eprintid: 25500
rev_number: 18
eprint_status: archive
userid: 4044
dir: disk0/00/02/55/00
datestamp: 2018-10-31 10:16:54
lastmod: 2018-12-20 13:02:16
status_changed: 2018-10-31 10:16:54
type: doctoralThesis
metadata_visibility: show
creators_name: Walther, Michael
title: Monitoring Thermal Evolution in the
Intergalactic Medium over 12 Billion
Years
subjects: ddc-520
divisions: i-130001
divisions: i-851310
adv_faculty: af-13
abstract: The thermal state of the intergalactic medium (IGM) is an important probe of physical
properties for the bulk of gas in the universe. Here, we perform a new measurement
of the thermal state for redshift z ≤ 5.4 covering 12 billion years from the endstage of
reionization to the present day. For this purpose we measure the Lyman-α forest flux
power spectrum based on high resolution quasar spectra from different ground- and
space-based spectrographs, combine this analysis with archival measurements of percent
level precision, analyze hydrodynamical simulations, use powerful statistical techniques
for interpolation, and perform Bayesian inference via Markov chain monte carlo. We
observe a rise in the temperature at mean density from 6000 K at z = 5.4 towards
14 000 K at z = 3.4 followed by a cooldown phase reaching 6000 K at z = 0.03. This
evolution is provides conclusive evidence for photoionization heating due to reionization
of He II, as well as the subsequent cooling of the IGM due to an expanding universe in
concordance with model predictions. The agreement with previous measurements is
good as well, but our analysis supercedes those by accounting for additional parameters
that we marginalize over, and by the vast cosmological timespan our measurement spans.
At the highest redshifts z > 5 we infer lower temperatures than expected from the
standard picture of IGM heating allowing leaving little room for additional smoothing
due to warm dark matter free streaming. Additionally, our measurement for z < 0.5
allows additional constraints on the ultraviolet background in contradiction to previous
claims of a UV underproduction crisis.
date: 2018
id_scheme: DOI
id_number: 10.11588/heidok.00025500
ppn_swb: 1658566475
own_urn: urn:nbn:de:bsz:16-heidok-255005
date_accepted: 2018-10-18
advisor: HASH(0x55fc36c4bb00)
language: eng
bibsort: WALTHERMICMONITORING2018
full_text_status: public
citation:   Walther, Michael  (2018) Monitoring Thermal Evolution in the Intergalactic Medium over 12 Billion Years.  [Dissertation]     
document_url: https://archiv.ub.uni-heidelberg.de/volltextserver/25500/1/Michael_Walther_thesis_as_printed_for_letter_format.pdf