Distribution and kinematics of atomic and molecular gas inside the Solar circle

Abstract

The detailed distribution and kinematics of the atomic and the CO-bright molecular hydrogen in the disc of the Milky Way inside the Solar circle are derived under the assumptions of axisymmetry and pure circular motions. We divide the Galactic disc into a series of rings, and assume that the gas in each ring is described by four parameters: its rotation velocity, velocity dispersion, midplane density and its scale height. We fit these parameters to the Galactic HI and CO (J=1-0) data by producing artificial HI and CO line-profiles and comparing them with the observations. Our approach allows us to fit all parameters to the data simultaneously without assuming a-priori a radial profile for one of the parameters. We present the distribution and kinematics of the HI and H2 in both the approaching (QIV) and the receding (QI) regions of the Galaxy. Our best-fit models reproduces remarkably well the observed HI and CO longitude-velocity diagrams up to a few degrees of distance from the midplane. With the exception of the innermost 2.5 kpc, QI and QIV show very similar kinematics. The rotation curves traced by the HI and H2 follow closely each other, flattening beyond R=6.5 kpc. Both the HI and the H2 surface densities show a) a deep depression at 0.5<R<2.5 kpc, analogous to that shown by some nearby barred galaxies, b) local overdensities that can be interpreted in terms of spiral arms or ring-like features in the disk. The HI (H2) properties are fairly constant in the region outside the depression, with typical velocity dispersion of 8.9+/-1.1 (4.4+/-1.2) km/s, density of 0.43+/-0.11 (0.42+/-0.22) cm-3 and HWHM scale height of 202+/-28 (64+/-12) pc. We also show that the HI opacity in the LAB data can be accounted for by using an `effective' spin temperature of about 150 K: assuming an optically thin regime leads to underestimate the HI mass by about 30%.

23 pages, 24 figures. Accepted by A&A

References in corpus (14)

• High-Resolution Rotation Curves and Galaxy Mass Models from THINGS
• SPARC: Mass Models for 175 Disk Galaxies with Spitzer Photometry and Accurate Rotation Curves
• Dynamical modelling of the Galactic bulge and bar: the Milky Way's bar pattern speed, stellar, and dark matter mass distribution
• The Structure of the Milky Way's Bar Outside the Bulge
• What is Driving the HI Velocity Dispersion?
• The cold gaseous halo of NGC 891
• The Vertical Structure of the Outer Milky Way HI Disk
• Spatial distribution of interstellar gas in the innermost 3 kpc of our Galaxy
• The Spiral Structure of the Outer Milky Way in Hydrogen
• Cepheid Distances to SNe Ia Host Galaxies based on a Revised Photometric Zero-Point of the HST-WFPC2 and New P-L Relations and Metallicity Corrections
• Dark matter in the Milky Way, II. the HI gas distribution as a tracer of the gravitational potential
• Gas flow models in the Milky Way embedded bars
• A Wide-field High Resolution HI Mosaic of Messier 31: I. Opaque Atomic Gas and Star Formation Rate Density
• Recognizing the fingerprints of the Galactic bar: a quantitative approach to comparing model (l,v) distributions to observation

Cited by in corpus (30)

• Gaia Data Release 3: Mapping the asymmetric disc of the Milky Way
• Fast rotating and low-turbulence discs at $z\simeq 4.5$: Dynamical evidence of their evolution into local early-type galaxies
• Evidence for supernova feedback sustaining gas turbulence in nearby star-forming galaxies
• The impact of gas disc flaring on rotation curve decomposition and revisiting baryonic and dark-matter relations for nearby galaxies
• The volumetric star formation law in the Milky Way
• Galactic runaway O and Be stars found using Gaia DR3
• The ALMA-ALPAKA survey II. Evolution of turbulence in galaxy disks across cosmic time: difference between cold and warm gas
• A geostatistical analysis of multiscale metallicity variations in galaxies [I]: Introduction and comparison of high-resolution metallicity maps to an analytic metal transport model
• Bow shocks, bow waves, and dust waves. I. Strong coupling limit
• Spatially Coherent 3D Distributions of HI and CO in the Milky Way
• Fountain-driven gas accretion feeding star formation over the disc of NGC 2403
• Bayesian inference of three-dimensional gas maps: II. Galactic HI
• 3D modeling of the molecular gas kinematics in optically-selected jellyfish galaxies
• Modeling of Spiral Structure in a Multi-Component Milky~Way-Like Galaxy
• Volumetric Star Formation Prescriptions in Vertically Resolved Edge-on Galaxies
• The Panchromatic Hubble Andromeda Treasury XX: The Disk of M31 is Thick
• HI within and around observed and simulated galaxy discs -- Comparing MeerKAT observations with mock data from TNG50 and FIRE-2
• Stability of galaxies across morphological sequence
• Highest-Resolution Rotation Curve of the Inner Milky Way proving the Galactic Shock Wave
• The Black Hole Candidate Swift J1728.9$-$3613 and the Supernova Remnant G351.9$-$0.9
• Testing the Momentum-driven Supernova Feedback Paradigm in M31
• A large, long-lived, slowly-expanding superbubble across the Perseus Arm
• The Correlation Between Dust and Gas Contents in Molecular Clouds
• The Volumetric Star Formation Law in the Almost Edge-on Galaxy NGC 4302 Revealed by ALMA
• The Volumetric Extended-Schmidt Law: A Unity Slope
• The Hierarchical Dynamical State of Molecular Gas from 3 to 300 pc in NGC 253
• Indirect detection of dark matter absorption in the Galactic Center
• Limits on Dark Matter Annihilation from the Shape of Radio Emission in M31
• Molecular cloud matching in CO and dust in M33 II. Physical properties of giant molecular clouds
• The vertical structure of the stellar disk in NGC 551