Speaker 1: Welcome to Bedtime Astronomy. Explore the wonders of the cosmos
Speaker 1: with our soothing Bedtime Astronomy podcast. Each episode offers a
Speaker 1: gentle journey through the stars, planets, and beyond, perfect for
Speaker 1: unwinding after a long day. Let's travel through the mysteries
Speaker 1: of the universe as you drift off into a peaceful
Speaker 1: slumber under the night sky.
Speaker 2: Imagine opening like a photo album of the universe when
Speaker 2: it was just a toddler.
Speaker 3: Oh, that's a great way to picture it, right, Like.
Speaker 2: You would intuitively expect to see just complete chaos, absolutely,
Speaker 2: just random, messy infant galaxies scattered completely haphazardly in the void,
Speaker 2: like oblivious to one another, just trying to ignite their
Speaker 2: first stars.
Speaker 3: Yeah, just doing their own thing in isolation exactly.
Speaker 2: But recently astronomers developed the optical precision to actually look
Speaker 2: back twelve point six billion years into that exact epoch.
Speaker 3: And they definitely didn't find chaos, No.
Speaker 2: They didn't. They found these sprawling, highly structured, interconnected metropolis incredible.
Speaker 2: And these structures were already dictating exactly how fast those
Speaker 2: infant galaxies would grow, how they would physically shape themselves,
Speaker 2: and like ultimately how they would die. Yeah, we're essentially
Speaker 2: looking at the exact moment the cosmos began playing the
Speaker 2: nurture card, but on a galactic scale.
Speaker 3: Right, And that's huge because the prevailing assumption in cosmology
Speaker 3: for a very long time was that in the early universe,
Speaker 3: specifically that era around one point two billion years after
Speaker 3: the Big Bang, galaxies evolved almost entirely through secular processes.
Speaker 2: Which means what just internal stuff.
Speaker 3: Exactly, meaning their growth was driven by their own internal mass,
Speaker 3: their own gas reservoirs, and just their isolated gravitational dynamics.
Speaker 2: So totally the nature side of the equation, right, You're.
Speaker 3: Born with a certain amount of gas and you just
Speaker 3: build stars until you run out, got it. So finding
Speaker 3: these highlight evolved dense environments acting as like architectural constraints
Speaker 3: so early on, it completely upends our timeline of how
Speaker 3: structures formed because we've.
Speaker 2: Always known that in our current era, you know, the
Speaker 2: mature universe, galaxies are absolutely dominated by their environments, oh
Speaker 2: without a doubt. Like you look at massive structures like
Speaker 2: the Coma cluster which has thousands of galaxies, and it's
Speaker 2: obvious that gravity has corralled them together into these huge
Speaker 2: metropolises of light and hot gas.
Speaker 3: Right. But the assumption was always that this clustering and
Speaker 3: you know, the environmental effects that come with it, took
Speaker 3: billions of years to mature.
Speaker 2: We assumed it took time for the cosmic web to
Speaker 2: tighten its grip.
Speaker 3: Exactly, and that timeline constraint was largely based on the
Speaker 3: sheer scale of the distances.
Speaker 2: Involved and cosmic expansion, right.
Speaker 3: Yeah, the mechanics of expansion, the expansion of space acts
Speaker 3: as this persistent counter force to gravitational collapse.
Speaker 2: It's like a tug of war.
Speaker 3: That is the perfect analogy to form a massive galaxy
Speaker 3: cluster has to win a tug of war against the
Speaker 3: hubble flow.
Speaker 2: The underlying expansion of space itself.
Speaker 3: Right, And on the absolute largest scales, the expansion always wins.
Speaker 3: Space is pulling apart faster than gravity can pull it together.
Speaker 3: But on localized scales, On localized scales, if a region
Speaker 3: has a high enough initial density, its gravitational self attraction
Speaker 3: can actually halt that local expansion. It fights back and wins, Yeah,
Speaker 3: and it causes the whole region to collapse inward. We
Speaker 3: actually call this critical threshold the turnaround radius.
Speaker 2: Okay, so to understand how these environments shaped early galaxies,
Speaker 2: we need to look at the seeds of these modern
Speaker 2: massive clusters, the protoclusters, right, the protoclusters, And if a
Speaker 2: protocluster is essentially a localized region that successfully overcame the
Speaker 2: hubble flow, it must have started with a pretty significant advantage.
Speaker 3: Oh. Absolutely, it had to be an overdensity that was
Speaker 3: baked into the universe from the very beginning, just.
Speaker 2: Like a heavier pocket of space.
Speaker 3: Basically, Yeah, those primordial over densities are the crucial starting
Speaker 3: point because right after the Big Bang, matter was distributed
Speaker 3: with almost perfect uniformity, almost perfect almost, but there are
Speaker 3: these quantum fluctuations in that incredibly dense early state, and
Speaker 3: during cosmic inflation, those microscopic variations were stretched out to
Speaker 3: macroscopic scales.
Speaker 2: Leaving behind these slight variations in density.
Speaker 3: Right and over the first few hundred million years, dark matter,
Speaker 3: which doesn't interact with light so it can collapse much
Speaker 3: earlier than regular gas, began to pool into these slightly
Speaker 3: denser regions.
Speaker 2: Forming like the invisible scaffolding of.
Speaker 3: The universe exactly the dark matter halos. Wow, and these
Speaker 3: dark matter halos serve as the deep gravitational wells that
Speaker 3: anchor literally everything else. As they grew, their gravity pulled
Speaker 3: in the primordial hydrogen and helium.
Speaker 2: Gas, and that gas compresses, cools, and ignites to form
Speaker 2: the first stars.
Speaker 3: And infant galaxies. Yes, so a protocluster is really just
Speaker 3: a vast, sprawling network of these early dark matter halos
Speaker 3: connected by filaments of.
Speaker 2: Gas, just slowly drawing together towards this inevitable massive gravitational collapse.
Speaker 3: Right, and within those dense collapsing regions we see the
Speaker 3: onset of this environmental effect.
