NGC 3147: a 'true' type 2 Seyfert galaxywithout the broad-line regionTHE X-RAY UNIVERSE 2008- Granada, May 28th 2008A. Corral1, F. Panessa1,2, X. Barcons1, G. Matt3,L. Bassani4, F.J. Carrera1, E. Jimnez-Bailn5,F. La Franca3, N. Sacchi3

1Instituto de Fsica de Cantabria (CSIC-UC) - Santander (Spain)2INAF-IASF - Roma (Italy)3Universit degli Studi di Roma TRE - Roma (Italy)4INAF-IASF - Bologna (Italy)5Universidad Nacional Autnoma de Mxico, Mexico DF (Mexico)

BLRType2 AGN:The Unification Model viewNLRBLRTorusOptical

BLRType2 AGN:The Unification Model viewNLRBLRTorusX-raysX-rays and optical classifications generally agree: large amounts of X-ray absorption are measured in Seyfert 2s

The key to find genuine 'unabsorbed Seyfert 2s' is represented by SIMULTANEOUS X-ray and optical observationsIn some cases, the classifications in the two bands do not match the expectations ofUnified Models.

However, this mismatch is often due to the fact that the observations in the two bands are not simultaneous and catch the source in different states. These 'changing-look' AGN may be explained by a 'switching-off' of the nucleus or by a variable column density of the absorber.

We selected a conservative subsample of 5 sources,taken from Panessa & Bassani (2002).It includes optical Seyfert 2 galaxies without X-ray absorption and excluding Compton-thick candidates2 sources were observed1 will be observed this year

SourceXMM-NewtonOptical observationNGC 3147 Oct. 6th 2006Oct. 4th,5th,9th 2006 (OSN)IC 1631Nov. 23th 2006Dec. 1st 2006 (ESO)IRAS 01428-0404AO7TbdMrk 273x??NGC 4698??

NGC3147 is absorbed by a very low local column density.

NH< 5x1020 cm-2(99% for two parameters)NGC 3147z=0.009The pn and MOS spectra are well fitted by a powerlaw (~1.6) absorbed by the Galactic column density, plus a neutral iron K line (EW~130 eV)

NGC3147 is NOT Compton-thick:

- Neutral iron Ka EW: ~130 eV- X-ray/IR/[OIII] flux diagrams

NO BROAD Ha or Hb!The flux of any broad component of the Ha would be at most 5% of the total Ha fluxThe lack of broad optical lines in NGC3147 is an intrinsic property of the source and not an artefact of low S/NNGC3147: Optical spectrum

The X-ray spectrum of NGC3147 is that of a typical type 1 AGN

-No absorption-G~1.6-Iron Ka EW~130 eV-aox ~ 1.33The SIMULTANEOUS optical spectrum confirms the lack of broad permitted lines!

The very low column density measured in the X-rays (NH< 5x1020 cm-2) corresponds to AV

The previous (and only) X-ray observation was performed by GINGA and was likely contaminated by Abell 2877(Awaki 1993)

Its flux was to be considered an upper limit:

F2-10kev< 1.0x10-11 cgsThe very low flux ratioFx/F[OIII] ~ 0.05suggests that IC1631 is a Compton-thick AGN or a starburst

In any case, it cannot be considered an unabsorbed Seyfert 2candidate any more!IC 1631z=0.031

IC 1631z=0.031The optical lines' ratios points to a starburst classification

ConclusionsThe X-ray spectrum of NGC3147 is that of a typical type 1 AGN(NH< 5x1020 cm-2)The simultaneous optical spectrum excludes the presence of broad components for Ha and Hb

The key parameter for the observational properties of this source cannot be orientation, but an intrinsic feature (be it low accretion rate or luminosity), which prevents the BLR from forming.NGC3147 is the first 'true' type 2 Seyfert galaxy without the BLRIC1631 is a starburst galaxy and must therefore be removed from the list of 'unabsorbed Seyfert 2' candidatesThe key to find genuine 'unabsorbed Seyfert 2s' is represented by SIMULTANEOUS X-ray and optical observationsBianchi et al., 2008, MNRAS 385, 195See alsoFrancesca Panessasposter!

************