Thermal Instabilities and Shattering in the High-redshift WHIM: Convergence Criteria and Implications for Low-metallicity Strong H i Absorbers

Nir Mandelker*, Frank C. Van Den Bosch, Volker Springel, Freeke Van De Voort, Joseph N. Burchett, Iryna S. Butsky, Daisuke Nagai, S. Peng Oh

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

Using a novel suite of cosmological simulations zooming in on a megaparsec-scale intergalactic sheet (pancake) at z ∼ (3-5), we conduct an in-depth study of the thermal properties and H i content of the warm-hot intergalactic medium (WHIM) at those redshifts. The simulations span nearly three orders of magnitude in gas cell mass, ∼(7.7 × 106-1.5 × 104)M o˙, one of the highest-resolution simulations of such a large patch of the intergalactic medium (IGM) to date. At z ∼ 5, a strong accretion shock develops around the pancake. Gas in the postshock region proceeds to cool rapidly, triggering thermal instabilities and generating a multiphase medium. We find the mass, morphology, and distribution of H i in the WHIM to all be unconverged, even at our highest resolution. Interestingly, the lack of convergence is more severe for the less-dense, metal-poor intrapancake medium (IPM) in between filaments and far outside galaxies. With increased resolution, the IPM develops a shattered structure with most of the H i in kiloparsec-scale clouds. From our lowest-to-highest resolution, the covering fraction of metal-poor (Z < 10-3 Z o˙) Lyman-limit systems (N H I > 1017.2cm-2) in the z ∼ 4 IPM increases from ∼(3-15)%, while that of metal-poor damped Lyα absorbers (N H I > 1020cm-2) increases from ∼(0.2-0.6)%, with no sign of convergence. We find that a necessary condition for the formation of a multiphase shattered structure is resolving the cooling length, l cool = c s t cool, at T ∼ 105 K. If this is unresolved, gas "piles up"at T ≲ 105 K and further cooling becomes very inefficient. We conclude that state-of-the-art cosmological simulations are still unable to resolve the multiphase structure of the WHIM, with potentially far-reaching implications.

Original languageAmerican English
Article number115
JournalAstrophysical Journal
Volume923
Issue number1
DOIs
StatePublished - 10 Dec 2021

Bibliographical note

Publisher Copyright:
© 2021. The American Astronomical Society. All rights reserved..

Fingerprint

Dive into the research topics of 'Thermal Instabilities and Shattering in the High-redshift WHIM: Convergence Criteria and Implications for Low-metallicity Strong H i Absorbers'. Together they form a unique fingerprint.

Cite this