Charity Woodrum

We do know that cold gas reservoirs are the fuel for star formation.

Yeah, exactly.

So why do some of them have the cold gas reservoirs and some of them don't?

One of the things that I was able to measure was what's called the star formation history of the galaxy.

So think of that as on the y-axis, there would be the star formation rate.

So how many stars these galaxies are forming per year.

And on the x-axis, you have time.

And so their early star formation histories, when they were younger galaxies, those all looked quite similar.

However, in the last billion years, all of the galaxies that had the cold gas reservoirs in the last billion years of the galaxy's life, there was a bump in their star formation.

There was this significant amount of what we called secondary star formation episodes.

or rejuvenation.

Yeah, and people had seen rejuvenation before, but I don't know that anyone had seen cold gas reservoirs in massive quiescent galaxies and saw that they also had rejuvenation episodes.

Oh, it could?

Yeah.

Just like with the physical processes that can make a galaxy quench, there's physical processes that can make a galaxy rejuvenate as well.

Two galaxies collide and, you know, eventually form one galaxy together.

If two galaxies even interact with each other and do like a flyby, where they just fly by each other, that little interaction can cause bursts of star formation as well.

Yeah, just like seeing a friend and it, you know, lifts your mood.

My childhood best friends, they're the biggest reasons I was able to survive and make it to where I am today.

When I was laying on that couch, the people coming over and helping me had no reason to other than that they loved me.