RESEARCH
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Detecting metal-poor gas accretion in the star-forming dwarf galaxies UM 461 and Mrk 600

P. Lagos, T. C. Scott, A. Nigoche-Netro, R. Demarco, A. Humphrey, P. Papaderos

Abstract
Using VIMOS-IFU observations, we study the interstellar medium (ISM) of two star-forming dwarf galaxies, UM 461 and Mrk 600. Our aim was to search for the existence of metallicity inhomogeneities that might arise from infall of nearly pristine gas feeding ongoing localized star-formation. The IFU data allowed us to study the impact of external gas accretion on the chemical evolution as well as the ionised gas kinematics and morphologies of these galaxies. Both systems show signs of morphological distortions, including cometary-like morphologies. We analysed the spatial variation of 12+log(O/H) abundances within both galaxies using the direct method (T), the widely applied HII-CHI-mistry code, as well as by employing different standard calibrations. For UM461 our results show that the ISM is fairly well mixed, at large scales, however we find an off-centre and low-metallicity region with 12+log(O/H)<7.6 in the SW part of the brightest HII region, using the direct method. This result is consistent with the recent infall of a low mass metal-poor dwarf or HI cloud into the region now exhibiting the lowest metallicity, which also displays localized perturbed neutral and ionized gas kinematics. Mrk 600 in contrast, appears to be chemically homogeneous on both large and small scales. The intrinsic differences in the spatially resolved properties of the ISM in our analysed galaxies are consistent with these systems being at different evolutionary stages.

Keywords
Astrophysics - Astrophysics of Galaxies

Monthly Notices of the Royal Astronomical Society
2018 March

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Instituto de Astrofísica e Ciências do Espaço Universidade do Porto Faculdade de Ciências da Universidade de Lisboa
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia