Turbulent Pressure Heats Gas and Suppresses Star Formation in Galactic Bar Molecular Clouds

Abstract

The Central Molecular Zone (CMZ) of the Milky Way is fed by gas inflows from the Galactic disk along almost radial trajectories aligned with the major axis of the Galactic bar. However, despite being fundamental to all processes in the nucleus of the galaxy, these inflows have been studied significantly less than the CMZ itself. We present observations of various molecular lines between 215 and 230 GHz for 20 clouds with $|\ell |<10^{\circ }$, which are candidates for clouds in the Galactic bar due to their warm temperatures and broad lines relative to typical Galactic disk clouds, using the Atacama Large Millimeter/submillimeter Array (ALMA) Atacama Compact Array (ACA). We measure gas temperatures, shocks, star formation rates, turbulent Mach numbers, and masses for these clouds. Although some clouds may be in the Galactic disk despite their atypical properties, nine clouds are likely associated with regions in the Galactic bar, and in these clouds, turbulent pressure is suppressing star formation. In clouds with no detected star formation, turbulence is the dominant heating mechanism, whereas photo-electric processes heat the star-forming clouds. We find that the ammonia (NH${}_3$) and formaldehyde (H${}_2$CO) temperatures probe different gas components, and in general each transition appears to trace different molecular gas phases within the clouds. We also measure the CO-to-H${}_2$ X-factor in the bar to be an order of magnitude lower than the typical Galactic value. These observations provide evidence that molecular clouds achieve CMZ-like properties before reaching the CMZ

