Download Scientific potential of interferometry from Space

ESA’s Darwin space
interferometer
Huub Röttgering
Sterrewacht Leiden
The InfraRed Space Interferometer
DARWIN
• 2014
• 6 1.5 m telescopes
• Hexagonal configuration
• Beam combiner
• Passive cooling (40 K): 5-20 micron
Overview
 Introduction
– Timeline / status project
– Relation with NASA’s Terrestrial Planet
Finder
 Imaging considerations
 Science
Ringberg, 5-Sept-2003
Imaging with Darwin
Page 3
Science
 Finding and characterising exo-Earth’s
– Nulling interferometry
Ringberg, 5-Sept-2003
Imaging with Darwin
Page 4
The Problem
 Detecting light from
planets beyond solar
system is hard:
– Planet emits few
photons/sec/m2 at 10 mm
– Parent star emits 106 more
– Planet within 1 AU of star
– Dust in target solar system
300 brighter than planet
 Finding a firefly next to a
searchlight on a foggy
night
Science
 Finding and characterising exo-Earth’s
–
–
–
–
Nulling interferometry
Atmosphere -> CO2
Wet and pleasant H20
Life O3 (? / !)
O3
CO2
H2O
Earth at 10pc
6
8
10
12
14
16
18
(mm)
 High resolution and sensitive IR imaging
– Cophasing using an off-axis reference star
Ringberg, 5-Sept-2003
Imaging with Darwin
Page 6
Darwin timeline
 1993: Léger et al
– ``Darwin proposal’’
 2000 Presentation Alcatel system level study
 2004 Results significant technology development
program (15 Meuro)
– Optical components, coolers, thrusters, metrology,
control software, 2 breadboards …
 2007 – SMART2 techno demonstration flight
– (mainly LISA technology)
 2010 – SMART3 techno demonstration flight
– 2-3 space craft
 2014 – launch
Ringberg, 5-Sept-2003
Imaging with Darwin
Page 7
NASA’s TPF
 Similar goals and timelines
1999:
IR interferometer with
cooled 4x3.5 m
mirrors and ~75-1000
m baseline
Ringberg, 5-Sept-2003
Imaging with Darwin
Page 8
Vegetation edge
2000
Blue sky
Earth
spectrum
from
Earthshine
2001: 4 different studies
Variable-Pupil Coronagraph
IR Nulling Interferometers
SVS
coronagraphe
M2
M1
M3
Large Aperture IR Coronagraph
Hyper-telescope
2002: down selection for 2 concepts
•Coronagraph – Difficult
•10-15 meter mirror with rms surface
~< 1 Å
–Deformable mirrors - control to <1 Å rms
over wide range of scales
Variable-Pupil Coronagraph
–Wavefront sensing - adequate for <1 Å
control
•Interferometer - Complex
–Cryogenic nulling - 10-5 or 10-6 depth
across ~1 octave
–Wavefront & amplitude control - spatial
filter in mid-IR (+ DM for low spatial freqs)
+ control of thermal & vibration effects +
acc. amplitude measurement
IR Nulling Interferometers
–Beam transport issues (rejection of stray
light at small angles)
Joined ESA/NASA mission
 MOU: aims for a joining in 2006
 Plan
– Both sides continue technical studies
– Regular scientific contact
– Criteria to guide continuation after 2006
•
•
•
•
•
•
Ringberg, 5-Sept-2003
#1:
#2:
#3:
#4:
#5:
#6:
Sensitivity in finding and characterizing exoplanets
Richness of astrophysical science opportunities
Technology development needed
Life-cycle costs
Risk of cost, technology, schedule, on-orbit failures
Reliability and robustness
Imaging with Darwin
Page 12
Astrophysical imaging with
Darwin
1. Imaging considerations
2. Science
Röttgering et al. 2003, Heidelberg conference
Ringberg, 5-Sept-2003
Imaging with Darwin
Page 13
Imaging performance at 10 micron
 Sensitivity (Takajima and Matshura, 2001)
• Limited by shot noise from the zodiacal background.
