PoS(8thEVN)035 http://pos.sissa.it/ ly resulted in non-detections. e galactic nuclei is that both a tentative detection. have a high X-ray absorbing col- t a spectral line VLBI observation ted rotational states of OH and by transitions, deserve some attention of the transitions at 6031 MHz and ar engines blocked from direct view with diameters of a few hundred par- ns to observe. To explore these effects, re is sufficiently high, the content of the citation effects, in which coupling to the 10 pc) have been difficult to detect. Searches for < [email protected] , e Commons Attribution-NonCommercial-ShareAlike Licence. ∗ [email protected] [email protected] torus should mostly be molecular. Although molecular rings One of the fundamentalSeyfert concepts 1 in and Seyfert the 2 unifiedby harbour an scheme supermassive optically nucle and of geometrically activ thick torus. If the pressu secs are common, the expected small scale tori ( absorption lines of common molecules like CO and OH have most Before concluding that tori are not molecular, radiative ex nonthermal continuum can suppress the opacityand in influence the our lowest selection of the mostwe favourable transitio modified the search strategy byselecting looking a for sample the of higher 31 exci Seyfert 2 galaxies which are known to 6035 MHz, yielding detections in five sources.carried out We at also 13.4 presen GHz towards the core of Cygnus A, yielding umn. We present here the results of single dish observations Speaker. ∗ Copyright owned by the author(s) under the terms of the Creativ c

The 8th European VLBI Network Symposium September 26-29, 2006 Poland Toru´n, Max-Planck-Institut für Radiostronomie, Bonn, Germany E-mail: Alan L. Roy, Christian Henkel Max-Planck-Institut für Radiostronomie, Bonn, Germany E-mail: C. M. Violette Impellizzeri Molecular tori in AGN: a search using excited states of OH PoS(8thEVN)035 ± of a broad 50 mJy > = (3.75 H N 6GHz y for molecular S n temperature of ontinuum source larized broad-line s in the torus may wn OH absorption ry few cases could e and extent of the al lines of evidence efforts to detect the z, so far neglected, to search for OH in the lower transitions is radiatively excited. (see Table 1) selected f the stronger sources 92, Staveley-Smith et , the radio continuum ificant column density heme of active galactic lumn of ossible solutions. First, d CO J=1-2 absorption, C. M. Violette Impellizzeri ale torus of molecular gas, nd February 2004 with an d in some molecular torus r the 18-cm OH transitions , supporting CO excitation t view in the visible and soft ed properties, but evidence for ) and for having 2 − cm 22 10 ≥ 2 CO by Conway & Blanco [9] yielded non-detections at 1% optical 2 = 0.0565) powerful FR II radio , Cygnus A has been the subject z is consistent with the notion of a buried in Cygnus A [8]. Searches 2 − cm 23 10 × To explore the effects of radiative excitation we modified the search strateg Active galactic nuclei (AGN) come in two main types: those with and those without As the nearest ( to ensure sufficient continuum coreemission, strength. indicating an We obscured included some BLR,at AGN 1.6 and GHz. with some po additional The sources observationsaverage integration were with time carried kno of out 3 h between per August source 2003 and a 40-MHz bandwidth. Twenty o absorption, starting with a surveythe with the higher-order the transitions 100-metre at 6031 telescope MHz and infor 6035 Effelsberg having MHz in a 31 known type 2 high AGN X-ray absorbing column ( number of studies aimed at testingsuggest the that predictions Cygnus of the A unified harboursX-rays scheme. a Sever emission quasar by nucleus a hidden from dusty direc obscuring torus [7]. An X-ray absorbing co 2. Observations challenging the torus model forit Cygnus may A. be The that authors there suggestedbe is three smaller no p than such the torus. sizeemission of Second, from the the the background nucleus sizes continuum may of source. radiativelythe the excite lower Alternatively molecular the rotational CO, cloud increasing levels the and[2]. excitatio suppressing Interestingly, the Fuente absorption et opticalfrom al. depths radiative in excitation [11] effects. report Given 118-GHzmodels, the the CO+ abundances non-detection of absorption of OH OH absorption is predicte Radiative hard excitation to effects explain have unless this, been too, predicted by[12], Black suggesting (1997) also that fo thecould rotationally-excited be doublets more profitable at targets 6 than GHz the and 1.6-GHz lines. 13.4 GH depth [9]. Also, Barvainis & Antonucci [10] failed to detect CO J=0-1 an for 18-cm OH and 6-cm H 0.73) AGN Tori 1. Molecular tori in AGN optical line emission (type 1 and typenuclei, 2 all AGN, AGN respectively). are In intrinsically the similar; unified in sc and type the 2 broad objects line our region view (BLR) of[1]. is the The blocked central obscuring c by material an is obscuring expectedwhose to material be structure of an was sign approximately predicted -sc by, e.g.,expected Krolik molecular & absorption Begelman [3]. or emission Despitemolecular many in absorption a be number confirmed (e.g. ofal. surveys, Schmelz 1992 only et [4], al. in [5], ve 1986, [6]). Baan Thethe et unified existence al. scheme of accounts 19 for a many molecularobscuring observ torus material are remains still somewhat poorly indirect understood. and the structur PoS(8thEVN)035 211180 - - 180 - 205 - 230103 - - 180 - 120 - 205 - eak at 25 23 25 24 10 10 10 10 24 24 24 X-ray Int. time Det × × × × 24 25 10 10 10 H N > > > orresponding to n June 2004 and 5, were too strong cm 6 The data were cali- S ited OH at 13.4 GHz espectively, with 256 005+403 and 2013+370 C. M. Violette Impellizzeri 1052. ctral dynamic range and for he red lines mark the position ffelsberg. † sources observed by Velocity (km/s) locity. The velocity scales refer to the Rest Frequency (MHz)

