Astrobites | 2018 Jul 09
Jamila Pegues wrote:
One of the biggest mysteries of astronomy focuses on, quite fittingly, the absolute biggest astronomical phenomenon we know of: the universe, how it came to be, and where it could possibly be going. To learn more about the evolutionary timeline of the universe, scientists measure the redshifts of far-away objects like black holes and galaxies. In a surreal (and really cool) way, these far-away objects and their redshifts give us snapshots in time of how the universe looked long, long, long ago.
In today’s astrobite, we focus on one particular group of these far-away objects: active galactic nuclei. An active galaxy is a galaxy that has a central core giving off substantial amounts of energy. This core is what’s known as an active galactic nucleus – or AGN for short.
The authors of today’s paper highlighted two ways that scientists measure the redshifts of typical, not-active galaxies. One way is through spectroscopy, which uses the observed spectrum of a galaxy to measure the redshift. Unfortunately this way is pretty costly, and doesn’t work well on a galactic spectrum that is faint at near-infrared and optical wavelengths. The more common way is through photometry, which counts the number of photons, within a given energy band or range, that emit from the galaxy and are collected by a telescope. Given enough different energy bands, scientists can use photometry to construct a low-resolution spectrum of a galaxy and measure the redshift. ...
XZ: Deriving redshifts from X-ray spectra of obscured AGN - Charlotte Simmonds et al
- arXiv.org > astro-ph > arXiv:1807.01782 > 04 Jul 2018