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LAMSOT 多波段巡天 魏建彦 周宏岩 何香涛 井冈山 2005.04.27

LAMSOT 多波段巡天 魏建彦 周宏岩 何香涛 井冈山 2005.04.27. Understanding of Complex AGN Phenomena Requires Complex and Information-Rich Data Sets, and the Tools to Explore them …. … Large, homogeneous Sky Surveys at Multiple Wavelength Bands: Radio:FIRST/NVSS FIR: IRAS (ISO, Spitzer) NIR: 2MASS,

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LAMSOT 多波段巡天 魏建彦 周宏岩 何香涛 井冈山 2005.04.27

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  1. LAMSOT 多波段巡天魏建彦 周宏岩 何香涛井冈山 2005.04.27

  2. Understanding of Complex AGN Phenomena Requires Complex and Information-Rich Data Sets, and the Tools to Explore them … … Large, homogeneous Sky Surveys at Multiple Wavelength Bands: Radio:FIRST/NVSS FIR: IRAS (ISO, Spitzer) NIR: 2MASS, Opt: (POSS) SDSS/LAMOST, UV: GALEX X-ray: ROSAT, XMM/Chandra … • Each survey has its selection effect. Complete surveys are the most boring things in astronomy.

  3. LAMOST compared with SDSS • Without corresponding photometric survey • Start when SDSS finished • LAMOST AGN samples -- more diversity • -- much more workload • SDSS AGNs: 1. opt color; 2. FIRST counterpart; 3. RASS counterpart • LAMOST AGNs: 1. opt color using SDSS photometric data (~1 mag deeper); 2. NVSS/FIRST counterpart; 3. NIR-Opt color; 4. Opt-UV color; 5. XMM/Chandra counterparts; 6. variability; 7. other missions, e.g., Spitzer

  4. RL RL Radio Power Radio-to-optical ratio: R*º Lr / Lo RQ RQ Elvis et al. ‘94 Elvis et al. ‘94 Optical Optical I. Radio-selection at low Galactic latitude RL ~ 10% AGN (opt. surveys), c.f. Elvis 1994

  5. 2MASX J210931.90+353257.3 = VCS1 J2109+3532 Galactic Latitude = -8.35293 2’X2’ DSS image 2’X2’ 2MASS Ks-band image

  6. 2MASS J204352.72+252357.6 = NVSS J2043+2523 Galactic Latitude = -10.5571 R = 17.32, BJ =18.53 S1.4GHz, NVSS =25.5 mJy

  7. 1. Radio-selected AGN candidates at low Galactic latitude • 12 low Galactic latitude radio sources (|b|<15 deg) observed by the 2.16m telescope: 6 quasars 2 BL Lac candidates 1 LERG? 3 blank fields with a foreground star? • To identify radio sources at low Galactic latitude, accurate position is needed  NVSS flux > 15 mJy sub-sample (~1” position)

  8. R Optical Ivezic et al 03 R See also Jester & Kron: SDSS+FIRST Selection effect of radio-loud quasars(Wang et al. 2005) RQ/RL dichotomy?

  9. If the SDSS selection criterion adopted, ~7% extended sources would be missed, radio emission of ~15% objects underestimated • ~70% can be got back by NVSS  Moredichotomy than previous works based on SDSS-FIRST

  10. Another problem: over-resolution

  11. 2. IR-Opt color selection • F/MIR: lack of large area deep survey • NIR: 2MASS (limit ~ 1 mJy) 2MASS red AGN survey (J-Ks > 2 mag, Cutri et al. 2001): High efficiency at high Galactic latitude (ξ ~75% AGN), but ξ↘ as |b|↘ Be prone to partly obscured AGN, but tend to lost most of blue quasars (only ~5% optically selected quasars have so red NIR color) • Opt color selection: red AGNs missed • Both red and blue AGNs can be selected using NIR-Opt color, provided the contamination of the host galaxies is not serious: high efficiency/completeness However, 2MASS much shallow for LAMOST (only ~16% of the SDSS quasars are detected by 2MASS)

  12. 3. Optical color selection Within the area covered by SDSS: same criteria as SDSS but ~1 mag deeper • More quasars at intermediate z with wider luminosity range • High quality spectra (most objects targeted as galaxies) to dig out diluted/obscured AGNs

  13. 4. Opt-UV selection • At z<2, SDSS use power-law spectral shape to search for quasar candidates (the most prominent feature in quasars’ spectra – Lyαbreak is short ward of the SDSS u-band). • GALEX: AIS ~ SDSS spectral sample; MIS ~ SDSS photometric sample • GALEX can detectLyαbreak of z<2 in the UV bands  a large number of new (fainter) quasars in this redshift range (improving our measurement of the QSO luminosity function at z < 2).

  14. UV-Opt color-color diagram for quasars, galaxies, and stars Redshift distribution of GALEX-SDSS quasars

  15. 5. X -ray selection • Recent results (e.g., Kurazkiewicz et al. 2003) indicate • logNH(torus)~23 • Hard X-ray survey, such as XMM/Chandra, should be enough to search for even heavily obscured AGNs Absorption in X-rays

  16. Type 1 AGN SED far-IR near-IR Optical-UV X-rays mm Manners, 2002

  17. Type 2 AGN SED X-rays Radio far-IR optical-UV Norman et al, 2002

  18. 6. Search for low luminosity and high redshift AGNs through variability • Variability selection can be applied to “extended” objects, i.e. to search for AGNs which do not dominate the light of the host galaxy MB_nucl < -22 • Variability increases with redshift (Giallongo, Trevese & Vagnetti 91) Variability decreases withλrest and high z QSOs are more variable since they are observed at shorter λrest(DiClemente,et al. 96) • GALEX repeated observations • SDSS vs. POSS and SDSS repeated observations • PAN-STARs • New variable AGN sample compiled from LAMOST itself

  19. 7. Selecting AGN with Spitzer Very efficient Very efficient !

  20. Summary • Optical selection with SDSS (1 mag deeper) • Radio selection ( deeper, lower gal. latitude ) • 2MASS/optical/Radio selection • Variable-object selection ( Pan-Stars … ) • …… Various samples to address relevant AGN physics Muti-band identifications of star samples

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