Gas flow models in the Milky Way embedded bars

By N. Rodríguez-Fernández, F. Combes. 2008

141 citations recorded by the source corpus.

Context. The gas distribution and dynamics in the inner Galaxy present many unknowns, such as the origin of the asymmetry of the lu-diagram of the Central Molecular Zone (CMZ). On the other hand, there is recent evidence in the stellar component of the presence of a nuclear bar that may be slightly lopsided. Aims. Our goal is to characterize the nuclear bar observed in 2MASS maps and to study the gas dynamics in the inner Milky Way taking into account this secondary bar. Methods. We have derived a realistic mass distribution by fitting the 2MASS star count map with a model including three components (disk, bulge and nuclear bar) and we have simulated the gas dynamics in the deduced gravitational potential using a sticky-particles code. Results. Our simulations of the gas dynamics successfully reproduce the main characteristics of the Milky Way for a bulge orientation of 20°-35° with respect to the Sun-Galactic Center (GC) line and a pattern speed of 30-40 km s -1 kpc -1 . In our models the Galactic Molecular Ring (GMR) is not an actual ring but the inner parts of the spiral arms, while the 3-kpc arm and its far side counterpart are lateral arms that extend around the bar. Our simulations reproduce, for the first time, the parallelogram shape of the lu-diagram of the CMZ as the gas response to the nuclear bar. This bar should be oriented by an angle of ∼60°-75° with respect to the Sun-GC line and its mass amounts to (2-5.5) 10 9 M ⊙ . We show that the observed asymmetry of the CMZ cannot be due to lopsidedness of the nuclear bar as suggested by the 2MASS maps. Conclusions. We do not find clear evidence of lopsidedness in the stellar potential. We propose that the observed asymmetry of the central gas layer can be due to the infalling of gas into the CMZ in the I = 1.3°-complex.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/4ad81818911cc6b69774b9de9591cd10c81538bd

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Citations in the corpus

Molecular gas kinematics within the central 250 pc of the Milky Way (2016, background): “Rodriguez-Fernandez & Combes (2008) suggest that the 1.”
The Galaxy in Context: Structural, Kinematic, and Integrated Properties (2016, methodology): “…with various reference features in the CO lv-plot; Weiner & Sellwood (1999) obtained 42 km s−1 kpc−1 (RCR = 5.0 kpc) from matching the extreme HI velocity contour; Rodriguez-Fernandez & Combes (2008) obtained 30– 40 km s−1 kpc−1 and RCR = 5–7 kpc matching to the Galactic spiral arm pattern.”
A 100 pc ELLIPTICAL AND TWISTED RING OF COLD AND DENSE MOLECULAR CLOUDS REVEALED BY HERSCHEL AROUND THE GALACTIC CENTER (2011, methodology): “…imply a flattened potential in the CMZ that is consistent with a x/z = 0.5 axial ratio bulge mass distribution, remarkably similar to the value of 0.5−0.6 recently derived (Rodriguez-Fernandez & Combes 2008) fitting the 2MASS data to a potential model that includes the bulge and the nuclear bar.”
Dynamical modelling of the galactic bulge and bar: the Milky Way's pattern speed, stellar and dark matter mass distribution (2016, background): “Other studies found lower values in the range 25−40kms−1 kpc−1 from gas dynamics (Weiner & Sellwood 1999; Rodriguez-Fernandez & Combes 2008; Sormani et al. 2015; Li et al. 2016) or stellar dynamics (Long et al. 2013; P15).”
The dynamical evolution of molecular clouds near the Galactic Centre - I. Orbital structure and evolutionary timeline (2014, methodology): “Rodriguez-Fernandez & Combes (2008) show that a possible lopsidedness of the stellar potential is not responsible for the asymmetric gas distribution, as it would result in kinematics inco sistent with the observed line-of-sight velocities.”
The 6-GHz methanol multibeam maser catalogue – II. Galactic longitudes 6° to 20° (2010, methodology): “As an example, we cite a recent suggestion by Rodriguez-Fernandez & Combes (2008).”
A NEW MECHANISM FOR RADIAL MIGRATION IN GALACTIC DISKS: SPIRAL–BAR RESONANCE OVERLAP (2009, methodology): “Rodriguez-Fernandez and Combes (2008) estimated the strength of the MW bar to lie in the range 0.25 QT 0.4 by fitting bar models to near infrared observations (2MASS counts).”