- I'd like to introduce our
guest speaker for tonight

here at Space Place.

Tonight I'm very pleased
to introduce an astronomer

from the UW
Astronomy Department,

but also a friend of
mine, Eric Hooper.

Eric came to us,

he got his PhD at the University
of Arizona in astronomy,

and then came here
after working at

UT Austin, came here to
Madison where he's been here

for a few years now doing
a lot of different things,

but including a two-year
stint as director of the
WIYN Observatories.

You might remember the W
in WIYN is for Wisconsin.

It's a set of telescopes
that we manage from here,

and Eric was the director
of those for a term there.

But tonight, he's gonna tell
us about some of his research

with the intriguing
phrase cosmic archeology,

but I'm gonna turn it
over to him right now.

So please welcome Eric Hooper.

[clapping]

- Thank you, Jim.

And thank you everybody for
coming out this evening.

I really appreciate it.
We have a big crowd here.

I'm gonna start out by
just giving a shout out

to the organization
that's funding this work,

and that's the National
Science Foundation.

They provide funding
across the country

for a lot of different
interesting science,

not just in astronomy, but
across the whole spectrum

of science, technology,
engineering, and mathematics.

And I'm not the only
one on this project.

So let me introduce some of
the other cosmic archeologists.

I've included the pictures
of our local team here.

These are all University of
Wisconsin Madison astronomers.

The two on the left and right
are graduate students who,

of course, do most of the work.

The person in the middle
is the PI or the
principal investigator.

She's the leader of the grant.

The other two are faculty
collaborators of ours.

But we're not just a
UW of Madison team.

There are other people
I've showcased down
here at the bottom.

These are collaborators
from across the country,

and as you also see, from
other parts of the world.

These are part a large
international team

called the Sloan
Digital Sky Survey.

We'll talk more about
that later in the talk,

so I'm just giving you a little
foreshadowing of that here.

And one of the themes about
this that you're gonna see

throughout this talk is that
a lot of modern scientific

research, including in
astronomy, is done by teams

of people, this is actually
a relatively small team,

and also utilizing
a wide variety

of different technologies
and techniques.

That's gonna be part of
the story of this evening,

is what those techniques
and technologies

we're using to address
the project I'm
gonna tell you about.

Well first, we have to
deal with that title,

that weird title
that Jim alluded to.

He's really hoping I'm
gonna explain what it is.

I know that some of
you may be thinking,

"Oh, that guy, this
is a marketing ploy.

"He just made up the weirdest
title he could think of

"to get a crowd out tonight."

Well, maybe a little bit.

But the fun part of
tonight's talk is

that it is not completely crazy.

There's actually
a grain of truth

in everything in that title,

and I'm gonna explain a
little bit of that here.

And the entire talk
is encapsulated,
really, in the title.

So it's more than
just crazy marketing.

There really is meaning to
everything that's in that title,

and I just wanna unpack
that a little bit here.

But first, a quick
story, little anecdote,

how I actually
came up with this.

It wasn't for this talk,

although the details
of it for this talk,

but it occurred to me while
I was traveling sometime.

I was flying and I
was on an airplane.

And, as often happens,
you sit next to somebody

and they ask, "Well, where're
you going after Chicago?"

And after you say, "Well,
I'm going to Kalamazoo

"and they're going
to Walla Walla,"

then the conversation goes to,

"Oh, well, what do
you do for a career?"

And we sometimes get some
interesting responses

when we say we're astronomers,

because there's just not
that many of us in the world.

And some people find
that really intriguing.

Some people find
that really strange

and they don't know what to do.

and I've often thought,
"What could I say

"that would have a
grain of truth to it

"that would really make people
think it's kinda weird?"

So I've thought, I guess I
could say, given the project
I'm working on now,

I could turn to them.

I could say, "Yeah, so, I'm

"a time-traveling
cosmic archeologist.

"And by the way, let's talk
about this on the 15-hour
flight to Shanghai."

[laughing]
All right.

So let's unpack what
I actually mean here.

Clearly the most
ridiculous sounding part

of that whole title
is the archeology.

I mean, what does astronomy
have to do with archeology,

other than they
both start with A?

I have heard, oftentimes,
that astronomers,

and maybe others, use
archeology as sort

of a metaphor for astronomy.

Here's why.

Because there is an element
of looking into the past

that's inherent in astronomy.

The reason for
that is that light,

and any information
that comes with it,

has a finite travel time.

Now, that may not be readily
apparent to us in this room

because the speed of
light is so rapid,

but when you're talking
about the vast distances

that we are often dealing
with in astronomy,

then it starts
becoming relevant.

For example, the Sun's
light that we see,

is already a few minutes old.

That's not that far in the past.

Center of the galaxy,
when we look at it,

is over 20,000 years old.

The nearest large galaxy,

now we're going over
a million years old.

So by having things very far
away when we look at them,

we are inherently
looking into the past.

Maybe a more
down-to-earth analogy.

I don't know if maybe
today in middle school

and in elementary school
they don't do this,

but in my time kids would
pass notes to each other.

So here's the analogy.

Somebody starts passing
around the note around school

that so-and-so likes
whosie-what-sit.

And by the time that note
makes it all the way

around school, so-and-so
and whosie-what-sit have
already broken up.

So by the time you get
that, if you're at the end

of the chain, you have just
discovered information,

it's real information,
but it is lagging in time.

It's out of date.

And that is unavoidable
in astronomy.

And so that's why
people often will say,

"Astronomy's a little bit like
archeology in that sense."

But not really.

There is a difference.

And in astronomy, when
you're looking back in time

at something that is old
because it's far away,

it's not that we are digging
up pieces of the past

and looking at them
as they are now.

It's as though we are
actually able to look at

what really happened.

