Star formation at high redshift (2 < z < 7)

Methods for deriving star formation rates

•UV continuum = ionizing photons (dust obscuration?)

•Ly = ionizing photons (dust obscuration?)

•Far IR = bolometric (covering factor?)

•Radio continuum (synchrotron) = empirical (radio – FIR correlation?)

•Radio free-free/RRLs = ionizing photons (sensitivity, spectral confusion?)

•All relate mostly to massive stars (> 5 M_sun) => total SFR depends on extrapolation of IMF, and temporal behavior

Cosmic (proper) time

Radio-FIR correlation: tightest correlation in

extragalactic astronomy

Separating FF – Synch is difficult

Synch.

Free-free

Thermal dust

M82

SKA in context

z=8

EVLA

Cosmic ‘background’: ½ starlight reprocessed by dust

Evolution of space density of luminous QSOs (Fan et al. 2003)

Madau-Lilly plot: evolution of cosmic star formation rate

density

Galaxy populations at high redshift (2 < z < 7)

•Radio galaxies: only z > 0.5 galaxies before 90’s

•UV dropouts/Ly-break: broadband colors

•Ly : narrow band imaging

•Submm: (sub)mm bolometer camera imaging

•QSO Hosts: HST, (sub)mm

•QSO absorption lines: metalicity evolution, parent galaxies

•z=0.3 to 2: EROs, faint blue, Butcher-Oemler, Jy radio sources, ISO

•GRB hosts

•Pop III stars: early reionization by 100 M_sun stars in minihalos at z = 20?

z = 5.2 2000

10kpc

High z radio galaxies (L_1.4 > 1e28 W/Hz)

10kpc

z=0.057 1954

z=0.49 1980

z=3.8 1990

K-z relation: HzRGs = Giant Ellipticals

z>8 radio galaxies?

Alignment effect: Jet-induced star formation?

Clumpy morphologies => forming ellipticals?

1138-262 z=2.2

Alignement effect: Radio-Xray

Radio-Lyhalo

18kpc

Clustering on Mpc scales around HzRGs (1138-262 z=2.2) => protoclusters?

Dusty radio galaxies at high z?

Overdensity of submm galaxies?

UV dropouts/Ly break (Ly

Star formation rates in Ly break galaxies

Extinction uncorrected

corrected

Correlation between extinction and SFR => L_UV is independent of SFR

Ly break galaxies = highly biased (ie. clustered) galaxy formation

Ly break galaxies with Ly halos

SUBMM galaxies: dust obscured galaxy formation

HDF - optical HDF – 850 m

Dust obscured star formation dominates at z>2?

Submm galaxies: L_FIR = 1e12 to 1e13 L_sun

=> SFR = 100 to 1000 M_sun /yr

M_dust = 1e8-9 M_sun

Magic of submm

350 GHz

250 GHz

Brightest mm source in HDF:

K = 23.5

Radio photometric redshifts: two

colors, or ‘drop-outs’

Redshift distribution

Next step: photometric redshifts

CO emission => M(H_2) = 1e10-11 M_sun

Submm galaxies

QSO host galaxies

•Most low z spheroidal galaxies have SMBH

•M_BH = 0.002 M_bulge

=> ‘Causal connection between SMBH and spheroidal galaxy formationn’ (Gebhardt et al. 2002)?

30% of luminous QSOs have S_250 > 2 mJy

L_FIR > 7e12 M_sun

Dust heating: starburst or AGN?

2322+1944

z=6.4 S_250=5.5mJy

Radio-to-IR SED = M82

CO(1-0) w. VLA:

L_FIR = 3e13 L_sun

M(H_2) = 1e11 M_sun

A Molecular Einstein Ring: VLA 45 GHz observations of CO2-1 emission from the gravitationally

lensed QSO 2322+1944 at z=4.12 (Carilli et al. 2003)

Keck Rband

VLA CO2-1

2”

Using the gravitational lens to probe sub-kpc scales in 2322+1944: A starburst disk surrounding a SMBH => coeval SMBH – galaxy formation?

Optical QSO

Starburst disk: molecular gas, dust, radio continuum

Starbursts in QSO host galaxies?•30% of luminous QSOs (M_B < -27) have L_FIR = 1e13 L_sun (independent of redshift)

•Z= 2 sample: All L_FIR luminous QSOs detected at 1.4 GHz, and in all cases ‘q’ consistent with star forming galaxy (2.3 +/- 0.3)

Questions

•Relationships between different high z galaxy types?

•Halos masses and end-products (spirals, ellipticals)?

•Is > 1000 M_sun/yr possible, sustainable (Heckman limit)?

•IMF: top heavy? Star formation in extreme environments (P=100xISM)? Timescales?

•Dust formation at z>6: >1e8 M_sun in < 0.7 Gyr?

•What fraction of high z galaxy formation is dust-obscured?

•Submm galaxies – redshift distribution?

•radio – FIR correlation: mechanism? vs. redshift?

•M- relation – coeval SMBH and galaxy formation?

•QSO dust heating: star formation or AGN?

•L_FIR from S_250?

•X = gas mass to CO luminosity conversion? L_FIR to dust mass conversion?

•Pop III stars, minihalos, and first luminous objects: role of radio astronomy?