3 research outputs found
Observational Constraints on the Nature of Dark Energy: First Cosmological Results from the ESSENCE Supernova Survey
We present constraints on the dark energy equation-of-state parameter,
w=P/(rho c^2), using 60 Type Ia supernovae (SNe Ia) from the ESSENCE supernova
survey. We derive a set of constraints on the nature of the dark energy
assuming a flat Universe. By including constraints on (Omega_M, w) from baryon
acoustic oscillations, we obtain a value for a static equation-of-state
parameter w=-1.05^{+0.13}_{-0.12} (stat; 1 sigma) +- 0.11 (sys) and
Omega_M=0.274^{+0.033}_{-0.020} (stat; 1 sigma) with a best-fit chi^2/DoF of
0.96. These results are consistent with those reported by the SuperNova Legacy
Survey in a similar program measuring supernova distances and redshifts. We
evaluate sources of systematic error that afflict supernova observations and
present Monte Carlo simulations that explore these effects. Currently, the
largest systematic currently with the potential to affect our measurements is
the treatment of extinction due to dust in the supernova host galaxies.
Combining our set of ESSENCE SNe Ia with the SuperNova Legacy Survey SNe Ia, we
obtain a joint constraint of w=-1.07^{+0.09}_{-0.09} (stat; 1 sigma) +- 0.12
(sys), Omega_M=0.267^{+0.028}_{-0.018} (stat; 1 sigma) with a best-fit
chi^2/DoF of 0.91. The current SN Ia data are fully consistent with a
cosmological constant.Comment: Submitted to ApJ. 82 pages. 9 figures. 10 tables. Companion paper to
Miknaitis et al (2007). Electronic tables and probability surfaces available
at http://www.ctio.noao.edu/essence/wresult