Take Pompeii, for example,
on that fateful day

when Vesuvius blew up.

It would be as though rather
than going to Pompeii now

and unearthing artifacts
from that time,

we were able to look
from a distance and watch

the life of the
city in the morning,

watch the residents go about
their day on that final day.

Now, it would not
be a very clear view

because it would be
a long ways away.

We would not have really good
images or pictures of it,

but that's what
we would be doing.

We'd actually see
it going through

and happening as it occurred.

So in that sense, it's
not like archeology.

That's the time travel
bit in my title.

But wait, there is also
an element of archeology,

in that what we
are trying to do,

and I'm going to
describe to you,

is look back in time

at distant objects and
look for artifacts.

So we are doing both.

It is time traveling
and it is archeology.

We're trying to understand
what has been happening

with galaxies and the
black holes they contain,

at times previous
to when we see them.

Why? We'll talk about that.

So, we're gonna talk

about a fair number of
things this evening.

Big ones are black
holes and galaxies.

That's what this whole
project is about.

By the way, this project, this
time traveling archeology,

this is a field report.

We're not completely done yet.
We're in the middle of it.

We've got a lot of work done.
This is an update.

This is like when you're
watching a show about archeology

on TV and they are
just starting the dig

and they're out in the jungle
and they're getting hot

and sweaty and they're
getting bitten by scorpions,

that's where we are, we're
at the scorpion-biting
phase of this.

So we're gonna talk
about black holes,

supermassive or monstrous
black holes, and galaxies.

The black holes living inside

at the centers of the galaxies,
how are they connected?

That's the fundamental
question that we're after.

And what have these
been doing in the past,

specifically the stars
that are in the galaxies?

Galaxies are made up of a
bunch of different things

that we'll talk about here
in a minute, but the stars,
what have they been doing?

And what have the black
holes been up to in the past?

We're gonna talk about
some new observations

with a big radio telescope.

You may be thinking of
the one in New Mexico.

Some people may
be aware of that.

A little farther away,
a little bit bigger.

As I mentioned, a lot of
modern science needs multiple

different approaches
all integrated together.

One of the things we're doing
are massive simulations,

theoretical work using computers
to try to understand better

what we're actually seeing
with some of these telescopes.

And also, we're utilizing
visible light surveys

of the sky as well.

So that's where we're
going this evening.

Black holes and galaxies.

I talked about that this
was gonna be a connection

between them, a story of
the connection between them.

Time traveling in the
sense of looking backward

or into the past and see how
they actually were at time.

Archeology in the sense that
we are going to be looking

at relics in the past of
yet even in earlier history

of both the galaxies
and the black holes.

But before we dig into
these connections,

let's actually talk
about, remind ourselves

what are the black holes
and what are galaxies?

On the left here,

is a series of depictions
of a black hole.

Little bit hard to
get a real picture.

This is more than an
artist's conception.

This is actually a
computer simulation

of a disk of material
around a black hole.

Anybody recognize it?

It may look vaguely familiar.

It's a simulation that went

into the Hollywood
movie Interstellar.

So that the filmmakers
there wanted to have as much

scientific accuracy
as they could

within the constraints
of the production.

So one of their major
scientific advisor,

who I understand worked
very closely with them,

is a fellow named Kip Thorne.

Kip Thorne recently won
the Nobel Prize in physics

for working on
gravity-related things.

So he knows a thing or two
about black holes and gravity.

He has literally written
some of the books on them.

He worked with their
special effects team

to make as realistic as
possible simulations.

So going down from the top here,

if anybody saw the movie,
this is closest

to what was actually
depicted in the movie.

The black hole is
here in the middle.

More specifically,
that's its event horizon.

And this material around it
is called the accretion disk.

It's material flowing
into the black hole.

This was depicted in the
movie, but more realistic

are these down here, these two.

These are progressively
more realistic.

What they put in the movie
did not have an effect

known as Doppler shifting,
which changes colors

depending on whether the
material's moving towards you

or away from you.

And there is also an
effect of relativity

that makes things moving
very fast towards you

appear brighter, over here,
and things that are moving

quickly away from
you appear dimmer.

So this is how, right
here, a bit closer

to how the black hole
would be more realistically

in appearance, but that was
thought to be a little bit,

potentially too confusing
to the audience.

I was reading about this,
interestingly enough,

in a scientific paper,
in a journal called,

Classical and Quantum Gravity ,
Kip Thorne

and the special effects
people wrote a paper,

more than one, I think, about
doing movie special effects

in Classical and
Quantum Gravity.

It's actually a
really fun paper.

And down here, finally...

This is an attempt to explain
why it looks so weird.

Anybody, when they saw
the movie, wondered

why is there material, if you've
heard of an accretion disk,

why is it above and below as
well as from side to side?

It's an effect of gravity
called gravitational lensing.

This up here is a colored disk.

It's a color swatch that
changes color radiating outward

and is the same
all the way around.

If you take this and put it
in front of the black hole,

because of the warping
of space time by gravity,

this is what you see.

So this is really just a
nice, uniform color swatch,

but see how it gets
distorted around there?

Gravitational effects through
the warping of space time.

Anyway, that's my little
introduction into black holes.

By the way, I, and it turns
out, other astronomers,

had assumed that
when we saw the movie

that this is what's called
a stellar mass black hole,

something that has
relatively, as you will see,

low mass, though it's
not low by our standards,

a few times the mass of our Sun.

And it's the product of a
large massive star dying

leads to a black hole like that.

We all assumed
that's what this is.

Well, in reading about it, Kip
Thorne actually modeled this

as what's called a
supermassive black hole.

The black hole that
was in the simulations

is 100,000,000 times
the mass of our Sun.

