The Central Velocity Field in NGC 253 : Possible Indication of a Bar

Abstract

We have investigated whether motion of gas in a bar-like potential can account for the peculiar but systematic velocity field observed in the nuclear region of the starburst galaxy NGC 253. This unusual velocity field with gradients along both major and minor axes was revealed in a high resolution ($1.8^{\arcsec}\times 1.0^{\arcsec}$) H92$\alpha$ recombination line observation by Anantharamiah and Goss (1996). A simple logarithmic potential is used to model the bar. Assuming that the bulk of the gas flows along closed and non-intersecting x1 (bar) and x2 (anti-bar) orbits of the bar potential, we have computed the expected velocity field and position-velocity diagrams and compared them with the observations. A comparison of the integrated CO intensity maps with the spatial distribution of the x1 and x2 orbits in the model indicates that the nuclear molecular gas in NGC 253 lies mainly on the x2 orbits. We also find that the velocity field observed in the central 100 pc region in the H92$\alpha$ recombination line is well accounted for by the bar model if most of the ionized gas resides in the inner x2 orbits. However, the model is unable to explain the velocity field on a larger scale of $\sim 500$ pc observed using the OVRO interferometer with a resolution of $5^{\arcsec}\times 3^{\arcsec}$. The direction of the observed CO velocity field appears twisted compared to the model. We suggest that this perturbation in the velocity field may be due to an accretion event that could have occurred $10^7$ years ago.

26 latex pages, 7 figures, accepted in Astrophysical Journal

References in corpus (3)

• The Nuclear Starburst in NGC 253
• Mid-infrared [NeII] line emission from the nucleus of NGC 253
• The stellar and gaseous kinematics in NGC 253

Cited by in corpus (21)

• A 2 mm spectral line survey of the starburst galaxy NGC 253
• ALMA Reveals the Molecular Medium Fueling the Nearest Nuclear Starburst
• CO (J=7->6) Observations of NGC 253: Cosmic Ray Heated Warm Molecular Gas
• Spatially resolved optical IFU spectroscopy of the inner superwind of NGC 253
• The Temperature Distribution of Dense Molecular Gas in the Center of NGC 253
• The Stellar Kinematic Center and the True Galactic Nucleus of NGC253
• The Structure, Kinematics and Physical Properties of the Molecular Gas in the Starburst Nucleus of NGC 253
• Detection of the 13CO(J=6-5) Transition in the Starburst Galaxy NGC 253
• Shaken, Not Stirred: The Disrupted Disk of the Starburst Galaxy NGC 253
• Water vapor in the starburst galaxy NGC 253: A new nuclear maser?
• The Morpho-Kinematic Architecture of Super Star Clusters in the Center of NGC253
• VLA H53alpha and H92alpha line observations of the central region of NGC 253
• A thorough view of the nuclear region of NGC 253 - Combined Herschel, SOFIA and APEX dataset
• Spitzer-IRS mapping of the inner kpc of NGC 253: Spatial distribution of the Ne III, PAH 11.3 microns and H2 (0-0) S(1) lines and a gradient in the Ne III/Ne II line ratio
• ALCHEMI finds a "shocking" carbon footprint in the starburst galaxy NGC~253
• Near-Infrared Imaging of Barred Halo Dominated Low Surface Brightness Galaxies
• Unveiling Extragalactic Star Formation Using Radio Recombination Lines: An EVLA Pilot Study with NGC 253
• Multi-density model of the ionised gas in NGC 253 using radio recombination lines
• An ALCHEMI inspection of sulphur-bearing species towards the central molecular zone of NGC 253
• Radio recombination lines from obscured quasars with the SKA
• Unveiling Kinematic Structure in the Starburst Heart of NGC 253