Post on 22-Dec-2015
8th EVN Symposium 2006Exploring the Universe with the real-time VLBI
Toruń, Poland, 26-29 September 2006
Carlo Stanghellini
Istituto di Radioastronomia INAF Bologna
CSS AND GPS RADIO SOURCES
CSS AND GPS RADIO SOURCES
The onset of radio activity in AGNThe onset of radio activity in AGN
• Extended extragalactic radio sources have ages of several million years.
• They form at the center of active galaxies and expand for up to a few Mpc outside the host galaxies.
• To understand why and how a radio source starts and develops we need to find the youngest thus (intrinsecally) smallest radio sources at the center of active galaxies.
• Extended extragalactic radio sources have ages of several million years.
• They form at the center of active galaxies and expand for up to a few Mpc outside the host galaxies.
• To understand why and how a radio source starts and develops we need to find the youngest thus (intrinsecally) smallest radio sources at the center of active galaxies.
find young radio sourcesfind young radio sources
These sources are known as Compact Symmetric Objects (CSO, < 1kpc) and Medium Size Objects (MSO, 1-20 kpc). They generally have a convex radio spectrum (flux density versus frequency).
These sources are known as Compact Symmetric Objects (CSO, < 1kpc) and Medium Size Objects (MSO, 1-20 kpc). They generally have a convex radio spectrum (flux density versus frequency).
To find young radio sources we may look for compact sources with the same morphology of the large ones (in the assumption they maintain their basic structure during their lifetime).
To find young radio sources we may look for compact sources with the same morphology of the large ones (in the assumption they maintain their basic structure during their lifetime).
CSO/MSO and GPS/CSSCSO/MSO and GPS/CSS selection of CSOs and MSOs has severe problems. They have in general a convex radio spectrum peaking
around 1 GHz (CSO) or 100 MHz (MSO).
Selection based on the spectral shape is easier. then Compact Steep Spectrum (CSS) and GHz Peaked
Spectrum (GPS) radio sources.
selection of CSOs and MSOs has severe problems. They have in general a convex radio spectrum peaking
around 1 GHz (CSO) or 100 MHz (MSO).
Selection based on the spectral shape is easier. then Compact Steep Spectrum (CSS) and GHz Peaked
Spectrum (GPS) radio sources.
5/15/2max
5/45/1max )z1(SH)(e
O'Dea 1998
GPS
CSS
TurnoverTurnover
CSS/GPS/HFP radio sourcesCSS/GPS/HFP radio sources
Are these objects really young?Are these objects really young?
Youth scenario – they are young (10^4 yr).
Frustration scenario – they are old (10^6 yr) and confined.
Recurrency – they die and start again.
Short lived – they die when still young.
Youth scenario – they are young (10^4 yr).
Frustration scenario – they are old (10^6 yr) and confined.
Recurrency – they die and start again.
Short lived – they die when still young.
The density in the inner kpc
From X-ray, infrared, HI at 21 cm, radio spectrum at low frequency, optical line diagnostic
There is not a conclusive evidence to distinguish between the youth and the frustration scenarios
Core
Hot-Spot
Hot-Spot
Evidence for youthOwsianik et al. 1998
Evidence for youthOwsianik et al. 1998
2352+495
0710+439 Owsianik et al. 1998
0710+439 Owsianik et al. 1998
OQ208
Polatidis and Conway 2003
Proper motionsProper motions
Polatidis, Conway 2003 --- 10 detections (0.1-0.3 c)
3 upper limits (<0.1c)
Gugliucci et al. 2005 --- 9 detections (0.4c ?), 8 upper limits (<0.2c)
Dynamical ages 100-10000 years
Polatidis, Conway 2003 --- 10 detections (0.1-0.3 c)
3 upper limits (<0.1c)
Gugliucci et al. 2005 --- 9 detections (0.4c ?), 8 upper limits (<0.2c)
Dynamical ages 100-10000 years
B1943+546B1943+546
100pc
Core
Jet
Lobe
Core
Determination of LOCAL spectral aging:assuming:- no reacceleration- equipartition magnetic field- no expansion losses
Determination of LOCAL spectral aging:assuming:- no reacceleration- equipartition magnetic field- no expansion losses
Need pc-scale spectral index images via Multifrequency VLBA+Y1 observation
Need pc-scale spectral index images via Multifrequency VLBA+Y1 observation
Hot Spots
50pcAge=~1300 yr
V_sep=0.28c
Age=~1300 yr
V_sep=0.28c
1323+3211323+321
Dynamical ages and radiative ages agree
and strongly favour the youth scenario
but
Extended emissionpresent in a fraction of GPS
VLA B array
Recurrency?
Not always
1127+1451127+145
1127+145 from mas to arcsec1127+145 from mas to arcsec
2.7 GHZ VLBA (RRFID)2.7 GHZ VLBA (RRFID)
8.4 GHZ VLBA (RRFID)8.4 GHZ VLBA (RRFID)
2.7 GHZ VLBA tapered2.7 GHZ VLBA tapered
1.4 GHZ VLA B1.4 GHZ VLA B
0738+3130738+313
0738+313 from mas to arcsec 0738+313 from mas to arcsec
15 GHz VLBA
15 GHz VLBA
15 GHzVLBA
15 GHzVLBA
1.4 GHzVLA B
1.4 GHzVLA B
5 GHzVLBI
5 GHzVLBI
What are the hosts of CSS/GPS?What are the hosts of CSS/GPS?
CSS/GPS/(HFP) are a mix of galaxies and quasars.
Quasars rarely show a symmetric morphology, mostly core-jet at mas resolution.
