Constraining the temperature-density relation of the intergalactic medium with the Lyman α and β forests
Abstract
The post-reionization thermal state of the intergalactic medium is characterized by a power-law relationship between temperature and density, with a slope determined by the parameter γ. We describe a new method to measure γ using the ratio of flux curvature in the Lyman α and β forests. At a given redshift, this curvature ratio incorporates information from the different gas densities traced by Lyman α and β absorption. It is relatively simple and fast to compute and appears robust against several observational uncertainties. We apply this technique to a sample of 27 high-resolution quasar spectra from the Very Large Telescope. While promising statistical errors on γ appear to be achievable with these spectra, to reach its full potential, the dependence of the curvature ratio on the thermal state of the gas in the foreground Lyman α forest will require further, detailed forward modelling.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- February 2016
- DOI:
- 10.1093/mnrasl/slv172
- arXiv:
- arXiv:1510.08857
- Bibcode:
- 2016MNRAS.456L..79B
- Keywords:
-
- intergalactic medium;
- quasars: absorption lines;
- cosmology: observations;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 5 pages, 4 figures, accepted for publication in MNRAS LETTER, Added a reference