Transcript PPT 15MB - HubbleSOURCE

Great Observatories
Galactic Center Region
Image Unveiling
Science Telecon
October 6, 2009
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Multiwavelength Observations
Dr. Frank Summers
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Support Web Site
• http://hubblesource.stsci.edu/events/iyafinale/support/
• Generic press release
• Generic media alert
• Composite image caption (PDF)
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Hubble Space Telescope
• Visible, ultraviolet, and
infrared observations
– 115-2500 nanometers
– 2.4 meter mirror
• Launched April 1990
• Low Earth orbit
– 600 km
– 97 minutes
• Baltimore, MD
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Chandra X-ray Observatory
• X-ray observations
– 0.17-17 nanometers
– 4 cylindrical mirrors
• Launched July 1999
• Elliptical orbit
– 10-140 thousand km
– 64 hr 18 min
• Boston, MA
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Spitzer Space Telescope
• Infrared observations
– 3-180 microns
– 0.85 meter mirror
• Launched August 2003
– May 2009 “warm” mission
• Earth-trailing orbit
– 0.1 AU per year
• Pasadena, CA
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Spitzer
Hubble
Chandra
Compton
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Galactic Center Region
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90 degrees wide
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12 degrees
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4 degrees
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1 degree
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0.4 degrees
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Hubble – near infrared
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Spitzer – infrared
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Chandra – x-rays
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Spitzer Space Telescope
Dr. Susan Stolovy
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The Galactic Center as Seen From the
Spitzer Space Telescope/IRAC
Dr. Susan Stolovy (PI)
Spitzer Science Center/Caltech
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Why Observe the Galactic Center with Spitzer?
The Galactic Center (GC)
is invisible at optical
wavelengths
(0.4-0.7 microns) from
Earth even with the largest
telescope imaginable! The
interstellar dust in the
plane of our Milky Way
galaxy absorbs the light
from the center, which is
26,000 light years away
from us.
Spitzer’s mid-infrared
cameras see through the
dust and can cover large
areas efficiently.
Artist’s schematic of Milky Way Galaxy (arrow connects the Solar System
and the GC)
Image courtesy R. Hurt, SSC
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The 4 IRAC cameras give us a view extending all the way to the GC:
stars (mostly red giants), warm dust, and dark clouds
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The GC is revealed at longer infrared wavelengths!
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Spitzer/IRAC Galactic Center (GC) survey details
 Field of View covered: 890 x 640 light years assuming the
distance to the GC is 26,000 light years
 Area in sky covered is 1.9 x 1.4 degrees (roughly equivalent
to area 14 full moons would cover)
 Observed with 4 mid-infrared cameras from Infrared Array
Camera (IRAC) at 3.6, 4.5, 5.8, and 8.0 microns
 3.6 and 4.5 microns show mostly stars and 5.8 and 8.0
show both stars and warm, glowing dust. The glowing dust
emission seen in the IRAC images is mostly from tiny, sootlike particles called polycyclic aromatic hydrocarbons
(PAH’s). These particles exist on Earth as pollution!
 IRAC survey took only 16 hours of telescope time to
complete
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8 Micron Image of Galactic Center
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8 Micron image close-ups showing examples of regions
where massive stars have recently formed
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4 million solar
mass black
hole hiding
here
Quintuplet
cluster
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Radio emission is bright at Sgr A* (black hole), supernova remnants, star
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forming regions, and mysterious linear filaments near strong magnetic fields
Some Spitzer/IRAC Galactic Center Results
 Largest, most sensitive, highest resolution (1-2’’) map of
the GC at mid-infrared wavelengths
 We see spectacular, complex structure in glowing dust
emission, from compact globules to long, stringy filaments
 Over one million stars detected in the survey, but region is
so crowded that there are many more that we can’t detect
 Dark, obscuring clouds seen at many scales
 Star-forming regions imaged at GC distance and in spiral
arms along the line of sight
 Follow-up spectroscopy from Spitzer/IRS has led to
discovery of young stellar objects (baby stars) in the GC
(An et al. 2009, submitted to ApJL)
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Spitzer’s view of the Galactic Center
3.6 microns=blue, 4.5 microns=green, 5.8 microns=orange and 8.0 microns=red
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Hubble Space Telescope
Dr. Susan Stolovy
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The Galactic Center as Seen from the
Hubble Space Telescope/NICMOS
Dr. Susan Stolovy
Spitzer Science Center/Caltech 39
PI: D. Wang, UMASS
The HST survey of ionized hydrogen gas (Paschen alpha) in
Galactic Center (GC) was observed using the near-infrared
camera on Hubble called NICMOS (Near-Infrared Camera and
Multi-Object Spectrometer)
Although there is still much absorption of light at a wavelength
of 1.9 microns from the GC by interstellar dust, enough light
gets through in deep exposures to make a large-scale map of
the ionized gas possible to make.
