LAMSOT LAMSOT 多波段巡天多波段巡天

魏建彦 周宏岩 何香涛魏建彦 周宏岩 何香涛

井冈山 井冈山 2005.04.272005.04.27

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,Opt: (POSS) SDSS/LAMOST,UV: GALEXX-ray: ROSAT, XMM/Chandra …

Each survey has its selection effect. Each survey has its selection effect. Complete surveys are the most boring things Complete surveys are the most boring things in astronomy.in astronomy.

LAMOST compared with SDSSLAMOST compared with SDSS

Without corresponding photometric surveyWithout corresponding photometric survey

Start when SDSS finishedStart when SDSS finished

LAMOST AGN samples -- more diversity

-- much more workload •SDSS AGNs: SDSS AGNs: 1. opt color; 2. FIRST counterpart; 3. RASS counterpart1. opt color; 2. FIRST counterpart; 3. RASS counterpart

•LAMOST AGNs: LAMOST AGNs: 1. opt color using SDSS photometric data (~1 mag 1. opt color using SDSS photometric data (~1 mag deeper); 2. NVSS/FIRST counterpart; 3. NIR-Opt color; 4. Opt-UV color; 5. deeper); 2. NVSS/FIRST counterpart; 3. NIR-Opt color; 4. Opt-UV color; 5. XMM/Chandra counterparts; 6. variability; 7. other missions, e.g., SpitzerXMM/Chandra counterparts; 6. variability; 7. other missions, e.g., Spitzer

RQ

RL

Elvis et al. ‘94

Optical

I. Radio-selection at low Galactic latitude

RL ~ 10% AGN (opt. surveys), c.f. Elvis 1994

RQ

RL

Elvis et al. ‘94

Optical

Radio Power

Radio-to-optical ratio:

R* Lr / Lo

Galactic Latitude = -8.35293

2MASX J210931.90+353257.3 = 2MASX J210931.90+353257.3 = VCS1 J2109+3532VCS1 J2109+3532

2’X2’ 2MASS Ks-band image

2’X2’ DSS image

Galactic Latitude = -10.5571

R = 17.32, BJ =18.53 S1.4GHz, NVSS =25.5 mJy

2MASS J204352.72+252357.6 = NVSS J2043+2523

1. Radio-selected AGN candidates at low Galactic 1. Radio-selected AGN candidates at low Galactic latitudelatitude

12 low Galactic latitude radio sources (|b|<15 deg) 12 low Galactic latitude radio sources (|b|<15 deg) observed by the 2.16m telescope:observed by the 2.16m telescope:

6 quasars6 quasars

2 BL Lac candidates2 BL Lac candidates

1 LERG?1 LERG?

3 blank fields with a foreground star?3 blank fields with a foreground star?

To identify radio sources at low Galactic latitude, accurate To identify radio sources at low Galactic latitude, accurate position is needed position is needed NVSS flux > 15 mJy sub-sample (~1” NVSS flux > 15 mJy sub-sample (~1” position) position)

Selection effect of radio-loud Selection effect of radio-loud quasarsquasars

(Wang et al. 2005)(Wang et al. 2005)

Optical

R

R

Ivezic et al 03

See also Jester & Kron: SDSS+FIRST

RQ/RL dichotomy?

If the SDSS selection criterion adopted, ~7% extended sources If the SDSS selection criterion adopted, ~7% extended sources would be missed, radio emission of ~15% objects underestimatedwould be missed, radio emission of ~15% objects underestimated

~70% can be got back by NVSS~70% can be got back by NVSS More dichotomy than previous works based on SDSS-FIRST

Another problem: over-resolutionAnother problem: over-resolution

2. IR-Opt color selection2. IR-Opt color selection

F/MIR: lack of large area deep surveyF/MIR: lack of large area deep survey NIR: 2MASS (limit ~ 1 mJy)NIR: 2MASS (limit ~ 1 mJy)

2MASS red AGN survey (J-K2MASS red AGN survey (J-Kss > 2 mag, Cutri et al. 2001): > 2 mag, Cutri et al. 2001):

