[Spitzer-news] Galaxies Don Mask of Stars in New Spitzer Image

spitzer-news at lists.ipac.caltech.edu spitzer-news at lists.ipac.caltech.edu
Wed Apr 26 13:51:46 PDT 2006

In this issue:

1) Galaxies Don Mask of Stars in New Spitzer Image 
2) Great Observatories Present Rainbow of a Galaxy
3) Spitzer Profile: Jim Keller, Spitzer Media Producer
4) The Infrared Background: Sometimes It's What You Don't See That
5) Old and New Fellows Meet at a Spitzer Science Center Symposium



A pair of dancing galaxies appears dressed for a cosmic masquerade in a
new image from NASA's Spitzer Space Telescope. 

The infrared picture shows what looks like two icy blue eyes staring
through an elaborate, swirling red mask. These "eyes" are actually the
cores of two merging galaxies, called NGC 2207 and IC 2163, which
recently met and began to twirl around each other. 

The "mask" is made up of the galaxies' twisted spiral arms. Dotted along
the arms, like strings of decorative pearls, are dusty clusters of
newborn stars. This is the first time that clusters of this type, called
"beads on a string" by astronomers, have been seen in NGC 2207 and IC

"This is the most elaborate case of beading we've seen in galaxies,"
said Dr. Debra Elmegreen of Vassar College in Poughkeepsie, N.Y. "They
are evenly spaced and sized along the arms of both galaxies." 

Elmegreen is lead author of a paper describing the Spitzer observations
in the May 1 issue of the Astrophysical Journal. The image can be viewed
at http://www.spitzer.caltech.edu/spitzer   
Astronomers say the beads were formed when the galactic duo first met.
"The galaxies shook each other, causing gas and dust to move around and
collect into pockets dense enough to collapse gravitationally," said Dr.
Kartik Sheth of NASA's Spitzer Science Center at the California
Institute of Technology in Pasadena. Once this material condensed into
thick bead-like clouds, stars of various sizes began to pop up within

Spitzer's infrared camera was able to see the dusty clouds for the first
time because they glow with infrared light. The hot, young stars housed
inside the clouds heat up the dust, which then radiates at infrared
wavelengths.  This dust is false-colored red in the image, while stars
are represented in blue.

The Spitzer data also reveal an unusually bright bead adorning the left
side of the "mask." This dazzling orb is so packed full of dusty
materials that it accounts for five percent of the total infrared light
coming from both galaxies. Elmegreen's team thinks the central stars in
this dense cluster might have merged to become a black hole.

Visible-light images of the galaxies show stars located inside the
beads, but the beads themselves are invisible. In those pictures, the
galaxies look more like a set of owl-like eyes with "feathers" of
scattered stars. 
NGC 2207 and IC 2163 are located 140 million light-years away in the
Canis Major constellation. The two galaxies will meld into one in about
500 million years, bringing their masquerade days to an end. 

Other authors of this research include Bruce Elmegreen of IBM Watson
Research Center, Yorktown Heights, N.Y., Michele Kaufman of Ohio State
University, Columbus; Curt Struck of Iowa State, Ames; Magnus Thomasson
of Onsala Space Observatory, Sweden; and Elias Brinks of the University
of Hertfordshire, United Kingdom.

The Jet Propulsion Laboratory manages the Spitzer Space Telescope
mission for NASA's Science Mission Directorate, Washington. Science
operations are conducted at the Spitzer Science Center at Caltech. JPL
is a division of Caltech. Spitzer's infrared array camera was built by
NASA's Goddard Space Flight Center, Greenbelt, Md. The instrument's
principal investigator is Dr. Giovanni Fazio of the Harvard-Smithsonian
Center for Astrophysics.

For more information about Spitzer, visit
http://www.spitzer.caltech.edu/spitzer/ .

For more information about NASA and agency programs on the Web, visit
http://www.nasa.gov/home/ .




NASA's Spitzer, Hubble, and Chandra space observatories teamed up to
create this multi-wavelength, false-colored view of the M82 galaxy. The
lively portrait celebrates Hubble's "sweet sixteen" birthday. 




(Spitzer Profiles are portaits of the people who make the Spitzer
mission possible, written in their own words. In these features you can
learn more about our science, engineering, and support personnel and how
many different types of people are needed to make the mission possible.)

What do you do with a degree in theatre? Well, work for NASA, of course! 

