http://pos.sissa.it/ PoS(IX EVN Symposium)028 1 mJy ∼ S Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. c ∗ [email protected] [email protected] Speaker. In this contribution, we report on dual-frequency EVNies observations imaged of previously six at nuclei arcsecond resolution of with Seyfert the galax- limited VLA. sample These galaxies of are Seyferts, part for of a whichjects. distance- VLBI observations Our are observations available consider only for for the the brightest first ob- time sources with flux density around (VLA cores), which represents a significant stepous to works. lower flux They density are levels thus with an respect importantin to step Seyfert previ- towards galaxies an as understanding a of population. the emission mechanism ∗

Marcello Giroletti Francesca Panessa INAF IASF, via Fosso del Cavaliere 100,E-mail: 00133 Rome, Italy EVN observations of Seyfert galaxies INAF Istituto di Radioastronomia, via GobettiE-mail: 101, 40129 Bologna, Italy The 9th European VLBI Network Symposiumand on EVN The Users role Meeting of VLBISeptember in 23-26, the 2008 Golden Age for RadioBologna, Astronomy Italy PoS(IX EVN Symposium)028 ]. 1 ). Finally, 3 ]. The radio 10 Marcello Giroletti K and is located within a 8 . 10 4 × ]. 5 2 > b T ) and present the results of new European 2 ] a complete sample of 27 nearby Seyfert galaxies. 2 8 ], characterized by a central elongated structure with K) and closely aligned to a well detected maser disk. 2 6 ]. 10 6 , × 4 5 27 Mpc) and XMM data are available in the X-ray band [ . 2 < = d b T ), with bright compact cores (showing in some cases superluminal mo- 1 − W Hz 035 pc, i.e. comparable to the broad line region (BLR) scales. The VLBI compact . 22 0 10 < ]. This correlation holds for both RQ and RL sources, although the two groups are > 7 r ]. This suggests a similarity to the case of X-ray binaries (XRB), in which jets are more L 9 , 3 Very Long Baseline Interferometry observations of LLAGN and Seyfert galaxies are tradition- NGC 4151 is a radio-quiet Sy 1.5 nucleus studied with the VLBA at 15 GHz [ Another remarkable case is NGC 1068 [ While the radio emission in RL AGN is certainly due to the synchrotron process, the case for Moreover, there is evidence for a trend of increasing radio-loudness with decreasing Eddington Active Galactic Nuclei (AGN) are traditionally divided in radio quiet (RQ) and radio loud In order to discuss possible relations between the formation of jets in LLAGN and the accretion We have selected and presented elsewhere [ flat-spectrum radio component has a brightness temperature This suggests that the radio emissioncorona could or arise from from thermal a free-free wind process arising in from an a X-ray-heated molecular disk. ally difficult due to the low radioare luminosity bright of this enough sources. to Nevertheless, be the imagedour really and nearby sample, several sources some works interesting have facts reported have the recently results. been Among found. the sources in The sample is distance limitedVLBI ( images are available inand the we literature are only interested for in asummarize extending few some the bright results dataset objects on to (the the fainter really literature sources. nearby data ones) In (Sect. this contribution, we shortly 2. Literature data source size is two sided structure extending to thesuggesting large scale only radio mild jet. jet Sub-relativistic velocities motions or have a been large found, viewing angle. lower brightness temperature ( VLBI Network observations for 6 objects with VLA cores at the milliJansky level (Sect. dominant at lower accretion, while disks become less