VSI / MATISSE. Sebastian Wolf University of Kiel, Germany

Transcription

1 VSI / MATISSE Sebastian Wolf University of Kiel, Germany Circumstellar Disks and Planets Science cases for the second generation VLTI instrumentation May, University of Kiel

2 MIDI MATISSE [The Progenitor: MIDI] but Perfect combination of observing wavelength (~10µm) and spatial resolution (VLTI baselines 10-20mas) regions with hot dust can be spatially resolved since 2002 observations 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

3 MIDI MATISSE [MIDI s limitations] a) Small number of visibility points b) 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

4 [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 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)

5 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 disk Assumption: 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 HD 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).

6 Very Large Telescope Interferometer Multi-AperTure Mid-Infrared SpectroScopic Experiment 2 nd generation VLTI beam combiner L, M, N bands: ~ µm Improved spectroscopic capabilities: Spectral resolution: 30 / / Simultaneous observations in 2 spectral bands Goal: Thermal reemission images with an angular resolution of 0.003

7 Multi-AperTure Mid-Infrared SpectroScopic Experiment MATISSE High-Resolution Multi-Band Image Reconstruction + Spectroscopy in the Mid-IR 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 DARWIN Wavelength range 6-18µm

8 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

9 MATISSE [in context]

10 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)

11 MATISSE [ATs / UTs] ATs Goal Requirement Consequence Image reconstruction Optimized coverage of the u-v plane Majority of key science programmes must be executable using the relocatable Auxilliary Telescopes (ATs) UTs Required to reach the sensitivity limits demanded by selected science programmes (e.g. AGNs)

12 MATISSE [Performance goals] Ultimate correlated flux sensitivity Accuracy Maximum spatial resolution

13 selected science cases (in the field of star and planet formation)

14 Size scales Solar System Size Scales IRAS Butterfly Star Angular diameter of the orbits of selected Solar System planets as seen from the distance of the nearby starforming region in Taurus (140pc) : Neptune Jupiter Earth What is possible? TODAY AMBER / VLTI ~ a few mas [near-ir] MIDI / VLTI ~ mas [N band: ~8-13µm] SMA ~ 0.3 (goal: 0.1 ) [~submm]

15 Size scales Solar System Size Scales IRAS Butterfly Star Angular diameter of the orbits of selected Solar System planets as seen from the distance of the nearby starforming region in Taurus (140pc) : Neptune Jupiter Earth 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] 4-6 telescopes; image reconstruction

16 Low/Intermediate mass star formation Planet formation MATISSE [Exemplary science case] 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 Aurigae Spiral arm structure: H band (Herbig Ae star; Fukagawa et al. 2004; SUBARU) Distance: ~140 pc

17 Low/Intermediate mass star formation Planet formation MATISSE [Exemplary science case] 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 Aurigae Asymmetry (Color: 24.5µm, Contours: H Band) (Herbig Ae star; Fujiwara et al., 2006, SUBARU) Distance: ~140 pc

18 Low/Intermediate mass star formation Planet formation MATISSE [Exemplary science case] 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 Aurigae Spiral (345 GHz, continuum) (Herbig Ae star; Lin et al., 2006, SMA) Distance: ~140 pc

19 evolution of the planet-forming region

20 Example #1 HH30 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) [Guilloteau et al. 2008]

21 Example #2 Disk in the Bok Globule CB26 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 [Sauter et al., 2009] Inner disk radius: ~ 45 AU

22 Example #3 The Butterfly Star in Taurus 1360µm 894µm [Wolf et al. 2008] constraints on radial + vertical disk structure in the potential planet-forming region (r~80-120au)

23 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

24 Example #4 Face-on disks r in =37AU r in =27AU r in =40AU 340 GHz dust continuum images of LkHα 330 (top), SR 21N (middle), and HD B (bottom). The crosses mark the literature coordinates of the central star. [Brown et al. 2009]

25 MATISSE Disk clearing 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 ] 10µm image of a circumstellar disk with an inner hole; radius 4AU (inclination: 60 ; distance 140pc; inner 60AU x 60AU)

