Fredagskollokvium: Cosmology with CLASS: Future determination of ionization history from the CMB

Duncan Watts, Institute of Theoretical Astrophysics, UiO.

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Duncan Watts, Postdoctoral Fellow at Institute of Theoretical Astrophysics, UiO.

Cosmic microwave background (CMB) photons are partially polarized, both by free electrons around recombination, and by free electrons from recombination. The free electron fraction as a function of redshift directly affects the observed large-scale polarized CMB, by changing both the amplitude and the shape of the E-mode power spectrum.
Planck and WMAP have constrained the reionization optical depth, but this integrated quantity can only constrain the redshift of reionization assuming the intergalactic medium (IGM) instantaneously transitions from neutral to ionized. 
In this talk, I will introduce the Cosmology Large Angular Scale Surveyor (CLASS) and discuss its projected constraints on the reionization history of the universe. Specifically, I will consider a simple model with a period of an early ionization fraction of 5% atz∼28 in addition to the standard reionization scenario. I will also demonstrate that a cosmic variance measurement requires a moderate sensitivity of 10μK arcmin, and will be achieved by the CLASS experiment.
Bildet kan inneholde: himmel, natt, observatorium, rom, vitenskap.
Long exposure image of CLASS telescope at night, with Milky Way Galaxy in background. Credits: Matthew Petroff.

Please join via Zoom at

Meeting ID: 637 8575 4162
Passcode: 882009

Attendees will be muted during the colloquium, but will have the opportunity to ask questions at the end by clicking on the "raise hand” button (or send a request to me via chat).


Emneord: Cosmic Microwave Background (CMB), Experiments, Cosmology
Publisert 6. jan. 2020 21:26 - Sist endret 2. okt. 2020 08:58