CLASSY. VI. The Density, Structure, and Size of Absorption-line Outflows in Starburst Galaxies
Galaxy formation and evolution are regulated by the feedback from galactic winds. Absorption lines provide the most widely available probe of winds. However, since most data only provide information integrated along the line of sight, they do not directly constrain the radial structure of the outflo...
| 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/acbf46 |
| _version_ | 1797701757645619200 |
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| author | Xinfeng Xu Timothy Heckman Alaina Henry Danielle A. Berg John Chisholm Bethan L. James Crystal L. Martin Daniel P. Stark Matthew Hayes Karla Z. Arellano-Córdova Cody Carr Mason Huberty Matilde Mingozzi Claudia Scarlata Yuma Sugahara |
| author_facet | Xinfeng Xu Timothy Heckman Alaina Henry Danielle A. Berg John Chisholm Bethan L. James Crystal L. Martin Daniel P. Stark Matthew Hayes Karla Z. Arellano-Córdova Cody Carr Mason Huberty Matilde Mingozzi Claudia Scarlata Yuma Sugahara |
| author_sort | Xinfeng Xu |
| collection | DOAJ |
| description | Galaxy formation and evolution are regulated by the feedback from galactic winds. Absorption lines provide the most widely available probe of winds. However, since most data only provide information integrated along the line of sight, they do not directly constrain the radial structure of the outflows. In this paper, we present a method to directly measure the gas electron density in outflows ( n _e ), which in turn yields estimates of outflow cloud properties (e.g., density, volume filling factor, and sizes/masses). We also estimate the distance ( r _n ) from the starburst at which the observed densities are found. We focus on 22 local star-forming galaxies primarily from the COS Legacy Archive Spectroscopic SurveY (CLASSY). In half of them, we detect absorption lines from fine-structure excited transitions of Si ii (i.e., Si ii *). We determine n _e from relative column densities of Si ii and Si ii *, given Si ii * originates from collisional excitation by free electrons. We find that the derived n _e correlates well with the galaxy’s star formation rate per unit area. From photoionization models or assuming the outflow is in pressure equilibrium with the wind fluid, we get r _n ∼ 1–2 r _* or ∼5 r _* , respectively, where r _* is the starburst radius. Based on comparisons to theoretical models of multiphase outflows, nearly all of the outflows have cloud sizes large enough for the clouds to survive their interaction with the hot wind fluid. Most of these measurements are the first ever for galactic winds detected in absorption lines and, thus, will provide important constraints for future models of galactic winds. |
| first_indexed | 2024-03-12T04:40:20Z |
| format | Article |
| id | doaj.art-b6bde2dde095407c8fa8f08a772d15f3 |
| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-12T04:40:20Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj.art-b6bde2dde095407c8fa8f08a772d15f32023-09-03T09:43:29ZengIOP PublishingThe Astrophysical Journal1538-43572023-01-0194812810.3847/1538-4357/acbf46CLASSY. VI. The Density, Structure, and Size of Absorption-line Outflows in Starburst GalaxiesXinfeng Xu0https://orcid.org/0000-0002-9217-7051Timothy Heckman1https://orcid.org/0000-0001-6670-6370Alaina Henry2https://orcid.org/0000-0002-6586-4446Danielle A. Berg3https://orcid.org/0000-0002-4153-053XJohn Chisholm4https://orcid.org/0000-0002-0302-2577Bethan L. James5https://orcid.org/0000-0003-4372-2006Crystal L. Martin6https://orcid.org/0000-0001-9189-7818Daniel P. Stark7https://orcid.org/0000-0001-6106-5172Matthew Hayes8https://orcid.org/0000-0001-8587-218XKarla Z. Arellano-Córdova9https://orcid.org/0000-0002-2644-3518Cody Carr10https://orcid.org/0000-0003-4166-2855Mason Huberty11Matilde Mingozzi12https://orcid.org/0000-0003-2589-762XClaudia Scarlata13https://orcid.org/0000-0002-9136-8876Yuma Sugahara14https://orcid.org/0000-0001-6958-7856Center for Astrophysical Sciences, Department of Physics & Astronomy, Johns Hopkins University , Baltimore, MD 21218, USA ; xinfeng@jhu.eduCenter for Astrophysical Sciences, Department of Physics & Astronomy, Johns Hopkins University , Baltimore, MD 21218, USA ; xinfeng@jhu.eduCenter for Astrophysical Sciences, Department of Physics & Astronomy, Johns Hopkins University , Baltimore, MD 21218, USA ; xinfeng@jhu.edu; Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USADepartment of Astronomy, The