The Circumgalactic Medium of Extreme Emission Line Galaxies at z∼2: Resolved Spectroscopy and Radiative Transfer Modeling of Spatially Extended Lyα Emission in the KBSS-KCWI Survey
The resonantly scattered Ly α line illuminates the extended halos of neutral hydrogen in the circumgalactic medium of galaxies. We present integral field Keck Cosmic Web Imager observations of double-peaked, spatially extended Ly α emission in 12 relatively low-mass ( M _⋆ ∼ 10 ^9 M _⊙ ) z ∼ 2 galax...
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IOP Publishing
2023-01-01
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| Online Access: | https://doi.org/10.3847/1538-4357/acd849 |
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| author | Dawn K. Erb Zhihui Li Charles C. Steidel Yuguang Chen Max Gronke Allison L. Strom Ryan F. Trainor Gwen C. Rudie |
| author_facet | Dawn K. Erb Zhihui Li Charles C. Steidel Yuguang Chen Max Gronke Allison L. Strom Ryan F. Trainor Gwen C. Rudie |
| author_sort | Dawn K. Erb |
| collection | DOAJ |
| description | The resonantly scattered Ly α line illuminates the extended halos of neutral hydrogen in the circumgalactic medium of galaxies. We present integral field Keck Cosmic Web Imager observations of double-peaked, spatially extended Ly α emission in 12 relatively low-mass ( M _⋆ ∼ 10 ^9 M _⊙ ) z ∼ 2 galaxies characterized by extreme nebular emission lines. Using individual spaxels and small bins as well as radially binned profiles of larger regions, we find that for most objects in the sample the Ly α blue-to-red peak ratio increases, the peak separation decreases, and the fraction of flux emerging at line center increases with radius. We use new radiative transfer simulations to model each galaxy with a clumpy, multiphase outflow with radially varying outflow velocity, and self-consistently apply the same velocity model to the low-ionization interstellar absorption lines. These models reproduce the trends of peak ratio, peak separation, and trough depth with radius, and broadly reconcile outflow velocities inferred from Ly α and absorption lines. The galaxies in our sample are well-described by a model in which neutral, outflowing clumps are embedded in a hotter, more highly ionized inter-clump medium (ICM), whose residual neutral content produces absorption at the systemic redshift. The peak ratio, peak separation, and trough flux fraction are primarily governed by the line-of-sight component of the outflow velocity, the H i column density, and the residual neutral density in the ICM respectively. The azimuthal asymmetries in the line profile further suggest nonradial gas motions at large radii and variations in the H i column density in the outer halos. |
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| issn | 1538-4357 |
| language | English |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal |
| spelling | doaj-art-a2aa9a3ab79f4b7c8304246b590b30452025-08-20T02:12:41ZengIOP PublishingThe Astrophysical Journal1538-43572023-01-01953111810.3847/1538-4357/acd849The Circumgalactic Medium of Extreme Emission Line Galaxies at z∼2: Resolved Spectroscopy and Radiative Transfer Modeling of Spatially Extended Lyα Emission in the KBSS-KCWI SurveyDawn K. Erb0https://orcid.org/0000-0001-9714-2758Zhihui Li1https://orcid.org/0000-0001-5113-7558Charles C. Steidel2https://orcid.org/0000-0002-4834-7260Yuguang Chen3https://orcid.org/0000-0003-4520-5395Max Gronke4https://orcid.org/0000-0003-2491-060XAllison L. Strom5https://orcid.org/0000-0001-6369-1636Ryan F. Trainor6https://orcid.org/0000-0002-6967-7322Gwen C. Rudie7https://orcid.org/0000-0002-8459-5413The Leonard E. Parker Center for Gravitation, Cosmology and Astrophysics, Department of Physics, University of Wisconsin-Milwaukee , 3135 N Maryland Avenue, Milwaukee, WI 53211, USA ; erbd@uwm.eduCahill Center for Astronomy and Astrophysics, California Institute of Technology , 1200 E California Boulevard, MC 249-17, Pasadena, CA 91125, USACahill Center for Astronomy and Astrophysics, California Institute of Technology , 1200 E California Boulevard, MC 249-17, Pasadena, CA 91125, USACahill Center for Astronomy and Astrophysics, California Institute of Technology , 1200 E California Boulevard, MC 249-17, Pasadena, CA 91125, USA; Department