VSI / MATISSE - astrophysik.uni-kiel.destar/Kiel2010/Circumstellar_Disk... · 26-28 May, 2010 - University of Kiel. Perfect combination of observing wavelength (~10µm) ... UTs. Required

VSI / MATISSE

Sebastian WolfUniversity of Kiel, Germany

Circumstellar Disks and Planets – Science cases for the second generation VLTI instrumentation26-28 May, 2010 - University of Kiel

Perfect combination of observing wavelength (~10µm) and spatial resolution (VLTI baselines 10-20mas)

regions with hot dust can be spatially resolved

since 2002observations of the hot dust in circumstellar disks, AGB stars,

winds of hot stars, massive star forming regions, tori of AGNs, debris disks, solar system objects

Results:Very successful in interferometric spectroscopy(chemical composition of dust on different spatial scales)

Concept of mid-infrared long-baseline interferometry proven to work

but …

MATISSE[The Progenitor: MIDI]

MIDI

a) Small number of visibility pointsb) Lack of Phase Information

Investigation of small-scale structures (= main goal of MIDI) and quantitative analysis of spectroscopic observation strongly limited

c) Interpretation of MIDI data:Comparison between modeled and observed visibility points,

using 2D models with point-symmetry (usually even rotation symmetry)

Approach justified only by large-scale (if at all existing) symmetries, but expected to be strongly misleading or simply wrong

on size scales investigated with MIDI

MATISSE[MIDI’s limitations]

MIDI

[MIDI] Mid-IR Interferometry

Schegerer, Wolf, et al., 478, 779, 2008, „The T Tauri star RY Tauri as a case study of the inner regions of circumstellar dust disks “

Schegerer, Wolf, et al. 2009, A&A, 502, 367 „Tracing the potential planet-forming region around seven pre-main sequence stars“

Mid-Infrared Interferometric Instrument (MIDI)

Spatial resolution: λ/B ≥ 1AU @ 140pc with B ≤ 130m

Spectrally resolved (R=30) data in N band:• Silicate feature + (relative) radial distribution• Inner disk region ≤ 40 AU

General results(1) SED (global appearance of the disk) + spectrally

resolved visibilities can be fitted simultaneously(2) Best-fit achieved in most cases with

an active accretion disk and/or envelope(3) Decompositional analysis of the 10µm feature

confirms effect of Silicate Annealing in the inner disk (~ few AU)

Limitation of 2-beam interferometers[Example]

True surface brightness profile in circumstellar disks around TTauri / HAe/Be stars

Two-telescope interferometers: “mean” disk size & approximate inclination of the diskAssumption: Iso-brightness contours are centered on the location of the central star

Simulated 10μm intensity map of the inner 30AU×30AU region of a circumstellar T Tauri disk at an assumed distance of 140 pc; inclination angle: 60◦.

Left: VISIR false-color image of the emission from the circumstellar material surrounding the HAe star HD97048. The emission is widely extended, as compared with the point spread function (inset) obtained from the observation of a pointlike reference star. Right: Same image as in the middle, but with a cut at the brightness level and a fit of the edge of the image by an ellipse (Lagage et al. 2006).

Goal: Thermal reemission images with an angular resolution of 0.003“

MATISSE @ Very Large Telescope Interferometer

Multi-AperTure Mid-Infrared SpectroScopic Experiment

2nd generation VLTI beam combiner• L, M, N bands: ~ 2.7 – 13 µm• Improved spectroscopic capabilities:

Spectral resolution: 30 / 100-300 / 500-1000• Simultaneous observations in 2 spectral bands

MATISSE

Successor of MIDI:Imaging capability in the entire mid-IR accessible from the ground

Extension to AMBER / VSI:Extension down to 2.7µm + General use of closure phases

Complement to ALMA + TMT/E-ELT

Ground Precursor of DARWINWavelength range 6-18µm

Multi-AperTure Mid-Infrared SpectroScopic Experiment

High-Resolution Multi-Band Image Reconstruction+ Spectroscopy in the Mid-IR

MATISSE[overview]

Key features

• Imaging in N band

(general use of closure phases)

• L&M band extension

(simultaneous observations in L&M and N band)

