How to Make a Galaxy | Wisconsin Public Television

How to Make a Galaxy

How to Make a Galaxy

Record date: Nov 14, 2017

Jacqueline van Gorkom, Professor in the Department of Astronomy at Columbia University, studies neutral hydrogen in the universe and discusses the influence collision, merger and gas exchange have on how galaxies form and evolve.

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Episode Transcript

- It's a pleasure

to welcome you here.

Thank you all for coming out.

The Whitford Lecture is the

Department of Astronomy's

distinguished lecture series,

and it is named in honor

of Albert Whitford, who

was a longstanding member

of our department

and the director

of the Washburn Observatory

on campus.

And this year, this semester,

I'm pleased to

introduce our lecturer,

Professor Jacqueline van Gorkom

from Columbia University.

Jacqueline is a world-renowned

radio astronomer.

She'll be telling us about

some of her work tonight.

She has been at Columbia for

much of the past three decades.

And so, without further ado,


- Thank you.


So I'm actually not going

to talk about how to make

a galaxy because I really don't

know how to make a galaxy.

But I'm really

going to talk about

neutral hydrogen image

of the universe.

Now, why do I talk about that?

That's something in the '80s.

I was at Very Large Array

in New Mexico,

and I went around, I might

even have come to Madison,

giving colloquia saying,

I want to make a neutral

hydrogen image of the universe.

Why not be ambitious?

So why did I want to do that?

So I just moved to New Mexico

and there's this

Very Large Array

and I was making images of

neutral hydrogen around galaxies

and so one thing we found

was this picture here,

that bright spot,

that's actually

a very big galaxy

just like our own.

It's really big.

All the blue stuff around it,

is neutral hydrogen.

And so the image of the

neutral hydrogen remains.

And so I thought, well, wow,

I thought it was a big galaxy,

but actually there was

much more than that.

It looks totally different when

you look at neutral hydrogen.

And so I thought, well,

it would be really interesting

to make an image of the whole

universe in neutral hydrogen.

And so the next three decades

I've been trying to do that,

and I'm actually just

now beginning with Eric.

But I'll talk a bit about things

that we found on the way there.

So, first of all, what is this

emission of neutral hydrogen?

Neutral hydrogen is an atom. It's the simplest atom there is.

It's an electron and proton.

And normally the electron

and the proton

rotate in the same direction.

And then about once every 10

million years, the electron

decides to start spinning

in a different direction,

the opposite direction.

Once every 10 million years.

So it doesn't happy very often,

but when it happens,

it gets a little bit less energy

so it emits a wave

at 21 centimeter

and it's a radio wave.

So you can actually

observe neutral hydrogen,

and since the universe

is filled with it,

it doesn't matter

that it happens

once every 10 million

years per atom

because there's how many atoms

that you can observe it.

So the Very Large Array

is a radio telescope,

and so I've been using that

to make images of the

neutral hydrogen.

And I've had a lot of

students over the years,

and they make great pictures.

At left you see a quilt made by

my most recent students

who made the field array

in a quilt.

And at right you

see a nice sunset.

So the Very Large Array is

27 dishes in the plains

of St. Augustine in New Mexico.

And so since you are observing

at very low wavelengths,

you need to have a very big dish

to get enough angular

resolution, right?

If you want to see details,

you need to have a huge dish.

So instead what you do at radio,

you say I don't make one dish

but I make many, many dishes

and I combine the signals.

So that's what we do at VLA.

And, actually, not only that,

we also use the fact

that the Earth rotates. It does.

So if you think about it

looking from the sky,

you see that the three

arcs of the VLA

trace out a circle

in eight hours.

And so if you combine all the

signals, it's like having a

giant dish that gives you

very good resolution.

Not only that, you can actually

also move out the antennae

to different locations,

and so you can combine data

taken at different days, so

you get different resolution.

And so this is how you

take out an antenna

to a different location,

it's a circle transporter.

It's going on a rail on the

plains of St. Augustine.

You take up the antenna,

it happens every four months,

and then it gets transported

to a different place.

And I don't know

how many of you

have been on Highway 60

going by the VLA.

It's a beautiful spot,

but if you drive by Highway 60, at some point you see a sign:

"Watch out,

crossing telescopes."


