Constraints on the Local Cosmic Void from the Pantheon Supernovae Data

Kavli Affiliate: Ke Wang

| First 5 Authors: Ke Wang, Kun-Peng Chen, Morgan Le Delliou, ,

| Summary:

In principle, the local cosmic void can be simply modeled by the spherically
symmetric Lemaitre-Tolman-Bondi (LTB) metric. In practice, the real local
cosmic void is probably not spherically symmetric. In this paper, to
reconstruct a more realistic profile of the local cosmic void, we divide it
into several segments. Each segment with certain solid angle is modeled by its
own LTB metric. Meanwhile, we divide the 1048 type Ia supernovae (SNIa) of the
Pantheon Survey into corresponding subsets according to their distribution in
the galactic coordinate system. Obviously, each SNIa subset can only be used to
reconstruct the profile of one segment. Finally, we can patch together an
irregular profile for the local cosmic void with the whole Pantheon sample.
Note that, the paucity of each data subset lead us to focus on the inner part
of each void segment and assume that the half radii of the void segments are
sufficient to constrain the whole segment. We find that, despite $2sigma$
signals of anisotropy limited to the depth of the void segments, the
constraints on every void segment are consistent with $Lambda$CDM model at
$95%$ CL. Moreover, our constraints are too weak to challenge the cosmic
homogeneity and isotropy.

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