astro 641 agn
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Astro 641 AGN. More material: This lecture!. Mapping the Evolution of AGN. 3C Radio Survey. Third (revised) Cambridge Catalogue of radio sources using extended emission at 178 MHz. Low selection frequency: steep spectra Survey of all sources north of -5 deg with f R >9 Jy. 328 sources. - PowerPoint PPT PresentationTRANSCRIPT
Astro 641 AGNAstro 641 AGN
Mapping the Evolution Mapping the Evolution of AGNof AGN
More material:
• This lecture!
3C Radio Survey3C Radio Survey
• Third (revised) Cambridge Catalogue of radio sources using extended emission at 178 MHz.
• Low selection frequency: steep spectra
• Survey of all sources north of -5 deg with fR>9 Jy. 328 sources.
• Complete sample: Laing, Riley and Longair (1983). 96% complete to 10 Jy.
V/VV/Vmaxmax Test Test• Flux-limited sample --> at small
distances larger luminosity range.
• Solution: compute for each source the max. redshift at which it would still be included in a complete survey --> maximum volume Vmax.
• V/Vmax is a measure of the source position within the observable volume.
• V/Vmax uniform in [0,1] range.
• <V/Vmax>=0.5.
Power-law AGNPower-law AGN
Donley et al. (2008)
Selection: IRAC photometry is well-fit by a line of slope <-0.5
Fiore et al. 2008
Finding Heavily-Obscured AGNFinding Heavily-Obscured AGN
Mid-IRMid-IR X-ray StackingX-ray Stacking
FF2424/F/FRR>1000>1000
FF2424/F/FRR<200<200
• 4 detection in X-ray stack. Hard spectral shape, harder than X-ray detected sources.Good CT AGN candidates.• Similar results found by Daddi et al. (2007)
Rest-Frame StackingRest-Frame Stacking
Good fit with either NH1023cm-2 or combination of CT AGN with star-forming galaxies.
Consistent results with observed-frame stacking.
Treister et al. ApJ 2009c
X-Ray to Mid-IR RatioX-Ray to Mid-IR Ratio
~100x lower ratio for X-ray undetected sources.
Explained by NH~5x1024 to 1025cm-2
Treister et al. ApJ 2009c
Both X-rays and 12µm good tracers of AGN activity.
X-Ray to Mid-IR RatioX-Ray to Mid-IR Ratio
Ratio for sources with L12µm>1043erg/s (~80% of the sources) ~2-3x higher than star-forming galaxies
Treister et al. ApJ 2009c
Near to Mid-IR ColorsNear to Mid-IR Colors- Distributions significantly different- X-ray detected sources much bluer- Average f8/f24=0.2 for X-ray sources and 0.04 for X-ray undetected sample
BluerRedder
Well explained by different viewing angle (30o vs 90o) in the same torus model Can it be star-formation versus AGN?
Treister et al. ApJ 2009c