Chemical Features in the Circumnuclear Disk of the Galactic Center

Abstract

The circumnuclear disk (CND) of the Galactic Center is exposed to many energetic phenomena coming from the supermassive black hole Sgr A* and stellar activities. These energetic activities can affect the chemical composition in the CND by the interaction with UV-photons, cosmic-rays, X-rays, and shock waves. We aim to constrain the physical conditions present in the CND by chemical modeling of observed molecular species detected towards it. We analyzed a selected set of molecular line data taken toward a position in the southwest lobe of the CND with the IRAM 30m and APEX 12-meter telescopes and derived the column density of each molecule using a large velocity gradient (LVG) analysis. The determined chemical composition is compared with a time-dependent gas-grain chemical model based on the UCL\_CHEM code that includes the effects of shock waves with varying physical parameters. Molecules such as CO, HCN, HCO${}^{+}$, HNC, CS, SO, SiO, NO, CN, H${}_2$CO, HC${}_3$N, N${}_2$H${}^{+}$ and H${}_3$O${}^{+}$ are detected and their column densities are obtained. Total hydrogen densities obtained from LVG analysis range between $2\times 10^4$ and $1\times 10^6$cm${}^{-3}$ and most species indicate values around several $\times 10^5$cm${}^{-3}$, which are lower than values corresponding to the Roche limit, which shows that the CND is tidally unstable. The chemical models show good agreement with the observations in cases where the density is $\sim 10^4$cm${}^{-3}$, the cosmic-ray ionization rate is high, $>10^{-15}$s${}^{-1}$, or shocks with velocities $>40$km s${}^{-1}$ have occurred. Comparison of models and observations favors a scenario where the cosmic-ray ionization rate in the CND is high, but precise effects of other factors such as shocks, density structures, UV-photons and X-rays from the Sgr A* must be examined with higher spatial resolution data.

arXiv comment17 Pages, 13 figures, accepted for publication in A&A

References in corpus (45)

• A computer program for fast non-LTE analysis of interstellar line spectra
• Trigonometric Parallaxes of Massive Star Forming Regions: VI. Galactic Structure, Fundamental Parameters and Non-Circular Motions
• Chandra X-ray Spectroscopic Imaging of Sgr A* and the Central Parsec of the Galaxy
• The Two Young Star Disks in the Central Parsec of the Galaxy: Properties, Dynamics and Formation
• Updated Atomic Data and Calculations for X-ray Spectroscopy
• A model for atomic and molecular interstellar gas: The Meudon PDR code
• Non-thermal desorption from interstellar dust grains via exothermic surface reactions
• Cosmic-ray ionization of molecular clouds
• Evaporation of ices near massive stars: models based on laboratory TPD data
• Polycylcic Aromatic Hydrocarbons (PAH's) in dense cloud chemistry
• The nuclear star cluster of the Milky Way: proper motions and mass
• HCN and HCO+ Observations of the Galactic Circumnuclear Disk
• SiO line emission from C-type shock waves : interstellar jets and outflows
• The largest oxigen bearing organic molecule repository
• Discovery of a superluminal Fe K echo at the Galactic Center: The glorious past of Sgr A* preserved by molecular clouds
• Parametrization of C-shocks. Evolution of the Sputtering of Grains
• SiO emission from the Galactic Center Molecular Clouds
• Iron and Nickel Line Diagnostics for the Galactic Center Diffuse Emission
• The thermal state of molecular clouds in the Galactic Center: evidence for non-photon-driven heating
• Hard X-ray view of the past activity of Sgr A* in a natural Compton mirror
• Interacting Cosmic Rays with Molecular Clouds: A Bremsstrahlung Origin of Diffuse High Energy Emission from the Inner 2deg by 1deg of the Galactic Center
• Fading hard X-ray emission from the Galactic Centre molecular cloud Sgr B2
• Desorption From Interstellar Ices
• The Origin of Diffuse X-ray and $\gamma$-ray Emission from the Galactic Center Region: Cosmic Ray Particles
• Galactic center at very high-energies
• The HNC/HCN Ratio in Star-Forming Regions
• The Implications of a High Cosmic-Ray Ionization Rate in Diffuse Interstellar Clouds
• Gas infall towards Sgr A* from the clumpy circumnuclear disk
• Absorption Line Survey of H3+ toward the Galactic Center Sources II. Eight Infrared Sources within 30 pc of the Galactic Center
• The Morphology of Hadronic Emission Models for the Gamma-Ray Source at the Galactic Center
• L1157-B1: Water and ammonia as diagnostics of shock temperature
• Traces of past activity in the Galactic Centre
• APEX mapping of H3O+ in the Sgr B2 region
• Surviving the hole I: Spatially resolved chemistry around Sgr A*
• The Excitation of HCN and HCO+ in the Galactic Center Circumnuclear Disk
• GREAT confirms transient nature of the circumnuclear disk
• The X-ray lightcurve of Sgr A* over the past 150 years inferred from Fe-Ka line reverberation in Galactic Centre molecular clouds
• Widespread Methanol Emission from the Galactic Center
• Warm Molecular Gas Traced with CO J=7->6 in the Galaxy's Central 2 Parsecs: Dynamical Heating of the Circumnuclear Disk
• Infrared H3+ and CO Studies of the Galactic Core: GCIRS 3 and GCIRS 1W
• Discovery of K-Shell Emission Lines of Neutral Atoms in the Galactic Center Region
• Mapping photodissociation and shocks in the vicinity of Sgr A*
• H3+ Spectroscopy and the Ionization Rate of Molecular Hydrogen in the Central Few Parsecs of the Galaxy
• An analysis of HCN observations of the Circumnuclear Disk at the galactic centre
• Millimeter-wave Spectral Line Surveys toward the Galactic Circumnuclear Disk and Sgr A*

