An XMM-Newton view of Q2122-444:

an AGN without Broad Line Region?

Mario Gliozzi (GMU)L. Foschini (IASF Bo) R. Sambruna

(GSFC) L. Kedziora-Chudczer (Sidney)

* Type I and Type II AGN Unification Model HBLR vs non-HBLR * X-ray advantage * “Naked” AGN

* X-ray (XMM+Chandra) view of Q2122-444

Optical View:

[Fig. from Hawkins 2004]

Type I AGN:

Type II AGN:

Broad permitted lines

Narrow forbidden & permitted lines

Q2130-431

Q2125-431

Q2130-431

Q2125-431

Strong & variable continuum

Weak & constant continuum

Unification Model

Basic Ingredients mass *Supermassive BH*Accretion disk + corona*BLR: high velocity, high density gas on pc scales*NLR; lower velocity, lower density gas on kpc scales*Torus: gaseous & molecular absorbing medium in equatorial plane embedding BH, ADC, BLR*Jets: relativistic ejection (10% AGN)

AGN intrinsically the same:

Differences ascribed to viewing angle:

Type I Type II

Spectropolarimetry

Measure of polarization of light as a function of wavelengths

Instrumental in the development of Unification Model: Detection of broad permitted lines in polarized light in Sy2 NGC 1068(Miller & Antonucci 1983) :

* presence of hidden BLR (HBLR)

* constraints on location and geometry of the absorber

But exceptions exist: *Only 50% of Sy2 have HBLR (e.g. Tran 2001) based on 3-m (Lick) and 5-m (Palomar) telescopes

* Result confirmed by Keck 10-m telescope (Moran et al. 2007)

non-HBLR vs. HBLR

Study of HBLR and non-HBLR based on Lradio L[O III] or IR colors:

a) Intrinsically different:

L(HBLR) > L(non-HBLR) (e.g. Moran et al. 1992; Tran 2001)

b) Not different :

biased results, affected by dilution effects from host galaxy (e.g. Lumsden et al. 2001; Lumsden & Alexander 2001)

Unified Model explains observations, not physical origin of ingredientsExceptions important not to disprove the model but gain insights intolinks among AGN ingredients

X-ray Advantage

X-ray produced & reprocessed close to BH:Best diagnostics for central engine

(Hard) X-rays less affected by absorption: Direct estimate of NH

No diluting effects from host galaxy

But not exhaustive: Need to complement information with other wavelengths

X-ray view: HBLR vs. non-HBLR

a) non-HBLR intrinsically differentExistence of a threshold Lx=3 1042erg/s (Eddington ratio=10-3) : Below threshold: non-HBLR Above threshold: HBLR Sample: objects from Tran with archival Chandra, XMM, ASCA, or SAX data(Nicastro et al. 2003) Nicely fit theoretical model (Nicastro et al. 2000)

b) non-HBLR more heavily absorbed Sample: 4 “best” candidates from Tran sample (no BL, high S/N, low optical extinction) Chandra observations 10 ks (Gosh et al. 2007)

Limits of spectropolarimetry studies:* require very high S/N (limited nearby objects)* rely on existence of appropriately placed scattering region

Naked AGN: Discovery

Based on large scale optical monitoring program over 25 yearsfrom UK 1.2m Schmidt telescope in Australia.Initial sample: 1500 AGN candidates Intermediate sample: 129 Seyfert-like objects (high S/N, z<0.5) Final sample: 55 Seyfert 2 galaxies(Hawkins 2004)

Selection based on spectral & temporal variability properties:

*Spectrum ensures (apparent) lack of BLR

*Variability ensures direct view of central engine (and jet?)

6 naked AGN (spectrally type II, but variable as type I) detected

Naked AGN: Optical Classification

Seyfert 1

Seyfert 2

starburst

Type I AGN : FWHM > 1500 km/s, [OIII]/Hβ < 3, ∂B > 0.5

Type II AGN : FWHM < 1500 km/s, [OIII]/Hβ > 3, ∂B < 0.5

(Hawkins 2004)

(∂B=Bmax-Bmin)

Naked AGN: Optical Classification

Seyfert 1

Seyfert 2

starburst

Type I AGN : FWHM > 1500 km/s, [OIII]/Hβ < 3, ∂B > 0.5

Type II AGN : FWHM < 1500 km/s, [OIII]/Hβ > 3, ∂B < 0.5

Naked AGN : FWHM < 1500 km/s, [OIII]/Hβ > 3, ∂B > 0.5

Note : NLS1 ruled out by [OIII]/Hβ < 3, but not blazars

(Hawkins 2004)

X-ray Observations of Q2122-444

Goal: investigate nature of source*Constrain NH*Jet role?

Q2122-444: z=0.311, Hβ FWHM = 350 km/s, [OIII]/Hβ =6, ∂B = 0.9

Chandra observations: Date: December 2005Exposure: 4ks (part of snapshot survey)Instrument: ACIS-S(Gliozzi et al. 2007)

XMM observations: Date: November 2007Exposure: 40ks (pointed observation)Instruments: EPIC pn, MOS1, MOS2; OM

X-ray Imaging of Q2122-444

* Source easily detected: bright X-ray source

* Point-like appearance (consistent with ACIS PSF)

* No nearby sources within 1’

Unusual optical properties not due to source confusion.

Only 1 source in XMM extraction region.

X-ray Imaging of Q2122-444

* Source easily detected: bright X-ray source

* Point-like appearance (consistent with ACIS PSF)

* No nearby sources within 1’

Unusual optical properties not due to source confusion.

Only 1 source in XMM extraction region.

X-ray Spectrum of Q2122-444 Chandra:

XMM-Newton:

Spectra well fitted with simple absorbed PL.

Low NH suggests direct view of central engine.

X-ray Variability of Q2122-444

Short timescales: No significant flux nor spectral variability

Long timescales spectral variability

HR(Chandra) = -0.57(13)

HR(XMM) = -0.25(3)

where HR=(h-s)/(h+s)

Long timescales flux variability:

L0.5-8keV(Chandra) = 3.2 1043 erg/s

L0.5-8keV(XMM) = 1.4 1043 erg/s

The luminosity decreases by a factor of 2, and the spectrum hardens.

Broadband Properties of Q2122-444

Optical UV from the OM:

* mB=21.0(4), mU=20.1(2), mUVW1=20.0(2)

* Extinction fully consistent with NH

* Broadband spectral index αOX=1.30(6)

Radio from ATCA: (2.7 hr observations at 4.8 and 8.6

GHz)

* Source not detected

* Low radio loudness: RO <5, RX <10-4

Q2122-444: Summary

* The source is bright: Lx > 1043 erg/s (Eddington ratio = 10-2)

* X-ray spectral properties (Г and NH) typical of Seyfert 1 galaxies

* X-ray spectral variability properties (soft when bright) typical of Seyfert 1 galaxies

* Broadband properties (αOX and AV) confirm this scenario

* Low radio upper-limit rules out important contribution from putative jet

Q2122-444: Conclusions

Q2122-444 apparently lacks BLR but brighter than non-HBLR

Important to expand this work (enlarge sample, E band):

1) Representative of a large AGN class: -high detection rate from original sample -sizable fraction of narrow-lined AGN at Lx~1043 erg/s (Steffen et al. 2003)

2) May help shedding light on the origin of BLR and link with absorbing medium (e.g. clumpy torus model Nenkova et al. 2002)