A New Tool to Map Entire Galaxies


>>Hello all. Oh, great. Well, I’m glad to
see you all here. I’m Dr. Jake Hartman, and
welcome, all, to our second talk of the Carnegie at PCC series. I’m very much looking forward to it [laughter]
[applause], thank you. Just a few points. First off, of course, please
do silence your phones for the duration, if you
have not already done that. I want to give a quick
thank you to some of our student volunteers
who were a great help in getting the word out,
hanging posters, and generally, directing people to Creveling
Building which, it seems, that not that many people on
campus know where it is so, thank you to the Astronomy
Club and Geology Club for helping out with that. And I also want to give an
advertisement for the third and final talk of this series
this semester, that will be on November 20, also Wednesday. Same time, same place,
6:30 in Creveling. And that will be Allison Strong
[phonetic] also of Carnegie who will be talking about
the DNA of galaxies. So, I encourage you all to
come to that third series in our semester of talks. And, of course, bring
family and friends. Tonight, I am very happy to be
welcoming Dr. Rosalie McGurk who is Carnegie Post
Doc of Instrumentation. She’s been with Carnegie since
about 2017 working on some of the work that she’ll be
talking about this evening. Before that, she was at the Max
Planck Institute in Germany, also doing some instrumentation. And, before that, got
her PhD at University of California Santa Cruz where she studied
active galactic nuclei.>>Active black holes.>>Active black holes,
absolutely, the particularly hungry ones,
they’re still eating all of the stuff around them. Maybe we’ll hear a little
black hole stuff tonight.>>A little.>>All right, wonderful. Everyone likes that. And, yeah, so, I’m particularly
excited about this because, when we think about astronomy, we think about, you
know, the facts. We think about the black holes,
we think about the planets, we think about the galaxies. But we don’t often think about,
well, how do we know that? Will, how do we get
that information? We’re privileged to be in
the same town, Pasadena, awesome astronomy town as
Carnegie which is building some of the world’s largest
telescopes which ultimately
answer these questions. And a telescope is not just some
giant bucket collecting light raining down from the sky,
though that’s part of it. And it’s not just a bunch of
mirrors and possibly lenses that focus that light,
though that is part as well. Really, at the heart of the
telescope is the instrument that interprets that light,
that make sense of that light. And really gives you the data
that tells us about those stars or black holes or galaxies. And I think that that’s
probably the hardest part, interpreting all
of those photons, all that light that’s coming in. So, I am very excited to hear
about your work on this subject. Thank you, again,
Doctor Rosalie McGurk.>>Thank you so much [applause]. Thank you [applause]. Excellent. Thanks, Jake, for
the introduction. Can you guys hear me,
mostly in the back? Okay, great. And if I start being
too loud, do let me know because I’ll get
excited while I’m talking about this and I get louder. It’s not a surprise. Anyway, so, I’m going
to talk about a new tool to map entire galaxies. So, what do I mean by that? So, first I’ll talk about an
introduction to spectroscopy, then it will talk about the
different types of spectroscopy, long slit versus integral
field spectroscopy and I promise actually
defined with those mean. Then I’ll tell you about my
instrument and the science that it will be able to do. So let’s jump right in. So, you all are here
because you’re interested in astronomy and, maybe,
also some other sciences. And I’d like to tell you
all the other sciences, at least theoretically, have
it easier than astronomers because a lot of
scientists can go out and touch what they’re
studying, or at least observe it on a reasonable scale. We mostly get light
from our sources. So, that’s good, nice
start, just like. So, light’s pretty,
pretty good though because we can do a lot with it. We had to to make the
best of what we can do, to learn as much as we can. So, when we’re talking
about getting the light, we will take that
incoming light. I’m going to wave my
hands mostly at this one, unless people think I
should point that one too. We take the incoming
light and then we send it to some type of telescope. And does anyone recognize
the silhouette of this one?>>Hubble.>>It’s Hubble, okay. So, we’ve got some astronomers,
or people who know silhouettes, one of the two [laughter]. But the classic telescope is
made up of a primary mirror, and I’m going to say this, astronomers are not
creative in naming things. It’s the primary mirror because
it’s the first mirror the light hits, not creative. So, it’s the primary mirror, it
bounces to the secondary mirror because it’s the second
mirror the light, yeah. Anyway, so, and then it bounces
to some sort of instrument that will receive the
light and maybe do stuff to it and then record it. Okay, it was a nice, broad idea. One of our favorite things to
do with light is to disperse it. White light is made
up of all the colors of the visible spectrum,
and passing the light through a prism separates it or disperses it into
all the colors. And Pink Floyd is
really fantastic for letting everyone know
exactly this picture so, thank you Pink Floyd. You all know that’s
how it works. So, you put some sort of
dispersive element into the beam and it will spread the light out into the component
colors or wavelengths. I’ll probably forget to say
colors and use wavelengths for the rest of the talk
because it’s science talk. And nature is already
really an expert at dispersing the light
into all the colors. Rainbows are everywhere,
and the light on water droplets are really
good at spreading them, spreading the light out. But, talking about it in
