Caught in the Act: A Metal-rich High-velocity Cloud in the Inner Galaxy
We characterize the chemical and physical conditions in an outflowing high-velocity cloud (HVC) in the inner Galaxy. We report a supersolar metallicity of [O/H] = +0.36 ± 0.12 for the HVC at v _LSR = 125.6 km s ^−1 toward the star HD 156359 ( l = 328.°7, b = −14.°5, d = 9 kpc, z = −2.3 kpc). Using a...
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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/acaaa5 |
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| author | Frances H. Cashman Andrew J. Fox Bart P. Wakker Trisha Ashley Derck Massa Edward B. Jenkins Dhanesh Krishnarao Robert A. Benjamin Rongmon Bordoloi Tae-Sun Kim |
| author_facet | Frances H. Cashman Andrew J. Fox Bart P. Wakker Trisha Ashley Derck Massa Edward B. Jenkins Dhanesh Krishnarao Robert A. Benjamin Rongmon Bordoloi Tae-Sun Kim |
| author_sort | Frances H. Cashman |
| collection | DOAJ |
| description | We characterize the chemical and physical conditions in an outflowing high-velocity cloud (HVC) in the inner Galaxy. We report a supersolar metallicity of [O/H] = +0.36 ± 0.12 for the HVC at v _LSR = 125.6 km s ^−1 toward the star HD 156359 ( l = 328.°7, b = −14.°5, d = 9 kpc, z = −2.3 kpc). Using archival observations from the Far-Ultraviolet Spectroscopic Explorer (FUSE), the Hubble Space Telescope Imaging Spectrograph, and the European Southern Observatory Fiber-fed Extended Range Optical Spectrograph we measure high-velocity absorption in H i , O i , C ii , N ii , Si ii , Ca ii , Si iii , Fe iii , C iv , Si iv , N v , and O vi . We measure a low H i column density of log N (H i ) = 15.54 ± 0.05 in the HVC from multiple unsaturated H i Lyman series lines in the FUSE data. We determine a low dust depletion level in the HVC from the relative strength of silicon, iron, and calcium absorption relative to oxygen, with [Si/O] = −0.33 ± 0.14, [Fe/O] = −0.30 ± 0.20, and [Ca/O] = −0.56 ± 0.16. Analysis of the high-ion absorption using collisional ionization models indicates that the hot plasma is multiphase, with the C iv and Si iv tracing 10 ^4.9 K gas and N v and O vi tracing 10 ^5.4 K gas. The cloud’s metallicity, dust content, kinematics, and close proximity to the disk are all consistent with a Galactic wind origin. As the HD 156359 line of sight probes the inner Galaxy, the HVC appears to be a young cloud caught in the act of being entrained in a multiphase Galactic outflow and driven out into the halo. |
| first_indexed | 2024-03-11T10:25:00Z |
| format | Article |
| id | doaj.art-cb95e26dcab845bb9165237d72e77c35 |
| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-11T10:25:00Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal |
| spelling | doaj.art-cb95e26dcab845bb9165237d72e77c352023-11-15T16:39:09ZengIOP PublishingThe Astrophysical Journal1538-43572023-01-0194416510.3847/1538-4357/acaaa5Caught in the Act: A Metal-rich High-velocity Cloud in the Inner GalaxyFrances H. Cashman0https://orcid.org/0000-0003-4237-3553Andrew J. Fox1https://orcid.org/0000-0003-0724-4115Bart P. Wakker2https://orcid.org/0000-0002-0507-7096Trisha Ashley3https://orcid.org/0000-0002-6541-869XDerck Massa4https://orcid.org/0000-0002-9139-2964Edward B. Jenkins5https://orcid.org/0000-0003-1892-4423Dhanesh Krishnarao6https://orcid.org/0000-0002-7955-7359Robert A. Benjamin7https://orcid.org/0000-0002-8109-2642Rongmon Bordoloi8https://orcid.org/0000-0002-3120-7173Tae-Sun Kim9Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA ; frcashman@stsci.eduAURA for ESA, Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA ; afox@stsci.edu; Department of Physics & Astronomy, Johns Hopkins University , 3400 N. Charles Street, Baltimore, MD 21218, USADepartment of