A stunning image of M31 captured by Subaru Telescope's Hyper Suprime-Cam
(HSC) displays the fruits of international collaboration and
technological sophistication aligned with cutting-edge science. In
addition to providing information about a nearby galaxy that resembles
our own, this image demonstrates HSC's capability to fulfill Subaru
Telescope's intention of producing a large-scale survey of the Universe.
The combination of a large mirror, a wide field of view, and sharp
imaging represents a giant step into a new era of observational
astronomy and will contribute to answering questions about the nature of
dark energy and matter. It marks another successful stage in HSC's
commissioning process, which involves checking all of HSC's capabilities
before it is ready for open use.
Figure 1: M31 captured by HSC.
(Credit: HSC Project / NAOJ)
HSC's first beautiful image of M31 gives an answer to
the question: Does HSC really deliver what it promises in terms of
image quality? It displays a resounding "yes" by demonstrating the
sharp, detailed resolution of which the camera is capable across the
wide field of view that it embraces. The image indicates why this
powerful instrument is unique within the domain of current observational
technology, enabling high-resolution images from observations with a
large primary mirror (8.2 m) and large field of view (1.5 degrees).
M31, also known as the Andromeda Galaxy, is the
spiral galaxy nearest to our own Milky Way Galaxy, 2.5 million light
years from Earth. It is one of the brightest objects listed in the
Messier catalog and has garnered the attention of observers since 964
A.D., when the Persian astronomer al-Sufi wrote about it. Messier
catalogued it as M31 in 1764, 800 years later, and it continues to
intrigue the public and astronomers alike. It is visible to the naked
eye on moonless nights, even in areas with moderate light pollution.
Astronomers find it particularly interesting, because it is quite
similar to the Milky Way Galaxy and can provide valuable information
about how our own galaxy formed. Since the galactic center is visible,
it is possible to investigate how star formation varies in relation to
distance from the center of the galaxy. Of particular significance in
HSC's image is the consistently high quality of resolution of the
objects throughout the frame, which surpasses the clear resolution of
the image of the Andromeda Galaxy captured by the Subaru Prime Focus
Camera (Suprime-Cam) in 2001 (Figure 2). ("Sister Star World 2.5 Million Light-Years Away").
Although HSC's field of view is seven times larger than that of its
predecessor, Suprime-Cam, there is no degradation of the image at the
edges.
HSC's image of M31 gives tangible evidence of
features that HSC's developers had envisioned as early as 2002, when
astronomers at Subaru Telescope tried to anticipate the future demands
of cosmology-related research that existing technology could not handle.
Their foresight led to the establishment of the HSC Project in 2008
and was a catalyst for international collaboration among major research
partners-- National Astronomical Observatory of Japan (NAOJ Japan),
Kavli Institute for the Physics and Mathematics of the Universe (Kavli
IPMU, Japan, from 2007), the School of Science at the University of
Tokyo (Japan), KEK (High Energy Accelerator Research Organization,
Japan), Academia Sinica Institute of Astronomy and Astrophysics (ASIAA,
Taiwan, from 2005), Princeton University (U.S.A., from 2007)--and with
outstanding companies from industry--Hamamatsu Photonics K.K., Canon
Inc., and Mitsubishi Electric Corporation.
The cooperation of so many institutions and
organizations resulted in the completion and installation of the major
components of HSC (116 charge-coupled devices, the seven, high-optical
quality lenses of the wide field corrector in an innovative ceramic lens
barrel, and the prime focus unit) onto the Subaru Telescope on August
16-17, 2012 ("Hyper Suprime-Cam Ushers in a New Era of Observational Astronomy").
Scientists at Princeton University have worked closely with their
Japanese colleagues at NAOJ and Kavli IPMU on the software pipelines
that are analyzing terabytes of raw data, which not only yield beautiful
images but also precise measurements of the brightness, position and
shape of every galaxy and star.
Figure 3: Views of HSC from below and above the top
ring. The image on the left shows the position of HSC (without the
filter exchange unit or FEU) when mounted on the inner, top ring of the
Subaru Telescope. This location is at prime focus, and HSC is 15 meters
above the primary mirror. (Credit: NAOJ) The image on the right is a
close-up of the top part of HSC with the FEU installed on it. (Credit:
ASIAA)
The more recently installed filter exchange unit
(FEU) is another example of the fruit of international collaboration.
ASIAA (Taiwan) received valuable input from NAOJ about the overall
concept of the unit, its requirements, and definition of the interface
with the camera. Regular meetings between the partners every few months
enhanced the development of the unit. ASIAA and their domestic
partner, the Aeronautical Systems Research Division of Taiwan's
Chung-Shan Institute of Science and Technology (ASRD), developed and
delivered the unit, the building of which took place mainly in Taiwan.
As a result of these combined efforts, the completed FEU was ready to
use on HSC for the observation of M31. The unit can store up to six
filters and position one of them in the optical path. During the
exchange process, a motorized cart grasps the required filter and pushes
it from the jukebox storing its filters. FEU's operation is fully
automated, and it can complete the entire exchange sequence in 14
minutes, a relatively short period of time for such sophisticated, heavy
technology. HSC's filters in the FEU help the implementation of HSC's
science goals by providing a multi-color data set.
Dr. Satoshi Miyazaki, director of the HSC Project,
expressed his deep satisfaction with the high performance of HSC, which
shows the significant role that it will play as a tool to realize the
scientific objectives envisioned in its design: "The sharp resolution in
the current image augurs the instrument's capabilities for capturing
weak lensing, which is central to HSC's scientific goals of surveying
the parameters and properties of dark matter and dark energy in the
Universe as well as exploring the causes of the accelerating expansion
of the Universe. In essence, this means an expansion of applications
that derive from the instrument's capacity to make nearly invisible,
distant faint objects, visible and for bringing dark energy and dark
matter into the arena of scientific identification and investigation.
The design of HSC facilitates this task with faster survey speed and
tenfold expansion of file size, while maintaining quality equivalent to
Suprime Cam's."
Dr. Masahiro Takada (Kavli IPMU), the chair of the
HSC science working group, enthusiastically affirmed how much the
performance of HSC expands the range of potential scientific research:
"This first image from HSC is truly exciting. We can now start the
long-awaited, largest-ever galaxy survey for understanding the
evolutionary history and fate of the expanding Universe. A "cosmic
census", i.e. a large-scale imaging survey of every galaxy over a wide
solid angle in the sky and in sufficient depth to probe the distant
Universe, will include the detailed measurement of hundreds of millions
of galaxy shapes and assessment of the effects of gravitational lensing.
Such data will allow scientists to map the distribution of dark
matter, constrain the nature of dark energy, and search for baby
galaxies that were just born in the early Universe."
Astronomers have long dreamed of being able to image
billions of galaxies across the sky. As HSC proceeds along a successful
path of testing and demonstrates its capabilities, that dream is
becoming a reality.
Funding for the HSC Project was provided in part by
the following grants: Grant-in-Aid for Scientific Research (ID 15340065)
to S. Miyazaki (NAOJ); Grant-in-Aid for Scientific Research on Priority
Areas (ID 18072003) to H. Karoji (first at NAOJ, then at Kavli IPMU);
and the Funding Program for World-Leading Innovative R&D on Science
and Technology (FIRST) entitled, "Uncovering the Origin and Future of
the Universe-ultra-wide-field imaging and spectroscopy reveal the nature
of dark matter and dark energy" to H. Murayama (Kavli IPMU).
