PoS(11th EVN Symposium)089 http://pos.sissa.it/ ), accompanied α − ν ), we propose the hot ∼ σ ) 5 ν ( ∼ S 6, . 0 < 22 Mpc) low luminosity AGNs. We α < < 3 d . d , A. Doi c , a Jy. In three sources, namely NGC 3227, NGC 3982, and µ 100 < , M. Orienti b , F. Panessa 5 K) and flat/intermediate spectral index (0 a . ∗ 7 10 > [email protected] B Speaker. We report on sensitive dual-frequencyof (1.7 the and central 5 region GHz) of Europeanluminous VLBI nine members Network Seyfert of observations . a completedetect These sample radio sources emission of on are nearby milliarcsecond among ( scalesources the in we the faintest set an nuclei and upper of limit least 4 of galaxies, while for the other five NGC 4138, radio emission iscomponents. detected at We both describe 1.7 the andin structural 5 each and GHz of and spectral these it three properties nuclei isT of there resolved these is in features; one two component we or with more find high that brightness temperature (typically corona as the origin of non-thermal emission,required on by the synchrotron basis self-absorption. of the Finally, the unrealisticfurther magnetic five observations non-detected field on values nuclei intermediate remain scales elusive will and be necessary to investigate their nature. by secondary steep spectrum extendedjets components. or In outflows these is cases, thus non-thermalat the 5 emission most GHz; from keeping natural in explanation. mind the A modest faint significance feature of is this detection detected ( in NGC 4477 ∗ Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. Institute of Space and Astronautical Science, JAXA, 3-1-1 Yoshinodai, Sagamihara, Kanagawa INAF - Istituto di Radioastronomia, viaINAF/IAPS Gobetti via 101, del 40129 Fosso Bologna, del Italy CavaliereDipartimento 100, di 00133 Astronomia, Roma, Università Italy di Bologna, via Ranzani 1, 40127 Bologna, Italy c

11th European VLBI Network Symposium &October Users 9-12, Meeting, 2012 Bordeaux, France M. Giroletti 229-8510, Japan E-mail: Physical properties of the nuclear regiongalaxies in derived Seyfert from EVN observations c a b d PoS(11th EVN Symposium)089 ≤ K. 1 α . 9 ≤ 10 3 . ∼ M. Giroletti B T 6) component, . 0 ∼ 3) and K, suggestive of non . α 0 5 . 8 ∼ ] revealed flux density at 5 10 α ∼ is B T 5) and flat spectral index (0 . 7 > 4); the . B 0 T ∼ α 2 50 mas westward (3.5 pc), more extended. 4 mas, flat spectral index ( , we find two more extended, steep spectrum regions. ∼ . ◦ 1 45 ∼ − K, so presumably of non thermal nature. At about 12 pc in 5 . 7 ]. 7 10 , 1 ∼ and 9 pc in PA ◦ – NGC4138 is Sy1.9 . Our EVN observations reveal a main component, – The nuclear region of this Sy1.9 is resolved in two components, one with more – This Sy1.5 core shows a compact (1.2 mas), flat spectrum ( ], but what about the radio emission? Ho&Ulvestad (2001) [ ]. 2 6 NGC 4138 NGC 3982 All the sources detected at both frequencies, i.e. NGC3227, NGC3982 and NGC4138, present For the faintest sources in the sample, the extraordinary sensitivity of the European VLBI NGC 3227 We are studying a sample of 28 local Seyfert galaxies to understand the physical properties of ]. Motivated by the success of the previous experiment, we observed eight more targets with the 6), which we ascribe to non-thermal emission from the immediate vicinity of the central black . 4 detected at the two frequencies, with size thermal emission. The otherspectrum. component is 8.5 pc away and it is more resolved and with steeper 0 At 1.6 GHz, a second component is detected compact structure (0.9 mas) and flatter spectrum ( one component with high brightness temperature (log position angle (PA) 170 4. Physical properties Network is a key resource. We reportedEVN in observations for Giroletti 5 & objects, Panessa resulting (2009) in the[ clear results detections of for dual-frequency 4 of them, at least at one frequency the milliJansky level in 80%the of high them, using resolution the of VLAinterpretations VLBI at include 1.4 to thermal and free-free clarify 5 emission from the GHz. anstructures nature Various X-ray authors heated with of exploited corona low or the two-sided speeds, jet-like cores indicatingas of non-relativistic in the jet NGC brightest motion, 4151. sources. possibly due Possible to thermal plasma 2. EVN enters the game: old and new observations same setup, including also