Observational Evidence of AGN Feedback

28 Pages·2012·0.45 MB·English

by  Andy Fabian

Introduction
TheradiativeorWindMode
ThekineticMode
BaryonProfilesmassscalesandAGNfeedback
Futurestudies
Summary
Observational Evidence of AGN Feedback
AndyFabian
10demaiode2012
AndyFabian ObservationalEvidenceofAGNFeedback
Introduction
TheradiativeorWindMode
ThekineticMode
BaryonProfilesmassscalesandAGNfeedback
Futurestudies
Summary
Sumário
Introduction
TheradiativeorWindMode
AGNwinds
Galaxyoutflows
FromthepeaktothelateevolutionofAGNandquasars
Mergersorsecularevolution?
ThekineticMode
StrongEvidences
Heating/CoolingBalance
Cool,ColdGasandStarFormation
Theevolutionofcoolcoreinclusters
Themostluminousclusters
Hotgasingroupsandellipticalgalaxies
BaryonProfilesmassscalesandAGNfeedback
Futurestudies
Summary
AndyFabian ObservationalEvidenceofAGNFeedback
Introduction
TheradiativeorWindMode
ThekineticMode
BaryonProfilesmassscalesandAGNfeedback
Futurestudies
Summary
The AGN feedback
◮ Theinteractionprocessbetweentheblackholeatthecentreofagalaxyandthe
galaxyisknownasAGNfeedback.
◮ Ittakesplacethroughaninteractionbetweentheenergyandradiationgenerated
byaccretionontothemassiveblackholeandthegasinthehostgalaxy.
◮ Thedetailsofthefeedbackarecomplexandtheobservationalevidenceisnot
alwaysclear.
AndyFabian ObservationalEvidenceofAGNFeedback
Introduction
TheradiativeorWindMode
ThekineticMode
BaryonProfilesmassscalesandAGNfeedback
Futurestudies
Summary
Kinds of AGN feedback
◮ Twomajormodeshavebeenidentified,differentiatedbythenatureoftheenergy
outflowneartheblackhole:
◮ theradiativemode(quasarorwindmode):whentheaccretingblackholewasclose
totheEddingtonlimit.
◮ thekinecticmode(radiojetormaintencemode):whenthegalaxyhasahothalo
andtheaccretingblackholehaspowerfuljets.
AndyFabian ObservationalEvidenceofAGNFeedback
Introduction
TheradiativeorWindMode
ThekineticMode
BaryonProfilesmassscalesandAGNfeedback
Futurestudies
Summary
Effects
◮ Thegrowthofthecentralblackholebyaccretioncanhaveaprofoundeffectonits
hostgalaxy.
◮ Accretionenergydoesn’tsignificantlyaffectthestaralreadyexisting,butitcan
couplestronglywiththegasfromwhichnewstarforms.
◮ ThereislittleornoevidenceatthepresenttimeforAGNfeedbackoperatinginlow
massgalaxieswherestellarfeedbackisimportant.
◮ TheclearestobservationalevidenceforAGNfeedbackisfoundinthemost
massivegalaxiesknown,BCGincoolcoreclusters.
◮ AGNfeedbackisarelativelyyoungtopic,andawiderangeofargumentand
opinionhasbeenexpressed.
AndyFabian ObservationalEvidenceofAGNFeedback
Introduction
TheradiativeorWindMode AGNwinds
ThekineticMode Galaxyoutflows
BaryonProfilesmassscalesandAGNfeedback FromthepeaktothelateevolutionofAGNandquasars
Futurestudies Mergersorsecularevolution?
Summary
Accretion in galaxies
◮ Theequationwhichcanpreventtheaccretionintoagalaxyatthemaximum
possibleratebyaquasarattheEddingtonlimitis:
fσ4σ
MBH = πG2mTp (1)
whereσ istheThomsoncrosssectionforelectronscatteringandfisthefractionof
T
thegalaxymassingas.
◮ TheagreementthatthissimpleformulagiveswiththeobservedMBH−σrelation
canbeinterpretedas(weak)observationalevidenceforAGNfeedback.
AndyFabian ObservationalEvidenceofAGNFeedback
Introduction
TheradiativeorWindMode AGNwinds
ThekineticMode Galaxyoutflows
BaryonProfilesmassscalesandAGNfeedback FromthepeaktothelateevolutionofAGNandquasars
Futurestudies Mergersorsecularevolution?
Summary
◮ Ifthemaininteractionisduetowinds,nottoradiationpressure,thenthewind
needstohaveahighcolumndensityN,highvelocityν,highcoverginfractionfall
atlargeradiusr.Thekineticluminosityofawindis:
Lw = f r ν 3 N (2)
LEDD 2rg (cid:18)cc(cid:19) NT
◮ ToproduceMBH ∝σ4scalingthethrustofthewindneedstobeproportionalto
theEddingtonlimit.
◮ ThecommonestwayinwhichAGNwindsareobservedisbylineabsorptionofthe
quasarcontinuumbyinterveningwindmaterial.
◮ Generally,goodevidenceforAGNwindsoccursinunobscuredAGN,wherethe
UVspectrumcanbedirectlyseen.
AndyFabian ObservationalEvidenceofAGNFeedback
Introduction
TheradiativeorWindMode AGNwinds
ThekineticMode Galaxyoutflows
BaryonProfilesmassscalesandAGNfeedback FromthepeaktothelateevolutionofAGNandquasars
Futurestudies Mergersorsecularevolution?
Summary
Galaxy outflows
◮ EvidencesofAGNfeedbackisclearlyseen
insomegalacticoutflows.
◮ AnimportantobjectwhereboththeAGN
andouftlowareseenisthelowredshift,z=
0.04,quasar/mergerMrk231.
◮ Ithaveavelocityof∼1100kms−1andan
ouflowrateof420M⊙yr−1,severaltimes
greaterthanthestarformationrate.
AndyFabian ObservationalEvidenceofAGNFeedback
Introduction
TheradiativeorWindMode AGNwinds
ThekineticMode Galaxyoutflows
BaryonProfilesmassscalesandAGNfeedback FromthepeaktothelateevolutionofAGNandquasars
Futurestudies Mergersorsecularevolution?
Summary
The downsizing of AGN
◮ Itwasanimportantdiscovery.
◮ ThemostluminousandmassiveAGNweremostnumerousatreshiftsof2-2.5,
theless-luminouspeakedatsuccessivelylowerredshiftswiththeleastluminous
peakingaroundredshiftone.
◮ DownsizingofAGNwasfirstseeninX-raysurveys.
◮ ThebehaviouristheoppositeofwhatissimplypredictedinahierarchicalCDM
universe,wherethemostmassiveobjectsformlast.
◮ Itindicatesthatsomethingisquenchingquasarbehaviourandthemostwidely
acceptedsolutionisthatisisduetoAGNfeedback.
AndyFabian ObservationalEvidenceofAGNFeedback
Introduction
TheradiativeorWindMode AGNwinds
ThekineticMode Galaxyoutflows
BaryonProfilesmassscalesandAGNfeedback FromthepeaktothelateevolutionofAGNandquasars
Futurestudies Mergersorsecularevolution?
Summary
◮ Manytheoreticalmodelsforquasarevolutionarebasedongalaxy-galaxymergers
beingthetriggerforgasinfallontoablackhole.
◮ ButtheevidenceforthemtriggeringAGNisweak.
◮ Theevidenceisbuildingthatbetweenredshiftsof2andthecurrentepoch,much
oftheevolutionofAGNissecular.
AndyFabian ObservationalEvidenceofAGNFeedback