Tests of star formation metrics in the low-metallicity galaxy NGC5253 using ALMA observations of H30α line emission

George Bendo, R E Miura, D Espada, K Nakanishi, Robert Beswick, Michael D'Cruze, Clive Dickinson, Gary Fuller

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    Abstract

    We use Atacama Large Millimeter/submillimeter Array (ALMA) observations of H30 (231.90 GHz) emission from the low metallicity dwarf galaxy NGC 5253 to measure the star formation rate (SFR) within the galaxy and to test the reliability of SFRs derived from other commonly-used metrics. The H30 emission, which originates mainly from the central starburst, yields a photoionizing photon production rate of (1.9±0.3)×1052 s−1 and an SFR of 0.087±0.013 M⊙ yr−1 based on conversions that account for the low metallicity of the galaxy and for stellar rotation. Among the other star formation metrics we examined, the SFR calculated from the total infrared flux was statistically equivalent to the values from the H30 data. The SFR based on previously-published versions of the H
    flux that were extinction corrected using Pa and Pa lines were lower than but also statistically similar to the H30 value. The mid-infrared (22 μm) flux density and the composite star formation tracer based on H and mid-infrared emission give SFRs that were significantly higher because the dust emission appears unusually hot compared to typical spiral galaxies. Conversely, the 70 and 160 μm flux densities yielded SFR lower than the H30 value, although the SFRs from the 70 μm and H30
    data were within 1-2 of each other. While further analysis on a broader range of galaxies are needed, these results are instructive of the best and worst methods to use when measuring SFR in low metallicity dwarf galaxies like NGC 5253.
    Original languageEnglish
    Pages (from-to)1239-1252
    Number of pages13
    JournalMonthly Notices of the Royal Astronomical Society
    Volume472
    Issue number1
    Early online date20 Jul 2017
    DOIs
    Publication statusPublished - 21 Nov 2017

    Keywords

    • galaxies: dwarf
    • galaxies: individual: NGC 5253
    • galaxies: starburst
    • galaxies: star formation
    • radio lines: galaxies

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