Object
Name: Subaru XMM-Newton Deep Field
Telescope: Subaru/Prime Focus
Instrument: Suprime-Cam
Filter: B (0.4 µm), R (0.7
µm), and z′ (0.9 µm)
Observation Date: August 2002
to January 2004
Filed of View: 1.3° x 1.3°
Image Orientation: North is up,
East is left
Position: R.A. 2h 18m, Dec. −5°
00′(J2000)
|
- Low
Resolution JPEG Image (116KB)
- High Resolution JPEG
Image (541KB) A color composite image of the
Subaru/XMM-Newton Deep Field. Five Suprime-Cam pointings
cover a 1.3° x 1.3° field centered at α
= 02h18m, δ = −05° 00′ (2000.0).
The images of the Moon and the full SXDS field have
the same scale. |
At a press conference held on 3 PM (JST), June 1, 2004,
in Tokyo Japan, the National Astronomical Observatory
of Japan (NAOJ) unveiled visible, X-ray, and radio wavelength
images of the Subaru/XMM-Newton Deep Survey, based on
data from the Subaru telescope, the European Space Agency's
(ESA) XMM-Newton Observatory and the Very Large Array.
SXDS provides a comprehensive population census of galaxies
from the early Universe to the present. The image release
coincides with the public release of SXDS's visible wavelength
scientific data from Subaru telescope. By inviting both
amateur and professional astronomers to explore this menagerie
of over a million galaxies, the SXDS survey team hopes
to maximize the scientific output from this remarkable
data set. The web site for the Subaru data is: http://soaps.naoj.org/
One of the fundamental goals of modern
astronomy is understanding the history of the Universe,
and in particular learning about the processes which shape
the formation and evolution of galaxies. It is possible
to observe these processes unfold by surveying galaxies
near and far over a large enough volume of the Universe
so that local variations in the physical properties and
the distribution of galaxies do not skew the results. The
Subaru/XMM-Newton Deep Survey (SXDS) is the first multi-wavelength
survey which has sufficient width and depth to accurately
characterize the properties of galaxies from the early Universe
to the present.
Both Subaru and XMM-Newton have devoted
a considerable amount of time to the SXDS. The XMM-Newton
observations represent the deepest and most sensitive wide
area X-ray survey ever carried out by XMM-Newton, totalling
over 400 thousand seconds of exposure time. The Subaru telescope
has stared at this field for over 200 hours, in
four different colors, revealing details which are a hundred
million times fainter than what can be seen with the naked
eye.
The large volume explored by the SXDS reveals
over a million galaxies, of all types and sizes, and in
a range of environments. The field is in the constellation
Cetus, which is visible in the southern evening sky from
most northern latitudes in the fall. The survey area is
1.3 square degrees, about seven times the area of the full
moon, and 850 times the survey area of the famous Hubble
Deep Field.
The SXDS also encompasses a broad wavelength
range from short wavelength X-rays to long wavelength radio
waves. The multi-wavelength data provide a detailed description
of the various types of galaxies that populate the Universe,
but they can be also be used to estimate distances to all
the galaxies - yielding a three dimensional map. Due to
the finite speed of light, we see more distant galaxies
as they were longer ago, and a 3D map shows us how galaxies
have changed with time. The history of galaxies places strong
constraints on cosmological models that determine the ultimate
fate of our Universe.
The SXDS team, an international collaboration
of astronomers from the National Astronomical Observatory
of Japan (NAOJ), the University of Tokyo, the Institute
of Space and Astronautical Science (ISAS), the University
of Durham, and Tohoku University working in close collaboration
with the XMM-Newton Survey Science Centre (SSC) led by the
University of Leicester, are already obtaining a wealth
of scientific results which will be the topic of discussion
at a science workshop in Kyoto, Japan, from June 3 - 5,
2004. For example, Dr. Tadayuki Kodama and others have been
able to show that larger galaxies form earlier and evolve
faster than smaller galaxies. A team led by Dr. Yoshihiro
Ueda have shown that galaxies with massive black holes in
their centers are distributed in a pattern with a characteristic
length scale of 100 million light years.
The observational data and object catalog
from the Subaru telescope that led to these discoveries
are now publicly available on the internet to astronomers
throughout the world. "By releasing the data beyond
our own group, we hope to realize the full scientific potential
of the data", says Dr. Kazuhiro Sekiguchi, coordinator
of the Japanese SXDS team. "With a large and comprehensive
data set like this, there are innumerable research possibilities.
