Post on 12-Jan-2016
description
Active Galaxies
• Definition – – Amount of Energy– Type of Energy
• Non-thermal• Polarized
• Other characteristics– Emission spectra
• Hydrogen – Balmer series & Lyman alpha (121.6 nm), UV• N V (124.0 nm)• C IV (154.9 nm)• O VI (103.5 nm)• Forbidden emission lines
• Synchrotron radiation
F()=Fo
between 0.7 and 1.2
Active galaxy general characteristics -– L>1037 W (>10 billion L)
– Non-thermal emission– Excessive amount of IR, UV, radio, x-ray– Small region of rapid variability– Bright nucleus– Explosive appearance/Jets– Broad emission lines
ULIRG
• Very high redshift (z)
• Very young/early galaxies
• Lots of IR/dust
• Lots of star formation
• Earliest of all galaxies?
Seyferts
• Characteristics– Bright nuclei, 100 billion L
– Spiral like (90%)• 10% Normal spirals have Seyfert characteristics
– Non-thermal, synchrotron continuum– Two different types
• Type I– More common
– Wide spectral features – high velocity
– More luminous
– UV, x-ray
• Type 2– Narrow emission lines– Strong in IR
• Range of types, 1.5, 1.7, etc.
Model?– Accretion disk (non-thermal)
• High energy photons (x-ray, uv)
– Black hole– Jets
• Radio, or boosted to higher energies
– Dust – IR source for type 2– High/low velocity clouds
Type 1
Type 1.5
Type 2
Radio Galaxies
• 1% of all galaxies
• 10% of active
• Level of emission is used to classify
• Two groups– Compact– Extended
• Jets – synchrotron, bipolar outflow• Lobes, 50-3000 kpc, electrons, protons
• 3 types of extended radio galaxies– Classical double lobes
• High luminosity• cD galaxies, ellipticals
– Wide-angle tails, bent tails– Narrow tail sources
• Low luminosity, high velocity galaxies
• Compact sources have different energy profile ( ~ 0)
Cygnus A
Radio, x-ray images
100 kpc
M87
3 billion M
Black hole
M87X-ray radio both
Quasars
• Quasi-stellar objects (QSOs)• Characteristics
– Star-like appearance– Broad emission lines– Absorption lines, especially if z>2– Other absorption features
• Broad features with velocities up to 0.2 c• Low velocity sharp lines – absorption/emission• Lyman – alpha forest – wide range of velocities
• Most quasars visible light sources, or higher energy (x-ray, gamma-ray)
• Non-thermal spectrum (a between 0, 1.6)• Variable – quick• High z values
– Quasar evolution– Brightness varies with z (brighter at high z)– Very few at very high z– Peak at z~2.5 (1000x more/volume than
today)– Peak of 1 QSO per 100 Mpc3
Unified Model
• Look at model for Seyferts – Can be applied to all types of active galaxies– Must have a black hole!
– Million – billions of M
– Infall rates of 100 M /year needed
– High luminosities – short lived
History?
Step 1. First objects formed – what were they?ULIRG or Quasars or regular Galaxies?ULIRG Rare, hard to findQSOs – stand out, but not common at very high zMost distant object observed, z=10 (maybe)
Step 1a. Formation of first galaxies, z=5-8?With massive black holes? First QSOs formed also (not all galaxies are QSOs)
Step 2. Peak of QSO formation at z=2.5
Step 3. QSOs start to fade
Not feeding them enough
Step 4. QSOs become Seyferts? Or Radio?
Less powerful, logical step
Seyfert phase – relatively short
Whole AGN phase – few billion years?
Step 5. Normal, boring galaxies, with no major activity
Feeding the Monster
Black hole powers AGNs
Can you over feed a black hole?
Yes!
Radiation pressure limits infall
Eddington Luminosity –
LEdd = 3 x 104 (MBH/M) L
Abell 1835 IR1916 z=10!Much smaller than MW!
Most distant object?
Most distant QSO
SDSS J1148+5251z=6.42
Gravitational Lensing
How many quasars?
Lynx arc