It may surprise people that it takes people with all sorts of
backgrounds to make a space mission run, but I'm living proof. 

Actually, I've always been interested in science. I fell in love with
the stars as a kid watching science fiction movies and television shows.
I always got good grades in science and math. My teachers in grade
school all assumed I was going to end up being a scientist or engineer. 

But then, I started needing to do lab work in my science classes. I
vividly remember one experience in Chemistry class in high school. I was
following the instructions, when my beaker suddenly started producing a
thick cloud of black smoke. My chemistry teacher swooped in, grabbed the
beaker, and ran to the fume hood with it. To this day I don't know what
I did wrong. After the smoke cleared, my teacher looked at me, shook her
head, and said, "The students who are the best at the book work are
always the most hopeless in the lab." 

I had always struggled with my lab sections. I realized then that the
reason was that while I can understand the research that other people
do, I'm really not suited to being the one who does the research. I
think it's a personality thing. I'm really an artist at heart. 

By that time I'd already discovered that I loved drama and literature,
so even though my grades in those subjects had never been as good as my
math and science grades, I realized I should follow my love more than my
aptitude. It was the best decision I ever made. 

I went to the University of Southern California, where I majored in
theatre and classics (that's Latin and Greek language and culture), but
I took a lot of Geology classes (and nearly finished a minor in it) just
for fun. But while I was at USC I worked in one of the libraries on
campus. In my senior year, they started experimenting with writing web
pages for this new thing called Mosaic -- the first graphical web
browser (which later evolved into Netscape), and told me to learn to
write web pages. I did so, never imagining the impact the World Wide Web
would later have on the me and on the whole planet. 

After I graduated my career as an actor didn't take off, not
surprisingly (I was on Days of our Lives a few times, and can be seen
briefly in one episode of Melrose Place, but they never even let me
talk). So I went to work in a video production company, using my acting
skills in the marketing department. The company produced patient
education videos for hospitals. I learned how to use videos to teach by
watching what the director-producer there did. After a year there, I
took a job back at USC managing a computer lab for the School of Fine
Arts, where I also learned to edit video and sat in on a lot of graphic
design classes. I left there to work as a producer for an online news
magazine, and thought I'd made it -- until the dot-com crash! 

I started working on Spitzer (back then called SIRTF) in 2001, on the
recommendation of a friend who works here. I came in as the website
developer, but my bosses quickly realized that I also know video
production and graphic design, so today I get to do all three. I direct
and co-produce our popular Ask an Astronomer videos, design and maintain
websites, and create several of our print publications. It's a fun and
very varied job. 

So, even though I got here by a roundabout method, I've finally found a
job that merges my love of the arts with my love of science. And I don't
have to worry about creating any toxic fumes in the lab. 

I'm still active in the performing arts. I'm a member of all three
professional acting unions, but I work mostly on stage in smaller
theatres around Los Angeles (they're the ones who are most understanding
about the fact that I have a real job, too). I've now learned that I
don't need to make a living in theatre, because I can use what I know
from my performing arts background here at the Spitzer Science Center. 

So when your parents ask you what you're going to do with that liberal
arts degree, make sure to tell them that you could always work for NASA. 




It probably comes as no surprise that as powerful as our telescopes are,
there are limits to what they can see. As we look farther out into the
universe, objects appear smaller and dimmer to us, until at some point,
we can't see them as discrete objects any more. But limits are always
tantalizing. After all, the most distant objects in the universe are
also the youngest (due to the finite speed of light), and therefore
desperately interesting to astronomers. Of course, the more distant an
object, the fainter it is likely to be. Will we ever be able to see
things faint enough to find the very first starlight emitted by the
first stars and galaxies? For the time being, we have no telescope with
the resolving power and sensitivity to see galaxies that far away. But
astronomers have never been good at leaving well enough alone and
accepting limitations. Lately, a group of astronomers using the Spitzer
Space Telescope have found a method of observing distant galaxies that
are, in fact, too faint for Spitzer too see. 

How could that possibly work? How can a telescope observe something
beyond its limits of sensitivity? How can you even be sure there's
something out there to observe, if, by the very definition, you can't
see it? In fact, we are sure that there are stars and galaxies so far
away from us that we can't see them. What we can see is a background
glow, all around the sky, created by the combined light of all these
distant, invisible sources. 