And so that's what happens.

Okay, but so it's a

fantastic instrument,

and I actually lived

there for eight years.

And so I actually lived

close to the VLA,

I was one of the few scientists.

And this is telescope

in Pie Town.

And for a long time I thought

I wanted to be the

astronomer in Pie Town.

There's about 10 people there,

but it's very beautiful.

And so when I was there,

I also started--

And so after I had been

close to the VLA for a while

I decided to move to Manhattan,

so it's a

little different.


And so then I already

started thinking about

what does the environment do,

in that case to people,

but it also does something

to galaxies, right?

People in Datil, New Mexico,

are actually very different

from people in Manhattan.

And for a while I

went back and forth,

and every time I

made the transition,

I had to sort of

culturally adapt again.

In Datil, if you saw someone,

you better stop

and talk with them.

In New York,

you better not stop.


So it's very,

very different.

And the other questions is:

are galaxies different in

different environments?

So that is the first

part of the talk.

And then-- So I'm first going

to talk about how galaxies

are nearby in different


and then I'll talk

a bit about how

galaxies change if you

look back in time.

So that is what I'm

working on now.

So are galaxies different

in different environments?

So now I have to start telling

you about environment,

and so I'm going to tell you

that in a cosmological setting.

So what you see here is you see

the results of a simulation.

And you see four different times

in the life of the universe.

Okay, this is very

early in the universe,

shortly after the Big Bang.

So, on the top left,

you see a picture

that was very early in the

universe. It looks very smooth.

So what you see here

is a simulation

actually not of matter

but of dark matter.

So it is basically how

structures go in the universe.

You might not notice

but most of the matter

in the universe is dark matter.

We don't know what it is,

but it is a lot of matter.

And so this is the distribution

very early in the universe.

And if you go to the right,

it's somewhat later.

And you see that

you start forming

these bright filaments

and dark spots.

And if you look here,

you see it's very clear.

So this is even later

in the universe,

and this is today, Sequence 0.

That is what the universe

looks like today.

So you see these very

bright filaments.

That means that's

very high density.

So lots of mass.

And then in between you

see these dark spots.

And those are actually

very empty spots.

They're called voids.

And so in the local universe,

about 95% of space is

really, really empty.

It's voids and they're

very interesting.

So I'll tell you a little

bit about that too.

But so these are the filaments.

Most of the galaxies

are in filaments,

and when filaments connect,

you might get

clusters of galaxies

where there's thousands of galaxies very close together,

and they're

gravitationally bound.

So that's, I'm actually first

going to talk about clusters.

On the lower right, you

see now the distribution

of the dark matter,

and on the top, you see

the distribution of light.

And so if you look in

different environments,

it turns out galaxies

look slightly different,

which is pretty amazing.

So notice if you look

in groups or filaments,

you see many spiral galaxies.

You see disc galaxies.

Now, if you go to

a higher density

where these filaments connect,

you get clusters

of galaxies.

So there are thousands

of galaxies.

And if you look very carefully,

you see, especially at the left,

that most of the galaxies are

actually more elliptical shaped.

They don't have discs,

they don't have these

spiral patterns.

So in clusters of galaxies,

you have many more

early type galaxies,

discs without star formation,

or ellipticals than in groups where you have spirals.

And so this is the nearest

cluster of galaxies.

It's the Virgo cluster,

and you see

many, many of these

early type galaxies.

And so the question is:

why is it that in

different environments

there are different

kinds of galaxies?

So here is a

morphological sequence

of what galaxies

actually look like.

On the left, you

have ellipticals.

They are round.

They have no star formation.

On the right, you have

the spiral galaxies.

And so clusters are dominated by

ellipticals and disc galaxies

without star formation,

without any gas.

And everywhere else

you see something.

This is what we call the

density morphology relation.

Not very original.

And so the question is:

how do you get the density

morphology relation?

There are two extremes.

One is galaxies formed in

different environments,

and that is why they have

different morphology.

The other possibility is that

galaxies are morphologically

transformed by

their environment. Right?

And so you can go back

to Datil and Manhattan.