High efficiency at high Galactic latitude (High efficiency at high Galactic latitude (ξξ ~75% AGN), but ~75% AGN), but ξξ↘↘ as |b| as |b|↘↘

Be prone to partly obscured AGN, but tend to Be prone to partly obscured AGN, but tend to lost most of blue lost most of blue quasars quasars (only ~5% optically selected quasars have so red NIR color) (only ~5% optically selected quasars have so red NIR color)

Opt color selection: red AGNs missedOpt color selection: red AGNs missed Both red and blue AGNs can be selected using NIR-Opt Both red and blue AGNs can be selected using NIR-Opt

color, provided the contamination of the host galaxies is color, provided the contamination of the host galaxies is not serious:not serious:

high efficiency/completenesshigh efficiency/completeness

However, 2MASS much shallow for LAMOST (only ~16% of the SDSS However, 2MASS much shallow for LAMOST (only ~16% of the SDSS quasars are quasars are detected by 2MASS)detected by 2MASS)

3. 3. Optical color selectionOptical color selection

Within the area covered by SDSS: Within the area covered by SDSS:

same criteria as SDSS but ~1 mag same criteria as SDSS but ~1 mag deeperdeeper

More quasars at intermediate z with wider luminosity More quasars at intermediate z with wider luminosity rangerange

High quality spectra (most objects targeted as High quality spectra (most objects targeted as galaxies) galaxies)

to dig out diluted/obscured AGNs to dig out diluted/obscured AGNs

4. Opt-UV selection4. Opt-UV selection

At z<2, SDSS use power-law spectral shape to search for quasar candidates (the most prominent feature in quasars’ spectra – Lyα break is short ward of the SDSS u-band).

GALEX: AIS ~ SDSS spectral sample; MIS ~ SDSS photometric sample GALEX can detect Lyα break 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).

UV-Opt color-color diagram for UV-Opt color-color diagram for quasarsquasars, , galaxiesgalaxies, and , and starsstars

Redshift distribution of GALEX-SDSS quasars

5. X -ray selection5. X -ray selection

Absorption in X-raysAbsorption in X-rays

• 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

Type 1 AGN SEDType 1 AGN SED

Manners, 2002mm

far-IR near-IR Optical-UV X-rays

Type 2 AGN SEDType 2 AGN SED

Norman et al, 2002

Radio far-IR optical-UV X-rays

6. Search for low luminosity and 6. Search for low luminosity and high redshift AGNs through high redshift AGNs through

variabilityvariability

Variability selection can be applied to “extended” objects, i.e. Variability selection can be applied to “extended” objects, i.e. to search for AGNs which do not dominate the light of the to search for AGNs which do not dominate the light of the host galaxyhost galaxy

MMB_nuclB_nucl < -22 < -22 Variability increases with redshiftVariability increases with redshift (Giallongo, Trevese & (Giallongo, Trevese &

Vagnetti 91) Vagnetti 91) Variability decreases withVariability decreases withλλrest rest and high z QSOs and high z QSOs are more variable since they are observed at shorter are more variable since they are observed at shorter λλrestrest (DiClemente,et al. 96)(DiClemente,et al. 96)

GALEX repeated observationsGALEX repeated observations SDSS vs. POSS and SDSS repeated observationsSDSS vs. POSS and SDSS repeated observations PAN-STARsPAN-STARs New variable AGN sample compiled from LAMOST itselfNew variable AGN sample compiled from LAMOST itself

7. Selecting AGN with 7. Selecting AGN with SpitzerSpitzer

Very efficient

Very efficient !

SummarySummary Optical selection with SDSS (1 mag Optical selection with SDSS (1 mag

deeper)deeper) Radio selection ( deeper, lower gal. Radio selection ( deeper, lower gal.

latitude )latitude ) 2MASS/optical/Radio selection2MASS/optical/Radio selection Variable-object selection ( Pan-Stars … )Variable-object selection ( Pan-Stars … ) …………

Various samples to address relevant AGN physicsVarious samples to address relevant AGN physics

Muti-band identifications of star samplesMuti-band identifications of star samples