Andrew Yee[_1_]
January 8th 08, 07:57 PM
Office of Public Information
Eberly College of Science
Penn State University
University Park, Pennsylvania
CONTACTS:
Caryl Gronwall: (office) 814 865 2918
Barbara K. Kennedy (PIO): 814-863-4682
8 January 2008
Penn State, Rutgers Astronomy Teams Discover Ancestors of Galaxies Like the
Milky Way
Astronomers at Penn State and Rutgers universities have discovered galaxies
in the distant universe that are ancestors of spiral galaxies like our Milky
Way. These ancient objects, some of the first galaxies ever to form, are
being observed as they looked when the universe was a mere two-billion years
old. Today, scientists peg the age of the universe at 13.7-billion years, so
light from these galaxies traveled almost 12 billion years to reach Earth.
The discovery by a team led by Caryl Gronwall, senior research associate in
Penn State's Department of Astronomy & Astrophysics, and Eric Gawiser,
assistant professor in the Department of Physics and Astronomy in the
Rutgers School of Arts and Sciences, will be presented at the annual meeting
of the American Astronomical Society (AAS) in Austin, Texas, to be held from
January 7 to 11, 2008.
The newly discovered galaxies are quite small -- one-tenth the size and
one-twentieth the mass of our Milky Way. They also have fewer stars -- only
one-fortieth as many as are in the Milky Way. From ground-based telescopes,
they look like individual stars in size. Recent images made by the Hubble
Space Telescope, however, reveal them as regions of active star formation.
"Finding these objects and discovering that they are a step in the evolution
of our galaxy is akin to finding a key fossil in the path of human
evolution," Gawiser said. The team led by Gronwall and Gawiser determined
that these galaxies were fertile breeding grounds for new stars, which
burned hot and bright. These stars ionized the hydrogen atoms around them,
stripping them of their electrons and causing them to emit a tell-tale sharp
band of ultraviolet light known as Lyman alpha. The researchers also noted
that several of these galaxies, sometimes 10 or more, pulled together over
the ensuing few-billion years to form a single spiral galaxy.
"The Hubble Space Telescope has delivered striking images of these early
galaxies, with 10 times the resolution of ground-based telescopes," Gronwall
said. "They come in a variety of shapes -- round, oblong, and even somewhat
linear -- and we are starting to make precise measurements of their sizes."
Gawiser will preview Gronwall's early Hubble image analyses at the AAS
meeting, and the research team will publish the complete results later in a
scientific journal.
The astronomers discovered these galaxies as part of a five-year-old census
of galaxies in the early universe, a project called MUSYC (Multi-Wavelength
Survey by Yale and Chile). Gawiser, while a National Science Foundation
(NSF) astronomy and astrophysics postdoctoral fellow at Yale, initiated a
search for several types of galaxies that could be precursors of Milky
Way-type spirals; Gronwall led an investigation into the luminosity,
density, and distribution of the distinctive Lyman-alpha emitters. The
team's statistical analyses and computer simulations of how galaxies cluster
led them to the conclusion they first reported in the 10 December 2007 issue
of the Astrophysical Journal in a paper titled "Lyman alpha emitters are the
ancestors of spiral galaxies." "We knew by our understanding of cosmological
theory that spiral galaxies had to evolve from low-mass galaxies such as
these," Gawiser said. "The challenge was to actually find them. We'd seen
other early universe galaxies, but they were bigger and destined to evolve
into elliptical galaxies, not spirals."
The astronomers undertook four types of observations to find and
characterize the objects they were seeking. They performed the first step --
actually finding amid all the visible objects of deep space those galaxies
that emit ultraviolet light in the Lyman-alpha range -- using the Blanco
four-meter telescope at the National Science Foundation's Cerro Tololo
Inter-American Observatory in Chile. To measure their distance, they used
the Magellan Telescope at Las Campanas Observatory, also in Chile, to
measure redshift -- an effect that shows how fast an object is receding from
view due to a rapidly expanding universe. (The redshift at which they
studied these galaxies is 3.1.) To determine how many stars are in the
galaxies, they used the NASA Spitzer Space Telescope's Infrared Array
Camera. And to determine how big the galaxies are, they used the NASA Hubble
Space Telescope's Advanced Camera for Surveys.
