The present-day mass-metallicity relation for galaxies using a new electron-temperature method. (arXiv:1901.02890v1 [astro-ph.GA])

The present-day mass-metallicity relation for galaxies using a new electron-temperature method. (arXiv:1901.02890v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Yates_R/0/1/0/all/0/1">Robert M. Yates</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schady_P/0/1/0/all/0/1">Patricia Schady</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chen_T/0/1/0/all/0/1">Ting-Wan Chen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schweyer_T/0/1/0/all/0/1">Tassilo Schweyer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wiseman_P/0/1/0/all/0/1">Philip Wiseman</a>

We present a study of electron temperatures (Te) and gas-phase oxygen
abundances (Z_Te) for galaxies in the local Universe (z<0.25). Our sample comprises spectra from a total of 264 emission-line systems, ranging from individual HII regions to whole galaxies, and including 23 composite HII regions in predominantly 'main-sequence' galaxies from the MaNGA survey. We utilise 130 of these systems with directly measurable T(OII) to derive a new metallicity-dependent T(OIII)-T(OII) relation that provides a better representation of our varied data set than existing relations from the literature. Importantly, we find that all the T(OIII)-T(OII) relations considered here intrinsically under-estimate Z_Te at low O++/O+ by up to 0.6 dex, and provide an empirical correction based on strong-emission lines to account for this bias when using our relation. Our new Te method therefore allows accurate metallicities (1sigma = 0.08 dex) to be derived for any low-redshift system with an [OIII]4363 line detection, regardless of its physical size or ionisation state. This new Te method is then used to form the mass - metallicity relation (MZR) for a set of 118 local star-forming galaxies that is not strongly biased to starbursts. Our new MZR is in very good agreement with those formed from direct measurements of metal recombination lines and blue supergiant absorption lines, in contrast to most other Te-based and strong-line-based MZRs. Our new Te method therefore provides an accurate and precise way of obtaining metallicities for a large and diverse range of star-forming systems in the local Universe.

We present a study of electron temperatures (Te) and gas-phase oxygen
abundances (Z_Te) for galaxies in the local Universe (z<0.25). Our sample
comprises spectra from a total of 264 emission-line systems, ranging from
individual HII regions to whole galaxies, and including 23 composite HII
regions in predominantly ‘main-sequence’ galaxies from the MaNGA survey. We
utilise 130 of these systems with directly measurable T(OII) to derive a new
metallicity-dependent T(OIII)-T(OII) relation that provides a better
representation of our varied data set than existing relations from the
literature. Importantly, we find that all the T(OIII)-T(OII) relations
considered here intrinsically under-estimate Z_Te at low O++/O+ by up to 0.6
dex, and provide an empirical correction based on strong-emission lines to
account for this bias when using our relation. Our new Te method therefore
allows accurate metallicities (1sigma = 0.08 dex) to be derived for any
low-redshift system with an [OIII]4363 line detection, regardless of its
physical size or ionisation state. This new Te method is then used to form the
mass – metallicity relation (MZR) for a set of 118 local star-forming galaxies
that is not strongly biased to starbursts. Our new MZR is in very good
agreement with those formed from direct measurements of metal recombination
lines and blue supergiant absorption lines, in contrast to most other Te-based
and strong-line-based MZRs. Our new Te method therefore provides an accurate
and precise way of obtaining metallicities for a large and diverse range of
star-forming systems in the local Universe.

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