a more scientific context, we’ll take some source
of light, in this case, will talk about white
light first. We don’t want to look at the
entire source, we want to look at just a very narrow
portion of the light. So, will put a mask
in front of it. In this case, it’s sort of a
long slit mask, it’s a slit. Then we have a dispersing
element, in this case, beautiful prism. And, when you put the
white light through, you’ll get that continuous
spectrum out or a rainbow. And that’s useful
because, for example, at the core of our
star, we were able to disperse just the light
coming from the core, we would get a continuous
spectrum. That’s awesome. What else can we do? So, if you have heated
gas, and you try to take, try to disperse it out. So, one type of atomic
gas is right there, and it’s hot so, it’s glowing. When you disperse it
out, you get bright lines that characterize the gas and
this has a more common form that we see a lot here on
earth, they’re neon tubes. They’re neon signs, which can
actually be you get all the colors by having different types
of gas in it, in those tubes. So, by heating the gas or
running electricity through it, which is the same thing, we can
get it to glow a bright color and then, by dispersing
that tube, we can get those component lines
that make up that glowing light. And to be a little scientific,
these are emission lines, specifically, the gas
is hot and glowing so, all of its electrons
are pretty darn excited. So, if they were going to be on
an energy scale, they would be on the high end of
the energy scale. A lot like this child who
has had far too much sugar. And then, eventually, the gas
will cool and it will emit, it will, come on,
you’re supposed to. There. It will emit a photon and
it will release, it will release that light at a specific
energy so, like this child, now that they’ve finally spent
all of their energy, now, the gas is in a lower excited
state, or the child is asleep. So, that’s how we
get a mission lines. You take hot gas and
it will limit photons to try to cool down. Similarly, if you take that
same gas but it’s cooler now, and you put it in
front of a light source such as a white light
source, and you disperse it, you’ll see lines again but,
they’re dark this time. And they’re in front of, they’re
on top of a continuous spectrum from the white light source. So, the idea is, if you’ve got
something, a cool gas in front of something that’s
hot, the gas might try to grab some photons
that it likes. So, in this case, you’ve
got electrons that are sort of at a lower energy and,
if you can get a photon of the right energy or the right
wavelength, it will jump to a, and like a sleeping child, it
will grab that photon and jump to a higher energy level
and be higher, more excited. And so that means, if you
were just flooding the area with rainbows and one gas was
grabbing out certain wavelengths that were its favorite, it’d leave a dark patch,
a trough in the line. So, that’s how you get
your absorption lines because the gas absorbed
those particular wavelengths, like this child. Far too much sugar. But a little more specifically,
so, we talked about the core of the sun having a
continuous spectrum. From earth, we never see
that continuous spectrum. What we actually see is
an absorbed spectrum, and that’s because the sun
has cooler outer layers made up of multiple types of gases that are busy absorbing all the
wavelengths that it would prefer out of that continuous spectrum. So, you get lines missing. And so, this is, you
know, a small version. This is the much more
beautiful version of that, and you can see how many
absorption lines there are. There are zillions of them,
to use a scientific phrase, with some of them being larger
and some of them being fainter. And the reason we get so many
lines is each element has a really unique atomic
structure, as you’ve learned in all your science classes. Whether it’s carbon with its six
protons, neutrons, and electrons or sodium with more than
I’m counting right now. They have unique structures which means they have a unique
set of colors that they prefer to absorb light from or
emit light in, either way. So, carbon, for example, has
so many more emission lines than sodium which
only has a few. And it’s really, you can
think of it as being similar to barcodes, they’re
unique identifiers to show us what these
objects are. And so, really, we’re
always trying to guess what, what it is out there
because, again, all we’re getting is light. So, you’ve got to make the
best of the light you have. And, if you were trying
to identify the barcode on the left, you get my
favorite honey crisp apple, whereas on the right,
you’d get a navel orange. So, it’s really important to know exactly how the
barcode should be structured because it very clearly
links you to exactly the atomic element
that you wanted to be studying. And, again, chemists are really
used to using the periodic table and learning from all the
information that’s contained in it. I see it looking a lot more like
this because if you just looked out a column, you can
just see the difference between all the lines because
these are the unique identifiers that lead us to learn
about what the element is and how much is and
how it’s moving. So, the unique lines
here are really important to discover what elements
are present in the spectrum. And just to talk about
the sun specifically, we’ve got all these
absorption lines. The giant ones come from
some really important species like hydrogen has a red line
and a couple blue greeny lines. Magnesium has these three
really bright lines right there. And sodium has a characteristic
pair of orange lines. So, now you know some
of the elements that are in the sun’s atmosphere. Awesome. Pretty straightforward. And this is a beautiful
plot that we like to show, but we really look at a lot more
like a graph where brightness is on the y-axis and
