The Top 12 of 2012
9. The Masses of Stars at Birth May Depend on Environment
Why it is important: When stars are born, there appear to always be many more low-mass stars than massive stars. However, if this ratio or ‘Initial Mass Function‘ (IMF) varies, it can change the way more extreme systems like high-redshift galaxies evolve.
- Observations of early-type galaxies (circles; colors indicate the velocity dispersion, which increases with galaxy mass) show systematic differences in their stellar mass to light ratios (x-axis) compared to that expected for a standard Salpeter IMF (y-axis). Other comparison IMFs are shown as constant horizontal lines. Since the mass to light ratio decreases for more massive stars, an IMF with relatively fewer high-mass stars like Salpeter will have a higher mass-to-light ratio. No constant IMF fits all of these galaxies, and this trend is independent of the assumed fraction of Dark Matter in these galaxies. Read more about it in this astrobite! (Adapted from Figure 2 of Cappellari et al.)
Next: (#8) Gravitational Lenses as a Cosmic Bathroom Scale: Weighing the Dark Matter in Galaxy Clusters with Hubble
Previous: (#10) A Magic Ratio to Quench Star Formation? Stellar and Dark Matter Mass tell Galaxies When to Stop Forming stars
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