Direct imaging of AGN jets and black hole

Direct imaging of AGN jets and black hole vicinity Tiziana Venturi tventuri@ira. inaf. it Active Galactic Nuclei 9 Ferrara, 27. 05. 2010

Radio VLBI as the most direct way to look into the inner regions of AGNs z=0. 01 -> 1 mas = 0. 2 pc z=0. 1 -> 1 mas = 1. 8 pc z=2 -> 1 mas = 8 pc Knowledge of the inner jets in AGN even more relevant these days due to the current γ-ray observatories: true simultaneous radio/γ-ray studies of correlated variability, essential to locate the γ-ray emission. Current hot VLBI studies of AGNs - Simultaneous radio/γ –ray monitoring (radio imaging) of flaring blazars - The very faint Universe: low power nearby AGN (see Giroletti) & powerful high-z quasars

Low power Unified view of Radio Loud AGN FR I and BL Lacs High power FR II and FSRQ Unification models (Orr & Browne 1982; Urry & Padovani 1995) successfully tested in the radio band for the two power ranges : viewing angles and intrinsic relativistic speeds at the jet base

AGNs all very similar from a morphological point of view when looked on the parsec-scale: mostly core-dominated with an asymmetric jet, regardless of the classification (radio galaxies, BL Lacs, FSRQ) Orientation and relativistic velocities at the jet base Mkn 421 3 C 454. 3 BL Lac Markarian 421 – Blue BL M 87 - FRI BL Lac – Red BL M 87 3 C 454. 3 - FSRQ Cygnus A Images from MOJAVE at 15 GHz Cygn A - FRII

Sample of low/intermediate power radio galaxies (Giovannini et al. 2001) Sample of neraby BLLacs (Giroletti et al. 2004) Consistency in the distribution of Lorentz factors

Sample of low power radio galaxies Sample of nearby BLLacs (Giovannini et al. 2001) (Giroletti et al. 2004) Distribution of viewing angles consistent with the idea that the two classes of radio sources belong to the same population of objects seen under differentangles to the line of sight

The nuclear radio properties of highly beamed sources The Blazar World When we look at the powerful radio sources aligned at small angles to the line of sight, the most extreme properties are found: Observer - Strong flux density variability - Morphological changes implying superluminal speeds - Instabilities in the radio jet

Flux density variability Venturi et al. 2001 & 2003 Expanding cloud of relativistic electrons initially thick at some frequencies and viewed very close to the line of sight

Structural variability and superluminal motion Favourable viewing angle and high intrinsic speed of the radio emitting plasma, lead to superluminal proper motion 1995 - 2010 PKS 1510 -089 HPRQ; z=0. 36 βapp= 23. 76 c 1995 - 2010 2200+420 BLLac; z=0. 0686 βapp= 10. 57 c 1995 - 2010 3 C 454. 3 HPRQ; z=0. 859 βapp= 14. 19 c Polarization and total intensity movies from MOJAVE

3 C 279 VLBA 43 GHz HPRQ, z=0. 536 Radio galaxy, z=0. 033 βapp = 20. 57 c βapp = 5. 43

Current studies. I. Statistics from the MOJAVE survey The sample & the project Ideal band: high angular resolution, very good - Nearly 300 compact AGN in the Northern Sky, 135 of which formimage a and better o, S complete flux density limited sample (δ > -20 sensitivity 2 cm > 1. 5 Jy at any reliability compared to BU epoch between 1994 and 2004) monitoring - Monitoring carried out with the VLBA at 2 cm starting from 1994 - Statistical analysis made on the basis of the original sample: 135 sources 526 separate features in 127 jets (no speed measurements for 8 sources) database consisting of 2424 images

Analysis carried out for BL Lacs, FSRQ and radio galaxies separately (Lister et al. 2009) Peak at ~ 10 c Fastest component moving at 50. 6 c and interpreted as the upper end of the AGN jet Lorentz factor distribution Apparent velocity vs redshift: the distribution is not the result of observational limitations

Locus of (βapp, L) for sources with γ=32 and L=1025 W/Hz VLBA observational limit set at S=0. 5 Jy and μ=4 mas/yr Radio galaxies BL Lacs Quasars

Current studies. II. Simultaneous radio/γ-ray monitoring with VLBI imaging Before the advent of AGILE, FERMI and ground-based new VHE observatories, only a handful of simultaneous multiband campaign carried out on the best known blazars (i. e. 3 C 279, Mrk 421 …) with a variety of results (Hartmann et al. 2001; Blazejowski et al. 2005), or a posteriori correlations (Jorstad et al. 2001) γ-ray radio γ-ray flare Superluminal ejection

