Mapping the three-dimensional density of the galactic bulge with VVV red clump stars

By C. Wegg, O. Gerhard. 2013

275 citations recorded by the source corpus.

The inner Milky Way is dominated by a boxy, triaxial bulge which is believed to have formed through disk instability processes. Despite its proximity, its large-scale properties are still not very well known, due to our position in the obscuring Galactic disk. Here we make a measurement of the three-dimensional density distribution of the Galactic bulge using red clump giants identified in DR1 of the VVV survey. Our density map covers the inner (2.2x1.4x1.1)kpc of the bulge/bar. Line-of-sight density distributions are estimated by deconvolving extinction and completeness corrected K-band magnitude distributions. In constructing our measurement, we assume that the three-dimensional bulge is 8-fold mirror triaxially symmetric. In doing so we measure the angle of the bar-bulge to the line-of-sight to be (27+- 2)deg, where the dominant error is systematic arising from the details of the deconvolution process. The resulting density distribution shows a highly elongated bar with projected axis ratios ~(1:2.1) for isophotes reaching ~2kpc along the major axis. Along the bar axes the density falls off roughly exponentially, with axis ratios (10:6.3:2.6) and exponential scale-lengths (0.70:0.44:0.18)kpc. From about 400pc above the Galactic plane, the bulge density distribution displays a prominent X-structure. Overall, the density distribution of the Galactic bulge is characteristic for a strongly boxy/peanut shaped bulge within a barred galaxy.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/6585ad4417ebf79c753a0a65a9dad11e09ca87fb

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In Astronomy and Astrophysics

Citations in the corpus

Mean proper motions, space orbits, and velocity dispersion profiles of Galactic globular clusters derived fromGaiaDR2 data (2018, background): “It has been suggested that a large fraction of the Milky Way bulge stars have formed through disc instability processes and are not part of a classical bulge formed through mergers early in the formation of the Galaxy (e.g. Wegg & Gerhard 2013).”
The Galaxy in Context: Structural, Kinematic, and Integrated Properties (2016, methodology): “Data from Wegg & Gerhard (2013); figure after Portail et al. (2015b).”
Dynamical modelling of the galactic bulge and bar: the Milky Way's pattern speed, stellar and dark matter mass distribution (2016, methodology): “…the so-called split red clump in the galactic bulge (Nataf et al. 2010; McWilliam & Zoccali 2010) and the later 3D mapping of the bulge density by Wegg & Gerhard (2013) showed that the galactic bulge has a boxy/peanut (B/P) shape, similarly to bulges formed in N-body models by buckling of a…”
Target Selection for the SDSS-IV APOGEE-2 Survey (2017, background): “…stars for tracing the chemodynamics of distance-resolved structures, such as the bar and X-shape (e.g., McWilliam & Zoccali 2010; Nataf et al. 2010; Wegg & Gerhard 2013), APOGEE-2 targets a few “deep” inner Galaxy fields, with a targeting strategy designed to increase the fraction of RC to RGB…”
Made-to-measure models of the Galactic box/peanut bulge: stellar and total mass in the bulge region (2015, methodology): “The peanut shape was mapped last year in three dimensions by Wegg & Gerhard (2013) using public data from the VVV survey.”
The structure of the Milky Way's bar outside the bulge (2015, methodology): “5 that the bar angle between 10◦ l 20◦ was close to the α ≈ 27◦ found in the B/P Bulge.”
Predictions of the WFIRST Microlensing Survey. I. Bound Planet Detection Rates (2018, background): “This leads to significantly smaller event rates per source than would be expected for a more reasonable bar angle of ∼30◦ (e.g. Wegg & Gerhard 2013; Cao et al. 2013), which could lead us to over-correcting the event rates.”