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    Measuring Metallicities with HST/WFC3 photometry

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    Ross_metallicities2013.pdf (1.371Mb)
    Issue Date
    2013-10-17
    Author
    Ross, Teresa L.
    Holtzman, Jon
    Anthony-Twarog, Barbara
    Bond, Howard
    Twarog, Bruce A.
    Saha, Abhijit
    Walker, Alistair
    Publisher
    American Astronomical Society
    Type
    Article
    Article Version
    Scholarly/refereed, publisher version
    Published Version
    http://arxiv.org/abs/1310.4553
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    Abstract
    We quantified and calibrated the metallicity and temperature sensitivities of colors derived from nine Wide Field Camera 3 (WFC3) filters aboard the Hubble Space Telescope using Dartmouth isochrones and Kurucz atmospheres models. The theoretical isochrone colors were tested and calibrated against observations of five well studied galactic clusters: M92, NGC 6752, NGC 104, NGC 5927, and NGC 6791, all of which have spectroscopically determined metallicities spanning -2.30 < [Fe/H] < +0.4. We found empirical corrections to the Dartmouth isochrone grid for each of the following color magnitude diagrams (CMD) (F555W--F814W, F814W), (F336W-F555W, F814W), (F390M-F555W, F814W) and (F390W-F555W, F814W). Using the empirical corrections we tested the accuracy and spread of the photometric metallicities assigned from CMDs and color-color diagrams (which are necessary to break the age-metallicity degeneracy). Testing three color-color diagrams [(F336W-F555W),(F390M-F555W),(F390W-F555W), vs (F555W-F814W)], we found the colors (F390M-F555W) and (F390W-F555W), to be the best suited to measure photometric metallicities. The color (F390W-F555W) requires much less integration time, but generally produces wider metallicity distributions, and, at very-low metallicity, the MDF from (F390W-F555W) is ~60% wider than that from (F390M-F555W). Using the calibrated isochrones we recovered the overall cluster metallicity to within ~0.1 dex in [Fe/H] when using CMDs (i.e. when the distance, reddening and ages are approximately known). The measured metallicity distribution function (MDF) from color-color diagrams show this method measures metallicities of stellar clusters of unknown age and metallicity with an accuracy of ~0.2 - 0.5 dex using F336W--F555W, ~0.15 - 0.25 dex using F390M-F555W, and ~0.2 - 0.4 dex with F390W-F555W, with the larger uncertainty pertaining to the lowest metallicity range.
    Description
    This is the published version. Copyright 2013 American Astronomical Society
    URI
    http://hdl.handle.net/1808/19318
    Collections
    • Physics & Astronomy Scholarly Works [1713]
    Citation
    Ross, Teresa L., Jon A. Holtzman, Barbara J. Anthony-Twarog, Howard E. Bond, Bruce Twarog, Abhijit Saha, and Alistair Walker. "Measuring Metallicities With Hubble Space Telescope /wide-Field Camera 3 Photometry." The Astronomical Journal 147.1 (2013): 4. http://arxiv.org/abs/1310.4553

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    785-864-8983

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    Contact KU ScholarWorks
    785-864-8983
    KU Libraries
    1425 Jayhawk Blvd
    Lawrence, KS 66045
    785-864-8983

    KU Libraries
    1425 Jayhawk Blvd
    Lawrence, KS 66045
    Image Credits
     

     

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