Una astrónoma Deidre Hunter en el Observatorio Lowell, quien estudia como las estrellas se forman en galaxias "enanas", que pueden proporcionar la perspicacia(idea) en el nacimiento de las primeras estrellas después del Big Bang. Aquí, una imagen realzada por color óptica de la galaxia DDO 87 en la constelación la Osa Mayor muestra las estrellas. Fuente: Observatorio Lowell .Cuando usted en su imaginación una galaxia , esto es a menudo una espiral con la estructura magnífica - mucho tiempo, la acción de arremolinar, los brazos lechosos y brillantes blancas estrellas, nubes y mucho gas.
En el Observatorio ¨Lowell" la astrónoma Deidre Hunter ha pasado la mayor parte de los 17 años pasados estudiando metódicamente las galaxias que usted no podría esperar - galaxias pequeñas, difusas: irregulars enanas - para aprender todo ella puede sobre la formación de estrella y lo que esto puede decir a sus colegas y ella sobre el nacimiento de las primeras estrellas después del Big Bang.
En la Fundación Nacional de Ciencias- (NSF) crearon el proyecto llamado: LITTLE THINGS--for Local Irregulars That Trace Luminosity Extremes (LITTLE) and The HI Nearby Galaxy Survey (THINGS) --Un grupo de cazadores o astrónomos están formando mapas de esas pequeñas , difusas y enigmáticas galaxias enanas, que les permiten discernir los muchos procesos de la formación de estrellas.
" La formación de estrella en galaxias enanos hoy es similar a la formación de estrella a raíz del Big Bang, " dijo Hunter. " Las estrellas se forman de las nubes de gas. Nuestra búsqueda debe entender(calcular) lo que las nubes moleculares en estas galaxias irregulares son, y los procesos aquellas estrellas de forma. "
El equipo de científicos del The LITTLE THINGS están estudianto cercanamente un grupo de 41 galaxias enanas irregulares a traves de los lentes de los obasevatorios que han aportado datos. Entonces se está siguiendo a la uno de los grupos como: DDO 75, has 1/3500 que es la mas cercana a nuestra Vía Láctea . Otra galaxia es: Leo T, que fue recientemente descubierta en un grupo local de galaxias cercanas a nuestra Vía Láctea.
" Leo T es comparable en el resplandor para un racimo muy grande de estrellas que contiene varios millones de estrellas; en contrraste la Vía Láctea contiene aproximadamente 300 mil millones de estrellas, " dijo Hunter. Algunas galaxias en nuestra área de la muestra no son mucho más brillantes que un racimo de estrella grande. "
Versión de la NATIONAL SCIENCE FOUNDATION
In English:
Discovery
Tiny Galaxies Reveal How First Stars Formed:
Lowell Observatory astronomer Deidre Hunter and her team studies small, diffuse galaxies to learn about star formation in those regions and, perhaps, shed light on the birth of the first stars after the Big Bang
Color-enhanced optical image of the galaxy DDO 87 in the constellation Ursa Major showing stars.Credit and Larger Version
February 25, 2010
When you picture a galaxy in your mind's eye, it's often a spiral with magnificent structure--long, swirling, milky-white arms of stars and gas.
Lowell Observatory astronomer Deidre Hunter has spent most of the last 17 years methodically studying galaxies that you might not expect--small, diffuse galaxies: the dwarf irregulars--to learn all she can about star formation and what that can tell her colleagues and herself about the birth of the first stars after the Big Bang.
In a National Science Foundation- (NSF) funded project called LITTLE THINGS--for Local Irregulars That Trace Luminosity Extremes (LITTLE) and The HI Nearby Galaxy Survey (THINGS) --Hunter's team is mapping the gasses in these diffuse, enigmatic galaxies to discern the many processes of star formation.
"Star formation in dwarfs today is similar to star formation right after the Big Bang," Hunter said. "Stars form out of clouds of gas. Our quest is to figure out what the molecular clouds in these irregular galaxies are, and the processes that form stars."
The LITTLE THINGS team is closely studying 41 dwarf-irregular galaxies through the lens of numerous data sets. And the galaxies are small, relatively speaking. One, DDO 75, has 1/3500 the mass of the Milky Way. Another, Leo T, was recently discovered in the Local Group of galaxies, the closest neighbors to our own Milky Way.
"Leo T is comparable in brightness to a large star cluster that contains several million stars; in contrast, the Milky Way contains about 300 billion stars," Hunter said. Some of the galaxies in our sample area are not much brighter than a large star cluster."
The process of star formation is very inefficient. Some 50 to 90 percent of the gas present in star-forming molecular clouds, including the gas in the tiny irregular galaxies, remains after stars form.