of Physics and Astronomy, University of California Davis , 1 Shields Avenue, Davis, CA 95616, USAMax-Planck Institute for Astrophysics , Karl-Schwarzschild-Str. 1, D-85741 Garching, GermanyDepartment of Physics and Astronomy and Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Northwestern University , 2145 Sheridan Road, Evanston, IL 60208, USADepartment of Physics and Astronomy, Franklin & Marshall College , 637 College Avenue, Lancaster, PA 17603, USAThe Observatories of the Carnegie Institution for Science , 813 Santa Barbara Street, Pasadena, CA 91101, USAThe resonantly scattered Ly α line illuminates the extended halos of neutral hydrogen in the circumgalactic medium of galaxies. We present integral field Keck Cosmic Web Imager observations of double-peaked, spatially extended Ly α emission in 12 relatively low-mass ( M _⋆ ∼ 10 ^9 M _⊙ ) z ∼ 2 galaxies characterized by extreme nebular emission lines. Using individual spaxels and small bins as well as radially binned profiles of larger regions, we find that for most objects in the sample the Ly α blue-to-red peak ratio increases, the peak separation decreases, and the fraction of flux emerging at line center increases with radius. We use new radiative transfer simulations to model each galaxy with a clumpy, multiphase outflow with radially varying outflow velocity, and self-consistently apply the same velocity model to the low-ionization interstellar absorption lines. These models reproduce the trends of peak ratio, peak separation, and trough depth with radius, and broadly reconcile outflow velocities inferred from Ly α and absorption lines. The galaxies in our sample are well-described by a model in which neutral, outflowing clumps are embedded in a hotter, more highly ionized inter-clump medium (ICM), whose residual neutral content produces absorption at the systemic redshift. The peak ratio, peak separation, and trough flux fraction are primarily governed by the line-of-sight component of the outflow velocity, the H i column density, and the residual neutral density in the ICM respectively. The azimuthal asymmetries in the line profile further suggest nonradial gas motions at large radii and variations in the H i column density in the outer halos.https://doi.org/10.3847/1538-4357/acd849Galaxy evolutionHigh-redshift galaxiesCircumgalactic mediumGalaxy spectroscopyRadiative transfer simulations |
| spellingShingle | Dawn K. Erb Zhihui Li Charles C. Steidel Yuguang Chen Max Gronke Allison L. Strom Ryan F. Trainor Gwen C. Rudie The Circumgalactic Medium of Extreme Emission Line Galaxies at z∼2: Resolved Spectroscopy and Radiative Transfer Modeling of Spatially Extended Lyα Emission in the KBSS-KCWI Survey The Astrophysical Journal Galaxy evolution High-redshift galaxies Circumgalactic medium Galaxy spectroscopy Radiative transfer simulations |
| title | The Circumgalactic Medium of Extreme Emission Line Galaxies at z∼2: Resolved Spectroscopy and Radiative Transfer Modeling of Spatially Extended Lyα Emission in the KBSS-KCWI Survey |
| title_full | The Circumgalactic Medium of Extreme Emission Line Galaxies at z∼2: Resolved Spectroscopy and Radiative Transfer Modeling of Spatially Extended Lyα Emission in the KBSS-KCWI Survey |
| title_fullStr | The Circumgalactic Medium of Extreme Emission Line Galaxies at z∼2: Resolved Spectroscopy and Radiative Transfer Modeling of Spatially Extended Lyα Emission in the KBSS-KCWI Survey |
| title_full_unstemmed | The Circumgalactic Medium of Extreme Emission Line Galaxies at z∼2: Resolved Spectroscopy and Radiative Transfer Modeling of Spatially Extended Lyα Emission in the KBSS-KCWI Survey |
| title_short | The Circumgalactic Medium of Extreme Emission Line Galaxies at z∼2: Resolved Spectroscopy and Radiative Transfer Modeling of Spatially Extended Lyα Emission in the KBSS-KCWI Survey |
| title_sort | circumgalactic medium of extreme emission line galaxies at z∼2 resolved spectroscopy and radiative transfer modeling of spatially extended lyα emission in the kbss kcwi survey |
| topic | Galaxy evolution High-redshift galaxies Circumgalactic medium Galaxy spectroscopy Radiative transfer simulations |
| url | https://doi.org/10.3847/1538-4357/acd849 |
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