• Chemical history of the Milky Way reveal

    From ScienceDaily@1:317/3 to All on Fri Feb 11 21:30:38 2022
    Chemical history of the Milky Way revealed by new catalog of tens of
    millions of stars

    Date:
    February 11, 2022
    Source:
    University of Notre Dame
    Summary:
    Researchers published a new sample catalog of more than 24 million
    stars that can be used to decipher the chemical history of elements
    in the Milky Way galaxy.



    FULL STORY ========================================================================== University of Notre Dame researchers, along with collaborators in China
    and Australia, published a new sample catalog of more than 24 million
    stars that can be used to decipher the chemical history of elements in
    the Milky Way Galaxy.


    ==========================================================================
    The research, published this month in The Astrophysical Journal,
    represents about one-hundredth of a percent of the roughly 240 billion
    stars in the Milky Way. It marks a milestone for Timothy Beers, the Grace-Rupley Professor of Physics at Notre Dame, who has spent most
    of his career planning and executing ever-larger surveys of stars to
    decipher the galaxy's formation and chemical evolution -- a field called galactic archaeology. Researchers employed a new approach to measure
    the light from each star to infer the abundances of heavy metals such
    as iron. They also measured their distances, motions and ages.

    "The elemental abundances of individual stars trace the chemical
    enrichment of the Milky Way galaxy, from when it first began to form
    stars shortly after the Big Bang to the present," Beers said.

    "Combining this information with the stellar distances and motions allows
    us to constrain the origin of different components in the galaxy, such
    as the halo and disk populations," he continued. "Adding age estimates
    puts a `clock' on the process, so that a much more complete picture of
    the entire process can be drawn." Previous spectroscopic work by Beers
    and collaborators provided the information for the tens of thousands of
    stars that were used to calibrate the new approach, based on precision photometric measurements. The recent research used large photometric
    samples obtained with the Australian SkyMapper Southern Survey and the
    European Gaia satellite mission to calibrate estimates of metallicity.

    Until recently, the only means to obtain accurate estimates of the
    content of heavy metals, such as iron, for large numbers of stars was
    by taking low- and medium-resolution spectra that could be analyzed to
    extract this information.

    The process was long and painstaking.

    Beers is most interested in the stars with the lowest metallicities --
    very metal-poor stars with iron abundances less than 1 percent that of
    the sun - - because they were born early in the history of the universe,
    and therefore reveal the origin of elements in the periodic table. In
    the early 1980s, when Beers started his work, researchers knew of only
    about 20 very metal-poor stars. This new catalog brings the total of
    what Beers refers to as "fossils of the night sky" to more than 500,000.

    Containing more than 19 million dwarf and five million giant stars, the
    new catalog is expected to advance the knowledge of how the Milky Way was formed in a variety of ways, Beers said. These include characterizing the structure of the galactic thin/thick disks -- the structural components
    of spiral galaxies - - as well as the population of stars and globular
    clusters that surround most disk galaxies, called the stellar halo. The
    catalog of stars will also help researchers identify the trails of stars
    left behind from disrupted dwarf galaxies and globular clusters.

    In addition to Beers and graduate student Derek Shank at the University of Notre Dame, other collaborators include lead author Yang Huang of Yunnan University, China; Christian Wolf and Christopher A. Onken, Australian
    National University; Young Sun Lee, Chungnam National University,
    Korea; Haibo Yuan, Beijing Normal University, China; Huawei Zhang,
    Peking University, China; Chun Wang, Tianjin Normal University, China;
    and Jianrong Shi and Zhou Fan, Chinese Academy of Sciences.

    Beers and Shank's work on this project received support from grant
    14-30152, Physics Frontier Center/JINA Center for the Evolution
    of the Elements (JINA- CEE), awarded by the U.S. National Science
    Foundation. Beers also received support from a 2019 PIFI Distinguished Scientist award from the Chinese Academy of Science.

    ========================================================================== Story Source: Materials provided by University_of_Notre_Dame. Original
    written by Deanna Csomo Ferrell. Note: Content may be edited for style
    and length.


    ========================================================================== Journal Reference:
    1. Yang Huang, Timothy C. Beers, Christian Wolf, Young Sun Lee,
    Christopher
    A. Onken, Haibo Yuan, Derek Shank, Huawei Zhang, Chun Wang,
    Jianrong Shi, Zhou Fan. Beyond Spectroscopy. I. Metallicities,
    Distances, and Age Estimates for Over 20 Million Stars from SMSS
    DR2 and Gaia EDR3. The Astrophysical Journal, 2022; 925 (2):
    164 DOI: 10.3847/1538-4357/ac21cb ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/02/220211080614.htm

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