the wavelength, or color, is on the x-axis. And so, you’ve got your hydrogen
lines as deep troughs there, magnesium, sodium doesn’t show
up as well, but there it is. And another red hydrogen. So, I’ll probably be
showing most of our spectrum like this is we keep
going forward because plots are much more
easy to actually, you know, measure the depth of the dip and
how — and where the center is and how to actually understand
how those lines are — where exactly they are in
the wavelength spectrum. Because the position is critical
as is the depth of the line. So, to recap, emission
absorption lines are unique patterns that identify
the elements in the gas because we only get light so, that’s what we have
to work with. So, we’ve talked about the sun
a lot, what about other stars? What do they look like? So, the sun’s so huge it’s hard
to avoid taking a spectrum of it if you look at anything
in the day. To actually look at a star, we have to be a little
more specific and choosy about the light we want. So, you use a telescope to focus
the light into your instrument, but there are so many
stars in this field. I mean, there’s one horribly
shockingly bright star, Vega, but then there are
other things around. So, just focusing the
light’s not enough, we need to put a
mask in to block it. And the most classical
mask is just a long slit because it’s nice to have
some information not just of the object you
wanted, but along it. That does mean other objects
can creep in but, say, you blocked most
of them out, ish. Slits are pretty narrow. This is comically wide
so you can see it. It’d be smaller. And then, you disperse
the light, and save it on to a detector. And so, for this star,
Vega, when you disperse it, you can see the spectrum has
— I’ve labeled them terribly, but they’re hydrogen lines. They’re giant hydrogen
absorption lines on top of the emission coming
from the core of Vega. Okay so, Vega has a huge amount
of hydrogen in its atmosphere, kind of on top of
everything else. More than you can see. Good. So, putting a long
slit across the object and dispersing the light is what
I call long slit spectroscopy. But, dispersing — so,
dispersing stars is good but, we were promised more. What about other
astronomical objects? Saturn is a fun one
because it’s close enough that you can actually
really do this. And, normally when we talk about
pictures, I could when I talk about my long slit, I could mask out the entire beautiful
picture, but that’s really boring. So, we generally
do this instead. We’ll mask out the
portion that we’re about to see a spectrum of. So, when we do that,
I’ve rotated it because it fits better,
we’ll get this. So, if you dispersed
all the light going through that green slit, you’ll have wavelength
information along the x-axis, but you also get
information along the slit. So, I was saying, you know,
normally you’re trying to back out, block out
background objects. And so, in this case,
you don’t just block out background objects, you’re
also getting information from the ring, the disk, and
the ring on the other side. It really corresponds
beautifully. So, you also get
information along the slit. And I can’t emphasize
that enough because it means you’re getting
spatial information as well as the wavelength information that we were originally
interested in. And that’s really
powerful because, if you look at the
whole spectrum, okay, it’s really beautiful,
it looks like a rainbow. We really, on detectors,
see much more like this. It’s been spread
out by wavelength. So, the wavelength information
is there, not in the color of the plot, but in
the spread of the plot. And you can see that our
detector actually happens to be more sensitive in the red
than our eyes could have seen. That’s really cool, nice. Definitely that would have
defeated the point if we wanted to just measure red light
that our eyes can see. But, okay, what about
the spatial information? So, if we grab the light from
the upper ring and plot it as blue, and the light from
the disk and plot it as red, we’ll get something
that looks like this. And there are similarities
and differences so, the blue light is the ring
and the red light is the disk. So, similarities, we can
see these absorption lines that are coming from magnesium
and sodium and hydrogen. Those probably sound
pretty familiar because I was just talking
about them with the sun. And that’s because Saturn’s
not really going on its own. We’re actually seeing Saturn
and reflected sunlight so, therefore, we should
see features that we would’ve
seen in the sun. There they are. Excellent. But there are also differences. So, not so much in the
rings, but in the disk. And so, the disk has these
giant absorption lines which are actually methane. And we see them because the
light is actually penetrating part way into Saturn’s
atmosphere and is reflected, at some point, but as
it’s gone in and come out, it’s passed through
this volume of gas and light has been absorbed by
the methane in the atmosphere. So, just with this long slit
observation we just learned that Saturn’s atmosphere has
methane in it, that’s awesome. Easy. So, what about galaxies? What can we do with galaxies? Of course, were going
to put a long slit on it because that’s intrinsically
what we’re doing right now. And, if we plot it, it’s a
little more complicated looking. So, we’ve got along the
slit here, both there and along the y-axis, and then
we got the wavelength along the x-axis. And I’m super zoomed in so,
all we’re seeing our lines from nitrogen, hydrogen,
and another nitrogen line. Lots of, lots of nitrogen. But, they look really different than the lines were
talking about before. They’re not just
straight across, they actually change their
wavelength as they go spatially. That’s pretty cool. Why do you think that is? The Doppler effect is the reason and I’ll let someone
else explain it.>>The Doppler effect is the
apparent change in wavelength of a wave, depending on the
motion of the source toward or away from an observer. Astronomers observe this effect
with wavelengths of light, but we experience it
with sound as well.>>If you’ve ever stood
there on a street corner and you’ve heard
an ambulance go by, the first thing you hear is a
very high-pitched noise as it’s, say, coming from your
left and passing by you. And as it passes by you, what
you here are lower frequencies, a very low pitch sound. So, what is happening
in that instance is, as the ambulance is coming
toward you, the sound waves that are getting transmitted
by the horn on the ambulance, the sound waves are compressed. As it goes away from you, those
sound fronts, you could say, get stretched out so, corresponds to a longer
wavelength and a lower pitch. So, you hear a lower sound. The same principle can
be applied to light. If you have something
coming toward you, you will see the
spectrum get shifted but toward shorter wavelengths, and though shorter wavelengths
are mainly blue wavelengths. So, it get shifted, they
say, toward the blue. If something, and this
happens often in astronomy, if something is going
away from you, it’s going to get shifted
toward longer wavelengths and that’s mostly
toward the red.>>These shifts are classified by the direction they
move within the spectrum. Objects moving away
from us exhibit shift to the longer wavelengths. We call them red shifts. Objects moving toward us exhibit
shifts toward the shorter wavelength and are
called blue shifts.>>I told you we were creative
about naming things, right? Like really fundamentally
not creative. So, this is a really good
more scientific explanation. This is my favorite video
that I’m going to show you so, they are with me, it’s silly.>>[Background Music] Blue
light has shorter wavelengths than red light. When an object in
space moves towards us, it’s light waves are compressed
into higher frequencies or shorter wavelengths
and, hence, we say that the light
is blue shifted.>>It’s blue.>>When an object
moves away from us, it’s light waves are stretched
into lower frequencies –>>– It’s red –>>– Or longer wavelengths. And we say that the
light is red shifted.>>So, [laughter] so silliness
of cow abductions aside, specifically were talking
about the Doppler effect, meaning that, if you are looking
at an object that’s moving away from you, the light looks like
the wavelengths are stretched so you see it red
shifted, whereas, if you’re watching the light
source move toward you, you’re seeing the
light blue shifted. Okay. You’ve got it, here it
is one more time, I’m so sorry. But this is a little closer
to what would be thinking about in astronomy, not
lightbulbs, but some sort of point source moving. So, but our galaxy had
something different, it had lines on both sides. This cat is going help us
explore rotation [laughter]. Really specifically. So, the left side of the cat
is pretty much always coming towards us like that. And so, we blue shifted. And the right side of the
cat’s moving away from us so, it’s red shifted [laughter]. But, seriously, so the
galaxy is spinning. So, the left side of the galaxy
is being blue shifted so, the light’s more blue
when it has lines. And so, that’s how it will look,
it will be a more blue line. The center of the
galaxy sort of looks like it’s towards the
center of the possibilities. And then the right side of the
galaxy is moving away from us as the galaxy rotates so, it shows that the
line is red shifted. So, going back to what we
actually started this silly digression with, the top side of the galaxy is
showing these really, really clear red shifting
of all of the lines so, it’s moving towards
red wavelengths, meaning the top side of the
galaxy is moving away from us. On the bottom left side of
the galaxy is blue shifted so, it is moving towards us. So, that means the galaxy
is spinning like this into the plane of the sky. And we just learned that by
looking at only the light so, that’s pretty awesome
because that’s so far away. So, these long slit
spectroscopy’s really powerful. It can reveal the lines,
their structure, their motion, but I’m willing to now try to
convince you that it is inferior because you are missing
the big scale structure that you could’ve
seen otherwise. I know she just keeps changing
her mind about what she wants to convince you of, ugh. So, if you put long slits
across these, that’s good. You’ve got the big picture,
well, the tiny picture actually. You’ve got the tiny
picture along the slice. But, for this galaxy down
here, the Andromeda galaxy, if you wanted to look
at the entire galaxy, you just spent an hour
doing that one slit. So now, you have to add another
slit, spend another hour, then you add another
one, that’s another hour. So, by the time you wanted
to cover the whole galaxy, you just spent at least the
night, if not more than a night, trying to cover it so, and
then, horribly you have to so the image back together. So, you better be really sure about how you positioned
everything, especially if you’re
coming back the next night. Yay. Our jobs aren’t
complicated at all. Saturn is, you know,
the same way. If you were trying to
do it, you would want to space everything out. If you were trying to
learn about, you know, the different compositions of
the disk, not just of one slice of it, but you know,
weirdly, planets change in composition as you go round. So, shoot, you better
look at the whole thing, but only with a lot
of telescope time. So, quickly gets really
expensive and really difficult to try to rebuild
the bigger picture. So, now you guys
are going to have to help me rebuild the picture
of a couple of classical, well, one of them to classical
painting and one of them is not. So, this one to classical
painting. From these four slits, the
only light I’m giving you, what’s this painting? Ah, you guys know
too much, okay. So, it’s van Gogh’s
“Starry Night” so, maybe, you’d be good astronomers
