Podcaster: Dr Jacinta Delhaize and Dr Daniel Cunnama ; Guest: Kelebogile Bonokwane

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Title: Cosmic Savannah – #31: Cosmic Beasts and Where to Find Them

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Jacinta has a new paper out and takes her turn in the hot seat to tell us all about it!

Along with her colleagues, she has been part of the discovery of two giant radio galaxies using South Africa’s powerful MeerKAT telescope.

These galaxies are amongst the largest single objects in the Universe and are thought to be quite rare. The fact that MeerKAT detected two of these monsters in a relatively small patch of the sky suggests that giant radio galaxies may actually be much more common than previously thought.

Bio: Dr Jacinta Delhaize and Dr Daniel Cunnama are astronomers based in Cape Town, South Africa. Jacinta is a Research Fellow at the University of Cape Town. She spends her time using huge radio telescopes to study gas and black holes in distant galaxies. Daniel is the Science Engagement Astronomer at the South African Astronomical Observatory. He likes to use large supercomputers to create simulations of galaxies. Both Jacinta and Daniel love to promote the incredible astronomy happening across the African continent.

Guest: Susan Murabana Owen and Chu Owen

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Dan: [00:00:00] Welcome to The Cosmic Savannah with Dr Daniel Cunnama

Jacinta: [00:00:08] and Dr. Jacinta Delhaize. Each episode we’ll be giving you a behind the scenes look at world-class astronomy and astrophysics happening under African skies.

Dan: [00:00:17] Let us introduce you to the people involved, the technology we use, the exciting work we do, and the fascinating discoveries we make.

Jacinta: [00:00:24] Sit back and relax as we take you on a safari through the skies.

Dan: [00:00:34] Welcome to episode 31. Happy New Year, everyone.

Jacinta: [00:00:38] Yeah, happy New Year!

Dan: [00:00:39] We are once again recording over zoom. We are socially distanced and confined pretty much to our homes. So apologies for any sound issues or slight delay or. Jacinta and I talking over each other.

Jacinta: [00:00:55] We’ve got a fancy new setup now where I’ve got a home recording USB microphone set up. Thanks mum! It was my Christmas present. And Dan has our usual recorder in his house.

Dan: [00:01:07] Well, if you’re listening to it, then it’s worked. Yeah. All right. So 2021 from an astronomical point of view…

Jacinta: [00:01:13] there’s a new rover landing on Mars this year, right?

Dan: [00:01:16] Yeah. The Perseverance Rover will be landing this year, which is always exciting. We spoke about it a little bit last year. That’s super cool. They’re a few months away, I think. The launch of the James Webb Space Telescope should finally be happening this year.

Jacinta: [00:01:30] Oh I can’t wait!

Dan: [00:01:32] I’m not holding my breath.

Yeah. It’s gone through numerous delays over the years, so we’ll see. That’ll be very, very exciting and very, very stressful launching something like this.

I’ll be watching that launch with bated breath. In terms of celestial events observable from Earth, there’s nothing major. There’s a small eclipse visible from Cape Town, the 4th of December.

Jacinta: [00:01:57] Luna or solar?

Dan: [00:01:59] Solar, a small solar eclipse. But it’s a very small percentage visible just from Cape Town, not the rest of South Africa and actually it’s centered over Antarctica, which is quite exciting. If you can manage to get there. I’m sure we’ll get a couple of good photos out of that one. So, yeah, I guess we should get going with today’s episode.

Jacinta: [00:02:18] Yes.

Dan: [00:02:19] And what do we have in store today?

Jacinta: [00:02:21] Who are we interviewing today?

Dan: [00:02:24] Well, it’s the moment you’ve all been waiting for and I’ve been waiting for for some time. Jacinta’s long awaited paper is finally out. And so we can talk about it. I guess there’s an embargo until today, until it comes out and you can tell us all about it. So Jacinta… welcome to The Cosmic Savannah!

Jacinta: [00:02:47] No, you’re meant to call me Dr. Delhaize. Remember? Cause I’m the guest.