Are people born in

New York different

than people born in Datil,

or do they just change every

time they go back and forth?

So I had a student

who wrote a thesis

on what can happen to

galaxies in clusters.

And so she had beautiful data,

and then I said,

well, you have to

write one chapter

where you describe

all of this

and which galaxies can

actually get affected

by the environment,

the physical processes.

So she disappeared

for about a month,

and then she came

back with this.

So she said, well,

these are galaxies.

So in yellow, you see

the stars of galaxies.

In blue, you see the

interstellar medium of a galaxy.

So galaxies, these galaxies

have a lot of gas in the disc,

and they form stars

out of that gas.

In clusters between the

galaxies, there is very hot gas.

It's like 10 million degrees,

a hundred million degrees.

It's very, very hot.

And so if you see purple,

that's the hot gas.

So you see in the middle

there a happy galaxy.

What happens when this galaxy

falls into the cluster?

It can get ram pressure stripped

which means that the hot gas

pushes out the cold gas.

So years ago, cold gas is

flying out of galaxies

and the hot gas pushes it

especially out of the

edges of the disc.

So what you would see is

that gas gets affected

and the stars just

stay the way they are.

Okay, here is

another possibility.

So these galaxies are

surrounded by this hot gas.

So it can, cold

gas can evaporate.

It's very unpleasant

for the galaxy.

And, again, only the

gas will get affected.

But it can also

gravitationally interact.

So if two galaxies

get close together,

they can pull the stars

out from each other.

So, in that case, both the stars

and the gas will get affected.

So you get these

very long tails.

Probably doesn't happen

very often in clusters

because galaxies move so fast

with respect to each other.

So they don't have much time

to do this interacting.

Okay, and then it can be the

global potential of the cluster

can also sort of

truncate the galaxies.

That's called tidal truncation.

It would also affect

the stars and the gas.

And then there's something

that's currently really popular.

It's called starvation.

So what that is, is the idea

is that galaxies have this

reservoir of gas around them,

and that gas will,

slowly over the life

of a galaxy,

continue to fall in and

supply gas to the disc

so that they can

continue forming stars.

Now, if a galaxy falls

into a cluster,

that reservoir

might get removed.

So then all of the

sudden you have a galaxy

without gas around it

so it just uses up the fuel

in the disc and that's it.

And it doesn't form

any stars anymore.

So that's called starvation.

And this is also very popular. That's harassment.

And so I told you that,

so interactions are probably

not that important,

but people realize

that galaxies,

when they fly through a cluster,

they get little pulls

from all the other

galaxies in the cluster.

So the cumulative effect of all

these little pulls will be that,

again, the stars and the

gas too get affected.

So that's called harassment.

And so the question is:

what do we see in clusters?

And so this student

actually made an image

in neutral hydrogen of the

nearest cluster of galaxies,

which is the Virgo cluster.

So that she said life is

tough for galaxies.

So this is, I still think

this is an amazing picture.

It is not completely the real

universe but it's pretty close.

So what you see is

there's a picture of gas.

So I like gas.

So in the center,

you see this orange.

That is the very hot gas in the

center of the Virgo cluster.

In the center you see M87.

It's a very big elliptical.

And then you see around

it all these blue discs.

So these are disc galaxies

that are falling in.

And to make them visible,

we've blown them all

up by a factor 10.

So they are at the

proper location,

but the sizes are much larger than they are in reality.

But what you should

notice is that

right in the center

of the cluster,

these discs are

very, very tiny.

In the outer parts,

they are huge.

Now, this is something

that you expect from

ram pressure stripping.

If a galaxy falls

into the cluster,

the outer parts of

the gas get removed.

And so you see, I think this

picture tells you everything

that can happen to a

galaxy in a cluster.

But, here are some overlays.

So what you now see is you see

optical images of these galaxies

and the contours are the

neutral hydrogen gas.

So you see on top, you see

some galaxies are really

in the outer parts

of the cluster.

They have very extended

neutral hydrogen.

Nothing has happened to them.

And the bottom row,

you see galaxies

that have only some gas left, right in the center,

so that's it's completely

gone out of the disc.

That is why they are so smooth.

So that is very,

very interesting,

and that is almost due to

ram pressure stripping.