because you can interpolate from what I just gave you. So, as you’ve got it, Van
Gogh’s “Starry Night”. This one will be harder,
it’s a movie poster. It’s even red shifted in blue
shifted, guys [laughter]. It came out a couple years ago.>>Wonder Woman?>>Ah, you did it [applause]. Yay. So, the point is, trying
to construct the bigger picture from like tiny bits of
information is really hard. There’s a classic parable,
I think it’s Chinese, depending on what tiny part
of an animal you look at, you might come up with a
really different picture of what the animal looks like. So, if you were looking
at a blindfolded and you didn’t have an idea
of what you were studying, you know, you come up with
really different ideas of what the animal was. Whether it’s an elephant is
a spear, the elephant’s a fan or a wall or rope or a tree, you can see why they’d
come to that conclusion. But you missed it, it’s
a whole huge animal, but it has really
different parts. So, I think I’ve convinced you. Getting the big pictures
really important because otherwise it’s
really hard to learn about. But the problem is, if you just
dispersed the entire galaxy, just like you didn’t
put a mask on it, if you look at this picture,
you can probably see that bits of the orange light are on top
of the bits of green light are on top of the blue light
and it’s a horrible mess because you just
lost any difference between the spatial information
and the spectral information, or the wavelength information. So, that was a disaster. That was not a way to
get the bigger picture. So, to sort of wrap
that section up, long slit spectroscopy gives
you a really narrow window into the presence of
elements and their movement and it misses the
bigger picture. But luckily I’m building
an instrument that will give us
the entire picture. And so, that was long
slit spectroscopy. If we went the entire picture, we should probably call it
integral field spectroscopy, because not creative. The only way to do it. So, if you are trying to get
the picture of the whole galaxy, we’re still going
to use telescopes because they’re the
best things out there. But instead of sending
it to a normal mirror after the telescope
has focus the light, we’re going to use a really
specific different mirror. It’s not just a flat mirror,
it’s actually been broken into slices or strips. And each of the strips is
slightly tilted with respect to the strip next
to it to the extent that it’s sending the
light to different places. What I mean is, the top strip of this galaxy’s going
over to the left. The central part’s
headed to the middle, and the bottom slice is
headed over to the right. So, we just effectively took the
galaxy, slice it into pieces, and then just move them
away from each other. Because, if they’re
next to each other and we disperse them,
it’s a disaster. We went over that. Everything is lost. So, but, since we’ve
already focused the light, it started diverging
again like it does when I’m not wearing
my glasses or they’re in the wrong place on my nose. So, you need new lenses or
something to reimage the light and that causes it to
form basically strips like originally formed on
this mirror, but reformatted so which one new, long slit. And we just went
over long slits. We know how to do long slits. We already are really good
at dispersing long slits. So, we just took this
image and we chopped it up and reformatted it
to make a long slit that will then let us see the
whole picture of the galaxy. Because we took that slit and
we sent it to a spectrograph where it will be dispersed. So, you know, you can
actually see the little bits of galaxy in these pictures. And then it spread out and
then you really have a mass because you just chopped the
light into little pieces, spread it out, and
put it on a detector. And then your astronomers
are really sad because we just gave
them a mass. So, we also don’t just get
to build them an instrument, we get to build them software
that will help them reassemble that data into a data queue. And I’ll call it a
cube because, you know, the long slit was giving
us just spatial information and wavelength information. So, now we don’t just have one
spatial direction, we have both. So, were basically getting
images at every wavelength and we stack them
up to get a cube. If you wanted, you could show
this in the same way as a movie with you having to spatial
directions and then, instead of wavelength,
you’d have time. So, you can scroll through the
wavelength or time direction and pause on a frame and have
all the information you wanted to look at one individual
emission or absorption line. That’s really cool. So, we have to build them
software as well as instruments. They’re very greedy, how rude. So, that’s all of integral
field spectroscopy. I’m actually specifically
building this part right here. At first, I should actually
place it in perspective so, first we need a telescope. So, at Carnegie Observatories, we have Las Campanas
Observatories down in La Serena, Chile, along the South
American coast right there so, I get to fly there, you
know, probably three or four times a year to
try to do our observations. And I’ll get to fly there
even more which is both good and terrible to commission
this instrument. My cat will be grumpy because
I’ll be leaving a lot but, oh well, I mean, we
don’t have a choice. So, specifically in Las
Campanas Observatory, we have four telescopes. We’ve got to smaller
telescopes over here and then the Magellan telescopes which are basically twin
telescopes I would say. They are called the Clay and
the Baade and they sit next to each other, but they’re
not in the same building. They have separate domes that
are connected by a catwalk so you can just walk along it if
you really wanted to at night, to admire the night sky. So, zooming in specifically,
I’m using the Baade telescope. And so, that’s 6.5 meters, or more usefully,
