Delineating cosmic expansion history with recent supernova data: A
  Bayesian model-independent approach
  Marginal likelihoods for the cosmic expansion rates are evaluated using the
recent `Constitution' data of 397 supernovas, thereby updating the results in
some previous works. Even when beginning with a very strong prior probability
that favors an accelerated expansion, we end up with a marginal likelihood for
the deceleration parameter $q_0$ peaked around zero in the spatially flat case.
This is in agreement with some other analysis of the Constitution data. It is
also found that the new data significantly constrains the cosmic expansion
rates, when compared to the previous analysis. Here again we adopt the
model-independent approach in which the scale factor is expanded into a Taylor
series in time about the present epoch; for practical purposes, it is truncated
to polynomials of various orders, in different trials. Though one cannot regard
the polynomials thus obtained as models, in this paper we evaluate the total
likelihoods (Bayesian evidences) for them to find the order of the polynomial
having the largest likelihood. Analysis using the Constitution data shows that
the largest likelihood occurs for the fourth order polynomial and is of value
$\approx 0.77 \times 10^{-102}$. It is argued that this value, which we call
the likelihood for the model-independent approach, may be used to calibrate the
performance of realistic models.