NGC7130Mrk3Mrk231Mrk273 0.016Mrk463 62 Mrk1210 0.014 0.042Mrk1073 0.037 361 414IRAS05414+5840 103 1.1 0.050IRAS1345+1232 - 0.014 0.015 - 0.024 100 0.121 45 55 1.6 44 2160 10 - - † - † abs abs 180 180 358 - - - SourceNGC5506NGC5793 NGC6240NGC7674. 0.006 0.011 160 0.024 96 3.4 131 0.029 2.2 66.5 230 abs NGC5135 0.014 598 Mrk348F01475-0740 0.015 254 0.177 10 127 - 103 -

Flux Density (Jy) Density Flux 3 Flux Density (Jy) Density Flux ------65 abs 185255 - - 180 - 154 - 180 - 180 - 205 - min 23 22 22 23 23 23 24 23 24 10 22 10 10 10 10 10 10 5 2 25 . X-ray Int. time Det 10 × 10 × × × × × × − 10 23 2 10 H × × - N > < > cm 6 mJy cm S Velocity (km/s) z Rest Frequency (MHz) Absorption spectra of NGC 3079 (left) and NGC 5793 (right). T List of sources observed at 6 GHz with the 100-m telescope in E

Four of our top candidates: Cygnus A, Hydra A, NGC 1052 and NGC 127

Flux Density (Jy) Density Flux NGC2992 0.008NGC4151 0.003 77 6.9 125 2.2 (Jy) Density Flux NGC1275 0.017 16623 1.5 NGC1808 0.003 207 3 HydraA 0.055 154 - - Source Redshift NGC1052 0.005NGC1167 1500 0.002 243 NGC3079 0.004 145 1.6 CygnusA 0.056 1400 10 NGC1365 0.006 191 2 NGC1068 0.004 1090 NGC2110NGC2639 0.007 0.040 175 54.5NGC4261 2.9 NGC4388 - 0.007 0.008 80 76 - 154 4.2 - 180 abs Table 1: Figure 1: were followed up in the 4.7-GHz transitions with Effelsberg telescope betwee AGN Tori Henkel et al. (priv. comm.) August 2004. of the two main lines6035-MHz at line. 6031 MHz and 6035 MHz at the systemic ve for single-dish spectroscopy, and so demandingtwo unachievably of high spe these we thusin proposed Cygnus an A interferometric and study.13.4 NGC GHz. We 1052 looked with The for the observations exc 357 VLBA, km/s were omitting per made Hydra with IF). A two Thechannels since IFs IFs per its of were IF, core yielding 16-MHz centred was abrated bandwidth too at spectral using (c w 13.434 standard GHz line phase resolution and and of 13.441for amplitude GHz, bandpass 1.4 calibration km/s calibration r procedure, of per using Cygnus channel. A, 2 and 0423-01 and 3C84 for NGC PoS(8thEVN)035 e opacity owing gas. . The image 2 -150 hich ranges up GC 3079 (Fig 1, were observed at esponding to the idth, suggest that erved blueshifted -100 ggest the presence -150 -50 the torus is expected 0.52) mas -100 0 × eyfert 2 galaxy 16 Mpc C 3079 and NGC 5793, km/s -50 C. M. Violette Impellizzeri the two transitions at the ource, with wide velocity rg telescope. We detected 50 90 km/s 0 tion in this source has been 90 km/s km/s 100 50 Overall Spectrum overall specrtum 150 CYG-A RA 19 59 28.35397360 DEC 40 44 02.1200000 CYG-A.SUM.7 CYG-A RA 19 59 28.35397360 DEC 40 44

100

0 30 20 10 -10 milliJy/beam -20 -30 -40 150

CYG-A RA 19 59 28.35386803 DEC 40 44 02.1200000 cyg.IF2.spec.SUM.1 CYG-A RA 19 59 28.35386803

0 60 40 20 milliJy/beam ght panel shows the absorption spectrum -20 -40 p peak at 0.453 Jy/beam. The panels show -150 -100 -50 0 4 km/s 50 100 2 pc 150