And then there's this galaxy,

and you see 4522.

That is one of the most

interesting galaxies in

the cluster.

So there it looks as if the gas

is being pushed out right now.

That it's being pushed

out of the disc.

So that was, I'll get

back to that galaxy.

But another thing that was very

interesting in the cluster is

if you look at a certain

distance from the center,

you look at these gas discs,

you notice that all of them

have tails in each one

that point away from the

center of the cluster.

And so you see, on the sides,

you see blowups of each

of these galaxies.

Again, you see the optical,

and then in blue you see

the neutral hydrogen.

And what that shows is that,

so in all these cases

here you see that, for example,

that the disc comes through

but the gas is being pushed out.

That galaxy is somewhere there. So it's falling in.

It's being pushed out.

And here the same thing.

The tail points away

from the center.

So we think that in this

case this indicates

that this is sort of the

region where the galaxies

are beginning to be affected

by the cluster gas,

which, again,

we think is really cool.

Okay, now this is

this galaxy NC4522.

It's an amazing galaxy.

So you see that the gas is

currently being stripped out.

Maybe I'm not going to say much,

but one of the

interesting things is

so you can actually look at

the optical stars in the discs

and from the spectra

we can estimate

when star formation

happened last in the disc.

And so from

this we know

when the gas was removed

from the outer disc.

Which is a really

important hint.

And so why is that important?

So we think it

started forming stars

about 100 million years ago,

and the galaxy

is right there.

To get it stripped, you

would think it has to

go through the center,

but that would take

about 700 million years.

Well, actually, stars

started forming about

100 million years ago,

so we think, in this case,

the galaxy got stripped

right in the outer parts.

I think we see that now

very clearly happening.

When a cluster forms, you have

here the big cluster of galaxies

and then you have smaller

groups of galaxies

falling into the cluster.

And these groups also

have a lot of hot gas.

And so, actually you see it

here, when a group falls in,

it might stir up the hot

gas in the cluster.

And so that galaxy was just

at a point where the hot gas

from the different

parts collided and

affected the galaxy.

And so we actually think that

when you form a cluster,

you actually affect the galaxies

around the cluster very much,

and that's a really interesting

thing to see happening.

So this is of the

density of the gas.

So this is a high-resolution

movie of galaxies

that are falling into

the cluster, in the

center of the cluster.

And you can actually see that

the gas is being stripped out

and there are these long tails

of gas that are left over.

So we think we

understand a lot now.

We understand that galaxies

that fall into clusters get stripped of their gas,

and that is why there is no

star formation in clusters.

We have tons of data.

We really believe it.

And this is the outer parts

where you see these things.

So we know now that galaxies

and clusters lose their gas

because they come into

high density regions.

Now, we can also

say what happens,

I pointed out these voids,

these very empty regions.

What happens there?

And so there, actually, so these

are very low-density regions.

This is where the universe

evolved very, very slowly.

And so there we can

see how galaxies grow.

There's the picture

I showed you before.

So there's very large,

empty regions.

And so what do we know

about galaxy growth?

We a lot about the

things we can see.

We know how dark

matter assembles

and forms a large structure.

But how you actually form

a galaxy out of that,

we don't really know so well.

And so people have been

making a lot of simulations,

especially in the last 10 years,

and they sort of realized

that galaxies might,

so there's two ways you

can form galaxies.

Either you have a dark halo,

another dark halo,

they merge, gas falls in,

you form a galaxy.

Two galaxies merge and

become bigger and bigger.

It's called hierarchical

galaxy formation.

But, more recently, people have

realized that actually galaxies

might mostly grow by

slow infall of cold gas

directly into the disc.

And so they make very extensive

predictions of how that happens.

And one of the predictions

is that at a current time,

you should still

see this in voids

where there is small galaxies.

And so I'm going to show

you some results of that.

So we've been looking at voids.

You see the distribution of

galaxies in the nearby universe

as mapped out by the

Sloan Digital Sky Survey.

So there's a big survey

in the local universe

of all the galaxies.

And so the bright orange

is the destiny where all

the galaxies are,

and the dark spots is where

you see in the nearby universe

no galaxies, except for a few,

and that's these little diamonds that we have been pointing at.

