Atomic Carbon in the Central Molecular Zone of the Milky Way : Possible Cosmic-ray Induced Chemistry or Time-Dependent Chemistry Associated with SNR Sagittarius A East

Abstract

Being one of the most abundant atomic/molecular species observed in dense molecular gas, atomic carbon (${\mathrm{C}}^0$) is a potential good tracer of molecular gas mass in many chemical/physical environments, though the ${\mathrm{C}}^0$ abundance variation outside the Galactic disk region is yet to be fully known. This paper presents a wide-field 500 GHz [CI] map of the Galactic central molecular zone (CMZ) obtained with the ASTE 10-m telescope. Principal component analysis and non-LTE multi-transition analysis have shown that the [CI] emission predominantly originates from the low-excitation gas component with a 20-50 K temperature and $\sim 10^3{\mathrm{cm}}^{-3}$ density, whereas ${\mathrm{C}}^0$ abundance is likely suppressed in the high-excitation gas component. The average $N({\mathrm{C}}^0)$/$N(\mathrm{CO})$ abundance ratio in the CMZ is 0.3-0.4, which is 2-3 times that in the Galactic disk. The $N({\mathrm{C}}^0)$/$N(\mathrm{CO})$ ratio increases to 0.7 in the innermost 10 pc region and to $\sim 2$ in the circumnuclear disk. We discovered ${\mathrm{C}}^0$-rich regions distributed in a ring-shape encircling the supernova remnant (SNR) Sgr A east, indicative that the ${\mathrm{C}}^0$-enrichment in the central 10 pc region is a consequence of a molecular cloud-SNR interaction. In the 15 atom/molecules included in principal component analysis (PCA), CN is the only other species that increases in the [CI]-bright ring. The origin of the [CI]-bright ring is likely a cosmic-ray dominated region created by low-energy cosmic-ray particles accelerated by Sgr A east or primitive molecular gas collected by the SNR in which the ${\mathrm{C}}^0$-to-CO conversion has not reached the equilibrium.

arXiv comment23 pages, 16 figures, accepted for publication in Astrophysical Journal

References in corpus (77)