Speaker 2: Because in modern galaxy clusters, we know that environment is
Speaker 2: incredibly hostile.
Speaker 3: That's brutal.
Speaker 2: Like if a galaxy falls into a modern cluster, it
Speaker 2: doesn't just join the group peacefully, right, it gets fundamentally altered.
Speaker 3: Yeah, it's violently changed. We see these isolated field galaxies
Speaker 3: as beautiful, gas rich star forming spirals like our Milky Way,
Speaker 3: exactly like the Milky Way, but the galaxies trapped inside
Speaker 3: massive clusters, they're often massive ellipticals, entirely devoid of cold gas.
Speaker 2: Completely incapable of forming new stars. Right.
Speaker 3: Astronomers call it the classic red and dead classification.
Speaker 2: Which sounds so bleak. But what actually causes a galaxy
Speaker 2: to become red and dead when it falls into a
Speaker 2: modern cluster.
Speaker 3: Well, the mechanics driving it are thermodynamically really complex, because
Speaker 3: space within a cluster is not a vacuum.
Speaker 2: It's not empty, not at all.
Speaker 3: The immense gravitational pull of the entire cluster accelerates all
Speaker 3: this infalling gas to tremendous velocities, and.
Speaker 2: As it collides.
Speaker 3: As it collides, it shock heats to millions of degrees.
Speaker 3: It forms what we call the intracluster medium, or the ICM.
Speaker 3: So it's a plasma, a superheated plasma. It's actually so
Speaker 3: hot it emits primarily an X rays.
Speaker 2: Okay, So when a beautiful gas rich spiral galaxy plunges
Speaker 2: into this modern cluster, it's not flying through empty space now,
Speaker 2: it's literally slamming into a wall of superheated plasma at
Speaker 2: thousands of kilometers per second.
Speaker 3: Yeah, and the fluid dynamics of that collision are just
Speaker 3: devastating for the galaxy. I can imagine it experiences extreme
Speaker 3: ram pressure. The static pressure of the hot ICM basically
Speaker 3: acts like a hurricane force headwind, and it physically strips
Speaker 3: the cold star forming gas right out of the galactic.
Speaker 2: Disk, just blows it away.
Speaker 3: Yeah, trailing it behind the galaxy like the tail of
Speaker 3: a comet. And without that cold gas reservoir, star formation
Speaker 3: ceases almost immediately.
Speaker 2: It's just shut off completely. Yeah.
Speaker 3: And furthermore, the galaxy undergoes this process we call strangulation
Speaker 3: or starvation.
Speaker 2: Oh, which also sounds terrible.
Speaker 3: It is the extended halo of hot gas that would
Speaker 3: normally cool down and feed future star formation is also
Speaker 3: stripped away.
Speaker 2: So it loses its current gas and its future supply.
Speaker 3: Exactly. The galaxy is left with only its existing stars,
Speaker 3: which just slowly age, turn red, and eventually die out.
Speaker 2: But see that brings up a massive physical contradiction when
Speaker 2: we talk about the early universe. It really does, because
Speaker 2: if this environmental effect relies on this incredibly dense, superheated
Speaker 2: plasma to act as a hurricane wind, how could that
Speaker 2: effect possibly exist only one point two billion years after
Speaker 2: the Big Bang?
Speaker 3: Right?
Speaker 2: I mean a protocluster by definition hasn't fully collapsed yet.
Speaker 3: Right Exactly, the dark matter halos are still merging.
Speaker 2: The gas hasn't had billions of years to shock heat
Speaker 2: to those extreme X ray temperatures.
Speaker 3: You've highlighted the exact theoretical tension that made this specific
Speaker 3: era so critical to observe.
Speaker 2: Because the plasma shouldn't be there yet.
Speaker 3: Right, the classical mechanisms we just talked about, the ram pressure, stripping,
Speaker 3: the shock heating, they require a mature.
Speaker 2: Settled cluster, a finished product.
Speaker 3: Yeah, a protocluster at that early etpoch what we call
Speaker 3: redshift four or five is basically a sprawling, unfinished construction site.
Speaker 2: The gas is just streaming in along filaments.
Speaker 3: It isn't a static, superheated bath yet. So if we
Speaker 3: observe environmental effects altering the physical structure of galaxies in
Speaker 3: a protocluster, which we did, which we did, it implies
Speaker 3: that the mechanisms of cosmic nurture operate through entirely different
Speaker 3: physics in the early universe compared to today, probably.
Speaker 2: More accretion driven, right like feeding, instead of stripping.
Speaker 3: Exactly, it forces us to ask whether the early environment
Speaker 3: acts as a weapon that strips a galaxy or as
Speaker 3: a hyper efficient feeding tube that alters how it grows.
Speaker 2: But investigating that requires observational data that is frankly, notoriously
Speaker 2: difficult to capture.
Speaker 3: Extremely difficult because we aren't.
Speaker 2: Just looking for one faint object. We are looking for
Speaker 2: a sprawling, diffuse web of faint objects spread across a
Speaker 2: massive volume.
Speaker 3: Of space, seen as they were twelve point six billion
Speaker 3: years ago.
Speaker 2: Yeah, you can't just point a standard telescope at a blank
Speaker 2: patch of sky and hope to recognize a protocluster.
Speaker 3: Now, the observation challenge is huge. It's twofold, really. First,
Speaker 3: the intrinsic faintness of objects at that distance means you
Speaker 3: need an enormous light collecting area, a massive mirror, a
Speaker 3: massive primary mirror. And second, protoclusters are not compact.
Speaker 2: Because the universe expanded, right.
Speaker 3: The universe has expanded so much since that light was emitted.
Speaker 3: A single protocluster from that epoch spans an enormous angular
Speaker 3: size on the night sky today.
Speaker 2: So if you use a telescope with high magnification but
Speaker 2: a tiny field of view.
Speaker 3: You might see one or two galaxies, but you completely
Speaker 3: miss the forest for the trees, You'd never recognize the
Speaker 3: underlying macro structure.
