Neutral Hydrogen (H i) 21 cm as a Probe: Investigating Spatial Variations in Interstellar Turbulent Properties
Interstellar turbulence shapes the H i distribution in the Milky Way (MW). How this affects large-scale statistical properties of H i column density across the MW remains largely unconstrained. We use the ∼13,000 deg ^2 GALFA-H i survey to map statistical fluctuations of H i over the ±40 km s ^−1 ve...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2023-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/ad0464 |
| _version_ | 1797450704925753344 |
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| author | Amit Kumar Mittal Brian L. Babler Snežana Stanimirović Nickolas Pingel |
| author_facet | Amit Kumar Mittal Brian L. Babler Snežana Stanimirović Nickolas Pingel |
| author_sort | Amit Kumar Mittal |
| collection | DOAJ |
| description | Interstellar turbulence shapes the H i distribution in the Milky Way (MW). How this affects large-scale statistical properties of H i column density across the MW remains largely unconstrained. We use the ∼13,000 deg ^2 GALFA-H i survey to map statistical fluctuations of H i over the ±40 km s ^−1 velocity range. We calculate the spatial power spectrum (SPS) of the H i column density image by running a 3° kernel and measuring the SPS slope over a range of angular scales from 16′ to 20°. Due to GALFA’s complex observing and calibration strategy, we construct detailed estimates of the noise contribution and account for GALFA beam effects on the SPS. This allows us to systematically analyze H i images that trace a wide range of interstellar environments. We find that the SPS slope varies between ∼ −2.6 at high Galactic latitudes and ∼ −3.2 close to the Galactic plane. The range of SPS slope values becomes tighter when we consider H i optical depth and line-of-sight length caused by the plane-parallel geometry of the H i disk. This relatively uniform, large-scale distribution of the SPS slope is suggestive of large-scale turbulent driving being a dominant mechanism for shaping H i structures in the MW and/or the stellar feedback turbulence being efficiently dissipated within dense molecular clouds. Only at latitudes above 60° do we find evidence for the H i SPS slope being consistently more shallow. Those directions are largely within the Local Bubble, suggesting that the recent history of this cavity, shaped by multiple supernova explosions, has modified the turbulent state of H i and/or fractions of H i phases. |
| first_indexed | 2024-03-09T14:43:23Z |
| format | Article |
| id | doaj.art-57cd09a934404c9a90627b56251747f4 |
| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-09T14:43:23Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj.art-57cd09a934404c9a90627b56251747f42023-11-27T12:03:55ZengIOP PublishingThe Astrophysical Journal1538-43572023-01-01958219210.3847/1538-4357/ad0464Neutral Hydrogen (H i) 21 cm as a Probe: Investigating Spatial Variations in Interstellar Turbulent PropertiesAmit Kumar Mittal0Brian L. Babler1https://orcid.org/0000-0002-6984-5752Snežana Stanimirović2https://orcid.org/0000-0002-3418-7817Nickolas Pingel3Department of Astronomy, University of Wisconsin−Madison , 475 N. Charter Street, Madison, WI 53706-1582 USA; Department Electrical and Computer Engineering, University of Wisconsin−Madison , 1415 Engineering Dr., Madison, WI 53706-1582 USADepartment of Astronomy, University of Wisconsin−Madison , 475 N. Charter Street, Madison, WI 53706-1582 USADepartment of Astronomy, University of Wisconsin−Madison , 475 N. Charter Street, Madison, WI 53706-1582 USADepartment of Astronomy, University of Wisconsin−Madison , 475 N. Charter Street, Madison, WI 53706-1582 USAInterstellar turbulence shapes the H i distribution in the Milky Way (MW). How this affects large-scale statistical properties of H i column density across the MW remains largely unconstrained. We use the ∼13,000 deg ^2 GALFA-H i survey to map statistical fluctuations of H i over the ±40 km s ^−1 velocity range. We calculate the spatial power spectrum (SPS) of the H i column density image by running a 3° kernel and measuring the SPS slope over a range of angular scales from 16′ to 20°. Due to GALFA’s complex observing and calibration strategy, we construct detailed estimates of the noise contribution and account for GALFA beam effects on the SPS. This allows us to systematically analyze H i images that trace a wide range of interstellar environments. We find that the SPS slope varies between ∼ −2.6 at high Galactic latitudes and ∼ −3.2 close to the Galactic plane. The range of SPS slope values becomes tighter when we consider H i optical depth and line-of-sight length caused by the plane-parallel geometry of the H i disk. This relatively uniform, large-scale distribution of the SPS slope is suggestive of large-scale turbulent driving being a dominant mechanism for shaping H i structures in the MW and/or the stellar feedback turbulence being efficiently dissipated within dense molecular clouds. Only at latitudes above 60° do we find evidence for the H i SPS slope being consistently more shallow. Those directions are largely within the Local Bubble, suggesting that the recent history of this cavity, shaped by multiple supernova explosions, has modified the turbulent state of H i and/or fractions of H i phases.https://doi.org/10.3847/1538-4357/ad0464Interstellar atomic gasInterstellar phasesInterstellar mediumthe Milky WayNeutral hydrogen clouds |
| spellingShingle | Amit Kumar Mittal Brian L. Babler Snežana Stanimirović Nickolas Pingel Neutral Hydrogen (H i) 21 cm as a Probe: Investigating Spatial Variations in Interstellar Turbulent Properties The Astrophysical Journal Interstellar atomic gas Interstellar phases Interstellar medium the Milky Way Neutral hydrogen clouds |
| title | Neutral Hydrogen (H i) 21 cm as a Probe: Investigating Spatial Variations in Interstellar Turbulent Properties |
| title_full | Neutral Hydrogen (H i) 21 cm as a Probe: Investigating Spatial Variations in Interstellar Turbulent Properties |
| title_fullStr | Neutral Hydrogen (H i) 21 cm as a Probe: Investigating Spatial Variations in Interstellar Turbulent Properties |
| title_full_unstemmed | Neutral Hydrogen (H i) 21 cm as a Probe: Investigating Spatial Variations in Interstellar Turbulent Properties |
| title_short | Neutral Hydrogen (H i) 21 cm as a Probe: Investigating Spatial Variations in Interstellar Turbulent Properties |
| title_sort | neutral hydrogen h i 21 cm as a probe investigating spatial variations in interstellar turbulent properties |
| topic | Interstellar atomic gas Interstellar phases Interstellar medium the Milky Way Neutral hydrogen clouds |
| url | https://doi.org/10.3847/1538-4357/ad0464 |
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