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