21 feet in diameter. And so, we always talk about
telescopes because we want as many photons as possible as
you called them a light bucket. We want our bucket to be as big
as possible, the primary mirror. So, we always tell our
telescopes apart by saying, you know, this one’s a 21- foot diameter primary
mirror telescope. Because that’s one of the
most important parts about it. Then, you have to talk
about the instruments because that’s really
important to. But, specifically, this
observatory is located in one of the best sites
I’ve ever seen. So, during my last observing
run on the Baade telescope, this is what the
sky looked like. So, that’s the Milky Way, in
case it wasn’t clear [laughter]. That’s one of the Magellanic
clouds rotating through. I think it’s the large one. And then this happens. And it’s not actually the
sun coming up, it’s the moon. So, even with — so that’s
how dark the site is, like the moon casts
shadows that you can see. So, it’s really incredible. So, anyway, so this is
my last observing run and it was awesome. So, this is a fantastic site
and a fantastic telescope to put our instrument on. So, then the other side is, I’m
not building the spectrograph. Whoop, just knocking
it off the [inaudible]. So, I’m using an instrument
that already exists. It is a wide-field imaging
spectrograph called IMAX, has and Ackerman, no
one cares [laughter]. But what’s cool is
it’s got a slot here, you can see how the
panels come off. It’s got a slot somewhere
around on the other side, I couldn’t get a picture of it, that you can take these panels
off and you can put in something to modify the instrument. And that’s really cool. So, it’s getting the
light from the telescope like through this giant hatch
where it attaches to that hatch. So, the light from the
telescope’s headed inwards and then there’s a spot
that we can modify the beam. So, this is perfect because
that means I don’t have to build everything related
to the detector or the camera. I don’t have to touch that. I also don’t have to touch the
dispersion gratings, orgrisms, or prisms because
those are expensive and really complicated and, if
someone already built them well, why not make something
to just insert in to give this instrument
a whole new capability that it wouldn’t have
been able to do before. So, okay cool, perfect. So, I don’t have to build
the spectrograph, bonus. What I do need to build
is all of this in here. Excellent. So, let’s focus on that. So, we were talking about
integral field spectroscopy, if you’re just putting in
a unit to a spectrograph, that means were building
an integral field unit to modify an existing
spectrograph. And it has a ridiculous acronym, it’s called the reformatting
optically sensitive IMAX enhancing integral field unit. And we really did that to
make it called the Rosie IFU. And in case you didn’t catch
it, I’m Dr. Rosalie McGurk so, that wasn’t at all on
purpose [laughter]. But, of course, the only logo
we could use was a multicolored rose, that’s just obvious. Anyway, so what exactly
does my instrument do? So, the telescope
is given us an image that is not quite the
field of the whole moon. So, we actually need to
stop it down a little to show you what
I’m talking about. And, inside of that, so, this
is what the instrument takes in, that would be huge. Inside of that, we’re
actually going to grab a field that is 30 times smaller
than the moon in diameter. And that is perfect
because it is the size of our local galaxies. And I have to state, for the
record, since I’m comparing it to the moon, it sounds like
I’m grabbing a small field. There is one other instrument
that grabs the field this large in existence so,
that’s really cool. And they had to build
100 billion — hundred million dollar project
to do it, and we’re going to be much, much, much
less in budget than that. So, this is a much better
idea, much more reasonable. They had to build
24 spectrographs and we’re using one
that already exists. Oh God. So, we’re taking
that image that’s focused by the telescope
and then we chop it into four pieces immediately. No dillydallying around. It’s the first optic
the light hits. And I’m going to pick one
of them to talk about it, but keep in mind, we do all of the following
to the whole field. So, we take that one field and
then we magnify it by a factor of three, so it just got huge. And then we chop
it into 21 pieces. Okay, good. Then we take all
21 of those pieces, we need to de-magnify them
by that same factor of three because we need to bring the
image back to the original size because normally the
spectrograph just works with the telescope. There’s nothing in between. So, if you magnified it, now
you need to bring it back down so the spectrograph
can handle it. So, we broke it into
all those pieces. If we disperse it just like
that, that it be terrible, they’d all be on
top of each other. There would’ve been no point. So, now we need to line them up into a long slit
that’s far too long to show on the projector, of course. So, there are nine more up
there, nine more down there to bring it up to the 21. Good, not complicated at all. So, really, that was a cartoon
version of what we’re doing to the light, this is what we’re
actually doing with the optics. So, we take the light
from the telescope. It’s focused on to this mirror where we chop it
into four pieces. I’m only showing one to
start because it doesn’t need to be more complicated. Then we have a lens that
magnifies the light, we send it to the image
slicer and, of course, I can only show one of them because the image slicer
slices the light and fans them up this way, out of the screen. Or into the screen because it
does it evenly on both sides. So, I’m only showing
the center one because we don’t have 3-D
projection technology get, we’re working on it. So, it’s fanned out. We send it then to a second
lens where it’s de-magnified by that factor of three. And then a pair of just flat
