Type Ia supernova counts at high z: signatures of cosmological models and progenitors

摘要

Determination of the rates at which supernovae of Type Ia (SNe Ia) occur inthe early Universe can give signatures of the time spent by the binaryprogenitor systems to reach explosion and of the geometry of the Universe.Observations made within the Supernova Cosmology Project are already providingthe first numbers. Here it is shown that, for any assumed SNe Ia progenitor,SNe Ia counts up to $m_{R}simeq 23-26$ are useful tests of the SNe Iaprogenitor systems and cosmological tracers of a possible non-zero value of thecosmological constant, $Lambda$. The SNe Ia counts at high redshifts comparedifferently with those at lower redshifts depending on the cosmological model.Flat $Omega_{Lambda}$--dominated universes would show a more significantincrease of the SNe Ia counts at $z sim 1$ than a flat, $Omega_{M} = 1$universe. Here we consider three sorts of universes: a flat universe with$H_{0} = 65 km s^{-1} Mpc^{-1}$, $Omega_{M} = 1.0$, $Omega_{Lambda} = 0.0$;an open universe with $H_{0} = 65 km s^{-1} Mpc^{-1}$, $Omega_{M} = 0.3$,$Omega_{Lambda} = 0.0$; and a flat, $Lambda$--dominated universe with $H_{0}= 65 km s^{-1} Mpc^{-1}$, $Omega_{M} = 0.3$, $Omega_{Lambda} = 0.7$). On theother hand, the SNe Ia counts from one class of binary progenitors (doubledegenerate systems) should not increase steeply in the $z= 0$ to $z= 1$ range,contrary to what should be seen for other binary progenitors. A measurement ofthe SNe Ia counts up to $z sim 1$ is within reach of ongoing SNe Ia searchesat high redshifts.