theclearly Arecibo revealed three radio sources telescope at for twocomponents sources frequencies, plus are with one found suitable source also declination. at in 5A We GHz other detailed only. sources Low discussion but significance of itprovided these is in observation hard dedicated and papers to [ of claim the real statistical detections in analysis these of cases. the3. whole sample Notes is on single sources with brightness temperature This VLBI structure connects nicelyimages to [ the larger scale emission observed in literature MERLIN their nuclear regions. X-rayof observations them reveal nuclear [ activity at low luminosity levels in most Physical properties of the nuclear region in Seyfert galaxies derived from EVN observations 1. Background PoS(11th EVN Symposium)089 , we 2 ,426, and M. Giroletti 1 MNRAS , eq eq B B ) (mG) ) (mG) 3 3 − − min min U U 5.766.906.83 4.3 4.53 1.2 6.14 1.3 17.8 4.866.73 2.8 12.2 1.4 4.966.61 10.9 6.314.93 1.6 6.37 2.3 11.2 4.525.59 2.1 18.1 5.2 − − − − − − − − − − − − − − log log ) (erg cm ) (erg cm Physical properties of the nuclear 3 3 V V − − log log ) (cm ) (cm 1 1 − − L L log log 3 ]. The undetected sources remain a mystery; since 3 B B T T (K) (W Hz (K) (W Hz Physical quantities at 5 GHz. Columns as in Table 1. SNS 6.5W 6.1 20.5 7.2 19.7 56.9 6.6 20.0 55.9 S1 18.8 54.9 S2 54.8 S 5.4 5.8 19.1 19.1 5.7 54.9 54.4 19.3 54.7 Table 2: NGC 3227 CNGC 3982 CNGC 4138 7.5 C 19.8 9.1Source 54.1 8.5 19.8NGC Component 3227 log C 19.4 52.0 NGC 3982 52.1 CNGC 4138 7.5NGC C 4477 C 19.5 7.6 52.4 7.8 19.7 6.5 19.2 52.5 18.7 51.4 52.7 Source Component log Physical quantities at 1.7 GHz. Col. 3: brightness temperature; col. 4: monochromatic luminosity; 588, [arXiv:1208.0230] region in Seyfert galaxies derived from observations with the European VLBI Network The European VLBI Network is a joint facility of European, Chinese, South African and [1] Bontempi, P., Giroletti, M., Panessa, F., Orienti, M., & Doi, A. report physical parameters for the various componentsenergy. estimated under The the parameters assumption of we minimum derivemG. are On reasonable; the e.g. other hand, the in equipartitionand NGC magnetic the 4477, field detected physical is only parameters at of are 5 abecause at GHz, few odd of the brightness with the temperature a too is synchrotron lower, highseems self-absorption magnetic (SSA) more field scenario, viable, mainly required; similar a to thermal NGC free-free 1068 origin [ for its radio emission other institutes fundedsupported by by their the national European research Community Framework councils.Europe, Programme grant This 7, Advanced effort/activity agreement Radio is No. AstronomyAffair in Minister 227290. under the We bilateral acknowledge scientific a collaboration contribution between Italy from and the Japan. ItalianReferences Foreign hole; steep spectrum extendedthe components core, are suggesting also the detected presence within of some jets tens or of outflows on from scales. In Tables they have weak butinvestigate compact their cores nature. in VLA images, e-MERLIN observations wouldAcknowledgments be ideal to Table 1: col. 5: volume; col. 6: minimum energy density; col. 7: equipartition magnetic field. Physical properties of the nuclear region in Seyfert galaxies derived from EVN observations PoS(11th EVN Symposium)089 M. Giroletti ,432, 1138, Anisotropic ,706, L260, ApJ , MNRAS , ,275, 67 MNRAS , 4 The Parsec-Scale Radio Structure of NGC 1068 and the X-ray spectral survey with XMM-Newton of a complete ,613, 794, [arXiv:astro-ph/0406062] ,446, 459, [arXiv:astro-ph/0509584] ApJ , A&A , Radio Continuum Survey of an Optically Selected Sample of Nearby The Faintest Seyfert Radio Cores Revealed by VLBI Sub-parsec radio cores in nearby Seyfert galaxies ,133, 77, [arXiv:astro-ph/0102506] ApJS , sample of nearby Seyfert galaxies Nature of the Nuclear Radio Source [arXiv:0910.5821] Seyfert Galaxies radio and optical emission in the Seyfert nucleus of NGC 3227 [arXiv:1304.0794] [2] Cappi, M., Panessa, F., Bassani, L., et al. [3] Gallimore, J. F., Baum, S. A., & O’Dea, C. P. [4] Giroletti, M., & Panessa, F. [7] Panessa, F., & Giroletti, M. [5] Ho, L. C., & Ulvestad, J. S. [6] Mundell, C. G., Holloway, A. J., Pedlar, A., Meaburn, J., Kukula, M. J., & Axon, D. J. Physical properties of the nuclear region in Seyfert galaxies derived from EVN observations