The Local Group L-Band Survey: The First Measurements of Localized Cold Neutral Medium Properties in the Low-Metallicity Dwarf Galaxy NGC 6822
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arXiv
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| Auteurs principaux: | , , , , , , , , , , , , , , , , , |
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| Format: | Preprint |
| Publié: |
2024
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| _version_ | 1866913436602990592 |
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| author | Pingel, Nickolas M. Chen, Hongxing Stanimirović, Snežana Koch, Eric W. Leroy, Adam K. Rosolowsky, Erik Kim, Chang-Goo Dalcanton, Julianne J. Walter, Fabian Busch, Michael P. Chown, Ryan Meyer, Jennifer Donovan Eibensteiner, Cosima Hunter, Deidre A. Sarbadhicary, Sumit K. Tarantino, Elizabeth Villanueva, Vicente Williams, Thomas G. |
| author_facet | Pingel, Nickolas M. Chen, Hongxing Stanimirović, Snežana Koch, Eric W. Leroy, Adam K. Rosolowsky, Erik Kim, Chang-Goo Dalcanton, Julianne J. Walter, Fabian Busch, Michael P. Chown, Ryan Meyer, Jennifer Donovan Eibensteiner, Cosima Hunter, Deidre A. Sarbadhicary, Sumit K. Tarantino, Elizabeth Villanueva, Vicente Williams, Thomas G. |
| contents | Measuring the properties of the cold neutral medium (CNM) in low-metallicity galaxies provides insight into heating and cooling mechanisms in early Universe-like environments. We report detections of two localized atomic neutral hydrogen (HI) absorption features in NGC 6822, a low-metallicity (0.2 Z$_{\odot}$) dwarf galaxy in the Local Group. These are the first unambiguous CNM detections in a low-metallicity dwarf galaxy outside the Magellanic Clouds. The Local Group L-Band Survey (LGLBS) enabled these detections due to its high spatial (15 pc for HI emission) and spectral (0.4 \kms) resolution. We introduce LGLBS and describe a custom pipeline to search for HI absorption at high angular resolution and extract associated HI emission. A detailed Gaussian decomposition and radiative transfer analysis of the NGC 6822 detections reveals five CNM components, with key properties: a mean spin temperature of 32$\pm$6 K, a mean CNM column density of 3.1$\times$10$^{20}$ cm$^{-2}$, and CNM mass fractions of 0.33 and 0.12 for the two sightlines. Stacking non-detections does not reveal low-level signals below our median optical depth sensitivity of 0.05. One detection intercepts a star-forming region, with the HI absorption profile encompassing the CO (2$-$1) emission, indicating coincident molecular gas and a depression in high-resolution HI emission. We also analyze a nearby sightline with deep, narrow HI self-absorption dips, where the background warm neutral medium is attenuated by intervening CNM. The association of CNM, CO, and H$α$ emissions suggests a close link between the colder, denser HI phase and star formation in NGC 6822. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2407_13829 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | The Local Group L-Band Survey: The First Measurements of Localized Cold Neutral Medium Properties in the Low-Metallicity Dwarf Galaxy NGC 6822 Pingel, Nickolas M. Chen, Hongxing Stanimirović, Snežana Koch, Eric W. Leroy, Adam K. Rosolowsky, Erik Kim, Chang-Goo Dalcanton, Julianne J. Walter, Fabian Busch, Michael P. Chown, Ryan Meyer, Jennifer Donovan Eibensteiner, Cosima Hunter, Deidre A. Sarbadhicary, Sumit K. Tarantino, Elizabeth Villanueva, Vicente Williams, Thomas G. Astrophysics of Galaxies Measuring the properties of the cold neutral medium (CNM) in low-metallicity galaxies provides insight into heating and cooling mechanisms in early Universe-like environments. We report detections of two localized atomic neutral hydrogen (HI) absorption features in NGC 6822, a low-metallicity (0.2 Z$_{\odot}$) dwarf galaxy in the Local Group. These are the first unambiguous CNM detections in a low-metallicity dwarf galaxy outside the Magellanic Clouds. The Local Group L-Band Survey (LGLBS) enabled these detections due to its high spatial (15 pc for HI emission) and spectral (0.4 \kms) resolution. We introduce LGLBS and describe a custom pipeline to search for HI absorption at high angular resolution and extract associated HI emission. A detailed Gaussian decomposition and radiative transfer analysis of the NGC 6822 detections reveals five CNM components, with key properties: a mean spin temperature of 32$\pm$6 K, a mean CNM column density of 3.1$\times$10$^{20}$ cm$^{-2}$, and CNM mass fractions of 0.33 and 0.12 for the two sightlines. Stacking non-detections does not reveal low-level signals below our median optical depth sensitivity of 0.05. One detection intercepts a star-forming region, with the HI absorption profile encompassing the CO (2$-$1) emission, indicating coincident molecular gas and a depression in high-resolution HI emission. We also analyze a nearby sightline with deep, narrow HI self-absorption dips, where the background warm neutral medium is attenuated by intervening CNM. The association of CNM, CO, and H$α$ emissions suggests a close link between the colder, denser HI phase and star formation in NGC 6822. |
| title | The Local Group L-Band Survey: The First Measurements of Localized Cold Neutral Medium Properties in the Low-Metallicity Dwarf Galaxy NGC 6822 |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2407.13829 |