Active Galactic Nuclei: a brief introduction
Manel Errando Washington University in St. Louis The discovery of quasars 3C 273: The first AGN
z=0.158
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• The luminosity (L) of quasars, i.e. how bright they are, can be as high as Lquasar ~ 1012 Lsun ~ 1040 W. • The energy source of quasars is accretion power: - Nuclear fusion: 2 11 1 E =0.007 mc =6 10 W s g nucl ⇥ · · - Accretion power: 13 1 E = GMm/R =3 10 W s g acc ⇥ · ·
Accretion, i.e matter falling onto a black hole is the only energy source that is powerful enough to fuel the very bright luminosity of quasars.
3 The discovery of quasars 3C 273: The first AGN
The First Texas Symposium on Relativistic Astrophysics - 16-18 December 1963
4 Quasar BL Lac
• Characteristics • Bright compact nucleus • Time variability
• Unified model • Supermassive black hole • Rotating accretion disk • Perspective to observer, accretion rate and BH mass determines the kind of AGN.
6 AGN
7 AGN
Active Galactic Nuclei A few % of all galaxies
Radio-quiet Radio-loud 85%-95% 5%-15%
Spirals QSOs Ellipticals Blazars The most common class of AGN Quasi-Stellar Objects <5% of all AGN
Seyfert 1 Seyfert 2 Fanharoff-Riley BL Lacs Have both broad lines and Show only narrow Featureless optical spectrum narrow lines of ionized metals lines of all species Galaxies
FR1 FR2 LBLs HBLs Low luminosity High luminosity Low peaked High peaked
5%-10% are radio loud FSRQs Flat Spectrum Radio Quasars
8 Black Holes and Relativistic jets
• Supermassive black holes: 106-109 M☉ • Active Galactic Nuclei (AGN) • Outflows of particles and radiation: relativistic jets. • Aligned to our line of sight: Blazars. • See them from radio to gamma-ray energies. • Their emission is highly variable.
10-9 ]
-1 SMA s
-2 VLBA_core(BP143) VLBA(BP143) 10-10 VLBA(BK150) Metsahovi [erg cm
ν Noto F
ν VLBA_core(MOJAVE) 10-11 VLBA(MOJAVE) OVRO RATAN Medicina Swift/UVOT MAGIC 10-12 Effelsberg ROVOR Fermi NewMexicoSkies Swift/BAT MITSuME RXTE/PCA GRT Swift/XRT -13 10 GASP
WIRO OAGH
10-14 1010 1012 1014 1016 1018 1020 1022 1024 1026 1028 ν [Hz] Radio IR-optical-UV X-ray Fermi VHE
9 Leptonic models ν ν F
E • γsync Soft photon population: • SSC: synchrotron photons Inverse Compton • Emission from the disk e- scattering • Broad Line Region γVHE Synchrotron • Reprocessed emission from the dust γsoft radiation torus e- 10 Correlated variability
γsync
γ ν VHE γsync ν F e-
e-
E 1ES 1959+650
Krawczynski et al. 2004
11 Periodic variability from AGN jets
PKS 2155-204 P1~1.7 years P2~0.7 years P1+P2→29% var
12 Galaxy evolution in a nutshell
supermassive BH + supermassive BH
supermassive BH binary
supermassive BH merger
The periodic variability could be due to two supermassive black holes orbiting around each other. 13 Summary
• There is a lot we don’t yet know about how supermassive black holes grow, and how they shape star formation in their host galaxies. • Radiation from accreting supermassive black holes (AGN) is the best tracer we have of black hole evolution. • Basic models exist that explain the radiation we observe from relativistic jets. • Most models break down when observational data becomes more abundant and more detailed.
14 References
Active Galactic Nuclei - Robson Accretion power in astrophysics - Frank, King & Raine High Energy Astrophysics - Longair
Email me if you have further questions: [email protected]
15 Using python to study astrophysical catalogs
• We will now spend 15 min talking about astrophysical catalogs. • A catalog is generally the result of a very detailed analysis of a large amount of astrophysical data. • It differs from a single source analysis in that it aims at understanding the properties of a population of sources, rather than on individual objects. • We will use as an example the Fermi-LAT 4FGL catalog. It summarizes the properties of all gamma-ray sources that Fermi, a gamma-ray satellite, has detected in about 10 years of operation. - https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermilpsc.html • You can find and download the code that I will run here: - https://confluence.slac.stanford.edu/download/attachments/ 249335606/BL_Lacs_catalog_sample.ipynb? version=1&modificationDate=1559398718000&api=v2
16 The Fermi-LAT 4FGL catalog
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