Звездообразование в галактиках. Интервью с итальянским астрономом

[Music] Astronomy. The first question: Your work has been published in a very important magazine. It's well, usually it places really important works. So could you explain why is it so important? Because, as I understand, you observed the situation when star formation was driven not by winds from a black hole in the center of the galaxy, but with the merger, and a huge number of interstellar gas was ejected from the galaxy. The galaxy is going...

[Music] Thanks for the question. So there are two reasons, I would say, why this discovery is important. Maybe three. So the first reason is that, as you are saying, we are observing a galaxy in which star formation is going to be shut down soon because a large quantity of gas has been expelled outside of the galaxy. This means that the galaxy will not have material for forming new stars in the future.

This is important because this is the first time that this process has been observed in a massive galaxy. Theorists and observers have been asking for a long time what causes the massive galaxies, like the one we observed, to stop forming stars. So, by observing this phenomenon, we are saying that one of the ways in which massive galaxies can stop forming stars is by ejecting gas from galaxies. It was previously theorized, but now we are observing it. It's indirectly...

Yes, the other two reasons why this is important are that we were able to study the statistics of these events, trying to understand if they are enough to produce the number of dead galaxies in the universe. Our studies suggest that these events are rare, yes, but are also frequent enough that they can explain the formation of passive galaxies. And when I say passive, I mean galaxies that are not forming stars.

Could I interrupt you for a moment? When you speak about the statistics, how can you estimate the statistics using just one example of the galaxy? That's another very good question. And the reason why we can estimate statistics is because this is a single event that has been observed from a larger data set. We took the ALMA telescope and we observed more than 100 galaxies at the same cosmic epoch, but we observed this event, this ejection, only in one of those objects.

So this fact that we observed just one ejection over a hundred objects allowed us to understand how frequent these events are. And the third reason... So the third reason, you're promising? Yes, yes, yes. So the third reason is that the signature through which we discovered this event is actually extremely similar to the signature of other phenomena, which I think you also mentioned. Are those winds from AGN?

So what we are showing here is that these two phenomena can be very, very similar: winds and these ejections from mergers. So this perhaps is telling us that maybe in other cases these phenomena were confused in the past. This is normal, and this is how science goes. That sometimes we proceed by different trials and errors.

Yeah, yeah, perfect explanation. Thank you, Catalyst. Now the next question: The galaxy is rather far distant, yes, and the scale is very small. The Hubble image has about one arcsecond; it's very tiny. How is it possible to estimate the star formation rate and the structure of star formation within the galaxy with such a small scale of resolution?

So for the star formation measure rate, we just need integrated measurements. We don't need resolved measurements. You definitely cannot calculate individual stars at this distance, of course. No, absolutely not. This is only possible for the closest galaxies. This galaxy is so far away that we cannot resolve individual stars.

So we can compute the global star formation rate of the object in several ways. In specific studies, we took observations in the far infrared from the Herschel satellite, and we can convert the measurements of the falling through luminosity into star formation rate. How exactly this estimate is... I mean, you say that you can transform your measurements into infrared to star formation rate, and as a result, you got a huge deformation rate of about 500 stellar masses per...