Newly Improved Ionization Corrections for the Neutral Interstellar Medium: Enabling Accurate Abundance Determinations in Star-forming Galaxies throughout the Universe. (arXiv:2002.07831v1 [astro-ph.GA])

Newly Improved Ionization Corrections for the Neutral Interstellar Medium: Enabling Accurate Abundance Determinations in Star-forming Galaxies throughout the Universe. (arXiv:2002.07831v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Hernandez_S/0/1/0/all/0/1">Svea Hernandez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Aloisi_A/0/1/0/all/0/1">Alessandra Aloisi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+James_B/0/1/0/all/0/1">Bethan L. James</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ferland_G/0/1/0/all/0/1">Gary J. Ferland</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fox_A/0/1/0/all/0/1">Andrew J. Fox</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tosi_M/0/1/0/all/0/1">Monica Tosi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tumlinson_J/0/1/0/all/0/1">Jason Tumlinson</a>

Studies measuring the chemical abundances of the neutral gas in star-forming
galaxies (SFGs) require ionization correction factors (ICFs) to accurately
measure their metal contents. In the work presented here we calculate newly
improved ICFs for a sample of SFGs. These new corrections include both the
contaminating ionized gas along the line of sight (ICF$_{rm ionized}$) and
unaccounted higher ionization stages in the neutral gas (ICF$_{rm neutral}$).
We make use of recently acquired spectroscopic observations taken with the
Cosmic Origins Spectrograph (COS) on board Hubble to measure column densities
for Fe II and Fe III. Using the Fe III/Fe II ratios as well as other physical
properties (i.e. $log$[L$_{rm UV}$], $N$(H I), T, and $Z$) we generate ad-hoc
photoionization models with CLOUDY to quantify the corrections required for
each of the targets. We identify a luminosity threshold of $log$[L$_{rm
UV}$]$sim$ 40.75 erg s$^{-1}$ above which the ICF$_{rm neutral}$ values for
nitrogen are relatively higher (ICF$_{rm neutral}=0.05$-0.7) than those for
the rest of the elements (ICF$_{rm neutral}sim 0.01$). This behavior
indicates that for the high UV luminosity objects, N II is found in
non-negligible quantities in the neutral gas, making these ICF$_{rm neutral}$
corrections critical for determining the true abundances in the interstellar
medium. In addition, we calculate ICFs from a uniform grid of models covering a
wide range of physical properties typically observed in studies of SFGs and
extragalactic H II regions. We provide the community with tabulated ICF values
for the neutral gas abundances measured from a variety of environments and
applicable to chemical studies of the high redshift universe.

Studies measuring the chemical abundances of the neutral gas in star-forming
galaxies (SFGs) require ionization correction factors (ICFs) to accurately
measure their metal contents. In the work presented here we calculate newly
improved ICFs for a sample of SFGs. These new corrections include both the
contaminating ionized gas along the line of sight (ICF$_{rm ionized}$) and
unaccounted higher ionization stages in the neutral gas (ICF$_{rm neutral}$).
We make use of recently acquired spectroscopic observations taken with the
Cosmic Origins Spectrograph (COS) on board Hubble to measure column densities
for Fe II and Fe III. Using the Fe III/Fe II ratios as well as other physical
properties (i.e. $log$[L$_{rm UV}$], $N$(H I), T, and $Z$) we generate ad-hoc
photoionization models with CLOUDY to quantify the corrections required for
each of the targets. We identify a luminosity threshold of $log$[L$_{rm
UV}$]$sim$ 40.75 erg s$^{-1}$ above which the ICF$_{rm neutral}$ values for
nitrogen are relatively higher (ICF$_{rm neutral}=0.05$-0.7) than those for
the rest of the elements (ICF$_{rm neutral}sim 0.01$). This behavior
indicates that for the high UV luminosity objects, N II is found in
non-negligible quantities in the neutral gas, making these ICF$_{rm neutral}$
corrections critical for determining the true abundances in the interstellar
medium. In addition, we calculate ICFs from a uniform grid of models covering a
wide range of physical properties typically observed in studies of SFGs and
extragalactic H II regions. We provide the community with tabulated ICF values
for the neutral gas abundances measured from a variety of environments and
applicable to chemical studies of the high redshift universe.

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