26 Planetary signatures in the near-ir? Observation Variability 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) Artist impression of the disk around LRLL 31. A planet in the innermost region influences the disk to cast a large shadow on the outer region. The orbit of the planet, and thus the shadow, causes the disk to be variable in the near infrared on timescales on the order of one week. Picture credits: NASA. Example Transitional disk LRLL 31 in the 2-3Myr old starforming 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

27 tracing planets in young disks

28 Disk-Planet Interaction 1M J 1M sun star 0.01 M J 0.03 M J 0.1M J 0.3 M J 1 M J 0.01M J (Bate et al. 2003)

29 ALMA: Gaps Jupiter in a 0.05 M sun disk around a solar-mass star as seen with ALMA d=140pc Baseline: 10km λ=700µm, t int =4h [ Wolf et al ]

30 Planetary Accretion Region [ D Angelo et al ] [ Wolf & D Angelo 2005 ] Procedure Density Structure Stellar heating Planetary heating Prediction of Observation

31 Close-up view: Planetary Region [ Wolf & D Angelo 2005 ] M planet / M star = 1M Jup / 0.5 M sun 50 pc Orbital radius: 5 AU Disk mass as in the circumstellar disk around the Butterfly Star in Taurus Maximum baseline: 10km, 900GHz, t int =8h 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); 30 o phase noise; Bandwidth: 8 GHz

32 Influence on SED? Planet Planetary Environment Inner Disk Planetary Contribution / Disk reemission (within the inner 12 AU ~ 0.1 in Taurus) < 0.4% (depending on the particular model) 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. The presence of a planet + its basic characteristics (temperature, luminosity) cannot be derived from the SED of the disk alone. [ Wolf & D Angelo 2005 ]

33 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 ]

34 High Resolution! Requirement

35 MATISSE Planets Hot Accretion Region around the Planet inclination: 0 [ Wolf et al ]

36 Shocks & MRI Gas Dust 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 Log Density in MHD simulations after 100 planet orbits for planets with relative masses of q=1x10-3 and 5x10-3 (Winters et al. 2003) Observations of gaps will allow to constrain the physical conditions in circumstellar disks

37 Shadow Astrometry K band, scattered light 5 AU Space Interferometry Mission (SIM) Wavelength range µm [ Wolf & Klahr, in prep.] Conditions for the occurrence of a significantly large / strong shadow still have to be investigated Baseline: 10m Narrow Angle Field: 1 Narrow Angle Astrometry 1µas mission accuracy Strategy Center of Light Wobble [ G. Bryden, priv. comm.]

38 Giant Planets in Debris Disks 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. Scattered Light Image [ Rodmann & Wolf ] 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 Decreased Mid-Infrared SED

39 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: % (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 interferometry MATISSE: 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.

40 Massive Star Formation High-mass star forming regions are much more distant (in average) than those of low-mass stars (high-mass: 3-7kpc vs. low-mass: kpc) OB stars - form preferentially in the centre of dense star clusters - seem to live pref. in (tight) binary and higher order systems High number density of objects Enhanced outflow activity Strong stellar winds from the massive stars after ignition JHK composite of NGC 3603 from ISAAC data, dimension 25'' x 25'' The Orion BN/KL region at 12.5µm, dimension 10'' x 10'' (distance 450 pc) [Shuping et al. 2004]

41 Multi-wavelength imaging 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) 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 L M N

42 Spectroscopy [Dust]

43 Spectroscopy [Gas] Prominent gas/dust features L band H 2 O ice broad band feature ( µm) PAHs: 3.3µm, 3.4µm Nanodiamonds: 3.52µm Highest Sensitivity in the MIR (reduced background emission) M band CO fundamental transition series ( µm) CO ice features ( µm) Recombination lines, (e.g., Pfβ at 4.65µm)

44 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, H 2 O 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. 8µm: 30mas [Wit et al. 2007]