And so we've been looking at

the gas in these galaxies

in the largest underdensities

of the voids.

And here you see, so

not many people have

seen galaxies in voids.

Here you are. You can see

galaxies in voids. They're tiny.

You can't tell that,

but they are really tiny.

The forming starts

very actively.

So these are galaxies that are

just now beginning to grow.

And here, this is also

very interesting.

So this is now, you see the

tiny galaxies on the left. That's photographs.

And then contours is

the neutral hydrogen.

So you have tiny galaxies in a

void, but unlike in clusters,

they have gas that just

extends very, very far out.

It's amazing.

And here you see this was

the first galaxy we

made an image of,

and it is also the most

interesting galaxy we found,

which was quite interesting.

So you see, on the left, you

see this tiny disc of a galaxy.

That galaxy is rotating like

that. That's the stars.

Now the contours is

neutral hydrogen.

Giant envelope.

It's rotating like this.

So we call it the polar disc,

for obvious reasons.

So that basically we think

is one of the best examples

of a galaxy that is

actually right now

accreting this gas

onto the galaxy.

It's very smooth.

If it was merging, the

optical disc wouldn't

look that undisturbed.

And we found some filaments in

voids, lots of them actually.

Gaseous filaments, and

in these filaments,

probably, galaxies form.

And this is a galaxy.

I just have to show you this.

The local group, our galaxy

is actually close

to one of the largest

voids that we know of.

There's a huge void

very close to us,

and there is also

a little galaxy.

On the left you see it.

It's tiny, has a few stars.

Giant envelope of H1,

and, again,

the motion of the gas indicates

that there's something

weird going on.

So we think that's

another indication

that there's infall of gas.

So the conclusion

from this void survey

is that by looking for it,

you select a very interesting

sample of galaxies.

They might still be

accreting gas, and they

are very metal poor.

So we think these are galaxies

that have been very

slow in forming.

So, again, the H1

tells us a lot.

And this is a terrible picture,

but I think it's one of the

most interesting pictures

I've ever seen.

So this is made in 2014 by

some people in Australia.

And this is the closest

that you can come

to making an H1 image

of the universe.

So this is basically a

picture of the whole sky.

And what you see in the contours

is the density of galaxies.

And in color, you see

whether the galaxies

are gas poor or gas rich.

So red is very gas poor

and blue is gas rich.

And contours are

galaxy densities.

So that basically

tells you that

everywhere where

there are high densities,

all of the sudden the galaxies

are very, very gas poor.

And if you go to low densities,

they are very gas rich.

I've just shown you that.

You know this.

But I think this is a

fascinating image, and I just

want to make a better image

eventually of this.

It's great.

Okay, so now, in the last

sort of 15 minutes or so,

I want to tell you about CHILES.

That's the thing I've been

working on a lot recently,

together with Eric.

CHILES stands for the Cosmos H1

Large Extragalactic Survey.

And it's a thousand-hour


with the Very Large Array,

it's ridiculous.

So we're getting lots

and lots of data.

We're working very hard.

And this is to show you

what astronomers do.

They drink beer.


And these are all people,

so there's about 26 people

in this collaboration,

they are spread

all over the world.

And the reason why it's

important to talk about this

is that radio astronomy is

about to undergo a revolution,

I think, because there's

all these new telescopes

coming online around the world

and so people from all

these different telescopes

are all in this collaboration.

So we're all talking

all the time

about the great things

we're going to do.

So why do we want to do this?

So this is basically a

survey where we are making,

so now I'm not looking at one

cluster or a bunch of voids,

but we are staring at

one point on the sky,

and we are integrating

for a thousand hours.

So we get a very,

very deep image.

Right? A thousand hours.

Normally you get six

hours or something.

This time you get a thousand. And why is this so special?

So the Very Large Array, which

came online in the 1980s,

has been upgraded in the

last seven years or so.

So it used to be the best

telescope in the world,

and in 2010 it was still the best telescope in the world.

But now it's a factor 10 better

in every possible respect

because the electron is

completely renewed.

And so what is now

possible is that we,

in this one deep observation,

we probe, in distance,

out to about 4.6 billion

years back in time.

