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Intermediate Redshift Clusters Shed Light on Galaxy Evolution
1 Febrero 2013: Using high signal-to-noise optical spectroscopy from Gemini, and Hubble Space Telescope imaging of three intermediate redshift galaxy clusters, Gemini astronomers Inger Jørgensen and Kristin Chiboucas have shed new light on galaxy evolution. The team’s paper, accepted for publication in The Astronomical Journal, shows that the mass to light ratios of the galaxies indicate that low-mass galaxies have experienced more recent star formation than high-mass galaxies. Both the mass-to-light ratios and the Balmer lines (hydrogen lines) can be used to estimate the ages of the galaxies. However, the Balmer lines indicate that all of the galaxies are very old, leading to a contradiction between the two methods of age determination. Furthermore, the metal lines (or metallicity, an indication of the presence of elements heavier than hydrogen and helium which are formed in previous generations of stars) show that there are metallicity differences when comparing the clusters. This is in contradiction with …
