an xmm-newton view of q2122-444: an agn without broad line region?
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
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)