Testing the isotropy of cosmic acceleration with the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>Pantheon</mml:mi><mml:mo>+</mml:mo></mml:mrow></mml:math> and SH0ES datasets: A cosmographic analysis
Carlos A. P. Bengaly, J. S. Alcaniz, C. Pigozzo
Abstract
We use a recent $\mathrm{Pantheon}+\mathrm{SH}0\mathrm{ES}$ compilation of type Ia supernova distance measurements at low-redshift, i.e., $0.01\ensuremath{\le}z\ensuremath{\le}0.10$, in order to investigate the directional dependency of the deceleration parameter (${q}_{0}$) in different patches (60\ifmmode^\circ\else\textdegree\fi{} size) across the sky, as a probe of the statistical isotropy of the Universe. We adopt a cosmographic approach to compute the cosmological distances, fixing ${H}_{0}$ and ${M}_{B}$ to reference values provided by the collaboration. By looking at 500 different patches randomly taken across the sky, we find a maximum $\ensuremath{\sim}3\ensuremath{\sigma}$ CL anisotropy level for ${q}_{0}$, whose direction points orthogonally to the cosmic microwave background (CMB) dipole axis, i.e., $(R{A}^{\mathrm{SN}},DE{C}^{\mathrm{SN}})=(267\ifmmode^\circ\else\textdegree\fi{},6\ifmmode^\circ\else\textdegree\fi{})$ vs $(R{A}^{\mathrm{CMB}},DE{C}^{\mathrm{CMB}})=(167\ifmmode^\circ\else\textdegree\fi{},\ensuremath{-}7\ifmmode^\circ\else\textdegree\fi{})$. We assessed the statistical significance of those results, finding that such a signal is expected due to the limitations of the observational sample. These results support that there is no significant evidence for a departure from the cosmic isotropy assumption, one of the pillars of the standard cosmological model.