A Cosmological Wish List for the JWST - Sixty Symbols

it's a wishlist ready given the success this remarkable success of jwst and the fact it's already producing images that are just stunning the world and its science is only just beginning I thought as a theorist who knows nothing about astronomy I would try and give a from what a wish list of of what it I would like to try and understand us see from jwst that will help us cosmologists understand both the universe as it is now but also the early universe it's glasses sea light in the infrared we can't see infrared so why is that if useful because in the very early universe which it can probe back to light was emitted from hopefully the first galaxies that were forming and the first Stars within the first galaxies that light probably is in the visible part of the spectrum when it was emitted and in maybe the UV part of the spectrum but that's 13 billion years ago 13.4 13.5 billion years ago only a few hundred million years after the big bang since that time as it started on its Traverse through the cosmos the universe has been expanding and what happens is light that experiences an expansion gets stretched And So It Begins emitted in the visible light but by the time it's reached us some 13 billion years later it's been stretched into the infrared so no matter how good your Hubble Space Telescope was or any of your telescopes on Earth that can on that can see visible light it would not be able to see that light whereas jwst is specifically been made so that the light it picks up is infrared light in the very early Universe one of the things it's going to try and find that evidence for is the first galaxies that were forming it can see those Galaxies for me it can see because it's got spectrometers it can see the light and then it can break it up into its constituent parts and from that it can see what elements are in those galaxies early on so it's gaining information about those elements from 13 plus billion years ago but here's the key thing that I'm particularly interested in right not clearly if it conceived back that far and no one else can it can also see nearer and so it can see galaxies forming 13 billion years ago but it can see galaxies then as they were say 10 billion years ago 6 billion years ago 5 billion years ago and what you're beginning to get is as long as you're thinking about the same type of galaxies you're beginning to understand the evolution of those galaxies how does a Galaxy evolve through time my hope this is why it's a wish list is that the the way a Galaxy evolves on its large scales will depend on what the background universe is doing how it's expanding where we know the universe is dominated by one thing today dark energy but we don't know what that dark energy is we think it might be something that is a constant energy contribution throughout the Universe because the energy density energy per unit volume that's called a cosmological constant but it may not it may be something that has evolved over time and has become much more significant today my hope is that these two sort of paradigms one where the dark energy is evolving in time and one where it's effectively a constant in time will lead to subtle but measurable differences in how a Galaxy evolves and so what you would need to do is solve your numerical simulations in both of these situations one where it's evolving in time and one where it isn't when you do numerical simulations you're looking at lots and lots of potential galaxies evolving you hopefully will see some difference say for example in the clustering of galaxies how many there you form in a given region or you might see something different in the size of the galaxies because Dark Energy might prevent the galaxies from collapsing depending upon how strong it is in the early universe so if you might find galaxies are a bit bigger than you were expecting if the DACA energy is evolving in time and because jwst is able to probe so far back and hopefully see lots and lots of examples of very early galaxies we'll maybe get some decent statistics on say the size distribution and the clustering of them those will be parameters numbers which depend upon the nature of the Dark Energy so I can't give you a concrete prediction as to what you might find my guess would be with a cosmological constant that they are going to be sort of um maybe a bit bigger than without the cosmological custom simply because it its presence might be more significant early on okay so so I've got my galaxies I'm trying to understand the Dynamics of those then if I look at say the center of a galaxy one thing we know about the center of the Galaxy is every Galaxy that's been observed has a supermassive black hole in there Sagittarius A is the famous one in the Milky Way and that's got a mass of about a million times the mass of the Sun the question is what what's the seed what led into what became the center of the Galaxy which could then accrete enough matter to give you a billion solar masses one possibility is that the seed could have come from the very early universe in the very early Universe much earlier than this there are these objects that could be in principal form that are very massive cosmic strings that can be small Loops of string which can form and they can have masses which are quite easily big enough to accomplish this thing of the seed Mass I have to admit they're not the favorite way forward those people that work on this day in day out say no you don't need to be so exotic you can work with standard sort of astrophysics and pinch this tweak that a little bit and you can get it but here's the question right imagine jwst keeps seeing masses close to a million solar masses back at 13.4 billion years ago in other words those first galaxies that are forming are already have this supermassive black hole in the center and imagine if they keep seeing it then the question arises is there enough time for you know that seed must have been there using standard astrophysics or do I need some other more exotic particle physics origin which is where I would come in and yeah that's what I'm looking for so so the second thing on my wish list is that we can begin to probe the core of a galaxy and see how massive it is as we go further and