And I was delighted to
see that, because what I
am talking about here

are supermassive black holes,

black holes with
masses of millions

and even billions of
times the mass of the Sun.

So this is actually a very
relevant depiction of this.

So that's a bit about black
holes, supermassive ones.

They live in here, in
the middle of the galaxy.

We live in a galaxy.

If you go outside, maybe
later at night if it's clear,

get out where some lights are,
away from some of the lights,

you can see it's the Milky Way,
that's our galaxy.

This is not a picture
of the Milky Way.

Some people may recognize
this as a picture

of the Sombrero Galaxy taken
with the Hubble Space Telescope.

It's meant there as
kind of a generic

but very pretty depiction
of the galaxy, you see
some of the parts of it.

You see the fuzz there, the
lighted fuzz, those are stars.

This is an enormous
number of stars

whose light's all
blended together.

The dark plane is a disk of gas.

We have a plane
in our Milky Way.

Our Milky Way doesn't
look like this quite.

It is a different
type of galaxy,

but it does have
that disk in it,

does have that dust in it.

And then right at the center
of almost every galaxy

we know about, there is
one of these monsters.

There is one of these
supermassive black holes.

So we live in a galaxy.

There's a supermassive black
hole living in the galaxy,

almost every one.

What does that mean about us?

I can tell you.

There's somebody
in here tonight,

sitting right now, and there
is a supermassive black hole

behind you and
underneath your chair.

One of you, one of us.

Anybody getting nervous?
[laughing]

You don't have to worry.
That one person is me.

The supermassive black
hole in our galaxy

is roughly there.

It's in that direction,
still below the horizon.

It's not that long ago.

It's okay. I don't have
to worry about it.

It's a long ways away.

It takes 25,000 years for
anything to happen to get to us.

And black holes don't have
some mysterious sucking power.

They're not gonna suck
an entire galaxy in,

and things have to get
relatively close to them.

So we're gonna be
okay with that.

But if you do get
material close to them,

and that material falls
into this accretion disk,

hapless stars, unfortunate
planets that may be around them,

gas, dust, whatever
happens to get in there,

loses an enormous amount of
energy. It's falling energy.

It's just like if something
fell down, it breaks.

Imagine something falling
with so much more energy

than we can conceive
of on Earth,

and it releases some
of that before it falls

into the black
hole, that can power

a rather remarkable thing.

It's called an active
galactic nucleus.

It's the visible manifestation,
and when I say visible

I don't just mean visible light,

I mean all different kinds
of electromagnetic radiation

as we'll talk about,
it's the manifestation

of one of these supermassive
black holes consuming

material and then jetting
out some of that material

and a lot of light.

And those jets come out
at very close to the speed

of light and they can be huge.

So getting over to the
panel on the right.

Now we're putting the
two of them together.

This is an image of a
cluster of galaxies.

Each little fuzz ball in
there is its own galaxy.

It's like the Milky
Way in which we live.

Some are bigger,
some are smaller.

Those red plumes,
that's a false color.

They're not actually red.

They're representing
radio jets and lobes.

A lot of times the largest
physical manifestations

of these active galactic nuclei,

these supermassive black
holes gobbling up material,

sending up these enormous
jets at close to the speed

of light are in the radio.

I mentioned the radio
telescope earlier,

so that's where we're
going with this.

And you can see how much
bigger sometimes these are.

They can be much
larger than the galaxy.

They can be a substantial
fraction of the size

of a cluster of galaxies,
like is in this case.

So now, what might
be the connection?

That's where our
story's leading.

It's the connection between
black holes and galaxies.

Again, it's a time travel
story because we're looking

at things that are distant,
and hence back in time.

It's an archeological
story because we're looking

at relics back in time
to try to understand

what has happened earlier
and earlier in time.

And what we're trying
to understand is
how the black holes

and the stars in the
galaxies might be connected

with each other.

This is why we're
thinking about this,

because there is growing
evidence that there is

a very fundamental connection.

The work on the
left is not ours.

It's a published paper.
The citation right there.

But it's showing a
cluster of galaxies.

Again, the light fuzz balls
are individual galaxies.

The blue is an X-ray image.

We don't see X-rays, but we
have to represent it somehow,

so it's a false color image.
The X-rays are blue.

Again, the radio's in red.

You see those
large radio plumes.

If you look closely,
the radio plumes

appear to be in areas where
there's not many X-rays.

The X-rays are tracing the
hot gas around these galaxies

around this cluster.

The radio plumes
driven by this AGN

or active galactic nucleus
have driven out this material.

There's a term called feedback.

This is something that
people have been getting more

and more interested in, not
only because of observational

evidence like this,
but theoretical evidence.

Folks who have been
getting better and better

at modeling how galaxies form,

they basically create an entire
universe inside a computer.

They create gas, primordial gas,

add dark matter,
this mysterious stuff.

We really don't know what it is.

And watch what happens.

And gravity will cause the gas
and dark matter to collapse,

which will form galaxies,
stars, et cetera.

They've gotten better
and better and better at
this across my career.

It's actually been remarkable at
how much progress they've made.

But there was a problem.

Stars formed too quickly,
more than people see.

Too many stars faster than we
actually see in real galaxies.

What to do about this?

There had to be some way of
suppressing that star formation,

some kind of feedback
mechanism that as gas flowed

into the galaxies would
then puff it back up again.

Two main candidates for
that, the stars themselves.

Some stars explode, huge
explosion, super nova,

they blow the gas
back out or heat it.

The other one's these,
the active nucleus.

The material flows in,
it can light up the black hole,

turn on the active galactic
nucleus, puff out the material,

shut itself off, and maybe
shut off the star formation

in the galaxy.

This is where we're going.
It's that connection.

People have been working on
this to try to understand

this better and better.

