Hydrogen Ionization in Cosmic Webs Probed By Quasar Light

by Tommy on 11/05/2017
Cosmic Web Void Filament Structure

Cosmic Web Void Filament Structure

I’m reduced to science reporting by blog, press release and main stream media.

This new science publishing paradigm is even catching up to Arxiv and Scholar.


University of California Santa Barbara Press Release

Measurement of the small-scale structure of the intergalactic medium using close quasar pairs, Alberto Rorai1, Joseph F. Hennawi, Jose Oñorbe, Martin White, J. Xavier Prochaska, Girish Kulkarni, Michael Walther, Zarija Lukić and Khee-Gan Lee, Science, 356, 6336, 418-422 (28 April 2017), DOI:10.1126/science.aaf9346

Space between galaxies is filled with a tenuous gas known as the intergalactic medium (IGM). The presence of hydrogen atoms in the IGM at different redshifts imprints a series of absorption lines in the spectra of background quasars. Rorai et al. studied pairs of closely spaced quasars and quantified how similar their absorption lines are as a function of transverse separation and redshift. They thus assessed the smoothness of the IGM on relatively small scales—several times the size of a galaxy. The results constrain interactions between galaxies and the IGM, such as heating by ultraviolet photons.

The distribution of diffuse gas in the intergalactic medium (IGM) imprints a series of hydrogen absorption lines on the spectra of distant background quasars known as the Lyman-α forest. Cosmological hydrodynamical simulations predict that IGM density fluctuations are suppressed below a characteristic scale where thermal pressure balances gravity. We measured this pressure-smoothing scale by quantifying absorption correlations in a sample of close quasar pairs. We compared our measurements to hydrodynamical simulations, where pressure smoothing is determined by the integrated thermal history of the IGM. Our findings are consistent with standard models for photoionization heating by the ultraviolet radiation backgrounds that reionized the universe.

Now Julie Cohen just needs to work on writing up the actual citation to the paper.

In addition to an embedded link, I’d like the cite.

Bad Julie! Very bad Julie!


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