Cosmic Horizons

An astro-ph post today. I've written previously about some papers that I've published looking at a "new" cosmological model, which is claimed to be superior to the currently favoured model, the ΛCDM  cosmology. This model, known as the R h = ct universe, is supposedly simpler, but in truth, it is not. And what's more, it is not a good description of the Universe we observe. If you're interested, you can read about it  here. So, what's in my new paper. I take a look at a couple of claimed successes of the R h  = ct universe, namely that it explains the birth of quasars and does away with inflation. The crux of my argument is that the presence of matter in the universe actually destroys the claimed successes of this cosmology. What I did is consider four cosmological models, the standard ΛCDM, with a present day matter density of 27% of the total, and a dark energy component making up the rest. The important thing is that the dark energy has an  equatio...

PhD student, Hugh Garsden, postdoc, Nick Bate, and I just had a paper accepted for publication in MNRAS. As you can see by the title, we combine two separate astrophysical techniques to probe the inner regions of quasars, namely gravitational microlesing. I don't have much time this week (too much teaching and paperwork to do), but will expand on these in the near future. In summary, microlensing accounts for the gravitational lensing due to the myriad of compact objects, be they stars, planets or black holes, as they pass through the line of sight. Unlike the relatively boring microlensing within the galactic halo, this microlensing results on beautiful and complex magnification maps; Reverberation mapping happens when a flare from the central engine of a quasar, typically thought to be an accretion disk orbiting a supermassive black hole, propagates through surrounding clouds of high velocity material, the Broad Line Region. I pinched the below picture from Brendon Brewer'...

A quasar has been found at a redshift of 7.1 . While this is not the most distant object discovered (there are gamma-ray bursts and galaxies that have been found at a higher redshift), it is considerably brighter, has a lovely spectrum and comes with some very pretty graphics; The lead on the paper is  Dan Mortlock . I've known Dan for years; he was a PhD student at Melbourne when I visited in in 1995 (I was finishing up my thesis at the time). Excellent result.