2016ApJ...816...40J -
Astrophys. J., 816, 40 (2016/January-1)
Resolving ionization and metallicity on parsec scales across Mrk 71 with HST-WFC3.
JAMES B.L., AUGER M., ALOISI A., CALZETTI D. and KEWLEY L.
Abstract (from CDS):
Blue compact dwarf (BCD) galaxies in the nearby universe provide a means for studying feedback mechanisms and star formation processes in low-metallicity environments in great detail. Owing to their vicinity, these local analogs to primordial young galaxies are well suited for high-resolution studies that are unfeasible for high-redshift galaxies. Here we present Hubble Space Telescope Wide Field Camera 3 observations of one such BCD, Mrk 71, one of the most powerful local starbursts known, in the light of [O ii], He ii, Hβ, [O iii], Hα, and [S ii]. At D ~= 3.44 Mpc, this extensive suite of emission-line images enables us to explore the chemical and physical conditions of Mrk 71 on ∼2 pc scales. We use emission-line diagnostics to distinguish ionization mechanisms on a pixel-by-pixel basis and show that despite the previously reported hypersonic gas and superbubble blowout, the gas in Mrk 71 is photoionized, with no sign of shock-excited emission. He ii emission line images are used to identify up to six Wolf-Rayet stars, three of which lie on the edge of a blowout region. Using strong-line metallicity diagnostics, we present the first ''metallicity image'' of a galaxy, revealing chemical inhomogeneity on scales of <50 pc. We additionally demonstrate that while chemical structure can be lost at large scales, metallicity diagnostics can break down on spatial scales smaller than an H ii region. This study highlights not only the benefits of high-resolution spatially resolved observations in assessing the effects of feedback mechanisms but also the potential limitations when employing emission-line diagnostics; these results are particularly relevant as we enter the era of extremely large telescopes.
Abstract Copyright:
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Journal keyword(s):
galaxies: abundances - galaxies: individual: Mrk 71 - galaxies: star formation - stars: winds, outflows - stars: Wolf-Rayet - techniques: imaging spectroscopy
CDS comments:
Table 3: Sources A1, B1, B2, B3-5 and B6 are not in SIMBAD.
Simbad objects:
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