Speaker 2: Which is exactly why astronomers needed an instrument like the
Speaker 2: subru telescope in Hawaii, Yes, specifically utilizing its hyper suprimecam
Speaker 2: or HSC.
Speaker 3: That camera is incredible.
Speaker 2: It's an engineering marvel is designed specifically for wide field surveys.
Speaker 2: It lets researchers map vast swaths of the deep universe simultaneously.
Speaker 3: But even with a massive field of view, looking at
Speaker 3: visible light from that era is completely useless.
Speaker 2: Right, because of redshift. The ultraviolet and visible light emitted
Speaker 2: by those early stars has been physically stretched by the
Speaker 2: expansion of space over twelve point six billion years.
Speaker 3: Yeah, the cosmological redshift is the defining hurdle of high
Speaker 3: redshift astronomy. Space itself is expanding, and as a photon
Speaker 3: traverses that expanding space, its wavelength is physically stretched out.
Speaker 2: So a photon emitted in the ultraviolet by a hot
Speaker 2: young star in the early universe.
Speaker 3: Will arrive at Earth billions of year years later with
Speaker 3: its wavelength stretched all the way into the red or
Speaker 3: infrared part of the spectrum.
Speaker 2: Right, So, if we want to trace the skeletal structure
Speaker 2: of a protocluster, we can't look for just the broad
Speaker 2: spectrum of starlight.
Speaker 3: It's two faint and smeared out exactly.
Speaker 2: We need a specific, highly concentrated signal that survives that
Speaker 2: cosmic stretching, we need a tracer.
Speaker 3: And in cosmology, the ultimate tracer for early star formation
Speaker 3: is the Liman alpha emission line.
Speaker 2: Let's break that down, because the physics underlying Liman alpha
Speaker 2: emission is just so cool. It relies on the fundamental
Speaker 2: quantum mechanics of the hydrogen atom.
Speaker 3: Right, yes, and hydrogen, being the primordial building block of
Speaker 3: the cosmos, was overwhelmingly abundant back then. It was everywhere
Speaker 3: exactly so, when a young massive galaxy undergoes a starburst phase,
Speaker 3: it synthesizes populations of incredibly hot massive stars, the O
Speaker 3: and B type stars.
Speaker 2: And to be clear for everyone, these aren't stars like
Speaker 2: our son oh in it at all. These are stellar behemoths.
Speaker 2: They burn at furious temperatures, and they exhaust their nuclear
Speaker 2: fuel in a matter of millions of years rather than billions.
Speaker 3: Yeah, they live fast and die young. And because they
Speaker 3: burn so hot, the peak of their radiation sits deep
Speaker 3: in the extreme ultraviolet.
Speaker 2: They're essentially cosmic floodlights.
Speaker 3: That is exactly what. They are blasting, high energy, ionizing
Speaker 3: radiation into the surrounding.
Speaker 2: Gas, and that surrounding gas is thick with neutral hydrogen.
Speaker 3: Right, So, When a high energy, extreme ultraviolet photon from
Speaker 3: one of these massive stars collides with the neutral hydrogen atom.
Speaker 2: It transfers its energy to the atom's single electron.
Speaker 3: Yes, and in the quantum mechanical model of the atom,
Speaker 3: electrons occupy specific quantized energy levels. They can't just be anywhere, No,
Speaker 3: they have defined orbits. So the incoming photon provides enough
Speaker 3: energy to excite the electron from its ground state, the
Speaker 3: lowest energy level and equals one up to a higher
Speaker 3: energy orbital.
Speaker 2: But quantum systems inherently seek their lowest possible energy state, right, Yeah,
Speaker 2: the universe absolutely abhors an excited electron.
Speaker 3: Really does. It can't maintain that precarious higher orbit, so.
Speaker 2: It drops back down almost instantaneously.
Speaker 3: Right, But energy must be conserved. When the electron transitions
Speaker 3: from that first excited state and equals to back down
Speaker 3: to the ground state, it has to release the exact
Speaker 3: quantum of energy it originally absorbed.
Speaker 2: And that energy is released as a single photon exactly.
Speaker 3: And because the energy difference between those two specific orbitals
Speaker 3: in a hydrogen atom is an absolute, unchanging physical constant.
Speaker 2: The emitted photon always has the exact same.
Speaker 3: Wavelength one hundred and twenty one point six nanometers.
Speaker 2: Deep in the ultraviolet. Yes, so you have millions of
Speaker 2: these massive stars acting as engines pumping extreme UV radiation
Speaker 2: into the surrounding hydrogen clouds.
Speaker 3: And the hydrogen clouds respond by fluorescently glowing at this
Speaker 3: one highly specific wavelength.
Speaker 2: It basically turns the entire galaxy into a blazing cosmic
Speaker 2: neon sign.
Speaker 3: It's exactly how it acts, flashing open for business making stars.
Speaker 2: I love that that is otherwise incredibly difficult to observe.
Speaker 2: These galaxies are broadcasting this brilliant, unmistakable signal, tied directly
Speaker 2: to the furious birth of new stars.
Speaker 3: And galaxies identified by the specific signature are appropriately called
Speaker 3: Lyman alpha emitters because the submission line is intrinsically so
Speaker 3: bright it acts as a beacon.
Speaker 2: Let's just pinpoint intense star formation across immense distances, right.
Speaker 3: However, actually capturing that one hundred and twenty one point
Speaker 3: six nanometer photon from Earth requires incredibly precise interference filters.
Speaker 2: Because of the red shift we discussed earlier. The photon
Speaker 2: leaves the galaxy at one hundred and twenty one point
Speaker 2: six nanometers, but as it travels for twelve point six
Speaker 2: billion years through expanding space, that wavelength stretches.
Speaker 3: Yeah, But the beauty of it is we can calculate
Speaker 3: the exact red shift for the specific epoch we want to.
Speaker 2: Observe because MathWorks.
