W.M. Keck Observatory | 2015 Apr 29
An international team of astronomers, led by Michele Cappellari from the University of Oxford, has used data gathered by the W. M. Keck Observatory in Hawaii to analyze the motions of stars in the outer parts of elliptical galaxies, in the first such survey to capture large numbers of these galaxies. The team discovered surprising gravitational similarities between spiral and elliptical galaxies, implying the influence of hidden forces. The study will be published in The Astrophysical Journal Letters.[attachment=0]SLUGGS.jpg[/attachment]
The scientists from the USA, Australia, and Europe used the powerful DEIMOS spectrograph installed on the world's largest optical telescope at Keck Observatory to conduct a major survey of nearby galaxies called SLUGGS, which mapped out the speeds of their stars. The team then applied Newton's law of gravity to translate these speed measurements into the amounts of matter distributed within the galaxies.
“The DEIMOS spectrograph was crucial for this discovery since it can take in data from an entire giant galaxy all at once, while at the same time sampling the speeds of its stars at a hundred separate locations with exquisite accuracy,” said Aaron Romanowsky, of San Jose State University.
One of the most important scientific discoveries of the 20th century was that the spectacular spiral galaxies, such as our own Milky Way, rotate much faster than expected, powered by an extra gravitational force of invisible "dark matter" as it is now called. Since this discovery 40 years ago, we have learned that this mysterious substance, which is probably an exotic elementary particle, makes up about 85 percent of the mass in the Universe, leaving only 15 percent to be the ordinary stuff encountered in our everyday lives. Dark matter is central to our understanding of how galaxies form and evolve – and is ultimately one of the reasons for the existence of life on Earth – yet we know almost nothing about it. ...
Small scatter and nearly-isothermal mass profiles to four half-light radii
from two-dimensional stellar dynamics of early-type galaxies - Michele Cappellari et al
- Astrophysical Journal Letters 804(1) L21 (01 May 2015) DOI: 10.1088/2041-8205/804/1/L21
arXiv.org > astro-ph > arXiv:1504.00075 > 01 Apr 2015