"Astronomy has long used a model where big surveys are followed by detailed
studies of the interesting objects they find," said Nigel Sharp, program
officer in NSF's Division of Astronomical Sciences. "This work nicely
couples the large-area, wide-field view of our ground-based telescope with
the sharp focus of the Hubble to probe to the faintest light levels. This
team has come the closest yet to finding young galaxies that resemble our
own Milky Way in its infancy."
Additional study participants are Robin Ciardullo at Penn State; Harold
Francke and Paulina Lira at Universidad de Chile; C. Megan Urry, Pieter van
Dokkum and Shanil Virani at Yale; Kamson Lai, Giovanni Fazio and Jia-Sheng
Huang at Harvard, Kevin Schawinski at Oxford; Alvaro Orsi, Felipe
Barrientos, Leopoldo Infante and Nelson Padilla at Pontificia Universidad
Catica de Chile; Ryan Quadri and Edward Taylor at Leiden Observatory; John
Feldmeier at Youngstown State; Ezequiel Treister at the European Southern
Observatory; and Guillermo Blanc at the University of Texas at Austin.
Additional members of MUSYC are listed at http://www.astro.yale.edu/MUSYC .
The research was funded by grants from NSF, including an Astronomy and
Astrophysics Postdoctoral Fellowship, and from NASA's Hubble Space Telescope
and NASA's Spitzer Space Telescope. The Cerro Tololo Inter-American
Observatory is part of the National Optical Astronomical Observatory, funded
by NSF and operated by the Association of Universities for Research in
Astronomy. The Spitzer Space Telescope is managed by the NASA Jet Propulsion
Laboratory and CalTech. The Hubble Space Telescope is managed by the NASA
Goddard Space Flight Center and science programs are managed by the Space
Telescope Science Institute.
[NOTE: Images supporting this release are available at
http://www.science.psu.edu/alert/Gronwall1-2008.htm ]
Eberly College of Science
Penn State University
University Park, Pennsylvania
CONTACTS:
Caryl Gronwall: (office) 814 865 2918
Barbara K. Kennedy (PIO): 814-863-4682
8 January 2008
Penn State, Rutgers Astronomy Teams Discover Ancestors of Galaxies Like the
Milky Way
Astronomers at Penn State and Rutgers universities have discovered galaxies
in the distant universe that are ancestors of spiral galaxies like our Milky
Way. These ancient objects, some of the first galaxies ever to form, are
being observed as they looked when the universe was a mere two-billion years
old. Today, scientists peg the age of the universe at 13.7-billion years, so
light from these galaxies traveled almost 12 billion years to reach Earth.
The discovery by a team led by Caryl Gronwall, senior research associate in
Penn State's Department of Astronomy & Astrophysics, and Eric Gawiser,
assistant professor in the Department of Physics and Astronomy in the
Rutgers School of Arts and Sciences, will be presented at the annual meeting
of the American Astronomical Society (AAS) in Austin, Texas, to be held from
January 7 to 11, 2008.
The newly discovered galaxies are quite small -- one-tenth the size and
one-twentieth the mass of our Milky Way. They also have fewer stars -- only
one-fortieth as many as are in the Milky Way. From ground-based telescopes,
they look like individual stars in size. Recent images made by the Hubble
Space Telescope, however, reveal them as regions of active star formation.
"Finding these objects and discovering that they are a step in the evolution
of our galaxy is akin to finding a key fossil in the path of human
evolution," Gawiser said. The team led by Gronwall and Gawiser determined
that these galaxies were fertile breeding grounds for new stars, which
burned hot and bright. These stars ionized the hydrogen atoms around them,
stripping them of their electrons and causing them to emit a tell-tale sharp
band of ultraviolet light known as Lyman alpha. The researchers also noted
that several of these galaxies, sometimes 10 or more, pulled together over
the ensuing few-billion years to form a single spiral galaxy.