PKS 1510 -089 (Marscher et al. 2010) VLBA 43 GHz monitoring & Fermi LAT and AGILE observations Optical and γ-ray flares in good coincidence Rotation of the optical polarization vector 2 new superluminal features with speeds of 24± 2 c and 21. 6± 0. 6 c Multiband observations interpreted as a single feature (seen as superluminal) moving through a helical magnetic field in the jet acceleration zone

3 C 454. 3 (Vercellone et al. 2010) VLBA 15 GHz monitoring & AGILE observations 15 GHz - 7 Aug 2007 Flares in the optical and γ-ray band Slow monotonic flux density increase at radio wavelengths Total flux density increase due to the radio core (component C) Flux density of the main jet components stable or decreasing No proper motion along the jet No birth of new components so far From the core variability at 43 GHz it was derived that the source is viewed at θ~1. 5° and that Γ~20

The case of M 87 (Giroletti et al. 2010) Coordinated radio-VHE (VERITAS) observational campaign VHE flares on 9/2/2010 and April 2010 Second radio galaxy, beyond 3 C 84, detected at high energies

ATel #2431 – VHE flare on 9 Feb 2010 e. VLBI monitoring – 2 epochs before the flare and 4 during and after the flare Inner jet HST-1 Evidence for flux density increase at the jet base (~10%) and continued proper motion in HST-1 with vapp~7 c

Current studies. III. VLBI Imaging of high-z quasars - Frey et al. High-z radio quasars with available SDSS spectroscopy Sample selection: z>4. 5; compact on FIRST with 8. 8 m. Jy < S 1. 4 GHz <28. 8 m. Jy z=4. 92 z=5. 01 α=-0. 60 α=-0. 58 z=4. 73 z=4. 87 α=-0. 55 α=-0. 58 VLBI results: • EVN detection rate 100% at 1. 6 GHz (top row) as well as at 5 GHz (bottom row) (the sample was not selected on flat radio spectrum!) • Compact sources, but 4 out of 5 have steep spectrum (α~-0. 6) on this scale

Main current ground VLBI facilities VLBA (δ≥ -30 o) : 327 MHz - 43 GHz, 512 Mbps www. nrao. edu GMVA (δ≥ -30 o ): up to 86 GHz LBA (southern hemisphere): up to 22 GHz European VLBI Network (δ ≥ -10 o): 1. 4 - 22 GHz, 1 Gbps e-EVN, more flexible and more frequent than EVN www. evlbi. org Major support provided to new users by the JIVE staff

Future Space VLBI missions Space Radio Telescope – 2011 327 MHz, 1. 6, 4. 8, 15 -22 GHz www. asc. rssi. ru/radioastron/news. html ASTRO-G – 2014 www. vsop. iasa. ac. jp/vsop 2 Dual Pol. – 8. 4, 22, 43 GHz sub-mas to μas resolutions from 327 MHz to 43 GHz

Final Considerations VLBI is the only way to directly image the central regions in AGNs The present performances and flexibility of VLBI and e-EVN make AGN cores and jets and very faint AGN the most targeted sources these days The new space and ground-based high energy observatories have revived the interest in the study of the inner regions in powerful radio galaxies: monitoring of large samples are the current approach

Current radio programs - I. Imaging Monitoring MOJAVE Imaging + monitoring survey (~200 sources) – VLBA @15 GHz TANAMI southern monitoring of blazars (~80 sources) – LBA @ 8. 4 & 22 GHz BU Blazar Group 22 & 43 GHz VLBA imaging monitoring of ~ 20 sources VIPS VLBI Imaging and Polarimetry Survey, VLBA@5 GHz, ~1200 sources USNO-RRFID Database of geodetic observations at 2. 3/8. 4 GHz and 22 GHz DXRBS EVN observations at 5 GHz of ~ 100 sources from the DXRBS sample

Current radio programs - II. Single dish monitoring UMRAO UMich Radio Observatory, full polarization long term monitoring at 4. 8, 8. 4, 15 GHz of ~ 50 bright sources Ratan monitoring survey of ~ 700 bright sources Metsahovi long term monitoring (~ 100 sources) @ 22 & 37 GHz OVRO daily monitoring of ~ 1000 sources @ 15 GHz FGamma Eb (11 cm to mm)/IRAM (1, 2, 3 mm) simultaneous monitoring Medicina and Noto Monthly monitoring of ~ 30 sources at 5, 8. 4 and 22 GHz