What are Active Galaxies?

1
What are Active Galaxies?
Active galaxies have an energy source beyond what
can be attributed to stars. The energy is
believed to originate from accretion onto a
supermassive blackhole. Active galaxies tend to
have higher overall luminosities and very
different spectra than normal galaxies.

• Some classes of active galaxies
• Quasars
• Seyfert galaxies (Type I and Type
  II)
• Radio galaxies
• LINERs

non-stellar radiation
stellar, blackbody radiation
2
AGN radio loud classification Radio galaxies
Giant E similar to radio quiet E with non thermal
activity origin core (possibly X
optical) Extended kpc scale FR I and FR II
FR II BLRG and NLRG
FR I only NLRG Compact Low Power Compact
CSS CSO GPS nuclear only Intrinsic
(young or frustrated) geometry effects Radio
power 1040 -- 1047 erg/s
1 erg 0.1µJy 1 Jy 10-26 W/Hz m2
3
Radio galaxies of high and low power have quite
different morphologies on the large scale
(Fanaroff Riley 1974)
FR II High power P1.4 GHz gt 1024.5 W Hz-1
CLASSICAL DOUBLES
EDGE BRIGHTNED Radio core, asymmetric
collimated jets, hot-spots
Cyg A
3C 109
3C 219
4
FR I Low power P1.4 GHz lt 1024.5 W Hz-1
EDGE DARKENED Radio core, symmetric jets with
opening angles ? 10-15o,
low brightness lobe
3C 296
3C 449
3C 31
5
Quasars

• First discovered in the 1960s.
• Detected radio sources with optical counterparts
  appearing as unresolved point sources.
• Unfamiliar optical emission lines.
• Maartin Schmidt was the first to recognize that
  these lines were normal Hydrogen lines seen at
  much higher redshifts than any previously
  observed galaxies.
• D 660 Mpc (2.2 billion light years) for
  3C273
• 1340 Mpc (4.4 billion light
  years) for 3C 48
• L 2 x 1013 Lsun for 3C273.
• Within 2 years, quasars were discovered with
  z gt 2 and L ? 1014 Lsun
• Most distant QSO discovered today - z 6.42

6
QUASAR
-- Starlike some time radio loud --
Variability (continuum) -- UV excess -- Broad
Lines -- High z -- X-Ray emission -- continuum
? non thermal (radio optical and X) radio quiet
similar to radio loud, Radio to optical
ratio radio at 5 GHz optical at 4400
Amstrong Rr-o 10--100 radio loud
0.1--1 radio quiet
7
3C 48
8
3C 273
9
HST image 3C273
10
(No Transcript)
11
Very Long Baseline Interferometry VLBI
EVN
V L B A
Spatial VLBI
12
114435
13
Angular resolution R 1.22 lambda/D radiant
eye D 8 mm R 17.3 but because of cell size
1 Optical telescope 4 m 0.035 but seeing
problems. Radio no problem with atmosphere up
to 22 GHz and more ? R better than 1 mas
14
Linear scales SMBH
AU Accretion Disk
1 mpc Compact radio
VLBI core 0.1 pc BLR

1 pc Molecular Thorus
100 pc NLR
up to kpc Host Galaxy
a few
kpc Radio Lobes
1 Mpc
15
VLBI studies of radio galaxy nuclei one of the
most important results is the detection of
proper superluminal motion
Expansion of about 6 pc in 3.5 years ?
velocity ? 6c
16
By the time that light leaves from position (2),
light emitted from position (1) will
have travelled a distance AC The difference in
arrival time for the observer is
SUPERLUMINAL MOTION
The apparent velocity as seen by the observer is
For example ? 10o and v 0.999c
then v(OBS) 10.7 c
17

• The detection of superluminal motions and
• of one-sided jets in the majority of both
• low power and high power radio galaxies
• indicates that the jets at their basis are
• all strongly relativistic

18

• Doppler effect and relativistic boosting
• v ßc ? orientation angle with respect to
  the line of sight
• ? ?o ?e/(?(1-ßcos?o)) ?e D
• is the Lorentz factor and
• D 1/(?(1-ßcos?o)) Doppler factor
• Low velocity ? 1 D ? (1 ß cos?o) classic
  Doppler
• Le total source luminosity
• monocromatic source luminosity L(?e)
• Power emitted in ??e will be received in
• ??o ??e D

