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GISELLA DE ROSATHE OHIO STATE UNIVERSITY
ON BEHALF OF THE AGN-STORM COLLABORATION
Probing AGN Structure on Microarcsecond Scales:
The Space Telescope and Optical Reverberation Mapping Program
Hubble 25 – April, 21st, 2015
AGN STORMTROOPERS (incomplete...) 2
P. Arevalo, A.J. Barth, V.N. Bennert, M.C. Bentz, A. Bigley, M. Bottorff, T.A. Boroson, W.N. Brandt, A.A. Breeveld, M. Brotherton, B.J. Brewer,
E. Cackett, M. Carini, L. Carrasco, S. Chul, K. Clubb, J. Comerford, E.M. Corsini, D.M. Crenshaw, S. Croft, E. Dalla Bontà, A. Deason, A. De Lorenzo-Caceres,
K. D. Denney, G. De Rosa, M. Dietrich, T. Dwelly, R. Edelson, S. Eftekharzadeh, J. Ely, M. Eracleous, P.A. Evans, M.M. Fausnaugh, A.V. Filippenko, O. Fox, N. Gehrels,
J.M. Gelbord, M.R. Goad, C.J. V. Gorjian, M. Graham, J.E. Greene, C.J. Grier, D. Grupe, J. Gutierrez,P.B. Hall, E. Holmbeck, K. Horne, M. Im, C. Johnson, M. Joner, J.
Kaastra, S. Kaspi, B.C. Kelly, P. Kelly, J.A. Kennea, M. Kim, C.S. Kochanek, K.T. Korista, G.A. Kriss, D. Laney, M.W. Lau, J.C. Lee, D. Leonard, P. Lira,
M. Lundquist, S. Mathur, J. Mauderhan, J. McCormac, R. McGurk, I.M. McHardy, N. Milgram, L. Morelli, F. Muller Sanchez, H. Netzer,M. Nguyen, J. Nousek, P. Ochner,
A. Pancoast, I. Papadakis, L. Pei, B.M. Peterson, A. Pizzella, R.W. Pogge, J.-U. Pott, F. Pozo Nunez, X. Prochaska, G. Rude, D. Sand, J.S. Schimoia, K. Schnulle,
S.G. Sergeev, B. Shappee, I. Shivvers, M. Siegel, A. Siviero, D. Starkey, K. Steenbrugge, M. Strauss, A,-L. Sun, H.I. Sung, M. Tejos, T. Treu, B. Tucker, P. Uttley, S. Vaughan,
M. Vestergaard, L. Vican, C. Villforth, W.F. Welsh, J.-H. Woo, H. Yan, H. Yuk, S. Young, N. Zakamska, W. Zheng, Y. Zu
Hubble 25 – April, 21st, 2015
Outline3
Studying AGN using reverberation mapping
AGN STORM: program details
AGN STORM: early results
Reverberation mapping with HST, the future
Hubble 25 – April, 21st, 2015
AGN structure4
Hubble 25 – April, 21st, 2015
Urry & Padovani, 1995
NGC 5548
Rest wavelength (Å)
f l (1
0-1
3 e
rg c
m-2 s
-1 Å
-1)
BLR
NLR
DISK
Problem: microarcsecond resolution needed to study the details of the inner structure (e.g. size, dynamics)
Figure courtesy of L. Pei
Reverberation mapping: time vs spatial resolution
The continuum luminosity varies stochastically in time
The gas responsible for the broad line emission is ionized by the AGN continuum and “responds” to variations in the continuum luminosity on a time scale
t = RBLR / c
We can estimate the distance of the gas from the timescale for response.