Speaker 3: MathWorks. The era of twelve point six billion years ago
Speaker 3: corresponds roughly to a redshift of z equals four point
Speaker 3: five to five. Okay, and we know mathematically exactly how
Speaker 3: much a one hundred and twenty one point six nanimeter
Speaker 3: wavelength will be stretched by a red shift of that magnitude.
Speaker 2: It pushes the wavelength entirely out of the ultraviolet right.
Speaker 3: Yes, through the visible blue and green, and lands it
Speaker 3: squarely in the longer red wavelengths of the optical spectrum.
Speaker 2: So astronomers design a custom piece of glass, a narrow
Speaker 2: band filter that physically blocks out the entire electromagnetic spectrum
Speaker 2: except for that one mathematically predicted stretched out wavelength.
Speaker 3: It's a bespoke filter.
Speaker 2: And they place us in front of the hypersuprime cam,
Speaker 2: and they just stare at a massive patch of the sky.
Speaker 3: Right. They aren't looking at stars in our galaxy or
Speaker 3: even normal galaxies in the background.
Speaker 2: They are basically wearing specialized thermal goggles that's.
Speaker 3: A great analogy, goggles that only let them see the
Speaker 3: specific glow of Liman alpha mitters from exactly twelve point
Speaker 3: six billion years ago.
Speaker 2: It's a technique of extraordinary precision.
Speaker 3: It really is. By utilizing these narrow band filters on
Speaker 3: wide field imagers, you essentially take a highly specific slice
Speaker 3: of the universe at one exact moment in cosmic time.
Speaker 2: You're just mapping the distribution of these glowing beacons.
Speaker 3: Yeah, and if the universe were truly unorganized at that stage,
Speaker 3: you would expect to see a relatively uniform, random scattering
Speaker 3: of Lineman alpha emitters across the field of view.
Speaker 2: Just dots randomly everywhere. Right, But that is the exact
Speaker 2: opposite of what the SUBRU data revealed, totally the opposite.
Speaker 2: When they mapped this specific epoch, they found an astonishing
Speaker 2: concentration of these emitters. They located a massive, highly structured protocluster.
Speaker 3: And they named it the Locktac protocluster.
Speaker 2: Which is such an amazing discovery.
Speaker 3: The identification of the Locktac protocluster is a landmark observation,
Speaker 3: mainly because of its profound morphological complexity.
Speaker 2: Right, because the researchers didn't just find a singular, dense
Speaker 2: knot of galaxies. The mapping revealed this expansive, multi component architecture.
Speaker 2: It was highly structured, and the name itself provides a
Speaker 2: perfect geological metaphor for the structure. It's named after Locktac
Speaker 2: Lake in northeastern.
Speaker 3: India, right in Manipur.
Speaker 2: Yeah, and that lake is famous for its fumnus.
Speaker 3: The floating islands.
Speaker 2: Exactly, these massive, circular, floating islands of organic matter and vegetation.
Speaker 2: Some of them are large enough to support entire localized
Speaker 2: ecosystems like people live on them.
Speaker 3: Wow.
Speaker 2: But they are all floating within and inextricably linked to
Speaker 2: this one singular aquatic system of the lake, and the.
Speaker 3: Mapping of the protocluster mirrors that topology perfectly.
Speaker 2: It really does. The narrow band data revealed four distinct,
Speaker 2: intensely dense subclusters.
Speaker 3: Four separate nodes of hyperactive star formation.
Speaker 2: And these nodes are physically separated by vast distances across
Speaker 2: the early cosmic web. Yet the kinematic data and the
Speaker 2: spatial distribution confirmed they are absolutely gravitationally bound.
Speaker 3: They are four massive islands floating within a shared unseen
Speaker 3: ocean of dark matter.
Speaker 2: It totally validates the bottom up model of hierarchical structure
Speaker 2: formation on a gro and scale. We are looking at
Speaker 2: the fundamental building blocks of a future supercluster before they
Speaker 2: have consolidated. Right.
Speaker 3: Ronaldo Leastrom, the lead author of this study from the
Speaker 3: National Astronomical Observatory of Japan, accurately describe these nodes as
Speaker 3: the construction sites of the most massive structures in the
Speaker 3: present day universe.
Speaker 2: Construction sites. It's so appropriate because it highlights the dynamic,
Speaker 2: unfinished nature of the whole system.
Speaker 3: Very unfinished. In the billions of years following this twelve
Speaker 3: point six billion year old snapshot, the profound mass of
Speaker 3: that shared dark matter halo would act as a massive
Speaker 3: gravitational funnel.
Speaker 2: So those four separate islands.
Speaker 3: They're locked in an inexorable inward spiral, destined to crash
Speaker 3: through the process of dynamical friction, where massive objects lose
Speaker 3: orbital energy as they move through a background of smaller
Speaker 3: particles and dark matter. Their orbits will decay to slow
Speaker 3: down and fall in Exactly, they will eventually fall toward
Speaker 3: the bury center of the system.
Speaker 2: And the eventual collisions between these four nodes would be
Speaker 2: unfathomably violent, truly cataclysmic as those individual subclusters merge. The
Speaker 2: dark matter halos intertwine, but the baryonic matter, the gas,
Speaker 2: and the galaxies slams together.
Speaker 3: Yeah, and those mergers would trigger massive shock waves through
Speaker 3: the newly forming intracluster medium.
Speaker 2: Which would incite even more starbursts before eventually heating the
Speaker 2: gas to the point where star formation is permanently quenched.
Speaker 3: Exactly what we discussed earlier. The Looctac protocluster is definitively
Speaker 3: destined to become one of the monolithic spherical X ray
Speaker 3: emitting superclusters we see in the local universe today.
Speaker 2: So finding this structure provided the perfect laboratory. It proved
Speaker 2: that complex multi noode environments existed extremely early in cosmic history.
Speaker 3: But just establishing the presence of the environment is only
Speaker 3: the prerequisite, right.
Speaker 2: Right, The main question was is this environment actually doing anything?
