2017/07/20 by M. Opitsch, Michael Opitsch, M. H. Fabricius +9 · 20 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Bulge #Galaxies: Formation, Evolution, Phenomena #Galaxy #Gravitational microlensing #Kinematics #Photometry (optics) #Radial velocity #Spiral galaxy #Stars #Stellar kinematics #Stellar, planetary, and galactic studies #astro-ph.GA
paper · pdf · doi:10.1051/0004-6361/201730597
published in Astronomy and Astrophysics 611, A38 (EDP Sciences) · 23 pages, 39 figures; accepted for publication in A&A
arxiv created 2017/07/20 · openalex publication_date 2017/11/17 · arxiv updated 2018/03/21 · openalex created_date 2019/07/30 · openalex updated_date 2026/08/05
Aim. As the nearest large spiral galaxy, M 31 provides a unique opportunity to study the structure and evolutionary history of this galaxy type in great detail. Among the many observing programs aimed at M 31 are microlensing studies, which require good three-dimensional models of the stellar mass distribution. Possible non-axisymmetric structures like a bar need to be taken into account. Due to M 31’s high inclination, the bar is difficult to detect in photometry alone. Therefore, detailed kinematic measurements are needed to constrain the possible existence and position of a bar in M 31. Methods. We obtained ≈220 separate fields with the optical integral-field unit spectrograph VIRUS-W, covering the whole bulge region of M 31 and parts of the disk. We derived stellar line-of-sight velocity distributions from the stellar absorption lines, as well as velocity distributions and line fluxes of the emission lines H β , [O III ] and [N I ]. Our data supersede any previous study in terms of spatial coverage and spectral resolution. Results. We find several features that are indicative of a bar in the kinematics of the stars, we see intermediate plateaus in the velocity and the velocity dispersion, and correlation between the higher moment h 3 and the velocity. The gas kinematics is highly irregular, but is consistent with non-triaxial streaming motions caused by a bar. The morphology of the gas shows a spiral pattern, with seemingly lower inclination than the stellar disk. We also look at the ionization mechanisms of the gas, which happens mostly through shocks and not through starbursts.