1. THE HST VIEW OF LINERS AND OTHER LOCAL AGN MARCO CHIABERGE CNR - Istituto di Radioastronomia - Bologna Alessandro Capetti (INAF-OATo) Duccio Macchetto (STScI) NGC 4438 - HST/WFPC2

2. What are LLAGN? Radio quietRadio loud (Nearby) galaxies with evidence for AGN activity and nuclear emission lines L(H  ) < 10 40 erg s -1 (Ho et al. 1997) Low Ionization Nuclear Emission-line Regions LINERs Seyferts Low Luminosity Radio Galaxies > 30% of nearby galaxies are LLAGN [OIII] / [OII] < 1 [OIII] / [OII] > 1

3. Compact radio cores in LINERs and Seyferts: a clear signature of an active nucleus Unresolved on the mas scale T B > 10 8 K Flat radio spectrum  ~ 0.0 - 0.6 (F  -  ) The radio cores are variable Radio cores are synchrotron emission from a jet (Nagar et al 2002, Falcke et al. 1999) SIMILAR TO THE CORES OF RADIO GALAXIES

4. THE SAMPLE of LLAGNs FR I radio galaxies from the 3CR catalog LINERs all liners with d < 19 Mpc from the Palomar sample of nearby galaxies Radio data from Nagar et al. 2001 18/21 have HST images Seyfert 1 from Ho & Peng 2001 Seyfert 1 from Palomar sample (d med = 20 Mpc) + Seyfert 1 from the CfA sample (d med = 80 Mpc) 25/32 have HST images THE LOCAL AGNs ARE WELL REPRESENTED BY THE 3 COMBINED SAMPLES

5. LLAGN - LINER nuclei NGC 4278 - HST WFPC2- I bandNGC 4589 - HST WFPC2- I band 15’’

6. LLAGN - Seyfert 1 nuclei NGC 5033 - HST WFPC2 - V band

7. 3C 338 3C 31 FR I RADIOGALAXIES: synchrotron nuclei Chiaberge, Capetti, Celotti 1999 Chiaberge et al. 2003

8. DETECTION RATE of optical nuclei LINERs 7/18 39% Seyfert 1 100% FR I radio galaxies 85% EXPECTED: Type1 = clear view of the nucleus, by def intrinsically fainter?

9. LLAGN IN THE RADIO-OPTICAL PLANE LINERs FR I Sy1 Radio galaxy - like Seyfert - -like Synchrotron radiation in optical and radio (CCC 1999) Thermal excess

10. NUCLEAR RADIO LOUDNESS OF LLAGN Seyfert 1’s nuclei are NOT radio loud!! A fraction of LINERs is RADIO LOUD RL RQ

11. 2 populations of LINERS Radio quiet, Seyfert - like radio: non thermal optical: thermal emission from the accretion process Radio -loud, radio galaxy - like radio AND optical: non-thermal emission from the jet RADIO LOUNDESS TELLS US WHAT IS THE PHYSICAL MECHANISM WE ARE OBSERVING IN THE TWO BANDS

12. BLACK HOLE MASS VS. RADIO LOUDNESS RQ RL QSO at z ~1-2: RL only for M BH /M  > 10 9 (Dunlop et al. 2003) FR I SY 1 LINER M BH from direct measurements or correlations (e.g. Tremaine et al. 2002)

13. ACCRETION EFFICIENCY VS. RADIO LOUDNESS M black hole m. RL RQ FR I SY 1 LINERs L Edd = 1.3 x 10 38 (M BH /M  ) erg s -1

14. CONCLUSIONS Seyferts small BH M < 10 8 M  high accretion rate m <~ 1 RQ LINERs small BH M < 10 8 M  low accretion rate m << 1 RL LINERs large BH M > 10 8 M  low accretion rate m << 1. Radio galaxies. There are two types of LINERS: Sy-like and RG - like RQ RL ADAFs observed in the optical?.

