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Interferometry in the visible Young Stellar Objects M. Benisty, S. Kraus, K. Perraut (leader), G. Schaefer, M. Simon Science cases for visible interferometry – Nice, January, 15th 1 Scientific rationale Nuage moléculaire Molecular clouds (Taurus) Effondrement Collapse 1 pc ― 20’ 10 pc ― 4° Accretion disk and bipolar ejection Debris disk and protoplanets 106 yrs 0.1 pc ― 2’ Planetary system old [Bouvier & Malbet 2001] 105 / Fragmentation Fragmentation 1000 AU ― 7’’ 300 AU ― 2’’ 30 AU ― 0.2’’ Outline Fundamental parameters of YSO Complex environment Summary of High-Level Requirements 3 Outline Fundamental parameters of YSO Complex environment Summary of High-Level Requirements 4 Fundamental parameters of YSO For low-mass (M < 1 Mʘ) young (< 10 Myr) PMS stars the mass and age estimates vary according to the evolutionary tracks used. The mass spectrum of low mass stars (the majority!) is imprecisely known. The chronology of planet formation is also imprecisely known. 5 Situation and opportunities M < 1 Mʘ : Dynamical measurements of masses will “calibrate” the theoretical calculations of evolution. Masses < 0.5 Mʘ are particularly required. Studies of Taurus and Ophiuchus star forming regions (1 to few Myr; 120-160 pc) M > 1 Mʘ : Theoretical calculations are consistent. Hence diameter measurements of a star determine its age! Studies of stars in the older (10 Myr +), but closer (few pc +) “Nearby Young Moving Groups” 6 Interferometric measurement Angular Resolution (mas) at Baseline (m) = 0.6 µm = 1.0 µm = 1.5 µm 100 0.62 1.03 1.5 200 0.31 0.51 0.77 300 0.21 0.34 0.5 1 AU orbit at 140 pc (eg Tau and Oph) subtends 7 mas. at 10 pc: 1.0 mas (Sun); 0.5 mas (M0V) Angular diameters in Tau or Oph unresolvable Interferometric measurement of dynamical masses in these regions possible for visual binaries and some SB Diameters of F and G stars in Nearby Young Moving Groups resolvable if close enough 7 Census of dynamical masses MIRC observations of s Ori Aa-Ab [Schaefer et al., in prep] N=8 N=4 N=8 Resolved Spectroscopic Binaries Eclipsing Binaries Masses with precisions measured to better than 10% MAa = 16.8 ± 0.4 M⊙ MAb = 12.8 ± 0.3 M⊙ d = 385 ± 3 pc Few precise masses below 0.5 Mʘ 8 Resolving PMS Spectro binaries Taurus-Auriga Ophiuchus Sco-Cen Chamaeleon Orion NGC 2264 a sin i (mas) Resolved SB2 Spectral Types: F-M PMS binaries resolved with a baseline of 300 m Eclipsing SB2 R-band K-band 39 21 V (mag) Going down to R-band doubles the sample 3D structure of Taurus SFR Stars with measured proper motions [Ducourant et al. 2005] CO clouds [Dame et al. 2011] Stars with measured distances [Torres et al. 2009; Simon et al. 2013] The clumps where stars formed range from 131 to 161 pc. Need distances to L1495N, L1551 (hosting GG Tau) Nearby Young Moving Groups NYMGs are stars known to exist in the vicinity of the Sun as members of “moving groups” each consisting of stars moving in the same approximate direction with the solar neighborhood. They are young: 8-12 Myr ( Pic moving group) ~ 40 Myr (AB Dor moving group) They are nearby: from a few to 100 pc. Most members of the NYMGs are Known members of Pic NYMG [Schlieder et al. 2012]. Spectral in Southern hemisphere but some type is coded by color. members of Pic and AB Dor are in the North. 11 Measure diameter of stars in NYMGs Pic MG HIP 21547 (0.518 ± 0.009 mas) HIP 25486 (in progress) HIP 560 (0.492 ± 0.013 mas) [Simon & Schaefer 2011] AB Dor MG [Schlieder 2012, PhD Thesis] NOTE: angular diameter (mas) scaled to a common distance of 10 pc Measure diameter of NYMG members V mag Star number Spectral Type 3-4 1 A 4-5 1 A 5-6 3 2A, 1F 6-7 5 5F 7-8 6 4F, 1G, 1K 8-9 3 9-10 4 10-11 13 11-12 11 12-13 6 13-14 2 14-15 1 Mostly G and K Mostly M Known members of Pic NYMG in 2008 [Torres et al. 2008]. All the F stars can be resolved at 1 μm with baselines ≥ 100 m F stars are in the “sweet spot” for angular diameter and hence age measurement: they are bright, near to us, their evolutionary tracks are reliable, and they are still above ZAMS. Outline Fundamental parameters of YSO Complex environment Summary of High-Level Requirements 14 Structure of a protoplanetary disk [Dullemond & Monnier 2010] 15 The complex innermost regions Near-infrared (spectro-)interferometry directly probes the emission within the innermost astronomical unit (AU), where key quantities for the star-disk-protoplanet(s) interactions are set. The regions probed by this technique are much more complex than expected. 