Science Cases for MATISSE

1. Star and Planet Formation

2. Evolved Stars

3. Solar System Minor Bodies

4. Extrasolar Planets

5. Active Galactic Nuclei

6. Galactic Center

MATISSE[in context]

MATISSE[requirements / observing strategy]

Requirements: Spectroscopic Resolution

Number of Combined Beams

2/3 T Mode : Highest sensitivity measurements; Preparatory studies

4 T Mode : Image reconstruction and Model fitting studies

Observing Strategies

a) Image reconstruction mode (3-5 nights)

b) Model fitting mode (single measurements)

~

MATISSE[ATs / UTs]

ATs

Goal Image reconstruction

Requirement Optimized coverage of the u-v plane

Consequence Majority of key science programmes must be executable using the relocatable Auxilliary Telescopes (ATs)

UTsRequired to reach the sensitivity limits demanded by selected science programmes

(e.g. AGNs)

MATISSE[Performance goals]

Ultimate correlated flux sensitivity

Accuracy

Maximum spatial resolution

selected science cases

(in the field of star and planet formation)

Size ScalesSolar System

Angular diameter of the orbits of selected Solar System planets as seen from the distance of the nearby star-forming region in Taurus (140pc) :

Neptune - 0.43” Jupiter - 0.074”Earth - 0.014”

What is possible? – TODAY

AMBER / VLTI ~ a few mas [near-IR]MIDI / VLTI ~ 10 – 20 mas [N band: ~8-13µm]SMA ~ 0.3” (goal: 0.1”) [~submm]

Size scales

IRAS 04302+2247 „Butterfly Star“

Size ScalesSolar System

Angular diameter of the orbits of selected Solar System planets as seen from the distance of the nearby star-forming region in Taurus (140pc) :

Neptune - 0.43” Jupiter - 0.074”Earth - 0.014”

What is possible? – WITHIN THE NEXT DECADE (examples)

VSI / VLTI ~ a few mas [near-IR]MATISSE / VLTI ~ 3 – 20 mas [L/M/N bands: ~3-13µm]ALMA ~ 20 mas [~submm]

Size scales

IRAS 04302+2247 „Butterfly Star“

4-6 telescopes;image reconstruction

AB Aurigae

Spiral arm structure: H band(Herbig Ae star; Fukagawa et al. 2004; SUBARU)

Distance: ~140 pc

MATISSE[Exemplary science case]

Low/Intermediate mass star formationPlanet formation

Complex outer disk structure observed

Complex inner disk structure expected

FU Ori outbursts -- Variability in general (flux, polarization),

Expected influence from the formation of Jets/Outflows

AB AurigaeAsymmetry (Color: 24.5µm, Contours: H Band)

(Herbig Ae star; Fujiwara et al., 2006, SUBARU)

Distance: ~140 pc







AB AurigaeSpiral (345 GHz, continuum)

(Herbig Ae star; Lin et al., 2006, SMA)

Distance: ~140 pc







evolution of the planet-forming region

Example #1 HH30

[Guilloteau et al. 2008]

Observation• IRAM interferometer, 1.3mm, beam size ∼0.4”

Result• Disk of HH30 is truncated at an inner radius of 37 ± 4 AU

Interpretation• Tidally truncated disk surrounding a binary system (two stars on a low eccentricity, 15 AU semi-major axis orbit)

• Additional support for this interpretation: Jet wiggling due to orbital motion

• The dust opacity index, β ≈ 0.4, indicates the presence of cm size grains (assuming that the disk is optically thin at 1.3mm)

Example #2 Disk in the Bok Globule CB26

[Sauter et al., 2009]

Observations considered

• HST NICMOS NIR imaging• (Sub)mm single-dish: SCUBA/JCMT, IRAM 30m• Interferometric mm cont. maps:SMA (1.1mm), OVRO (1.3/2.7mm)• SED, including IRAS, ISO, Spitzer

Inner disk radius: ~ 45 AU

constraints on radial + vertical disk structure in the potential planet-forming region (r~80-120AU)

1360µm

894µm

[Wolf et al. 2008]

Example #3 The Butterfly Star in Taurus

Example #4 Face-on disks

• AB Aurigae (Lin et al. 2006)Emission gap observed in gas and dust distribution

• GM Aurigae (Dutrey et al. 2008)Inner disk radius: 19 +/-4 AU

Example #4 Face-on disks

340 GHz dust continuum images of LkHα 330 (top), SR 21N (middle), and HD 135344B (bottom).The crosses mark the literature coordinates of the central star.

