COS-EDGES: Co-rotation and Kinematic Stratification of the Multi-Phase CGM Around Edge-On Galaxies
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| Natura: | Preprint |
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2025
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| author | Kacprzak, Glenn G. Oppenheimer, Benjamin D. Nielsen, Nikole M. Fernandez-Figueroa, Antonia Murphy, Michael T. Allen, Rebecca J. Barone, Tania M. Sameer Churchill, Christopher W. Burchett, Joseph N. Gupta, Kaustubh R. Charlton, Jane C. Platukis, Caleb B. |
| author_facet | Kacprzak, Glenn G. Oppenheimer, Benjamin D. Nielsen, Nikole M. Fernandez-Figueroa, Antonia Murphy, Michael T. Allen, Rebecca J. Barone, Tania M. Sameer Churchill, Christopher W. Burchett, Joseph N. Gupta, Kaustubh R. Charlton, Jane C. Platukis, Caleb B. |
| contents | We present the first results from the COS-EDGES survey, targeting the kinematic connection between the ISM and multi-phase circumgalactic medium (CGM) in nine isolated, edge-on galaxies at z~0.2, each probed along its major axis by a background quasar at impact parameters of 13-38kpc. Using VLT/UVES and HST/COS quasar spectra, we analyse MgI, MgII, HI, CII, CIII, and OVI absorption relative to galaxy rotation curves from Keck/LRIS and Magellan/MagE spectra. We find that at lower $D/R_{vir}$ ($D/R_{vir}\leq 0.2$), over 80% of absorption in all ions lies on the side of systemic velocity matching disk rotation, and the optical-depth-weighted median velocity ($v_{abs}$) is consistent with the peak rotation speed. At higher $D/R_{vir}$ ($D/R_{vir} > 0.2$), the kinematics diverge by ionisation state: For low ionisation gas, the amount of co-rotating absorption remains >80%, yet $v_{abs}$ drops to 60% of the galaxy rotation speed. For high ionisation gas (OVI), only 60% of the absorption is consistent with co-rotation and $v_{abs}$ drops to 20% of the rotation speed. Furthermore, the velocity widths, corresponding to 50% of the total optical depth ($Δv_{50}$) for low ionisation gas is 1.8 times larger in the inner halo than at larger radii, while for CIII and OVI $Δv_{50}$ remains unchanged with distance. These results suggest a radially dependent CGM kinematic structure: the inner halo hosts cool, dynamically broad gas tightly coupled to disk rotation, whereas beyond 0.2$R_{vir}$, particularly traced by OVI and HI, the CGM shows weaker rotational alignment and lower velocity dispersion. Therefore, low-ionisation gas likely traces extended co-rotating gas, inflows and/or recycled accretion, while high-ionisation gas reflects a mixture of co-rotating, lagging, discrete collisionally ionised structures, indicating a kinematic stratification of the multi-phase CGM. [Abridged] |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2507_11613 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | COS-EDGES: Co-rotation and Kinematic Stratification of the Multi-Phase CGM Around Edge-On Galaxies Kacprzak, Glenn G. Oppenheimer, Benjamin D. Nielsen, Nikole M. Fernandez-Figueroa, Antonia Murphy, Michael T. Allen, Rebecca J. Barone, Tania M. Sameer Churchill, Christopher W. Burchett, Joseph N. Gupta, Kaustubh R. Charlton, Jane C. Platukis, Caleb B. Astrophysics of Galaxies We present the first results from the COS-EDGES survey, targeting the kinematic connection between the ISM and multi-phase circumgalactic medium (CGM) in nine isolated, edge-on galaxies at z~0.2, each probed along its major axis by a background quasar at impact parameters of 13-38kpc. Using VLT/UVES and HST/COS quasar spectra, we analyse MgI, MgII, HI, CII, CIII, and OVI absorption relative to galaxy rotation curves from Keck/LRIS and Magellan/MagE spectra. We find that at lower $D/R_{vir}$ ($D/R_{vir}\leq 0.2$), over 80% of absorption in all ions lies on the side of systemic velocity matching disk rotation, and the optical-depth-weighted median velocity ($v_{abs}$) is consistent with the peak rotation speed. At higher $D/R_{vir}$ ($D/R_{vir} > 0.2$), the kinematics diverge by ionisation state: For low ionisation gas, the amount of co-rotating absorption remains >80%, yet $v_{abs}$ drops to 60% of the galaxy rotation speed. For high ionisation gas (OVI), only 60% of the absorption is consistent with co-rotation and $v_{abs}$ drops to 20% of the rotation speed. Furthermore, the velocity widths, corresponding to 50% of the total optical depth ($Δv_{50}$) for low ionisation gas is 1.8 times larger in the inner halo than at larger radii, while for CIII and OVI $Δv_{50}$ remains unchanged with distance. These results suggest a radially dependent CGM kinematic structure: the inner halo hosts cool, dynamically broad gas tightly coupled to disk rotation, whereas beyond 0.2$R_{vir}$, particularly traced by OVI and HI, the CGM shows weaker rotational alignment and lower velocity dispersion. Therefore, low-ionisation gas likely traces extended co-rotating gas, inflows and/or recycled accretion, while high-ionisation gas reflects a mixture of co-rotating, lagging, discrete collisionally ionised structures, indicating a kinematic stratification of the multi-phase CGM. [Abridged] |
| title | COS-EDGES: Co-rotation and Kinematic Stratification of the Multi-Phase CGM Around Edge-On Galaxies |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2507.11613 |