Exploring the evidence for a large local void with supernovae Ia data

Understand

In this work we utilise the most recent publicly available type Ia supernova (SN Ia) compilations and implement a well formulated cosmological model based on Lema\^{i}tre-Tolman-Bondi metric in presence of cosmological constant $\Lambda$ ($\Lambda$LTB) to test for signatures of large local inhomogeneities at $z\leq0.15$.

• Local underdensities in this redshift range have been previously found based on luminosity density (LD) data and galaxy number counts.
• Our main constraints on the possible local void using the Pantheon SN Ia dataset are: redshift size of $z_{\rm size}=0.068^{+0.021}_{-0.030}$; density contrast of $\delta\Omega_0/\Omega_0=-10.5_{-7.4}^{+9.3}\%$ between 16th and 84th percentiles.
• Investigating the possibility to alleviate the $\sim9\%$ disagreement between measurements of present expansion rate $H_0$ coming from calibrated local SN Ia and high-$z$ cosmic microwave background data, we find large local void to be a very unlikely explanation alone, consistently with previous studies.