[Brown et al. 2009]

rin=27AUrin=37AU rin=40AU

MATISSEDisk clearing

10µm image of a circumstellar disk with an inner hole; radius 4AU (inclination: 60°; distance 140pc;

inner 60AU x 60AU)

Sublimation radius ~ 0.1-1AU (TTauri HAe/Be stars)

but:

Observations: Significant dust depletion >> Sublimation Radii

TW Hydrae : ~ 4 AU (Calvet et al. 2002)

GM Aur : ~ 4 AU (Rice et al. 2003)

CoKu Tau/4 : ~10 AU (D’Alessio et al. 2005, Quillen et al. 2004)

[ MATISSE Science Cases ]

Planetary signatures in the near-IR?

Artist impression of the disk around LRLL 31. A planet in the innermost regioninfluences the disk to cast a large shadow on the outer region. The orbit of theplanet, and thus the shadow, causes the disk to be variable in the nearinfrared on timescales on the order of one week. Picture credits: NASA.

ObservationVariability of T Tauri stars

on time scales < 1 year

Various interpretations• Clumpy inner circumstellar shell/disk structure

• Variable stellar accretion rate⇒ variable net luminosity⇒ variable inner disk structure / disk illumination

• Embedded stellar or planetary companion => dynamical perturbation (short-term)

Example Transitional disk LRLL 31 in the 2-3Myr old star-forming region IC 348: Variations of the near-IR and N band spectra on a few months timescale[Muzerolle et al. 2009]

Observational basis: Spitzer/IRS 5-40µm observations, 6 months (Houck et al. 2004); further Spitzer/MIPS observations (Muzerolle et al. 2009) + SpeX/IRTF, SPOL (Spectro-polarimeter; Steward observatory) spectroscopic measurements

tracing planets in young disks

Disk-Planet Interaction

0.01MJ

0.1MJ

1MJ

0.3 MJ

0.03 MJ

0.01 MJ

(Bate et al. 2003)

1Msun star

1 MJ

ALMA: Gaps

Jupiter in a 0.05 Msun disk

arounda solar-mass star

as seen with ALMA

[ Wolf et al. 2002 ]

d=140pc

Baseline: 10km

λ=700µm, tint=4h

Planetary Accretion Region

[ D’Angelo et al. 2002 ]

[ Wolf & D’Angelo 2005 ]

Density Structure

Stellar heating

Planetary heating

Prediction of Observation

Proc

edur

e

Close-up view: Planetary Region[ Wolf & D’Angelo 2005 ]

Maximum baseline: 10km, 900GHz, tint=8h

Mplanet / Mstar = 1MJup / 0.5 Msun

Orbital radius: 5 AUDisk mass as in the circumstellar disk around the Butterfly Star in Taurus

50 pc

100 pc

Random pointing error during the observation: (max. 0.6”);Amplitude error, “Anomalous” refraction;

Continuous observations centered on the meridian transit;Zenith (opacity: 0.15); 30o phase noise;

Bandwidth: 8 GHz

Influence on SED?

[ Wolf & D’Angelo 2005 ]

Planet

Planetary Environment

Inner Disk Planetary radiation significantly affects the dust reemission SED only in the near to mid-infrared wavelength range.

This spectral region is influenced also by the warm upper layers of the disk, the inner disk structure, and the planetary contribution.

Planetary Contribution / Disk reemission (within the inner 12 AU ~ 0.1” in Taurus) < 0.4%

(depending on the particular model)

The presence of a planet + its basic characteristics (temperature, luminosity)

cannot be derived from the SED of the disk alone.

Complementary Observations: Mid-IR

Hot Accretion Region

around the Planet

inclination: 0° inclination: 60°

10µm surface brightness profile of a T Tauri disk with an embedded planet

(inner 40AUx40AU, distance: 140pc)

[ Wolf et al. 2007 ]

High Resolution!

Requirement

MATISSE – Planets

[ Wolf et al. 2005-2007 ]

Hot Accretion Region

around the Planet

inclination: 0°

Shocks & MRI

Strong spiral shocks near the planet are able to decouple the larger

particles (>0.1mm) from the gas

Formation of an annular gap in the dust, even if there is no gap

in the gas density.

