , D. Yong , R. R. Lane , L. L. Kiss

It has been suggested that the peanut-shaped bulges seen in some edge-on disk galaxies are produced when bars in these galaxies buckle. This paper reviews the modelling which seeks to show how bars buckle, and I present a very simple new…

Astrophysics · Physics 2007-05-23 Michael R. Merrifield

I review some of the work on bars which is closely linked to the bar/bulge system in our Galaxy. Several independent studies, using totally independent methods, come to the same results about the 3D structure of a bar, i.e., that a bar is…

Astrophysics of Galaxies · Physics 2015-06-04 E. Athanassoula

We construct a large set of dynamical models of the galactic bulge, bar and inner disk using the Made-to-Measure method. Our models are constrained to match the red clump giant density from a combination of the VVV, UKIDSS and 2MASS…

Astrophysics of Galaxies · Physics 2016-12-21 Matthieu Portail , Ortwin Gerhard , Christopher Wegg , Melissa Ness

Evidence for a bar at the center of the Milky Way triggered a renewed enthusiasm for dynamical modelling of the Galactic bar-bulge. Our goal is to compare the kinematics of a sample of tracers, planetary nebulae, widely distributed over the…

The Galactic bulge at latitude $4<|b|$(deg.)$<10$ was claimed to show an X-shape, which means that stellar density distributions along the line of sight have a double peak. However, this double peak is only observed with the red-clump…

Astrophysics of Galaxies · Physics 2022-10-19 Ž. Chrobáková , M. López-Corredoira , F. Garzón

Simulations have shown that bars are subject to a vertical buckling instability that transforms thin bars into boxy or peanut-shaped structures, but the physical conditions necessary for buckling to occur are not fully understood. We use…

Astrophysics of Galaxies · Physics 2017-08-23 Zhao-Yu Li , Luis C. Ho , Aaron J. Barth

Major-axis long-slit stellar kinematics was obtained for 30 edge-on spiral galaxies, 24 with a boxy/peanut-shaped (B/PS) bulge. B/PS bulges are present in >45% of highly inclined systems and much work suggests that they are the edge-on…

Astrophysics · Physics 2009-11-10 A. Chung , M. Bureau

Some observations indicate that the Milky Way has two inner components, a bulge and a long bar, which present a misalignment of about 20 degrees that is against the predictions of some theoretical models that are based on numerical…

Astrophysics of Galaxies · Physics 2014-11-19 Paul Compère , Martín López-Corredoira , Francisco Garzón

Recent observational studies have revealed that the Galactic bulge has cylindrical rotation and a steeper vertical metallicity gradient. We adopt two representative models for the bulge formation and thereby investigate whether the two…

Astrophysics of Galaxies · Physics 2015-05-28 Kenji Bekki , Takuji Tsujimoto

We use high resolution collisionless $N$-body simulations to study the secular evolution of disk galaxies and in particular the final properties of disks that suffer a bar and perhaps a bar-buckling instability. Although we find that bars…

Astrophysics · Physics 2009-11-10 Victor P. Debattista , C. Marcella Carollo , Lucio Mayer , Ben Moore

We show for the first time, that a fully cosmological hydrodynamical simulation can reproduce key properties of the innermost region of the Milky Way. Our high resolution simulation matches the profile and kinematics of the Milky Way's…

Astrophysics of Galaxies · Physics 2018-07-25 Tobias Buck , Melissa K. Ness , Andrea V. Macciò , Aura Obreja , Aaron A. Dutton

The gas dynamics in the Galactic disc is modeled by releasing an initially axisymmetric SPH component in a completely self-consistent and symmetry-free 3D N-body simulation of the Milky Way in which the stellar components display a…

Astrophysics · Physics 2007-05-23 R. Fux

We describe a new phenomenon of `bar damping' that may have played an important role in shaping the Milky Way bar and bulge as well as its spiral structure. We use a collisionless N-body simulation of a Milky Way-like galaxy initially…

Astrophysics of Galaxies · Physics 2016-11-07 Ewa L. Lokas

(Abridged) By using an N-body simulation of a bulge that was formed via a bar instability mechanism, we analyse the imprints of the initial (i.e. before bar formation) location of stars on the bulge kinematics, in particular on the…

Astrophysics of Galaxies · Physics 2016-04-27 A. Gomez , P. Di Matteo , N. Stefanovitch , M. Haywood , F. Combes , D. Katz , C. Babusiaux