The faint source population at 15.7 GHz - III. A high-frequency study of HERGs and LERGs
A complete sample of 96 faint ($S > 0.5$ mJy) radio galaxies is selected from the Tenth Cambridge (10C) survey at 15.7~GHz. Optical spectra are used to classify 17 of the sources as high-excitation or low-excitation radio galaxies (HERGs and LERGs respectively), for the remaining sources thre...
| Main Authors: | , , , |
|---|---|
| Format: | Journal article |
| Published: |
Oxford University Press
2016
|
| _version_ | 1797088029803806720 |
|---|---|
| author | Whittam, I Riley, J Green, D Jarvis, M |
| author_facet | Whittam, I Riley, J Green, D Jarvis, M |
| author_sort | Whittam, I |
| collection | OXFORD |
| description | A complete sample of 96 faint ($S > 0.5$ mJy) radio galaxies is selected from the Tenth Cambridge (10C) survey at 15.7~GHz. Optical spectra are used to classify 17 of the sources as high-excitation or low-excitation radio galaxies (HERGs and LERGs respectively), for the remaining sources three other methods are used; these are optical compactness, X-ray observations and mid-infrared colour--colour diagrams. 32 sources are HERGs and 35 are LERGs while the remaining 29 sources could not be classified. We find that the 10C HERGs tend to have higher 15.7-GHz flux densities, flatter spectra, smaller linear sizes and be found at higher redshifts than the LERGs. This suggests that the 10C HERGs are more core dominated than the LERGs. Lower-frequency radio images, linear sizes and spectral indices are used to classify the sources according to their radio morphology; 18 are Fanaroff and Riley type I or II sources, a further 13 show some extended emission, and the remaining 65 sources are compact and are referred to as FR0 sources. The FR0 sources are sub-divided into compact, steep-spectrum (CSS) sources (13 sources) or GHz-peaked spectrum (GPS) sources (10 sources) with the remaining 42 in an unclassified class. FR0 sources are more dominant in the subset of sources with 15.7-GHz flux densities $<$1 mJy, consistent with the previous result that the fainter 10C sources have flatter radio spectra. The properties of the 10C sources are compared to the higher-flux density Australia Telescope 20 GHz (AT20G) survey. The 10C sources are found at similar redshifts to the AT20G sources but have lower luminosities. The nature of the high-frequency selected objects change as flux density decreases; at high flux densities the objects are primarily quasars, while at low flux densities radio galaxies dominate. |
| first_indexed | 2024-03-07T02:44:04Z |
| format | Journal article |
| id | oxford-uuid:ab7165f9-1b4c-46c3-81e3-f198ea069778 |
| institution | University of Oxford |
| last_indexed | 2024-03-07T02:44:04Z |
| publishDate | 2016 |
| publisher | Oxford University Press |
| record_format | dspace |
| spelling | oxford-uuid:ab7165f9-1b4c-46c3-81e3-f198ea0697782022-03-27T03:21:55ZThe faint source population at 15.7 GHz - III. A high-frequency study of HERGs and LERGsJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:ab7165f9-1b4c-46c3-81e3-f198ea069778Symplectic Elements at OxfordOxford University Press2016Whittam, IRiley, JGreen, DJarvis, MA complete sample of 96 faint ($S > 0.5$ mJy) radio galaxies is selected from the Tenth Cambridge (10C) survey at 15.7~GHz. Optical spectra are used to classify 17 of the sources as high-excitation or low-excitation radio galaxies (HERGs and LERGs respectively), for the remaining sources three other methods are used; these are optical compactness, X-ray observations and mid-infrared colour--colour diagrams. 32 sources are HERGs and 35 are LERGs while the remaining 29 sources could not be classified. We find that the 10C HERGs tend to have higher 15.7-GHz flux densities, flatter spectra, smaller linear sizes and be found at higher redshifts than the LERGs. This suggests that the 10C HERGs are more core dominated than the LERGs. Lower-frequency radio images, linear sizes and spectral indices are used to classify the sources according to their radio morphology; 18 are Fanaroff and Riley type I or II sources, a further 13 show some extended emission, and the remaining 65 sources are compact and are referred to as FR0 sources. The FR0 sources are sub-divided into compact, steep-spectrum (CSS) sources (13 sources) or GHz-peaked spectrum (GPS) sources (10 sources) with the remaining 42 in an unclassified class. FR0 sources are more dominant in the subset of sources with 15.7-GHz flux densities $<$1 mJy, consistent with the previous result that the fainter 10C sources have flatter radio spectra. The properties of the 10C sources are compared to the higher-flux density Australia Telescope 20 GHz (AT20G) survey. The 10C sources are found at similar redshifts to the AT20G sources but have lower luminosities. The nature of the high-frequency selected objects change as flux density decreases; at high flux densities the objects are primarily quasars, while at low flux densities radio galaxies dominate. |
| spellingShingle | Whittam, I Riley, J Green, D Jarvis, M The faint source population at 15.7 GHz - III. A high-frequency study of HERGs and LERGs |
| title | The faint source population at 15.7 GHz - III. A high-frequency study of
HERGs and LERGs |
| title_full | The faint source population at 15.7 GHz - III. A high-frequency study of
HERGs and LERGs |
| title_fullStr | The faint source population at 15.7 GHz - III. A high-frequency study of
HERGs and LERGs |
| title_full_unstemmed | The faint source population at 15.7 GHz - III. A high-frequency study of
HERGs and LERGs |
| title_short | The faint source population at 15.7 GHz - III. A high-frequency study of
HERGs and LERGs |
| title_sort | faint source population at 15 7 ghz iii a high frequency study of hergs and lergs |
| work_keys_str_mv | AT whittami thefaintsourcepopulationat157ghziiiahighfrequencystudyofhergsandlergs AT rileyj thefaintsourcepopulationat157ghziiiahighfrequencystudyofhergsandlergs AT greend thefaintsourcepopulationat157ghziiiahighfrequencystudyofhergsandlergs AT jarvism thefaintsourcepopulationat157ghziiiahighfrequencystudyofhergsandlergs AT whittami faintsourcepopulationat157ghziiiahighfrequencystudyofhergsandlergs AT rileyj faintsourcepopulationat157ghziiiahighfrequencystudyofhergsandlergs AT greend faintsourcepopulationat157ghziiiahighfrequencystudyofhergsandlergs AT jarvism faintsourcepopulationat157ghziiiahighfrequencystudyofhergsandlergs |