dust and molecular gas in the most distant quasars

Dust and molecular gas in the Dust and molecular gas in the most distant quasarsmost distant quasars

Dust and molecular gas in the Dust and molecular gas in the most distant quasarsmost distant quasars

Ran WangDepartment of Astronomy, Peking University,

China

Supervisor: Chris Carilli ( NRAO)Collaborators: Bertoldi, F. (University of Bonn); Cox, P. (IRAM); Fan, X. (University of Arizona); Jiang, L. (University of Arizona); Menten, K. (MPIfR); Neri, R. (IRAM); Omont, A. (IAP); Strauss, M. (Princeton); Wagg, J. (NRAO); Walter, F. (MPIfA)

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

Introduction – the first discovery of dust and Introduction – the first discovery of dust and CO at z~6CO at z~6

Bertoldi et al. (2003)

Beelen et al. 2006

Introduction – the first discovery of dust and Introduction – the first discovery of dust and CO at z~6CO at z~6

Bertoldi et al. 2003Bertoldi et al. 2003

Walter et al. 2004; Carilli et al. 2008

Introduction – Black hole/bulge Introduction – Black hole/bulge relationsrelations

Introduction – Black hole/bulge Introduction – Black hole/bulge relationsrelations

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

MBH~σ4

MBH~10-3MBulge

Introduction – Introduction – Black hole/bulge Black hole/bulge relationsrelations

Introduction – Introduction – Black hole/bulge Black hole/bulge relationsrelations

Coppin et al. (2008)

• What is the evolutionary stage of these z~6 quasars?• How the most massive black hole – bulge

systems evolve at their early stage. • Can we see active building via massive star

formation co-eval with rapid black hole accretion?

• Dynamical mass;• Black hole – bulge ratios;

IntroductionIntroductionIntroductionIntroduction

•The host galaxies of these z~6 quasars are still the only sample of the earliest galaxies that are detectable with our current millimeter and radio instruments.•What are the physical properties of these quasar host galaxies?

•Dust and gas masses;•Dust temperature;•Molecular excitation;•Star formation history.



• We are pursuing cm and mm studies of all the quasars discovered at z~6– We first do a millimeter and radio

continuum survey with all the z~6 quasars.

– Further observations at submm wavelengths with strong millimeter detections to measure the FIR SED and determine the dust temperature.

– Search for CO with the millimeter detections.

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 m_1450A < 20; Fan et al. 200x

• Five from the SDSS Deep Stripe of ~260 deg^2, with 20 < m_1450A < 21.5; Jiang et al. 2007

• Four from the Canada-France High-z Quasar Survey (CFHQS), from ~400 deg^2 area, with m_1450A > 21; 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.

• Observations from X-ray to near-IR show spectral energy distributions similar to that of the typical optical quasars at low z (Jiang et al. 2006).

• AGN activities similar to that in the low-z quasars dominate the X-ray to near-IR emission of these z~6 objects.

SampleSampleSampleSample

SHARC-II CSO

PdBI IRAM

ObservationsObservationsObservationsObservations

MAMBO IRAM-30mVLA

• MAMBO observations of 33 sources– rms in the range of 0.4 to 1.1 mJy with a

median value of 0.6 mJy– Ten are detected at >= 3 sigma level– The detection rate is (30 +/-10) %,

consistent with the (sub)mm detection rate of optically bright quasars at z~2 (Omont et al. 2003) and z~4 (Omont et al. 2001; Carilli et al. 2001)

A summary of the (sub)mm and A summary of the (sub)mm and radio Resultsradio Results




• VLA observation of 32 sources– rms <= 20 uJy for most of the sources – Ten were detected, with two of them

having flux densities > 1mJy– Three of them have radio loudness R

≥10

• The radio loud fraction at z~6: one out of the primary SDSS sample of 22 sources.

Av

GHzv

f

fR

4400,

5,

Analysis – the average FIR and radio Analysis – the average FIR and radio emissionemission


• The mean 250 GHz flux density – The whole sample: 1.26 +/- 0.10 mJy– The subsample of 10 MAMBO detections:

2.73 +/- 0.06 mJy– The subsample of 23 MAMBO non-

detections:

•<f250GH>= 0.52 +/- 0.13 mJy

– No difference in <f250GHz> when radio loud sources are excluded.



FIR-millimeter spectral index ~2

•The FIR-to-1450A luminosity ratios of the three groups have a range of ~0.6dex.

•The mean value of the non-detections matches the extrapolation of the template if a FIR-millimeter spectral index of a ≥ 2 is assumed.

Wang et al. (2008, in press.)

Analysis – SEDs of MAMBO detectionsAnalysis – SEDs of MAMBO detectionsAnalysis – SEDs of MAMBO detectionsAnalysis – SEDs of MAMBO detections

Wang et al. (2008, in press.)

• Get a better measurement of the excess FIR dust emission.– Determine the dust temperature (Td): 100 K or 30 – 60

K?• Need measurements at shorter wavelengths.

– Determine the emissivity index (β): dust compositions• Need measurements at longer wavelengths.