3D MHD simulations of accretion (driven by magneto-rotational instability) on to a rotating magnetized star with a tilted dipole magnetic field produce complex maps. All these complicated inner disk structures are strongly time variable on a timescale of weeks to years … [Romanova et al. 2012] Accretion-ejection phenomena Accretion via the accretion columns (T Tau) or the inner disk Connections star/inner disk, inner disk/dust disk ? Morphology of the inner rim of the dust disk ? Processus of dissipation and evolution of the disk ? Law of temperature, velocity, density in the disk ? Ejection via a wind (star, disk, …) and jets Launching point and morphology of jets ? Mechanisms that favor jet collimation ? Mass-loss rate wrt mass-accretion rate ? Formation of the Hydrogen emission lines Connection between accretion and ejection Line forming regions ? Mechanisms that could explain the temporal variability ? 17 Visible spectral lines DG Tau vs. FU Ori spectra Forbidden lines (e.g. [OI], [NII], [FeII], [SII]) Ha (and also Ca II triplet at 850/854/866 nm) Trace low-density gas,1 sometimes withpc R* = 0.07associated mas @ 140 andlikely outflow. However, this emission is typically Accretion tracer [Hartmann et al.jets 1994], Requires very high distributed over tracing structures on the stellar surface and in themany arcseconds [Podio et al. 2011; Bacciotti magnetospheric accretion columns (3-5 R*et ) al. 2002] angular resolution possibly overresolved with interferometry Visible spectral lines Lines (nm) EW (Å) Ha 656.2 20 - 150 Ca II triplet 849.8 854.2 866.2 0.5 - 50 He I lines 667.8 706.5 0.5 – 2 O I lines 777.2 844.6 -1.6 - 8 [0I] line 630 < 15 [SII] line 673.1 <5 [FeII] line 715.5 <2 Requires very high spectral resolution 19 The He I1.083 line [Edwards et al. 2003] • A unique diagnostic of kinematic motion in the regions close to the star. • High opacity: a very sensitive probe to the geometry of the mechanisms at play. • He I line is composite: • Blue-shifted absorption (wind) • Red absorption (accretion) [Kurosawa et al. 2011] Very compact wind (few R*) that requires very high angular resolution 20 Accretion in close binaries • Stars orbit in a gap opened by tidal interactions inside a circumbinary disk. • Young short period binaries (P < a few 10 days, sep ~ a few 0.1 AU) cannot support large circumstellar disks. Circumbinary disk • Evidence of enhanced emission line activity close to periastron passages (DQ Tau [Basri et al.1997], UZ Tau E [Martyn et al. 2005]) non-axisymmetric accretion [de Val-Borro et al. 2011] 21 Simulated accretion streamers V4046 Sgr [de Val-Borro et al. 2011] 0.2 mas R mag = 9.5 Interferometry will provide a critical test of simulations such as these. 22 Detecting low-mass companions [Close et al. 2014] Planets and brown dwarfs forming in the disk should exhibit accretion signatures (H-a emission) Expected contrast (companion/star) w/o extinction Brown Dwarf < 10-3 Jup. < 10-4 Contrast could be dramatically reduced due to extinction Requires high contrast imaging at moderate spectral resolution Scattered light disk features HD141569, HST Imaging in scattered light could reveal asymmetric structures that might be linked to planet formation, similar as seen in the outer disk [Mouillet et al. 2001] HD10054 6 Combining scattered light imaging Total integrated scattered light in contributions are about 100VIS/NIR constraints sizeflux times fainter thandust stellar distribution and vertical dust stratification (Mulders etal.Requires 2013) high-fidelity, high-contrast imaging Interest of polarimetric mode (SPHERE) or nulling Outline Fundamental parameters of YSO Complex environment Summary of High-Level Requirements 25 Summary of High-Level Specs Science cases Diameter of stars in SFR Baseline Spectral resolution Imaging A few 1000 (Ha) 1 few 10000 Yes Unreachable Diameter of stars in NYMGs > 100 m Dynamical masses 300 m Accretion-ejection Hectometric Companion Hectometric High-contrast Scattered light Hectometric High-contrast High-fidelity 26 Limiting magnitudes Pre-Main sequence stars in Taurus-Auriga K 70 Object numbers 60 From Kenyon et al. 2008 50 R 40 30 20 10 0 4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 13.5 14.5 15.5 16.5 17.5 18.5 19.5 20.5 Magnitude In Ophiuchus, K-mags are similar but R are fainter because of greater extinction. 27 Conclusions YSO is a strong science case for interferometry in the visible. Interferometric Imaging and Spectroscopy will provide unique and complementary data for understanding star and planet formation. The techniques will probe the innermost regions protoplanetary disks and will enable diameter measurements of stars still contracting to the main sequence. The science case is very challenging mainly because of the brightness of targets. 28 Differences among models 1.0 Mʘ 0.1 Mʘ Increasingly ideal gas in interior Increasingly non-ideal Radiative transport increasingly important in core Radiative transport less important Convection increasingly important Peak of spectral energy distribution increasingly affected by broad molecular absorption Therefore: 1) Equation of state 2) Radiative and molecular opacities are very important. 3) Treatment of convection 4) Model atmospheres