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What velocity dispersion tells us about galaxy evolution

4 Oct 2012, 22:55 UTC
What velocity dispersion tells us about galaxy evolution
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Astronomers at Yale investigate how the number of galaxies at fixed inferred velocity dispersion (a probe of the total gravitational potential) changes as a function of time. Their results support a picture where star-forming galaxies are somehow "quenched" and transition to the non-star-forming galaxy population, consistent with leading ideas of galaxy evolution.Categories: Daily paper summariesTags: galaxies, galaxy evolution(Click to read more...)

Title: Evolution of Quiescent and Star-Forming Galaxies Since z~1.5 as a Function of Their Velocity Dispersions
Authors: Rachel Bezanson, Pieter van Dokkum, and Marijn Franx
First Author’s Institution: Yale University
When astronomers go out and observe galaxies, they make measurements that don’t necessarily have much physical meaning on their own. Consider the most basic “observable” of any astronomical object: flux (usually reported in the oft-maligned magnitude system). Flux is related to the amount of energy being generated by a star (or an entire galaxy), but you can’t actually calculate the luminosity unless you also know how far away the star (or galaxy) is. Once you have luminosity, though, you can compare one object to another directly, and luminosity functions have been a valuable tool for understanding changes in galaxy populations for virtually as long as we’ve known about other ...

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