Astronomy, University of Wisconsin-Madison , 475 North Charter Street, Madison, WI 53706, USASpace Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA ; frcashman@stsci.eduSpace Science Institute , 4750 Walnut Street Suite 205 Boulder, CO 80301, USADepartment of Astrophysical Sciences, Princeton University , Princeton, NJ 08544-1001, USASpace Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA ; frcashman@stsci.edu; NSF Astronomy & Astrophysics Postdoctoral Fellow, Johns Hopkins University , 3400 N. Charles Street, Baltimore, MD 21218, USA; Department of Physics, Colorado College , 14 East Cache La Poudre Street, Colorado Springs, CO 80903, USADepartment of Physics, University of Wisconsin-Whitewater , 800 West Main Street, Whitewater, WI 53190, USADepartment of Physics, North Carolina State University , 421 Riddick Hall, Raleigh, NC 27695-8202, USADepartment of Astronomy, University of Wisconsin-Madison , 475 North Charter Street, Madison, WI 53706, USAWe characterize the chemical and physical conditions in an outflowing high-velocity cloud (HVC) in the inner Galaxy. We report a supersolar metallicity of [O/H] = +0.36 ± 0.12 for the HVC at v _LSR = 125.6 km s ^−1 toward the star HD 156359 ( l = 328.°7, b = −14.°5, d = 9 kpc, z = −2.3 kpc). Using archival observations from the Far-Ultraviolet Spectroscopic Explorer (FUSE), the Hubble Space Telescope Imaging Spectrograph, and the European Southern Observatory Fiber-fed Extended Range Optical Spectrograph we measure high-velocity absorption in H i , O i , C ii , N ii , Si ii , Ca ii , Si iii , Fe iii , C iv , Si iv , N v , and O vi . We measure a low H i column density of log N (H i ) = 15.54 ± 0.05 in the HVC from multiple unsaturated H i Lyman series lines in the FUSE data. We determine a low dust depletion level in the HVC from the relative strength of silicon, iron, and calcium absorption relative to oxygen, with [Si/O] = −0.33 ± 0.14, [Fe/O] = −0.30 ± 0.20, and [Ca/O] = −0.56 ± 0.16. Analysis of the high-ion absorption using collisional ionization models indicates that the hot plasma is multiphase, with the C iv and Si iv tracing 10 ^4.9 K gas and N v and O vi tracing 10 ^5.4 K gas. The cloud’s metallicity, dust content, kinematics, and close proximity to the disk are all consistent with a Galactic wind origin. As the HD 156359 line of sight probes the inner Galaxy, the HVC appears to be a young cloud caught in the act of being entrained in a multiphase Galactic outflow and driven out into the halo.https://doi.org/10.3847/1538-4357/acaaa5Galactic centerUltraviolet astronomyHigh-velocity cloudsChemical abundancesGalactic winds |
| spellingShingle | Frances H. Cashman Andrew J. Fox Bart P. Wakker Trisha Ashley Derck Massa Edward B. Jenkins Dhanesh Krishnarao Robert A. Benjamin Rongmon Bordoloi Tae-Sun Kim Caught in the Act: A Metal-rich High-velocity Cloud in the Inner Galaxy The Astrophysical Journal Galactic center Ultraviolet astronomy High-velocity clouds Chemical abundances Galactic winds |
| title | Caught in the Act: A Metal-rich High-velocity Cloud in the Inner Galaxy |
| title_full | Caught in the Act: A Metal-rich High-velocity Cloud in the Inner Galaxy |
| title_fullStr | Caught in the Act: A Metal-rich High-velocity Cloud in the Inner Galaxy |
| title_full_unstemmed | Caught in the Act: A Metal-rich High-velocity Cloud in the Inner Galaxy |
| title_short | Caught in the Act: A Metal-rich High-velocity Cloud in the Inner Galaxy |
| title_sort | caught in the act a metal rich high velocity cloud in the inner galaxy |
| topic | Galactic center Ultraviolet astronomy High-velocity clouds Chemical abundances Galactic winds |
| url | https://doi.org/10.3847/1538-4357/acaaa5 |
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