State of the Universe

Weak lensing to Doppler boosting to cross-correlations: novel probes of the high-redshift Universe

by Dr. Abhishek Maniyar (New York University)

Tuesday, September 6, 2022 from to (Asia/Kolkata)
at A304 and Zoom: Meeting ID: 825 1295 6967 Passcode: 384194
In recent years, cosmic microwave background (CMB) weak lensing, cosmic infrared background (CIB), and line intensity mapping (LIM) have emerged as a powerful tool to probe fundamental physics and galaxy evolution. 1. In the first part of the talk, I will present a brief introduction to the quadratic estimators for the weak lensing. Then I will show that a linear combination of lensing maps from the cosmic microwave background (CMB) and from line intensity maps (LIMs) allows to exactly null the low-redshift contribution to CMB lensing, and extract only the contribution from the Universe from/beyond reionization. This would provide a unique probe of the Dark Ages, complementary with 21 cm. I will quantify the interloper bias (which is a key hurdle to LIM techniques) to LIM lensing for the first time, and derive a "LIM-pair" estimator which nulls it exactly. 2. Then I will present a new observable: Doppler boosted CIB emission (DB-CIB). It is analogous to the kinematic Sunyaev-Zeldovich effect (kSZ) but has its origins in an emitted signal rather than a scattered signal like kSZ. This subtle difference allows us to use DB-CIB as a probe of the peculiar velocity field without the infamous ‘ optical depth degeneracy’ problem. I will show some results for prospects of observing the DB-CIB and its potential applications.3. Finally, I will briefly present an idea I am working on which utilises the kSZ effect to extract ‘only’ the patchy component of the reionisation i.e. the high redshift contribution using the so called projected-field estimators.