5
t2= t1+ t = t1+RBLR/c
RBLR
Accretion disk
Broad line gas
Hubble 25 – April, 21st, 2015
Observer
Reverberation mapping: estimating t6
t t t
Continuum
CROSS CORRELATION
Lya line
Hubble 25 – April, 21st, 2015
De Rosa+ 2015
Reverberation mapping: MBH estimate
MBH= f RBLR Dv2 G-1
Virial Product
RBLR from RM delay estimate
Dv from width of the varying part of the emission line
Calibration of <f> through MBH-s*
7
Hubble 25 – April, 21st, 2015
Quiescent galaxyAGN, new dataAGN
Grier+2013
Reverberation mapping: R-L relation8
Radius of the emitting region increases with a power of the ionizing continuum luminosity
Single Epoch Mass Estimates: MBH ∝ Dv2 RBLR
line width2 Llg
All relations are anchored to the RM MBH
RM is not only vital to estimate MBH in the local universe, but also in distant sources
Hubble 25 – April, 21st, 2015
9
Observer
v1
v2
v3 t1 < t2 < t3
Reverberation mapping: resolving in t and vLOS
Hubble 25 – April, 21st, 2015
Required time sampling, duration, and S/N makes velocity-delay map recovery very difficult.
Reverberation mapping: status before AGN STORM
10
Reverberation lags measured for ~50 AGNs, mostly Hβ
AGNs with lags for multiple lines: highest ionization emission lines respond most rapidly ionization stratification
Handful of optical datasets good enough to probe BLR structure/kinematics. Balmer lines: flattened geometries, combination of virialized motion and infalling gas
Little known about high-ionization lines (IUE, HST-FOS). Estimated lags but limited information about detailed response (few orbits, low S/N)
Hubble 25 – April, 21st, 2015
11
AGN STORM: program
AGN STORM program
12
Multiwavelength reverberation mapping monitoring program to study the Seyfert 1 galaxy NGC 5548,
2014 January - August
NIR-MIR:photometry
ground based, Spitzer
Optical: ground based
spectroscopy &
photometrydaily
X-Ray:Chandra, SWIFT
Optical-NUV:
photometrySWIFT
3 times per day
FUV: HST
once per day171 orbits
AGN STORM
Hubble 25 – April, 21st, 2015
AGN STORM: scientific goals
13
Structure and kinematics of the high-ionization BLR with HST COS Ly α λ1215, C IV λ1549, Si IV λ1400, NV λ1240, He II λ1640
Simultaneous ground-based optical spectroscopy programBalmer lines, He II λ4686
Accretion disk structure with HST, Swift, and ground-based data (X-rays to mid-IR)
Physical structure of emitting gas Dynamical processes at microarcsec scales
Uncertainties in MBH based on RM measurementsHubble 25 – April, 21st, 2015
AGN STORM: HST program
14
Daily observations with Cosmic Origins Spectrograph:
Each visit: G130M and G160M exposures in single orbit (~1100-1750 Å )
179 visits (2014 February 1 to July 27) 8 unsuccessful visits (e.g., safing events)
Customized data reduction pipeline developed: Precision of flux calibration better than 1.5% locally Wavelength calibration precise to < 6 km s−1
Hubble 25 – April, 21st, 2015
15
AGN STORM: early results
AGN STORM HST program
Mean lags relative to 1367 Å continuum
16
Hubble 25 – April, 21st, 2015 De Rosa+ 2015
Preliminary analysisCIV emission line
Strong velocity dependence of lags
Higher velocity gas responds most rapidly
First half: larger variations, shorter lags
Second half: smaller variations, longer lags
17
Hubble 25 – April, 21st, 2015 De Rosa+ 2015
Preliminary analysisLya emission line
Strong velocity dependence of lags
Situation complicated by strong absorption systems
First half: larger variations, shorter lags
Second half: smaller variations, longer lags
18
Hubble 25 – April, 21st, 2015 De Rosa+ 2015
AGN STORMHST program
challenges
Broad UV absorption gradually disappearing during the campaign
Analysis of absorption features ongoing ( Kriss+ in prep )
19
Hubble 25 – April, 21st, 2015
Figure courtesy of G. Kriss
AGN STORMHST program
challenges
Line variations are not simple continuum echoes
Superb data, challenge to model in detail
Velocity delay map analysis ongoing
(Horne+ in prep; Pancoast+ in prep)
20
Hubble 25 – April, 21st, 2015
Figure courtesy of K. Horne
Continuum
CIV
AGN STORM HST & optical
spectroscopy
Mean lags relative to UV and optical continua
21
Pei+ in prep
Hubble 25 – April, 21st, 2015
AGN STORM: HST & optical spectroscopy
22
topt >> tUV RBLR measured from optical data alone is systematically lower than true RBLR
Not a problem for statistical MBH calibrated via M-s relationship as long as UV/opt continuum lag does not scale strongly with L or M (systematics simply subsumed into f)
More simultaneous optical/UV monitoring programs needed to determine continuum lag to determine possible dependence on L or M
Hubble 25 – April, 21st, 2015
Swift UVOT - Feb to June 2014
12 hour cadence ~280 epochs
23
AGN STORM: HST & NUV-optical photometry
Ground based – 16 observatories
> 600 epochs in V
Edelson+ 2015
Hubble 25 – April, 21st, 2015 Fausnaugh+ in prep
HST & NUV-optical photometry
Some tension with irradiated thin disk model
Disk structure larger than expected for a standard thin disk (Edelson+2015, Fausnaugh+ in prep)
Optical lags are comparable to, or greater than, He II lags. Emission regions are of similar physical size
24
Hubble 25 – April, 21st, 2015
Fausnaugh+ in prep
Edelson+ 2015
AGN STORM: summary
25
Successfully acquired 171 UV spectra of NGC 5548 with HST COS.