It's probably a fundamental link

between the supermassive
black holes at the center

of galaxies and the stars
in the galaxies around them.

The specific question
we're trying to address

is time scale.

Is there any connection with
when a supermassive black hole

became active,
like is shown here,

and any star formation events,

the history of the formation
of stars in the galaxy.

Is there any connection between.

This would indicate
there would be.

The theoretical work
indicate there would be.

But what's the timing?

Does the AGN turn the active
galactic nucleus on first,

same time, afterwards?

How are they relative
to each other?

Is there always a connection,

or is there really no
connection in timing?

Is it maybe just a
little bit that happens

below what we can detect?

So these are the
type of questions

that we're trying to answer.

So if we're trying to
see a connection in time

between what the
black hole is doing

and what the stars in
the galaxy are doing,

we can't just look at

a galaxy and a black
hole at the same time.

Well, you can.
People have done that.

That's done a lot.
But you're limited.

You're looking at a snap
shot in time, one time.

Remember, you're looking
at Pompeii that morning.

You're not seeing
what had happened

500 years earlier in Pompeii.

For that, you need to
go back to that morning

in the early 80's and
go dig up something.

That's the time
traveling archeology,

and that's what we're
trying to do here,

is go dig up things and see
if we can make a connection

in that time scale.

And the plot on the left
here is just a schematic.

The thing in the middle
that looks like a sun

is actually meant to represent
an active galactic nucleus.

That's a supermassive
black hole.

Over here,

on the right part of
that, is the outflow.

And it may even
trigger star formation.

So the idea, the main idea
people are thinking about now

is that these active
galactic nuclei may shut off

star formation, but they
may also trigger it.

That's an idea that's
been around a long time.

I remember hearing about
that in graduate school.

So there may be a
lot going on here.

And this is the question
I was addressing just here.

What is the time scale here?

So to do this,
we need a couple things.

This is the archeology again.

We need to be able to trace a
black hole's activity history.

What has it been
up to in the past?

Was it active in the past,
or was it just sitting there?

Remember, it's only
active if you have
material flowing into it.

That accretion disk, if
it runs out of material,

it just sits there.

Also, we need to be able

to trace the galaxy's
star formation history.

What were the stars doing?
Do we see a connection?

Was there an episode of
activity in the black hole

in the past that then shut
off the star formation,

that then triggered
the star formation?

Did the star
formation happen first

and then trigger the
black hole or shut it off?

How do these things
connect with each other?

That's what we're
trying to get at here.

And we can do that with
a black hole, at least,

the active galactic
nucleus, we can do that

if we look at them
with radio light.

Remember, I said those huge
plumes were radio emission,

particularly at low frequency.

And we need to be able
to trace the galaxy's

star formation history,
and we can do that

with visible light observations.

That's the story
of this evening,

the rest of the evening here.

So getting to how we
figure out what the stars

have been up to, this
is a very brief rundown

of a rather complicated topic.

But the principles are okay.

Over here on the left

is something called a
Hertzsprung-Russell diagram

or a color magnitude diagram.

We don't need to worry about
the terminology too much.

It's a plot.
This is color.

They've nicely color-coded it.

This end is red.
That end is blue.

So it's color, blue to red,
and up here is brightness.

This is fainter,
that's brighter,

and these represent stars.

This is the culmination
of decades of work,

particularly in the first
half of the 20th century,

to understand, to not
only measure these things

but understand how
this changes with time.

And what happens is that
when a bunch of new stars

are first born, they
lie all along here.

This is called
the main sequence.

And the more massive ones,
the ones that turn out

the more massive ones, are
brighter and they're bluer.

They gobble up their fuel, even
though they have more of it,

they are real hogs.

They gobble up very
quickly, and they expire.

The star dies.

And so from here,

they would move off to
this other part here.

This is not a talk
about stellar evolution,

just suffice it to say
that they go over here

and then they loop
around over here

and they eventually peter out.

The point is that the older
the group of stars are,

the more, whoops.

Back that up a bit,
hit the wrong button.

The more they moved off of
here to get down to this,

so you can tell the age of
a group of stars this way.

And this allows you to then
connect age of lots of stars

and how the galaxy in
which they live appears.

And this is it over here.

So if we have very young stars,
a very young group of stars,

that's these blue
ones over here.

Remember, the young
ones live up in here.

Very bright, very blue, so
they dominate the light,

they can dominate the light
of the whole group of stars

and even the galaxy.

So this is what's called
a stellar population.

Each of these graphs is
a stellar population.

What it means here is this is
brightness, again, vertical.

And this is color,
specifically wavelength.

So this is blue, what our
eyes would see as blue,

red, near infrared.

And even though
these are each coded

by the same color
all the way through,

it doesn't mean they're
all the same color.

It's just that this
one is colored blue

because it's more
dominantly blue.

It's got more light
up in the blue

than it does over
here in the red.

And this is an age sequence.

Young,

old,
really old.

You can see what happens.

This plot of light,
this is like a rainbow.

It's a spectrum.

By the way, these tags up
here, this is showing us

what kind of the key
ideas here in each figure

and this is where we are
in the plot, roughly,

just kind of a guide,
because this can be

a little bit complicated.

So if you're ever not
sure, or you wake up

and you say, "Where
is that guy?"

That's where we are.
Just look at the top there.

So this is the appearance
of a collection of stars

of a single age.

And a galaxy is made up
of collections of stars

of different ages.

And so we can combine
these together.

Principle is we can combine
these together and form

the rainbow or the spectrum
of an entire galaxy

made up of components of these.

If you can combine
them together to see

what a galaxy looks like,
you can also take them apart.

That's the key, we can take
a spectrum of a galaxy,

or pieces of a galaxy,
and pull it apart

into these constituent
pieces and understand,

in principle, how old
each of the pieces were.

