Transcript The Transient Radio Sky Astrophysical and Artificial

Star formation at high redshift (2 < z < 7)
Methods for deriving star formation rates
•UV continuum = ionizing photons (dust obscuration?)
•Ly a = 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
M82
Synch.
Free-free
Thermal
dust
SKA in context
EVLA
z=8
Cosmic ‘background’: ½ starlight reprocessed by dust
Madau-Lilly plot: evolution
of cosmic star formation rate
density
Evolution of space density of
luminous QSOs (Fan et al. 2003)
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 a: 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, mJy radio sources, ISO
•GRB hosts
•Pop III stars: early reionization by 100 M_sun stars in minihalos at z = 20?
High z radio galaxies (L_1.4 > 1e28 W/Hz)
z=0.057 1954
z=3.8 1990
10kpc
10kpc
z=0.49 1980
z = 5.2 2000
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
18kpc
Radio-Lya halo
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 a)
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 a halos
SUBMM galaxies: dust obscured galaxy formation
HDF - optical
HDF – 850 mm
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 ‘dropouts’
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)?
z=6.4
2322+1944
30% of luminous QSOs have S_250 > 2 mJy
L_FIR > 7e12 M_sun
Dust heating: starburst or AGN?
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-s 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?