Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.atnf.csiro.au/research/Astro2008/Postings/Elizabeth_Mahony.pdf Дата изменения: Thu Jun 26 05:00:14 2008 Дата индексирования: Sat Sep 6 19:13:20 2008 Кодировка: Поисковые слова: star

Active Galaxies at High Radio Frequencies
Elizabeth Mahony (USYD), Elaine Sadler (USYD), Ron Ekers (ATNF), Ilana Feain (ATNF) and the AT20G team




Provides high frequency flux calibrators for the next generation of radio surveys Important for active galaxy evolution and future CMB missions such as PLANCK ...and to search for black hole mergers









5450 sources from 0o-90o, excluding galactic plane |b|<1.5o Flux limited at 40mJy, complete to 60mJy ~80% also have near simultaneous measurements at 5 and 8 GHz (all sources south of -15o)








Crossmatched the entire survey with the SuperCOSMOS database, complete to B=22 4016 (74%) sources with optical counterparts, majority (71%) are candidate QSOs Searched the 6dFGS and NED for redshift information 19% of sources have redshifts










Median redshift is z=1.12 Highest redshift at z=4.63






A correlation between optical luminosity and radio luminosity for QSOs selected at 20GHz Significant at 99% confidence level Only observed for AT20G QSOs, not for Galaxies




Owen & Mufson (1977) found a similar correlation for a small sample of QSOs observed at 90GHz Correlation not observed in QSO samples selected at 1.4GHz i.e. the FIRST Bright QSO sample (Becker et al. 2001). Suggests a link between the radiation mechanisms in the optical and radio regimes













Investigate the properties of radio-loud QSOs selected at high-frequency, and compare them with QSOs selected at lower radio frequencies, in X-rays and optically. Test whether the radio-optical correlation in AT20G QSOs might be due to relativistic beaming effects, using measurements of the line/continuum ratio from optical spectra. Observe a larger sample of QSOs at 20GHz and measure their radio spectral-energy distributions. Could also carry out eVLBI observations of the most luminous AT20G QSOs to test beaming models and determine radio-source morphology.






By selecting at high frequencies the sample becomes dominated by QSOs QSOs are ideal in searching for merging black holes since they are bright over a wide range of redshifts eVLBI imaging of these sources would reveal any binary black holes Optical spectra would also be informative ­ sources with double peaked emission lines could be evidence of a binary black hole system




Ingredients: 5 ATCA dishes 1 Wideband correlator Method: Scan the sky at 20GHz down to flux limit of 40mJy Then observe candidate sources individually Observe confirmed detections at 5 & 8 GHz as well