8th EVN Symposium 2006 Exploring the Universe with the real-time VLBI Toruń, Poland, September 2006 Carlo Stanghellini Istituto di Radioastronomia INAF Bologna CSS AND GPS RADIO SOURCES

The 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 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). 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/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.

O'Dea 1998 GPS CSS

Turnover CSS/GPS/HFP radio sources

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 Evidence for youth Owsianik et al Evidence for youth Owsianik et al

Owsianik et al. 1998

OQ208

Polatidis and Conway 2003

Proper motions Polatidis, Conway detections ( c) 3 upper limits (<0.1c) Gugliucci et al detections (0.4c ?), 8 upper limits (<0.2c) Dynamical ages years Polatidis, Conway detections ( c) 3 upper limits (<0.1c) Gugliucci et al detections (0.4c ?), 8 upper limits (<0.2c) Dynamical ages years

B pc 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 Hot Spots 50pc Age=~1300 yr V_sep=0.28c Age=~1300 yr V_sep=0.28c

Young Radio Sources

Dynamical ages and radiative ages agree and strongly favour the youth scenario but

Extended emission present in a fraction of GPS Recurrency? Not always

GHZ VLBA (RRFID)8.4 GHZ VLBA (RRFID)2.7 GHZ VLBA tapered 1.4 GHZ VLA B

 from mas to arcsec 15 GHz VLBA 15 GHz VLBA 1.4 GHz VLA B 5 GHz VLBI

z=0.631 z=2 z=3

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.

Flux density limits

Fraction 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)

Origin of the convex spectrum  In CSOs few similar rather homogeneous compact components (lobes and/or hot-spots) combine to make the typical global GHz peaked radio spectrum.  In some quasars a particular geometric configuration amplifies the brightness of a compact and homogeneous component close to the core, which dominates the radio spectrum and is responsible for the global GHz peaked shape.  In CSOs few similar rather homogeneous compact components (lobes and/or hot-spots) combine to make the typical global GHz peaked radio spectrum.  In some quasars a particular geometric configuration amplifies the brightness of a compact and homogeneous component close to the core, which dominates the radio spectrum and is responsible for the global GHz peaked shape.

 GPS galaxies are young radio sources (or confined).  GPS quasars are intrinsically similar to FS quasars.  In the framework of the study of the evolution of extragalactic radio sources, CSS/GPS/HFP quasars are objects contaminating the samples, and should be excluded.  GPS galaxies are young radio sources (or confined).  GPS quasars are intrinsically similar to FS quasars.  In the framework of the study of the evolution of extragalactic radio sources, CSS/GPS/HFP quasars are objects contaminating the samples, and should be excluded. Quasars and Galaxies are different objects

CSS/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.

CSS/GPS/HFP samples Spencer et al. 89 CSS 3C/PW Fanti et al. (1990) Kunert et al B3-VLA Fanti et al Compact Low Pol - Stanghellini et al. half Jy Parkes – Snellen et al Marecki et al 1999 WENSS-GPS Snellen et al GPS 1Jy Stanghellini et al CORALZ – Snellen et al HFP Bright HFP Dallacasa et al 2000 Faint HFP Stanghellini/Dallacasa Flux density limit size

Evolution of extragalactic radiosources Expansion, interaction with the ambient medium, luminosity evolution, age-size correlation:  current models on the evolution of the radio sources in their infancy derive by the model of Begelman,  self similarity, luminosity decreases with time. Expansion, interaction with the ambient medium, luminosity evolution, age-size correlation:  current models on the evolution of the radio sources in their infancy derive by the model of Begelman,  self similarity, luminosity decreases with time.

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

Alexander 2000 Atmosphere 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 (GPS) and Fanti et al (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 Samples: Snellen et al (GPS), Stanghellini et al (GPS), Fanti et al (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 (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?  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