Speaker 3: Yes? The primary scientific objective was to determine if this,
Speaker 3: the sprawling, interconnected environment, was actively altering the evolutionary pathways
Speaker 3: of the individual galaxies residing within it.
Speaker 2: Like did living in one of these four dense islands
Speaker 2: actually change a galaxy's physical structure compared to a galaxy
Speaker 2: just growing up in complete isolation.
Speaker 3: And to answer that, the wide field survey capabilities of
Speaker 3: the Subaru telescope were no longer.
Speaker 2: Sufficient because Subru is designed to find the city.
Speaker 3: Right, to understand the architecture of the individual buildings within
Speaker 3: the city, you need unprecedented spatial resolution.
Speaker 2: You have to zoom in.
Speaker 3: You have to transition from wide field mapping to deep
Speaker 3: targeted observations.
Speaker 2: Which necessitates space based observatories exactly.
Speaker 3: The research team employed a multi wavelength approach, combining the
Speaker 3: high resolution visible light capabilities of the Hubble Space Telescope
Speaker 3: with the revolutionary infrared sensitivity of the James Web Space.
Speaker 2: Telescope GWST, doing what it does best, and the methodology
Speaker 2: here relies on using different wavelengths of light to isolate
Speaker 2: different physical components of the galaxies.
Speaker 3: Right, Yeah, They performed a massive comparative analysis. They analyzed
Speaker 3: the galaxies deeply embedded inside the dense nodes of the
Speaker 3: Locktac protocluster city dwellers, and they compare them directly to
Speaker 3: field galaxies, galaxies from the exact same red shift, the
Speaker 3: exact same twelve point six billion year old epoch, but
Speaker 3: located in low density, isolated regions of the cosmic.
Speaker 2: Web rural galaxies.
Speaker 3: Exactly. It is the ultimate controlled experiment for the nature
Speaker 3: versus nurture debate and astrophysics.
Speaker 2: Because by isolating the epoch you completely remove time as
Speaker 2: a variable. They're the exact same age, right.
Speaker 3: The only major variable altering their evolutionary state should be
Speaker 3: the local density of their environment.
Speaker 2: So they scrutinized the physical morphology of these two groups
Speaker 2: of galaxies across two distinct spectral regimes, right, the rest
Speaker 2: frame ultraviolet and the rest frame optical.
Speaker 3: Yes, let's break down the physical significance of those two
Speaker 3: spectral regimes.
Speaker 2: Let's do it.
Speaker 3: The rest frame ultraviolet light, which we observe today red
Speaker 3: shifted into the visible or near infrared, acts as a
Speaker 3: direct tracer for active, ongoing star formation.
Speaker 2: As we established with the Liman alpha mechanics, UV radiation
Speaker 2: is dominated by the most massive.
Speaker 3: Hottest stars, right the O and B types.
Speaker 2: And because those stars have lifetimes of only a few
Speaker 2: million years, any UV light we detect must be coming
Speaker 2: from stars that were born almost exactly the moment the
Speaker 2: light was emitted.
Speaker 3: Exactly. Ultraviolet emission provides an instantaneous pulse check of the galaxy.
Speaker 3: It delineates the exact regions where giant molecular clouds are
Speaker 3: actively collapsing to form new stellar populations right now.
Speaker 2: Okay, So when the researchers analyzed the spatial extent of
Speaker 2: the ultraviolet emission, basically measuring the physical size of the
Speaker 2: star forming cores, what did they find?
Speaker 3: They found a remarkable parody. They were the same, statistically indistinguishable,
Speaker 3: whether a galaxy was deeply embedded in the chaotic, dense
Speaker 3: environment of the Loctac protocluster or floating completely alone in
Speaker 3: the cosmic voids.
Speaker 2: The active nurseries looked identical.
Speaker 3: Yes, the physical size of their central star forming engines
Speaker 3: was the same. The environment did not appear to be
Speaker 3: altering the spatial distribution of current star formation in the core.
Speaker 2: So if the investigation had just concluded there, if they
Speaker 2: only had the ultraviolet data, you might actually conclude that
Speaker 2: the early environment had no structural impact at all.
Speaker 3: You would you might erroneously conclude that nature entirely dominated
Speaker 3: nurture in the early universe.
Speaker 2: But the rest frame optical data.
Speaker 3: Yes, captured meticulously by Jawst's near infrared camera. It revealed
Speaker 3: a drastically different reality.
Speaker 2: Because the optical light, which has been redshifted deep into
Speaker 2: the infrared where jawst excels, doesn't trace the massive, short
Speaker 2: lived hot stars.
Speaker 3: No. No, it traces the older, cooler, lower mass stars,
Speaker 3: the K and M type dwarfs and giants.
Speaker 2: The stars that live for billions of years.
Speaker 3: Right Therefore, they represent the accumulated history of the galaxy.
Speaker 3: The rest frame optical emission maps the stellar mass distribution
Speaker 3: that has already been assembled over the galaxy's entire lifetime
Speaker 3: up to that point.
Speaker 2: It provides the structural footprint of the established galaxy, independent
Speaker 2: of wherever the current transient bursts of new star formation
Speaker 2: happened to be a correct exact so I like to
Speaker 2: think about it like looking at modern cities. The UV
Speaker 2: light shows us the bustling downtown district where all the
Speaker 2: new frantic construction is happening right now.
Speaker 3: That's a perfect way to visualize it.
Speaker 2: But the optical light shows us the sprawling suburbs, the
Speaker 2: historical footprint of the city's growth over time. Yes, and
Speaker 2: when they compared the optical footprints the suburbs of the
Speaker 2: cluster galaxies to the isolated field galaxies.
Speaker 3: The parody vanished entirely.
Speaker 2: The divergence was profound.
Speaker 3: The data explicitly demonstrated that the galaxies residing within the
Speaker 3: dense nodes of the Locktac protocluster were on average one
Speaker 3: point four times larger in their rest frame optical emission
Speaker 3: than their isolated counterparts.
