On the origin of radio core emission in radio-quiet quasars
We present a model for the radio emission from radio-quiet quasar nuclei. We show that a thermal origin for the high brightness temperature, flat spectrum point sources (known as radio ``cores'') is possible provided the emitting region is hot and optically-thin. We hence demonstrate that...
| Main Authors: | , |
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| Format: | Journal article |
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2007
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| _version_ | 1826279069662052352 |
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| author | Blundell, K Kuncic, Z |
| author_facet | Blundell, K Kuncic, Z |
| author_sort | Blundell, K |
| collection | OXFORD |
| description | We present a model for the radio emission from radio-quiet quasar nuclei. We show that a thermal origin for the high brightness temperature, flat spectrum point sources (known as radio ``cores'') is possible provided the emitting region is hot and optically-thin. We hence demonstrate that optically-thin bremsstrahlung from a slow, dense disk wind can make a significant contribution to the observed levels of radio core emission. This is a much more satisfactory explanation, particularly for sources where there is no evidence of a jet, than a sequence of self-absorbed synchrotron components which collectively conspire to give a flat spectrum. Furthermore, such core phenomena are already observed directly via milli-arcsecond radio imaging of the Galactic microquasar SS433 and the active galaxy NGC1068. We contend that radio-emitting disk winds must be operating at some level in radio-loud quasars and radio galaxies as well (although in these cases, observations of the radio cores are frequently contaminated/dominated by synchrotron emission from jet knots). This interpretation of radio core emission mandates mass accretion rates that are substantially higher than Eddington. Moreover, acknowledgment of this mass-loss mechanism as an AGN feedback process has important implications for the input of energy and hot gas into the inter-galactic medium (IGM) since it is considerably less directional than that from jets. |
| first_indexed | 2024-03-06T23:53:19Z |
| format | Journal article |
| id | oxford-uuid:735d7b7c-3078-4d5f-abdc-dd7ac7a24a1d |
| institution | University of Oxford |
| last_indexed | 2024-03-06T23:53:19Z |
| publishDate | 2007 |
| record_format | dspace |
| spelling | oxford-uuid:735d7b7c-3078-4d5f-abdc-dd7ac7a24a1d2022-03-26T19:55:56ZOn the origin of radio core emission in radio-quiet quasarsJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:735d7b7c-3078-4d5f-abdc-dd7ac7a24a1dSymplectic Elements at Oxford2007Blundell, KKuncic, ZWe present a model for the radio emission from radio-quiet quasar nuclei. We show that a thermal origin for the high brightness temperature, flat spectrum point sources (known as radio ``cores'') is possible provided the emitting region is hot and optically-thin. We hence demonstrate that optically-thin bremsstrahlung from a slow, dense disk wind can make a significant contribution to the observed levels of radio core emission. This is a much more satisfactory explanation, particularly for sources where there is no evidence of a jet, than a sequence of self-absorbed synchrotron components which collectively conspire to give a flat spectrum. Furthermore, such core phenomena are already observed directly via milli-arcsecond radio imaging of the Galactic microquasar SS433 and the active galaxy NGC1068. We contend that radio-emitting disk winds must be operating at some level in radio-loud quasars and radio galaxies as well (although in these cases, observations of the radio cores are frequently contaminated/dominated by synchrotron emission from jet knots). This interpretation of radio core emission mandates mass accretion rates that are substantially higher than Eddington. Moreover, acknowledgment of this mass-loss mechanism as an AGN feedback process has important implications for the input of energy and hot gas into the inter-galactic medium (IGM) since it is considerably less directional than that from jets. |
| spellingShingle | Blundell, K Kuncic, Z On the origin of radio core emission in radio-quiet quasars |
| title | On the origin of radio core emission in radio-quiet quasars |
| title_full | On the origin of radio core emission in radio-quiet quasars |
| title_fullStr | On the origin of radio core emission in radio-quiet quasars |
| title_full_unstemmed | On the origin of radio core emission in radio-quiet quasars |
| title_short | On the origin of radio core emission in radio-quiet quasars |
| title_sort | on the origin of radio core emission in radio quiet quasars |
| work_keys_str_mv | AT blundellk ontheoriginofradiocoreemissioninradioquietquasars AT kuncicz ontheoriginofradiocoreemissioninradioquietquasars |