Molecular Gas and Star Formation Properties in the Central and Bar Regions of NGC 6946

Abstract

In this work, we investigate the molecular gas and star formation properties in the barred spiral galaxy NGC 6946 using multiple molecular lines and star formation tracers. High-resolution image (100 pc) of ${}^{13}$CO (1-0) is created by single dish NRO45 and interferometer CARMA for the inner 2 kpc disk, which includes the central region (nuclear ring and bar) and the offset ridges of the primary bar. Single dish HCN (1-0) observations were also made to constrain the amount of dense gas. Physical properties of molecular gas are inferred by (1) the Large Velocity Gradient (LVG) calculations using our observations and archival ${}^{12}$CO (1-0), ${}^{12}$CO(2-1) data, (2) dense gas fraction suggested by HCN to ${}^{12}$CO (1-0) luminosity ratio, and (3) infrared color. The results show that the molecular gas in the central region is warmer and denser than that of the offset ridges. Dense gas fraction of the central region is similar with that of LIRGs/ULIRGs, while the offset ridges are close to the global average of normal galaxies. The coolest and least dense region is found in a spiral-like structure, which was misunderstood to be part of the southern primary bar in previous low-resolution observations. Star formation efficiency (SFE) changes by ~ 5 times in the inner disk. The variation of SFE agrees with the prediction in terms of star formation regulated by galactic bar. We find a consistency between star-forming region and the temperature inferred by the infrared color, suggesting that the distribution of sub-kpc scale temperature is driven by star formation.

arXiv comment14 pages, 12 figures, accepted for publication in ApJ

References in corpus (53)

• The CO-to-H2 Conversion Factor
• The Star Formation Efficiency in Nearby Galaxies: Measuring Where Gas Forms Stars Effectively
• The Star Formation Law in Nearby Galaxies on Sub-Kpc Scales
• THINGS: The HI Nearby Galaxy Survey
• SINGS: The SIRTF Nearby Galaxies Survey
• The Star Formation Rate and Dense Molecular Gas in Galaxies
• The Calibration of Mid-Infrared Star Formation Rate Indicators
• HERACLES: The HERA CO-Line Extragalactic Survey
• Star Formation in NGC 5194 (M51a). II. The Spatially-Resolved Star Formation Law
• The Resolved Properties of Extragalactic Giant Molecular Clouds
• KINGFISH -- Key Insights on Nearby Galaxies: A Far-Infrared Survey with Herschel: Survey Description and Image Atlas
• Star Formation in NGC5194 (M51a): The Panchromatic View from GALEX to Spitzer
• Rotational quenching of CO due to H${}_2$ collisions
• Cluster-formation in the Rosette molecular cloud at the junctions of filaments
• Bar-driven Transport of Molecular Gas to Galactic Centers and Its Consequences
• Star Formation Rates in Molecular Clouds and the Nature of the Extragalactic Scaling Relations
• Bulgeless Giant Galaxies Challenge our Picture of Galaxy Formation by Hierarchical Clustering
• Discovery of Recent Star Formation in the Extreme Outer Regions of Disk Galaxies
• Triggered massive-star formation on the borders of Galactic HII regions. I. A search for `collect and collapse' candidates
• A Comparative Study of Giant Molecular Clouds in M51, M33 and the Large Magellanic Cloud
• Dynamically Driven Evolution of the Interstellar Medium in M51
• Molecular Gas and Star Formation in Bars of Nearby Spiral Galaxies
• On-The-Fly Observing System of the Nobeyama 45-m and ASTE 10-m Telescopes
• A simple and accurate approximation for the Q stability parameter in multi-component and realistically thick discs
• A Mapping Survey of the 12CO and 13CO Emission in Galaxies
• Molecular Gas, Dust and Star Formation in the Barred Spiral NGC 5383
• Bar Diagnostics in Edge-On Spiral Galaxies. II. Hydrodynamical Simulations
• Millimeter Interferometric HCN(1-0) and HCO+(1-0) Observations of Luminous Infrared Galaxies
• Resolved Giant Molecular Clouds in Nearby Spiral Galaxies: Insights from the CANON CO (1-0) Survey
• Submillimeter ALMA Observations of the Dense Gas in the Low-Luminosity Type-1 Active Nucleus of NGC 1097
• Molecular Gas Dynamics in NGC 6946: a Bar-driven Nuclear Starburst "Caught in the Act"
• Physical Conditions in Molecular Clouds in the Arm and Interarm Regions of M51
• Ionized gas kinematics and massive star formation in NGC 1530
• Star formation efficiency in the Barred Spiral Galaxy NGC 4303
• CO(1-0) imaging of M51 with CARMA and NRO45
• Dynamically Influenced Molecular Clouds in the Nucleus of NGC 6946: Variations in the CO Isotopic Line Ratios
• Multi-Transition Study of M51's Molecular Gas Spiral Arms
• NMA CO (J=1-0) Observations of the Halpha/Radio Lobe Galaxy NGC 3079: Gas Dynamics in a Weak Bar Potential and Central Massive Core
• Ammonia Thermometry of Star Forming Galaxies
• Resolved Measurements of Xco in NGC 6946
• Coupling the dynamics and the molecular chemistry in the Galactic center
• A New 100-GHz Band Two-Beam Sideband-Separating SIS Receiver for Z-Machine on the NRO 45-m Radio Telescope
• Giant molecular clouds in the non-grand design spiral galaxy NGC 6946
• Quantifying Resonant Structure in NGC 6946 from Two-dimensional Kinematics
• The Virgo CO Survey: VI. Gas Dynamics and Star Formation Along the Bar in NGC 4303
• The variation in molecular gas depletion time among nearby galaxies: II the impact of galaxy internal structures
• ${}^{13}CO(J=1--0)$ Depression in Luminous Starburst Mergers
• Starbursting Nuclear CO Disks of Early-type Spiral Galaxies
• The filling factor - radius relation for 58 HII regions across the disk of NGC6946
• Some like it cold: molecular emission and effective dust temperatures of dense cores in the Pipe Nebula
• Dense and Warm Molecular Gas and Warm Dust in Nearby Galaxies
• Kinematics of Ionised Gas in the Barred Seyfert Galaxy NGC 4151
• The Dense Gas in the Central Kiloparsec of NGC 6946

Cited by in corpus (7)

• The Effect of Galaxy Interactions on Molecular Gas Properties
• SDSS-IV MaNGA: Spatially resolved star formation in barred galaxies
• The distribution of star formation in galactic bars as seen with H$\alpha$ and stacked GALEX UV imaging
• A statistical study of giant molecular clouds traced by ${}^{13}$CO, C${}^{18}$O, CS, and CH${}_3$OH in the disk of NGC 1068 based on ALMA observations
• A 2-3 mm high-resolution molecular line survey towards the centre of the nearby spiral galaxy NGC 6946
• Variation in GMC Association Properties Across Bars, Spiral Arms, Inter-Arms, and Circumnuclear Region of M100 (NGC 4321) Extracted from ALMA Observations
• Submillimeter Array CO(2-1) Imaging of the NGC 6946 Giant Molecular Clouds