15. AGN structure and unification model Urry & Padovani 1995 Type 2 Type 1

16. R = F  cm / F  RADIO QUIET / RADIO LOUD AGN The distribution of R in optically selected samples of quasars has been historically found to be BIMODAL R > 10 RADIO LOUD R < 10 RADIO QUIET Kellermann et al. 1989, 1994 Recent studies have questioned quasars bimodality White et al. 2000, Cirasuolo et al. 2003 What is the physical meaning of radio-loudness in LLAGN?

17. In the OPTICAL the host galaxy dominates in ground based observations LINERS and Seyferts from the PALOMAR sample Filippenko & Sargent 1995; Ho, Filippenko & Sargent 1997 optical spectroscopic survey of all 486 northern galaxies with B<12.5 mag SAMPLES OF LLAGN > 30% are LLAGN: LINERs (~20%) or Seyferts (~10%)

18. Why study LLAGN? Proximity (d << 100 Mpc) means high spatial resolution fueling mechanisms, local environment Quasars quasar remnants Accretion onto black holes at the lowest rates How do AGNs turn off?

19. OUTLINE OF THE TALK Observational properties of the different classes LLAGN The nuclear structure of low luminosity radio galaxies The HST view of the central regions of LINERs: optical nuclei, radio loudness, accretion process

20. OPTICAL EMISSION LINES Seyferts [OIII] / [OII] > 1 powered by AGN LINERs [OIII] / [OII] < 1 LLRG LINERS AND LLRG HAVE SIMILAR OPTICAL SPECTRA ionization mechanism: AGN, SHOCKS or HOT STARS?

21. M 84 = 3C272.1 VLA @1.4 GHz FR I radio morphology (Laing & Bridle 1987) Optical, Palomar 1.5 m 250” ~20 kpc

22. Seyfert galaxies NGC 4258 = M 106 Mundell et al. 2000

23. NGC 1052 VLA 1.4 GHz ~3 kpc LINERs NGC 4278 - VLBA 5GHz Hosts: Ellipticals + spirals Giovannini et al. 2000 Wrobel et al 1984

24. X rays ASCA ( Terashima et al. 2002) L 2-10kev = 4 x 10 39 - 5 x 10 41 erg s -1   non-thermal?  H < ~ 10 22 cm -2 A few Seyfert 2 have  H > 10 23 cm -2 Chandra basically confirms the ASCA results ( Terashima & Wilson 2003) AGAIN SIMILAR TO LLRG

25. FR I OF THE 3CR CATALOG Complete sample: 33 objects, 32 with HST R-band observations The HST/WFPC2 snapshot survey of 3CR radio sources (P.I. Sparks)

26.  Chiab, Capetti & Celotti 1999, Capetti et al. 2002, Verdoes-Kleijn et al. 2001 NON-THERMAL SYNCHROTRON EMISSION FROM THE BASE OF THE JET NO OBSCURATION - NO RADIATIVELY EFFICIENT ACCRETION THE RADIO-OPTICAL CORE CORRELATION OF 3CR FR I RADIO GALAXIES

27. 3CR QSO and BLRG WITH z < 0.3 FR I Thermal emission from the accretion disk 3C 390.3 - HST R-band CCC 2002

28. Radio cores Optical cores LINERS have the faintest nuclei

29. Ho & Peng 2001 The majority of Seyfert1 nuclei are radio loud

30. WE NEED AN ESTIMATE OF THE BH MASS Tremaine et al. 2002 What about the radiation efficiency?

31. Black hole masses of local AGNs from direct measurements or correlations (e.g. Tremaine et al. 2002) On average Sy1’s BH have lower masses than LINERs and FR I

32. ACCRETION EFFICIENCY vs. RADIO CORES FR I LINERs SY 1 ADAF? L Edd = 1.3 x 10 38 (M BH /M  ) erg s -1

33. CONCLUSIONS At low luminosities, the radio loudness properties of the nuclei are still different The difference between the various classes is possibly due to the properties of the accretion process and of the central BH mass There are two types of LINERS: Sy-like and RG - like RQ RL ADAFs observed in the optical?