Do high-velocity clouds form by thermal instability?
We examine the proposal that the HI "high-velocity" clouds (HVCs) surrounding the Milky Way and other disc galaxies form by condensation of the hot galactic corona via thermal instability. Under the assumption that the galactic corona is well represented by a non-rotating, stratified atmos...
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| Format: | Journal article |
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2009
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| _version_ | 1826293897626648576 |
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| author | Binney, J Nipoti, C Fraternali, F |
| author_facet | Binney, J Nipoti, C Fraternali, F |
| author_sort | Binney, J |
| collection | OXFORD |
| description | We examine the proposal that the HI "high-velocity" clouds (HVCs) surrounding the Milky Way and other disc galaxies form by condensation of the hot galactic corona via thermal instability. Under the assumption that the galactic corona is well represented by a non-rotating, stratified atmosphere, we find that for this formation mechanism to work the corona must have an almost perfectly flat entropy profile. In all other cases the growth of thermal perturbations is suppressed by a combination of buoyancy and thermal conduction. Even if the entropy profile were nearly flat, cold clouds with sizes smaller than 10 kpc could form in the corona of the Milky Way only at radii larger than 100 kpc, in contradiction with the determined distances of the largest HVC complexes. Clouds with sizes of a few kpc can form in the inner halo only in low-mass systems. We conclude that unless even slow rotation qualitatively changes the dynamics of a corona, thermal instability is unlikely to be a viable mechanism for formation of cold clouds around disc galaxies. |
| first_indexed | 2024-03-07T03:37:15Z |
| format | Journal article |
| id | oxford-uuid:bcb57c32-330a-4bc1-a813-5e294d6c0f6e |
| institution | University of Oxford |
| last_indexed | 2024-03-07T03:37:15Z |
| publishDate | 2009 |
| record_format | dspace |
| spelling | oxford-uuid:bcb57c32-330a-4bc1-a813-5e294d6c0f6e2022-03-27T05:26:21ZDo high-velocity clouds form by thermal instability?Journal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:bcb57c32-330a-4bc1-a813-5e294d6c0f6eSymplectic Elements at Oxford2009Binney, JNipoti, CFraternali, FWe examine the proposal that the HI "high-velocity" clouds (HVCs) surrounding the Milky Way and other disc galaxies form by condensation of the hot galactic corona via thermal instability. Under the assumption that the galactic corona is well represented by a non-rotating, stratified atmosphere, we find that for this formation mechanism to work the corona must have an almost perfectly flat entropy profile. In all other cases the growth of thermal perturbations is suppressed by a combination of buoyancy and thermal conduction. Even if the entropy profile were nearly flat, cold clouds with sizes smaller than 10 kpc could form in the corona of the Milky Way only at radii larger than 100 kpc, in contradiction with the determined distances of the largest HVC complexes. Clouds with sizes of a few kpc can form in the inner halo only in low-mass systems. We conclude that unless even slow rotation qualitatively changes the dynamics of a corona, thermal instability is unlikely to be a viable mechanism for formation of cold clouds around disc galaxies. |
| spellingShingle | Binney, J Nipoti, C Fraternali, F Do high-velocity clouds form by thermal instability? |
| title | Do high-velocity clouds form by thermal instability? |
| title_full | Do high-velocity clouds form by thermal instability? |
| title_fullStr | Do high-velocity clouds form by thermal instability? |
| title_full_unstemmed | Do high-velocity clouds form by thermal instability? |
| title_short | Do high-velocity clouds form by thermal instability? |
| title_sort | do high velocity clouds form by thermal instability |
| work_keys_str_mv | AT binneyj dohighvelocitycloudsformbythermalinstability AT nipotic dohighvelocitycloudsformbythermalinstability AT fraternalif dohighvelocitycloudsformbythermalinstability |