Constraining the temperature-density relation of the intergalactic medium with the Lyman-$\alpha$ and $\beta$ 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 $\gamma$. We describe a new method to measure $\gamma$ using the ratio of flux curvature in the Lyman-$\alpha$ and $\beta$ forests. At a given redshift, this curvature ratio incorporates information from the different gas densities traced by Lyman-$\alpha$ and $\beta$ 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 $\gamma$ 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-$\alpha$ forest will require further, detailed forward modelling.

5 pages, 4 figures, accepted for publication in MNRAS LETTER, Added a reference

References in corpus (9)

• Model-independent evidence in favor of an end to reionization by z~6
• HeII Reionization and its Effect on the IGM
• Possible evidence for an inverted temperature-density relation in the intergalactic medium from the flux distribution of the Lyman-alpha forest
• The photoheating of the intergalactic medium in synthesis models of the UV background
• The thermal history of the intergalactic medium down to redshift z=1.5: a new curvature measurement
• On the intergalactic temperature-density relation
• IGM Constraints from the SDSS-III/BOSS DR9 Ly-alpha Forest Flux Probability Distribution Function
• Measuring the equation of state of the high-z intergalactic medium using curvature statistics
• The Lyman-beta forest as a cosmic thermometer

Cited by in corpus (9)

• Revealing reionization with the thermal history of the intergalactic medium: new constraints from the Lyman-$\alpha$ flux power spectrum
• A New Precision Measurement of the Small-Scale Line-of-Sight Power Spectrum of the Ly$\alpha$ Forest
• Inferring the IGM thermal history during reionisation with the Lyman-$\alpha$ forest power spectrum at redshift $z\simeq 5$
• A new Measurement of the Intergalactic Temperature at $z\sim 2.55-2.95$
• Exploring the Thermal State of the Low-Density Intergalactic Medium at z=3 with an Ultra-High Signal-to-Noise QSO Spectrum
• A measurement of the Lyman-beta forest power spectrum and its cross with the Lyman-alpha forest in X-Shooter XQ-100
• Probing helium reionization with kinetic Sunyaev Zel'dovich tomography
• On the Physical Nature of Ly$\alpha$ Transmission Spikes in High Redshift Quasar Spectra
• Emergence of the Temperature-Density Relation in the Low-Density Intergalactic Medium