Is there a universal background glow in visible light? Amazingly, the
answer is "not any more." Until about ten years ago, there were indeed
visible light photons detected by our telescopes that astronomers could
not identify sources for. But that changed when the Hubble Space
Telescope released its"Deep Field." After staring at a relatively"empty"
part of the sky for over a week, Hubble found thousands of tiny, distant
galaxies that had never been seen before. When these objects were
finally resolved, it was a quick calculation to confirm that they had
been responsible for the leftover visible light. In a real way, Hubble
had seen as much of the universe as it was possible to see in visible
light. Every photon could now be identified with a specific source. 

But this isn't the case for the infrared universe; there is still a
faint, long-wavelength infrared glow coming from the entire sky. What
might be causing this infrared background? At this point, we're looking
back to the time when the very first stars and galaxies began to form.
This radiation is likely the heavily red-shifted remnant signal of
young, giant stars bursting into existence, or super-heated gases
falling into giant black holes at the cores of young galaxies. But some
of the background is probably from nearer, less dramatic sources such as
dim galaxies. What's up to astronomers now is to resolve as much of the
background as they can, slowly whittling away the extra light. What's
left over may, after the next generation of space telescopes comes
along, give us a view of the first galaxies to ever exist. 

Amazingly, a team of astronomers using NASA's Spitzer Space Telescope
has recently been able to resolve about 80% of the far-infrared
background by using a clever trick to see the unseeable. The idea is
this: first, identify a population of distant galaxies that you can see
at shorter infrared wavelengths. Then, set your telescope to observe
these galaxies at longer wavelengths where the infrared background is
detected. The "target" galaxies may no longer be visible, but you can
measure how much infrared background is coming from that part of the
sky. Next, make lots and lots of observations of these galaxies and add
them all together. Even if you can't see the individual galaxies at the
longer wavelength, maybe by adding the data from many galaxies together,
you'll begin to see some sort of fluctuation signal produced by your
combined target galaxies. 

Dole and his team undertook an ambitious program. First, they needed to
find near- and far-infrared observations of several thousand galaxies.
Luckily, the Multiband Imaging Photometer for Spitzer (MIPS) had just
completed a deep survey of parts of the infrared sky, creating matching
data sets at 24, 70, and 160 microns. The astronomer and his colleagues
at the Institut d'Astrophysique Spatiale and the University of Arizona
identified over 20,000 faint galaxies that were just barely visible at
24 microns. Then, they added the collected light from more and more
galaxies together, hoping to coax out a faint signal at longer
wavelengths. All in all, Dole's team combined infrared images of over
20,000 galaxies. And as more and more images were stacked up, Dole and
his team did indeed see signals at 70 and 160 microns begin to emerge.
In a real way, they found a way to observe galaxies that were too faint
for Spitzer to see, at least in individual observations. The team also
went as far as to conduct an opposite experiment: when Spitzer surveyed
the sky where no galaxies were visible at 24 microns, no far infrared
background showed up either. 

Amazingly, Dole's observations can account for 80% of the infrared
background, knocking a huge chunk out of the unresolved background. And
what's more, astronomers now know what sort of galaxies contribute the
most to the infrared background: starburst galaxies about 7 billion
light-years away from us. This population of galaxies is extremely
bright in the infrared, as entire galaxies are lit up with the glow of
new stars still embedded in the clouds of dust and gas they were born

The remaining 20% is now the big mystery. This light must come from
objects even more distant, maybe even from the very first starlight that
led the universe out of its dark age. At this point, that much is still
beyond our grasp. 

Still, few people realized just how powerful a tool for probing the very
early universe Spitzer could be. As Dole observes, "Just 10 years after
the discovery of the infrared background in the COBE data, we can now
give more accurate measurements of it with Spitzer and, more
importantly, describe what the galaxies responsible for this infrared
background are. This illustrates the great role of the infrared in
cosmology, and more importantly, why we need high quality data in the
whole electromagnetic spectrum." 




Old and new participants of the Spitzer Space Telescope Fellowship
program will meet at the Spitzer Science Center on April 10 and 11,
2006, for a symposium that will address astronomical topics ranging from
cosmic dust to a species of "failed stars," known as brown dwarfs. 

Every year, a handful of recent PhDs from across the globe are selected
to participate in the fellowship program. The program funds participants
to focus solely on their Spitzer-related research interests for three
years. They also have access to Spitzer Science Center resources and the
option to work at a world-class US-based institution of their choice.
The first group of fellows was selected in 2002. 



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