On the redshift cut-off for flat-spectrum radio sources
We use data from the Parkes Half-Jansky Flat-Spectrum (PHJFS) sample (Drinkwater et al. 1997) to constrain the cosmic evolution in the co-moving space density of radio sources in the top decade of the flat-spectrum radio luminosity function (RLF). A consistent picture for the high-redshift evolution...
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| Format: | Journal article |
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2000
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| _version_ | 1826273010485559296 |
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| author | Jarvis, M Rawlings, S |
| author_facet | Jarvis, M Rawlings, S |
| author_sort | Jarvis, M |
| collection | OXFORD |
| description | We use data from the Parkes Half-Jansky Flat-Spectrum (PHJFS) sample (Drinkwater et al. 1997) to constrain the cosmic evolution in the co-moving space density of radio sources in the top decade of the flat-spectrum radio luminosity function (RLF). A consistent picture for the high-redshift evolution is achieved using both simple parametric models, which are the first to allow for distributions in both radio luminosity and spectral index, and variants of the V / V_max test, some of which incorporate the effects of radio spectral curvature. For the most luminous flat-spectrum objects, the PHJFS sample is extremely similar to that used by Shaver et al. (1996, 1998) to argue for an abrupt `redshift cut-off': a decrease by a factor ~30 in space density between a peak redshift z~2.5 and z~5. Our analysis finds that the observable co-moving volume is too small to make definitive statements about any redshift cut-off for the most luminous flat-spectrum sources, although both constant-space density (no cut-off) models and models with cut-offs as abrupt as those envisaged by Shaver et al. are outside the 90% confidence region. The inference that the decline in space density is most likely to be gradual, by a factor ~4 between z~2.5 and z~5, is in accordance with previous work on the RLF by Dunlop and Peacock (1990), but different to the abrupt decline favoured by studies of optically-selected quasars. Dust obscuration provides one explanation for this difference. We show that a significant fraction of the most radio-luminous flat-spectrum objects are Giga-Hertz Peaked Spectrum (GPS) rather than Doppler-Boosted (DB) sources, complicating any interpretation of the redshift cut-off. |
| first_indexed | 2024-03-06T22:21:38Z |
| format | Journal article |
| id | oxford-uuid:554069d3-6352-4e89-ac93-9f868b983c57 |
| institution | University of Oxford |
| last_indexed | 2024-03-06T22:21:38Z |
| publishDate | 2000 |
| record_format | dspace |
| spelling | oxford-uuid:554069d3-6352-4e89-ac93-9f868b983c572022-03-26T16:42:51ZOn the redshift cut-off for flat-spectrum radio sourcesJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:554069d3-6352-4e89-ac93-9f868b983c57Symplectic Elements at Oxford2000Jarvis, MRawlings, SWe use data from the Parkes Half-Jansky Flat-Spectrum (PHJFS) sample (Drinkwater et al. 1997) to constrain the cosmic evolution in the co-moving space density of radio sources in the top decade of the flat-spectrum radio luminosity function (RLF). A consistent picture for the high-redshift evolution is achieved using both simple parametric models, which are the first to allow for distributions in both radio luminosity and spectral index, and variants of the V / V_max test, some of which incorporate the effects of radio spectral curvature. For the most luminous flat-spectrum objects, the PHJFS sample is extremely similar to that used by Shaver et al. (1996, 1998) to argue for an abrupt `redshift cut-off': a decrease by a factor ~30 in space density between a peak redshift z~2.5 and z~5. Our analysis finds that the observable co-moving volume is too small to make definitive statements about any redshift cut-off for the most luminous flat-spectrum sources, although both constant-space density (no cut-off) models and models with cut-offs as abrupt as those envisaged by Shaver et al. are outside the 90% confidence region. The inference that the decline in space density is most likely to be gradual, by a factor ~4 between z~2.5 and z~5, is in accordance with previous work on the RLF by Dunlop and Peacock (1990), but different to the abrupt decline favoured by studies of optically-selected quasars. Dust obscuration provides one explanation for this difference. We show that a significant fraction of the most radio-luminous flat-spectrum objects are Giga-Hertz Peaked Spectrum (GPS) rather than Doppler-Boosted (DB) sources, complicating any interpretation of the redshift cut-off. |
| spellingShingle | Jarvis, M Rawlings, S On the redshift cut-off for flat-spectrum radio sources |
| title | On the redshift cut-off for flat-spectrum radio sources |
| title_full | On the redshift cut-off for flat-spectrum radio sources |
| title_fullStr | On the redshift cut-off for flat-spectrum radio sources |
| title_full_unstemmed | On the redshift cut-off for flat-spectrum radio sources |
| title_short | On the redshift cut-off for flat-spectrum radio sources |
| title_sort | on the redshift cut off for flat spectrum radio sources |
| work_keys_str_mv | AT jarvism ontheredshiftcutoffforflatspectrumradiosources AT rawlingss ontheredshiftcutoffforflatspectrumradiosources |