Astronomy and Astrophysics – Astrophysics – Cosmology and Extragalactic Astrophysics
Scientific paper
2012-03-28
Astronomy and Astrophysics
Astrophysics
Cosmology and Extragalactic Astrophysics
5 pages, 4 figures; submitted to MNRAS
Scientific paper
We report the first results of a long term program aiming to provide accurate independent estimates of the Hubble constant (H0) and the Dark Energy equation of state parameter (w) using the L(Hbeta)-velocity dispersion (sigma) distance estimator for Giant HII regions and HII galaxies. We have used VLT and Subaru high dispersion spectroscopic observations of a local sample of HII galaxies, identified in the SDSS DR7 catalogue in order to re-define and improve the L(Hbeta) - sigma distance indicator and to determine the Hubble constant. To this end we used as local calibration or 'anchor' of this correlation, giant HII regions in nearby galaxies which have accurate distance measurements determined via primary indicators. Using our best sample of 89 nearby HII galaxies and 23 Giant HII regions in 9 galaxies we obtain H0 = 73.9+- 2.7 (statistical)+- 2.9 (systematic) km s-1 Mpc-1, in excellent agreement with, and independently confirming, the most recent SNe Ia based results.
Basilakos Spyros
Bresolin Fabio
Chavez Ricardo
Melnick Jorge
Plionis Manolis
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