Dan: [00:02:52] Well, wait, let me do it…The Esteemed Dr. Jacinta Delhaize, welcome to The Cosmic Savannah.

Jacinta: [00:03:00] Yes well, hi, nice to be here. I’m actually quite nervous. I guess this is what it feels like to be a guest on our show.

Dan: [00:03:07] Just relax. It’s a conversation. That’s what we tell our guests, right?

Jacinta: [00:03:11] Ok, chilling. Well, I guess, well, you have to ask the questions, don’t you?

Dan: [00:03:16] Yeah. I have to ask the questions this time.

Let’s get into it. Your paper, you have discovered well, you and your team have discovered two giant radio galaxies using the MeerKAT telescope. And these galaxies are amongst the largest single object in the universe  and obviously quite rare.

Before we get into the discovery and what exactly it all means, I think we should do a sort of introduction to radio astronomy. Talk a little bit about what it is and how it differs from optical astronomy. What exactly are we looking at and how are we doing it?

Jacinta: [00:03:52] Sure. Okay, so astronomy uses the whole electromagnetic spectrum, some telescopes can detect optical light, which is the same light as we can see with our eyes.

So they’re just basically huge eyes, but then we can also have different telescopes that can see ultraviolet light, infrared, the whole range of wavelengths down to the lowest frequencies or the longest wavelengths, which are the radio. And radio telescopes kind of look like big satellite dishes. There are several around the world and a new one in South Africa is called MeerKAT.

That’s in the Karoo and it comprises of 64 individual dishes and combined together it’s called an interferometer, which is pretty much one of the best in the world, if not the best at what it does. This is a pretty new telescope. It was launched… What? June 2018?

Dan: [00:04:47] That’s correct.

Jacinta: [00:04:47] And since is starting to make some pretty cool discoveries, including this one that we’ve made.

Dan: [00:04:55] Yeah. So we’re basically looking at radio waves which are coming in. As you said, MeerKAT’s a 64 dish array. And the reason we do an array is because in order to detect these very long wavelengths, we’d ideally like to have a huge square kilometer big dish. But that’s kind of unfeasible. So instead we build these arrays and then combine the signals to simulate a much bigger telescope.

That’s interferometry.

Jacinta: [00:05:26] Well, that’s getting towards the SKA which MeerKAT is the precursor of, but yes, that’s what we’re heading towards.

Dan: [00:05:32] I don’t know what the combined collecting area of MeerKAT is, but it’s pretty big. 64 dishes which are each kind of 13 meters big.  You’ve spoken a little bit about MeerKAT launched in 2018.

What makes MeerKAT so special? Why is it so powerful and what are the technological advancements which we’ve seen from MeerKAT?

Jacinta: [00:05:52] The one thing about MeerKAT in particular is that it’s very, very sensitive, so it can pick up very, very faint light or light from very large distances. And this is because what we call the receivers, the part that received the light, the radio waves, these are cryogenically cooled and they perform even better than they were designed for. So this thing is really, really sensitive.

The other really good thing about MeerKAT is that because there are so many of these individual dishes, 64 of them, we can spread them out. Some close together, some really far apart. And the greater the number of different distances between telescopes the more completely you can see the sky.

So if you have telescopes that are closer together, if you have dishes that are closer together, you’re going to be able to see things on the sky that are much larger scale. And if you have telescopes that are further apart, you’re going to be able to see things on a smaller scale. And so because we have this whole range, we can see small features in the emission from the galaxies or from whatever we’re looking at. And we can see large features.

And the way this has helped to make the discovery that we’ve published today is that this makes the MeerKAT telescope really sensitive to what we call “diffuse emission”. This is kind of like large scale fuzzy stuff. That’s very, very faint and distributed over large patch of sky.

Dan: [00:07:17] Okay. So you mentioned your discovery. Let’s get into it. You’ve discovered two giant radio galaxies. Firstly, what is a radio galaxy and how does it sort of differ from a regular galaxy?

Jacinta: [00:07:29] Okay. So galaxies, as we know are big collections of stars and gas and dust and dark matter and such, and you might have what we call a normal galaxy or star forming galaxy, which is just chilling out and it’s forming stars and converting its gas into stars. And those stars go supernova and then etc.