So that is the
stellar archeology.

That's figuring out the past
history of the star formation

in any galaxy for which we
have sufficiently good data

and a good enough understanding
of what we're doing,

which is a key that's
still being worked on.

Most of our project today,

like I said, this
is a field report.

We're still in the scorpion
biting, bug stinging,

digging around in the jungle
phase of the archeology.

Most of what we've
done so far has been

on the other part, the radio.

I'll come back to
the stars in a bit.

This is the AGN.

This thing here is
also a spectrum.

This is a rainbow,
just like a rainbow,

rainbow when you see it outside,
it's a spectrum.

It's breaking the light up
into its constituent colors,

but this is a radio one.

What's up here at the top are
frequencies and megahertz.

150 megahertz on the
left, 1,400 on the right.

Now, that may be
coming out of the blue.

Red and blue colors,
we're used to.

150 megahertz,
well, what's that?

So I gave a few
guidelines up here.

I've listed a few things we
might be somewhat familiar with,

very high frequency TV,
the high band of it,

is roughly where it's
indicated up there.

The UHF channels of
TV are over there.

And underneath of it, I
got merged in a little bit

with the labeling
there, cell phones.

And AM is lower frequency,
so off to the left,

and Sirius XM radio is higher
frequency, so off to the right.

So that kind of gives us an
idea of where we are here.

And I've plotted spectra

of the radio source.

It looks a lot simpler.

So this is similar to, it's
the same type of thing,

a plot of brightness
of light with color

as we had before, but this
one looks a lot simpler,

thankfully, because that
one's really complicated.

And again, there's
a sequence of age.

The blue one here is
for a radio source

that's 10,000,000 years old.

What you see happening here
is that as you go older,

the key is down there
in the lower right,

as you go older from 10,000,000
years to 50,000,000 years

to 100,000,000 years, by
the way, MYR is mega year,

million years old, to
300,000,000 years old.

Look at the corresponding
colored lines.

The young ones are shallow
and go straight across.

As they progressively get
older, they get steeper

and there's a turnover there.

So those are two things
we're gonna see here more of

as we go forward, how
steep that line is.

Is it shallow?
That indicates pretty young.

Or is it steep?
That indicates older.

And also, the location of where

these turnovers have
happened, like this one.

This one is
300,000,000 years old.

Notice how quickly it's
turning over like that.

So we're gonna talk
about that more.

The steepness of the
spectrum, the radio spectrum,

and the turnover point,
the frequency at which
it turns over.

This, then, is also a clock.

Like what we had for the stars,

this is a clock for
the active galaxies.

So we can get some idea
of how old they are,

and even look for relics,

again, the
archeological reference.

We are looking for not only
currently active galaxies,

but ones that may have
been active in the past.

And this is a way to do that

because you can see
something that was active

a long time ago,
300,000,000 years ago,

we can still see it, even if
it's no longer active today,

with the right kind
of observations.

And that means lower radio
frequencies, 300 megahertz,

150 megahertz, are considered
low frequency in the radio.

So getting there.

At the beginning,
remember, I mentioned there

would be a radio
telescope in here,

but it's not the
one in New Mexico.

The one in New Mexico is
called the Very Large Array.

It's been in a lot of
commercials, movies,

the movie Contact, for example.

You can tell I'm a
bit of a movie buff,

especially when it comes to
astronomical-themed things.

This is a telescope that's
actually even bigger

than the one in New Mexico.

More dishes, the dishes
are larger themselves.

And this picture here
is just a subset of it.

This is only a tiny
part of the array.

If you look carefully,
the one in the foreground,

the biggest dish, is next
to a little white blob.

That little white
blob is a Jeep.

These dishes are
45 meters across.

This is near Pune, India.

It's called the Giant
Metrewave Radio Telescope,

GMRT there stands for Giant
Metrewave Radio Telescope.

Metrewaves, it's the
wavelength of the radio waves.

These things will go, this
will observe wavelengths,

the shortest one
is about that big.

The longest one is
taller than Darth Vader.

That's why they say
metrewave, it's in the meters.

Longer wavelengths
corresponds to low frequency.

So those are the same thing.

It's a radio interferometer.

We could have a whole talk
about radio interferometers.

They're wonderful
things that allows you

to use many dishes, many
radio dishes, to work as one.

Gives you the clarity of image

that you would have close to it

if you had a single

gigantic radio dish

that was as big as
the entire array.

So these things are spread
out over 10's of kilometers

all across this plane in India.

And they work together and
they can give you an image

that is approaching as crisp

as if you had a giant
bowl that was 10's

of kilometers across all
collecting radio length.

That's why they're really neat.
That's why people use them.

And over here on the
right is an example

of observations of
one of our objects.

This is a radio
galaxy, similar to ones

that I showed earlier,
not quite as big.

And all the alphabet,
don't worry about the
alphabet soup up there.

Those are different
surveys, we've drawn
these from our surveys.

The SS in all these things
stands for sky survey.

So SDSS is a sky survey.
TGSS is a sky survey.

WINSS is a sky survey.

And then I've indicated a
couple points of new data.

These are some of
the data we've taken

and are currently working on.

We just finished the second
of three observing runs.

The next one will be
coming up next month,

and then we will have
all the data we need,

hopefully for one of the
graduate student's PhD theses.

And so we'll have a lot
more of this coming in.

All right.

Here's just a quick example.

This is some early results.

I've plotted three
things up here.

Remember I said that
one of the key things

is a spectrums shape, this
is an indication of shape.

Don't worry about what
the color bar means here.

The key thing is this.
This is the age.

This is the derived
product from the spectrum.

That is

100,000,000 years right there.

Green blue is 200,000,000 years.

And so this thing looks like
it's actually relatively young.