Speaker 2: A forty percent increase in physical size. That is a
Speaker 2: massive structural discrepancy, It really is. So the central downtowns
Speaker 2: are exactly the same size, but the established suburbs of
Speaker 2: the cluster galaxies have sprawled outward immensely.
Speaker 3: Proving definitively that the environment is actively manipulating the physical
Speaker 3: architecture of the galaxies, but it's doing so primarily on
Speaker 3: the outskirts right leaving the central star forming cores relatively untouched.
Speaker 2: This morphological disparity is really the crux of the discovery, isn't.
Speaker 3: It Absolutely because it indicates that the mechanisms of environmental
Speaker 3: influence in the early universe are fundamentally different from the
Speaker 3: gas stripping processes that dominate modern clusters.
Speaker 2: Right Because in a mature cluster, the environment strips the
Speaker 2: gas and shuts down star formation in the core, but.
Speaker 3: In this early protocluster, the environment is rapidly building up
Speaker 3: the extended stellar envelope, while the core just continues to
Speaker 3: function normally.
Speaker 2: Okay, So that requires us to analyze the actual mechanics
Speaker 2: of mass assembly in a dense environment, like if the
Speaker 2: central engine isn't working any harder than an isolated galaxy,
Speaker 2: how is the club uster galaxy building these massive outer
Speaker 2: suburbs so rapidly?
Speaker 3: It implies the mass isn't being generated internally.
Speaker 2: It's being accreted externally.
Speaker 3: Yes, and the theoretical frameworks for galaxy formation strongly support
Speaker 3: that conclusion. In a high density node like the Locktac protocluster,
Speaker 3: a massive central galaxy sits at the nexus of intersecting
Speaker 3: dark matter filaments.
Speaker 2: These filaments act as cosmic highways exactly.
Speaker 3: They channel continuous streams of cold primordial gas directly into
Speaker 3: the gravitational well of the galaxy.
Speaker 2: This phenomenon is known as cold stream accretion. Right.
Speaker 3: Yes, it provides a massive influx of raw material to
Speaker 3: the outer regions of the galaxy.
Speaker 2: So it's essentially being force fed by the cosmic web.
Speaker 3: Yes, but it's not just pristine gas flowing in the
Speaker 3: dense environment of a protocluster is crowded with smaller satellite
Speaker 3: dor galaxies, right, so.
Speaker 2: The frequency of minor mergers in a protocluster environment must
Speaker 2: be exponentially higher than in isolated regions.
Speaker 3: Oh, incredibly high. The deep gravitational well of the primary
Speaker 3: galaxy constantly captures these smaller satellite galaxies.
Speaker 2: And as a dwarf galaxy orbits the larger.
Speaker 3: Host, gravitational tidal forces begin to shred it. The stars
Speaker 3: and gas from the dwarf galaxy are literally stripped away
Speaker 3: and deposited into the extended halo of the primary galaxy.
Speaker 2: It's a process of violent gravitational cannibalism.
Speaker 3: It really is. The primary galaxy isn't necessarily forming all
Speaker 3: those older stars in its massive new suburbs. It's stealing
Speaker 3: them from its neighbors.
Speaker 2: Just ripping them apart.
Speaker 3: Yeah. Over millions of years, as it shreds and consumes
Speaker 3: multiple satellite galaxies, those accreted stars build up the extended
Speaker 3: diffuse optical footprint that GWST detected.
Speaker 2: So it's this combination of cold stream accretion along dark
Speaker 2: matter filaments and the elevated rate of minor mergers exactly.
Speaker 3: It perfectly explains the physical characteristics observed in the Locktac protocluster.
Speaker 2: The environment acts as an accelerant from mass assembly.
Speaker 3: The galaxies in the dense nodes have preferential acts to
Speaker 3: the cosmological buffet, basically.
Speaker 2: Allowing them to rapidly assemble extensive stellar envelopes far earlier
Speaker 2: than galaxies starved of those resources in the isolated voids.
Speaker 3: Right, the ultimate verdict on the nature versus nurture debate
Speaker 3: in the early cosmos is unambiguous at this point.
Speaker 2: Nurture plays a massive structural role almost from the very beginning.
Speaker 3: Absolutely, just one point two billion years after the Big Bang,
Speaker 3: which is barely nine percent into the universe's current lifespan,
Speaker 3: a galaxy's physical evolution was already deeply dependent on its
Speaker 3: cosmological zip code.
Speaker 2: You cannot model the early universe assuming galaxies evolved as
Speaker 2: isolated islands. They were heavily manipulated by the interconnected ecosystem
Speaker 2: they inhabited.
Speaker 3: And it forces a necessary paradigm shift in our cosmological simulations.
Speaker 3: Theoretical models must prioritize the macro environmental context, even at
Speaker 3: extreme redshifts.
Speaker 2: The gravitational web, the hydrodynamics of the inflowing gas, the
Speaker 2: proximity and kinematics of neighboring dark matter halos.
Speaker 3: Right, these are secondary effects that emerge billions of years later.
Speaker 3: They are the primary drivers of morphological evolution from day one.
Speaker 2: But you know, this accelerated growth model presents a really
Speaker 2: fascinating dichotomy to me. How So, Well, if the early
Speaker 2: protocluster environment is basically a hyper efficient feeding mechanism that
Speaker 2: builds these massive galaxies rapidly, how do we reconcile that
Speaker 2: with the eventual fate of these structures? Right? Because we
Speaker 2: established earlier that in the modern mature universe, cluster galaxies
Speaker 2: are red and dead the environment eventually chokes them. So
Speaker 2: does the very process of this rapid environment driven mass
Speaker 2: assembly inadvertently seal their fate? Like does the gluttonous growth
Speaker 2: trigger the mechanisms of their own destruction?
Speaker 3: It does. The thermodynamics of the environment virtually guarantee it.
Speaker 2: It's a double aided sword exactly.
Speaker 3: In the early epoch, the dominant process is the accretion
Speaker 3: of cold gas along the filaments, which fuels the growth. However,
Speaker 3: as the protocluster continues to pull in more mass, the
Speaker 3: depth of the gravityational potential well increases significantly, and so.
