Warm Dust in the Most Distant Warm Dust in the Most Distant QuasarsQuasars

Warm Dust in the Most Distant Warm Dust in the Most Distant QuasarsQuasars

Ran WangDepartment of Astronomy, Peking

University, China

IntroductionIntroductionIntroductionIntroduction

• Why looking for dust at z~6– The mass of dust in the earliest and most

massive galaxies: dust formation within 1 Gyr.– The dust temperature, distribution, and

Luminosity: dust heating quasar systems. FIR luminosity SFR evolutionary stage of the black hole – bulge system.

Tremaine et al. (2002)Marconi & Hunt. (2002)

MBH~σ4

MBH~10-3MBulge

IntroductionIntroductionIntroductionIntroduction

SampleSampleSampleSample

• There are totally Thirty-three quasars discovered at z~6.– z=5.71 to 6.43– M_1450A < -25.0

• Twenty-two from the SDSS survey of ~8000 deg^2 area, with m1450A < 20.

• Nine from deeper optical imaging with m1450A>20, Jiang et al. 2007; Willott et al. 2007

• IR (Spitzer) + optical: one; Cool et al. (2006)• Radio (FIRST) + optical: one; McGreer et al. (2006)

Most of these objects were optically selected from the SDSS survey

Represent the most luminous quasar population at z~6.

SHARC-II CSO

ObservationsObservationsObservationsObservations

MAMBO IRAM-30m

The average FIR and radio The average FIR and radio emissionemission

The average FIR and radio The average FIR and radio emissionemission

FIR-millimeter spectral index ~2

Wang et al. (2008 submitted)

Star formation in the mm non-Star formation in the mm non-detectionsdetections

Star formation in the mm non-Star formation in the mm non-detectionsdetections

• The average FIR luminosity: 1.2x1012 Lsun

– Even 50% of the FIR emission from star formation, the star formation rate => 200 Msun yr-1

– The major bulge building stage via starburst has been finished ?

The SEDs of millimeter detectionsThe SEDs of millimeter detectionsThe SEDs of millimeter detectionsThe SEDs of millimeter detections

The bright millimeter detectionsThe bright millimeter detectionsThe bright millimeter detectionsThe bright millimeter detections

•The FIR emission exceeds that of the local quasar template.

•The FIR SED is consistent with optically thin gray-body emission from 40 ~ 50 K dust.

•The FIR-to-radio SED is consistent with that of typical star forming galaxies.

•Dust mass: ≥108 Msun

•FIR luminosity ~ 1013 Lsun

5.0

)50~()(4(][~

dvKTB

Ldust

vv

FIRR

Luminosity correlation LLuminosity correlation LFIRFIR - L - LBolBolLuminosity correlation LLuminosity correlation LFIRFIR - L - LBolBol

Wang et al. (2008 in press)

Luminosity correlation LLuminosity correlation LFIRFIR – L – L’’COCOLuminosity correlation LLuminosity correlation LFIRFIR – L – L’’COCO

Star formation in the z~6 quasarsStar formation in the z~6 quasarsStar formation in the z~6 quasarsStar formation in the z~6 quasars

• The mm and CO detected quasars at z~6:– FIR emission from 40 ~ 50 K warm dust.– Properties similar to that of star forming

galaxies.

– Derived star formation rate: ≥ 103 Msun yr-1

– Active bulge building via massive star formation co-eval with SMBH accretion.

LLFIRFIR & Lya emission & Lya emissionLLFIRFIR & Lya emission & Lya emission

Omont et al. (1996): Three kinds of spectra from z>4 quasars

LLFIRFIR & Lya emission & Lya emissionLLFIRFIR & Lya emission & Lya emission

• Quasars at z~6:• Most of the

millimeter detections tend to have log(EW)Lya < 1.5.

• The origin of this effect is not clear yet.

• More observations…

Wang et al. (2008 in press)

• We studied the (sub)millimeter emission from the host galaxies of quasars at z~6.

• About 30% of these sources have been detected in warm dust continuum at 1.2 mm.

• The average FIR-to-radio SED of the non-detected sources is comparable to that of local optical quasars.

• Obvious FIR excesses in the SEDs of the strong millimeter detections.

• FIR dust heating dominated by Star formation at a rate of a few 1000 Msun yr-1 .

• The millimeter detected quasars tend to have weak UV line emission.

SummarySummarySummarySummary

Introduction – The discovery of Introduction – The discovery of z~6 quasarsz~6 quasars

1148+5251 z=6.42

Bertoldi et al. (2003)

Beelen et al. 2006