fold mirrors aligns the light into that slit to send
it into the spectrograph. And so, this is one of
those fields and one of those slices that we made. This is all four subfields, so we chop the light
into four pieces. And then we had an image
slicer for each of them so, that means we took the four
fields and we chop each of them into 21 pieces. So, we have 84 optical paths. Great. And so, we
have to reformat each of those subfields
into one long slit. So, and even more find
that, I didn’t mention it, when you’re making
telescopes, you either get to have a nice flat focal
plane where you’d want to put a detector, but your
image quality is less good to have it be flat. Or you can have fantastic
image quality, but the focal point is curved, meaning the light isn’t
focused there or there or there. So, if you are putting it
straight on to a detector, you’d be pretty bummed
about that because it’d be out of focus in spots. Ugh. But we don’t have
to do quite yet so, we sliced all the light up and
we made it very complicated. Yay. So, we sliced those four
subfields up, we broke them into pieces, and we reformatted
each of them into one long slit. So, that means, in our field of
view, we have for long slits. And that’s the size
of the original image. So, we chopped it nice and fine. Good. And so, what I want
you to notice the diameter of this is actually
2.5 m, meaning — step outside the
podium, about this big. The projector’s bigger
than my instrument will be. Great. Very small, 84 optical
beams, nice and compact and very challenging to
put together and align. Great. So, this is what
that whole field looks like if you projected
onto the camera or the detector that’s
busy reading the light out. And I’m going to get rid
of the IMAX field-of-view because it’s just messy. So, when you disperse
each of these, it’s going to look like that. So, that’s what the dispersed
light will look light from each slit onto
our detector so, this is why it’s really
critical to have software to put it back together because
the astronomers would be very angry if you just
sent them that’s. Check. Can’t argue. So, we’re working
on the software, what this slide is meant
to remind me to say. Software in progress
using Python. So, then what are
the other parts of building this instrument,
because I’ve given an overview. But what’s actually happening? So, all I can talk about
the image slicer so, this is what one of our
image slicers look like. And to give it a little sense
of scale, that’s a calculator. So, it’s not large,
not large at all. And so, you can see each of the shiny slices here
is slightly offset an angle from the one next to it. So, that causes the
image to be redirected where the center slice
sending it straight back out. The other way to put it
in scale is that’s a dime. Oh good. But to see what the
image slicer’s actually doing since I haven’t really like, other than waving my hands
wildly, I haven’t shown you. So, I’m going to give
you a top view of this. So, there it is. There’s the image slicer
and it fans the light out into 21 beams,
I’ll say up and down because that’s what it
looks like right now. So, that’s the second lens there
the de-magnifies the light. There’s one of the fold mirrors,
and the other one’s sort of a mess down that strip. And, again, this picture’s
bigger than all of our optics. Our optics are actually
much more like, the lenses may be the
size of my thumbnail. And the mirrors are probably
more like the pinky nail. So, yay, small, compact. So, just to zoom in a little,
I’ve actually deceived you. We didn’t make it into one, long
slit, we actually realize that, if you take a big circular piece
of metal and you slice for line down it, the structural
integrity of that piece of metal is like shot. It’s done. It wobbles when you poke it. So, that doesn’t work. So, we realized that we can take
each one of the little slices that we made, that
we fanned out, and we can just offset them
a little bit from the center and so, that’s what this
is really trying to show. That’s one of the slices. My hand’s bouncing
too much, good. That, you know, so, each
of the slices are offset by 6 millimeters
from each other. Just so that the metal plate
that we’re building on top of doesn’t give way to
gravity because, of course, this whole instrument
has to spend. That’d be too easy
any other way. It has to rotate
with the night sky. Good, good, not complicated
at all. So, then, jumping to talking about the other part I
can easily share is all of these optics are
floating in space. That’s not realistic. Clearly, they have to
be held by something. So, I’ve been working
with a mechanical engineer who is busy designing
how to hold, you know, the optics I put in a box there. So, we’ve got that second lens
the de-magnifies the light held by this great pink arm. We’ve got one of the fold
mirrors, words, right there. And another one of the fold
mirrors right there in red and it sends it down
through a little window into the spectrograph. Of course, they all
have to be held by, you know, a clamp of some kind. We’ll be gluing these
in because it turns out you can’t hold the
other side of the lens without blocking the
beam that’s headed into the rest of the instrument. So, it ends up being
wonderfully complicated. And so, we were trying to find
out if we could 3-D print this or if we could not
3-D print this. And the answer is we cannot. Our 3-D printer is not
high enough resolution, but it’s a really
great test case. So, I should have flipped
the image, I forgot. That’s where the
lenses will sit. And we’re doing them in units
of five because, otherwise, if you try to string
all 21 together, it turns into a nightmare. It’s already a little
of a nightmare, it would be more of a nightmare. So, the light would be
coming in from the side, go through the lens, hit the
fold mirrors, and then go down. Okay, so, that’s what my