Presence of weak extended emission (>10kpc) when deep observations are available.
CSS/GPS/(HFP) are a mix of galaxies and quasars.
Quasars rarely show a symmetric morphology, mostly core-jet at mas resolution.
Presence of weak extended emission (>10kpc) when deep observations are available.
Fraction of core-jet quasarsFraction of core-jet quasars
Incidence of quasars and/or core-jet morphologies decreases with increasing size (and decreasing turnover frequency).
Consistent with the view that the convex radio spectrum in quasars and galaxies originate from intrinsically different emitting regions.
Incidence of quasars and/or core-jet morphologies decreases with increasing size (and decreasing turnover frequency).
Consistent with the view that the convex radio spectrum in quasars and galaxies originate from intrinsically different emitting regions.
CSS Some (Dallacasa et al., Fanti et al.)
GPS Half (Stanghellini et al.)
HFP Most (Dallacasa et al., Tinti et al. 2004)
CSS/GPS/HFP quasarsCSS/GPS/HFP quasars
In the framework of evolution of radio sources from pc to Mpc scale, most GPS quasars are contaminating objects.
Any inference based on complete samples of HFP/GPS/CSS radio sources should take in consideration this contamination, and should be limited to CSOs when information morphologies are available or limited to Galaxies, if mas morphologies are unknown.
In the framework of evolution of radio sources from pc to Mpc scale, most GPS quasars are contaminating objects.
Any inference based on complete samples of HFP/GPS/CSS radio sources should take in consideration this contamination, and should be limited to CSOs when information morphologies are available or limited to Galaxies, if mas morphologies are unknown.
Even excluding contaminating objects CSS/GPS/HFP are too many.
They should decrease in luminosity by an order of magnitude during evolution (Fanti et. al 1995, Odea et al. 1997)
Existance many short-lived objects (Readhead et al. 1994)
Even excluding contaminating objects CSS/GPS/HFP are too many.
They should decrease in luminosity by an order of magnitude during evolution (Fanti et. al 1995, Odea et al. 1997)
Existance many short-lived objects (Readhead et al. 1994)
Cotton et al. 2003
HFP/GSP/CSS sources become a “tool” to study the evolution of the extragalactic radio sources.
HFP/GSP/CSS sources become a “tool” to study the evolution of the extragalactic radio sources.
CSS/GPS/HFP samplesCSS/GPS/HFP samples
Spencer et al. 89
CSS 3C/PW Fanti et al. (1990) Kunert et al. 2002
B3-VLA Fanti et al. 2001
Compact Low Pol - Stanghellini et al. half Jy Parkes – Snellen et al. 2002
Marecki et al 1999 WENSS-GPS Snellen et al. 1998
GPS 1Jy Stanghellini et al. 1998
CORALZ – Snellen et al. 2004
HFP Bright HFP Dallacasa et al 2000 Faint HFP Stanghellini/Dallacasa
Flux density limit
size
Begelman 1996
Self-similar hypothesis: cocoon will evolve with a fixed ratio of
width to length Density profile
Luminosity into FRI, FRII
Expansion velocity weakly dependent on source size
A fraction of sources die young
nr
2
1
cs lL
Alexander 2000Atmosphere with a King profile
Self similar expansion
No cosmological evolution of the Luminosity Function
Comparison of predicted distribution functions with observational data - Samples: Stanghellini et al. 1998 (GPS) and Fanti et al. 1990 (CSS)
Luminosity increases in the GPS phase (<1kpc)
Luminosity decreases afterwards
GPS/CSS become FRII and FR I
A fraction are short lived sources
Snellen et al. 2000Samples: Snellen et al. 1998 (GPS), Stanghellini et al. 1998 (GPS),
Fanti et al. 1990 (CSS) – only galaxies
Luminosity evolution
derived Local Luminosity Function of CSS/GPS
Atmosphere with King profile
Equipartition conditions, self similar expansion
L increases in the GPS phase, then decreases,
CSS/GPS become FRII and FR I
strong comological evolution of the LF.
NO need for short lived objects
Tinti & De Zotti 2006
They combine several samples of GPS galaxies: Dallacasa et al. 2000, Stanghellini et al. 1998, WENSS Snellen et al.1998, Half-Jy Snellen et al. 2002, CORALZ Snellen et al. 2004, Edwards and Tingay 2004, Bolton et al. 2004 (111 objects)
NO self similarity
L decreases with time
GPS become only FRI
NO need for cosmological evolution of LF
The different models are constrained by the available samples of CSS/GPS/HFP radio sources
The problem of different predictions/results arises because the different groups introduce different assumptions to put the samples together
The different models are constrained by the available samples of CSS/GPS/HFP radio sources
The problem of different predictions/results arises because the different groups introduce different assumptions to put the samples together
what is needed?what is needed?
Selection and characterization of a large sample of HFP/GPS/CSS radio sources with symmetric morphology, at a low flux density limit, and a wide range in turnover frequency, to test and discriminate the proposed models.
Detection of proper motions in a large sample of HFP/GPS/CSS to investigate trends, make some statistics, and constrain the models
Selection and characterization of a large sample of HFP/GPS/CSS radio sources with symmetric morphology, at a low flux density limit, and a wide range in turnover frequency, to test and discriminate the proposed models.
Detection of proper motions in a large sample of HFP/GPS/CSS to investigate trends, make some statistics, and constrain the models
New instruments are important to go to weaker flux densities and higher resolutions but a lot can be done with just the EVN, VLBA, VLA
New instruments are important to go to weaker flux densities and higher resolutions but a lot can be done with just the EVN, VLBA, VLA