But some galaxies are called active galactic nuclei. Most galaxies have a supermassive black hole in their center, and this black hole becomes active when you have stuff falling into the black hole. So whether that be gas or dust coming from the galaxy or coming from the intergalactic medium, which is the stuff between galaxies.

So this is trickling in into the black hole and it’s heating up a lot as it does so. Then we call this black hole active. We call this whole galaxy an AGN, an active galactic nucleus. This activity is emitting a huge amount of very high energy light. It can be emitted across the entire electromagnetic spectrum all the way from the gamma rays down to the radio.

And when you have a lot of radio emission coming from this region, it’s called a radio galaxy. And often this is in the form of two kind of beams coming usually above and below the plane of the galaxy itself. And we call these jets. There are relativistic particles. These are highly charged particles like electrons, which are traveling close to the speed of light and they are interacting with the magnetic field around the black hole.

These are spiraling in the magnetic field and emitting what we call synchrotron radiation, which is predominantly admitted in the radio. Right? So we have these huge beams of radio emission coming from above and below the black hole in these huge jets. And this is what a radio galaxy is.

Dan: [00:09:20] We really got you excited there didn’t we? Okay. It’s a lot to take in. So essentially a radio galaxy’s got the supermassive black hole at the center, which when it’s feeding, essentially taking in gas sometimes excites that gas and pushes out large jets of high energy particles, which we can detect in the radio wavelengths.

Jacinta: [00:09:48] Exactly.

Dan: [00:09:49] Okay. Got it. So what is a giant radio galaxy then?

Jacinta: [00:09:55] These jets of light, of which we will put a picture on the website for this episode. These huge radio jets, we think that they grow. So they start out small and then as the galaxy ages, they get bigger and bigger and bigger and bigger pushing further and further outwards from the galaxy.

They can come in a whole range of sizes. And the giant radio galaxies these are ones that are bigger than 700 kiloparsecs, which is around 22 times the size of our own galaxy, the Milky Way. So these are really truly enormous systems and these particular ones, we call giant radio galaxies.

They’re actually fairly rare. We’ve found hundreds of thousands, even millions of radio galaxies of all different sizes, but only about 800 or so of them are classified as giants. So relatively rare.

Dan: [00:10:44] Are they giant in mass or just giant in size?

Jacinta: [00:10:47] Giant in size. So we measured the size as the distance between the end of one radio jet and the end of the other. So the full extent.

Dan: [00:10:54] So they don’t necessarily have more stars in them. They’re just kind of more diffuse things.

Jacinta: [00:10:59] Yeah, exactly. So their end to end size is really enormous. The galaxy at the center, it can vary in what it looks like, but often it will be hosted by a galaxy that is what we call a red and dead elliptical.

So it’s an elliptical galaxy, which has very little gas in it and therefore it’s not forming many stars. So the stars that are inside it are kind of turning red because stars turn red as they age and without new stars forming that are blue, this whole galaxy looks red.

Dan: [00:11:26] Is that why these sort of large galaxies haven’t been detected before? I mean, is it because their stars aren’t quite so bright and they’re more diffuse?

Jacinta: [00:11:35] No. So what we call the “host” galaxy, the galaxy that is hosting the black hole and emitting the radio jets. That’s actually fairly bright. I mean, we can see it very clearly in the optical images, but what hasn’t been detected before is the radio emission.

The particular galaxies that we have found with MeerKAT, they have been found before in the radio wavelengths. So actually that was part of the work that I did in my previous postdoctoral research position in Croatia where we studied the same patch of sky with a telescope in New Mexico called the Very Large Array. And the benefit of the Very Large Array is that it has very, very good angular resolution.

That means that it can see details very, very clearly and very, very small details. And in that data, you can see these galaxies, you can see the radio jets, but only the inner parts of them, the very, very inner parts. So in that data, these look like radio galaxies, but not giants, just kind of small ones. So we’d found  them before  and we’d found their elliptical host galaxies, but they just looked small. What we found in the new data is that not only do they have these little inner jets, they’ve got these huge, enormous outer jets, many, many, many times bigger than the previous ones that were found. And so that’s how we now know that these are giant radio galaxies.

