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Modern Quasar SEDs

Modern Quasar SEDs. Zhaohui Shang （ Tianjin 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.

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Modern Quasar SEDs

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  1. Modern Quasar SEDs Zhaohui Shang （Tianjin Normal University） Kunming, Feb. 2009

  2. 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

  3. AGN Structure - Multi-wavelength Study Major components: • super massive black hole • accretion disk (opt., UV, X-ray, continuum) • emision line clouds/wind • dusty torus (IR) • Jets (radio)

  4. Example: Big Blue Bump – Spectral break at ~1000 Å(HST composite) HST AGN composite spectra Zheng et al. (1997) • 101 objects • 284 HST spectra • z > 0.33 Telfer et al. (2002) • 184 objects • 332 HST spectra • z > 0.33

  5. 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

  6. 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)

  7. Recent Results from Spitzer (IRS spectra) • E.g, • 29 quasars (Netzer et al. 2007)

  8. 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:

  9. Modern Quasar SED • Our project • SEDs from radio to X-ray utilizing best data from both ground and space telescopes • Update Elvis et al. 1994 • Better estimate of bolometric luminosity and correction • Multi-wavelength study of quasar physics

  10. AGN SEDs: Revisit Hubble Spitzer FUSE ChandraXMM Comptongamma-ray Observatory VLAsurveys Optical Ground-based Sub-mmarray

  11. 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

  12. Data (UV-optical) • Quasi-simultaneous UV-optical spectra • Rest wavelength coverage 1000 – 8000 Å, (some 900 – 9000 Å) FUSE ground-based HST

  13. Data (Infrared) • 2MASS near-IR JHK photometry • Spitzer IRS mid-IR spectra (rest frame ~5-35 µm) • MIPS far-IR (24, 70, 160 µm) photometry • IRS spectra: • Silicates features at 10 and 18 µm(Siebenmorgen et al. 2005, Sturm et al. 2005, Hao et al. 2005, Weedman et al. 2005) • Emission lines [Ne III]15.56 µm, [O IV]25.89 µm, …… • Power-law between ~5-8 µm, and beyond

  14. Data (Radio, X-ray) • Radio • Surveys from 74MHz to 15GHz, including 4C, VLSS, WENSS, Texas, FIRST, NVSS, GB6, and some GHz surveys • Higher resolution allows to separate the real cores for some objects • X-ray • Chandra + XMM archive data/literature • Higher resolution and sensitivity

  15. Spectral Energy Distribution Radio to X-ray

  16. Spectral Energy Distribution Radio to X-ray Compared with Elvis 1994: similar in overall shape

  17. 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 Å • Clear Silicates features around 10 and 18 µm

  18. 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 Å • Clear Silicates features around 10 and 18 µm • Near-IR composite spectrum (Glikman et al. 2006) • 27 AGNs (z<0.4) • 1 micron inflexion

  19. 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 Å • Clear Silicates features around 10 and 18 µm • Near-IR composite spectrum (Glikman et al. 2006) • 27 AGNs (z<0.4) • 1 micron inflexion • Compared to the mean SEDs of Elvis et al. 1994 (Normalized to UV-optical) • Overall similar patterns • More details with emission features

  20. Spectral Energy Distributions (radio-loud/quiet) Normalized at 8 µm Normalized at 5600 Å Small difference between radio-loud and radio-quiet in mid-IR

  21. Spectral Energy Distributions (diversity) • Individual mid-IR spectral are different. • Contribute differently to the bolometric luminosity(LMIR~8% to 30% of LBol, assuming LBol=9λLλ(5100Å) Normalized at 8 µm Normalized at 5600 Å

  22. Spectral Energy Distributions => Bolometric Luminosity • In 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 contamination • Double counting

  23. Bolometric Luminosity (2 problems) 1. Host galaxy contaminationup to 50% or more in near-IR McLeod & Rieke 1995 Can be corrected with high-resolution imaging of host galaxies.

  24. Bolometric Luminosity (2 problems) 1. Double Counting • This problem can NOT be solved without assumptions. • The bolometric luminosity is an upper limit.

  25. Conclusions • Quasar SEDs, bolometric luminosity and bolometric corrections are important. • It is hard to do. • We must do it. • Thank you !

  26. Result 2 of 3: Evidence of Intrinsic Reddening

  27. Result 2 of 3: Evidence of Intrinsic Reddening (Is it real?) • Correlation holds without the “outliers”.

  28. Result 2 of 3: Evidence of Intrinsic Reddening (is it real?) • Correlation holds without the “outliers” • Correlation 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.

  29. Result 3 of 3: Eigenvector one (EV1) in Mid-IR (Boroson & Green 1992)

  30. Result 3 of 3: Eigenvector one (EV1) in Mid-IR r=0.64, p=1.0% • Equivalent width of Silicates 10µm also seems to be a parameter of EV1. • Consistent with the picture of covering factor.

  31. Summary • We 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 10µm feature is a parameter in the Eigenvector 1 relationships. • This agrees with the UV-optical results.

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