Speaker 2: The velocities of the infalling galaxies and gas clouds increase.
Speaker 3: And as those velocities increase, the collisions become far more energetic.
Speaker 2: The friction intensifies.
Speaker 3: Precisely, the kinetic energy of all that infalling matter is
Speaker 3: converted into thermal energy through massive shocks.
Speaker 2: So the diffuse gas permeating the protocluster begins to heat
Speaker 2: up rapidly.
Speaker 3: Yes, eventually the temperature of this intercluster medium crosses a
Speaker 3: critical threshold. It becomes so hot that it can no
Speaker 3: longer condense and cool down to fom molecular clouds.
Speaker 2: So the cold streams that were feeding the galaxies are disrupted.
Speaker 3: Evaporated by the expanding volume of superheated plasma.
Speaker 2: The buffet just closes exactly.
Speaker 3: The environ transitions from a feeding tube to a blast.
Speaker 2: Furnace, and as that plasma thickens and heats up, the
Speaker 2: ram pressure stripping we talked about earlier finally kicks in.
Speaker 3: Yeah, The galaxies, which grew so massive and bloated during
Speaker 3: the early feeding phase, now find themselves flying through a dense,
Speaker 3: hot wind that violently tears away whatever cold gas they
Speaker 3: have left.
Speaker 2: It is such a profound evolutionary trajectory. And furthermore, the
Speaker 2: rapid mass assembly in the early universe often fuels the
Speaker 2: rapid growth of the galaxy's central supermassive black hole.
Speaker 3: Right, Yes, that's another crucial factor. As massive amounts of
Speaker 3: gas funnel into the galactic center, the black hole begins
Speaker 3: to accrete matter at a phenomenal rate, becoming an active
Speaker 3: galactic nucleus or AGN.
Speaker 2: And AGN feedback is perhaps one of the most violent
Speaker 2: regulatory mechanisms in the universe.
Speaker 3: Oh, without a doubt, we actually.
Speaker 2: See this actively happening in other structures from this era,
Speaker 2: like the so called spiderweb protoclusters.
Speaker 3: The spiderweb protoclusters are exquisite examples of environment driven regulation.
Speaker 2: So what exactly happens there?
Speaker 3: In these systems? The central supermassive black hole is accreting
Speaker 3: matter so voraciously that it generates colossal jets of relativistic
Speaker 3: particles in intense radiation, and.
Speaker 2: These jets punch out into the surrounding intraclusters.
Speaker 3: Right. The energy injected by the AGN is so immense
Speaker 3: that it physically blows the cold gas out of the
Speaker 3: central galaxy and heats the surrounding environment, effectively halting star
Speaker 3: formation not just within the host galaxy but across massive
Speaker 3: swaths of the entire cluster.
Speaker 2: Wow. So the central black hole essentially acts as a
Speaker 2: thermostat for the entire galactic neighborhood.
Speaker 3: Exactly. If the environment feeds the galaxy too quickly, the
Speaker 3: black hole ignites and violently shuts off the fuel supply
Speaker 3: for everyone.
Speaker 2: It's a self regulating macrosystem.
Speaker 3: Yeah.
Speaker 2: And we also see this extreme feedback in the distant
Speaker 2: hot dust obscure galaxies or hot dogs, right, the ones
Speaker 2: discovered by JAWST.
Speaker 3: Yes, the hot dogs represent an extreme phase of this
Speaker 3: evolutionary cycle.
Speaker 2: They are just incredibly massive, hyper luminous galaxies in the
Speaker 2: early universe that are completely enshrouded and thick, obscuring clouds
Speaker 2: of dust, and.
Speaker 3: The infrared radiation they emit is staggering. Recent kinematic analysis
Speaker 3: using JAWST suggests that much of this dust is not
Speaker 3: settled in the galactic disc, but is being violently expelled
Speaker 3: outward along the polar axis of the galaxy.
Speaker 2: Driven by the intense radiation pressure of a buried, hyperactive
Speaker 2: supermassive black hole.
Speaker 3: Exactly, the central engine is literally blowing the galaxy's raw
Speaker 3: building materials out into intergalactic space, and.
Speaker 2: That expelled dust and heavy element enriched gas eventually cools
Speaker 2: and mixes into the surrounding environment, chemically altering the intracluster
Speaker 2: medium For the next generation.
Speaker 3: Galaxies, the feedback loops are just endless and deeply intertwined.
Speaker 2: Nothing in the universe evolves in pure isolation. The early
Speaker 2: cosmos was a chaotic, violent, but fundamentally interconnected thermodynamic.
Speaker 3: Ecosystem, and the discovery of the morphological differences in the
Speaker 3: Locktac protocluster provides the foundational evidence for that interconnected reality.
Speaker 2: However, as robust is the multi wavelength data from subru,
Speaker 2: Hubble and JWST is, the Locktac protocluster remains a single,
Speaker 2: albeit massive data point.
Speaker 3: Right, It's just one structure. To elevate this from a
Speaker 3: profound observation of one specific region to an ironclad universal
Speaker 3: law of early galaxy formation, the sample size must increase dramatically.
Speaker 2: We need to know if the Locktac protocluster was a
Speaker 2: unique anomaly like a particularly weird hyperactive neighborhood, or if
Speaker 2: this rapid environment driven structural inflation is the standard rule
Speaker 2: for all dense environments in the early.
Speaker 3: Universe, and that requires mapping and analyzing dozens, if not hundreds,
Speaker 3: of these ancient structures, which.
Speaker 2: Brings us to the next generation of astronomical instrumentation which
Speaker 2: is being brought online specifically to execute that massive survey.
Speaker 3: Yes, the suber telescope itself is currently undergoing a transformative
Speaker 3: upgrade to its spectrosnopic capabilities.
Speaker 2: A prime focus spectrograph right the Udihulit PFS.