And it’s because of the excellent MeerKAT sensitivity to diffuse emission, which I said at the start, the ability to detect large scale, very faint emission or light on the sky. That’s why we can now pick up the giant lobes of this galaxy. Whereas we couldn’t see it in other data from telescopes like the Very Large Array or from the Giant Meter-wave Radio Telescope in India, which has also looked at this particular patch of sky called COSMOS.

Dan: [00:13:25] All right so you haven’t discovered new galaxies. You’ve just discovered a larger radio emission, a more diffuse radio emission than has been discovered before from these galaxies. And they’re not necessarily giant galaxies, although they are big, but they’re giant in the radio.

Jacinta: [00:13:42] Well, it depends what you mean by galaxy.

What do you mean by a giant galaxy? Classically that’s considered to be the size of the part of the galaxy that contains all the stars. But all of these radio jets, this plasma, this is also part of the galaxy.

Dan: [00:13:57] Ah touche.

Jacinta: [00:13:58] But we haven’t really considered that to be the size of galaxies before, because we couldn’t actually see it.

Dan: [00:14:03] Ah but then, I mean, you know, there could be this diffuse emission around all galaxies, but it’s just not getting lit up.

Jacinta: [00:14:10] Well, we’re looking with MeerKAT now, and we’re not finding that except for in a few examples such as these.

Dan: [00:14:16] Yeah. Then that leads me onto my next question. What does this mean for galaxy formation and evolution or our understanding of it?

Jacinta: [00:14:24] Okay. So, yeah, that’s a good question. There’s actually something else special about these galaxies and not only are they giants that hadn’t been identified as giants before, they’re also particularly special giants. We had a look at how these compare to other giant radio galaxies in size and what we call “luminosity” or “power”. By luminosity or power we mean kind of how bright the radio waves are, how much emission is coming from them. And they’re actually really quite faint. So we’ve found galaxies that are much larger and a bit fainter than most other giant radio galaxies that have been found. This means that they are quite unique objects and it probably means that there’s a lot more of them out there. There might be this extra population of giant radio galaxies out there that we haven’t seen before, simply because our telescopes couldn’t pick up this diffuse light, which MeerKAT can now see. This would actually match what we have predicted from models of how these radio galaxies evolve over time.

As I’ve said, we think that these radio jets, they start off small, so contained quite close to the stars, but then they grow outwards over time. If this is really why some galaxies become giants, then this would mean that we should see quite a lot more giant radio galaxies than we are actually seeing.

So it looks like they are there. We just hadn’t seen them before because of the limitations of our telescopes. And this is all information we need in order to understand how galaxies evolve or change over time, over cosmic time, since they were formed after the Big Bang till now. We need to understand all of these different physical processes that are going into them to understand the whole picture of galaxy formation and evolution.

Dan: [00:16:16] Yeah and you mentioned that, you know that there could be other giant radio galaxies like this, and we should be detecting them. These galaxies you detected, and you’re part of a survey called MIGHTEE, and presumably the MIGHTEE survey is going to carry on and is expected to detect many more of these. Can you just explain a little bit about MIGHTEE? What does it stand for firstly, and then what is its goal? What can we expect coming out from the survey in the next few years?

Jacinta: [00:16:46] MIGHTEE, that’s an acronym which I’ve just had to look up because I can never remember it.

It stands for the MeerKAT International Gigahertz Tiered Extragalactic Exploration survey. So mightee: M I G H T E E. And this is a galaxy evolution survey planned with MeerKAT and underway. So initially when MeerKAT was being planned  there were several large survey projects planned. So international astronomers got together and formed collaborations and decided what most of the time on MeerKAT was going to be spent doing. And they sent in proposals. And the plan for MIGHTEE was one of them.

This was to create a really large scale galaxy evolution survey. Now, what does that mean? It means that MeerKAT is looking at several large patches of sky. In total it’ll be about 20 square degrees. Now to give you an idea, the area of the full moon is about half a square degree. Fairly large patches of sky.

