extending α ox studies to include the numerous low-to- moderate luminosity agns aaron steffen the...
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![Page 1: Extending α OX Studies to Include the Numerous Low-to- Moderate Luminosity AGNs Aaron Steffen The Pennsylvania State University November 6th, 2006](https://reader030.vdocuments.mx/reader030/viewer/2022032800/56649d385503460f94a1248f/html5/thumbnails/1.jpg)
Extending αOX Studies to Include the Numerous Low-
to-Moderate Luminosity AGNs
Aaron SteffenThe Pennsylvania State University
November 6th, 2006
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Collaborators
Iskra StratevaMPE
Niel BrandtPSU
David AlexanderDurham, U.K.
Franz BauerColumbia
Anton KoekemoerSTScI
Bret LehmerPSU
Don SchneiderPSU
Cristian VignaliINAF - Bologna
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Extended Chandra Deep Field - South (E-CDF-S; Lehmer et al. 2005)
Four contiguous 250 ks ACIS-I exposures centered on the 1Ms CDF-S
COMBO-17 (Wolf et al. 2004)Optically selected AGNs using 5 Broad-band
and 12 Medium-band filters
Project Motivation● Extend αOX studies to include the low-to-moderate luminosity AGNs that numerically dominate the AGN population.
● Break the luminosity - redshift degeneracy present in flux-limited samples.
● Compile a large, homogeneous AGN sample and use both parametric and non-parametric statistical tests to determine if αOX evolves with cosmic time.
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Sobolewska, Siemiginowska & Zycki (2004)
Richards et al. (2006)
● UV emission from a thermalized thin accretion disk.
● X-ray emission from inverse-Compton scattering off of energetic electrons in optically thin corona.
● Radio jets and intrinsic absorption can affect the measurement of the intrinsic X-ray/UV emission.
Relation Between UV and X-ray Emission in AGN
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Sample#
srcs# X-ray
Detected
Strateva et al. (2006)
Seyfert 1s 25a 25 (100%)
SDSS / ROSAT 155126
(81%)
High-z 36 32 (89%)
Steffen et al. (2006)
BQS / ROSAT 46 45 (98%)
COMBO-17 / E-CDF-S
52 47 (90%)
High-z 19 32 (89%)
Total 333293
(88%)
Sample#
srcs# X-ray
Detected
Strateva et al. (2006)
Seyfert 1s 25a 25 (100%)
SDSS / ROSAT 155126
(81%)
High-z 36 32 (89%)
Steffen et al. (2006)
BQS / ROSAT 46 45 (98%)
COMBO-17 / E-CDF-S
52 47 (90%)
High-z 19 32 (89%)
Sample#
srcs# X-ray
Detected
Strateva et al. (2006)
Seyfert 1s 25a 25 (100%)
SDSS / ROSAT 155126
(81%)
High-z 36 32 (89%)
Breaking the L-z Degeneracy
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Comparing LUV and LX vs. redshift
Our sample spans 5 (4) orders of magnitude in LUV (LX).
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X-ray vs. Optical Luminosity
OLS Bisector yields:
Non-parametric
Kendall’s partial τ = 0.519 (15σ)
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Evidence for a non-linear relation
Dependance of αOX on log(LUV)
Non-parametric Kendall’s
partial τ = −0.377 (14σ)
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No Evidence for Evolution
ParametricNon-Parametric
Kendall’s Partial τ = −0.031 (1.3σ)
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Comparison with Earlier Studies
AT86
W94 S05 S06
Number of Sources
154 343 228 333
% X-rayDetected
61% 52% 86% 88%
Radio Loud or BALs?
Yes Yes No No
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Future Studies: Including the Most Luminous AGNs
Sample#
srcs# X-ray
Detected
Strateva et al. (2006)
Seyfert 1s 25a 25 (100%)
SDSS / ROSAT 155126
(81%)
High-z 36 32 (89%)
Steffen et al. (2006)
BQS / ROSAT 46 45 (98%)
COMBO-17 / E-CDF-S
52 47 (90%)
High-z 19 32 (89%)
Total 333293
(88%)
Sample#
srcs# X-ray
Detected
Strateva et al. (2006)
Seyfert 1s 25a 25 (100%)
SDSS / ROSAT 155126
(81%)
High-z 36 32 (89%)
Steffen et al. (2006)
BQS / ROSAT 46 45 (98%)
COMBO-17 / E-CDF-S
52 47 (90%)
High-z 19 18 (89%)
Just et al. (2007)
SDSS / Chandra 3030
(100%)
High-z 19 14 (74%)
Total 382337
(88%)
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Still no Evidence for Cosmic Evolution
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Are the COMBO-17 selected AGNs the Faint Extension of the SDSS
Population?
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COMBO-17 αOX Distrbution
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