Modern Quasar SEDs Zhaohui Shang （ Tianjin Normal University ） Kunming, Feb. 2009.
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Modern Quasar SEDsZhaohui ShangTianjin Normal University
Kunming, Feb. 2009
Quasar Spectral Energy Distributions (SED) Significant energy output over wide frequency range Big blue bump (UV bump) strongest energy output Infrared bump energy output comparable to UV bump Quasar SED (Elvis et al. 1994) Infrared broad band photometry
AGN Structure - Multi-wavelength StudyMajor components:super massive black hole
accretion disk (opt., UV, X-ray, continuum)
emision line clouds/wind
dusty torus (IR)
Example: Big Blue Bump Spectral break at ~1000 (HST composite)Telfer et al. (2002)
184 objects332 HST spectraz > 0.33Zheng et al. (1997)
101 objects284 HST spectraz > 0.33HST AGN composite spectra
Recent Results from Spitzer (broad band IRAC) 259 SDSS quasars (Richards et al. 2006) Overall SEDs consistent with the mean SEDs of Elvis et al. 1994 Large SED diversity for individual objects
Recent Results from Spitzer (broad band IRAC, MIPS)13 high-redshift (z>4.5) quasars (Hines et al. 2006, ApJ, 641, L85)Consistent with SEDs of low-redshift quasars (Elvis et al. 1994)
Recent Results from Spitzer (IRS spectra)E.g,29 quasars (Netzer et al. 2007)
Importance of Quasar SEDs, practically Important in determining the bolometric correction of quasars (AGNs) Accretion disk models: distinguish thin or slim disks??!Eddington Accretion Ratio:
Modern Quasar SEDOur projectSEDs from radio to X-ray utilizing best data from both ground and space telescopesUpdate Elvis et al. 1994Better estimate of bolometric luminosity and correctionMulti-wavelength study of quasar physics
AGN SEDs: RevisitCompton gamma-ray ObservatoryChandra XMMHubbleSub-mm arrayVLA surveysOpticalGround-basedSpitzerFUSE
Sample (heterogeneous)Total 85 quasars from 3 sub-samples:
Sub-sample 1: 22 PG quasars (a complete sample) (Laor et al. 1994, Shang et al. 2003)Sub-sample 2: 17 AGNs from FUSE UV-bright sample (Kriss 2000, Shang et al. 2005)Sub-sample 3: 50 radio-loud quasars (Wills et al. 1995, Netzer et al. 1995)
Low-redshift, z < 0.5 (most) Quasi-simultaneous UV-optical spectra to reduce uncertainty from variability
Data (UV-optical)Quasi-simultaneous UV-optical spectraRest wavelength coverage 1000 8000 , (some 900 9000 )FUSEHSTground-based
Data (Infrared)2MASS near-IR JHK photometrySpitzer IRS mid-IR spectra (rest frame ~5-35 m) MIPS far-IR (24, 70, 160 m) photometryIRS spectra:Silicates features at 10 and 18 m (Siebenmorgen et al. 2005, Sturm et al. 2005, Hao et al. 2005, Weedman et al. 2005)Emission lines [Ne III]15.56 m, [O IV]25.89 m, Power-law between ~5-8 m, and beyond
Data (Radio, X-ray)RadioSurveys from 74MHz to 15GHz, including 4C, VLSS, WENSS, Texas, FIRST, NVSS, GB6, and some GHz surveysHigher resolution allows to separate the real cores for some objects
X-rayChandra + XMM archive data/literatureHigher resolution and sensitivity
Spectral Energy DistributionRadio to X-ray
Spectral Energy Distribution Radio to X-rayCompared with Elvis 1994: similar in overall shape
Spectral Energy Distributions (mid-IR, optical, UV)A sub-sample of 15 objects (6 radio-loud, 9 radio-quiet)
Composite spectrum (UV + optical + mid-IR)Normalized at 5600 Clear Silicates features around 10 and 18 m
A sub-sample of 15 objects (6 radio-loud, 9 radio-quiet)
Composite spectrum (UV + optical + mid-IR)Normalized at 5600 Clear Silicates features around 10 and 18 mSpectral Energy Distributions (mid-IR, optical, UV)Near-IR composite spectrum (Glikman et al. 2006)27 AGNs (z
Spectral Energy Distributions (mid-IR, optical, UV)Compared to the mean SEDs of Elvis et al. 1994 (Normalized to UV-optical)Overall similar patternsMore details with emission featuresA sub-sample of 15 objects (6 radio-loud, 9 radio-quiet)
Composite spectrum (UV + optical + mid-IR)Normalized at 5600 Clear Silicates features around 10 and 18 mNear-IR composite spectrum (Glikman et al. 2006)27 AGNs (z
Spectral Energy Distributions (radio-loud/quiet)Normalized at 5600 Normalized at 8 mSmall difference between radio-loud and radio-quiet in mid-IR
Spectral Energy Distributions (diversity)Normalized at 5600 Normalized at 8 mIndividual mid-IR spectral are different.Contribute differently to the bolometric luminosity (LMIR~8% to 30% of LBol, assuming LBol=9L(5100)
Spectral Energy Distributions => Bolometric LuminosityIn progress Bolometric luminosity estimate must take into account the diversity of the (mid-) infrared spectra.Mid-IR spectra can help to improve the bolometric correction, e.g.,
Two problems:Host galaxy contaminationDouble counting
Bolometric Luminosity (2 problems)1. Host galaxy contamination up to 50% or more in near-IRCan be corrected with high-resolution imaging of host galaxies.McLeod & Rieke 1995
Bolometric Luminosity (2 problems)1. Double Counting This problem can NOT be solved without assumptions. The bolometric luminosity is an upper limit.
Conclusions Quasar SEDs, bolometric luminosity and bolometric corrections are important.
It is hard to do. We must do it.
Thank you !
Result 2 of 3: Evidence of Intrinsic Reddening
Result 2 of 3: Evidence of Intrinsic Reddening (Is it real?)Correlation holds without the outliers.
Result 2 of 3: Evidence of Intrinsic Reddening (is it real?)Correlation holds without the outliersCorrelation is NOT caused by a correlation between spectral slope and the UV luminosity.Show direct evidence of intrinsic dust reddening.
All quasars have intrinsic reddening (our sample is blue).Mid-IR + UV-optical info could lead to good estimate of intrinsic reddening.
Result 3 of 3: Eigenvector one (EV1) in Mid-IR(Boroson & Green 1992)
Result 3 of 3: Eigenvector one (EV1) in Mid-IREquivalent width of Silicates 10m also seems to be a parameter of EV1.Consistent with the picture of covering factor.r=0.64, p=1.0%
SummaryWe constructed the UV-optical and mid-IR composite spectra of low-redshift broad-line (type I) quasars from a sub-sample.Unlike borad-band SEDs, the composites show detailed mid-IR features.Mid-IR spectra needs to be considered in estimating a better bolometric luminosity.
All quasars seem to have intrinsic dust reddening.Mid-IR and UV-optical information may be used to estimate the intrinsic reddening.
Silicates 10m feature is a parameter in the Eigenvector 1 relationships.This agrees with the UV-optical results.