The LBT $Y_{\rm p}$ Project III: LUCI Spectra of Metal-Poor Nebulae
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| Format: | Preprint |
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2026
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| _version_ | 1866911408542711808 |
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| author | Weller, Miqaela K. Pogge, Richard W. Skillman, Evan D. Aver, Erik Rogers, Noah S. J. Berg, Danielle A. Salzer, John J. Miller Jr., John H. Spiegel, Jayde |
| author_facet | Weller, Miqaela K. Pogge, Richard W. Skillman, Evan D. Aver, Erik Rogers, Noah S. J. Berg, Danielle A. Salzer, John J. Miller Jr., John H. Spiegel, Jayde |
| contents | Accurately determining the elemental abundances of a low metallicity nebula strongly depends on measuring the density (n$_e$) and temperature (T$_e$) of the gas. Because these two parameters are inherently degenerate when derived solely from H and He recombination lines, we rely on the density-sensitive HeI $λ$10830 line to assist in resolving this issue, especially for accurate He abundances. To facilitate this, we present near-IR (NIR) LUCI spectra of 48 low-metallicity targets from the Large Binocular Telescope (LBT) and homogeneously reduce them using Pypeit as part of the LBT $Y_{\rm p}$ Project. IR spectra require special care, and we wavelength calibrate by-hand using the bright OH emission lines, carefully apply proper telluric corrections, and co-add the spectra of LUCI1 and LUCI2 on a resampled grid to ensure accurate results. We use a Gaussian profile to fit the emission lines and measure the fluxes relative to Paschen-gamma (P$γ$), resulting in HeI $λ$10830 to P$γ$ ratios consistent with previous studies. As a result, this work significantly expands the available dataset of NIR HeI $λ$10830 fluxes in low metallicity galaxies. These high-quality measurements, where we find a median flux ratio uncertainty of $\widetildeσ = 0.08$, reduce the overall uncertainties in helium abundance estimates for individual targets. The increased size of the high-quality sample enables searching for systematic uncertainties and improves the reliability of the helium abundance determinations used to infer the primordial helium abundance ($Y_{\rm p}$). |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2601_22237 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | The LBT $Y_{\rm p}$ Project III: LUCI Spectra of Metal-Poor Nebulae Weller, Miqaela K. Pogge, Richard W. Skillman, Evan D. Aver, Erik Rogers, Noah S. J. Berg, Danielle A. Salzer, John J. Miller Jr., John H. Spiegel, Jayde Astrophysics of Galaxies Cosmology and Nongalactic Astrophysics Accurately determining the elemental abundances of a low metallicity nebula strongly depends on measuring the density (n$_e$) and temperature (T$_e$) of the gas. Because these two parameters are inherently degenerate when derived solely from H and He recombination lines, we rely on the density-sensitive HeI $λ$10830 line to assist in resolving this issue, especially for accurate He abundances. To facilitate this, we present near-IR (NIR) LUCI spectra of 48 low-metallicity targets from the Large Binocular Telescope (LBT) and homogeneously reduce them using Pypeit as part of the LBT $Y_{\rm p}$ Project. IR spectra require special care, and we wavelength calibrate by-hand using the bright OH emission lines, carefully apply proper telluric corrections, and co-add the spectra of LUCI1 and LUCI2 on a resampled grid to ensure accurate results. We use a Gaussian profile to fit the emission lines and measure the fluxes relative to Paschen-gamma (P$γ$), resulting in HeI $λ$10830 to P$γ$ ratios consistent with previous studies. As a result, this work significantly expands the available dataset of NIR HeI $λ$10830 fluxes in low metallicity galaxies. These high-quality measurements, where we find a median flux ratio uncertainty of $\widetildeσ = 0.08$, reduce the overall uncertainties in helium abundance estimates for individual targets. The increased size of the high-quality sample enables searching for systematic uncertainties and improves the reliability of the helium abundance determinations used to infer the primordial helium abundance ($Y_{\rm p}$). |
| title | The LBT $Y_{\rm p}$ Project III: LUCI Spectra of Metal-Poor Nebulae |
| topic | Astrophysics of Galaxies Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2601.22237 |