19
The power is for frequency unit ?o ?e x D
for time unit dto dte? - dte ? ß cos?
dte?(1 ß cos?) dte/D in the time range
between the emission of 2 photons the source
moved in our direction (or time
contraction) for solid angle d?o d?e/D2
Relativistic aberration and d?o p d?o2
20
in conclusion Lo Le x D4 Doppler boosting or
relativistic beaming But if we consider
monochromatic emission Lo(?o)d?o Le(?e)d?e x
D4 Lo(?o) Le(?e) x D3 Since L(?) ? ?-?
(synchrotron) Lo(?o) Le(?o) x D3? Le(?o) x
D4 D-(1-?) D-(1-?) is the K-correction
21
JET RELATIVISTIC EFFECTS
(DOPPLER BOOSTING)
Doppler factor
Jet pointing toward the observer is AMPLIFIED
22
From the ratio between the approaching and the
receding jet, the jet velocity and orientation
can be constrained
JET SIDEDNESS RATIO
But if jets are a continuum emission, only the
structure in the motion direction is affected
(unidimensional motion)
23
FR I - 3C 449
FR II - 3C 47
24
Radio core dominance
Given the existence of a general correlation
between the core and total radio power we can
derive the expected intrinsic core radio power
from the unboosted total radio power at
low frequency.
Pc observed core radio power at 5 GHz Ptot
observed total radio power at 408 MHz Core radio
power affected by jet Doppler boosting Total
radio power at low frequency is intrinsic, no
boosting because core self absorbed and radio
lobes steep spectrum
25
The comparison of the expected intrinsic and
observed core radio power will constrain ß and
?. A large dispersion of the core radio power is
expected because of the dependance of the
observed core radio power with ?. From the data
dispersion we derive that ? has to be lt 10
26
Pc Pi D(2 ?) Pbest-fit P(60) Pi D(2 ?)
Pi/?2?(1-ß cos?)2? if ? 60 we have

Pi/?2?(1-ß/2)2? and Pi P(60)
?2?(1-ß/2)2? Pc P(60) (1-ß/2)2? / (1-ß
cos?)2? Assuming ? 0 (nucleo) Pc P(60)
(1-ß/2)2 / (1-ß cos?)2 (Pc/P(60))0.5 (1-ß/2)/
(1-ß cos?) Pc from observations
P(60)
from Ptot and best fit High jet velocity implies
a high dispersion of observational points
27
Arm length ratio
By comparison of the size of the approaching (La)
and receding (Lr) jet we derive
Or La/Lr La/Lr ?a/?r Da/Dr
28
Brightness Temperature I? F?/p?2 B?
2kTb/?2 F? observed monocromatic flux ?
source angular size. Values are in the range T
1011 1012 K ? non thermal origin Tb has to
be lt 1012 K since at this value the magnetic
field energy density (Umag B2/8p) can be
lower than the radiation energy Urad
4pJ/c When Urad gt Umag the dominant emission is
from inverse Compton in the gamma ray band and
the source life is very short. Moreover we do not
see the expected emission in the gamma band
29
Therefore we derive that Urad/Umag lt 1
corresponding to Tmax 1012 K or lower But
from short (intraday variability) we have Tb(?)
? (S(?)/?2) (?2/2k) ? S(?) ?2 small ? and/or
large ? Tb(?) gt 1012 K Solutions 1) Coherent
synchrotron emission 2) Relativistic motion
Tbi Tbo x D 3) Stellar scintillation
30
THE MEASUREMENT OF THE JET VELOCITY
Proper Motion In some sources proper motion has
been detected allowing a direct measure of the
jet apparent pattern velocity. The observed
distribution of the apparent velocity shows
a large range (e.g. Kellerman et al. 2000)
31
From the measure of the apparent velocity we can
derive constraints on ß and ? But are bulk
and pattern velocity correlated???? In a few
cases where proper motion is well defined there
is a general agreement between the highest
pattern velocity and the bulk velocity Ghisellin
i et al. 1993 Cotton et al. 1999 for NGC
315 Giovannini et al. 1999 for 114435 However
in the same source we can have different
pattern velocities as well as standing and high
velocity moving structures
32
(No Transcript)
33
(No Transcript)
34
The correlation between the optical and radio