We can encourage rigorous science by allowing other researchers
to test their observational or theoretical results against
ours. Other researchers -- professionals, amateurs, and
students -- can look at our data with a new perspective
and begin answering questions that we may have overlooked,
or don't have the time or human resources to address,"
says Dr. Sekiguchi.
Although the SXDS data are already a treasure
trove of information, their scientific value will multiply
when observations at wavelengths that complement the existing
data are complete. These include ultra-violet (0.1-0.3 microns),
near-infrared (1-2.5 microns), mid and far-infrared (3-160
microns) and sub-millimeter (250 to 1000 microns) imaging
and optical spectroscopy from a wide range of international
facilities. In five years, when the survey is scheduled
to conclude, SXDS should place strong constraints on the
cosmological models that determine the ultimate fate of
the Universe, providing insights into both the past and
the future.
Images:
References:
Kodama, T. et al. 2004
"Down-Sizing in Galaxy Formation at z~1 in the Subaru/XMM-Newton
Deep Survey (SXDS)"
Published in the May 2004 edition of the Monthly Notices
of the Royal Astronomical Society MNRAS, 350, 1005
The SXDS Home Page
http://www.naoj.org/Science/SubaruProject/SDS/
The European Space Agency's Press Release Site
http://www.esa.int/science/media
SXDS Team Member List
Contacts:
Dr. Kazuhiro Sekiguchi
(USA: 1) 808-934-5905
(Japan: 81) 90-4565-4275 (May 31 - June 5)
kaz at subaru.naoj.org
Dr. Masatoshi Imanishi
Subaru Telescope
(Japan: 81) 422-34-3538
imanishi at optik.mtk.nao.ac.jp
Additional Information:
- What are the scientific data now available?
- What other observations are being carried
out on the SXDS field?
- What other observations may be proposed?
- Why do you need a deep and wide survey?
- Why do you need to observe at multiple
wavelengths?
- What do the different wavelength images
show?
- How do you determine the distances to
the galaxies?
- What are some of the scientific results
of SXDS?
- Where can I find more information on the
various telescopes that may be used to observe the SXDS
field?
-
What are the scientific data
now available?
-
Optical imaging data from Subaru telescope's prime
focus camera Suprime-Cam (http://soaps.naoj.org/).
The data consists of B-band (central wavelength
0.4 microns), R-band (0.7 microns), i'-band (0.8
microns) and z'-band (0.9 microns) to a faintness
of 28.2 magnitudes in B-band, which is several hundred
million times fainter than what can be observed
by the naked eye.
-
X-ray imaging data from the EPIC camera (European
Photon Imaging Camera) onboard ESA's XMM-Newton
Observatory. The energy range of the X-ray data
is 0.5 to 10.0 keV, equivalent to wavelengths of
1/8000 to 1/400 microns.) These are available through
the XMM-Newton Science Archive (http://xmm.vilspa.esa.es/external/xmm_data_acc/xsa/index.shtml).
-
A catalog of all the astronomical objects detected
in the Subaru/Suprime-Cam data.
-
What other observations are
being carried out on the SXDS field?
-
Sub-millimeter observations with the Sub-millimeter
Common User Bolometer Array (SCUBA) on the James
Clerk Maxwell Telescope (JCMT) on Mauna Kea. The
SXDS field will be covered as part of the SCUBA
HAlf Degree Extragalactic Survey (SHADES). JCMT
will be dedicating a substantial fraction of its
total observing time over three years to carry out
SHADES, the largest ground based sub-millimeter
survey ever undertaken to date. The survey began
in 2002 and is expected to be completed in 2005.
-
The Balloon-borne Large Aperture Sub-millimeter
Telescope (BLAST) will take sub-millimeter data
of wavelengths inaccessible from the Earths surface
(250-500 microns).
-
Near-infrared imaging with Wide Field Infrared
Camera (WFCAM) on the United Kingdom Infrared Telescope
on Mauna Kea. The SXDS field will be included in
the Ultra Deep Survey (UDS) of the United Kingdom
Infrared Telescope Infrared Deep sky Survey (UKIDSS)
that will obtain deep wide field imaging in the
1 to 2.5 micron range. The UKIDSS survey will begin
in 2004, and approximately 300 nights of observing
will be dedicated to the UDS survey over 5 years.
-
Mid to far-infrared observations (3 - 160 microns)
with NASA's Spitzer Space Telescope will begin this
summer.
-
What other observations are
being proposed for the SXDS field?
-
Ultra-violet imaging using NASA's Galaxy Evolution
Explorer (GALEX) satellite. These observations would
cover the wavelength range of 0.1 to 0.3 microns.