(PaardeKooper & Mellema 2004)

MHD simulations - Magnetorotational instability

• gaps are shallower and asymmetrically wider

• rate of gap formation is slowed

Observations of gaps will allow to constrain the physical

conditions in circumstellar disksLog Density in MHD simulations after 100 planet orbits for planets with relative masses of q=1x10-3 and 5x10-3 (Winters et al. 2003)

Gas Dust

Shadow – Astrometry

Conditions for the occurrence of a significantly large / strong shadow still have to be investigated

[ Wolf & Klahr, in prep.]

Space Interferometry Mission (SIM)

Wavelength range0.4-0.9µm

Baseline: 10m

Narrow Angle Field: 1°

Narrow Angle Astrometry1µas mission accuracy

StrategyCenter of Light Wobble

[ G. Bryden, priv. comm.]

K band, scattered light

5 AU

Giant Planets in Debris Disks

• Decreased Mid-Infrared SED

[ Rodmann & Wolf ]

Planet Resonances and gravitational scattering

Asymmetric resonant dust belt with one or more clumps, intermittent with one or a few off-center cavities

+

Central cavity void of dust.

• Resonance Structures: Indicators of Planets

[1] Location

[2] Major orbital parameters

[3] Mass of the planet

[ Wolf & Hillenbrand 2003, 2005 ]

www1.astrophysik.uni-kiel.de / dds

Scattered Light Image

Young binaries

Binaries are the rule and not the exception• Nearby solar-type main-sequence stars show that about 53% of the stars are binary or multiple

systems• Taurus-Auriga star forming region: 80-100% (Ghez et al. 1993; Leinert et al. 1993; Reipurth &

Zinnecker 1993)

Science Cases• Gap between the close binaries detected by spectroscopic measurements and the companions at

larger separations detected on single dish telescopes by imaging with adaptive optics or by speckle interferometryMATISSE: Can close the gap

• Dynamical mass determination: Calibration of pre-main sequence evolutionary models• Characterization of infrared companions• Evolution of young binary systems

(Note: binary /= two independent stars)• Circumbinary disks: Structure, Alignment

The ‘miniclusters’ UZ Tau (the sources are separated by 0.4 and 3.6 arcsec) as seen in the Ks band with

NAOS/CONICA at the VLT.

High-mass star forming regions are much more distant (in average)than those of low-mass stars (high-mass: 3-7kpc vs. low-mass: 0.1-0.3 kpc)

JHK composite of NGC 3603 from ISAAC data, dimension 25'' x 25''

OB stars- form preferentially in the centre of dense star clusters- seem to live pref. in (tight) binary and higher order systems

The Orion BN/KL region at 12.5µm,dimension 10'' x 10'' (distance 450 pc)

[Shuping et al. 2004]

High number density of objects

Enhanced outflow activity

Strong stellar winds from the massive stars after ignition

Massive Star Formation

Observations in different bands

• … trace regions with different characteristic temperatures / physics / chemistry

• … provide image with different spatial resolution

• … allow a comparison with lower-resolution images obtained at large telescopes with adaptive optics – tracing the large scale structure of the targets – in different wavelength regions (L/M: NACO, N: VISIR)

L M N

Multi-wavelength imaging

Depending on the individual band

• … unique spectral features (dust/gas) are accessible

• … spectral features can be investigated that correspond to dust species which can also be observed in N band

Spectroscopy[Dust]

L band

• H2O ice broad band feature (2.7-4.0µm)

• PAHs: 3.3µm, 3.4µm

• Nanodiamonds: 3.52µm

• Highest Sensitivity in the MIR (reduced background emission)

M band

• CO fundamental transition series (4.6-4.78µm)

• CO ice features (4.6-4.7µm)

• Recombination lines, (e.g., Pfβ at 4.65µm)

Spectroscopy[Gas]

Prominent gas/dust features

Dust / Gas spectroscopy: Applications

• Mineralogy of proto-planetary disks– Dust grain coagulation– Modification in innermost (hottest) disk regions (silicate annealing), Radial mixing

• Environment of massive stars– Spatial distribution of CO, H2O ice– CO absorption lines: Distribution of warm / cold gas– Pfund β and Br α emission lines (?): Disk kinematics

M–band spectrum of the massive star forming region W33A (taken from Pendleton et al. 1999) as a compelling example for the occurrence of the 4.62 μm feature commonly attributed to OCN−.