arXiv comment42 pages, 22 figures. Updated to match published version

References in corpus (90)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• The Gaia mission
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• Gaia Data Release 3: Summary of the content and survey properties
• Starburst99: Synthesis Models for Galaxies with Active Star Formation
• The Infrared Array Camera (IRAC) for the Spitzer Space Telescope
• Control of star formation by supersonic turbulence
• A computer program for fast non-LTE analysis of interstellar line spectra
• The Galaxy in Context: Structural, Kinematic and Integrated Properties
• Trigonometric Parallaxes of High Mass Star Forming Regions: the Structure and Kinematics of the Milky Way
• A new calibration of stellar parameters of Galactic O stars
• CASA, the Common Astronomy Software Applications for Radio Astronomy
• The Calibration of Mid-Infrared Star Formation Rate Indicators
• Calibrating Extinction-Free Star Formation Rate Diagnostics with 33GHz Free-Free Emission in NGC6946
• A geometric distance measurement to the Galactic Center black hole with 0.3% uncertainty
• Chandra X-ray Spectroscopic Imaging of Sgr A* and the Central Parsec of the Galaxy
• HERACLES: The HERA CO-Line Extragalactic Survey
• MAMBO Mapping of Spitzer c2d Small Clouds and Cores
• The Critical Density and the Effective Excitation Density of Commonly Observed Molecular Dense Gas Tracers
• How to Calculate Molecular Column Density
• The Structure of the Milky Way's Bar Outside the Bulge
• ATLASGAL --- properties of a complete sample of Galactic clumps
• Variations in the Galactic star formation rate and density thresholds for star formation
• What controls star formation in the central 500 pc of the Galaxy?
• Herschel Survey of Galactic OH+, H2O+, and H3O+: Probing the Molecular Hydrogen Fraction and Cosmic-Ray Ionization Rate
• Dense gas in the Galactic central molecular zone is warm and heated by turbulence
• Molecular gas kinematics within the central 250 pc of the Milky Way
• Spatial distribution of interstellar gas in the innermost 3 kpc of our Galaxy
• Diffuse X-ray Emission in a Deep Chandra Image of the Galactic Center
• Spatially Resolved Chemistry in Nearby Galaxies I. The Center of IC 342
• The link between turbulence, magnetic fields, filaments, and star formation in the Central Molecular Zone cloud G0.253+0.016
• Hot and Diffuse Clouds near the Galactic Center Probed by Metastable H3+
• The H_2O southern Galactic Plane Survey (HOPS): I. Techniques and H_2O maser data
• Star formation rates and efficiencies in the Galactic Centre
• The Post-Shock Chemical Lifetimes of Outflow Tracers and a Possible New Mechanism to Produce Water Ice Mantles
• Spectral imaging of the Central Molecular Zone in multiple 3-mm molecular lines
• The Electron Temperature Gradient in the Galactic Disk
• The thermal state of molecular clouds in the Galactic Center: evidence for non-photon-driven heating
• Direct Measurement of the Ratio of Carbon Monoxide to Molecular Hydrogen in the Diffuse Interstellar Medium
• Stellar structures, molecular gas, and star formation across the PHANGS sample of nearby galaxies
• Radio Continuum and Recombination Line Study of UC HII Regions with Extended Envelopes
• The Galactic Center Molecular Cloud Survey. I. A Steep Linewidth-Size Relation & Suppression of Star Formation
• Gas flow in barred potentials
• The Milky Way bar and bulge revealed by APOGEE DR16 and Gaia EDR3
• The Early Evolution of Massive Stars: Radio Recombination Line Spectra
• ATOMS: ALMA Three-millimeter Observations of Massive Star-forming regions -- I. Survey description and a first look at G9.62+0.19
• 'The Brick' is not a brick: A comprehensive study of the structure and dynamics of the Central Molecular Zone cloud G0.253+0.016
• Radio Recombination Lines in Galactic HII Regions
• Absorption Line Survey of H3+ toward the Galactic Center Sources II. Eight Infrared Sources within 30 pc of the Galactic Center
• ALMA-IMF I -- Investigating the origin of stellar masses: Introduction to the Large Program and first results
• Mass inflow rate into the Central Molecular Zone: observational determination and evidence of episodic accretion
• The H2O southern Galactic Plane Survey(HOPS): NH3 (1,1) and (2,2) catalogues
• The Temperature Distribution of Dense Molecular Gas in the Center of NGC 253
• The size--density relation of extragalactic HII regions
• Gas dynamics in the Milky Way: a low pattern speed model
• The Central 300 pc of the Galaxy probed by infrared spectra of H${}_3^{+}$ and CO: part I. Predominance of warm and diffuse gas and high H${}_2$ ionization rate
• Cosmic-Ray Heating of Molecular Gas in the Nuclear Disk: Low Star Formation Efficiency
• Molecular Gas and Star Formation in the Nucleus of IC 342:C${}^{18}$O and Millimeter Continuum Imaging
• The geometry of the gas surrounding the Central Molecular Zone: on the origin of localised molecular clouds with extreme velocity dispersions
• Stellar population constraints on the ages of galactic bars
• The stellar mass distribution of the Milky Way's bar: an analytic model
• The Dense Gas Fraction in Galactic Center Clouds
• Effect of bars on the galaxy properties
• Nuclear Bar Catalyzed Star Formation: 13^CO, C18^O and Molecular Gas Properties in the Nucleus of Maffei 2
• Dynamically constraining the length of the Milky Way bar
• H2O Southern Galactic Plane Survey (HOPS): Paper III - Properties of Dense Molecular Gas across the Inner Milky Way
• Dynamically Driven Inflow onto the Galactic Center and its Effect upon Molecular Clouds
• The large scale dust lanes of the Galactic bar
• Fermi-LAT observations of the Sagittarius B complex
• Submm Recombination Lines in Dust-Obscured Starbursts and AGN
• Kinetic temperature of massive star-forming molecular clumps measured with formaldehyde. III. The Orion Molecular Cloud 1
• Characterisation of the Mopra Radio Telescope at 16--50 GHz
• Statistical Study of the Star Formation Efficiency in Bars: Is Star Formation Suppressed in Gas-Rich Bars?
• The SEDIGISM survey: a search for molecular outflows
• CO Multi-line Imaging of Nearby Galaxies (COMING): VI. Radial variations in star formation efficiency
• Suzaku Detection of Extended/Diffuse Hard X-Ray Emission from the Galactic Center
• Merger-induced Shocks in the Nearby LIRG VV 114 through Methanol Observations with ALMA
• Cyanoacetylene in IC 342: An Evolving Dense Gas Component with Starburst Age
• HI Absorption Toward HII Regions at Small Galactic Longitudes
• Spatially Resolved Chemistry in Nearby Galaxies III. Dense Molecular Gas in the Inner Disk of the LIRG IRAS 04296+2923
• Molecular gas and star formation within 12 strong galactic bars observed with IRAM-30m
• Tests of star formation metrics in the low metallicity galaxy NGC 5253 using ALMA observations of H30$\alpha$ line emission
• Atomic and molecular gas properties during cloud formation
• New detections of (sub)millimeter hydrogen radio recombination lines towards high-mass star-forming clumps
• Recombination Lines and Molecular Gas from Hypercompact HII regions in W51 A
• Star forming activity in the H II regions associated with IRAS 17160-3707 complex
• Evidence of a Cloud-Cloud Collision from Overshooting Gas in the Galactic Center
• Living on the edge of the Central Molecular Zone: G1.3 is the more likely candidate for gas accretion into the CMZ
• Benchmarking the IRDC G351.77-0.53: Gaia DR3 distance, mass distribution, and star formation content

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