DUVET: Resolved direct metallicity measurements in the outflow of starburst galaxy NGC 1569
Monthly Notices of the Royal Astronomical Society(2024)
摘要
We present the results of direct-method metallicity measurements in the disk
and outflow of the low-metallicity starburst galaxy NGC 1569. We use Keck
Cosmic Web Imager observations to map the galaxy across 54 (800 pc)
along the major axis and 48 (700 pc) along the minor axis with a
spatial resolution of 1 (∼15 pc). We detect common strong
emission lines ([OIII] λ5007, Hβ, [OII]
λ3727) and the fainter [OIII] λ4363 auroral line, which
allows us to measure electron temperature (T_e) and metallicity. Theory
suggests that outflows drive metals out of the disk driving observed trends
between stellar mass and gas-phase metallicity. Our main result is that the
metallicity in the outflow is similar to that of the disk, Z_ out /
Z_ ISM≈ 1. This is consistent with previous absorption line
studies in higher mass galaxies. Assumption of a mass-loading factor of
Ṁ_ out/ SFR∼3 makes the metal-loading of NGC 1569
consistent with expectations derived from the mass-metallicity relationship.
Our high spatial resolution metallicity maps reveal a region around a
supermassive star cluster (SSC-B) with distinctly higher metallicity and higher
electron density, compared to the disk. Given the known properties of SSC-B the
higher metallicity and density of this region are likely the result of star
formation-driven feedback acting on the local scale. Overall, our results are
consistent with the picture in which metal-enriched winds pollute the
circumgalactic medium surrounding galaxies, and thus connect the small-scale
feedback processes to large-scale properties of galaxy halos.
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