Ultraviolet Signatures of Tidal Interaction in the Giant Spiral Galaxy, M101

Abstract

We present new evidence for tidal interactions having occurred in the disk of M101 in the last 10^8 - 10^9 years. Recent imaging of the far-ultraviolet emission from M101 by the Shuttle-borne Ultraviolet Imaging Telescope (UIT) reveals with unprecedented clarity a disk-wide pattern of multiple linear arm segments (``crooked arms''). The deep FUV image also shows a faint outer spiral arm with a (``curly tail'') feature that appears to loop around the supergiant HII region NGC 5471 - linking this outlying starburst with the rest of the galaxy. These FUV-bright features most likely trace hot O & B-type stars along with scattered light from associated nebular dust. Counterparts of the outermost ``crooked arms'' are evident in maps at visible wavelengths and in the 21-cm line of HI. The inner-disk FUV arms are most closely associated with H$\alpha$ knots and the outer (downstream) sides of CO arms. Comparisons of the ``crooked arm'' and ``curly tail'' morphologies with dynamical simulations yield the greatest similitude, when the non- axisymmetric forcing comes from a combination of ``external interactions'' with one or more companion galaxies and ``internal perturbations'' from massive objects orbiting within the disk. We speculate that NGC 5471 represents one of these ``massive disturbers'' within the disk, whose formation followed from a tidal interaction between M101 and a smaller galaxy.

Paper format (latex); length of paper (8); 4 gif figure files; uses aas2pp4.sty AASTeX macro file; to be published in Part I of the Astrophysical Journal

Cited by in corpus (30)

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• Recent star formation in nearby galaxies from GALEX imaging:M101 and M51
• The HI environment of the M101 group
• Characteristics of Spiral Arms in Late-type Galaxies
• The Red and Featureless Outer Disks of Nearby Spiral Galaxies
• A New Probe of the Molecular Gas in Galaxies: Application to M101
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• Discovery of Extra-Planar HI Clouds and a HI Tail in the M101 Galaxy Group with FAST
• The Dependence of the Hierarchical Distribution of Star Clusters on Galactic Environment
• M101: Spectral Observations of HII Regions and Their Physical Properties
• Far Ultraviolet Imagery of the Edge-On Spiral Galaxy NGC 4631
• Wide-field CO isotopologue emission and the CO-to-H${}_2$ factor across the nearby spiral galaxy M101
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• Deep Narrowband Photometry of the M101 Group: Strong-Line Abundances of 720 HII Regions
• Polygonal Structures in the Gaseous Disk: Numerical Simulations
• Breaking the degeneracy between gas inflow and outflows with stellar metallicity: Insights on M101
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• Gemini Spectra of Star Clusters in the Spiral Galaxy M101
• A Deep Census of Outlying Star Formation in the M101 Group
• A Dynamical Model of the M101 / NGC 5474 Encounter
• A Dynamic Galaxy: Stellar Age Patterns Across the Disk of M101