It's around 50,000,000 years
old, look at the color there.

Now, a key component of any
type of scientific research

is not only can I put a number,

but understanding how
precise that number is.

Is it a good number?
Is it a usable number?

To what degree is it
good, is it usable?

That comes with precision or
understanding the uncertainty.

And so this one over
here on the right

is a ratio of the
age we determined

divided by how
uncertain we think it is.

And those numbers are a
little bit hard to see,

but they range to
about 10 to 20 there.

So it's 10 to 20, the
age is 10 to 20 times

what the precision of it
is, which is not too bad.

We could do a little bit better.

But that is just the
so-called random uncertainty.

That's if everything
else was just fine,

just due to the nature of
the random fluctuations

in the data you get,
how good the data are,

but there are more than
random fluctuations.

There are also
systematic uncertainties.

And I'm gonna make a brief
but kinda big deal about this.

I'm gonna put it up
here, systematic errors,

'cause this is important,
not just in astronomy,

but in any time we're dealing
with any type of data,

any type of information.

It's not only the
basic precision of it,

but also how well--
what are your assumptions

and how well do you
know your assumptions?

For example, polling data
is a commonly-used analogy.

You'll see an error bar
quoted on most polls.

That's 35% of people like this

and 70% of people like that,

put an error bar plus
or minus 2% or 3%

is often what you hear.

But that's only the full story

if it's been a
careful representative
sample of the people.

If they only call
up a group of people

who have a particular
connection with each other,

they may get very different,
very skewed and biased results.

And that's what we're
trying to understand here.

The basic techniques I outlined,

the plot of those simple
radio spectra, are great,

but they sweep a lotta
things under the carpet.

It's not that anybody's
been hiding anything.

It's just this is something
that was developed 50 years ago.

It's a beautiful piece of work,

but the real things
are so complicated

that you have to make
certain assumptions

that we know are
not valid in nature.

The question is, how
invalid are they?

What will they do?

What do these assumptions
do that we've made?

And so this is where the
numerical simulations

I was talking about
come into play.

We are

using computer models,

basically creating these
AGN inside of a computer,

letting them age, and
seeing what happens to them.

And remember, I told you
earlier that we would be talking

about a couple things here:
one is the turnover frequency.

That's what this is.
This is 100 megahertz.

1,000 megahertz, so this is
the range we're observing.

This is 10 gigahertz.

You'd have to go to the
VLA in New Mexico to see that.

This is a snapshot in time.
This one's 10,000,000 years old.

This one's 40,000,000 years old.
Again, this is the simulation.

So we're looking at it
at a particular time.

If everything were simple,

as that basic
model was assuming,

this should all
have the same color,

should all have the same
color frequency. It doesn't.

Some of this is
very high frequency.

Some of this is
very low frequency.

That tells us that
there's a lot going on.

It's not that we
didn't know this,

but we're trying to
better understand this.

And over here is a measure
of the shape of the spectrum.

Again, the key thing
is to look at the range

of colors across this.

These are just
snapshots in time.

I have a movie.

This is kind of fun.

It's a different color
scale because we're still,

this is still very much
work under development,

and Yi-Hao, the graduate
student who's working

on this changed the color scale.
He likes this one better.

I think it's kinda fun.
We're watching time move here.

This is the jet.
This is inside a simulation.

You're seeing the jet.

The black hole is where that
yellow stuff is spouting out.

And again, the
color coding here is

that frequency where
the spectrum turns over.

The deep purple is
below 100 megahertz,

very low frequency,
lower than we can see.

And the blue is up
at 10 gigahertz.

I mean, the yellow's
up at 10 gigahertz.

So what you're seeing is an
evolution of the spectrum

of the radio source in time.

Can't show it all at once,
it'd just be too confusing.

I mean, as it is, we're
looking at a three-dimensional

model here in
two-dimensional space.

The point is, you're watching
it age before your very eyes.

What the color coding here
represents how it would look

to us if we observed it
in a radio telescope.

So what we're trying
to do is understand,

better understand what
the data we're getting out

of this radio telescope
in India actually mean.

And it's going out to

350,000,000 years, it goes
out to 500,000,000 years.

So this is a simulation
over half a billion years

of cosmic time.

And we're trying to
use this to inform,

let's play it one
more time real quick.

There it is again.
There's the jet.

That's the galaxy, the active
nucleus is very active.

The black hole's running.
We're at 3,000,000 years.

It goes slowly at first
and then shuts off.

I think they shut
off the black hole

at about 10,000,000 years
and then they speed up

because we would
be here all night

if we watched it at this pace.

It's 8,000,000 years.

So you see that the
yellow, there it goes,

the black hole just shut off.
The active nucleus shut off.

Now it's passively evolving.

So if we were to observe a real
galaxy that was like this,

this would be the relic,
this would be the artifact.

This would be what we dug up
as the cosmic archeologists,

that thing right there.

A snapshot in time,
that we, unfortunately,

we can't see that in real life.

It's only in the
simulation that we're able

to see that movie.

But we're trying to use
these simulations to inform

what it is we are actually
seeing in real life.

So the trick is to
take the observations

that we're making with these
radio telescopes and say,

"All right, well,
what is the best match?

"What timing here
does it best match

"and how well can
we determine that?"

So that's where a lotta the
work is going on right now.

And this is what I was
just talking about.

What if we pretend the
simulations are real?

And what I mean by
that is we can take--

Those simulations have an
enormous amount of information.

You saw there's information
about the shape of the spectrum,

information about the
slope of the spectrum,

information about time,
we have brightness of it.

We have all these
different qualities.

We know what the
pressure of the gas is.

We know what the
magnetic fields are,

far more than we know in
an actual, real observation.

So to really try to make
progress in understanding

what it can tell us, we have
to look at these simulations

as though we were
actually making a

real observation.

