| Name: | Swati Gavas |
| Affiliation: | Indian Institute of Science Education and Research Mohali |
| Conference ID : | ASI2024_264 |
| Title : | Dispersion in the Hubble-Lemaitre constant measurements from gravitational clustering |
| Authors : | Swati Gavas 1, J S Bagla 1, and Nishinkanta Khandai 2,3 |
| Authors Affiliation: | 1 Indian Institute of Science Education and Research (Mohali), Sector 81, SAS Nagar, Punjab 140306, India
2 School of Physical Sciences, National Institute of Science Education and Research, Jatni 752050, India
3 Homi Bhabha National Institute, Training School Complex,Anushaktinagar, Mumbai 400094, India |
| Mode of Presentation: | Oral |
| Abstract Category : | Galaxies and Cosmology |
| Abstract : | Measurements of the Hubble-Lemaitre constant H0 require us to estimate and recession velocity of galaxies independently. Gravitational clustering that leads to formation of galaxies and the large scale structure leaves its imprints in the form of peculiar velocities of galaxies. In general it is not possible to disentangle the peculiar velocity component from recession velocities of galaxies and this introduces an uncertainty in the determination of H0. We use cosmological N-body simulations to quantify the impact of peculiar velocities on the estimation of H0. We consider observers to be located in dark matter halos and target galaxies to be distributed amongst dark matter halos. We compute the distribution of the estimated value of H0 across all such observers in the simulation and we study the distribution as a function of distance from the observer. We find that the dispersion of this distribution is large at small scales and it diminishes as we go to large separations, reaching the level of the quoted statistical error in Planck and SH0ES measurements at approximately 100~Mpc. Measurements at smaller scales are susceptible to errors arising from peculiar motions, and this error can propagate to measurements at larger scales in the distance ladder. Notably, we observe a weak negative correlation between the local over-density around an observer and the deviation of the local and the global value of H0. We show that deviations more significant than 5% of the global values can be encountered frequently at scales of up to 40~Mpc, and this is larger than the statistical errors on local estimates. |