University of Texas at Austin , 2515 Speedway, Stop C1400, Austin, TX 78712, USADepartment of Astronomy, The University of Texas at Austin , 2515 Speedway, Stop C1400, Austin, TX 78712, USAAURA for ESA, Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USADepartment of Physics, University of California , Santa Barbara, Santa Barbara, CA 93106, USASteward Observatory, The University of Arizona , 933 N Cherry Avenue, Tucson, AZ, 85721, USAStockholm University , Department of Astronomy and Oskar Klein Centre for Cosmoparticle Physics, AlbaNova University Centre, SE-10691, Stockholm, SwedenDepartment of Astronomy, The University of Texas at Austin , 2515 Speedway, Stop C1400, Austin, TX 78712, USAMinnesota Institute for Astrophysics, University of Minnesota , 116 Church Street SE, Minneapolis, MN 55455, USAMinnesota Institute for Astrophysics, University of Minnesota , 116 Church Street SE, Minneapolis, MN 55455, USASpace Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USAMinnesota Institute for Astrophysics, University of Minnesota , 116 Church Street SE, Minneapolis, MN 55455, USANational Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; Waseda Research Institute for Science and Engineering, Faculty of Science and Engineering, Waseda University , 3-4-1, Okubo, Shinjuku, Tokyo 169-8555, JapanGalaxy formation and evolution are regulated by the feedback from galactic winds. Absorption lines provide the most widely available probe of winds. However, since most data only provide information integrated along the line of sight, they do not directly constrain the radial structure of the outflows. In this paper, we present a method to directly measure the gas electron density in outflows ( n _e ), which in turn yields estimates of outflow cloud properties (e.g., density, volume filling factor, and sizes/masses). We also estimate the distance ( r _n ) from the starburst at which the observed densities are found. We focus on 22 local star-forming galaxies primarily from the COS Legacy Archive Spectroscopic SurveY (CLASSY). In half of them, we detect absorption lines from fine-structure excited transitions of Si ii (i.e., Si ii *). We determine n _e from relative column densities of Si ii and Si ii *, given Si ii * originates from collisional excitation by free electrons. We find that the derived n _e correlates well with the galaxy’s star formation rate per unit area. From photoionization models or assuming the outflow is in pressure equilibrium with the wind fluid, we get r _n ∼ 1–2 r _* or ∼5 r _* , respectively, where r _* is the starburst radius. Based on comparisons to theoretical models of multiphase outflows, nearly all of the outflows have cloud sizes large enough for the clouds to survive their interaction with the hot wind fluid. Most of these measurements are the first ever for galactic winds detected in absorption lines and, thus, will provide important constraints for future models of galactic winds.https://doi.org/10.3847/1538-4357/acbf46Galaxy evolutionGalaxy windsGalaxy kinematicsStarburst galaxiesUltraviolet astronomyGalaxy spectroscopy |
| spellingShingle | Xinfeng Xu Timothy Heckman Alaina Henry Danielle A. Berg John Chisholm Bethan L. James Crystal L. Martin Daniel P. Stark Matthew Hayes Karla Z. Arellano-Córdova Cody Carr Mason Huberty Matilde Mingozzi Claudia Scarlata Yuma Sugahara CLASSY. VI. The Density, Structure, and Size of Absorption-line Outflows in Starburst Galaxies The Astrophysical Journal Galaxy evolution Galaxy winds Galaxy kinematics Starburst galaxies Ultraviolet astronomy Galaxy spectroscopy |
| title | CLASSY. VI. The Density, Structure, and Size of Absorption-line Outflows in Starburst Galaxies |
| title_full | CLASSY. VI. The Density, Structure, and Size of Absorption-line Outflows in Starburst Galaxies |
| title_fullStr | CLASSY. VI. The Density, Structure, and Size of Absorption-line Outflows in Starburst Galaxies |
| title_full_unstemmed | CLASSY. VI. The Density, Structure, and Size of Absorption-line Outflows in Starburst Galaxies |
| title_short | CLASSY. VI. The Density, Structure, and Size of Absorption-line Outflows in Starburst Galaxies |
| title_sort | classy vi the density structure and size of absorption line outflows in starburst galaxies |
| topic | Galaxy evolution Galaxy winds Galaxy kinematics Starburst galaxies Ultraviolet astronomy Galaxy spectroscopy |
| url | https://doi.org/10.3847/1538-4357/acbf46 |
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