This is the sharpest image ever of such a large region in the
GC; it reveals much about how massive stars form, evolve,
and interact with their environment
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HST/NICMOS GC survey details
 Field of view covered: 270 x 90 light years assuming the distance to
the Galactic Center is 26,000 light years
 Area in sky covered is 0.6 x 0.2 degrees, roughly equivalent to area
of covered by 1/2 full moon; (it’s cropped to a smaller area in press
image, however, about 0.4 degrees across in panel “b”)
 The Paschen series of hydrogen spectral lines in the infrared is
named after the German physicist Louis Paschen, who discovered
them in 1908 (the alpha line, at 1.87 microns, is the strongest of the
series). The Earth’s atmosphere absorbs this line from celestial
sources, so we need a telescope in space to observe it.
 NICMOS observations made in 2 narrow-band filters with
wavelengths of 1.87 microns and 1.90 microns. Paschen alpha
emission arises from ionized hydrogen gas that excited by hot stars.
 Took 144 orbits of telescope time to complete: this is the largest area
ever covered by NICMOS by a single program. The data have 10
times better resolution (sharpness) than the Spitzer/IRAC data. 41
Making Paschen Alpha images
a) F187N filter b) continuum (F190N) subtracted c) stars removed
HST figures from Wang et al., submitted Sept. 2009, MNRAS
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1.87 micron
image: we
detect
600,000
stars!
Note also
the dark
foreground
dust clouds
Paschen
alpha image
This shows
ionized
hydrogen
emission
near sites of
massive
stars
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a) The central few light years b) the “Pistol”,”Quintuplet” and “Sickle”,
c) The Arched filaments: linear features trace local magnetic field
“fingers”
sculpted by
winds from
hot stars in
Quintuplet
cluster
Location of black hole
(radio source known
as Sgr A*)
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Close-ups of Selected Nebulae from Pa alpha
mosaic of Galactic Center
Several of these are newly discovered
Horizontal bar in each figure shows 0.2 parsecs=0.65 light years
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Some results from the HST data
 Sharpest view ever of the Galactic Center in a large-scale map;
shows clear signs of interaction of massive stars with
environment: “fingers”, bubbles, outflows, etc.
 Amazing network of long, straight filaments seen in great detail
for first time in ionized gas; some of them follow magnetic field
lines;
 New compact nebulae discovered with young massive stars,
ranging from early to late stages of star formation
 Many candidate massive stars identified by bright Pa alpha
emission. Some are located OUTSIDE the 3 known clusters in
the GC; they may have been thrown out of parent clusters or
formed outside clusters
 Spectroscopic follow-up shows that many are exotic stars with
strong winds. They will explode as supernovae in the future
and will have a large impact on future star formation processes
in the GC.
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Chandra X-ray Observatory
Dr. Peter Edmonds
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An X-ray view of the Galactic Center
Chandra image
What do the colors mean in this image?
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red: lowest energy X-rays
green: medium energy X-rays
blue: highest energy X-rays
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OVERVIEW
Chandra image is a mixture of:
- hot gas, e.g. remnants of supernovas
- point sources of different types
- star clusters
SOME DETAILS
- Sagittarius A: contains the center of the
galaxy and a supermassive black hole
- Arches and Quintuplet are star clusters
- 1E 1743.1-2843 is a double star
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Sagittarius A*
-- The nearest supermassive black hole to us
-- Weighs about 4 million times the Sun
-- Area close to it is currently surprisingly dim
-- This area was much brighter in the past
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Sgr A*’s bigger, more active cousins
MS 0735
Hydra A
Black holes are “messy eaters”
-- Material around BH heats up and glows
close-up
(artist’s
impression)
-- Most of the inflowing material swallowed by BH
-- Some is flung outwards along jets/outflows
-- Sgr A* was more like this in the past
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Light echo from Sagittarius A*
-- Area near black hole was about 100,000
- times brighter 50 years earlier
-- Light reflected off clouds 50 yrs later
-- Mass equal to about that of Mercury
- was swallowed by the black hole
Artist’s impression of
what happened
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More information and graphics at:
http://chandra.harvard.edu/photo/2009/gcenter/
http://chandra.harvard.edu/photo/2003/0203long/
http://chandra.harvard.edu/photo/2007/gcle/
http://chandra.harvard.edu/photo/2009/hydra/
http://chandra.harvard.edu/photo/2006/ms0735/
General information about Chandra science and program:
http://chandra.harvard.edu/
Related Chandra products available:
Chandra Explores the Milky Way:
38x23" Poster, 8 1/2x 11" Litho,
6x8" Postcard, 2x8" Bookmark
http://chandra.harvard.edu/edu/request.html
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Final Thoughts
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Further Discussion
• Image Unveiling Google Group
– Should have received invitation
– Send email to Carolyn to add others
– groups.google.com/group/iya-image-unveiling
• Open discussion
– Ask questions
– Share ideas
– Discuss event planning
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