NGC 3147: a 'true' type 2 Seyfert galaxy without the broad-line region THE X-RAY UNIVERSE Granada, May 28 th 2008 Stefano Bianchi A. Corral 1, F. Panessa 1,2, X. Barcons 1, G. Matt 3, L. Bassani 4, F.J. Carrera 1, E. Jiménez-Bailón 5, F. La Franca 3, N. Sacchi 3 1 Instituto de Física de Cantabria (CSIC-UC) - Santander (Spain) ‏ 2 INAF-IASF - Roma (Italy) ‏ 3 Università degli Studi di Roma TRE - Roma (Italy) ‏ 4 INAF-IASF - Bologna (Italy) ‏ 5 Universidad Nacional Autónoma de México, Mexico DF (Mexico) ‏

BLR Narrow Lines No broad lines Type2 AGN: The Unification Model view NLR BLR Torus Optical

BLR Type2 AGN: The Unification Model view NLR BLR Torus Absorber C-thin C-thick X-rays X-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 observations In some cases, the classifications in the two bands do not match the expectations of Unified 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. Risaliti et al. (2007) ‏ Matt et al. (2003) ‏

The Sample 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 candidates 2 sources were observed 1 will be observed this year SourceXMM-NewtonOptical observation NGC 3147 Oct. 6 th 2006 Oct. 4 th,5 th,9 th 2006 (OSN) IC 1631 Nov. 23 th 2006 Dec. 1 st 2006 (ESO) IRAS AO7Tbd Mrk 273x ?? NGC 4698 ??

NGC3147 is absorbed by a very low local column density. N H < 5x10 20 cm -2 (99% for two parameters) ‏ NGC 3147 z=0.009 The 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  EW: ~130 eV - X-ray/IR/[OIII] flux diagrams Adapted from Panessa & Bassani (2002) ‏

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

The X-ray spectrum of NGC3147 is that of a typical type 1 AGN -No absorption -  ~1.6 -Iron K  EW~130 eV -a ox ~ 1.33 The SIMULTANEOUS optical spectrum confirms the lack of broad permitted lines! The very low column density measured in the X-rays (N H < 5x10 20 cm -2 ) corresponds to A V <0.3, at odds with the large amount of dust required to obscure the BLR NGC3147 intrinsically lacks the BLR! The BLR may disappear at very low bolometric luminosities (Elitzur & Shlosman 2006) ‏ The bolometric luminosity of NGC3147 is about 5x10 42 erg s -1, larger than the 'threshold' calculated in this scenario Moreover, in this case the lack of the BLR would imply the lack of the torus Low luminosity Below a minimum accretion rate, the BLR cannot form (Nicastro 2000) ‏ The Eddington ratio of NGC3147 ranges between 8x10 -5 and 2x10 -4, well below the 'threshold' proposed in this scenario Low accretion rate

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: F 2-10kev < 1.0x cgs The very low flux ratio F x /F [OIII] ~ 0.05 suggests that IC1631 is a Compton-thick AGN or a starburst In any case, it cannot be considered an unabsorbed Seyfert 2 candidate any more! IC 1631 z=0.031 The XMM-Newton spectrum has a very low flux: F 2-10kev =(2.8±1.1)x cgs and a very low luminosity: L 2-10kev =(6.2±2.4)x10 40 cgs

IC 1631 z=0.031 Adapted from Panessa & Bassani (2002) ‏ The optical lines' ratios points to a starburst classification

Conclusions The X-ray spectrum of NGC3147 is that of a typical type 1 AGN (N H < 5x10 20 cm -2 ) ‏ The simultaneous optical spectrum excludes the presence of broad components for H  and H  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 BLR IC1631 is a starburst galaxy and must therefore be removed from the list of 'unabsorbed Seyfert 2' candidates The key to find genuine 'unabsorbed Seyfert 2s' is represented by SIMULTANEOUS X-ray and optical observations Bianchi et al., 2008, MNRAS 385, 195 See also Francesca Panessa’s poster!