Living on the edge of the Central Molecular Zone: G1.3 is the more likely candidate for gas accretion into the CMZ

Abstract

The 1.3deg (G1.3) and 1.6deg (G1.6) cloud complexes in the Central Molecular Zone (CMZ) of our Galaxy have been proposed to possibly reside at the intersection region of the X1 and X2 orbits for several reasons. This includes the detection of co-spatial low- and high-velocity clouds, high velocity dispersion, high fractional molecular abundances of shock-tracing molecules, and kinetic temperatures that are higher than for usual CMZ clouds. We mapped both cloud complexes in molecular lines in the frequency range from 85 to 475GHz with the IRAM 30m and the APEX 12m telescopes. The kinematic structure of G1.3 reveals an `emission bridge' at intermediate velocities (~150km/s) connecting low-velocity (~100km/s) and high-velocity (~180km/s) gas and an overall fluffy shell-like structure. These may represent observational evidence of cloud-cloud interactions. Low- and high-velocity gas components in G1.6 do not show such evidence of interaction, suggesting that they are spatially separated. We selected three positions in each cloud complex for further analysis. Based on non-LTE modelling of an ensemble of CH3CN lines, we derived kinetic temperatures of 60-100K and H2 volume densities of 10${}^4$-10${}^5$cm-3 in both complexes. Molecular abundances relative to H2 suggest a similar chemistry of the two clouds, which is moreover similar to that of other GC clouds. We conclude that G1.3 may indeed exhibit signs of cloud-cloud interactions. We propose an interaction of gas that is accreted from the near-side dust lane to the CMZ, with gas pre-existing at this location. Low- and high-velocity components in G1.6 are rather coincidentally observed along the same line of sight. They may be associated with either overshot decelerated gas from the far-side dust line or actual CMZ gas and high-velocity gas moving on a dust lane. These scenarios would be in agreement with numerical simulations.

arXiv commentAccepted for publication in A&A

References in corpus (71)