And their goal here is to pick up the radio light from many hundreds of thousands of galaxies. And in doing that, you can study for example, the hydrogen gas, the neutral gas within these galaxies, which is the raw fuel of star formation, which we have spoken about a few times previously on The Cosmic Savannah.

And you can also study what I mentioned earlier, the synchrotron emission. So that’s this special lightgenerated by these electrons moving really fast in the magnetic fields. Sort of weird other things like polarization, where the direction of the light, the angle of the light is changing, but we don’t need to go into all of those details.

There’s a lot of different components of this MIGHTEE survey, but it started off with Early Science observations or Pilot observations. So this is just to check whether everything’s going right. These are the first set of observations to see if the survey has been well-planned. So to do that, MIGHTEE looked at one patch of sky one square degrees in size. So about four full moons can fit into that region.

And we looked at a particular patch of sky called COSMOS, as I mentioned earlier, and this patch of sky has been looked at by many other different telescopes in the past, in the radio light, in the x-rays in ultraviolet, in the infrared. And so we have a lot of data to compare with.

That’s important because all of this extra types of data that can let us figure out how far away these galaxies are. And once we’ve done that, we can have a look at how much light we’re detecting from them. And we can figure out what the actual strength of the light is because of course if you’ve got a galaxy that is close to you, but a bit faint, it’s going to look the same brightness as a galaxy that is further away from you and quite bright.

One of the things that we found straightaway when we looked at this early science data and of the COSMOS field was we spotted these two huge extended objects. Which turned out to be these giant radio galaxies that I have published a paper on. And they really looked fantastic. We’ll post a picture on the website of a cutout from the radio map of the sky that MIGHTEE made. And you can see really clearly these big streaks, these fuzzy streaks across the sky. And those are these giant radio galaxies that we found. Now, this was really exciting because if there are only, let’s say about 800 giant radio galaxies known, and a lot of these have been found with the LOFAR telescope, which stands for the Low Frequency Array, which is sort of based in the Netherlands and Europe. With that telescope most of  these giant radio galaxies were found, and we looked at how they were distributed across the sky. And based on that, we really didn’t suspect to find even one giant radio galaxy in this tiny one square degree patch of sky that we looked at. The fact that we found two is incredible. The probability of finding two, based on what we know about the distribution on the sky of giant radio galaxies, is very, very, very small. Incredibly small.

So either we have been insanely lucky to find these, or there are many more giant radio galaxies than we previously knew. And so that’s how we came up with this very exciting conclusion that there may be many more than we knew before. And that we’re starting to find them now with surveys like MIGHTEE, that are able to detect this very faint diffuse emission because of how sensitive they are.

Dan: [00:21:10] That’s super cool. And how much of the sky is MIGHTEE going to look at and how long is it going to take and how many of these things can we expect?

Jacinta: [00:21:21] So it’s going to look at in total 20 square degrees. So for comparison, what I’m talking about was one square degrees. These early observations, which four full moons will fit into it.

So you times that by 20 that’s how big ultimately the field will be. It’ll take several hours. So the observations that we looked at of the COSMOS field, actually they took only about less than 24 hours. So it’s actually incredible how sensitive this MeerKAT telescope is because the same patch of sky with the Very Large Array we had to look at for 400 hours with the Very Large Array before we could get to the same level of sensitivity.

So it’s going to take quite a few more hours to finish the whole survey. But the thing is we have to share the telescope. So not all of the observations can be dedicated just to MIGHTEE. We have to share with other surveys.

Dan: [00:22:12] You’re not going to get 20 days straight up.

Jacinta: [00:22:14] No.

Dan: [00:22:15] It’s probably just as well otherwise you’d have a lot of work.

Jacinta: [00:22:19] Yeah. Right. Of course, this is definitely not just me doing it. This is an international team of several dozens of astronomers. This is led by Matt Jarvis at the University of Oxford and Russ Taylor at the University of Cape Town. And then there are many other people who work very, very hard on this, including Ian Heywood, who is the second author on my paper and many others.

So yeah, not just me.

