Gabriele Giovannini Dipartimento di Astronomia, Bologna University

Low Luminosity Radio Loud AGNs Gabriele Giovannini Dipartimento di Astronomia, Bologna University Istituto di Radioastronomia - INAF In collaboration with M. Giroletti – IRA INAF Bologna G.B. Taylor - UNM Albuquerque NM

OUTLINE Review: Morphology Kinematic New Results: Faint cores Complex morphologies A giant FR I source with apparent superluminal motion: 1144+35 Conclusions About: Polarization see Gabuzda BL Lac sources see Bondi Young sources see Stanghellini

Jet morphology Literature data + The complete sample: B2 and 3CR radio sources with z < 0.1 Being selected at low frequency it is not affected by observational biases related to orientation effects. Nearby sources: good linear resolution + low power At present VLBI data are available for 60/95 sources The large scale morphology of observed sources is 37 FR I rg 11 FR II rg 8 compact flat spectrum sources Other: 2 Bl_Lacs, 1 CSO, 1 CSS

Important result is that two-sided sources on the pc scale are 18 corresponding to 30.2% to be compared with 11% in PR sample and 4.6 % in Caltech survey. In a random oriented sample the probability that a source is at an angle between θ1 and θ2 with respect to the line of sight is P(θ1,θ2) = cos(θ1) – cos(θ2) the percentage of FR I + FR II is 48/60 = 80% corresponding to θ > 37o-40o in agreement with unified models. The percentage of two-sided sources is 30% corresponding to angles > 70o. Consistent with a j/cj ratio R ≤ 5 if jet velocity = 0.9 – 0.99c

All FR II two-sided are NLR. • Two-sided sources show low power radio cores. • In most sources there is a good agreement between the pc-kpc • scale jet orientation in agreement with the suggestion that • large distortions seen in BL-Lac sources are due to small • intrinsic bends amplified by projection effects

3C192 z = 0.0597 arcsecond core: 8 mJy at 5 GHz VLBI phase reference mode Peak: 1.7 mJy/b noise: 0.05 mJy/b VLA B+C at 1.4 GHz 10 pc LS 200 kpc

3C 452 a NL FR II radio galaxy 0331+39 a low power compact radio galaxy 3C 338 a FR I radio galaxy

3C 382 a BL FR II radio galaxy 3C 66B a FR I radio galaxy

JET KINEMATICS Proper Motion 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: Ghisellini et al. 1993 Cotton et al. 1999 for NGC 315 Giovannini et al. for 1144+35

However in the same source we can have different pattern velocities as well as standing and high velocity moving structures In some well studied sources the jets show a smooth and uniform surface brightness  no proper motion visible e.g. Mkn 501 (Giroletti et al. 2004) + poster Assuming that the jets are intrinsically symmetric we can use relativistic effects to constrain the jet bulk velocity βc and orientation with respect to the line of sight (θ) as following:

Jet sidedness From the jet to cj brightness ratio R we derive: 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. Arm length ratio By comparison of the size of the approaching (La) and receding (Lr) and more

B2 and 3Cr sources Rg and QSS No selection effect on θ The comparison of the expected intrinsic and observed core radio power will constrain β and θ. A large dispersion of the core radio power is expected because of the dependance of the observed core radio power with θ. From the data dispersion we derive that Г has to be < 10 and > 3

Results From our study on 60/95 sources from the B2 and 3CR catalogues and from literature data we found that: - In all sources pc scale jets move at high velocity. No correlation has been found with core or total radio power - We used the jet velocity and the corresponding orientation to derive the Doppler factor for each source: and the corresponding intrinsic core radio power:  = 0

M87 3C192 The line is the general correlation between the core and total radio power. Points in the left side (observed data) show the expected dispersion because of different orientation. Note that we started to observe sources with brighter core. In the right figure we plotted the derived intrinsic core radio power. We have here a small dispersion since we removed the spread due to different orientation angles.

Next step (in progress) sources with an arcsecond core flux density > 1 mJy Sources with a faint radio core: more complex structures -- restarted activity -- different orientation angle between pc and kpc structure -- complex pc scale structure with no evident core or multiple core? A statistical problem or we are starting to study sources with different properties?