• Array Programming with NumPy
• Binary companions of evolved stars in APOGEE DR14: Search method and catalog of ~5,000 companions
• A computer program for fast non-LTE analysis of interstellar line spectra
• An atomic and molecular database for analysis of submillimetre line observations
• The Cologne Database for Molecular Spectroscopy, CDMS, in the Virtual Atomic and Molecular Data Centre, VAMDC
• ATLASGAL - The APEX Telescope Large Area Survey of the Galaxy at 870 microns
• The Critical Density and the Effective Excitation Density of Commonly Observed Molecular Dense Gas Tracers
• A 100-parsec elliptical and twisted ring of cold and dense molecular clouds revealed by Herschel around the Galactic Center
• Variations in the Galactic star formation rate and density thresholds for star formation
• Massive Stars in the Quintuplet Cluster
• Massive Stars in the Arches Cluster
• What controls star formation in the central 500 pc of the Galaxy?
• Hi-GAL, the Herschel infrared Galactic Plane Survey: photometric maps and compact source catalogues. First data release for Inner Milky Way: +68°> l > -70°
• High-resolution wide-band Fast Fourier Transform spectrometers
• The dynamical evolution of molecular clouds near the Galactic Centre - I. Orbital structure and evolutionary timeline
• Dense gas in the Galactic central molecular zone is warm and heated by turbulence
• Improved GRAVITY astrometric accuracy from modeling of optical aberrations
• Gas flow models in the Milky Way embedded bars
• SiO emission from the Galactic Center Molecular Clouds
• The thermal state of molecular clouds in the Galactic Center: evidence for non-photon-driven heating
• Isolating signatures of major cloud-cloud collisions using position-velocity diagrams
• Cloud-cloud collisions and triggered star formation
• The Galactic Center Molecular Cloud Survey. I. A Steep Linewidth-Size Relation & Suppression of Star Formation
• The PHANGS-HST Survey: Physics at High Angular resolution in Nearby GalaxieS with the Hubble Space Telescope
• Far-Infrared Dust Temperatures and Column Densities of the MALT90 Molecular Clump Sample
• Gas flow in barred potentials
• The Bolocam Galactic Plane Survey IV: 1.1 and 0.35 mm Dust Continuum Emission in the Galactic Center Region
• A Molecular Face-on View of the Galactic Centre Region
• Simulations of the Milky Way's central molecular zone -- I. Gas dynamics
• A new look at the molecular gas in M42 and M43; possible evidence for cloud-cloud collision which triggered formation of the OB stars in the Orion Nebula Cluster
• Isolating signatures of major cloud-cloud collisions II: The lifetimes of broad bridge features
• Simulations of the Milky Way's central molecular zone -- II. Star formation
• Cloud-cloud collision as drivers of the chemical complexity in Galactic Centre molecular clouds
• Physical characteristics of bright Class I methanol masers
• Recent star formation in the inner Galactic Bulge seen by ISOGAL II -- The Central Molecular Zone
• Warm H2 in the Galactic center region
• Towards open and reproducible multi-instrument analysis in gamma-ray astronomy
• On the temperature structure of the Galactic Centre cloud G0.253+0.016
• Nuclear Spirals in the inner Milky Way
• The geometry of the gas surrounding the Central Molecular Zone: on the origin of localised molecular clouds with extreme velocity dispersions
• CMZoom: Survey Overview and First Data Release
• ATCA Survey of Ammonia in the Galactic Center: The Temperatures of Dense Gas Clumps between SgrA* and SgrB2
• A survey of the Galactic center region in HCO+, H13CO+ and SiO
• The Galactic Center Molecular Cloud Survey. II. A Lack of Dense Gas & Cloud Evolution along Galactic Center Orbits
• Cloud-cloud collisions in the common foot point of molecular loops 1 and 2 in the Galactic Center
• Coupling the dynamics and the molecular chemistry in the Galactic center
• Tracing gas accretion in the Galactic center using isotopic ratios
• C18O, 13CO, and 12CO abundances and excitation temperatures in the Orion B molecular cloud: An analysis of the precision achievable when modeling spectral line within the Local Thermodynamic Equilibrium approximation
• CHIMPS2: Survey description and ${}^{12}$CO emission in the Galactic Centre
• Molecular shock tracers in NGC 1068: SiO and HNCO
• 3 mm spectral line survey of two lines of sight toward two typical cloud complexes in the Galactic Center
• Formation of the young compact cluster GM 24 triggered by a cloud-cloud collision
• Temperature structures in Galactic Center clouds - Direct evidence for gas heating via turbulence
• Molecules in G1.6-0.025 - 'Hot' Chemistry in the Absence of Star Formation at the Periphery of the Galactic Center Region
• High-mass star formation in Orion B triggered by cloud-cloud collision: Merging molecular clouds in NGC 2024
• Chemistry of the High-Mass Protostellar Molecular Clump IRAS 16562-3959
• CMZoom II: Catalog of Compact Submillimeter Dust Continuum Sources in the Milky Way's Central Molecular Zone
• ALMA CO Observations of a Giant Molecular Cloud in M33: Evidence for High-Mass Star Formation Triggered by Cloud-Cloud Collisions
• Sulphur and carbon isotopes towards Galactic centre clouds
• The centres of M83 and the Milky Way: opposite extremes of a common star formation cycle
• Chemical evolution along the circumnuclear ring of M83
• Deuterium fractionation as a multi-phase component tracer in the Galactic Centre
• A global view on star formation: The GLOSTAR Galactic plane survey IV. Radio continuum detections of young stellar objects in the Galactic Centre region
• Kinetic temperatures toward X1/X2 orbit interceptions regions and Giant Molecular Loops in the Galactic center region
• Hot Molecular Gas in the Circumnuclear Disk
• The foot points of the Giant Molecular Loops in the Galactic center region
• Morphological and Kinematical Analysis of the Double-barred Galaxy NGC 3504 Using ALMA CO (2-1) Data
• New Look at the Molecular Superbubble Candidate in the Galactic Center
• Warm molecular gas in the Galactic center region
• The Central 300 pc of the Galaxy Probed by Infrared Spectra of H${}_3^{+}$ and CO: III. Locations of Sgr B2 and Star $\iota$
• One-kpc Expanding Cylinder of HI-Gas around the Galactic Center

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• Turbulent Pressure Heats Gas and Suppresses Star Formation in Galactic Bar Molecular Clouds
• Parabolic-like Trend in SiO Ratios throughout the Central Molecular Zone: Possible Signature of a Past Nuclear Activity in the Galactic Center