bystander wrote:Gemstones Askew in the Heavens
astrobites | 2017 Mar 14
Planck's Dusty GEMS. III. A massive lensing galaxy with a
Paddy Alton wrote:
In today’s article I want to take a closer look at gravitational lenses and open a window on some of the interesting science astronomers are using these objects for.
A gravitational lens results from a chance alignment of two galaxies, one near and one far. To understand how it works, we need to take a brief tour through Einstein’s General Theory of Relativity – but don’t panic! I’ll keep it light. In his landmark theory, now over a century old, Einstein outlined the mechanism by which gravity acts. Rather than being a fixed background against which events happen – a sort of cosmic stage – space itself can be warped and stretched by the presence of mass. The more massive the object, the stronger the distortion. The upshot is that anything following a straight path through space, such as a light ray, finds itself travelling a curved path instead when it passes near a mass – as if a force was acting directly upon it. It’s this apparent force that we call gravity. This effect was used in 1919 by Sir Arthur Eddington to confirm the predictions of General Relativity, to much excitement and confusion; during an eclipse, Eddington measured the angle through which the Sun’s gravity deflected the light of distant stars, showing that this matched the theory. In special circumstances, the same effect can focus the deflected light rays, just like a traditional lens ...
bottom-heavy stellar initial mass function at z=1.5
- R. Canameras et al
Paddy Alton wrote:
Following this method, the authors infer that the foreground galaxy is indeed more massive than might be expected from its brightness alone, indicative of an excess of dim dwarf stars. This is consistent with results from galaxies in the nearby universe, which have undergone billions of years of additional evolution, forging a crucial link between local galaxies and their antecedents.
Indeed, we may see an excess of dim dwarf stars in the local universe, too.
Deborah Byrd of EarthSky
Astronomers have peered into eight relatively nearby elliptical galaxies and made a discovery suggesting that small, dim red dwarf stars in these sorts of galaxies might be 20 times more plentiful than in our spiral-shaped Milky Way galaxy.
It may indeed be true that elliptical galaxies contain huge numbers of dim red dwarf stars, boosting the mass of the galaxies considerably but having little impact on the galaxies' light output.