Transcript Case for a high frequency SKA

Chicago III, Sept. 15, 2007
Washington DC
Chris Carilli (NRAO)
Thermal science at
centimeter wavelengths,
and more!
High Frequency (> 10GHz)
Laundry list of high frequency science with SKA
(what we lose without  >10GHz)
• First light: molecular line studies of the first galaxies**
• Cradle of life: Terrestrial planet formation and pre-biotic molecules
• Cosmology: Extragalactic water masers and measurement of Ho
• Testing GR: Pulsars in the Galactic Center
• SZ effect at 30GHz
• Molecular abs line systems and the variation of the fundamental constants
• Stellar masers (SiO, H2O) -- late stages of stellar evolution
• NH3
• Solar system thermal objects: atmospheres, surfaces, asteroids, KBO, comets
• Spacecraft tracking and telemetry at 32GHz: movies from Mars
• Stellar photospheres, winds, outflows
• FF/RRL -- HII regions, SuperStarClusters ….
**Key Science Projects
ALMA/EVLA CO redshift coverage
Epoch of Reionization:
Benchmark indicating
formation first luminous
Objects = Last frontier
First galaxies: standard
molecular transitions
redshift to cm regime
•Total gas mass
•Gas dynamics
•Gas excitation
•High density gas tracers
^2
ALMA z~10
Starbursts
CO Excitation
ladder
Normal
galaxies
Weiss, Walter, Downes, Henkel, in prep.
First galaxies -- Radio astronomy into cosmic reionization
z ~ 6 QSO host galaxies: molecular gas and dust
50K
FWHM=350 km/s
Radio-FIR
correlation
 Mdust ~ 1e8 Mo
Dust heating: star formation or
AGN?
Follows Radio-FIR correlation:
SFR ~ 3000 Mo/yr
z=6.42
VLA
PdBI
• Giant reservoirs of molecular gas ~2e10 Mo =
fuel for star formation.
• Currently: 2 solid detections, 2 likely at z~6
VLA
of CO3-2
VLAJ1148+52:
imaging of
gasimaging
at subkpc
resolution
0.4”res
rms=50uJy at 47GHz
1”
5.5kpc
0.15” res
 Not just circumnuclear disk.
 Separation = 0.3” = 1.7 kpc
 Can AGN heat dust kpc-scales
(geometry/rad transfer)?
 TB = 20K => Typical of
starburst nuclei
Gas dynamics: Potential for testing MBH - Mbulge relation
at high z -- only direct probe of host galaxies
1148+5251
z=6.42
Mdyn~ 2e10/(sin)^2 Mo
Mgas~ 2e10 Mo
Mbulge ~1e12 Mo
(predicted)
z<0.5
MBH = 0.002 Mbulge
[CII] 158um ISM gas cooling line at z=6.4
 C+ = workhorse line for z>6 galaxies with ALMA
30m 256GHz
Maiolino etal
 Structure identical to CO 3-2” (~ 5 kpc) =>
distributed gas heating = star formation?
 SFR ~ 6.5e-6 L[CII] ~ 3000 Mo/yr
CII PdBI Walter et al.
1”
CII + CO 3-2
Higher Density (>1e4 cm^-3) Tracers: HCN, CN, & HCO+,
HCN 1-0
HCO+ 1-0
Riechers
200uJy
•Cloverleaf (z=2.56) = SgrB2 of distant
galaxies
•Lines 5-10x fainter than CO
•ncr > 1e7cm^-3 for higher orders => higher
order not (generally) excited?
•Dense gas tracers best studied with cm
telescopes
CO vs. HCN: total vs. dense gas
1e13
FIR
Index=1.5
Index = 1
1e9
L’(CO)
• CO traces all molecular gas
(>100 cm^-3)
• SFR / total gas mass = star
formation efficiency, increases
with FIR luminosity.
L’(HCN)
 HCN traces dense gas (> 1e4 cm^-3)
 SFR / dense gas mass ~ universal in all
galaxies: ‘Counting star forming clouds’
Building a giant elliptical galaxy
+ SMBH at tuniv < 1Gyr
 Multi-scale simulation isolating most
massive halo in 3 Gpc^3 (co-mov)
10
10.5
Li, Hernquist, Roberston..