CYG-A RA 19 59 28.35399120 DEC 40 44 02.1199000 cyg.IF2.spec.SUM.1 CYG-A RA 19 59 28.35399120 DEC 40 44

0 60 40 20 milliJy/beam -20 -40 -150 -100 Relative R.A. (mas) VLBA 2 cm -50 0 km/s

50 Relative Declination (mas) Declination Relative 100 150

CYG-A RA 19 59 28.35409677 DEC 40 44 02.1198000 cyg.IF2.spec.SUM.1 CYG-A RA 19 59 28.35409677 DEC 40 44

0 50 40 30 20 10 milliJy/beam -10 -20 -30 -40 VLBA image of Cygnus A at 2 cm. The synthesized beam is (0.879 Of the originally selected 31 Seyfert 2 galaxies listed in Table 1, 27 sources The absorption spectrum in NGC 5793 also shows a very broad line width, w = 0.05. Two further lines corresponding to the two transitions were also obs τ a montage with selected OH absorption spectra. The bottom ri is contoured at -1.5, 1.5, 3, 6, 12, 24,integrated over 48, the 96 whole percent source. of the ma 3. Results 3.1 The Effelsberg survey 6 GHz and 20 sources were observedabsorption at at 4.7 6 GHz GHz with towards the five 100-mare sources. Effelsbe shown The in spectra Fig. of 1. two Absorptioncomponents of was detected them, and towards NG narrow the troughs centre of atleft each the s panel), systemic velocities the of absorption thetwo width two transitions is lines. (6031 800 MHz km/s, In and N withis 6035 two MHz) deeper at components the corr systemic velocity. The maximum lin relative to the systemicAlternatively, these velocity two troughs, by symmetric 100 around km/s, theof 6035-MHz indicating line, gas might the rotating su around presence aaway, of extend central to some source. 1.5 pc outfl The from the VLBIfound central jets to engine in [14]; come this the from 1.6-GHz source, nuclear absorp the a region 6-GHz S [15] absorption and was also in likelyto addition to be. to come No the from absorption broad the was velocity central observed region, w in where the 4.7-GHz transition. to 1000 km/s (Fig.1, right panel). Two narrow troughs, corresponding to Figure 2: AGN Tori PoS(8thEVN)035 ere visible earby galaxy five of the 27 rce, extending nge from a few ds the centre of al region, either The noise in the suming the pres- rce. We report a s not support the tate transitions at line of sight to the se previous studies that the new 6-GHz molecular detections. ible even after longer n, and again seems to etection rate of 19 %, rds the central region. .g. [20], [21]. ess of the radio source ossibility is that it may eature due to low-level -detections still need to based on X-ray column is surrounding the inner C. M. Violette Impellizzeri 90 km/s. The absorption the core. The profile is resolution IR observations 0.034, were observed. ∼ ities of peak absorption and rge columns of dust towards ∼ τ 5 = 0.125 with a line FWHM corresponding to τ The 2-cm continuum image of Cygnus A (Fig. 2) shows a compact radio sou We have detected rotationally-excited, broad OH lines in absorption towards We have found that in the five systems with detections the lines are strong and w We also report a tentative OH detection at 13.4 GHz towards the powerful, n AGN Tori systemic velocity and corresponding to a maximum line opacity of Both these sources show1.6 previously GHz [16], detected [17]. OH in absorption in the lower3.2 s Cygnus A east–west up to 4 pcmap from is the 5 core, mJy/beam. withtentative a Fig. detection peak 2 of flux shows the density the rotationally-excitedCygnus of spectra OH A. 453 for The mJy/beam. transition apparent different at optical positions 13.434 depthadjacent GHz derived at continuum from towar the the is ratios sou of intens profile towards the lobes isjets, suggestive that whereas part a of deeper thestrongest and when gas integrated is broader over diffuse the absorption and entireindicate profile area that containing is the continuum seen gas emissio is towards Further spread tests over are the needed whole to source,instrumental confirm effects with only this prevalence detectable result towa after and long to integration times. rule out a spurious f 4. Conclusions sources observed with thewhich 100-m is telescope in higher Effelsberg. thanmainly targeted the This red detection , yields where rates an a infraredthe achieved d excess line is in indicative of of previous la sight surveys. (e.g.densities. [18], Tho This [19]). is The the100 source km/s first selection to time in 2000 this km/s, our has suggestingrotating study that been was around the done. the gas central in Thedetections engine, all observed have sources or line is absorption infalling/outflowing. widths close in ra tohypothesis We the of the have radiative ground centr excitation found models state alone transition to explainHowever, at the given previous the 1.6 lack GHz. high of X-ray absorbing Thisbe columns explained. doe in Since our the systems, nature thebe of non non-molecular the in absorbing most material galaxies. is unknown, one p after short integration times, whereas inintegration the times. non-detections This no bimodal lines distribution wereence of of vis absorptions compact could clouds be crossing explained the as line of sight in a few sources. Cygnus A. 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