Emission-line lags range from ~2.5 days for He II λ1640 t0 ~6 days for Lyα λ1215.
Both Lyα and C IV lags show velocity-dependence: the data set has information on BLR kinematics.
Lag of a few days between UV and optical continuum light curves: implications for RBLR and virial factor.
Accretion disk: tension with thin disk model. Similar physical size than emission regions.
Hubble 25 – April, 21st, 2015
AGN STORM: publication plan 26
I: HST-COS dataset – accepted
II: Swift-HST RM of the accretion disk - accepted
III: Continuum interband lags HST-SWIFT-Ground based ~ submission IV: Optical emission line variations ~ submission
V: Velocity delay maps - ongoing
VI: Modeling of accretion disk structure - ongoing
VII: Direct modeling of spectra - ongoing
VIII: Absorption line variations - ongoing
IX: Dynamical modeling - ongoing
X: Spectral energy distribution analysisXI: Photoionization modelingXII: NIR observationsXIII: Wrap up
Hubble 25 – April, 21st, 2015
AGN STORM: a look into the (near) future
27
Hubble 25 – April, 21st, 2015
The AGN-STORM program shows that:
• RM with HST-COS is feasible (schedule/instrument) and successful
• UV coverage is needed when absolute size of BLR matters (e.g. dynamical modeling)
• Unexpected results – need to test uniqueness
We have ~5 years to observe more sources:AGN ID tCIV lt-days
NGC 3783 ~4, 2
Fairall 9 ~14
3C390.3 ~30, 6
NGC 7469 ~3, 5
NGC 4151 ~3.5, 3
NGC 4593 ~0.1, 1.5
28
Backup
STScI – August, 14th, 2014
Ground base observability vs z29
Figure courtesy of Sarah Gallagher
Reverberation mapping: geometry and kinematics
30
Observer
1
2
3
Toy model, stationary clouds
τ=r/c All points on an “isodelay surface” have the same extra light-travel time to the observer, relative to photons from the continuum source.
t1 < t2 < t3Shell: emission-line gas
Hubble 25 – April, 21st, 2015
AGN STORM: continuum variations31
Typical precision < 1.5%
Hubble 25 – April, 21st, 2015
Reverberation Mapping: assumptions32
Continuum originates in a single central sourceMBH=107-108 Msun , accretion disk size=1013-14 cm – BLR size ~1016 cm
Light travel is the most important time scaleEmission line gas responds instantaneously (trec ~ 40)
RM experiments carried out on time scales shorter than BLR dynamical time (3-5 years)
Simple (though not necessarily linear) relation between observed continuum (optical/UV) and the ionizing continuum (FUV)
Hubble 25 – April, 21st, 2015
Reverberation Mapping: simplified approach
33
Under these assumptions, velocity independent transfer equation:
However, most of the past data sets were inadequate for transfer function solution, so simpler analyses were used: e.g. Cross Correlation Function Analysis
Line light curve
Continuum light curve
TransferFunction
Lag estimates34
Mean response time (“lag”) obtained from cross-correlation function:
Figure courtesy of B. Peterson
Emission line width
Measure line widths from the rms residual spectrum:
Captures the velocity dispersion of the gas that is “reverberating”.