-
Optical Spectroscopy and U-band (0.3 microns) imaging
with the Visible Imaging Multi-Object Spectrograph
(VIMOS) on the Melipal unit of the European Southern
Observatory's (ESO) Very Large Telescope.
-
It is possible that SXDS will be one of the first
survey fields for the Atacama Large Millimeter Array(ALMA)
once it is operational. ALMA will obtain data in
the 0.3-10 mm range (300 to 10000 microns).
-
Why do you need a deep and
wide survey?
Most deep surveys have been "pencil beam surveys" which
look deeply into the Universe in a small piece of sky.
Such surveys can show when different types of astronomical
objects came into existence, but not how typical they
are. The role different types of galaxies play in the
larger picture of the evolution of the Universe, and
their relationship to galaxies as they exist today remain
largely unknown.
On very large scales, the Universe appears to be homogenouse
and looks the same everywhere, but on scales of several
tens of million light years, the Universe appears to
have a foam like structure, with voids with few galaxies,
and filaments or sheets where galaxies congregate. A
pencil beam survey may point into a void or along a
filament, and may not reveal the typical property of
galaxies in the Universe. To understand the average
properties of the Universe, a survey needs to cover
scales that exceed several tens of millions of light
years. Of course, even observing the entire sky would
not be enough if the observations do not reveal the
faintest most distant galaxies. Deep observations are
necessary to study how galaxies have changed over time.
To study the history of galaxies, it is important to
balance the size of the survey field and the depth of
the observations. The SXDS survey field corresponds
to a piece of the Universe about 150 million times 150
million light years in area in the Universe of 5 to
13 billion years ago. It samples of a volume of several
billion cubic light years.
-
Why do you need to observe
at multiple wavelengths?
Almost all our knowledge of the Universe is derived
from the measurement of light. Also known as electromagnetic
radiation, light has different names depending on its
wavelength: Gamma-rays, X-rays, UV-rays, visible light,
infrared light, microwaves, sub-millimeter waves and
radio waves (from short wavelength/high frequency/high
energy to long wavelength/ low frequency/ low energy).
At different wavelengths, light carries distinct information
about its source such as distance, movement, temperature,
density and chemical composition. Using modern technologies
such as senstive infrared detectors and artificial satellites,
astronomers are now able to explore the Univserse at
most wavelengths.
-
What do the different wavelength
images show?
Over a thousand X-ray sources are found in the XMM-Newton
images. Some of them are nearby stars with a very active
corona that radiates in the X-ray domain, but the largest
majority are far flung active galaxies hiding powerful
black holes in their nucleus. Other sources include
distant clusters of galaxies, located up to eight thousand
light years away. Since X rays travel in space at a
finite speed, XMM-Newton gives us a view of these galaxies
when they were much younger and less evolved than now.
By comparing these images with those of nearby galaxies,
astronomers can infer how they have evolved in the course
of the last several thousand million years, or about
three quarters of the life of the Universe.
The Subaru images of the SXDS field show a million
galaxies of different colors in diverse envoronments.
The visible color of a galaxy depend primarily on the
age of its stars and its distance. A distant cluster
of galaxies can easily be identified by the uniformly
red color and small apparent size of their members.
Many galaxies appear to belong to groups and may galaxies
appear to be undergoin gravitational interactions with
other galaxies. The colors, distribution, and appearance
of the galaxies allow astronomers to trace how galaxies
have been evolving with time.
-
How do you determine the distances
to the galaxies?
The best way to determine the distance to a far away
galaxy is spectroscopy. Spectroscopy involves dissecting
light into different wavelengths and making a spectrum.
Different molecules have characteristic wavelengths
at which they emit and absorb light. When we observe
a moving object, these characteristic wavelengths appear
to shift in proportion to the speed at which they are
moving away or towards us. When something is moving
away from the observer, the wavelength shifts to longer
wavelengths and appears redder. This is called a "redshift".
Due to the expansion of the Universe, the farther away
a galaxy is, the faster it is moving even further away.
This means that a measurement of the redshift is a measurement
of the distance to a galaxy or any other distant astronomical
object.
Spectroscopy of very distant and faint galaxies is
technologically very challenging, however. For example,
it takes an hour of observing with the 8.2 meter effective
aperture Subaru telescope to obtain a usable spectra
of an object with a brightness of 23 magnitudes in visible
light (several million times fainter than what can be
observed with the naked eye). The faintest galaxies
detected in the SXDS are 100 times fainter.