instrument will look like. It will be fantastic. We’ll get spectroscopy over
this whole area once we put everything back together. What science can we do with it? I’ll go through it briefly since I didn’t leave
time for questions. So, with this galaxy,
it is a mess. It’s what we call
forward disk galaxy. And who knows what is
happening to this galaxy, if it is rotating,
what’s going on. It’s a complicated picture so, we need a much more
complicated way to look at it than just a long slit. So, if we can actually
make it to the movie so, this galaxy shows rotation and
it has emission in nitrogen. Is it going? Yes, it’s going, in nitrogen,
hydrogen, and sulfur. So, it’s going to slowly move
through it, and there it goes. That was one of them. So, we just saw a flash
of nitrogen, hydrogen, and nitrogen again, and
those were two sulfur lines. So, what way is it rotating? We’ll do it again. Length okay. It’s really rotating
from left to right so, even though it’s got this
like ridiculous feature of the really weird
sort of bulge or something that’s happened,
it hasn’t affected the galaxy. The galaxy might be star
forming a little more because of it’s probably a
Burger going on right there, but it hasn’t affected
the rest of the galaxy. It’s rotating as normal. Okay, good. We wouldn’t have known that without a much more
complicated picture. It could have had plumes, it could have had all
sorts of weird things. So, here is another
example of how awesome it is to have the whole picture. So, this is a huge — this
is a galaxy, start over. This is a combined
image of Hubble and the Chandra x-ray telescope, so the x-ray telescope’s
shown in blue. And specifically, we’re looking
at a disk galaxy that’s falling into a giant galaxy cluster. So, it’s falling into a
whole bunch of hot, hot gas and it’s going to interact
with tons of other stars. But, while it’s interacting
with this hot gas as it falls into the galaxy cluster, that hot gas is actually
stripping gas that was originally part
of the galaxy off of it, leaving this phenomenal
hot gas plume that you can only see in x-rays. And in emission lines. And what’s really
fantastic, if it will do it, you can see the hydrogen
and nitrogen lines of this gas even extending
out to this, you know, hundred thousand light years and it’s not just
streaming off the galaxy, it actually still knows
about the rotation of its original galaxy. Because you can see the
gas on there is rotating as it’s streaming, there goes. So, it’s rotating as it’s
streaming off the galaxy. We would never have guessed
that, we would’ve guessed that, once it was stripped
from the galaxy, it wouldn’t know
where it came from. It wouldn’t retain
any of that rotation. So, then, this is the final one. There’s an active black hole
sitting in the center of this, and it’s busy blowing
filaments of gas out into sort of these cavities,
these big radio bubbles. And then it’s slowly
starting to cool. But the system is
horribly complicated because it’s not just
blowing them in one plane, it’s blowing them in all of it. So, if you want to try to
understand what’s happening, you need a much more dynamic
approach to studying it. So, it should zoom through
the boring wavelengths until it reaches
the emission lines. But, once it does
that, you can start to see there is ridiculous
incredible far-flung structure even out up to there and there’s
even a high velocity thing right close to the galaxy, meaning that the black hole
has recently blown out very fast moving material. And then it’s also got some
sulfur emission even at sort of close, but sort of at
close radii from the galaxy. So, by studying something
like this, you might be able to piece together how many epics of the black hole blowing
giant bubbles have happened, how far they can travel, what
speeds they might have started at to get to at that distance. So, you can actually start to piece together how
blackhole feedback works because we don’t understand
how black holes blow bubbles like this. We don’t know how often
they do it, we don’t know with what energy they do it. So, we really need
data like this to try to build it together,
try to put it together. And then, finally,
movies are beautiful but they’re very
hard to publish. At least on a paper that other
people might read weirdly. So, actually what astronomers
study is often plots much more like this, so this is a
pretty standard disk galaxy. And they’ve shown where
they got data enough to measure the velocity
of the gas in this galaxy. And so, I meant to put velocity
up here but I forgot so, this is the velocity that they
measured using the Doppler shift of this gas with more blue gas
being blue shifted towards us and read gas being red
shifted away from us because we’re not
creative again. So, you can see, not only
is the galaxy rotating, but it has really
detailed structure as it passes through the center. So, you can use 3-D
data like this to complexly model the galaxy
is not just, you know, one line, but as an actual 3-D structure
to try to understand dynamically where is the mass in the galaxy. And if you have really
high resolution information in the center, you can measure
the black hole mass that way by watching how it’s
tweaking the gas around it. So, that’s really fantastic. So, this is more of what
data looks like when we talk about data, not just
beautiful movies. So, then in summary, I’ve
shown that spectroscopy of emission absorption lines
shows the presence of elements and their movements
through the Doppler shift. Long slit spectroscopy
only shows part of the picture while integral
field spectroscopy shows the entire picture. And our integral field
spectrograph will open up a whole new avenue of
science that can be done on our Magellan telescope. So, with that, thank you
so much for your attention. I can take questions about
all the things [applause].

1 thought on “A New Tool to Map Entire Galaxies”

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