Speaker 3: Exactly, it will revolutionize our ability to map these early
Speaker 3: structures because while the hypersuprime cam can image vast areas
Speaker 3: and identify candidates using narrow band filters, the PFS will
Speaker 3: allow astronomers to simultaneously capture the detailed spectrum of thousands
Speaker 3: of individual objects across a massive field of view.
Speaker 2: And spectroscopy is the key to unlocking the kinematics.
Speaker 3: It absolutely is.
Speaker 2: Instead of just seeing a glowing dot and estimating its
Speaker 2: redshift based on a filter, spectroscopy breaks the light down
Speaker 2: into its constituent wavelengths, revealing the exact chemical signatures and
Speaker 2: the precise velocity of.
Speaker 3: The galaxy, so you can measure exactly how fast those
Speaker 3: four massive nodes in the Locktac protocluster are moving toward
Speaker 3: each other.
Speaker 2: It transitions the data from a two dimensional map into
Speaker 2: a fully realized three dimensional kinematic model exactly.
Speaker 3: Furthermore, the development of the next generation wide field adaptive
Speaker 3: optic system, known as Ultimate, will dramatically reduce the blurring
Speaker 3: effects of Earth's atmosphere over unprecedentedly large fields of view.
Speaker 2: So this will allow ground based observatories to achieve spatial
Speaker 2: resolutions that rival space telescopes, but across much larger areas
Speaker 2: of the sky.
Speaker 3: Right, and the synergy between those massive high resolution ground
Speaker 3: serve and the continued targeted infrared supremacy of the James
Speaker 3: Web space telescope is going to define the next decade
Speaker 3: of observational cosmology.
Speaker 2: They will systematically hunt down these ancient construction sites, peer
Speaker 2: through the dust, and map the optical footprints of the
Speaker 2: galaxies inside them.
Speaker 3: And I would heavily bet that the lock Tack mechanics
Speaker 3: the rapid environment driven assembly of galactic suburbs will prove
Speaker 3: to be the universal standard.
Speaker 2: The principles of thermodynamics and gravity strongly suggest you are correct.
Speaker 2: I mean the underlying physics of cold stream accretion and
Speaker 2: dynamical friction are not localized phenomena.
Speaker 3: Now, they are universal mechanics, dictated by the distribution of
Speaker 3: dark matter.
Speaker 2: From the microscopic quantum fluctuations in the first fractions of
Speaker 2: a second to the sprawling multi million light year filaments
Speaker 2: of the cosmic web. The architecture of the space adding
Speaker 2: a galaxy inhabits fundamentally and unavoidably dictates the structural object
Speaker 2: it will become.
Speaker 3: It really is a staggering realization about the Maca Hannicks
Speaker 3: of the cosmos.
Speaker 2: The universe didn't wait billions of years to mature before
Speaker 2: enforcing the rules of structure and environment.
Speaker 3: Not at all.
Speaker 2: Just one point two billion years in, the invisible scaffolding
Speaker 2: of dark matter was already acting as an inescapable evolutionary force.
Speaker 2: If a galaxy was born in the dense hub of
Speaker 2: a protocluster, it was already rapidly pulling in mass, tearing
Speaker 2: apart its smaller neighbors, and sprawling outward into a massive
Speaker 2: structural footprint, operating under a completely different set of physical
Speaker 2: rules than a galaxy born in the isolated voids.
Speaker 3: The environmental effect was inextricably woven into the fabric of
Speaker 3: galaxy evolution from the earliest conceivable stages of structure formation, and.
Speaker 2: There is a profound philosophical resonance in that scientific reality.
Speaker 2: There is think about it. We constantly analyze how we
Speaker 2: are shaped by our own environments, how our cities are communities,
Speaker 2: the resources available in our neighborhoods, and the local structures
Speaker 2: we inhabit dictate our growth and our trajectories.
Speaker 3: And it turns out the most incomprehensibly massive structures in
Speaker 3: the Cosmo are subject to the exact same fundamental rule
Speaker 3: of nature.
Speaker 2: At every scale of existence, from the microscopic behavior of
Speaker 2: excited electrons to the psychological development of humans to the
Speaker 2: thermodynamic evolution of entire galaxies. We are all products of
Speaker 2: the environments that surround us.
Speaker 3: The universe itself is a product of its environment.
Speaker 2: It perfectly bridges the gap between the esoteric physics of
Speaker 2: early structure formation and our intuitive understanding of interconnected systems.
Speaker 2: We are essentially observing the macro scale equivalent of a
Speaker 2: universal truth.
Speaker 3: It's beautiful, Honestly it is.
Speaker 2: I want to leave you the listener, with a final
Speaker 2: thought to mull over long after this discussion ends. We
Speaker 2: have spent this time detailing how astrophysicists utilize the specific
Speaker 2: quantum mechanics of liman alpha emission, massive wide field surveys,
Speaker 2: and precision infrared mirrors to look back twelve point six
Speaker 2: billion years. They finally developed the exact right filter to
Speaker 2: see the invisible scaffolding that was shaping the Luctac protocluster.
Speaker 2: They found the neighborhood that was manipulated the galaxies. But
Speaker 2: if the absolute largest structures in the early universe were
Speaker 2: already silently organizing and shaping their galactic inhabitants just one
Speaker 2: point two billion years after the Big Bang, what massive
Speaker 2: invisible cosmic structures are currently shaping our own Milky Way
Speaker 2: galaxy right now?
Speaker 3: Oooh, that's a deep question, right.
Speaker 2: We know we are being pulled toward the Great Attractor,
Speaker 2: We know we are part of the Laniakia supercluster. But
Speaker 2: what vast unseen gravitational forces are dictating our ultimate evolutionary
Speaker 2: fate as we fly through the cosmos? Forces that we
Speaker 2: simply haven't invented the right mathematical or optical filter to
Speaker 2: see yet.
Speaker 3: It's a humbling reminder that we are constantly swimming in
Speaker 3: an ocean of gravitational dynamics that we are only just
Speaker 3: beginning to accurately map.
Speaker 2: Keep looking up and keep questioning the empty spaces.