characterization of agn variability in the optical and ... · characterization of agn variability...
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PA U L A S Á N C H E Z
P A U L I N A L I R A R E G I S C A R T I E R
Characterization of AGN Variability in the Optical and Near Infrared
regimes
06-28-2016 AGN: what’s in a name - Garching
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AGN VARIABILITY
• Which is the mechanism responsible for AGN variability? • How is the observed variability related with physical
quantities of AGNs?
Absolute magnitude vs variability amplitude. Vanden Berk, et al. 2004
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AGN VARIABILITY
Observations
Host Galaxy
AGN
It is very hard to detect NIR even in moderate luminosity AGNs!
Image from: The Physics and Evolution of Active Galactic Nuclei, H. Netzer, 2013
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THE QUEST-LA SILLA AGN VARIABILITY SURVEY
• Images of Stripe82, ECDFS, XMM-LSS, Elais-S1, and COSMOS fields, taken between 2011 and 2015.
• Telescope: ESO-Schimdt (La Silla), 1m. • Instrument: QUEST2 camera 112 CCDs (7.5 deg2), Q band
(~sum of g and r filters). • Details in Cartier et al. 2015
~ 20TB of raw data
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ULTRAVISTA SURVEY
• UltraVista Survey in the COSMOS field (McCracken et al. 2012), taken between December 2009 and June 2014. • Telescope: VISTA (Paranal), 4.1m • Instrument: VIRCAM: Y,J,H and Ks bands
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VARIABILITY ANALYSIS
How to quantify AGN variability?
�2rms � err(�2
rms) > 0
χ2 Probability Excess Variance
�2rms =
�2LC � �2
m
m2�2 =
NobsX
i=1
(mi �m)2
�2m,i
P (�) > 0.95
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VARIABILITY ANALYSIS
The Structure Function (SF)
SF (�t) =
⌧r⇡
2|�mi,j |�
q�2i + �2
j
�
�t
Schmidt et al. (2010)
Y
MJD
SF (⌧) = A
✓⌧
1yr
◆�
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VARIABILITY ANALYSIS
The Structure Function (SF)
SF (�t) =
⌧r⇡
2|�mi,j |�
q�2i + �2
j
�
�t
Schmidt et al. (2010)
Y
MJD
SF
Δt (yr)
SF (⌧) = A
✓⌧
1yr
◆�
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VARIABILITY ANALYSIS
The Structure Function (SF)
SF (�t) =
⌧r⇡
2|�mi,j |�
q�2i + �2
j
�
�t
Schmidt et al. (2010)
Y
MJD
SF
Δt (yr)
SF (⌧) = A
✓⌧
1yr
◆�
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VARIABILITY ANALYSIS
The Structure Function (SF) Schmidt et al. (2010)
SF (⌧) = A
✓⌧
1yr
◆� P (A) / 1
AMCMC P (�) / 1
1 + �2 � > 0
1 > A > 0
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VARIABILITY ANALYSIS
The Structure Function (SF) Schmidt et al. (2010)
SF (⌧) = A
✓⌧
1yr
◆� P (A) / 1
AMCMC P (�) / 1
1 + �2 � > 0
1 > A > 0
L(A, �) =Y
i,j
1q(2⇡V 2
eff,ij)exp
�
�m
2ij
2V 2eff,ij
!
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VARIABILITY ANALYSIS
The Structure Function (SF) Schmidt et al. (2010)
Y
MJD
SF (⌧) = A
✓⌧
1yr
◆� P (A) / 1
AMCMC P (�) / 1
1 + �2 � > 0
1 > A > 0
L(A, �) =Y
i,j
1q(2⇡V 2
eff,ij)exp
�
�m
2ij
2V 2eff,ij
!
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VARIABILITY ANALYSIS
The Structure Function (SF) Schmidt et al. (2010)
Y
MJD
SF
Δt (yr)
SF (⌧) = A
✓⌧
1yr
◆� P (A) / 1
AMCMC P (�) / 1
1 + �2 � > 0
1 > A > 0
L(A, �) =Y
i,j
1q(2⇡V 2
eff,ij)exp
�
�m
2ij
2V 2eff,ij
!
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RESULTS: QUEST
Regis Cartier PhD Thesis, details in Cartier et al. 2015
Analysis for AGN with spectroscopic classification from optical counterpart catalog of the XMM-COSMOS field (Brusa et al. 2010)
% Variable objects in the Q band NL BL
Classic SF
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QUEST: AGN CANDIDATES
Star AGN
Star AGN
Spectroscopic follow up of our candidates during 2016.
u-g & g-r colors + variability properties
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RESULTS: ULTRAVISTA
Analysis for AGN with spectroscopic classification from optical counterpart catalog of the Chandra-COSMOS field (Marchesi et al. 2015), Only for Y band
MCMC SF
Y 0.08 < z < 5.31
Sánchez et al. in prep.
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RESULTS: ULTRAVISTA
Y filter: A vs HXR lum. Y filter: A vs (1+z).
log(A) = (�15.6± 6.3) + log(LHXR)(0.28± 0.14) + log(1 + z)(1.2± 0.3)
P = 0.06 P = 0.00
Preliminary
0.08 < z < 5.31
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SUMMARY
• Our optical and NIR analysis, demonstrate that BL objects show a different variability behavior than NL objects, occupying different regions in the Structure Function A-γspace.
• The amplitude of the variability “A” determined by the
Structure Function shows a positive correlation with redshift, which implies a positive correlation between frequency and amplitude of the variability.
• Variability-based AGN selection find AGN populations missed by other optical selection techniques.
ACKNOWLEDGMENTS: SOCHIAS grant through ALMA/Conicyt Project #31150039