Cornering the Hubble tension by studying systematics and reconstructing the local Universe with supernovae (HOSTFLOWS)

Lluis Galbany
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The expansion rate of the Universe parameterized by the Hubble-Lemaître parameter H(z), has been a major endeavor in cosmology since the discovery of the expanding Universe. In the last years, significant effort has been put forth to measure with high precision the local value of the Hubble-Lemaître parameter known as the Hubble constant (H0), and today H0 is estimated from the distance ladder with an uncertainty of <3% . Perplexingly, these findings have revealed a dramatic discrepancy dubbed "the Hubble tension": the estimation of H0 from the local distance ladder is in strong disagreement (at 4.4σ or 99.99% level) with the value inferred at high-redshift from the angular scale of fluctuations in the cosmic microwave background (CMB), possibly hinting towards new physics beyond the standard model. This discrepancy represents the most urgent puzzle of modern cosmology, and it is nowadays one of its hottest topics. The HOSTFLOWS project aims to advance towards solving of this tension by (i) performing an unprecedented study of the local environments of nearby standard candles to address the leading systematic uncertainties in the measurement of H0, and (ii) reconstructing the panorama of our supercluster Laniakea by studying cosmic flows using type Ia supernovae (SNe Ia) in the near-infrared (NIR). In this talk, I will introduce the topic and summarize the current and future efforts HOTFLOWS is doing in this regard.