Note: While this solid state feature is present toward several massive YSOs, W33A is an extreme example where it attains an even larger optical depth than the neighbouring CO ice feature at 4.67 μm.

FWHM(W33A) @ 8µm: 30mas [Wit et al. 2007]

MATISSE in the context of Star and Planet formation

Star and Planet FormationLow-mass Star and Planet FormationMineralogy of proto-planetary disks, dust grain growth and sedimentationTransitional objects: Status of inner disk clearingNature of outbursting young stellar objectsBinary mode of star formation: Inner structure and conditions for planet formation in circumbinary vs. circumstellar disks. Disk alignment.Characteristic structures in disks: Tracing giant proto-planets

Late stage of planet formation - Debris disksPlanetesimal collisions and exo-comets evaporation, grain properties and disk geometry.Complex spatial inner disk structure – direct indicators for the presence of planetsCharacterization of Darwin/TPF targets

Massive Star Formation: Link between low and high-mass star formation?Search and characterization of accretion disks around young massive (proto)starsSpatial distribution of the gas (carbon monoxide and hydrogen) and dust (silicates/graphite and CO ice) in the typically complex and distant high-mass star-forming regions

Summary

Phase-referenced imaging

Phase-referenced imaging allows one to reconstruct

∼ 4× fainter targets than closure-phase imagingPhase-referenced imaging can yield acceptable reconstructions of the T Tauri disk (∼ 90 masdiameter) down to a flux of 5.7 Jy (restoration error ∼ 21%), and closure-phase imaging can yield acceptable reconstructions down to a flux of 19.7 Jy (restoration error ∼ 15%).

∼ 1.5−2× larger targets than closure phase imaging.Reconstruction of T Tauri disks (average SNR ≈ 20 of the squared visibility) up to diameters of 180-210 mas (restoration errors ∼ 28-42%), and closure-phase imaging can reconstruct disks up to a diameter of 120 mas (restoration errors ∼ 16%).

VSI: VLTI Spectro-Imager

Second generation general purpose VLTI instrument

Near infrared• Immediate access to emission/absorption lines that probe the gas in a wide variety of conditions

and chemical states• Sublimation temperatures of dust peaks in the NIR

Full use of existing infrastructure• Eight telescopes and six delay lines are currently installed at Paranal • Use of 4T at a time can provide excellent science, but the full use of the existing infrastructure is

the key to maintain VLTI as the top optical interferometric facility in the world.

Complementarity• Imaging capabilities / High angular resolution:

Highly complementary to both the AO imaging instrumentation available at the VLT but also to ALMA imaging

• Spectral resolutions: considerable overlap with existing VLT instrumentation (which have much coarser angular resolution)

• Complementary to MATISSE: Probes the inner dust sublimation surface as well as the gas motions, while MATISSE probes the outer “colder” dust


Instrument design:

ImagingYoung star disks and winds; Evolved stars; Stellar surfaces; AGN torus.

High dynamic range imagingDebris disks.

Parametric visibilitiesBinaries, AGN BLRs and massive black holes.

High dynamic range parametric visibilitiesExtrasolar planets.

PRIMA operationAdditional science in AGN torus, BLR and massive-black holes

Target of opportunity + PRIMAMicrolensing (additional science)


Scientific requirementsSpectroscopic requirements. lowest resolution: 20 … 100.. intermediate spectral resolution: 1500–2500. high spectral resolution: 12000.

. lower scientific priority: mode with spectral resolution of 5000 is recommended.

. On average the spectral position of each pixel should be determined with an error no lessthan 0.20 of the pixel wavelength width

. lowest boundary of accessible instrument wavelengths: 1.08 μm.

. accessible J band in intermediate spectral resolution: at least 1.08 μm as its lower limit.

. K band accessible to the instrument should range from 1.95 μm to 2.37 μm; ideally upto 2.40 μm.

. spectral bands (J, H or K) does not necessarily have to be observed simultaneously.


