Séminaire/Seminar Galaxies |
| « Precision cosmology with HII galaxies and giant HII regions » |
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Roberto Terlevich |
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I will report results of our programme aimed at studying the properties of compact galaxies with on-going massive and dominant episodes of star formation (HII galaxies). We have used the L(Hß) - s distance estimator based on the correlation between the ionized gas velocity dispersions and Balmer emission line luminosities of HII galaxies and Giant HII regions to trace the expansion of the Universe up to z ~ 2.4. This approach provides independent constraints on H0, Om and the dark energy equation of state parameter w.
Using high-dispersion Visible-NIR spectroscopy of HII galaxies at redshifts between 0.6 and 2.33, obtained at the VLT using XShooter plus some high-z HII galaxies from the literature improves the constraints and highlights the need for high quality emission line profiles, fluxes and reddening corrections. These results are consistent with recent studies, although weaker due to the as yet small sample and perforce lower quality of the literature data of high-z HII galaxies. I will also discuss our simulations based on these first results that show that highly competitive constraints can be obtained using a sample of 500 to 1000 high redshift HII galaxies with high quality data that can be easily obtained with present facilities like KMOS at the VLT or MOSFIRE at KECK in about 10 to 20 clear nights. Regarding H0, we have recalibrated the anchor sample of Giant HII regions in nearby galaxies with distances determined with primary methods via Cepheids and/or RRLyrae . Our latest results that include the new data for the expanded anchor sample and the "maser" galaxy NGC4258 gives H0 = 69 Km s-1 Mpc-1 indicating a possible solution of the tension with the Planck results. |
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jeudi 31 mars 2016 - 11:30 Salle 281 Institut d'Astrophysique de Paris |
| Page web du séminaire / Seminar's webpage |