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19–23 Dec 2024
Swatantrata Bhavan, Banaras Hindu University, Varanasi
Asia/Kolkata timezone

Anisotropy in Pantheon+ supernovae

Not scheduled
20m
Swatantrata Bhavan, Banaras Hindu University, Varanasi

Swatantrata Bhavan, Banaras Hindu University, Varanasi

Department of Physics, I.Sc., Banaras Hindu University, 221005 Varanasi, India
Oral Astroparticle physics and cosmology

Speaker

Animesh Sah

Description

We employ Maximum Likelihood Estimators to examine the Pantheon+ cata-
logue of Type Ia supernovae for large scale anisotropies in the expansion rate of
the Universe. The analyses are carried out in the heliocentric frame, the CMB
frame, as well as the Local Group frame. In all frames, the Hubble expansion rate
in the redshift range 0.023 < z < 0.15 is found to have a statistically signifi-
cant dipolar variation exceeding 1.5 km s^−1 Mpc^−1, i.e. bigger than the claimed
1% uncertainty in the SH0ES measurement of the Hubble parameter H0. The
deceleration parameter too has a redshift-dependent dipolar modulation at > 5σ
significance, consistent with previous findings using the SDSSII/SNLS3 Joint
Lightcurve Analysis catalogue. The inferred cosmic acceleration cannot there-
fore be due to a Cosmological Constant, but is probably an apparent (general
relativistic) effect due to the anomalous bulk flow in our local Universe.

Author

Co-authors

Christos Tsagas (Aristotle University of Thessaloniki) Mohamed Rameez (Tata Institute of Fundamental Research) Prof. Subir Sarkar, Oxford (University of Oxford)

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