NGSNCOSMO - Next Generation Supernova Cosmology

Cosmology is at the threshold of a new era.

The standard, Lambda-CDM, model, till recently, has been an excellent explanation of observations in the early and late universe.

The recent tension between the local Hubble constant (H0) and the inference from early universe, is a strong challenge to Lambda-CDM, with profound consequences for particle physics and cosmology.

While this tension can be a sign of novel physics, e.g., a contribution from massive neutrinos or a modified theory of gravity, it can also be a realization of unknown systematic effects. It is, therefore, urgent to explore such measurements from more than one method.

This project will tackle the open question "is there new physics beyond Lambda-CDM?" with cutting edge transient surveys in three steps: 1) Developing strongly lensed supernovae as an exciting new probe of H0, independent of either the early universe or the local distance scale. 2) sidestepping known systematics in local H0, by constructing a unique distance ladder from Type Ia supernovae (SNe Ia) observed by a single survey, the Zwicky Transient Facility (ZTF) 3) pioneering an empirical test of the directional dependence of H0 using the SN Ia magnitude-redshift relation.

The Vera Rubin Observatory (VRO), online imminently, is expected to discover hundreds of lensed SNe.

Utilizing state-of-the-art spectrographs, e.g., NOT and 4MOST, we will build a sample of lensed SNe from the VRO and measure H0 with 1.3% accuracy.

Implementing modern methods for distances to the ZTF SN Ia host galaxies from tip of the red giant branch (TRGB) stars, we will overcome the current largest distance scale error sources, i.e. host galaxy bias and calibration.

Forthcoming spectroscopy surveys will allow precise inference of ZTF SN Ia host galaxy redshifts, shedding light on potential anisotropies in the Hubble constant.

These interconnected channels for measuring the Hubble constant and its directional dependence will enable a precise and accurate test of Lambda-CDM.