Model of Outgrowths in the Spiral Galaxies NGC 4921 and NGC 7049 and the Origin of Spiral Arms
arXiv:1211.3628 · doi:10.1007/s10509-012-1270-8
Abstract
NGC 4921 and 7049 are two spiral galaxies presenting narrow, distinct dust features. A detailed study of the morphology of those features has been carried out using Hubble Space Telescope archival images. NGC 4921 shows a few but well-defined dust arms midway to its centre while NGC 7049 displays many more dusty features, mainly collected within a ring-shaped formation. Numerous dark and filamentary structures, called outgrowths, are found to protrude from the dusty arms in both galaxies. The outgrowths point both outwards and inwards in the galaxies. Mostly they are found to be V-shaped or Y-shaped with the branches connected to dark arm filaments. Often the stem of the Y appears to consist of intertwined filaments. Remarkably, the outgrowths show considerable similarities to elephant trunks in H II regions. A model of the outgrowths, based on magnetized filaments, is proposed. The model provides explanations of both the shapes and orientations of the outgrowths. Most important, it can also give an account for their intertwined structures. It is found that the longest outgrowths are confusingly similar to dusty spiral arms. This suggests that some of the outgrowths can develop into such arms. The time-scale of the development is estimated to be on the order of the rotation period of the arms or shorter. Similar processes may also take place in other spiral galaxies. If so, the model of the outgrowths can offer a new approach to the old winding problem of spiral arms.
arXiv comment35 pages, 16 figures
References in corpus (26)
- AINUR: Atlas of Images of NUclear Rings
- The properties of the ISM in disc galaxies with stellar feedback
- Formation and Fragmentation of Gaseous Spurs in Spiral Galaxies
- Radiation-magnetohydrodynamic simulations of HII regions and their associated PDRs in turbulent molecular clouds
- Formation of Spiral-Arm Spurs and Bound Clouds in Vertically Stratified Galactic Gas Disks
- Magnetohydronamic Evolution of HII Regions in Molecular Clouds: Simulation Methodology, Tests, and Uniform Media
- Radiation driven implosion and triggered star formation
- Dynamical HII Region Evolution in Turbulent Molecular Clouds
- Global Modeling of Spur Formation in Spiral Galaxies
- Detailed Numerical Simulations on the Formation of Pillars around HII-regions
- Spurs and feathering in spiral galaxies
- Radiation-magnetohydrodynamic simulations of the photoionisation of magnetised globules
- An HST Archival Survey of Feathers in Spiral Galaxies
- Deep Luminosity Functions of Old and Intermediate-Age Globular Clusters in NGC 1316: Evidence for Dynamical Evolution of Second-Generation Globular Clusters
- HST Imaging of the Globular Clusters in the Fornax Cluster: Color and Luminosity Distributions
- Branch, Spur, and Feather Formation in Spiral Galaxies
- The Lifetime of Grand Design
- Effects of Magnetic Fields on Photoionised Pillars and Globules
- Atomic and molecular gas in the merger galaxy NGC 1316 (Fornax A) and its environment
- Minor-axis velocity gradients in spirals and the case of inner polar disks
- Evolution of Blister-Type HII Regions in a Magnetized Medium
- Synthetic observations of simulated pillars of creation
- Magnetic ionization fronts II: Jump conditions for oblique magnetization
- Dust and Ionized Gas Association in E/S0 Galaxies with Dust Lanes: Clues to their Origin
- Dark mammoth trunks in the merging galaxy NGC 1316 and a mechanism of cosmic double helices
- The angular momentum of condensations within elephant trunks
Cited by in corpus (5)
- HST and HI Imaging of Strong Ram Pressure Stripping in the Coma Spiral NGC 4921: Dense Cloud Decoupling and Evidence for Magnetic Binding in the ISM
- HST Imaging of Dust Structures and Stars in the Ram Pressure Stripped Virgo Spirals NGC 4402 and NGC 4522: Stripped from the Outside In with Dense Cloud Decoupling
- Cooling in the X-ray halo of the rotating, massive early-type galaxy NGC 7049
- Globular Clusters and Spur Clusters in NGC 4921, the Brightest Spiral Galaxy in the Coma Cluster
- Molecular gas filaments and fallback in the ram pressure stripped Coma spiral NGC 4921