New astrobites article

The vagaries of scheduling have given me another astrobites article not too long after the last (I get a break now until August, editing aside).

This time I chose to write about a recent Nature paper, about the discovery of a distant disc galaxy through gravitational lensing (I've called this one Definitive Discovery of a Dead Distant Disc since, in the absence of a clever reference or pun, alliteration always works). Back in March, I'd written another article in which I set out in broad brush-strokes how gravitational lensing works and why its useful. But when it comes to lensing, it takes two to tango: you need a huge amount of mass, perhaps provided by a foreground galaxy, to focus the light of a background galaxy. This means that lensing really has two main uses - you might be interested in the distribution of mass in the foreground galaxy, or else in the magnified background galaxy that you wouldn't otherwise be able to see so clearly. In my March article I focused mostly on the former use, something I know a little about through working with Dr Russell Smith (my PhD supervisor), who has put the technique to good use weighing nearby massive galaxies. This time I was keen to redress that imbalance. The paper I chose to write about discusses observations of a distant disc galaxy, one which appears to have finished forming stars remarkably early in the universe's life. Typically, the violent processes that can end star formation abruptly also reshape the galaxy, whereas a quiescent disc galaxy would normally have burned out slowly. If the result holds up then it therefore presents something of a puzzle!

Here's how it looks before correcting for the distorting effect of the lens (in this case a massive galaxy cluster) - this is a cropped version of a figure from the paper, which is linked to in my article: