The Accretion Geometry of NGC 5548

Transcription

1 The Accretion Geometry of NGC 5548 Emma Gardner & Chris Done Durham University

2 Reverberation as a Tool for Investigating Accretion Geometries UV Disc Illuminates Clouds Clouds Re-emit Flux as Lines Czerny et al Mehdipour et al. 2015

3 Reverberation as a Tool for Investigating Accretion Geometries UV Disc Illuminates Clouds Clouds Re-emit Flux as Lines Czerny et al Kollatschny & Zetzl 2013

4 Reverberation as a Tool for Investigating Accretion Geometries Disc Re-emits Flux as Opt/UV Continuum X-ray Source Illuminates Disc UV-Opt X-rays Czerny et al Cameron et al. 2012

5 Reverberation in NGC 5548 Hard X-rays Soft X-rays UV Observed simultaneously by Swift and HST with <0.5 day sampling rate for approximately 120days Optical Edelson et al. 2015

6 Optical Reverberation in NGC 5548 Hard X-rays Soft X-rays UV Edelson et al. 2015

7 Longer than Expected Lags Standard Disc Prediction McHardy et al. 2014

8 Log v F(v) Reprocessing Model Log v

9 Log v F(v) Reprocessing Model Log v

10 Log v F(v) Gravitational Energy Released T Reprocessing Model Log v

11 Log v F(v) Reprocessing Model T increases Log v

12 Log v F(v) Reprocessing Model T increases Log v

13 Log v F(v) Reprocessing Model T increases Log v

14 Log v F(v) Reprocessing Model T increases Log v

15 Log v F(v) Reprocessing Model T increases Log v

16 Log v F(v) Reprocessing Model T increases Log v

17 Log v F(v) Reprocessing Model Illumination provides additional source of heating Log v

18 Log v F(v) Reprocessing Model Log v Effective temperature of annulus is the flux weighted sum of temperature from gravitational heating and temperature from X-ray heating

19 Log v F(v) Reprocessing Model Log v Effective temperature of annulus is the flux weighted sum of temperature from gravitational heating and temperature from X-ray heating

20 Log v F(v) Reprocessing Model V band Log v UV Effective temperature of annulus is the flux weighted sum of temperature from gravitational heating and temperature from X-ray heating

21 Log v F(v) Reprocessing Model Traditionally expected lags from standard disc: τ = R c T R 3/4 τ λ 4/3 λ max 1 T V band Log v UV

22 Log v F(v) Reprocessing Model Traditionally expected lags from standard disc: τ = R c T R 3/4 τ λ 4/3 λ max 1 T V band Log v UV Not true for a flared disc

23 Log v F(v) Reprocessing Model V band Log v UV For each radius: Gravitational flux Illuminating X-ray flux Response to fluctuations in illuminating continuum as a function of time TRANSFER FUNCTION

24 Disc Transfer Functions

25 Disc Transfer Functions Reprocessed lightcurve is a lagged and smoothed version of the illuminating lightcurve. (Smoothing timescale ~ lag timescale)

26 Log v F(v) Reprocessing Model V band Log v UV For each radius: Gravitational flux Illuminating X-ray flux Response to fluctuations in illuminating continuum as a function of time TRANSFER FUNCTION

27 NCG 5548 r out UVW1 2-10keV Hard X-rays r cor Model Parameters: M = a = 0 m = 0.04 i = 45 r out = 660R g Spectral Constraints: Γ = 1.6 vf UVW1 ~ 1.7 vf 10keV r cor = 70R g

28 UVW1 Spectrum Hard X-rays r cor = 70R g Flux vs Disc Radius Intrinsic Disc Emission Reprocessed Flux Light Curves CCF Observed Model Output

29 UVW1 Spectrum Hard X-rays r cor = 70R g Flux vs Disc Radius Amplitude of model UVW1 fluctuations too small Too much dilution by Reprocessed hot intrinsic Flux emission from inner disc Light Reprocessing Curves signal stronger CCF at larger radii disc must be truncated at large radius Intrinsic Disc Emission Observed Model Output

30 UVW1 Spectrum r cor = 300R g Hard X-rays Flux vs Disc Radius Intrinsic Disc Emission Reprocessed Flux Light Curves CCF Observed Model Output

31 UVW1 Spectrum r cor = 300R g Hard X-rays Flux vs Disc Radius Amplitude of model UVW1 fluctuations much better BUT Reprocessed Flux Too much high frequency power Light travel time not long enough Light Curves CCF to smear sufficiently keep reprocessed spectrum the same but try increasing radius at which it occurs Intrinsic Disc Emission Observed Model Output

32 r cor = 300R g Light Curves CCF 2 R Observed Model Output Light Curves CCF 4 R Observed Model Output

33 r cor = 300R g Light Curves CCF 2 R 4 R Producing sufficient light travel time smoothing requires the reprocessor to by 4x further away than if emission came Observed Model Output from standard disc BUT Light Curves CCF Resulting lags then too long UVW1 fluctuations still too correlated with hard X-rays Observed Model Output

34 Disc is NOT reprocessing hard X-ray emission (Colours show Observed and Model Output) Disc cannot see hard X-rays. Something is preventing the hard X-rays from directly illuminating the disc. Whatever this structure is, it is probably the source of illuminating flux.

35 Soft X-ray Excess: For once a solution rather than a problem! Mehdipour et al. 2015

36 Soft X-ray Excess: For once a solution rather than a problem! Mehdipour et al. 2015

37 Soft X-ray Excess: For once a solution rather than a problem! Mehdipour et al. 2015

38 Soft X-ray Excess: For once a solution rather than a problem! Mehdipour et al. 2015

39 Fast Light Travel Time Slow Dissipation Soft excess region (SXS) emission peaks in UV/FUV UV line driving lifts up material Hard X-rays overionise material so it falls back down Whole turbulent region prevents hard X-rays illuminating disc Instead hard X-rays illuminate inner edge of SXS Fluctuations dissipate outwards through SXS (slower than light travel time). UV from outer edge of SXS illuminates disc

40 UVW1 Standard Disc Reprocessing UV Emission V HST Spectrum Hard X-rays Light Curves CCF Observed Model Output

41 V band UVW1 Observed Model Output Observed Model Output Reprocessing HST UV emission gives a much better match to shape of observed UV/Optical lightcurves BUT If the disc is the reprocessor, UVW1 and V band lags are too similar, i.e. cannot produce V band lag that is 4x longer than UVW1

42 1 2d lag times require reprocessing at R g. Disc BBs produced at these radii are too cool to contribute significant flux to UVW1 or V bands, due to their large area. Illuminating UV Flux (HST band) UVW1 V band V band wrt HST HST wrt HST UVW1 wrt HST Edelson et al τ = 0. 5d R rep = 270R g + R HST τ = 2d R rep = 1080R g +R HST To heat a reprocessor at these large radii enough to emit in UV/optical bands requires the reprocessor has a SMALL AREA.

43 Czerny et al. 2015

44 Hard X-rays Soft X-rays FUV UV Constant Optical Continuum Reverberating Optical Continuum Reverberating Optical Lines Proposed Geometry for NGC 5548 IR

45 Summary Optical lightcurves consistent with reprocessing UV not hard X-rays Soft excess component good candidate for obscuring hard X-rays and providing illumination Long lags imply reprocessor at large radii Disc cannot be this reprocessor, since disc annuli at large radii have large area so are too cool to significantly contribute to UV/optical bands Need small area reprocessor at large radii, implying reprocessors are optically thick BLR clouds