Non varying features disappear.
35
De Rosa et al., in prep
DvLOS
A virialized BLR36
For all the sources for which it is has been testable (multiple emission line):
Suggesting that gravity is indeed the principal dynamical force in the BLR
DV ∝ RBLR-1/2
Peterson & Wandel, 2002
MBH cross-check37
Comparison between direct methods(MBH in units of 106 Msun)
Galaxy NGC 4258 NGC 3227 NGC 4151
Megamasers 38.2±0.1 N/A N/A
Stellar dynamics 33±2 7-20 47+11-14
Gas dynamics 25-260 20+10-4 30+7.5
-22
Reverberation mapping
N/A 7±1 26.5±1.5
New
AGN12 AGN12
MBH estimate
MBH= f RBLR Dv2 G-1
Virial Product
Observable
f is our ignorance factor: everything we do not know about BLR geometry and inclination
Putting everything together Calibration of <f> through MBH-s*
38
Grier et al., 2013
Quiescent galaxyAGN, new dataAGN
Hb RBLR-L AGN Relationship
Simple ionization argument:
To first order, all AGN spectra look the
same (Davidson 1972):
After a carful subtraction of the host-galaxy light:
R ∝ LBLR0.5
39
Bentz et al., 2013
AGN-STORM: Why 180 HST orbits?
40
1. Assume geometry & kinematics: inclined keplerian disk with two-armed spiral wave
2. Simulate continuum variation assuming dumped random walk
3. Create velocity delay maps for different lines (photoionization grid)
4. Create realistic mock spectra5. Create recovered velocity delay maps6. Play with free parameters: length of the
campaign & time resolution
Velocity delay map: edge-on ring41
rϑ
Rotating clockwise, Vorb
Observer
Line-of-sight velocity V (km/s)
2 r/c
r/c
Vorb-Vorb
Time delay τ
V=Vorb sinϑ
τ=(1+cosϑ)r/c
Circular orbit projects to an ellipse in the (V, τ) plane.
Velocity delay map: thick geometries 42
Generalization to a disk (multiple rings) or thick shell (multiple inclination) is trivial.
Observer
LOS V (km/s)
2 rout/c
Vout-Vout
τ
rout/c
-Vin Vin
2 rin/c
rin/c
Observer
Reverberation Mapping: full approach43
Under same assumptions as before:
Velocity resolved line light curve
Continuum light curve
Velocity delay map
Well-defined inversion problem dependent only on the quality of the data.
First recovered velocity-delay map ARP 151: Bentz et al. 2010
Problems: S/N, duration and time sampling requirements make the recovery of velocity delay maps difficult
AGN-STORM: program elements
44Spectroscopy UV 2.5m Hubble Space Telescope + COSOptical MDM 1.3m Telescope, Kitt Peak ARC 3.5m Telescope, Apache Point Asiago 1.22m Telescope, Asiago, Italy CrAO 2.6m Shajn Telescope, Crimea Lick 3m Shane Telescope, Mt. Hamilton, Calif
ornia 2.5m Nordic Optical Telescope + Spectrograp
h, La Palma, Canaries WIRO 2.3m Telescope, Wyoming 2m Liverpool Telescope with Frodospec spect
rograph, La Palma, Canaries
PhotometryX-Ray Chandra ACIS-S/LETG Swift X-Ray TelescopeUV Swift 0.3m UVOT (UV/Optical) Telescope
Optical 2m Liverpool Telescope with Imager, La Palma, Canari
es Bohyunsan Optical Astronomy Observatory 1.8m Teles
cope, Mt. Bohyun, South Korea
CrAO 0.7m AZT-8 Telescope, Crimea, Ukraine CrAO 1.3m AZT-11 Telescope, Crimea, Ukraine (operat
ed by WKU) Fountainwood Observatory, Georgetown, Texas (SU) LOAO 1-m Telescope, Mt. Lemmon Arizona (operated
by KASI) Hard Labor Creek Observatory 0.5m Telescope, Rutle
dge GA (GSU) 1.3m RCT Telescope, Kitt Peak Arizona (operated by
WKU) Wise Observatory C18 Telescope, Mitzpe Ramon, Israe
l Bell Observatory 0.6m Telescope, Western Kentucky U
niversity West Mountain Observatory 0.91m Telescope, West M
