Colloquium Abstract - Mahesh - 2026May08

May 8, 2026

11:00am Mountain

Nivedita Mahesh (Caltech)

 

Chasing the 21-cm signal: From MRO to OVRO to the Lunar farside

 

Abstract

Standard cosmological models predict that the first astrophysical sources formed in a Universe filled with neutral hydrogen (HI) about 100 million years after the Big Bang. The transition into Cosmic Dawn (CD) that seeded all the structures we see today can only be robustly probed directly by the 21-cm line of HI. Redshifted by the Hubble expansion, HI emission and absorption during CD is expected to be visible at radio frequencies between 40 and 100 MHz, tracing redshifts of z ~ 13–35. Precisely characterized and carefully calibrated low-frequency instruments are necessary to measure the predicted ~10–200 mK brightness temperature of this redshifted 21-cm signal against bright galactic foregrounds.
In this talk, I will discuss two experiments designed to probe Cosmic Dawn: EDGES and OVRO-LWA. I will touch on the efforts of the EDGES team since the reported detection in Bowman et al. (2018), focusing on new analysis techniques and updates to the EDGES-3 system. For the OVRO–Long Wavelength Array, I will present the details of the upgraded telescope and discuss the development of MANAS, a new global 21-cm experiment at OVRO designed to address the systematic challenges that have defined the field. Finally, I will look beyond Earth to the lunar farside, the ultimate radio-quiet environment, and discuss FARSIDE as a future pathway to accessing the Dark Ages 21-cm signal, free from terrestrial RFI and ionospheric distortion.


Local Host: Kathryn Plant

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