So we make a very deep

observation, and we can see

the motions of the galaxies

over that whole range.

So we make these images

of neutral hydrogen

over this tremendous range.

That's what we are trying to do. It's a big project.

So we're going back to

what we see redshift of 0.45.

It's about 4.6

billion light years.

And we are basically

making pictures.

We are looking what the

kinematics look like,

what the motions are, and just

what the content is of galaxies

with respect to this

so-called cosmic rift,

the distribution of

the galaxies at large.

So what we're doing now

about galaxy evolution

going back over that time, we

know a lot about star formation.

If you look at the

star formation density

in the universe,

we know that in the last

almost 10 billion years

the star formation rate

dropped tremendously.

So the universe is slowly

forming less and less stars.

And certainly this range

that we are looking,

it's just going down

very, very fast.

Well, what do we

know about the gas

in the galaxies

over that range?

Just about nothing.

So that is what

this picture shows.

This is sort of summary of

where we are right now

in our knowledge of

neutral hydrogen by just

doing blind surveys.

So this little area here,

that is ALFALFA.

It's a fantastic

survey with Arecibo.

We know a lot about

galaxies very nearby.

Beyond that, we know

almost nothing.

So this is, again, the

structure of the cosmic rifts

as seen in galaxies,

so you see these kind of voids.

And so there's a number of

regions that have been probed.

I have to try this now.

Okay, you see these

two little things

sticking out to the right? That's a survey by [inaudible].

The thing that you're seeing

there, the very tall thing,

that's the CHILES survey.

So that's the range where

we are going to find

all these galaxies in H1.

That's our plan.

And so we've been

observing since 2013,

and we'll continue

observing until 2019.

So... this is just to show

you that we can do it.

This was a pilot.

And here you see the pilot

only did half the range

that we are doing now.

And what you see is,

so here you see

the distribution of the galaxies at different distances.

And so you see, again, you see

these large structures.

So you see walls here and there.

And these are galaxies that we

detected in H1, and so, again,

you see that the morphology

is really different in

different environments.

So this is very nearby, very

extended in a very empty region.

If you come to a wall, you

see that galaxy get distorted. It has companions.

And if you go to an

even denser region,

you see galaxies merging.

So this, it shows you this

was done in only 60 hours,

and that already shows

you that you get

very interesting results

if you do this.

You really see the

neutral hydrogen

as a function of environment.

So I won't bore you with that.

But I do want to bore you

with this because this is,

I am actually very, very

proud of this picture.

So this is noise.

So why do I get

excited about noise?

On top, you see the

result of the pilot.

So where we observed over this

enormous frequency range,

so obverse over 240 megahertz

in one observation.

That's really special.

Very high resolution.

And you see that mostly the

noise actually is flat.

So that's about the

noise we should range,

but then you see these peaks.

And what are they?

They are due to satellites,

cellphones, GPS, all the

stuff you shouldn't be using

because it completely

ruins our data.



And so this is now the new data.

So it is twice the range.

This is the real survey.

And it's actually

really interesting.

So, first of all, you can

see that this is 180 hours,

we really go down in the noise.

So we are still,

we are doing well,

by integrating longer,

we get less noise.

And you see that

some of these peaks,

they stay at exactly

the same place

so that the satellites

keeping there.

But some disappear

and some appear.

It's sort of fascinating.

So it is not

completely constant.

In general, there is more

satellites coming,

which is really a big scandal,

but that's what's happening.

And another good thing is, so this is sort of real strange,

if you go to higher,

further distances,

it actually gets better again.

So we might get great

results eventually.

That's what we are doing.

So this is the result

comparing the pilot

to the first 180 hours.

You see that if you integrate

longer, the H1 grows.

You observe more and

more neutral hydrogen.

Now, this is interesting.

I had a student

working on this,

the first phase of the series.

And so she said,

can we do something

with the first 180 hours?

So here you see the distribution

of the optically long galaxies

as function of, basically,

distance, redshift.

And you see there are

these walls. Right?

So there is this structure

in the cosmic web.

And so she said, well, let's

just have a look and see

if you find something at a

distance of a redshift 0.37.

Nobody has ever made an H1

image at that distance.

