A new look at the kinematics of the bulge from an N-body model

Abstract

(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 heliocentric radial velocity distribution of bulge stars. Four different latitudes were considered: $b=-4^{\circ }$, $-6^{\circ }$, $-8^{\circ }$, and $-10^{\circ }$, along the bulge minor axis as well as outside it, at $l=\pm 5^{\circ }$ and $l=\pm 10^{\circ }$. The bulge X-shaped structure comprises stars that formed in the disk at different locations. Stars formed in the outer disk, beyond the end of the bar, which are part of the boxy peanut-bulge structure may show peaks in the velocity distributions at positive and negative heliocentric radial velocities with high absolute values that can be larger than 100 $\mathrm{km}$ ${\mathrm{s}}^{-1}$, depending on the observed direction. In some cases the structure of the velocity field is more complex and several peaks are observed. Stars formed in the inner disk, the most numerous, contribute predominantly to the X-shaped structure and present different kinematic characteristics. Our results may enable us to interpret the cold high-velocity peak observed in the APOGEE commissioning data, as well as the excess of high-velocity stars in the near and far arms of the X-shaped structure at $l$=$0^{\circ }$ and $b$=$-6^{\circ }$. When compared with real data, the kinematic picture becomes more complex due to the possible presence in the observed samples of classical bulge and/or thick disk stars. Overall, our results point to the existence of complex patterns and structures in the bulge velocity fields, which are generated by the bar. This suggests that caution should be used when interpreting the bulge kinematics: the presence of substructures, peaks and clumps in the velocity fields is not necessarily a sign of past accretion events.

arXiv comment21 pages, 18 figures. Accepted for publication in A&A

References in corpus (56)

• The age structure of stellar populations in the solar vicinity. Clues of a two-phase formation history of the Milky Way disk
• The Secular Evolution of Disk Structural Parameters
• Evolution of Stellar Bars in Live Axisymmetric Halos: Recurrent Buckling and Secular Growth
• Mapping the Three-Dimensional Density of the Galactic Bulge with VVV Red Clump Stars
• Our Milky Way as a Pure-Disk Galaxy -- A Challenge for Galaxy Formation
• The photometric structure of the inner Galaxy
• ARGOS III: Stellar Populations in the Galactic Bulge of the Milky Way
• Two Red Clumps and the X-Shaped Milky Way Bulge
• The Split Red Clump of the Galactic Bulge from OGLE-III
• The Bulge Radial Velocity Assay (BRAVA): II. Complete Sample and Data Release
• The metallicity distribution of bulge clump giants in Baade's Window
• K-Band Calibration of the Red Clump Luminosity
• Color-Magnitude Diagram Distribution of the Bulge Red Clump Stars - Evidence for the Galactic Bar
• ARGOS IV: The Kinematics of the Milky Way Bulge
• Alpha element abundances and gradients in the Milky Way bulge from FLAMES-GIRAFFE spectra of 650 K giants
• The origin of the split red clump in the Galactic bulge of the Milky Way
• Modelling the Galactic bar using OGLE-II Red Clump Giant Stars
• The structure of the Galactic bar
• Insights on the Milky Way bulge formation from the correlations between kinematics and metallicity
• Mapping the X-Shaped Milky Way Bulge
• The dominant epoch of star formation in the Milky Way formed the thick disc
• The Gaia-ESO Survey: metallicity and kinematic trends in the Milky Way bulge
• The GIRAFFE Inner Bulge Survey (GIBS). I. Survey Description and a kinematical map of the Milky Way bulge
• ARGOS II: The Galactic Bulge Survey
• The Bulge Radial Velocity Assay (BRAVA): I. Techniques and a Rotation Curve
• A New Photometric Model of the Galactic Bar using Red Clump Giants
• Kinematics at the Edge of the Galactic Bulge: Evidence for Cylindrical Rotation
• Unifying boxy bulge and planar long bar in the Milky Way
• The Bulge Radial Velocity Assay (BRAVA): I. Sample Selection and a Rotation Curve
• Formation and evolution of galactic disks with a multiphase numerical model
• A boxy bulge in the Milky Way. Inversion of the stellar statistics equation with 2MASS data
• Constraining the structure and formation of the Galactic bulge from a field in its outskirts. FLAMES-GIRAFFE spectra of about 400 red giants around (l,b)=(0°,-10°)
• Why the Milky Way's bulge is not only a bar formed from a cold thin disk
• Signatures of Bulge Triaxiality from Kinematics in Baade's Window/
• The Apache Point Observatory Galactic Evolution Experiment: First Detection of High Velocity Milky Way Bar Stars
• The Vertical X-shaped Structure in the Milky Way: Evidence from a Simple Boxy Bulge Model
• Mapping a stellar disk into a boxy bulge: The outside-in part of the Milky Way bulge formation
• Metallicity gradients through disk Instability: A simple model for the Milky Way's boxy bulge
• Evidence of a Metal Rich Galactic Bar from the Vertex Deviation of the Velocity Ellipsoid
• 3D kinematics through the X-shaped Milky Way bulge
• N-body simulation insights into the X-shaped bulge of the Milky Way: Kinematics and distance to the Galactic Centre
• Metallicity and kinematics of the bar in-situ
• Origin of the high v_los feature in the Galactic bar
• Dynamics of the Galactic Bulge using Planetary Nebulae
• The X-Shaped Milky Way Bulge in OGLE-III Photometry and in N-Body Models
• Separating the conjoined red clump in the Galactic Bulge: Kinematics and Abundances
• Fabry-Perot Absorption Line Spectroscopy of the Galactic Bar. I. Kinematics
• A Kiloparsec-Scale Nuclear Stellar Disk in the Milky Way as a Possible Explanation of the High Velocity Peaks in the Galactic Bulge
• Resonant Orbits and the High Velocity Peaks Towards the Bulge
• On the Correlation Between Metallicity and the X-Shaped Morphology of the Milky Way Bulge
• Measurements of streaming motions of the Galactic bar with Red Clump Giants
• Kinematics of the X-shaped Milky Way Bulge: Expectations from a Self-consistent N-body Model
• Constraining the Galactic Bar Parameters with Red Clump Giants
• Are high velocity peaks in the Milky Way bulge due to the bar?
• Asymmetric streaming motion in the Galactic bulge X-shaped structure revealed by the OGLE-III proper motions
• Theoretical Models of the Galactic Bulge

Cited by in corpus (7)

• The disc origin of the Milky Way bulge: Dissecting the chemo-morphological relations using N-body simulations and APOGEE
• Formation of S0 galaxies through mergers. Morphological properties: tidal relics, lenses, ovals, and other inner components
• The disc origin of the Milky Way bulge: On the necessity of the thick disc
• Predicted Stellar Kinematics of a Kiloparsec-Scale Nuclear Disc (or Ring) in the Milky Way
• Searching for a kinematic signature of the moderately metal-poor stars in the Milky Way bulge using N-body simulations
• Spectroscopic Observations of Obscured Populations in the Inner Galaxy: 2MASS-GC02, Terzan 4, and the 200 km/s stellar peak
• Rediscovering the Milky Way with orbit superposition approach and APOGEE data III. Panoramic view of the bulge