Astronomy seminar: "Detecting IGM structures in the very early Universe: Status, challenges, and new approaches"

Wed, 02/13/2019 - 14:00 - 15:00
Nithya Thyagarajan (NRAO)

Direct detection of evolving neutral Hydrogen structures from the Cosmic Dawn and Reionization Epochs (EoR) will reveal the nature of the first stars and galaxies as well as complete our understanding of a significant evolutionary phase of the Universe. In contrast with some recent exciting results from the EDGES experiment, detection of IGM structures using redshifted 21 cm by many experiments such as the MWA, LOFAR, and PAPER that commenced in the last decade has remained elusive. This is primarily due to the challenges in isolating the bright emission from foreground objects and instrument systematics from contaminating the cosmic signal. I will specifically describe results from my work that focuses on identifying, characterizing and providing design and analysis solutions to these various challenges. The Hydrogen Epoch of reionization Array (HERA) is a new instrument that aims to tackle these challenges and place meaningful cosmological and astrophysical constraints by studying the redshifted 21 cm signal from these cosmic epochs. One of the primary limitations in analysis arises from the challenge of very high precision calibration. I will introduce a novel and a complementary approach using bi-spectrum phase that bypasses the stringent calibration requirements and could potentially improve the prospects of detecting structures during cosmic reionization. I will discuss pathways to estimating the HI brightness temperature fluctuations and its evolution with redshift in this approach.

David Rittenhouse Laboratory, A2