Physical properties of young radio sources and their ambient medium Monica Orienti Dipartimento di Astronomia, UniBo; INAF – IRA, Bologna Monica Orienti Active Galactic Nuclei 9 Ferrara 27/05/2010 Collaboration with D. Dallacasa

Outline Monica Orienti Active Galactic Nuclei 9 Ferrara 27/05/ Young radio sources and their evolution 2. Physical properties in young radio sources 3. Young radio sources and their ambient medium

3 1. Young Radio Sources P 1.4 GHz > W/Hz; Convex spectrum; LS < 1 – 20 kpc; Double/triple or complex; Asymmetries; 15%-30% in flux limited samples 500 pc 350 pc 550 pc 175 pc Monica Orienti Active Galactic Nuclei 9 Ferrara 27/05/2010

Evolutionary scenario HFP GPS CSS 1. Young radio sources Kinematic ages Spectral ages CompactYoung yr Polatidis&Conway 03, Murgia+ 99, Murgia 03… High fraction in flux limited samples: luminosity evolution! Snellen+00 Monica Orienti Active Galactic Nuclei 9 Ferrara 27/05/2010

Dying objects? HFPGPS CSS ? FR I/II Orienti et al PKS Young radio sources t syn = 2700±600 years; γ ≤ 600; t OFF = 550±100 years No injection/acceleration of fresh particles! Monica Orienti Active Galactic Nuclei 9 Ferrara 27/05/2010

Recurrent activity? On kpc scales: (Baum et al. 1990; Tinti et al. 2005) On pc-scales: (Orienti&Dallacasa 2008, Luo et al. 2007) 1. Young radio sources t relic ~ 10 7 –10 8 yr J t relic ~ 10 3 – 10 4 yr J J : 128 kpc J : 50 pc OQ208: 43 pc OQ 208 Monica Orienti Active Galactic Nuclei 9 Ferrara 27/05/2010

The spectral peak Optically thin Optically thick     Radiative losses Log Log S( ) SSA is present by default SSA in a homogeneous component: β = Physical properties Monica Orienti Active Galactic Nuclei 9 Ferrara 27/05/2010

Magnetic field In the presence of SSA from homogeneous component: H SSA = f(  ) 5 S 2 p (1+z)   max   min 5 p Kellermann & Pauliny-Toth Physical properties Monica Orienti Active Galactic Nuclei 9 Ferrara 27/05/2010 Orienti & Dallacasa 2008

Are young objects in equipartition? In case of equipartition: H eq  (1+k) 2/7  -2/7 P 2/7 V -2/7 Pacholczyk 1970 H eq  H SSA Orienti&Dallacasa Physical properties Monica Orienti Active Galactic Nuclei 9 Ferrara 27/05/2010

Are young objects in equipartition? In case of equipartition: H eq  (1+k) 2/7  -2/7 P 2/7 V -2/7 Pacholczyk 1970 H eq  H SSA with some exceptions… Orienti&Dallacasa Physical properties Monica Orienti Active Galactic Nuclei 9 Ferrara 27/05/2010

SSA or FFA? SSA 2. Physical properties Not homogeneous ambient medium! FFA Orienti&Dallacasa 08 Monica Orienti Active Galactic Nuclei 9 Ferrara 27/05/2010

The HI in young radio sources Larger incidence of HI absorption in young radio sources than in “normal” radio galaxies (Morganti et al. 2001); Anti-correlation LS – N HI ; (Pihlström et al. 2003; Vermeulen et al. 2003; Gupta et al. 2006) Circumnuclear disk/tours (Mundell et al. 2003) 3. The ambient medium Monica Orienti Active Galactic Nuclei 9 Ferrara 27/05/2010

The HI in young radio sources Larger incidence of HI absorption in young radio sources than in “normal” radio galaxies (Morganti et al. 2001); Anti-correlation LS – N HI ; (Pihlström et al. 2003; Vermeulen et al. 2003; Gupta et al. 2006) Circumnuclear disk/tours (Mundell et al. 2003) 3. The ambient medium Monica Orienti Active Galactic Nuclei 9 Ferrara 27/05/2010

3. The ambient medium The X-ray column density Anti-correlation LS – N H :What’s the origin of the X-ray emission? Monica Orienti Active Galactic Nuclei 9 Ferrara 27/05/2010 Tengstrand et al J

3. The ambient medium The X-ray column density Radio outflow due to jet-cloud interaction Are we observing the same absorber??? Morganti et al Monica Orienti Active Galactic Nuclei 9 Ferrara 27/05/2010 OQ 208 Tengstrand et al. 2009

Distribution of the atomic hydrogen HI located ~100 pc from the core, where the jet bends Off-nuclear cloud 4C Morganti et al The ambient medium HI detected against the whole source Central disk , Peck et al Monica Orienti Active Galactic Nuclei 9 Ferrara 27/05/2010

Jet-cloud interactions? They may be responsible for the asymmetries in arm- length and luminosity found in compact objects The statistic is still too poor….. Labiano et al The ambient medium Monica Orienti Active Galactic Nuclei 9 Ferrara 27/05/2010

Asymmetries in “symmetric” objects Strong asymmetry in both luminosity and arm-length ratios between the lobes Saikia+ 03, Fanti+ 90 Jet-ISM interaction? 3. The ambient medium Orienti et al., in prep. Monica Orienti Active Galactic Nuclei 9 Ferrara 27/05/2010

19 Summary Monica Orienti Active Galactic Nuclei 9 Ferrara 27/05/2010 Small radio galaxies represent the young phase in the radio source evolution; Not all the young radio sources will evolve in the large FR I/FR II population; The spectral peak is due to SSA, but an additional contribution from FFA is present in the most compact objects; Young radio sources are in equipartition conditions; The ambient medium plays an important role in the evolution of the radio emission. A better knowledge of the ambient medium will enable us to draw a more reliable picture on the fate of the radio source evolution

Summary Small radio galaxies represent the young phase in the radio source evolution; Not all the young radio sources will evolve in the large FR I/FR II population; The spectral peak is due to SSA, but an additional contribution from FFA is present in the most compact objects; Young radio sources are in equipartition conditions; The ambient medium plays an important role in the evolution of the radio emission. More X-ray observations please!!! Monica Orienti Active Galactic Nuclei 9 Ferrara 27/05/2010