nuclear flux density in FR I implies common
synchrotron origin and no dust torus BL Lacs
show the same correlation in agreement with
Unified Models. The shift is due to the different
boosting
BL Lacs
Chiaberge et al. 1999
FR I
35
BL Lacs
Chiaberge et al. 1999
FR I
Our sample
Corrected for the Doppler factor
BL Lacs observed
36
Parent Population
intrinsic
observed
Low frequency ? no beaming effects
Nuclear properties different since are
affected by beaming but in agreement if we
compare intrinsic values.
37
Velocity Structures
An evident limb brightened jet morphology on the
parsec scale is present in some FR I
sources 114435, Mkn 501, 3C 264, M87,
033139.
38
But also a few high power sources show the same
structure
BLAZAR 1055018
The limb-brightened structure can be due to a
different Doppler boosting in a two-velocity
relativistic jet. If the source is oriented at a
relatively large angle with respect to the line
of of sight, the inner high velocity spine
could be strongly deboosted while the slower
external layer could be boosted or at least not
so strongly de-boosted
39
The low number of known limb-brightened sources
is due -- to observational problems to
transversally resolve the jet -- to orientation
effects only sources in a small orientation
range can appear as limb-brightened because of
the different Doppler factor.
Profile of the 3C 264 jet at different distances
from the core
BL_Lac 0521-165
40
Is the two velocity regime ? related to the jet
interaction with the ISM ? or an intrinsic jet
property ?
in most sources the limb-brightened structure
starts far from the core ? external (real or
angular resolution effect?)
in M87 the jet is limb-brightened on scales of
light-weeks ? intrinsic in Mkn 501 the jet
is resolved very near to the core ? intrinsic in
114435 we need a too fast velocity decrease ?
intrinsic
41
Moreover recent observations of Cygnus A (Bach et
al. 2003) show a complex structure of the jet and
cj, an apparent jet acceleration and a low
velocity proper motion. The observations could
be explained by a stratification of the jet with
different velocities. Meier (2003) discussed a
model where a different velocity regime is an
intrinsic jet property related to the inner AGN
structure. In this case one more jet velocity
decrease due to the ISM is likely to be present
in an intermediate region (from the pc to the
kpc).
42
Two laboratory sources 114435 and Mkn 501
114435 is a giant radio galaxy projected linear
size 1.0 Mpc h65-1
The arcsecond core is the dominant feature
43
On the parsec scale it shows a core, a strong
extended jet and a short cj
counterjet
flat spectrum core
main jet
44
Superluminal motion
Well defined components 11 epochs from 1991 to
2002
Only high quality data jet 5 and 8.4 GHz
data cj 8.4 GHz only Jet ßapp 2.7
constant All components constant velocity cj
side ßapp 0.3
45
Since we know the j and cj proper motion
according to Mirabel et al. 1994 we can derive
the jet orientation
Assuming H0
65, the source distance D is 295 Mpc and
? 25o
Therefore ß 0.88 is the pattern velocity of
the shear layer. The Doppler factor is 2.4 the
structure is boosted.
From the j-cj brightness ratio and from the
j-cj arm ratio we derive a jet bulk velocity ß
gt 0.8 in agreement with the measured pattern
velocity.
46
Shear-layer d 2.4 - boosted If the inner
spine is moving with e.g. ? 15 the
corresponding Doppler factor is 0.7
deboosted. A fast spine and a lower velocity
shear layer can explain the limb brightened
structure.
core
If the external region started with the same
velocity of the inner spine, its velocity
decreased from 0.998 to 0.88c in less than 100
pc. This suggest a velocity structure already
present at the jet beginning.
47
z 0.034 1mas 0.67 pc
Tavecchio et al. 2001
From NED
48
Mkn 501 Large Scale
Koolgaard et al. 1992