45 Summary MATISSE in the context of Star and Planet formation Star and Planet Formation Low-mass Star and Planet Formation Mineralogy of proto-planetary disks, dust grain growth and sedimentation Transitional objects: Status of inner disk clearing Nature of outbursting young stellar objects Binary 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 disks Planetesimal collisions and exo-comets evaporation, grain properties and disk geometry. Complex spatial inner disk structure direct indicators for the presence of planets Characterization 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)stars Spatial 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

46 Phase-referenced imaging Phase-referenced imaging allows one to reconstruct 4 fainter targets than closure-phase imaging Phase-referenced imaging can yield acceptable reconstructions of the T Tauri disk ( 90 mas diameter) 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%) larger targets than closure phase imaging. Reconstruction of T Tauri disks (average SNR 20 of the squared visibility) up to diameters of mas (restoration errors 28-42%), and closure-phase imaging can reconstruct disks up to a diameter of 120 mas (restoration errors 16%).

47 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

48 VSI: VLTI Spectro-Imager Instrument design: Imaging Young star disks and winds; Evolved stars; Stellar surfaces; AGN torus. High dynamic range imaging Debris disks. Parametric visibilities Binaries, AGN BLRs and massive black holes. High dynamic range parametric visibilities Extrasolar planets. PRIMA operation Additional science in AGN torus, BLR and massive-black holes Target of opportunity + PRIMA Microlensing (additional science)

49 VSI: VLTI Spectro-Imager Scientific requirements Spectroscopic requirements. lowest resolution: intermediate spectral resolution: high spectral resolution: 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 less than 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 up to 2.40 μm.. spectral bands (J, H or K) does not necessarily have to be observed simultaneously.

50 VSI: VLTI Spectro-Imager Scientific requirements Fringe 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 K band. A mode where part (exact amount TBD) of the K band light is used to fringe track and 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 on one of PRIMA s dual beams, the other being reserved for the science channel.

51 VSI: VLTI Spectro-Imager Scientific requirements Imaging requirements. Telescope positions should remain fixed during the night.. An imaging mode where three different combinations of four telescopes (3 x 4T) are available within a time-span of weeks, is required.. An imaging mode where the simultaneous combination of six telescopes (6T) is available in a single night, would open new and unique science. PRIMA The star separator systems and differential delay lines of PRIMA allows off-axis fringe tracking

52 VSI: VLTI Spectro-Imager Selected science cases Young 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 lines MATISSE: Obtaining images of protoplanetary disks at multiple infrared wavelengths will enable a global picture of these objects

53 VSI: VLTI Spectro-Imager Reconstructed images: Case studies: [1] YSOs 3x4T [MIRA reconstruction] 1x6T [MIRA reconstruction]

54 VSI: VLTI Spectro-Imager Reconstructed images: Case studies: [1] YSOs 3x4T [BSMEM reconstruction] 1x6T [BSMEM reconstruction]

55 VSI: VLTI Spectro-Imager Selected science cases Multiplicity of young stars Is the frequency of companions within 5AU of YSOs consistent with that observed among nearby field stars or substantially higher, as for wider systems? Among multiple systems, what is the frequency of quadruple and high-order systems and do they show evidence of past dynamical re-arragements? Are there some significant trends regarding this restricted multiplicity rate as a function of stellar mass, age and/or environment? Can the physics of core fragmentation and/or subsequent internal rearrangements account for these differences? Alternatively, do these companions form through a distinct mechanism?

56 VSI: VLTI Spectro-Imager Selected science cases Exoplanets 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

57 VSI: VLTI Spectro-Imager Reconstructed images: Case studies: [3] Microlensing 1x6T(?) [MIRA reconstruction] 1x6T(?) [BSMEM reconstruction]

58 VSI: VLTI Spectro-Imager Selected science cases Debris 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.

59 VSI: VLTI Spectro-Imager Reconstructed images: Case studies: [2] Debris disks 1x6T [MIRA reconstruction] 1x6T [BSMEM reconstruction] Remark: High dynamic range requirements => only the 6 AT 1 night configuration was explored

60 MATISSE / VSI + Similar science cases, but Complementary in questions to be addressed due 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