"The Hubble Space Telescope has delivered striking images of these early
galaxies, with 10 times the resolution of ground-based telescopes," Gronwall
said. "They come in a variety of shapes -- round, oblong, and even somewhat
linear -- and we are starting to make precise measurements of their sizes."
Gawiser will preview Gronwall's early Hubble image analyses at the AAS
meeting, and the research team will publish the complete results later in a
scientific journal.
The astronomers discovered these galaxies as part of a five-year-old census
of galaxies in the early universe, a project called MUSYC (Multi-Wavelength
Survey by Yale and Chile). Gawiser, while a National Science Foundation
(NSF) astronomy and astrophysics postdoctoral fellow at Yale, initiated a
search for several types of galaxies that could be precursors of Milky
Way-type spirals; Gronwall led an investigation into the luminosity,
density, and distribution of the distinctive Lyman-alpha emitters. The
team's statistical analyses and computer simulations of how galaxies cluster
led them to the conclusion they first reported in the 10 December 2007 issue
of the Astrophysical Journal in a paper titled "Lyman alpha emitters are the
ancestors of spiral galaxies." "We knew by our understanding of cosmological
theory that spiral galaxies had to evolve from low-mass galaxies such as
these," Gawiser said. "The challenge was to actually find them. We'd seen
other early universe galaxies, but they were bigger and destined to evolve
into elliptical galaxies, not spirals."
The astronomers undertook four types of observations to find and
characterize the objects they were seeking. They performed the first step --
actually finding amid all the visible objects of deep space those galaxies
that emit ultraviolet light in the Lyman-alpha range -- using the Blanco
four-meter telescope at the National Science Foundation's Cerro Tololo
Inter-American Observatory in Chile. To measure their distance, they used
the Magellan Telescope at Las Campanas Observatory, also in Chile, to
measure redshift -- an effect that shows how fast an object is receding from
view due to a rapidly expanding universe. (The redshift at which they
studied these galaxies is 3.1.) To determine how many stars are in the
galaxies, they used the NASA Spitzer Space Telescope's Infrared Array
Camera. And to determine how big the galaxies are, they used the NASA Hubble
Space Telescope's Advanced Camera for Surveys.
"Astronomy has long used a model where big surveys are followed by detailed
studies of the interesting objects they find," said Nigel Sharp, program
officer in NSF's Division of Astronomical Sciences. "This work nicely
couples the large-area, wide-field view of our ground-based telescope with
the sharp focus of the Hubble to probe to the faintest light levels. This
team has come the closest yet to finding young galaxies that resemble our
own Milky Way in its infancy."
Additional study participants are Robin Ciardullo at Penn State; Harold
Francke and Paulina Lira at Universidad de Chile; C. Megan Urry, Pieter van
Dokkum and Shanil Virani at Yale; Kamson Lai, Giovanni Fazio and Jia-Sheng
Huang at Harvard, Kevin Schawinski at Oxford; Alvaro Orsi, Felipe
Barrientos, Leopoldo Infante and Nelson Padilla at Pontificia Universidad
Catica de Chile; Ryan Quadri and Edward Taylor at Leiden Observatory; John
Feldmeier at Youngstown State; Ezequiel Treister at the European Southern
Observatory; and Guillermo Blanc at the University of Texas at Austin.
Additional members of MUSYC are listed at http://www.astro.yale.edu/MUSYC .
The research was funded by grants from NSF, including an Astronomy and
Astrophysics Postdoctoral Fellowship, and from NASA's Hubble Space Telescope
and NASA's Spitzer Space Telescope. The Cerro Tololo Inter-American
Observatory is part of the National Optical Astronomical Observatory, funded
by NSF and operated by the Association of Universities for Research in
Astronomy. The Spitzer Space Telescope is managed by the NASA Jet Propulsion
Laboratory and CalTech. The Hubble Space Telescope is managed by the NASA
Goddard Space Flight Center and science programs are managed by the Space
Telescope Science Institute.
[NOTE: Images supporting this release are available at
http://www.science.psu.edu/alert/Gronwall1-2008.htm ]