prominent [ we summarize preliminary conclusions and future prospects in Sect. RQ AGN is much less clear. Afrom clue the about study the of nature scaling of relations. the radio Recentluminosity emission works extending in have Seyfert over found galaxies 8 a comes correlation orders between of(LLAGN) X-ray magnitudes, and [ radio down to the regime of Low-Luminosity AGNs ratio [ separated by an offset in X-ray luminosity. (RL). The latter aresources ( common targets oftions) VLBI and large observations: scale radio they lobes.emission Radio are is quiet confined AGNs typically to are the much powerful sub-kpc fainterAGN radio scale. radio are sources However, radio moderately and sources deep their at VLA radio some surveys show level that [ most rate, we need to look at theresolution radio and emission superior to sensitivity, see which if explains it why is this actually radiated topic by has a not jet. been This challenged requires before. high EVN observations of Seyfert galaxies 1. Introduction PoS(IX EVN Symposium)028 × 6 . 3 04 mJy. = . 0 BH ± . In general, M 2 74 . Marcello Giroletti Source ) from the tentative phase centers 00 10 mas (HPBW). The corresponding ν (GHz) < 2 Mpc. For this source, the visibility data . We used the maximum recording rate of . 1 were affected by major recording or weather 10 = d 3 italics 004), and a radio flux density of 0 . , Ur, Nt, Hh 1.6 NGC 4388, 4501, 5194 , Ur, Nt 5 NGC 4051, 5033, 5273 0 Sh Sh = Edd L / K, i.e. suggestive of the presence of Doppler beaming. X L 8 10 , On, Mc, Tr, Sh, Ur, Nt, Hh 5 NGC 4388, 4501, 5194 , On, Mc, Tr, > Ef Ef , Wb , Wb, K) and an elongated structure which suggests radio outflow on sub-pc scales Jb 6 , and discussed in the following subsections. The image parameters are given in 10 3 × Log of observations. Stations listed in 2 -coverage. Amplitude calibration was done a priori in the standard EVN pipeline; phase > , and ) 2 B ), a low Eddington ratio ( v , , T

1 u NGC 4051 is classified as a Sy 1.5 galaxy at We observed with the EVN at 1.6 and 5 GHz the nuclei of six Seyfert galaxies: NGC 4051, Phase coherence was clearly detected on the baselines with large sensitive telescopes in four We detected with high confidence NGC 4051, NGC 4388, NGC 4501, NGC 5033 at 1.6 GHz Finally, a good case of an extremely weak source though successfully revealed with VLBI is ( problems. 2008 Feb 28 Jb, Wb, Ef, On, Mc, Tr, Table 1: Date2007 Jun 62007 Telescopes Jun 1 Jb, Wb, Ef, On, Mc, Tr, Jb, Sh, Ur, Nt 1.6 NGC 4051, 5033, 5273 2008 Mar 10 M ]. 5 11 brightness temperatures are 3.2 NGC 4051 the figure captions andthe a detected comparison galaxies to have the a10 VLA flux and properties density 50% on of is the reported VLA scales in flux that Table density, is and around estimated 0.5–1 sizes mJy, i.e. between NGC 4388, NGC 4501, NGC 5194, and NGCdates 5273, and between participating 2007 telescopes June are and 2008 reported March. in The Table exact cases at 1.6 GHz andsignificant failures in at one some of case the at largestsources. apertures, 5 thus We GHz. possibly also compromising found the Note detection significant that of displacements the the (as large 5 as GHz 1 observations were affected by and NGC 5033 at 5Figs. GHz. Images of the host galaxy and of the VLBI detections are shown in 10 3. New EVN observations 1 Gbps and each source was observedthe for about 6 hr, switching betweencorrections targets were in order obtained to using improve observationsreferencing technique. of bright nearby calibrators, in the so-called phase adopted in the schedules, owing to the lack of previous3.1 high resolution Results observations. NGC 4395. This radio-quiet type 1 nucleus has an intermediate mass ( EVN observations of Seyfert galaxies Thanks to deep VLBI observations,core it ( has been possible[ to reveal a high brightness temperature PoS(IX EVN Symposium)028 ). 