BAO cosmology in non-spatially flat background geometry with application to BOSS and eBOSS
arxiv(2024)
摘要
We study the impact of the assumption of a non-flat fiducial cosmology on the
measurement, analysis and interpretation of BAO distance variables, along and
across the line-of-sight. The assumption about cosmology enters in the choice
of the base template, as well as on the transformation of tracer's redshifts
into distances (the catalog cosmology): here we focus on the curvature
assumption, separately and jointly, on both.
We employ BOSS and eBOSS publicly available data and show that for the
statistical precision of this data set, distance measures and thus cosmological
inference are robust to assumptions about curvature both of the template and
the catalog. Thus the usual assumptions of flat fiducial cosmologies (but also
assumptions of non-flat cosmologies) do not produce any detectable systematic
effects. For forthcoming large-volume surveys, however, small but appreciable
residual systematic shifts can be generated which may require some care. These
are mostly driven by the choice of catalog cosmology if it is significantly
different from true cosmology. In particular, the catalog (and template)
cosmology should be chosen, possibly iteratively, in such a way that the
recovered BAO scaling variables are sufficiently close to unity. At this level
of precision, however, other previously overlooked effects become relevant,
such as a mismatch between the sound horizon as seen in the BAO and the actual
sound horizon in the early Universe. If unaccounted for, such effect may be
misinterpreted as cosmological and thus bias the curvature (and cosmology)
constraints.
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