Galileo's Pendulum

From detailed modeling and what we see of modern galaxies, we expect the earliest galaxies to be small and have intense star formation. A new survey using data from the Spitzer space telescope and the Subaru telescope in Hawaii has found a lot of surprisingly massive galaxies at the edge of our ability to observe, and those galaxies are aggressively making new stars. In my new Daily Beast column, I discuss that survey and what it might mean for our understanding of galaxy formation.

The new research discovered something different. The authors found a substantial number of very massive galaxies—more than 10 times the mass of the Milky Way—at a much earlier time than expected. (I have to say that the image accompanying that press release is among the more … embarrassingly dorky examples I’ve seen.) Not only that, these galaxies were busily making new stars, with bigger galaxies giving birth faster than those with lower mass.

That’s consistent with what astronomers have seen for closer galaxies. But early galaxies—at least very high-mass ones—should drop off in star formation at some point. That expectation depends on galaxies merging from smaller chunks, and depleting some of their available star-making fuel. [read more…]