• An atomic and molecular database for analysis of submillimetre line observations
• Giant Gamma-ray Bubbles from Fermi-LAT: AGN Activity or Bipolar Galactic Wind?
• A geometric distance measurement to the Galactic Center black hole with 0.3% uncertainty
• Diagnostics of irradiated gas in galaxy nuclei. I: A Far-ultraviolet and X-ray dominated region code
• Diagnostics of irradiated dense gas in galaxy nuclei. II. A grid of XDR and PDR models
• A 100-parsec elliptical and twisted ring of cold and dense molecular clouds revealed by Herschel around the Galactic Center
• Broad-band nonthermal emission from molecular clouds illuminated by cosmic rays from nearby supernova remnants
• H3+ in Diffuse Interstellar Clouds: a Tracer for the Cosmic-Ray Ionization Rate
• Herschel Survey of Galactic OH+, H2O+, and H3O+: Probing the Molecular Hydrogen Fraction and Cosmic-Ray Ionization Rate
• 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
• The CI lines as tracers of molecular gas, and their prospects at high redshifts
• Hot and Diffuse Clouds near the Galactic Center Probed by Metastable H3+
• A Chandra Study of Sgr A East: A Supernova Remnant Regulating The Activity Of Our Galactic Center?
• Spectral imaging of the Central Molecular Zone in multiple 3-mm molecular lines
• A cosmic-ray dominated ISM in Ultra Luminous Infrared Galaxies: new initial conditions for star formation
• Discovery of a superluminal Fe K echo at the Galactic Center: The glorious past of Sgr A* preserved by molecular clouds
• A lower limit of 50 microgauss for the magnetic field near the Galactic Centre
• Inflation of 430-parsec bipolar radio bubbles in the Galactic Centre by an energetic event
• Effective destruction of CO by cosmic rays: implications for tracing H${}_2$ gas in the Universe
• The linewidth-size relationship in the dense ISM of the Central Molecular Zone
• CN and HCN in Dense Interstellar Clouds
• Testing the universality of the star formation efficiency in dense molecular gas
• Echoes of multiple outbursts of Sagittarius A* revealed by Chandra
• The AST/RO Survey of the Galactic Center Region. I. The Inner 3 Degrees
• HCN versus HCO+ as dense molecular gas mass tracer in Luminous Infrared Galaxies
• The Survey of Water and Ammonia in the Galactic Center (SWAG): Molecular Cloud Evolution in the Central Molecular Zone
• Absorption Line Survey of H3+ toward the Galactic Center Sources II. Eight Infrared Sources within 30 pc of the Galactic Center
• HNCO enhancement by shocks in the L1157 molecular outflow
• Physical conditions in the central molecular zone inferred by H3+
• Supernova enhanced cosmic ray ionization and induced chemistry in a molecular cloud of W51C
• Neutral Atomic Carbon in Centers of Galaxies
• 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
• APEX mapping of H3O+ in the Sgr B2 region
• X-ray Echo from the Sagittarius C Complex and 500-year Activity History of Sagittarius A*
• Seeding the Galactic Centre gas stream: gravitational instabilities set the initial conditions for the formation of protocluster clouds
• GREAT confirms transient nature of the circumnuclear disk
• Cosmic ray induced ionisation of a molecular cloud shocked by the W28 supernova remnant
• Observing a column-dependent zeta in dense interstellar sources: the case of the Horsehead Nebula
• AST/RO Observations of Atomic Carbon near the Galactic Center
• New places and phases of CO-poor/CI-rich molecular gas in the Universe
• Chemical Features in the Circumnuclear Disk of the Galactic Center
• XMM-Newton observations of Sagittarius A East
• The Galactic Centre in the Far Infrared
• The Dense Gas Fraction in Galactic Center Clouds
• Large-scale mapping observations of the CI(3P1-3P0) and CO(J=3-2) lines toward the Orion A molecular cloud
• GMC Collisions as Triggers of Star Formation. V. Observational Signatures
• ALMA Observations of Multiple-CO and C Lines Toward the Active Galactic Nucleus of NGC 7469: X-Ray-dominated Region Caught in the Act
• Extensive [CI] Mapping toward the Orion-A Molecular Cloud
• Kinematics of Shocked Molecular Gas Adjacent to the Supernova Remnant W44
• Physical Conditions of Molecular Gas in the Galactic Center
• On the physical mechanisms governing the cloud lifecycle in the Central Molecular Zone of the Milky Way
• Mass Supply to Galactic Center due to Nested Bars in the Galaxy
• The relationship between dust and [CI] at z=1 and beyond
• Very Large Array Observations of Galactic Center OH 1720 MHz Masers in Sagittarius A East and in the Circumnuclear Disk
• 12CO 4-3 and [CI] 1-0 at the centers of NGC 4945 and Circinus
• Exploring molecular complexity with ALMA (EMoCA): Complex isocyanides in Sgr B2(N)
• High Atomic Carbon Abundance in Molecular Clouds in the Galactic Center Region
• Spectral-Line Survey at Millimeter and Submillimeter Wavelengths toward an Outflow-Shocked Region, OMC 2-FIR 4
• ALMA Observations of Atomic Carbon [C I] (${{}^3\mathrm{P}}_1\to {{}^3\mathrm{P}}_0$) and Low-$J$ CO Lines in the Starburst Galaxy NGC 1808
• HCN $J$=4-3, HNC $J$=1-0, ${\mathrm{H}}^{13}\mathrm{CN}$ $J$=1-0, and $\mathrm{H}{\mathrm{C}}_3\mathrm{N}$ $J$=10-9 Maps of Galactic Center Region I: Spatially-Resolved Measurements of Physical Conditions and Chemical Composition
• Molecular-Cloud-Scale Chemical Composition III: Constraints of Average Physical Properties through Chemical Models
• ALMA [CI] observations toward the central region of a Seyfert galaxy NGC 613
• ALMA Images of the Host Cloud of the Intermediate-mass Black Hole Candidate CO-0.40-0.22$^* : No Evidence for Cloud-Black Hole Interaction, but Evidence for a Cloud-Cloud Collision
• Atlas of Cosmic ray-induced astrochemistry
• High Velocity Compact Clouds in the Sagittarius C Region
• The Central 300 pc of the Galaxy probed by infrared spectra of H3+ and CO: II. Expansion and morphology of the warm diffuse gas
• Discovery of a [CI]-faint, CO-bright Galaxy: ALMA Observations of the Merging Galaxy NGC 6052
• Warm ISM in the Sgr A Complex. I: Mid-J CO, atomic carbon, ionized atomic carbon,and ionized nitrogen sub-mm/FIR line observations with the Herschel-HIFI and NANTEN2/SMART telescopes
• The FFX Correlator
• CO-0.30-0.07: A Peculiar Molecular Clump with an Extremely Broad Velocity Width
• [CI] 492 GHz mapping toward Cas A
• SMA Observations of the Extended CO(6-5) Emission in the Starburst Galaxy NGC253
• Indications of M-dwarf Deficits in the Halo and Thick Disk of the Galaxy
• Very Large Array monitoring of 1720 MHz OH masers toward the Galactic Center
• HCN $J$=4-3, HNC $J$=1-0, ${\mathrm{H}}^{13}\mathrm{CN}$ $J$=1-0, and $\mathrm{H}{\mathrm{C}}_3\mathrm{N}$ $J$=10-9 Maps of Galactic Center Region II.: Physical Properties of Dense Gas Clumps and Probability of Star Formation
• A Multi-Line Ammonia Survey of the Galactic Center Region with the Tsukuba 32-m Telescope - I. Observations and Data

Cited by in corpus (3)

• Cosmic Ray Interstellar Propagation Tool using Itô Calculus (criptic): software for simultaneous calculation of cosmic ray transport and observational signatures
• Cosmic-ray-driven enhancement of the C${}^0$/CO abundance ratio in W51C
• The Discovery of an Active Wind from the Milky Way's Black Hole