00 8 ] and × 4 00 12 ∼ VLA Marcello Giroletti α VLA 5GHz S ). ◦ 4GHz . VLA 1 S 7.311.62.1 3.2 7.98.0 0.7 1.1 0.3 4.2 0.5 0.5 31 Mpc hosting an unresolved VLA = 5 6 6 6 d 9 mas, in PA 7 10 10 10 10 × × × × × 1 3 4 3 . . . . B T 4 ) (K) (mJy) (mJy) 1 − 34 Mpc, this galaxy hosts a central radio source resolved = d VLBI . It is therefore identified as the “true” core, probably obscured 5GHz 1 P − ) clearly detect compact radio emission from this component, with 1 ) (mJy beam 1 − ]. 4 6GHz . VLBI 1 P (mJy beam Properties of the radio cores. VLBI data (Cols. 1-3) are from the present work; VLA data Images of NGC 4388. Left: color image from the (size At 6 cm, we lack sensitivity but emission is detected at low SNR ratio. Known also as M 88, NGC 4501 is a Sy 2 galaxy at Our observations (see Fig. Classified as a Sy 2 (or 1.9) at (Cols. 4-6) are from [ Table 2: Source NGC 4051 1.0? ... 1 NGC 4388 0.8NGC 4501 0.6NGC 5033 1.4NGC 5194 ...NGC 5273 ...... 1.0 ...... 1 1 3 ...... 3.4 2.1 1.3 1.3 0.8 0.4 3.4 NGC 4501 at optical wavelengths. There is alsojet, an while extension no to emission the is NE detected that from could the be southern interpreted component. as a tentative references therein). a 1.6 GHz peak of 0.8 mJy beam Figure 1: Right: 1.6 GHz EVN images of the central region (beam 35 EVN observations of Seyfert galaxies at 1.6 GHz show thatmodel emission fit. For on this parsec reason, we scales do is not show clearly a present, clean map, although3.3 which difficult we NGC hope to 4388 to image produce or in a future paper. into two peaks, neither of whichor coincides even with inverted, the optical spectral nucleus; index the up northern to peak has 2 a cm, flatter, and it has a size upper limit of 70 mas (see [ PoS(IX EVN Symposium)028 ). ). 00 00 8 8 × × 00 00 12 12 . The peak ∼ ∼ 2 Marcello Giroletti ). ◦ ). 24 ◦ − 10 mas, in PA 7 13 mas, in PA × × 5 and our data account for a large fraction of the VLA detected flux ). Our resulting spectral index is slightly flatter than the one measured 1 3 − ]). We are probably detecting the inner component of a slightly extended 4 ] and references therein). We detected this source also on parsec scales; in 4 5, [ . 0 = α ]. We detected this source at 1.6 GHz and show the image in Fig. 4 7 Mpc (see [ Images of NGC 5033. Left: color image from the Sloan Digital Sky Survey (size Images of NGC 4501. Left: color image from the Sloan Digital Sky Survey (size . 12 VLA data at 6 and 20 cm show an unresolved or slightly resolved core in this Sy 1.9 galaxy = d at on larger scale ( Right: 1.6 GHz EVN images of the central region (beam 22 radio source [ brightness is 0.6 mJy beam density at 20 cm, suggesting that the radio source is highly compact. 3.5 NGC 5033 fact, this is the only objectGHz that image is is detected shown in in Fig. our EVN observations at both 1.6 andshort 5 jet, GHz (the although 1.6 the uncertaintyon in the amplitude spectral calibration index and quite possible large. variability make the error Figure 3: Right: 1.6 GHz EVN images of the central region (beam 36 Figure 2: EVN observations of Seyfert galaxies PoS(IX EVN Symposium)028 K, i.e. presum- Marcello Giroletti 6 80% of the sources. This 2002, A&A, 392, 53, ∼ Radio sources in low-luminosity active 2002, A&A, 382, L13, [arXiv:astro-ph/0112385] 6 The Parsec-Scale Radio Structure of NGC 1068 and the X-ray spectral survey with XMM-Newton of a complete 2004, ApJ, 613, 794, [arXiv:astro-ph/0406062] Population