Scientific requirementsFringe tracker requirements

. A fringe tracker is required for the science case.The fringe tracker can operate at a different band than the science channel, except for the Kband. A mode where part (exact amount TBD) of the K band light is used to fringe trackand part to do science should be available.

. The fringe tracker design should be driven by sensitivity.

. Interesting additional science would be allowed if the fringe tracker could fringe track onone of PRIMA’s dual beams, the other being reserved for the science channel.


Scientific requirementsImaging requirements

. Telescope positions should remain fixed during the night.

. An imaging mode where three different combinations of four telescopes (3 x 4T) are availablewithin a time-span of weeks, is required.

. An imaging mode where the simultaneous combination of six telescopes (6T) is available in asingle night, would open new and unique science.

PRIMAThe star separator systems and differential delay lines of PRIMA allows off-axis fringe tracking


Selected science casesYoung disks• Physical properties of the inner disk, Structure of gas / dust disk• Inner rim structure• Presence of planetary companion

• Disk census in star-forming regions

• Time-dependent phenomena:– VSI angular resolution of 1 mas => keplerian radius of 0.15 AU at 150 pc => keplerian period:

11.5 days => Disk evolution on timescales of weeks.

Complementary observations:Sub-mm interferometers (PdBI, ALMA): Cold, outer disk regions; different dust properties and different emission linesMATISSE:Obtaining images of protoplanetary disks at multiple infrared wavelengths will enable a global picture of these objects


Reconstructed images: Case studies:[1] YSOs

3x4T [MIRA reconstruction]



Reconstructed images: Case studies:[1] YSOs

3x4T [BSMEM reconstruction]



Selected science casesMultiplicity of young stars

Is the frequency of companions within 5AU of YSOs consistent with that observed amongnearby field stars or substantially higher, as for wider systems?

Among multiple systems, what is the frequency of quadruple and high-order systems and dothey show evidence of past dynamical re-arragements?

Are there some significant trends regarding this restricted multiplicity rate as a function ofstellar mass, age and/or environment?

Can the physics of core fragmentation and/or subsequent internal rearrangements account forthese differences? Alternatively, do these companions form through a distinct mechanism?


Selected science casesExoplanets

Observation of hot Jupiters in J, H and K bands, with a low (R ~100) or medium (R ~1000) resolution.

Model fitting of low-resolution spectra => of their albedo and test the cloud-free assumption

Phase dependence of the measured signal shall constrain the heat redistribution (through the temperature across the surface) and the weather conditions.

At medium resolution: Measurement of the abundance of CO, testing of the presence of CH4

Approach: Differential closure phases:Hot Jupiters are very close to their parent star:In the wavelength domain of VSI, common hot Jupiters have a typical contrast of 10−4 and the best

targets reach a contrast of 10−3

Reconstructed images: Case studies:[3] Microlensing

VSI: VLTI Spectro-Imager1x6T(?) [MIRA reconstruction]

1x6T(?) [BSMEM reconstruction]


Selected science casesDebris disks

Inner disk structure => indicative for embedded planets (planet/disk interaction)

Large survey to detect the presence of close-in dust down to a meaningful density level and derive statistics for this phenomenon

• Occurrence rate as a function of various stellar parameters. These mainly include age and spectral type, but also metallicity. Further parameters could be added to the list. One could investigate, for example, correlation with stellar rotation, which is closely related to the angular momentum budget of planetary systems

• Possible correlation with the presence of cold excesses. Statistical information on excesses across the spectrum — from near-IR (VSI) to sub-mm (SCUBA/SCUBA2) would allow one to better constrain the overall spatial distribution of dust material in the systems

• Possible correlation with the known (RV) giant planets, as done for outer discs.


Reconstructed images: Case studies:[2] Debris disks



Remark: High dynamic range requirements=> only the 6 AT × 1 night configuration was explored

MATISSE / VSI

+

Similar science cases, but

Complementary in questions to be addresseddue to

Complementary in angular / spatial scale and wavelength

Both:Complementary in wavelength to ALMA, but similar angular scale

Similar to TMT/E-ELT wavelength range, but different angular scale

Documents

VSI / MATISSE - astrophysik.uni-kiel.destar/Kiel2010/Circumstellar_Disk... · 26-28 May, 2010 - University of Kiel. Perfect combination of observing wavelength (~10µm) ... UTs. Required