• Similar to JWST
– Point source sensitivity
• 1 hour, s/n=5: 2.5 microJy
– Image sensitivity
• S_integrate/noise > 50 within FOV
• > 2.5 microJy for a 100 hour
 Resolution
– Baselines up to 500 meter
– 200 m baseline: 10 mas
• JWST 350 mas
Ringberg, 5-Sept-2003
Imaging with Darwin
Page 14
Imaging considerations
 PSF of an individual telescope: 1.4 arcsec
– = maximum FOV for pupil combination
 Mapsize (200 m baseline/telescope diameter)
<~ 100 * 100 independent pixels
 Complexity
– per configuration maximum 6*5/2 = 15 uv points
– number of uv-points >>~ number of image parameters
– for a complex map of 100 * 100 independent pixels:
• >>~ 666 configurations
Ringberg, 5-Sept-2003
Imaging with Darwin
Page 15
1
6
Baseline dynamics
Basic reconfiguration approach
a single expansion up to baselines
of 500 m and contraction
coupled to a 60o rotation
d’Arcio et al. 2001
bang-bang thrust profile both
radially and tangentially
<dB/dt> = 1.5 cm/s @ 1 mN
Fastest reconfiguration cycle takes about 16 hours
Snapshots will be taken “on the fly”
Ringberg, 5-Sept-2003
Imaging with Darwin
Page 16
1
7
UV coverage
Hexagonal array -> 9
independent visibilities per
snapshot
600 snapshots, ~ 5400 uv
points/reconfiguration cycle
d’Arcio et al. 2001
Ringberg, 5-Sept-2003
-> Filling the UV plane is
’’easy’’
 Ground based telescopes
are ``fixed’’
 (radio) Baseline/aperture is
huge
Imaging with Darwin
Page 17
Issue: Cophasing

How to phase-up the array not using the target?
–
Essential to
•
•
–
Off-axis bright stars (there are enough!)
•
•
–
integrate longer than the coherence time of the interferometer
(~10 sec)
Measure complex visibilities (Amplitude and phase) needed for
imaging
Similar to PRIMA instrument for the VLTI (Quirrenbach, this
meeting)
Multiplexing in wavelengths has the advantage that science and
reference beams travel along common path (Alcatel)
Implementation
1. Modification to the nulling beamcombiner (Alcatel)
2. Separate imaging beamcombiner
Ringberg, 5-Sept-2003
Imaging with Darwin
Page 18
 How to get a large Field of
View?
– Mosaicing
Light from
telescope
Light from
telescope
positioning stages
Lo
(fixed)
– homothetic mapping
• Relative complex
• Pupil matching in
magnification and
orientation before image
Afocal zoom
plane combining
optics (5-50x)
• Implementation
imaging
telescope
Zoom optics
(5-50x)
4kx4k detector
conventional
pupil mapping
• Expensive in time
variable
magnification
– Pupil
matching/zooming
optics at central
beamcombiner
– Pupil
matching/zooming
at telescopes
(see d’Arcio and
le Poole, 2003)
 Physical processes
observable at 6-20 micron
– Molecules: Rotational and
vibrational lines
• Temperatures, densities,
kinematics, Chemistry
– Ions: Forbidden finestructure lines
• Temperatures, densities,
kinematics, abundance's
ISO observations
Starburst galaxy
Circinus
– Dust: PAH features,
continuum shape
• Composition, temperature
– Late type stars: continuum
(high z)
• Spatial scales
Appropriate sensitivity and
angular resolution ?
Star and planet formation
AGN
Distant galaxies
Ringberg, 5-Sept-2003
Imaging with Darwin
Page 21
Star and Planet formation
 Sketch of scenario maybe in
place (Shu et al. 87)
 Vast range of conditions and
relevant timescales
– densities 10^4 - 10^13 /cm^3
– temperatures 10 - 10,000 K
– month - 10^6 years
 Issues
– density, temperature and
dynamical structure of disks?
