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Astronomers release most ultraviolet light shots from nearby galaxies



This image shows the galaxy NGC 6744, about 30 million light-years away. It is one of 50 galaxies observed in the Legacy ExtraGalactic UV Surveys (LEGUS) of the Hubble Space Telescope. It is the sharpest and most comprehensive ultraviolet photograph of star-forming galaxies in the nearby universe, providing a rich source for understanding the complexities of star formation and galaxy evolution. The image is a composite that uses both ultraviolet and visible light and was captured using Hubble's Wide Field Camera 3 and Advanced Camera for Surveys. Credit: NASA, ESA and the LEGUS team

An international team of astronomers is taking advantage of NASA's Hubble Space Telescope's unprecedented sharpness and spectral range to publish the most comprehensive high-resolution ultraviolet light measurements of near star-forming galaxies.

The researchers combined new Hubble observations with Hubble archival images for 50 star-forming spiral and dwarf galaxies in the local universe, providing a large and extensive source for understanding the complexities of star formation and galaxy evolution. The project, called the Legacy ExtraGalactic UV Survey (LEGUS), has compiled star catalogs for each of the LEGUS galaxies and cluster catalogs for 30 of the galaxies, as well as images of the galaxies themselves. The data provides detailed information about young, massive stars and star clusters and how their environment affects their development.

"There has never been a star cluster and a stellar catalog of ultraviolet light observations," said Survey Director Daniela Calzetti of the University of Massachusetts, Amherst. "Ultraviolet light is a major tracer of the youngest and hottest star populations astronomers need to deduce the age of stars and obtain a complete star history, and the synergy of the two catalogs offers unprecedented potential for understanding star formation." [19659005] How stars form is still an annoying question in astronomy. "Much of the light we get from the universe comes from stars, and yet we still do not understand many aspects of how stars are created," said team member Elena Sabbi from the Space Telescope Science Institute, Baltimore, Maryland. "This is even the key to our existence – we know that life would not be here if we did not have a star."

The research team carefully selected the LEGUS targets from 500 galaxies assembled in ground-based elevations that are between 11 million and 58 million light-years from Earth. The team members chose galaxies based on their mass, the rate of star formation, and the abundance of elements heavier than hydrogen and helium. The catalog of ultraviolet objects collected by NASA's Galaxy Evolution Explorer (GALEX) also helped pave the way for the Hubble study.

UGCA 281 is a blue compact dwarf galaxy in the constellation of Canes Venatici. In it, two huge star clusters appear bright white and are surrounded by greenish hydrogen gas clouds. These clusters account for most of the recent star formation in UGCA 281; The rest of the galaxy consists of older stars and appears redder in color. The reddish objects in the background are background galaxies that appear through the diffuse dwarf galaxy. The image is a composite that uses both ultraviolet and visible light and was captured using Hubble's Wide Field Camera 3 and Advanced Camera for Surveys. Credit: NASA, ESA and the LEGUS team

The team used Hubble's Wide Field Camera 3 and Advanced Camera for Surveys to capture visible and ultraviolet images of galaxies and their most massive young stars and star clusters for over a year. The researchers also added archive images with visible light to provide a complete picture.

The Star Cluster catalogs contain about 8,000 young clusters whose ages range from 1 million to about 500 million years. These stellar groups are up to ten times more massive than the largest clusters in our Milky Way galaxy.

The star catalogs comprise about 39 million stars, at least five times as massive as our sun. Visible light stars are between one million and several billion years old; The youngest stars, which are between 1 million and 100 million years old, shine prominently in ultraviolet light.

The Hubble data provide all the information needed to analyze these galaxies, the researchers said. "We also offer computer models to help astronomers interpret the data in the star and cluster catalogs," said Sabbi. "For example, researchers can investigate how star formation occurs in a given galaxy or group of galaxies, correlate the properties of galaxies with their star formation, deduce the star formation history of galaxies, and help astronomers identify the precursor stars of supernovae

One of the key questions that astronomers can answer is the connection between star formation and the large structures like spiral galaxies a galaxy high.

