2018/08/22 by Matías Blaña Díaz, Matias Blaña, Ortwin Gerhard +10 · 1 citation
Physics and Astronomy · #Andromeda Galaxy #Astronomy and Astrophysical Research #Astrophysics #Bulge #Dark matter #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy formation and evolution #Galaxy rotation curve #Milky Way #Omega #Physics #Quantum mechanics #Star (game theory) #Star formation #Stellar kinematics #Stellar mass #Stellar, planetary, and galactic studies #astro-ph.GA
paper · pdf · doi:10.1093/mnras/sty2311
32 pages, 32 Figures; Published in MNRAS
arxiv created 2018/08/22 · openalex publication_date 2018/08/22 · arxiv updated 2018/08/24 · openalex created_date 2018/08/31 · openalex updated_date 2026/08/05
The Andromeda galaxy (M31) contains a box/peanut bulge (BPB) entangled with a classical bulge (CB) requiring a triaxial modelling to determine the dynamics, stellar, and dark matter mass. We construct made-to-measure models fitting new VIRUS-W IFU bulge stellar kinematic observations, the IRAC-3.6 µm photometry, and the disc’s H i rotation curve. We explore the parameter space for the 3.6 µm mass-to-light ratio |(Υ3.6)|, the bar pattern speed (|Ω\rm p|), and the dark matter mass in the composite bulge (|M\rm B\rm DM|) within |3.2 \rm kpc|. Considering Einasto dark matter profiles, we find the best models for |Υ3.6 = 0.72 ± 0.02 \rm M\odot L\odot -1|, |M\rm B\rm DM = 1.2+0.2-0.4× 1010 \rm M\odot |, and |Ω\rm p = 40± 5 \rm km \rm s\rm -1 \rm kpc-1|. These models have a dynamical bulge mass of |M\rm dyn\rm B = 4.25+0.10-0.29× 1010 \rm M\odot | including a stellar mass of |M⋆ \rm B = 3.09+0.10-0.12× 1010 \rm M\odot |(73 per cent), of which the CB has |M⋆ \rm CB = 1.18+0.06-0.07× 1010 \rm M\odot | (28 per cent) and the BPB |M⋆ \rm BPB = 1.91± 0.06 × 1010 \rm M\odot | (45 per cent). We also explore models with NFW haloes finding that, while the Einasto models better fit the stellar kinematics, the obtained parameters agree within the errors. The |M\rm B\rm DM| values agree with adiabatically contracted cosmological NFW haloes with M31’s virial mass and radius. The best model has two bulge components with completely different kinematics that only together successfully reproduce the observations (μ3.6, υlos, σlos, h3, h4). The modelling includes dust absorption which reproduces the observed kinematic asymmetries. Our results provide new constraints for the early formation of M31 given the lower mass found for the classical bulge and the shallow dark matter profile, as well as the secular evolution of M31 implied by the bar and its resonant interactions with the classical bulge, stellar halo and disc.