SNNEXT

Since the discovery of the accelerated expansion of the Universe in 1998 by two independent high-redshift supernova (SN) projects using the Hubble Space Telescope, supernova cosmology has become an essential probe in all wide-field survey collaborations until our days (e.g. SDSS, SNLS, PanSTARRS). The first 3σ initial estimate of the Dark Energy density parameter has been rapidly improved to the point of this being already constrained to 1%, so the focus is now on its equation of state parameter w=P/ρ; and its evolution with cosmic time w(a)= w0+wa(1-a), where a is the scale factor of the universe. The most recent publication of the full 5-year analysis of the Stage III experiment Dark Energy Survey (DES, 2013-2017) Supernova survey, which is the current state-of-the-art SN cosmology results, have reached the precision of this w below the 10% level enabling the possibility to study the evolution of dark energy in cosmic time for further studies. Previous state-of-the-art Hubble-Lemaitre diagram, Pantheon+, combined SNIa data of low and high redshift from 18 different sources, with the systematic uncertainties that this combination of photometric systems carry over, as shown in Brout et al (2022). Ongoing efforts are put into combining the 1650 SNIa from the 5YR DES at z>0.1 with the 2000 low-z (z<0.1) SNe Ia from the Zwicky Transient Facility (ZTF), reducing systematics to only two very-well understood systems.

As members of both DES and ZTF SN Ia cosmology working group, our SN-ICE research group have been in the first row of these developments playing a fundamental role. The future looks promising in this regard. The next generation (Stage IV) collaborations in SN cosmology are expected to constrain w0 down to 1% and wa down to 10%, firmly proving whether the evolution across cosmic time is real. For that, we have assured full membership in the leading collaborations of the next decade:

A) The La Silla Southern Supernova Survey (LS4), set to commence in April 2024, will scan the Southern sky for five years, obtaining observations of all nearby SNe with exceptional quality, paving the way for the next best measurement of the Hubble constant (H0) and the growth scale parameter (σ8);

B) The Vera Rubin Observatory Legacy Survey of Space and Time (LSST), scheduled to begin scanning the Southern sky in February 2025 with a newly built 8-meter aperture telescope, will provide observations of hundreds of thousands of supernovae of all types at intermediate redshifts (0.2<z<1.2) during the its ten years of operation; and 

C) the Nancy Grace Roman Space Telescope (ROMAN), slated for launch no later than May 2027, includes a Supernova Survey that will obtain observations of the furthest supernovae ever observed (z~2.5), whose light we see now but was emitted when the Universe was only 2,000 million years old.

By combining this wide range in lookback time, these three experiments will build the most powerful SN Hubble-Lemaître diagram ever constructed, both in the terms of the number of SN and the extended redshift range, yielding groundbreaking results in the field. In this project, we aim to advance towards contributing in building this next Hubble-Lemaître diagram by working on different directions within these three surveys.