Dan: [00:22:44] MeerKAT is a precursor to the Square Kilometer Array which we mentioned earlier, and that’s going to be coming in the next five or 10 years. Recently the SKA was ratified. There’s many, many partner countries involved, and I think the final signatures happened in December.

So it’s, it’s official now that the SKA is an international organization. There’s a treaty and construction can now start on the SKA. That’s obviously going to be even more sensitive than MeerKAT. What are you looking forward to from SKA in terms of this kind of research in this field?

Jacinta: [00:23:27] Yeah, that’s a good question.

So the SKA is just so incredibly exciting. Of course, it’s going to be built partly in South Africa and partly in Western Australia. Each of those two components of the SKA will detect slightly different frequencies of the radio light. And it’s going to be, I think, revolutionary for our understanding of galaxy evolution, our understanding of radio galaxies, and radio astronomy because it will combine the best qualities of all the different telescopes in the world.

So the best qualities of the Very Large Array, the VLA, the best qualities of MeerKAT and ASKAP in Australia. MeerKAT, as I’ve said, is very good at detecting diffuse emission. So it’s very good at detecting large scale things.

And it’s very, very sensitive. It has good angular resolution, meaning it can see smaller details, but not as good as the VLA. So the VLA has really good angular resolution. The SKA will have both will have everything, right? So it’s going to be very, very sensitive, even more sensitive than MeerKAT by many times.

And it’s going to have really amazing angular resolution. So can see very, very small details. If you can see details that are very, very small and very, very faint, you can see things that are very far away and everything in between there. And of course, as you’re looking further and further away, you’re looking back in time because of the amount of time it takes for light to travel to the Earth.

So we’re going to have this amazing new crisp view of the Universe as seen in the radio light. And I can’t wait to see what will happen. And hopefully not only will MeerKAT detect many more of these giant radio galaxies. So hopefully we’re even going to find more in MIGHTEE in the other fields that haven’t been looked at yet.

But then with the SKA who knows what we’ll find? Maybe we’ll find extra giant radio galaxies, or I dunno, what would we call them? Uh, humongous giant radio galaxy, or something like that.

Dan: [00:25:22] We’ve got a few years to try and come up with a good name.

Jacinta: [00:25:24] Yeah. I clearly, I’m not very good at naming, so we’ll have to do a workshop on that.

Dan: [00:25:31] Okay. Well, Dr. Delhaize, thank you very much for joining us on The Cosmic Savannah.

Jacinta: [00:25:37] It was a pleasure to be here, Dan. Thanks. It’s so weird!

Dan: [00:25:42] Congratulations on your paper. Well done for getting it out. That’s quite an achievement. It’s super exciting.

Jacinta: [00:25:48] Thank you. It’s been a long haul.

Dan: [00:25:51] Maybe we can just explain to the listeners, I mean, what does it mean to get a paper?

It’s not like an article in the newspaper, right?

Jacinta: [00:25:57] No. Yeah. And why it takes so long as well.

So a scientific publication or a paper is the goal of your work as an academic. It’s to make a discovery or a finding and then publish it. So tell other people. And the whole process can take several years. It can be very quick if you are very, very, very lucky and very efficient, but usually it takes several years. The way that it works for me, because I’m an observational astronomer is I wait for the telescope to take the data and I wait for team members to process the data. Because it doesn’t come out of the telescope looking like a nice, pretty map. You have to do a lot of complicated things to turn it into an image of the sky. And then you kind of look at that data and you find something interesting and then you analyze it. So this is usually using a lot of coding and a lot of programming.

And doing the analysis. So applying knowledge of astrophysics. So this is where your knowledge of physics and maths comes in. You read a lot of other people’s papers. You can’t just read textbooks on the topic to understand the research the field that you’re in because the textbooks aren’t updated quickly enough to be cutting edge because papers are coming out every single day with newer and newer and newer research.

And you have to be really up to date on the very latest stuff in this research field that you’re working on. So you have to go and read all of these papers and understand what the cutting edge is. And then you have to start to write your paper. You write up your discoveries and what you found, you compare it to what other people have published in the literature before.

