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ALMA Observations of [OI]145um and [NII]205um Emission lines from Star-Forming Galaxies at $z\sim7$

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arxiv 2504.03831 v1 pith:7HV7237W submitted 2025-04-04 astro-ph.GA

classification astro-ph.GA
keywords emissiongalaxieslinesneutralobservationssigmastar-formingalma
verification ladder T0 review T1 audit T2 compute T3 formal
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abstract

We present results of new observations of [OI]145um and [NII]205um emission lines from four star-forming galaxies at redshifts between $z=6.58$ and $7.68$ that have previous detections of \Ciium\ and dust continua. Using ALMA, we successfully detect [OI]145um emission from all targets at $>4\,\sigma$ significance. However, [NII]205um emission is undetected in all galaxies (SNR $<3.5\,\sigma$) except for a tentative detection from A1689-zD1. From the observed high [CII]/[NII] emission line ratios ($\gtrsim20 - 80$), we find that most of the [CII]158um emission arise from neutral gas regions ($3\,\sigma$ lower limits of $\gtrsim 74 - 96\%$). From [OI]145um, [CII]158um lines, and infrared luminosities, we estimate the neutral gas densities of $n_{\rm H}=10^{3.5}$ - $10^6\,{\rm cm^{-3}}$ and the far-ultraviolet (FUV) radiation strengths of $G_0\sim10^{2.5}$-$10^{3}$. While the neutral gas densities are similar to those of high-redshift starburst galaxies, the FUV strengths are lower compared to both local and high-redshift starbursts. Finally, we estimate atomic hydrogen masses using [OI]145um emission lines and the oxygen abundances measured from recent JWST observations. We find gas mass ratios of $f_{\rm gas}\sim0.3$ - $0.8$, which are similar to earlier studies using [CII]158um. Starting from this pilot observation, future large [OI]145um emission line surveys will provide us with currently little-known neutral gas properties of star-forming galaxies in the early Universe.

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Cited by 3 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. Fine-structure Line Atlas for Multi-wavelength Extragalactic Study (FLAMES) III: [C II] as Tracer, Crisis of SFR, [O III]/[C II] at High-z, New Answers and New Questions

    astro-ph.GA 2025-07 conditional novelty 6.0 of 10

    A universal gas-line deficit relative to infrared luminosity, seen in [C II], [O I], [N II], and extinction-corrected H-alpha, breaks standard SFR calibrations in the brightest dusty galaxies and implies a metallicity...

  2. Fine-structure Line Atlas for Multi-wavelength Extragalactic Study (FLAMES) I: Comprehensive Low and High Redshift Catalogs and Empirical Relations for Probing Gas Conditions

    astro-ph.GA 2025-07 conditional novelty 6.0 of 10

    A new 1800-galaxy atlas of infrared fine-structure lines shows line ratios chiefly trace abundances and radiation hardness, quantifies AGN contamination in [O III]88 and [O I]63, and finds most density tracers biased.

  3. Gas-Poor Hosts and Gas-Rich Companions of $z\approx$3.5 Radio Active Galactic Nuclei: ALMA Insights into Jet Triggering and Feedback

    astro-ph.GA 2025-06 conditional novelty 6.0 of 10

    Around z~3.5 radio-loud AGN, nearly all detectable cold gas sits in off-center companion clouds rather than in the AGN host galaxies, supporting merger-driven triggering or feedback scenarios.

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