Microphysics of Circumgalactic Turbulence Probed by Fast Radio Bursts and Quasars
The circumgalactic medium (CGM) is poorly constrained at the subparsec scales relevant to turbulent energy dissipation and regulation of multiphase structure. Fast radio bursts are sensitive to small-scale plasma density fluctuations, which can induce multipath propagation (scattering). The amount o...
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2025-01-01
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| Online Access: | https://doi.org/10.3847/1538-4357/ade0bc |
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| author | Stella Koch Ocker Mandy C. Chen S. Peng Oh Prateek Sharma |
| author_facet | Stella Koch Ocker Mandy C. Chen S. Peng Oh Prateek Sharma |
| author_sort | Stella Koch Ocker |
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| description | The circumgalactic medium (CGM) is poorly constrained at the subparsec scales relevant to turbulent energy dissipation and regulation of multiphase structure. Fast radio bursts are sensitive to small-scale plasma density fluctuations, which can induce multipath propagation (scattering). The amount of scattering depends on the density fluctuation spectrum, including its amplitude ${C}_{{\rm{n}}}^{2}$ , spectral index β , and dissipation scale l _i . We use quasar observations of CGM turbulence at ≳pc scales to infer ${C}_{{\rm{n}}}^{2}$ , finding it to be $1{0}^{-16}\lesssim {C}_{{\rm{n}}}^{2}\lesssim 1{0}^{-9}$ m ^−20/3 for hot ( T > 10 ^6 K) gas and $1{0}^{-8}\lesssim {C}_{{\rm{n}}}^{2}\lesssim 1{0}^{-4}$ m ^−20/3 for cool (10 ^4 ≲ T ≲ 10 ^5 K) gas, depending on the gas sound speed and density. These values of ${C}_{{\rm{n}}}^{2}$ are much smaller than those inferred in the interstellar medium at similar physical scales. The resulting scattering delays from the hot CGM are negligible (≪1 μ s at 1 GHz), but they are more detectable from the cool gas as either radio pulse broadening or scintillation, depending on the observing frequency and sightline geometry. Joint quasar-FRB observations of individual galaxies can yield lower limits on l _i , even if the CGM is not a significant scattering site. An initial comparison between quasar and FRB observations (albeit for different systems) suggests l _i ≳ 750 km in ∼10 ^4 K gas in order for the quasar and FRB constraints to be consistent. If a foreground CGM is completely ruled out as a source of scattering along an FRB sightline, then l _i may be comparable to the smallest cloud sizes (≲pc) inferred from photoionization modeling of quasar absorption lines. |
| format | Article |
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| institution | DOAJ |
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| language | English |
| publishDate | 2025-01-01 |
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| series | The Astrophysical Journal |
| spelling | doaj-art-e390555558f34d9685721488673b5db82025-08-20T03:11:52ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-0198816910.3847/1538-4357/ade0bcMicrophysics of Circumgalactic Turbulence Probed by Fast Radio Bursts and QuasarsStella Koch Ocker0https://orcid.org/0000-0002-4941-5333Mandy C. Chen1https://orcid.org/0000-0002-8739-3163S. Peng Oh2https://orcid.org/0000-0002-1013-4657Prateek Sharma3https://orcid.org/0000-0003-2635-4643Cahill Center for Astronomy and Astrophysics, California Institute of Technology , Pasadena, CA 91125, USA ; socker@caltech.edu; Observatories of the Carnegie Institution for Science , Pasadena, CA 91101, USACahill Center for Astronomy and Astrophysics, California Institute of Technology , Pasadena, CA 91125, USA ; socker@caltech.edu; Observatories of the Carnegie Institution for Science , Pasadena, CA 91101, USADepartment of Physics, University of California , Santa Barbara, CA 93106, USADepartment of Physics, Indian Institute of Science , Bengaluru 560012, IndiaThe circumgalactic medium (CGM) is poorly constrained at the subparsec scales relevant to turbulent energy dissipation and regulation of multiphase structure. Fast radio bursts are sensitive to small-scale plasma density fluctuations, which can induce multipath propagation (scattering). The amount of scattering depends on the density fluctuation spectrum, including its amplitude ${C}_{{\rm{n}}}^{2}$ , spectral index β , and dissipation scale l _i . We use quasar observations of CGM turbulence at ≳pc scales to infer ${C}_{{\rm{n}}}^{2}$ , finding it to be $1{0}^{-16}\lesssim {C}_{{\rm{n}}}^{2}\lesssim 1{0}^{-9}$ m ^−20/3 for hot ( T > 10 ^6 K) gas and $1{0}^{-8}\lesssim {C}_{{\rm{n}}}^{2}\lesssim 1{0}^{-4}$ m ^−20/3 for cool (10 ^4 ≲ T ≲ 10 ^5 K) gas, depending on the gas sound speed and density. These values of ${C}_{{\rm{n}}}^{2}$ are much smaller than those inferred in the interstellar medium at similar physical scales. The resulting scattering delays from the hot CGM are negligible (≪1 μ s at 1 GHz), but they are more detectable from the cool gas as either radio pulse broadening or scintillation, depending on the observing frequency and sightline geometry. Joint quasar-FRB observations of individual galaxies can yield lower limits on l _i , even if the CGM is not a significant scattering site. An initial comparison between quasar and FRB observations (albeit for different systems) suggests l _i ≳ 750 km in ∼10 ^4 K gas in order for the quasar and FRB constraints to be consistent. If a foreground CGM is completely ruled out as a source of scattering along an FRB sightline, then l _i may be comparable to the smallest cloud sizes (≲pc) inferred from photoionization modeling of quasar absorption lines.https://doi.org/10.3847/1538-4357/ade0bcCircumgalactic mediumRadio burstsQuasarsQuasar absorption line spectroscopyRadio transient sourcesExtragalactic radio sources |
| spellingShingle | Stella Koch Ocker Mandy C. Chen S. Peng Oh Prateek Sharma Microphysics of Circumgalactic Turbulence Probed by Fast Radio Bursts and Quasars The Astrophysical Journal Circumgalactic medium Radio bursts Quasars Quasar absorption line spectroscopy Radio transient sources Extragalactic radio sources |
| title | Microphysics of Circumgalactic Turbulence Probed by Fast Radio Bursts and Quasars |
| title_full | Microphysics of Circumgalactic Turbulence Probed by Fast Radio Bursts and Quasars |
| title_fullStr | Microphysics of Circumgalactic Turbulence Probed by Fast Radio Bursts and Quasars |
| title_full_unstemmed | Microphysics of Circumgalactic Turbulence Probed by Fast Radio Bursts and Quasars |
| title_short | Microphysics of Circumgalactic Turbulence Probed by Fast Radio Bursts and Quasars |
| title_sort | microphysics of circumgalactic turbulence probed by fast radio bursts and quasars |
| topic | Circumgalactic medium Radio bursts Quasars Quasar absorption line spectroscopy Radio transient sources Extragalactic radio sources |
| url | https://doi.org/10.3847/1538-4357/ade0bc |
| work_keys_str_mv | AT stellakochocker microphysicsofcircumgalacticturbulenceprobedbyfastradioburstsandquasars AT mandycchen microphysicsofcircumgalacticturbulenceprobedbyfastradioburstsandquasars AT spengoh microphysicsofcircumgalacticturbulenceprobedbyfastradioburstsandquasars AT prateeksharma microphysicsofcircumgalacticturbulenceprobedbyfastradioburstsandquasars |