And then you finish writing this paper. So mine is about 15 pages, but you can have shorter papers. You can have longer papers. That’s  about an average size, I’d say about 15 pages with very, very small font and double columns and figures and pictures in it and everything. And then you submit it to a journal. And a journal is a…how would you describe a journal, Dan? I’ve never really been sure how to describe them.

Dan: [00:28:01] It’s a publication, you know. It’s like a newspaper, except it’s a formal publication, which comes out generally once a month from an organization which collects and processes these papers. So they keep a record of all of the papers, which get published.

Jacinta: [00:28:21] And it used to actually be published in an actual journal, an actual magazine sort of thing, which was sent out to all of the institutes.

But now of course, most of it’s just online because we all got access to the internet. We can just download all of the papers. We can save paper, save some trees in the process. You can choose which journal. There are several that you’d want to submit to. Usually you try and submit to a journal that has a what we call a high impact factor, so it’s got a really good reputation.

You submit it to this journal. I submitted it to the Monthly Notices of the Royal Astronomical Society. And then they do this important process called a peer review. They send your paper to somebody else who is an expert in the same field, but who was not an author on your paper.

And they have to read through it and they have to make suggestions and say, okay, yes, this paper looks like it’s scientifically rigorous. This is really well done. All of the analysis is correct. Or they make suggestions for changes. They say, oh look, you’ve actually forgotten to factor in this. Or then they might make some small changes, they might suggest some big changes. And then you get it back and you have a chance to change things. And then you can submit it back to the journal and then it might go through that process again, or it might be accepted.

My paper was accepted in, I think it was December of 2020. And then you have to do some things like you have to make sure it’s all type set to the nice format of the journal and you wait for that to happen.

And then finally it gets published. And often you also put it on the public archive, which is where everybody can access it because some of these journals are closed access. So you actually have to have a subscription to access them. But we obviously want everybody in the world to be able to access science and what we publish. So that’s why we also publish a version of it in the public access area. And that’s the process from start to finish.

Dan: [00:30:09] Thank you.  I should point out that that practice of publishing things on what’s called the arXiv, which is a freely available archive of all of the papers, is kind of unique to astronomy.

Jacinta: [00:30:22] Is it?

Dan: [00:30:23] Yeah. Most other sciences and especially medical research and things are behind a paywall. So you can’t access these journals without paying. And that slows the whole process down quite a lot, actually. Whereas in astronomy, often people post on the arXiv things which have been submitted, but actually haven’t been peer reviewed yet. Just to give people an indication of what’s going on and what’s coming. 

Particularly if you’re experienced and confident in your work. Are you’re confident it’s going to get published without many changes. You stick it on the arXiv and people can read it that day. You can publish it one day and it’s out there the next. So it’s a really good way for astronomy to move forward quickly and for these discoveries to be shared.

Jacinta: [00:31:08] Yeah, we don’t have to wait for months and months for the journals to publish it.

Dan: [00:31:13] You don’t actually I have to wait for these articles to be formally published. You can read them almost instantly.

And then the last step of the publishing process, which you didn’t mention is once it’s out there, then you start again.

Jacinta: [00:31:27] Well, yeah, I’m avoiding that part.

Dan: [00:31:30] So take a deep breath and do it all again.

Jacinta: [00:31:36] That’s right. I mean, I guess I could mention if you want the next step.

Dan: [00:31:40] What’s coming next? You must have one in the pipeline.

Jacinta: [00:31:43] My bosses are listening to this. So yes, I’ve been working very hard. Yeah. So I guess you usually have several projects kind of going on at the same time that you’re working on. But I’ve got several ideas of where to go from here with regards to these giant radio galaxies. I’ve put in a proposal to observe them again with MeerKAT, but at a different frequency, at a lower frequency.

And this is going to give us information about the actual age of the electrons in different parts of the jets. So what we think is that we’re going to find that they’re very young towards the center and very old towards the outside. But we are actually trying to find out whether these galaxies are restarted, meaning that the black hole kind of switched off for a while and stopped forming jets.

