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Title: Transverse kinematics of the Galactic bar-bulge from VVV and Gaia

Abstract

ABSTRACT We analyse the kinematics of the Galactic bar-bulge using proper motions from the ESO public survey Vista Variables in the Via Lactea (VVV) and the second Gaia data release. Gaia has provided some of the first absolute proper motions within the bulge and the near-infrared VVV multi-epoch catalogue complements Gaia in highly extincted low-latitude regions. We discuss the relative-to-absolute calibration of the VVV proper motions using Gaia. Along lines of sight spanning $$-10\lt \ell /\, \mathrm{deg}\lt 10$$ and $$-10\lt b/\, \mathrm{deg}\lt 5$$, we probabilistically model the density and velocity distributions as a function of distance of ∼45 million stars. The transverse velocities confirm the rotation signature of the bar seen in spectroscopic surveys. The differential rotation between the double peaks of the magnitude distribution confirms the X-shaped nature of the bar-bulge. Both transverse velocity components increase smoothly along the near side of the bar towards the Galactic Centre, peak at the Galactic Centre, and decline on the far side. The anisotropy is σℓ/σb ≈ 1.1–1.3 within the bulk of the bar, reducing to 0.9–1.1 when rotational broadening is accounted for, and exhibits a clear X-shaped signature. The vertex deviation in ℓ and b is significant |ρℓb| ≲ 0.2, greater on the near side of the bar and produces a quadrupole signature across the bulge indicating approximate radial alignment. We have re-constructed the 3D kinematics from the assumption of triaxiality, finding good agreement with spectroscopic survey results. In the co-rotating frame, we find evidence of bar-supporting x1 orbits and tangential bias in the in-plane dispersion field.

Authors:
ORCiD logo [1];  [2];  [1];  [3]
  1. Institute of Astronomy, University of Cambridge, Madingley Rd, Cambridge CB3 0HA, UK
  2. Institute of Astronomy, University of Cambridge, Madingley Rd, Cambridge CB3 0HA, UK, School of Physics, Astronomy and Mathematics, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK
  3. School of Physics, Astronomy and Mathematics, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1530459
Resource Type:
Published Article
Journal Name:
Monthly Notices of the Royal Astronomical Society
Additional Journal Information:
Journal Name: Monthly Notices of the Royal Astronomical Society Journal Volume: 487 Journal Issue: 4; Journal ID: ISSN 0035-8711
Publisher:
Oxford University Press
Country of Publication:
United Kingdom
Language:
English

Citation Formats

Sanders, Jason L., Smith, Leigh, Evans, N. Wyn, and Lucas, Philip. Transverse kinematics of the Galactic bar-bulge from VVV and Gaia. United Kingdom: N. p., 2019. Web. doi:10.1093/mnras/stz1630.
Sanders, Jason L., Smith, Leigh, Evans, N. Wyn, & Lucas, Philip. Transverse kinematics of the Galactic bar-bulge from VVV and Gaia. United Kingdom. doi:10.1093/mnras/stz1630.
Sanders, Jason L., Smith, Leigh, Evans, N. Wyn, and Lucas, Philip. Tue . "Transverse kinematics of the Galactic bar-bulge from VVV and Gaia". United Kingdom. doi:10.1093/mnras/stz1630.
@article{osti_1530459,
title = {Transverse kinematics of the Galactic bar-bulge from VVV and Gaia},
author = {Sanders, Jason L. and Smith, Leigh and Evans, N. Wyn and Lucas, Philip},
abstractNote = {ABSTRACT We analyse the kinematics of the Galactic bar-bulge using proper motions from the ESO public survey Vista Variables in the Via Lactea (VVV) and the second Gaia data release. Gaia has provided some of the first absolute proper motions within the bulge and the near-infrared VVV multi-epoch catalogue complements Gaia in highly extincted low-latitude regions. We discuss the relative-to-absolute calibration of the VVV proper motions using Gaia. Along lines of sight spanning $-10\lt \ell /\, \mathrm{deg}\lt 10$ and $-10\lt b/\, \mathrm{deg}\lt 5$, we probabilistically model the density and velocity distributions as a function of distance of ∼45 million stars. The transverse velocities confirm the rotation signature of the bar seen in spectroscopic surveys. The differential rotation between the double peaks of the magnitude distribution confirms the X-shaped nature of the bar-bulge. Both transverse velocity components increase smoothly along the near side of the bar towards the Galactic Centre, peak at the Galactic Centre, and decline on the far side. The anisotropy is σℓ/σb ≈ 1.1–1.3 within the bulk of the bar, reducing to 0.9–1.1 when rotational broadening is accounted for, and exhibits a clear X-shaped signature. The vertex deviation in ℓ and b is significant |ρℓb| ≲ 0.2, greater on the near side of the bar and produces a quadrupole signature across the bulge indicating approximate radial alignment. We have re-constructed the 3D kinematics from the assumption of triaxiality, finding good agreement with spectroscopic survey results. In the co-rotating frame, we find evidence of bar-supporting x1 orbits and tangential bias in the in-plane dispersion field.},
doi = {10.1093/mnras/stz1630},
journal = {Monthly Notices of the Royal Astronomical Society},
number = 4,
volume = 487,
place = {United Kingdom},
year = {2019},
month = {6}
}

Journal Article:
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This content will become publicly available on June 25, 2020
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