The large scale dust lanes of the Galactic bar

Abstract

(abridged) By comparing the distribution of dust and gas in the central regions of the Galaxy, we aim to obtain new insights into the properties of the offset dust lanes leading the bar's major axis in the Milky Way. On the one hand, the molecular emission of the dust lanes is extracted from the observed CO l-b-V distribution according to the interpretation of a dynamical model. On the other hand, a three dimensional extinction map of the Galactic central region constructed from near-infrared observations is used as a tracer of the dust itself and clearly reveals dust lanes in its face-on projection. Comparison of the position of both independent detections of the dust lanes is performed in the (l, b) plane. These two completely independent methods are used to provide a coherent picture of the dust lanes in the Milky Way bar. In both the gas and dust distributions, the dust lanes are found to be out of the Galactic plane, appearing at negative latitudes for l > 0 deg and at positive latitudes for l < 0 deg. However, even though there is substantial overlap between the two components, they are offset from one another with the dust appearing to lie closer to the b = 0 deg plane. Two scenarios are proposed to explain the observed offset. The first involves grain destruction by the bar shock and reformation downstream. Due to the decrease in velocity caused by the shock, this occurs at lower z. The second assumes that the gas and dust remain on a common tilted plane, but that the molecular gas decouples from the Milky Way's magnetic field, itself strong enough to resist the shear of the bar's shock. The diffuse gas and dust remain coupled to the field and are carried further downstream. This second scenario has recently been suggested in order to explain observations of the barred galaxy NGC 1097.

arXiv comment4 pages, 5 figures, accepted for publication in Astronomy and Astrophysics letters

References in corpus (12)

• Interstellar Dust Grains
• The Milky Way in Molecular Clouds: A New Complete CO Survey
• Modelling the Galactic Interstellar Extinction Distribution in Three Dimensions
• COBE's Galactic Bar and Disk
• The structure of the Galactic bar
• Magnetic fields in barred galaxies. IV. NGC 1097 and NGC 1365
• Cosmic-Ray Heating of Molecular Gas in the Nuclear Disk: Low Star Formation Efficiency
• An Upper Limit to the Age of the Galactic Bar
• Coupling the dynamics and the molecular chemistry in the Galactic center
• The Eastern Arm of M83 Revisited: High-Resolution Mapping of 12CO 1-0 Emission
• Physical Conditions of Molecular Gas in the Galactic Center
• 3D MHD Modeling of the Gaseous Structure of the Galaxy: Description of the Simulations

Cited by in corpus (25)

• Gas flow models in the Milky Way embedded bars
• The Bolocam Galactic Plane Survey IV: 1.1 and 0.35 mm Dust Continuum Emission in the Galactic Center Region
• Simulations of the Milky Way's central molecular zone -- I. Gas dynamics
• Lopsided Spiral Galaxies
• Trigonometric parallaxes to star-forming regions within 4 kpc of the galactic center
• Mapping the Milky Way bulge at high resolution: the 3D dust extinction, CO, and X factor maps
• Mass inflow rate into the Central Molecular Zone: observational determination and evidence of episodic accretion
• A theoretical explanation for the Central Molecular Zone asymmetry
• Spectral and intensity variations of Galactic 26^Al emission
• The geometry of the gas surrounding the Central Molecular Zone: on the origin of localised molecular clouds with extreme velocity dispersions
• Dynamically Driven Inflow onto the Galactic Center and its Effect upon Molecular Clouds
• CHIMPS2: Survey description and ${}^{12}$CO emission in the Galactic Centre
• Interstellar dust along the line of sight of GX 3+1
• Multiplicity of nuclear dust lanes and dust lane shocks in the Milky Way bar
• HI Absorption Toward HII Regions at Small Galactic Longitudes
• The long bar as seen by the VVV Survey: II. Star counts
• Evidence of a Cloud-Cloud Collision from Overshooting Gas in the Galactic Center
• On the morphology of dust lanes in galactic bars
• Revealing Gas Inflows towards the Galactic Central Molecular Zone
• Star Formation in Extreme Environments: A 200 pc High Velocity Gas Stream in the Galactic Centre
• Gas Transfer Between the Inner 3-kpc Disk and the Galactic Central Molecular Zone
• Turbulent Pressure Heats Gas and Suppresses Star Formation in Galactic Bar Molecular Clouds
• How is Cold Gas Loaded into Galactic Nuclear Outflows?
• Bar-driven gas redistribution suppresses star formation in spiral galaxies: Evidence from dust lanes in NGC 3351
• SF-R You Sure? The Conflicting Role of Star Formation Rates in Constraining the Evolution of Milky Way Analogues in Cosmological Simulations