Two BBL Talks On 11/4/2019 (Speakers: JYi-Kuan Chiang, Ohio State University; Nick Kern, University Of California, Berkeley)

Monday November 4, 2019 12:00 pm

Speaker #1 — JYi-Kuan Chiang

Title: Intensity Mapping Tomography: Cosmic UV Background and Beyond

Abstract: Intensity mapping is an emerging way to probe the matter and radiation content in the universe, and the target features do not need to be limited to strong emission lines. I will introduce a highly generic, cross-correlation-based framework to recover previously collapsed redshift information for cosmic photons in intensity maps of arbitrary bandwidths. This enables a tomography of the radiation budget not only across cosmic time but also in frequency space as the photons get redshifted by the cosmic expansion. I will demonstrate this method with data by probing the continuum, Lyα line, and Lyman break in the cosmic UV background up to z~2 using GALEX All Sky and Medium Imaging Surveys. This allows us to perform spectral diagnostics for the entire body of the UV background and provide insights on cosmic star formation, black hole accretion, and potential emission from the diffuse intergalactic medium. We expect this method to be generically applicable for a rich set of existing and upcoming wide-field datasets in probing the cosmic background over a wide range of wavebands and cosmic history.

Speaker #2 — Nick Kern

Title: Data Analysis and Parameter Inference for 21cm Cosmology and the Effort to Detect the Epoch of Reionization with HERA

Abstract: The Hydrogen Epoch of Reionization Array (HERA) is a large, low-frequency radio interferometer currently being built in the Karoo Desert, South Africa. Its goal is to use neutral hydrogen’s 21cm emission from Comic Dawn and the Epoch of Reionization (EoR) at redshifts 6 < z < 25 to probe the formation of the first stars, galaxies, and black holes and understand how their feedback shaped the intergalactic medium (IGM). However, actually measuring the 21 cm signal is a daunting task, as it is buried under astrophysical foregrounds, instrumental contamination and thermal noise. In this talk, I will discuss the development and application of novel techniques for instrumental calibration and systematic mitigation for HERA Phase I en route to its first limit on the 21cm power spectrum at the EoR. Another challenge we face is accurate modeling of the 21cm signal at speeds fast enough to explore the weakly constrained parameter space. I will discuss how we can use machine learning tools to approximate these cosmological simulations and accelerate inference computations that would otherwise be prohibitively slow.



  • JYi-Kuan Chiang, Ohio State University
  • Nick Kern