Cited by in corpus (36)

• Phosphorus-bearing molecules in the Galactic Center
• The chemistry of phosphorus-bearing molecules under energetic phenomena
• Optical Depth Estimates and Effective Critical Densities of Dense Gas Tracers in the Inner Parts of Nearby Galaxy Discs
• CMZoom: Survey Overview and First Data Release
• ALMA Astrochemical Observations of the Infrared-Luminous Merger NGC 3256
• The Circumnuclear Disk Revealed by ALMA. I. Dense Clouds and Tides in the Galactic Center
• ALMA View of the Circum-nuclear Disk of the Galactic Center; Tidally-disrupted Molecular Clouds falling to the Galactic Center
• Dense molecular gas properties on 100 pc scales across the disc of NGC 3627
• Starburst Energy Feedback Seen Through HCO${}^{+}$/HOC${}^{+}$ Emission in NGC 253 from ALCHEMI
• Molecular Gas Feeding the Circumnuclear Disk of the Galactic Center
• Enhanced UV radiation and dense clumps in Mrk231's molecular outflow
• CMZoom II: Catalog of Compact Submillimeter Dust Continuum Sources in the Milky Way's Central Molecular Zone
• 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
• ALMA observations of HCN and HCO+ outflows in the merging galaxy NGC 3256
• Structure and kinematics of shocked gas in Sgr B2: further evidence of a cloud-cloud collision from SiO emission maps
• The First Mid-Infrared Detection of HNC in the Interstellar Medium: Probing the Extreme Environment Towards the Orion Hot Core
• Hot Molecular Gas in the Circumnuclear Disk
• Physical Contact between the +20 km/s Cloud and the Galactic Circumnuclear Disk
• Forming circumnuclear disks and rings in galactic nuclei: a competition between supermassive black hole and nuclear star cluster
• ALCHEMI finds a "shocking" carbon footprint in the starburst galaxy NGC~253
• A study of methanol and silicon monoxide production through episodic explosions of grain mantles in the Central Molecular Zone
• The diffuse molecular component in the nuclear bulge of the Milky Way
• Virial Clumps in Central Molecular Zone Clouds
• Effects of turbulence in the Circumnuclear Disk
• The foot points of the Giant Molecular Loops in the Galactic center region
• Dense Gas and Star Formation in Nearby Infrared Bright Galaxies: APEX survey of HCN and HCO+ J=2-1
• How far actually is the Galactic Center IRS 13E3 from Sagittarius A${}^{\ast }$?
• Impact of an Active Sgr A* on the Synthesis of Water and Organic Molecules Throughout the Milky Way
• Revealing the Physical Conditions around Sgr A* using Bayesian Inference -- I. Observations and Radiative Transfer
• 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
• On the effects of UV photons/X-rays on the chemistry of the Sgr B2 cloud
• Herschel water maps towards the vicinity of the black hole Sgr A*
• Chemical templates of the Central Molecular Zone. Shock and protostellar object signatures under Galactic Center conditions
• The Discovery of an Active Wind from the Milky Way's Black Hole
• From the Circumnuclear Disk in the Galactic Center to thick, obscuring tori of AGNs -- Modelling the molecular emission of a parsec-scale torus as found in NGC1068
• Chemistry of Dark Molecular Clouds