"This produces the nebulae," Hunter said. "They are like signposts that say, 'massive stars are found here.' In a general sense, it's like weather clouds on Earth. You need these molecular clouds that form out of the ubiquitous atomic hydrogen gas to precipitate stars."
Hunter added that there are probably multiple processes going on, which adds to the complexity and time-intensive nature of the LITTLE THINGS study. In the dwarf galaxies, there's star-induced star formation. There's also turbulence. "It's not just density, but also the motions of the gas," Hunter says.
The data sets Hunter and her colleagues are using include optical-wavelength data Hunter already collected and analyzed using research telescopes at Lowell's Anderson Mesa facility near Flagstaff, Ariz. But some of the new, key data are in radio wavelengths, and they come from NSF's Very Large Array (VLA) located west of Socorro, N.M.
In May 2007, Hunter was invited to give a talk at the VLA. Afterwards, a scientist with the facility suggested she put in a large proposal, that is, a proposal for a large amount of VLA telescope time. She and her team had been unsuccessful in previous smaller requests for the needed hours, but this time, the team was rewarded: about 400 hours to study a subsample of dwarf galaxies that represent a range of characteristics.
One of Hunter's collaborators, Lowell predoctoral student Megan Jackson, is looking at the motions of the stars, their velocities and their rotation. Fellow Lowell predoc Hongxin Zhang is looking closely at existing ultraviolet and optical data sets from the galaxies, helping define their star-formation histories.
Zhang has been limited with his current sets of infrared data, so he is embarking on an observing program using a special instrument called Mimir attached to the 1.8-meter Perkins Telescope at Anderson Mesa, also at Lowell. The Perkins is operated through a partnership with Boston University, and Mimir is a powerful, $2.5-millon infrared instrument built by a team led by Dan Clemens of Boston University.
As for the massive amount of VLA radio data, much has to be collected, sorted and analyzed. Kim Herrmann, a Lowell Observatory postdoctoral fellow and part of the LITTLE THINGS team, is reducing the VLA data.
"When Kim came to Flagstaff, she had never dealt with radio interferometric data," Hunter said. "But she quickly came up to speed and has now become a local expert. She has calibrated more LITTLE THINGS data than any other person on the team, and she is exactly the kind of person we need on the team. Right now, we're in this 'grunge' phase of the project; it is very tedious. If all goes well, and I'm not distracted by other tasks, it takes me one month per galaxy to reduce the VLA data."
The extensive data are poised to re-shape astronomers' understanding of star formation. "The crux of the problem is that the standard models for galaxies don't work for dwarfs. Dwarfs should not be forming stars at all."
But indeed they are. They are forming stars even at their outer edges. The little-understood portions of dwarf irregular galaxies are what intrigue Hunter most of all.
"It's the outer disks--because they are so extreme," she said. "These are such extreme environments that they are very stringent tests for star formation."
-- Steele Wotkyns, Lowell Observatory, steelewot3@gmail.com
This Behind the Scenes article was provided to LiveScience in partnership with the National Science Foundation.
Investigators:
Deidre Hunter
Trisha Ashley
Sandipan Basu
Dan Clemens
Bruce Elmegreen
Kim Herrmann
Megan Jackson
Se-Heon Oh
Michael Rupen
Caroline Simpson
David Westpfahl
Lisa Young
Hongxin Zhang
Related Institutions/Organizations:
Lowell Observatory
Boston University
Florida International University
IBM Thomas J Watson Research Center
New Mexico Institute of Mining and Technology
Locations:
Arizona
Florida
Massachusetts
New Mexico
New York
Related Awards#0707563 Collaborative Research: Star Formation in Subcritical Environments #0707426 Collaborative Research: Star Formation in Subcritical Environments #0707468 Collaborative Research: Star Formation in Subcritical Environments #0707835 Collaborative Research: Star Formation in Subcritical Environments
Related Websites
LiveScience.com: Behind the Scenes: Tiny Galaxies Reveal How First Stars Formed: http://www.livescience.com/space/dwarf-galaxy-star-formation-bts-100205.html
The LITTLE THINGS Survey:
http://www.lowell.edu/users/dah/littlethings/
Mimir: A Near-Infrared Wide-Field Imager, Spectrometer and Polarimeter: http://people.bu.edu/clemens/mimir/index.html
Boston University at Lowell Observatory: http://www.nsf.gov/cgi-bin/good-bye?http://www.bu.edu/iar/research/lowell/
Guillermo Gonzalo Sánchez Achutegui
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ayabaca@hotmail.com
ayabaca@yahoo.com
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