ountain Utah (BYU) ESO 2.2m Telescope,LaSilla, Chile LCOGT 1-meter Telescope Maidanak Observatory 1.5m Telescope, Uzbekistan Mount Laguna Observatory 1m Telescope, California Swift 0.3m UVOT (UV/Optical) Telescope ASASSN
Near Infrared ESO 2.2m Telescope,LaSilla, Chile Infrared Imaging System 0.8m Telescope, Cerro Arma
zones, Chile 2m Liverpool Telescope with Imager, La Palma, Canari
es Guillermo Haro Observatory, Sonora, Mexico (INOAE) Spitzer Space Telescope, IRAC imager
Velocity binned time lags45
Hubble 25 – April, 21st, 2015
46
Wavelength solution
Offsets in Standard Pipeline Products
• Wavelength offsets are seen between • different CENWAVES• COS and STIS datasets
• Offsets are consistent: data shown is 170 orbits combined for each setting.
47
Correcting with STIS48
• Identify IGM features present in COS and STIS spectra
• Cross-correlate lines from each observation with the STIS dataset
• Compute a linear offset to the dispersion and apply
Improved Alignment49
50
Lowered RMS
51
Fixed pattern noiseRaise your hand if you see any potential sources of fixed-pattern noise.
Improving S/N with P-flats52
170 orbits (21 hours of G130M and 57 hours of G160M)1291 and 1327 at 4 FPPOS1600 at 2 FPPOS1623 at 1 FPPOS
Wide range of parameter space:Broad settings with maximum FPPOS contributionNarrow settings with minimal FPPOS contribution
Improving S/N with P-flats53
Prominent Effect on narrow modes with few FPPOS
Narrow profile keeps fixed-pattern features sharp
Few FPPOS lets fixed-pattern noise patterns repeat
Improving S/N with P-flats54
Prominent Effect on narrow modes with few FPPOS
Narrow profile keeps fixed-pattern features sharp
Few FPPOS lets fixed-pattern noise patterns repeat
Improving S/N with P-flats55
Much smaller, though still evident effect on wider modes with many FPPOS
G130M modes intrinsically average over more detector area
More FPPOS diminishes the effect of fixed-pattern features
S/N Limits56
57
Static sensitivity functions
Residuals at lifetime position 2: WD 0308-56558
Residuals at lifetime position 2: WD 1057+71959
AGN-STORM: Static sensitivity functions
60
WD 0308-565 G130M, WD 1057+719 G160M
Model each CENWAVE/FPPOS setting individually
Low order Chebyshev polynomial FUVA
Spline function FUVB
Mask absorption lines and bad pixels
Residuals at lifetime position 2: G130M standard pipeline
61
62
Residuals at lifetime position 2: G130M AGN-STORM pipeline
63
Residuals at lifetime position 2: G160M standard pipeline
64
Residuals at lifetime position 2: G160M AGN-STORM pipeline
65
Time dependent sensitivity
66
WD 0308-565, time evolution of the residuals
AGN-STORM: Time dependent sensitivity
67
1. Redefined wavelength ranges
2. Added additional break point
3. Computed correction from individual CENWAVE settings
68
TDS residuals: Standard pipeline
3 1
2
69
TDS residuals: AGN-STORM pipeline
3 1
2
70
TDS residuals: Time evolution of the distribution
71
TDS residuals: RMS
Summary72
Improved wavelength calibration by cross-correlating onto the STIS wavelength scale.
Increased S/N by applying pixel-to-pixel flatfields.
Improved static sensitivity function by modeling individual CENWAVE/FPPOS settings.
Improved TDS correction with a) Revised wavelength ranges b) Additional breakpoint c) Compute correction from individual CENWAVEs
= Needs
validation = Needs code
dev/testing = More
complicated
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