8.1
 Stellar mass ~ 1e12 Mo forms in
series (7) of major, gas rich mergers
from z~14, with SFR ~ 1e3 - 1e4 Mo/yr
 SMBH of ~ 2e9 Mo forms via
Eddington-limited accretion + mergers
6.5
 Evolves into giant elliptical galaxy in
massive cluster (3e15 Mo) by z=0
• Enrichment of heavy elements, dust starts early (z > 8): good
news for radio astronomy
• Extreme and rare objects: ~ 100 SDSS z~6 QSOs on entire sky
• Integration times of hours to days to detect HyLIGRs
The need for collecting area: pushing to normal
galaxies at high redshift -- spectral lines
cm telescopes: low order
molecular transitions
(sub)mm: high order
molecular lines + fine
structure lines
The need for collecting area: continuum
A Panchromatic view of galaxy formation
Arp 220 vs z
cm: Star formation,
AGN
(sub)mm Dust,
molecular gas
Near-IR: Stars,
ionized gas, AGN
The Cradle of Life (Wilner)
• image terrestrial planet
formation zone of disks
– grain growth to pebbles
– embedded protoplanets and
sub-AU tidal gaps
– Evolution ~ 1 year
Bryden 1999
• assess biomolecules
– disk abundances
– locations
Remijan et al. 2006
Terrestrial Planet Formation
• T Tauri, Herbig Ae stars: several l00’s of
proto-Sun analogs, d ~ 140 pc, age 1-10 Myr
– How do terrestrial planets form?
– How much orbital evolution (migration)?
– Is our Solar System architecture typical?
1.3 mm
• SKA: unique probe of disk habitable zone
– mas resolution: 1AU = 7mas at 140pc
– cm waves: avoid dust opacity
– very high sensitivity: thermal emission
• Complementarity
– ALMA: Chemistry, dynamics, dust on larger
scales
– Optical: scattered light
star
dust
SKA Sensitivity: thermal science at
mas resolution
• SKA 8hrs, 22GHz, 2mas (1500km) =>
S(rms) = 0.02uJy, TB(rms) = 11K
• flux density emitted by a disk element dA
TB ~ 50 to 300 K on AU scales
• less than an Earth mass in sub-AU beam at
140 pc distance of nearby dark clouds
Embedded Protoplanets
• protoplanet interacts tidally with
disk
– transfers angular mom.
– opens gap
– viscosity opposes
P. Armitage
QuickTime™ and a
YUV420 codec decompressor
are needed to see this picture.
• orbital timescales in habitable
zone are short (t ~ 1 yr)
• synoptic studies track proper
motions of mass concentrations
Bate et al.
1AU Gap ~ 100 K
Grain Growth and Settling
• detailed frequency dependence of dust emissivity
is diagnostic of particle properties, esp. size
• SKA sensitive to cm sizes, predicted to settle to
disk mid-plane and seed planetesimals -- sticky
question?
QuickTime™ and a
YUV420 codec decompressor
are needed to see this picture.
TW Hya
3.5 cm dust
Wilner et al
NASA/JPL R. Hurt
.
Cosmology -- Water maser disks
(Greenhill)
• Hubble constant through direct measurement of
distances to galaxies in the Hubble flow.
• Distance to NGC 4258 = 7.4 Mpc +/- 4%
-- maser acceleration and proper motion
-- problem: NGC 4258 is too close => Cepheid
calibrator
• Earth baselines => resolution > 0.4 mas => max.
distance ~ 120 Mpc
• Currently ~ 30 NGC4258-like masers known
• SKA: ~ 100x more sources, with adequate
sensitivity to image => easily 1% measure of Ho
Why do we need to
know Ho to 1% ?
w ~ 1 +/- 
0.13
Future 1% measures of
cosmological parameters via CMB
studies require 1% measure of Ho
for fully constrained cosmology:
covariance!
(w)
Current Ho constraint
0.09
Ho accur.
10%
4%
GR tests: Galactic Center Pulsars
(Cordes)
•Sgr A* = 3106 black hole with a surrounding
star cluster with ~ 108 stars. Many of these are
neutron stars.
•Detecting pulsars near Sgr A* is difficult
because of the intense scattering screen in front
of Sgr A*: d ~ 2000 ν-4 sec (but S  ^-3)
•Solution: high sensitivity at high frequency: >
10GHz => width < 0.2sec
Key science:
• Highest probability of finding binary BHpulsar: strong field GR tests and BH spin.
• Possibly 1000 pulsars orbiting Sgr A* with
orbital periods < 100 yr
• Detailed studies of GC ISM -- DM…
Summary and Ruminations
KSP
10% Big step?
Up to 45GHz? >1000km?
First light: mol. lines
Y
Y
N
Terrestrial planet
formation: PP disks
Y
Y
Y
Gal. Center Pulsars
Y
N
N
Cosmology: water masers Y
and Ho
N
Y
• SKA-High is not being pursued by international partners.
• SKA-High is most consistent with current work in USA
(EVLA, ATA, DSN).
Case for frequencies up to 45 GHz: Thermal objects
Rayleigh-Jeans curve
implies thermal objects
are a factor four
stronger (in Jy) at
45GHz relative to
22GHz => a 10%
demonstrator becomes
40% of the SKA-22,
Or EVLA at 45GHz ~
8% SKA-22GHz
demonstrator
0.1 x Arp220
25-50GHz
10% demonstrator
What we lose without 3 -- 10 GHz
• mas resolution -- Astrometry! Jets, AGN, XRBs
• GRBs, RSNe
• Methanol masers: massive star formation
• Large RM sources
• ms Pulsars with moderate DM
….
END