Analysis – optically thin dust emissionAnalysis – optically thin dust emissionAnalysis – optically thin dust emissionAnalysis – optically thin dust emission

Assumption: optically thin gray-body

Analysis – the bright millimeter Analysis – the bright millimeter detectionsdetections


• Confirm the FIR excesses in the quasar SEDs.• A measurement of the dust temperature

(combined with MAMBO, SCUBA, and PdBI data):40 to 50 K

• A measurement of the dust mass: a few 108 Msun

• The size of the dust emission region:

1013 Lsun FIR luminosity, optically thin Rdust~5kpc



5.0

)50~()(4(][~

dvKTB

Ldust

vv

FIRR

Analysis – Luminosity correlation LAnalysis – Luminosity correlation LFIRFIR - - LLBolBol

Analysis – Luminosity correlation LAnalysis – Luminosity correlation LFIRFIR - - LLBolBol

• The relationships between FIR and AGN bolometric luminosity derived from local quasar samples (Hao et al. 2005).

– More than half of the MAMBO detected quasars at z~6 follow the relation defined by the IR luminous quasars hosted in ULIRGs

– The average value of the non-detections.

Wang et al. (2008, in press)

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)

Molecular COMolecular CO in the z~6 quasars in the z~6 quasars Molecular COMolecular CO in the z~6 quasars in the z~6 quasars

•Molecular CO emission has been detected in the mm bright quasars.

•Gas mass : M(H2) ~ a few 1010 Msun .

•CO line width of the new detections: FWHM ≥ 500 km/s.

•The median value is 300 km/s for previous CO detected quasars at high-z.

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

The star formation efficiencyThe star formation efficiencyThe star formation efficiencyThe star formation efficiency

Discussion – star formation in the z~6 Discussion – star formation in the z~6 quasarsquasars


• About 30% of the optically selected quasars at z~6 have been detected, and most of the detections show FIR excesses in their SEDs.

• The MAMBO undetected quasars at z~6:– The average FIR-to-radio SED is consistent with

the templates of local optical quasars.– The average FIR to AGN-bolometric luminosity

ratio follows the trend defined by local PG quasars.

– FIR emission from the outer region of the dust torus.

– Any contribution from star formation?

• The average FIR luminosity: 1.2x1012 Lsun

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

– Is the major bulge building stage via starburst finished ?

– The mass relationship between SMBHs and their bulges may already be established ?

– The observation is difficult.





• The bright MAMBO detections: What we see

– The FIR emission significantly exceeds the quasar templates– Dust temperature: 40~60 K

– Given the 1013 Lsun FIR luminosity, the size of the FIR dust emission region is estimated to be a few kpc

=> Consistent with the size of the CO and C+ emission region.

– CO detections– Luminosity correlations

• FIR-to-radio emission consistent with typical star forming galaxies.

• LFIR – Lbol correlation: follow the trends defined by local IR quasars – likely to be the high mass counterparts.

• LFIR – LCO correlation.



star formation?• It is likely that active star formation is ongoing in

the host galaxies of the strong millimeter detected quasars at z~6.

– Star formation rate: ≥103 Msun yr-1.

– Star formation efficiency: comparable to ULIRGs and SMGs.

• Gas mass: ~1010 Msun, which will turn to stars via the massive starburst.

• If the quasar systems at z~6 follow the local black hole-bulge relationship, the mass of a mature stellar bulge should be ≥5x1011 Msun.

Discussion – the evolutionary stage of the Discussion – the evolutionary stage of the z~6 quasarsz~6 quasars

Discussion – the evolutionary stage of the Discussion – the evolutionary stage of the z~6 quasarsz~6 quasars

• We are seeing the end of the active bulge building in these strong mm quasars ? – The stellar bulge with a mass of a few 1011 to 1012

Msun already exist. • Require measurements of the bulge dynamical

mass.• Resolve the stellar bulge at near-IR wavelengths.

– Not yet; • Require gas supply from outside;• Rapid supper-massive black hole accretion occurs

prior to the formation of the stellar bulge.

Further observationsFurther observationsFurther observationsFurther observations

• CO and [C II] searches in all the z~6 quasars which have strong FIR excesses in the SEDs (PdBI, SMA)– The [C II] observation requires lots of time with the current

instrument (SMA). ALMA is a better place to go!

• CO excitation studies with new detections. (low-order CO transition with GBT, EVLA)– Need the frequency range of about 30 to 40 GHz -- Ka band of

the EVLA

• High resolution (<= 0.3’’) CO and dust mapping (PdBI, EVLA).– Extended FIR emission (a few kpc) associated with the

CO emission: star formation.– Compact FIR emission: AGN dust heating– High resolution CO mapping: the dynamical mass within

a few kpc.

SummarySummarySummarySummary

• The current sample of quasars at z~6 is studied at millimeter and radio wavelengths.

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

• Molecular CO has been detected in the brightest mm detections.

• We investigate the possible dust heating process, and star forming activities from the host galaxies of these object.

• We discuss the evolutionary stage of these z~6 quasars.

dust and molecular gas in the most distant quasars

Documents

discovery of z

lowz quasars

low z jiang

radio emissionthe

radio instruments

bright quasars

radio continuum survey

typical optical quasars