further back and if so you eventually go far enough back that you have you just simply haven't had enough time to form that from conventional astrophysics that's my hope so the third thing that I think I would really like to understand is what happens to the supernovae as I go back in time so this type 1A supernovae which are the white dwarves that that create enough matter that they then can form a supernovae they use as standard candles and that's the way that we actually have been determining how the universe is accelerating one of the key ways but we can only probe it at the moment out to a certain distance scale a distant redshift it's of order one and when you look at the different models of dark energy and ask what does this Luminosity the brightness of these objects how does it look as a function of the redshift how far away all the models look fairly similar out to a redshift of of one or so but the models then begin to differ quite considerably once you go past the redshift of one because they they experience the matter dominated part of the universe differently one is the dark energy is a cosmodial constant it experiences the dark its contribution to the overall budget in a is a constant but the the ones with the um evolving equations of State they can actually they'll tail off compared to the cosmological constant so what you will see is a turnaround from the acceleration that we experienced today as we go back in redshift the universe stops accelerating we're going back in time remember the universe stops accelerating goes into what's called a matter dominated universe that's where the structures form that transition from the acceleration into the matter domination relies on the type of dark energy and I my hope my third part of the wish list is that the jwst will actually find enough supernovae going out through that regime to find lots and lots I think so that it will be able to definitively give us the profile of the luminosity and then we can fit it with our models so that's sort of like you'll be able to recalibrate those standard candles and continue using them as standing continue using them as standard candles all the way out to a much deeper distance and then that I think will provide us with a really good handle on whether or not the dark energy is evolving in time or whether or not it's a constant that would be a massive result there is a fourth thing if you which is kind of linked but it's a real wish wish list a wish squared there have been papers recently which suggest there's another type of standard candle that we could think about and these are quasars right quasars are supermassic black holes of going berserk and they can be found at really large red shoes I think there's a lot of controversy whether they really are standard candles but if there are if there is a way of representing them as standard candles then they that's another way of probing deep into the universe and jwst because it can see these massive supermassive black holes it'll be able to probe all the way out to these large large red shifts you know taking us back to 13 billion years number five could it tell us something about the nature of dark matter and the nature of some of the supermassive stars that might be present in the early Universe supermassive Stars yeah there could be really big stars that are present that could in principle have come been formed not from the sort of material we're used to but from the scale of fields arising from the very early Universe from inflation and there are stars that theorists like myself have worked on called buzz on Stars which are formed in the very early Universe Axion stars is another type you can make sure that there are the sort of size that you expect of stars and the question is could we see any evidence for that in the very early Universe which jwst might be picking up one of the things I've taken from your wish list is you really want to know how different the dark energy regime was back then yeah to what it's like now you want to compare the two yeah why would the dark energy regime be so different back in the early early days okay okay my own Prejudice is now coming in all right uh I admit um I work on an area I have done a lot of work on an area called um scaling Solutions okay what does that mean that means I have some field evolving and it evolves in such a way that it gets it it mimics whatever the background is doing and in the early Universe just a very brief reminder the early Universe sort of has a radiation dominated period where the energy density is dominated by radiation then it goes into a matter dominated area when the bulk of structures form and then it comes into the dark energy dominated regime where we're accelerating this scale of field type model has the property there it just mimics whatever is dominating at the time cosmological constant is a constant all the way back here in time this one remember I've I've had it so that it it matches a cosmodial constant today but earlier on it could have been bigger because it was tracking it's called tracking following the matter then following the radiation so this idea of being able to see the influence over time is coming from a a Prejudice of mine that I think if there are scalar fields in the early Universe they can have this property which is a really nice property it's called an attractor solution where it finds what's dominating and it goes I'll have a bit of that and it'll follow it and then it switches and it says I'll have a bit of that matter Dominator and it follows that and we we don't know if the universe did that or not and I'm hoping you've hit the come to the nucleus of it I'm hoping jwst can see some evidence of it that's what I would really like what there is it's a remarkably nondescript star I suspect it was chosen probably because it's fairly boring right it's not you know it's not so bright that it would sort of blind the telescope it's not so faint that they wouldn't actually be able to use it to focus the telescope with it's got no companions so you can get a nice sharp image of an individual style it's got a cool name

Channel: Sixty Symbols

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Id: OnMl_56qLoI

Length: 13min 27sec (807 seconds)

Published: Thu Oct 27 2022