And so the first

things we did was

we compared in the galaxies in a wall at a redshift of 0.12

to galaxies at a

redshift of 0.37.

And here is the result.

So that might not mean much to

you but these are two spectra,

and so what you see in

the wall at 0.12,

the mass in gas on average

is about two times

10 to the nine.

At 0.37, going back in time,

the mass is three times

10 to the nine.

And we think that is a

significant difference.

This is just the thing

that we wanted to see.

That the gas content might

actually being going up

if you go back in time.

And so we might have found that.

So now this is one of our

great discoveries so far.

So that's Ximena.

That's the student.

And Hansung Gim.

He's from UMASS.

They did it together, basically.

So, first of all,

we detected a galaxy.

And there it is.

So you see a tiny galaxy.

It's actually not a tiny

galaxy, a big galaxy,

but it has a huge neutral

hydrogen envelope.

And so when we found that,

we weren't really sure

whether we could

believe it or not.

So Hansung went to a

telescope in Mexico

to look for molecular gas.

And he found that,

actually even more amazing,

there is a huge amount

of molecular gas,

more even than

neutral hydrogen.

So this galaxy is very,

very interesting.

It's one of the most

gas rich galaxies

we know about in

the local universe.

This is an optical picture,

and it's really asymmetric.

It has a lot of star

formation on one side.

It's forming stars very rapidly.

And here you see, again,

the overlay of that.

So this is a

complicated picture,

but it shows you that on this

axis you see stellar mass,

on that axis you see H1 mass,

and the little

square is our galaxy

and all these other points

are other kinds of galaxies.

What this tells you is that it's

rich in H1 but not uniquely so.

But then, if you go

to molecular gas,

again the little

square is our galaxy.

It actually is uniquely

rich in molecular gas.

It's more gas rich than any

galaxy nearby that we know.

It's pretty amazing.

It's really, really rich.

And then there's another thing

that's really pretty amazing,

and that is the star formation

rate in this galaxy.

So what you see again,

on the right,

you see the stellar mass

for different galaxies,

and then, on the vertical axis, you see the star formation rate.

And so different kinds of

galaxies have been plotted here

for different parts

in the universe.

So here you see galaxies

that are really nearby,

redshifts of 0.2 and 0.5.

And then the bright symbols

to red are between 0.5 and 1.

And our galaxy is that

big start on top there.

So it's forming stars way

too rapidly for its mass.

Way too rapidly.

It's uniquely unique.

It doesn't exist in

the local universe.

And then, if you

compare it to galaxies

that have redshifts

between 1.5 and 2,

it actually fits in

very, very nicely.

So it looks like there's one

of these very young galaxies

in the very early universe that

is forming stars like crazy,

maybe because gas is falling in,

that we are seeing here

at this redshift.

So that's our big discovery.

We are very happy about that.

So that's the first discovery

in this big, big survey.

So eventually this will become

very, very interesting,

and so you should just

ask Eric to give a talk

about this in a little while. [laughter]

To present all the results.

It's the first step.

And so why is this so important?

It is because all these

other telescopes are

being constructed.

There's MeerKAT in the Karoo

Desert in South Africa.

It's about to start observing.

There's a telescope in

western Australia, ASKAP.

There's a telescope in the

Netherlands being built,

and then, eventually,

there will be the SKA,

Square Kilometer Array,

you might have heard of that,

that will also be built

in South Africa.

So these will all

get amazing results.

They will find many,

many more galaxies.

And you will hear a lot

more about each one.

So I want to finish with,

since all these places

are so interesting,

I went to the Karoo Desert to

look at this telescope there.

And I thought it looked

very much like New Mexico.

It actually really does.

If you drive through Karoo,

you think just like New Mexico,

but then we saw this,

and I said, what is this?

What is this? What is this?

So... what is this?

It's a nest of sociable

Weaver river birds.

So these birds,

they get together.

They start out

with a small nest,

and then more and more

birds come and they build

a bigger and bigger nest,

it's like bees, sort of beehive.

So there's hundreds of birds

making this nest.

So that by itself

is a good reason

to go into radio astronomy,

I think. [laughter]

That's it. Okay, thank you.


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