And that's what these
are representing.

So there are three
simulations here.

The 10,000,000 years, this one.

50,000,000 years, these
are snapshots in time

of the simulation you saw.

100,000,000 years.

By the way, note the
different size scale.

It looks smaller,

yet you saw it was
getting bigger with time.

That's just because it
got too big to fit on here

so I changed the size
scale to fit it on there.

So I'm just alerting
people of that.

Up here, this is an indication
of that spectral shape,

but let's go down here
and look at the age.

And it's a little difficult
to see it scale on here

with this large view.

But this is, if we
looked at a region

of this radio source
using the basic techniques

I talked about when we
first introduced them,

when I introduced those
simple radio spectra,

this is how old it
would tell us it is.

So it would say that colors
down here in this region

are 8,000,000 years old.

Colors out here are
22,000,000 years.

The actual simulation
age, that's the nice
thing about this.

We know exactly how old
this is because it's made up

and we can test it,
is 10,000,000 years.

So it doesn't do
too bad of a job,

but here is one of the reasons

why we are doing these
simulations. Look at this.

You saw this in the movie
and some of the stills I did.

This is a very different color.

So 10,000,000 years
is around here,

so this should all
be that blue color,

but a lot of it is not.

A lot of it looks much older.

And we think we
understand why that is.

There are very good
reasons for it.

It's losing energy to
blowing material around,

a lot of other
things are going on,

but that's what we're
trying to understand.

And then out here, this should
be 50,000,000 years old.

That's way off the scale, so
this time snapshot looks older.

All of it looks older
than it really is

in the simulation.

This one's not so bad.

This should be
100,000,000 years old.

Most of it's that blue color.

The point of this is
that by doing this,

we can better understand
how good our deductions are

about what we're learning,
and ultimately be able

to make corrections for that.

So that's where we're
going with this.

All right. So where
do we go from here?

So we've made quite a
bit of progress already.

You can see the
simulations are underway.

Surveying of the
radio is almost done.

We're still working on doing
the radio data reduction,

whoops, back up.

That's what this is over here.

It's gonna be a little hard
probably to see from the back,

but these are two images
of the same thing,

just showing the progress
we're slowly making.

This is a brand new telescope.

Nobody really knows exactly how
to reduce the data from it yet.

Even the people who built
it are still learning it,
and so are we.

And there's a bit of
an improvement, if you
squint your eyes.

We measured it. There's
some banding in the left
panel here of this.

That is, there's some banding in
here that's disappeared there.

So we're busy trying to
figure that out, finish
the observations,

and then later on go
observe more of these.

After all this time, three
observing runs a year

working on this, we've
observed 40, which is a lot.

But there are a lot more to go.

And then I talked about
these simulations.

I just showed you
one simulation.

We learned a lot by doing that.

We're gonna do more.

For one thing, and
it's gonna be done

on this thing called
XSEDE, which is the

Extreme Science and Engineering
Discovery Environment.

I'm glad they
shortened it to XSEDE.

It's an NSF funded thing again.

Again, the NSF is
supporting science of a lot

of different fields with
this, and we've been awarded

3,000,000 core hours so far.

That sounds like a lot to me.
I don't work in this normally.

Sebastian, he had to do this.

So that sounded
impressive to me.

And it is.

It would take centuries
on this laptop to do this.

And on this supercomputer,
we're gonna run it in a month.

So 3,000,000 core
hours for that.

And we're going to change the
parameters of the material

into which these AGN jets go,

how they make those
jets and lobes,

to better match the actual
galaxies that we're observing.

We're gonna change
the range of power

of the jet coming out of there.

Everything I showed you

was a great starting point,
but it's one simulation.

So we're now gonna do a grid
of nine in this next one

and better learn how
these parameters affect

the results and what they
mean for our interpretation

of how old our
own real data are,

'cause that's what
we're gonna do.

We're gonna try to measure
how old these simulations are

when we know how old they are,

and then learn how we
can better determine

the ages of our real AGN so
we can connect those together.

And I haven't talked
too much about the stars

since I first did the intro,

because we've been
mostly focusing

on the active galactic nuclei
and the radio observation.

But we have a lot of neat stuff

to look at those
stellar populations,

to disentangle the
different ages of the stars

and build up the history
of star formation

across the entire galaxy.

And UW-Madison is
a major partner in

something that's really cool.

The specific survey
is called MaNGA,

stands for Mapping
of Nearby Galaxies.

I bet they made the
acronym up first

because the guy leading
this at the time

was living and working in Japan.

So he thought, "Ah-ha,

"that's a good name for it."

It's part of something called
the Sloan Digital Sky Survey.

If you haven't heard of
that, keep an eye out for it.

It's been, I would say, one
of the most important surveys

of the sky that
humans have done.

It's been going on for
close to 20 years now.

It's done with a rather
modest-looking telescope.

That's it in the lower left.
It's a weird thing.

I've never been out there, I've
seen plenty of pictures of it,

but there's this
enclosure around it.

It looks like it's a cannon
with those pedals up there.

That's actually the
opening of the light paths.

So the light goes in down
that tube and all the
detectors are down there.

It's not that big of a
telescope by modern standards.

It's about 2 1/2 meters,
but it is dedicated.

First it was dedicated
to taking the images

of a major swath of the sky.

Those are all publicly
available, anybody can
go get that.

Since then, it's been dedicated
to more specific activities,

a series of survey projects.

We're now in the fourth
generation of this,

working on the fifth.

And UW's heavily involved
in both of those.

The project scientist for
all of this fourth generation

of Sloan is one of our faculty.

He's back right
next door to Marsha,

who's the PI of our project,
so he's in our building.

And we are also heavily
involved in designing

one of the major projects for
the next generation of this.

