Case Western Reserve University | 2015 Feb 03
Case Western Reserve University astronomers peered deep into space to discover new features of a galaxy that’s been sketched and photographed for 170 years.
The researchers were able to see faint plumes extending from the northeast and south of the nearby spiral galaxy M51a, also called the “Whirlpool Galaxy,” by taking what is essentially a photograph made by a 20-hour exposure.
The image also provides new details of the linear northwest plume, which itself is nearly 120,000 light-years long, and reveals a lack of stars in a portion of the southeast tail. ...
The northwest plume was seen in the 1970s, but the technology provided limited detail. The astronomers found it’s dominated by older, redder stars and has little gas, found in small patches. Due to the age of the stars and the extreme length of the plume, they suggest the plume was created by the interaction of an outer disk of M51 with another galaxy 200 million years ago or more.
The southern plume is an oddity. It has no morphological similarities with the surrounding parts of M51 and no gas. The plume has comparatively few stars and, therefore, mass, and little total light. One possibility, the researchers suggest, is the plume could be the remnants of a third satellite or body in the M51 system.
The northeast plume has about the same total light as the southern one. It may be an extension of the north side of the galaxy, but that is impossible to tell, Watkins said.
Other researchers discovered the southeastern gas tail in 1990 and assumed it was pulled out during an interaction with another galaxy. This new, deeper view still found no stars. That’s unusual for such a tail, but it provides a clear test for future interaction models. ...
The "Whirlpool" -- First Known Spiral Galaxy Yields New Insights
Daily Galaxy | 2015 Feb 04
Deep Imaging of M51: a New View of the Whirlpool's Extended Tidal Debris - Aaron E. Watkins, J. Christopher Mihos, Paul Harding
- Astrophysical Journal Letters 800(1) L3 (10 Feb 2015) DOI: 10.1088/2041-8205/800/1/L3
arXiv.org > astro-ph > arXiv:1501.04599 > 19 Jan 2015