4C 26.42 1346+26 central cD in A1795 z = 0.06326 VLBI 6 cm peak flux 5.9 mJy/b noise 0.1 mJy/b

10 pc VLBI 20 cm Phase ref. Mode Peak 24 mJy/b Noise 0.07 mJy/b 5 pc VLBI 6cm

3C 310 VLA B+C Linear size  300 kpc 1.4 GHz 1.7 GHz In agreement with Gizani and Garrett (2002) 6th EVN Symp. 5 GHz 5 pc Peak flux 1.3 mJy/b Noise 0.07 mJy/b

FIRST 25 kpc Van Breugel et al. 1986 VLA A+B at 20cm 0836+29B 4C29.30 A galaxy merger

Core – most compact only flat spectrum component 1 kpc VLA – A array at 6 cm

5 pc 1 kpc

Giant radio galaxy, core dominated at z = 0.0630 1144+35 counterjet flat spectrum core main jet

A1 B2 B1 B A

We started to observe this source with VLBI in 1990. The pc scale jet shows a well defined structure moving with a constant velocity and direction. We have an apparent jet velocity = 1.92c and a counter jet motion with an apparent velocity = 0.23c.

Assuming a symmetry in the jet/counter jet velocity, according to Mirabel and Rodriguez (1994) we can derive the intrinsic jet velocity and orientation: We derive: θ =30o and β = 0.95 These values are in agreement with the measured arm ratio: the jet/cj length ratio is 10  β cos(θ) = 0.82  β = 0.95 and θ = 30o.

The arcsecond core shows a clear flux density variability. Observations are available from 1972 at different frequencies. From a comparison of multi-epoch data it is clear that the flux density variability is not due to a core activity but to jet substructures (mainly the A component).

The morphology of this source suggests a recurrent radio activity. At least we have 1st (oldest): Mpc scale 2nd: naked jet + core dominant at arcsecond scale 3rd: VLBI Assuming a constant jet velocity, the main jet structure “came out” from the core in  1950. Fom 1950 to 1990 the flux density increased: velocity decrease in the external regions  Doppler factor increases ? Starting from 1990 we have an evident flux density decrease in the A component, which however appears always compact and moving at the same apparent velocity excluding possible adiabatic losses

In the last period 2002 to 2006: 1) The VLBI core is slightly increasing its flux density at 8.4 GHz In 2006 for the first time the VLBI core is the dominat mas structure 2) The arcsecond core flux density at frequencies > 8.4 GHz has stopped its flux density decrease. Since A component is still decreasing the change is due to the VLBI core Possible explanation: After 2002 and before 2006 the core is in an active phase and a new component is coming out. This new component is not yet visible in our images and is still self absorbed at frequencies lower than 8.4 GHz

We can estimate its size from the selfabsorption frequency assuming equipartition magnetic field: The estimated size of this new component is  0.03 mas not yet visible (VLBA HPBW is 0.17 mas at 7 mm) If it is moving with βa = 1.92 (as the main jet) we should start to resolve it in about 2 yrs (X band)

CONCLUSIONS • The parsec scale jet morphology is the same in high (FR II) and low (FR I) power sources • The pc scale morphology is in agreement with expectations from unified models • There is a good agreement between the pc and kpc scale orientation • The pc scale jet velocity is highly relativistic in FR II and FR I sources. It is not related to the total or core radio power of the source. No correlation with the kpc scale structure.

In some sources with a low power nuclear source we find a • peculiar morphology: restarted activity and a complex mas scale • structure not yet understood, misaligned with the kpc scale • structure • The low power source 1144+35 shows a superluminal motion and • a restarted activity. The core flux density is variable and an • increase of the core flux density at high frequency suggests • the presence of a new component which could be visible in • VLBI images in 2007-2008 • The monitor of the source 1144+35 allows the study of the pc • scale jet evolution starting from 1990 (mas morphology) • and from 1972 (nuclear source variability)

THANK YOU

Shear-layer δ = 2.4 - boosted If the inner spine is moving with e.g. Г = 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 With Г = 15 we expect a jet opening angle of 4o. The measured intrinsic opening angle is 4.2o 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.

Gabriele Giovannini Dipartimento di Astronomia, Bologna University