But on to this,
this MaNGA survey

has been solving a problem
that has bedeviled astronomers

who are doing things
like I'm trying to do,

like our group is trying
to do, for a long time,

in that a lot of what
we observe in galaxies

with visible light is either
from one part of the galaxy,

like the middle,
or it's a swath,

a cut,
through the galaxy,

because of the nature of the
instruments that are used.

There are instruments
that use optical fibers,

similar to what's in
telecommunication.

Optical fibers are light pipes.

Hold up an optical fiber,
whatever light comes in.

Goes down a pipe. You can
bend them. Really cool.

Move the light, and
it is a light pipe.

You can take the light
from where it comes in

from the telescope,
bend it around corners,

go down somewhere else, and
run it into an instrument

like a spectrograph
that makes the rainbow.

So what MaNGA's
doing, and again,

this isn't the first time
people have done this,

but this is done
on a massive scale.

They're putting a whole bunch of
these optical fibers together,

and the graphic on the right
is meant to represent that.

You can see the hands in there
are holding one of these things.

These are small, little devices.

That cylinder that
that person is holding

contains dozens, it
depends on which one,

we have different kinds of
up to close to 130 fibers,

so dozens to over
100 of these fibers.

If you look in the lower
right corner there,

right here, this is a
close-up of the top of that

with a little graphic done.

This is showing an
overlay of a galaxy.

The idea is, here,
you get the telescope,

make a picture of
the galaxy here.

And every one of
these little spots

is one of these optical fibers.

And it will take the light
from each spot of the galaxy

and run it into the instrument,
to the spectrograph,

and make a spectrum for us.

That allows us to look at
these stellar populations

and other things about it
across the entire galaxy,

not just at the center.

So this is a really
important new development

and this is basically
the second half

of the archeological dig,
which we started on,

but haven't gotten very far yet

'cause we've been focusing on
the simulations and the radio.

And this is just
a quick example,

I'm gonna run through
this very quickly,

of what this MaNGA can do.

This is putting
everything together.

So here is, in the image
down here in the lower left,

of a rather
nondescript-looking galaxy.

This is from the original
Sloan sky survey,

the one that took pictures.

This is a compendium
of radio maps.

This is an overlay.
There's the galaxy right there.

You can see it looks much
more interesting in the radio.

These are those jets
and plumes going out.

These are three
different surveys

at two different frequencies,
three different surveys.

This is not our data.
These are existing ones,

but showing some of the
complexity in there.

This is what we're trying
to measure to determine
the age of the AGN.

And this is a result of
the MaNGA data product.

This is looking at
actually ionized gas,

which is a little bit different
from what I was telling you

about in figuring out
the histories of stars,

but it's important for
understanding what's
going on right now.

So this will tell you about
current star formation

and also what the active
nucleus is doing as well

as looking at the radio.

And you can see here, I'm
not gonna go into the details

of this, but you
get in the past,

we might get something from
just one part of the galaxy,

or a slit here.

Now we're able to see
across the entire galaxy.

This is plotting
where the ionized,

where we think is
causing the ionized gas,

whether it's new star formation,

so it tells us about
star formation,

or whether it's
the active nucleus.

So that's just the
tip of the iceberg

of what we're getting out
of this MaNGA project.

All right.

To wrap up here, we've
talked about a lot.

It's a complicated project.

It's a fun project, but there
are a lotta pieces to it.

So let's just review it briefly.

And I'm going back to my little
shtick from the beginning,

my silly little title for
here, the time travel.

Again, that is--

It's not technically
time travel,

what we're talking about,
but it is an element of that.

That's what I said
at the beginning.

This title has a
grain of truth to it.

It's a time travel in
the sense that by looking

at objects that are far away,

we are not seeing
relics of them.

We are seeing them

as they were early in
time, earlier in time.

That's the analogy with
actually being able

to watch the residents of
Pompeii on that fateful morning.

That's the time
travel aspect of it.

We are also doing archeology.

That's looking into the
relics of past events

in the histories of the
galaxies, their stars,

their star formation history,

and what the supermassive
black holes have been up to.

That's pretty tricky.

We can do it if the
supermassive black holes

have been active and pumped
out all of this hot gas,

this plasma, that is
emitting radio light.

The spectrum, the
rainbow of radio light,

encodes the history

of what that supermassive
black hole's been doing.

It's up to us to figure
out how to do it.

So the time traveling
archeology aspect

is we're looking at
galaxies as they were,

but also at artifacts back then

of even earlier epics
to try to figure out,

the ultimate goal is to try
to figure out this timing

between star formation
and the activity

of the supermassive
black hole to see

if we can really get
some deep insight

into what people
think is going on,

this deep connection
of how the activity

of the supermassive
black hole and the stars

in the galaxies are intimately
connected to each other.

So it's part of that
larger ongoing story.

And the final theme here, is
lots of tools coming together.

That's what made this kind
of a complex talk in a way,

but also a fun, fun project,

because we're using the
state-of-the-art surveys.

I only briefly alluded
to the radio ones,

but there's several of those,
making good use of those.

I talked about the MaNGA survey.

We're using visible light.

That's how we're
getting at the stars.

We're using radio light.

That's how we're getting
primarily at the active nucleus.

And we're tying it all
together with simulations

of the stars, and we talked
a little bit about that.

But I alluded to it
back in the beginning

when we're trying to
disentangle what the spectrum,

what the rainbow of
light of the galaxy was

in terms of how it was
put together in the past.

When did the stars
form to do that?

That's a modeling exercise.

And also, simulations of the
jets and these big balloons,

these lobes, of the
radio galaxies to try

to better understand
what we're learning,

what we think we're learning,
about the ages of them.

Thanks so much, appreciate it.

[applause]