• VLA

Symmetric structure Jets are no more
relativistics on 10 kpc scale
20 kpc
49
At 2 arcsecond ?ß cos? gt 0.36 At 1 arcsecond ?ß
cos? gt 0.63
VLA B array (Cassaro et al. 1999)
VLA A array at 1.4 GHz
1.5 kpc
1.5 kpc
50
At 100 mas ß cos? gt 0.61 At 50 mas ß cos? gt
0.77
HPBW 9x5 mas
35 pc
51
The jet shows a complex and continuous morphology
with many sharp bends before undergoing a last
turn in the PA of the kpc scale structure. The
jet is clearly limb brightened. At 10 mas ß
cos? gt 0.92
15 pc
52
Evident limb-brightened structure beginning very
near to the core and visible up to 100 mas from
it. It is interpreted as evidence of a velocity
structure. No proper motion has been found
comparing 9 different epochs from 1995.29 to
1999.55. Compact structures are resolved and
complex in high resolution images
10 pc
22 GHz
22 GHz
1.5 pc
1.6 GHz VSOP
3 pc
53
A radio core one sided jet is visible in
recent VLBI observations at 86.2 GHz with a
linear resolution of 0.08 x 0.13 pc (HPBW)
Giroletti et al. in prep.
0.2 pc
Thanks to the global mm VLBI network VLBA (7
telescopes), Eb, Plateau de Bure, Pico Veleta,
Onsala, Metsahovi
54
Core unresolved at 86 GHz ? size lower than
0.03 pc (gaussian fit) 1 Rs 0.001 pc (M 109
Mo) High frequency spectrum is steep with a
turnover at about 8.4 GHz. It implies a magnetic
field in the range 0.01 0.03 G and that
inside the core a structure is present
Question why the jet brightness is so low
in the 86 GHz image? Steepening because of
high magnetic field?
We do not have polarization information Gabuzda
et al. 2004 B fields are dominated by the
toroidal component.
55
Better images to find the core position measure
the jet dynamics (starting velocity and
acceleration velocity structure)
M87 at 86 GHz (Krichbaum et al. 2006) at 43
GHz (VLBA) (Ly et al. 2007) MKN501 at 86 GHz
0.08 pc
56
Jet velocity and orientation from data High
velocity jet with G 15 and ? 4o (d ? 15) in
the gamma-ray region (lt 0.02 mas lt 0.02 pc)
from high frequency emission, gamma-ray
variability, and SED (SSC models) In the radio
jet region the jet orientation move from 4o to
10o - 15o to explain the limb-brightened
structure radio structure and G decrease to 10 (d
? 2.6) at 30 - 40 mas from the core (80-120
pc) The jet velocity decrease is low from HSA
data we estimate relativistic jets (v gt 0.6 c at
1 from the core) At 5 (?10 kpc de-projected)
the jet is no more relativistic (G 1.02 v
0.2c) as expected from FR I jet velocities Jet
PA not constant for unknown reasons
57
Observational data are in agreement with a simple
adiabatic model if the magnetic field is mostly
perpendicular to the jet (a parallel field
predicts a too fast velocity decrease with
respect to the j cj ratio)
Jet initial velocity 0.998 c
25 20 15
10
5
Adiabatic model in the case of relativistic
motion discussed by Baum et al. 1997. See
also Cotton et al. 1999, and Giroletti et al. 2004
58
Nuclear Structure Self absorbed regions Tb in
the same range of relativistic electrons Kinetic
temeperature Self absorbed spectrum ?2.5,
Trasparent region ?-? H(gauss) 3.2
10-5(?(mas))4(?max(GHz))5(Smax(Jy))-2 D/(1z) D
Doppler factor
59
From accretion/inflows to ejection/outflows
From IN to OUTflows
OUT
OUT
IN
IN
Magnetic Tower by Kato et al. 2003 (see also
Lynden-Bell 2003)
60
Le regioni piu interne dellAGNil modello base
e i meccanismi di emissione
RgGM/c2raggio gravitazionale
MBH106-109 masse solari
Compton inverso
Continuo di riflessione Compton
Emissione termica
Hot electrons T108-9 K
102 rg
Accretion disk T106 K
Black hole
T108-109 K
104 rg
61
CSO and GPS

• Good samples of CSOs selected on the morphology
  only are difficult to obtain
• CSO have in general a convex radio spectrum
  peaking around 1 GHz
• Selection based on the spectral shape is easier
• Lets look for GHz Peaked Sources (GPS)

D doppler factor circa 1!
62
Turnover frequency versus linear size
63
CSS/GPS/HFP radio sources
Turnover
64
(No Transcript)
65
Young Frustrated Geometric reasons
66
2352495
Owsianik et al. 1998
Hot-Spot
Core
Hot-Spot
67
0710439

• Owsianik et al. 1998

68
OQ208

69

• From Polatidis 2002

70
ENSEMBLE OF ELECTRONS
Synchrotron emissivity
Spectral index

• AGEING
• only e- with
• E lt E survive
• spectral break
• proportional to
• the source age
• ? ? H-3 t -2

Original spectrum
Aged spectrum
71
B1943546
Determination of LOCAL spectral
aging assuming - no reacceleration -
equipartition magnetic field - no expansion
losses
Hot Spots
Lobe
Age1300 yr V_sep0.28c
Core
Core
50pc
100pc
Need pc-scale spectral index images via
Multifrequency VLBAY1 observation
Jet
72
Young Radio Sources
73
Young Radio Sources
74
High Frequency Peakers

• Framework of YOUTH scenario

(Fanti et al. 1995, Readhead et al. 1996, Snellen
et al. 2000)
supported by

• Lack of any evidence for frustration
• Hot - spots motion in about a dozen of CSOs
• Spectral ageing in CSS/GPS radio sources
• Radio power .vs. Linear size (with
  ''irregularities'')

(many)
Owsianik Conway(1998), Fanti (2000), ...
Murgia et al. (1999)
75
VLBA _at_ 5 GHz, epoch July 2000 (10 mas 15 pc)
76
Expansion... results.

• DE 0.4 mas
• DW 0.5 mas
• DT 5 yr

• v 0.5 c
• age 500 yr

77
The early stages of radio source evolution
Tadhunter et al. 2001
PKS1549-79 AAT/IRIS2 K-band
FWHM1740/-50 km/s
78
CSS decrease in luminosity by an order of
magnitude during their evolution (e.g. Fanti et
al. 1995)
Snellen et al. 2000
79
FR II
FR I
limite osserv. per giganti