The old jets kind of kept expanding outwards and then suddenly it switched on again so that you’ve got these new little inner jets and this would indicate restarted activity. Which means that the supply of gas or whatever is falling into black hole, stopped for a while, and then started again, this is going to give us a lot more clues about what’s going on.

So I’m waiting to hear whether or not my observing proposal was successful. So I submitted this application to MeerKAT. Then there’s  a time allocation committee who are going to assess it. Lots of people are applying for time, so it’s very competitive. So I may not get this time,  this round, but there’ll be another opportunity later to try again.

This is one idea, but another thing I can do is go and look through the rest of the MIGHTEE data. Some of it has been taken in other areas of the sky as I mentioned, it’ll be 20 square degrees in full. And so some of that data already exists. So I can go and check that out. Go galaxy hunting, and see if I can spot some more giant radio galaxies.

Dan: [00:33:23] Awesome.

Jacinta: [00:33:24] And they should be there, right? If we’re right that there are two of these in each square degree of the sky, we should be able to find, I mean, there should be 40 in the entire MIGHTEE region. So fingers crossed we find some.

Dan: [00:33:36] I bet you there aren’t. And then you’re going to have to rethink the whole thing again.

Jacinta: [00:33:40] No, Dan don’t say that! But actually that could be more interesting to be like, what on Earth is going on in this particular part of the sky?

Dan: [00:33:49] Yeah. That’s the fun. You never really know what you’re going to get.

Jacinta: [00:33:52] Yeah, exactly. And so that’s a risk, right? You might start a project and it could go nowhere because you don’t know what the answer is.

That’s the point of science is that you’re doing something that no one else has done before, but it could also be a really cool discovery. 

Dan: [00:34:05] Great so I think that’s it for today.

Jacinta: [00:34:08] Yeah. So thank you for having me as a guest. It was a weird experience. You could hear how nervous I was.

Dan: [00:34:16] That was great. I mean, we’ve been wanting to talk about your research for a while and you’ve kind of been holding it close to your chest because there is something about that.

This research and endeavor, you don’t want to get scooped either. You don’t want somebody else to see your idea before you’ve published it and then publish it themselves. Because that does happen too. So you do kind of hold these things a little bit close to your chest. Mostly it’s a kind of nice environment, but it’s rare.

Jacinta: [00:34:44] Mostly people are really nice and cool about that, but it can happen.

But, anyway, I wanted to time this with the release of the official publication of the article, of the paper, and also the press release. I wrote a little press release and I’ve sent it out to various places. And so if anyone wants to contact me to talk about it, you can.

Dan: [00:35:01] Yeah. Let’s, let’s hope it gets picked up.  You know, it’s a pretty cool discovery and well done.

Jacinta: [00:35:07] Thank you.

Dan: [00:35:08] And thank you very much for listening. We hope you’ll join us again for the next episode of The Cosmic Savannah.

Jacinta: [00:35:13] You can visit our website,, where we’ll have the transcript, links to other stuff related to today’s episode.

And you can follow us on Twitter, Facebook, and Instagram @cosmicsavannah that’s Savannah spelled S a v a n n a h.

Dan: [00:35:29] Special thanks today to Dr.  Jacinta Delhaize for speaking with us.

Jacinta: [00:35:34] Thanks to our social media manager Sumari Hattingh, and all The Cosmic Savannah volunteers. Also to Mark Allnut for music production, Janas Brink and Michal Lyzcek for photography and Lana Ceraj for graphic design.

Dan: [00:35:47] We gratefully acknowledged support from the South African National Research Foundation, the South African Astronomical Observatory and the University of Cape Town Astronomy Department to help keep the podcast running.

Jacinta: [00:35:57] You can subscribe on Apple podcasts, Spotify, or wherever you get your podcasts. And if you’d like to help us out, please do rate and review us and recommended us to a friend.

We’d really appreciate it.

Dan: [00:36:07] And we’ll speak to you next time on The Cosmic Savannah.

Jacinta: [00:36:19] This is really good practice for me. It’s hilarious how, like, ah, I’m nervous and I’m stumbling and it’ll be good for like radio interviews to practice this stuff.

End of podcast:

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