– At what stage and when do
planets form?
Compendium of Monnier and Millan-Gabet of K-band sizes of YSOs
Disk models of D’Alessio, Merin
ISOCAM survey of your starclusters at 6.6 and 14.3 micron (Eiroa et al)
Log Radius[mas]
4
An unphysical, unrealistic extrapolation
-> fainter YSO are small
(10-100 mas ?)
MIDI
2
Darwin
0
-2
-1
Log flux @ 14 micron [Jy]
0
Active galactic Nuclei




Ringberg, 5-Sept-2003
Zoo: Seyfert, Starburst
quasars ...
– unification: orientation,
time-evolution, mass,
spin
1000 times more AGN at
z=2 than z=0
Every galaxy has a central
massive Blackhole (?)
Issues:
– Physics? When and how
do BH form?
– Relation to Galaxy
formation?
Imaging with Darwin
Page 25
Models of Tori of Granato et al.
 AGN may contain dusty tori
– can obscure the central
QSO
– feeds the massive Black
Hole
 Radiative transfer model of a
dusty torus
– size scales with QSO
luminosity
– SED from  = 1 - 300 mm
– morphologies at = 10 mm
Adapted to NGC 1068, Heijligers etal.
Ringberg, 5-Sept-2003
Imaging with Darwin
Page 26
Ln (10 m m [1030 erg/s/Hz]
Darwin observations of Tori
 D = 300 times the sublimation
radius
 NGC1068:
1’’
– Bight, low luminosity nearby
AGN
0.1’’ NGC1068
• 1.7 1031 erg/s/Hz at  = 10 mm
50 m Jy
– (prime target for MIDI/VLTI
in 2003)
5 m Jy
0.01’’
0.01
• ~10 Jy: prime target for
MIDI/VLTI in 2003
0.1
1
redshift
10
 Weak AGN observable up to z = 1
-2
 Stronger AGN up to z = 10
Distant Galaxies
 When and how do galaxies form?
– Star formation history, galaxies shapes
– Relation to black hole formation
 8-10 meter telescopes: a few thousand with 3<z<6 and
still counting
– Hardly morphological information
 Darwin: morphologies of the older stellar component
– observe 2 micron rest == 10 micron for z=4
 Semi-analytical models of galaxy formation as guidance
– input: evolution of cold-dark matter halos, prescriptions for
cooling, star formation and feedback, dust…
– output: large samples of mock galaxies and their properties
(SF, mass, type)
 FIRES survey
 IsaacVLT
 : 2.5^2 arcmin
 96 h in J, H, K
HDFS
 limit in K = 24.4
mag
 Image HST I+H+K
 Franx, Labbe,
Forster,schreiber,
Rix, Rudnick,
Röttgering, etal.
SED fitting
with galaxy templates
•Photometric redshift
•Estimate 10 micron
flux density
Rudnick, Labbe et al.
Ringberg, 5-Sept-2003
Imaging with Darwin
Page 30
JWST resolution
At 10 micron
(0.35 arcsec)
Ringberg, 5-Sept-2003
Imaging with Darwin
Page 31
Fn (10 m m ) m Jy
100 hour,
S_int/noise=50
100 hour
Pointsource
S/N=5
(photometric) redshift
Ringberg, 5-Sept-2003
Imaging with Darwin
Page 32
Conclusion
 Darwin will be a powerful instrument for
– Finding and characterizing exo-Earth
– Astrophysical studies
 Sensitivity is similar to JWST
– Cophasing is an important issue
 Size scales, AGN, YSOs, distant galaxies
are appropriate
– Case for larger fields
Ringberg, 5-Sept-2003
Imaging with Darwin
Page 33
2025
Terrestrial planet imager?
20 8-m telescopes