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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
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
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
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
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
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
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
◆�
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
◆�
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
◆�
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
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
!
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
!
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
!
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
QUEST: AGN CANDIDATES
Star AGN
Star AGN
Spectroscopic follow up of our candidates during 2016.
u-g & g-r colors + variability properties
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.
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
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
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