As an alternative, astronomers use a technique called
"photometric redshift." As in the case with spectroscopy,
shifts in characteristic features in a spectrum are
sought as a measure of redshift, but instead of a fine
dissection, the total amount of light in a specific
wavelength ranges is measured by taking images of a
galaxy with different filters. Although photometric
redshifts are less precise and less accurate than spectroscopic
redshifts, they are much easier to obtain for faint
galaxies. In a large survey, the uncertainties in scientific
conclusions based on the use of photometric redshifts
is reduced by the number of galaxies that are under
study.
-
What are some of the scientific
results of SXDS?
Dr. Tadayuki Kodama used the visible data from Subaru/Suprime-Cam
to select galaxies 8 billion light years away (in other
words galaxies as they were 8 billion years ago when
the universe was less than half of its current age)
to see how they formed and how they may have evolved
into galaxies of the present day Universe. He found
that bright and massive galaxies and fainter and less
massive galaxies form and evolve differently.
Galaxies that are heavier than 80 billion Suns have
reddish colors indicating that they are made of old
stars. Their distribution in space and the distribution
of stars within them are comparable to elliptical galaxies
in the present day universe. This implies that most
elliptical galaxies must have already existed 8 billion
years ago. On the other hand, galaxies with masses less
than 10 billion Suns all had blueish colors indicative
of young stars. These galaxies were still actively forming
stars 8 billion years ago.
Such a scenario in which heavier galaxies evolve faster
than lighter galaxies is called "down sizing". However,
this scenario may contradict the currently most successful
cosmological model of a universe filed with cold dark
matter in which smaller objects form first. (This is
called the bottom-up hypothesis.) These new results
may force astronomers to look for a new physical mechanism
that makes heavier objects form faster than our current
cosmological model of the universe.
There will soon be near-infrared images of the SXDS
field. By combining near-infrared information with the
visible it will be possible to extend a similar analysis
to more distant galaxies. This will allow scientists
if down-sizing holds true at earlier times. it may also
be possible to look back to the time when the higher
mass galaxies were actively forming stars.
- Where can I find more information
on the various telescopes that may be used to observe
the SXDS field?
- ALMA (Atacama Large Millimeter Array)
http://www.alma.nrao.edu/
(NRAO site)
http://www.eso.org/projects/alma/
(ESO site)
http://www.nro.nao.ac.jp/~lmsa/
(NAOJ site; Japanese only)
A large millimeter and sub-millimeter telescope combining
64 sensitive antennae and 16 supersensitive antennae
each 12 meters in diameter. Now under construction in
a high plateau in Chile 5000 meters in altitude. A collaboration
of the United States , several European nations and
Japan.
- BLAST (Balloon-borne Large-Aperture Sub-millimeter Telescope)
http://chile1.physics.upenn.edu/blastpublic/
A balloon-borne sub-millimeter telescope with a 2-meter
primary mirror developed by astronomers from the United
Kingdom, the United States, mexico, and Canada.
- GALEX (Galaxy Evolution Explorer)
http://www.galex.caltech.edu/
A UV satellite launched by NASA in April 2003.
- JCMT (James Clerk Maxwell Telescope)
http://www.jach.hawaii.edu/JACpublic/JCMT/
A sub-millimeter telescope with a 15 meter aperture
on Mauna Kea, Hawaii. Operated by the Joint Astronomy
Centre, a collaboration of the United Kingdom, the Netherlands,
and Canada.
- Spitzer Space Telescope
http://www.spitzer.caltech.edu/
An infrared telescope launched by NASA in August 2003.
One of NASA's four great space observatories which also
include the Hubble Space Telescope, the Compton Gamma-ray
Observatory and the Chandra X-ray Observatory.
- Subaru Telescope
http://www.naoj.org/
An 8.2 meter effective aperture optical-infrared telescope
operated by the National Astronomical Observatory of
Japan.
- UKIRT (United Kingdom Infrared Telescope)
http://www.jach.hawaii.edu/JACpublic/UKIRT/
A 3.8m infrared telescope on Mauna Kea, Hawaii. The
largest telescope that specializes in infrared observing.
Operated by the Joint Astronomy Centre, a collaboration
of the United Kingdom, the Netherlands, and Canada.
- VLA (Very Large Array)
http://www.vla.nrao.edu/
A radio telescope in Socorro, New Mexico, consisting
of 27 antennae each 25 meters in diameter.
- XMM-Newton (X-ray Multi-Mirror Mission - Newton)
http://xmm.vilspa.esa.es/
An X-ray satellite launched by ESA in December , 1999.
It has the largest aperture of all telescopes sensitive
to X-rays in the 0.5-10 keV range (1/8000 to 1/400 microns).
June 1, 2004 |
