Star Formation in AGN hostsStar Formation in AGN hosts
Li Shao&
PACS Evolutionary Probe (PEP) group
Hangzhou, ChinaApril 28, 2011
Evidence from Herschel PACSEvidence from Herschel PACS
Linking AGN and HostLinking AGN and Host• BH growth and
host star formation both need gas feeding mechanism
• Empirical relations– MBH-sigma– MBH-M*
imply strong link between BH growth and host formation
Ferrarese & Ford 05
Marconi & Hunt 03
Our approachOur approach• X-ray selected AGN
– Deep Chandra or XMM surveys in GOODS and COSMOS
– Good multi-wavelength coverage, redshifts and identifications are ready
• Star formation rate estimated from far-IR– Greatly improved sensitivity and spatial
resolution with Herschel-PACS– PACS can measure rest frame 60um out to z~2
Far-infrared emission isFar-infrared emission is host dominated host dominated
Netzer+07
PACS Detection RatesPACS Detection Rates• ~20% in GOODS-N of
2Ms Chandra sources• For non-detections
we use stacking
• ~40% in GOODS-S with deeper PACS data
Break L-z DegeneracyBreak L-z Degeneracy
• We have sufficient statistics to do the analysis in bins of both LX and z simultaneously
• In each bin, the IR luminosity is weighted average of the detections and the stacking of the non-detections
Shao+10
Merger vs. SecularMerger vs. Secular
Merger vs. SecularMerger vs. Secular
Hopkins+06
Merger scenario
Merger vs. SecularMerger vs. Secular
Genzel+06,08
BzK-15504 z~2.38 rotating disk with central AGN
Star formation vs. obscuration?Star formation vs. obscuration?
Hopkins+08
Star formation vs. obscuration?Star formation vs. obscuration?
Hopkins+08
High obscuration (dusty) and high SFR (ULIRG)
Low obscuration (quasar) and low SFR (quenched)
Correlation expected!
But…But…
Shao+10
• No trend for z~1 moderate luminosity X-ray AGN in GOODS-N
But…But…• No trend for z~1
moderate luminosity X-ray AGN in GOODS-N
• Still no trend for high luminosity COSMOS AGN, with good statistics
Shao+10
SummarySummary
• We use the rest-frame far-infrared luminosity to measure AGN host star formation rates
• We have enough statistics to break the redshift/luminosity degeneracy
• We propose two modes of AGN/host co-evolution– Merger like scenario for high LAGN
– Secular evolution for low LAGN
• No trend of LIR with AGN obscuration, details of the merger model need further understanding
Thanks to PEP team and F. Bauer, D. Alexander, N. Brandt, M. Brusa, V. Mainieri, M. Salvato, G. Hasinger, and many others