These six images represent the diversity of star formation areas in nearby galaxies. The galaxies are part of the Legacy ExtraGalactic UV Surveys (LEGUS) of the Hubble Space Telescope, the sharpest and most comprehensive ultraviolet light image of star-forming galaxies in the nearby universe. The LEGUS study combines new Hubble observations with archival Hubble images for 50 nearby star-forming spiral and dwarf galaxies, providing a large and comprehensive source for understanding the complexities of star formation and galaxy evolution. Astronomers publish the star catalogs for each of the LEGUS galaxies and cluster catalogs for 30 of the galaxies, as well as images of the galaxies themselves. The catalogs provide detailed information about young, massive stars and star clusters, and how their environment affects their evolution. The six images consist of two dwarf galaxies (UGC 5340 and UGCA 281) and four large spiral galaxies (NGC 3368, NGC 3627, NGC 6744 and NGC 4258). The images are a mixture of ultraviolet light and visible light from Hubble's Wide Field Camera 3 and Advanced Camera for Surveys. All galaxies go through a strong star and star cluster. One of LEGUS 'goals is to study star-forming regions in each galaxy. Because the galaxies are relatively close to Earth, Hubble can resolve individual stars. The most intense and recent star birth in the dwarf galaxies concentrates away from the center. In UGC 5340, a pocket of rapid star formation appears in the lower right corner, possibly triggered by a gravitational interaction with an invisible companion galaxy. The star formation is present throughout the body of UGC 5340, and the relatively young stars are responsible for the blue-white color of the galaxy. In UGCA 281, two giant star clusters appear bright white and are surrounded by greenish clouds of hydrogen gas. These clusters account for most of the recent star formation in UGCA 281; the rest of the galaxy is older stars and appears redder in color than UGC 5340. The reddish objects in the images of the dwarf galaxies are background galaxies that appear through these diffuse objects. In the spiral galaxies, a wave of star formation takes place along the dark filaments that form the spiral arms. The young stars illuminate the surrounding hydrogen gas and make the stars appear pink. The star birth begins at the inner spiral arms and moves outward. The milky white regions in the center of these galaxies represent the glow of countless stars. The star clusters in these galaxies are between 1 million and 500 million years old. These stellar groups are up to ten times more massive than the largest clusters in our Milky Way galaxy. The stars of the galaxies seen in the images range from the size of our sun to more than one hundred times our solar mass. They are between 1 million and several billion years old. The six galaxies are between 19 million and 42 million light-years from Earth. They were observed between January 2014 and July 2014. Credit: NASA, ESA and the LEGUS team

"When we look at a spiral galaxy, we usually do not just see a random distribution of stars," said Calzetti. "It is a very ordered structure, whether it be spiral arms or rings, and this is especially true of the youngest stellar populations, but on the other hand, there are several competing theories to connect the individual stars in individual star clusters with these ordered structures." [19659005] When we see galaxies in very fine details – the star clusters – and at the same time show the connection to the larger structures, we try to identify the physical parameters that underlie this order of stellar populations within galaxies. The last link between gas and star formation is the key to understanding galaxy evolution.

Team member Linda Smith from the European Space Agency (ESA) and the Space Telescope Science Institute added, "We look at the effects of the environment, especially with star clusters, and how their survival is related to their surrounding environment. "

The LEGUS study will also help astronomers interpret views of galaxies in the distant universe where ultraviolet light is being stretched by young stars. Infrared wavelengths due to the expansion of space." The data in the star and cluster catalogs These nearby galaxies will pave the way for what we will see with the upcoming NASA observatory, the James Webb Space Telescope, the Canadian Space Agency (CSA), "said Sabbi.

Webb observations would complement LEGUS 'views : The space observatory will invade dusty star cocoons to expose the infrared glow of tiny stars not seen in images in visible and ultraviolet light. "Webb will see star formation spreading across a galaxy," Sabbi continued "If you have information about the gas properties, you can really connect the points and see where, when and how star formation happens takes place. "


Research:
Hubble covers a galaxy with star births

Further information:
legus.stsci.edu/

Provided by:
ESA / Hubble Information Center


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