X: Are the super-Eddington X-ray sources beamed jets 2006, A&A, 446, 459, [arXiv:astro-ph/0509584] Radio Continuum Survey of an Optically Selected Sample of Nearby Seyfert On the Relationship between Radio Emission and Black Hole Mass in Galactic Nuclei 2001, ApJS, 133, 77, [arXiv:astro-ph/0102506] at 1.6 GHz and somehow higher at 5 GHz. 1 − sample of nearby Seyfert galaxies Galaxies Nature of the Nuclear Radio Source 2002, ApJ, 564, 120, [arXiv:astro-ph/0110440] in microblazars or intermediate mass black holes? [arXiv:astro-ph/0207176] galactic nuclei. III. “AGNs” in a distance-limited sample of “LLAGNs” Overall, the detection rate of compact parsec scale components remains strikingly high and the The European VLBI Network is a joint facility of European, Chinese, South African and other The six sources presented in this paper are part of a larger sample of Seyfert galaxies. The Compact components are not revealed in NGC 5194 and NGC 5273 (a Sy 2 and a Sy 1.5, re- [2] Gallimore, J. F., Baum, S. A., O’Dea, C. P. [1] Cappi, M., Panessa, F., Bassani, L., et al. [3] Ho, L. C. [4] Ho, L. C., Ulvestad, J. S. [5] Körding, E., Falcke, H., Markoff, S. [6] Nagar, N. M., Falcke, H., Wilson, A. S., Ulvestad, J. S. measured brightness temperatures are also remarkable (generally in excess of 10 radio astronomy institutes funded by their nationalresearch research funding councils. from This work the has European benefitedR113CT from Community’s 2003 sixth 50 58187. Framework Programme under RadioNet References fraction is still somehow uncertain owingsible to that the some faint of nature the of nonwith the detections a sources. are more In not thorough particular, due analysis it to and/oris is physical more also pos- reasons accurate most but positions. likely can due The actually to lowest be bad detection recovered observing rate conditions at rather 5 than GHz to peculiar spectral properties. ably non thermal). We anticipatefuture that observations and of will even improve fainter the cores statisticsof will the on be nature the of doable sample. the in radio The theX-ray emission ultimate near in emission goal Seyfert (disk/corona). galaxies remains (cores/jet/outflows) the and understanding of its coupling to the Acknowledgments present data set completes thewith observations the of VLA all at the 1.4 galaxies and for 5 which GHz. radio cores Parsec are scale detected cores are detected in 4. Preliminary conclusions and future prospects spectively) within 1” radius from thebeam phase centers. Upper limit peak brightness is around 0.1 mJy EVN observations of Seyfert galaxies 3.6 NGC 5194 and NGC 5273 PoS(IX EVN Symposium)028 The The X-ray and Marcello Giroletti VLBA Identification of the 2005, AJ, 130, 936, 2008, cosp, 37, 2340 2007, A&A, 467, 519, [arXiv:astro-ph/0701546] 7 Radio Loudness of Active Galactic Nuclei: Observational Facts 2007, ApJ, 658, 815, [arXiv:astro-ph/0604095] Radio Emission on Subparsec Scales from the Intermediate-Mass Black Hole 2006, ApJ, 646, L95, [arXiv:astro-ph/0606600] radio connection in low-luminosity active nuclei X-ray and radio connection in local Seyfert galaxies and Theoretical Implications Milliarcsecond Active Nucleus in the NGC 4151 [arXiv:astro-ph/0505141] in NGC 4395 [8] Panessa, F., Cappi, M., Pellegrini, S., Barcons, X., Bassani, L., Carrera, F., Ho, L., Giroletti, M. [7] Panessa, F., Barcons, X., Bassani, L., Cappi, M., Carrera, F. J., Ho, L. C., Pellegrini, S. [9] Sikora, M., Stawarz, Ł., Lasota, J.-P. EVN observations of Seyfert galaxies [10] Ulvestad, J. S., Wong, D. S., Taylor, G. B., Gallimore, J. F., Mundell, C. G. [11] Wrobel, J. M., Ho, L. C.