THEORY OF DEBRIS DISKS MODELING Jean-Charles Augereau, IPAG – Grenoble, France 2 What is a debris disk? Star Fomalhaut : composite HST+ALMA image Kalas et al. 2005, Boley et al. 2012 • Extrasolar planetary systems have planets, but also comets and asteroids ! • Extrasolar comets/asteroids manifest themselves when they release dust : collisions, evaporation ! • Debris disks • cold (~20-100K), extra-solar analogs to the Kuiper Belt • warm/hot (up to ~1500/2000K), extra-solar analogs to the asteroid belt and zodiacal dust 3 Why modeling debris disks? What do we want to know? • Grain properties: • Spatial distribution: • composition of • interaction with the unseen planets population of • history of the planetesimals formation and • size distribution evolution of planetesimals Toward a complete census of the constituents of extrasolar planetary systems, and a detailed understanding of their overall dynamics. 4 Theory of debris disk modeling Spectral Energy Distributions. Blackbody fitting, and limitations 10.0 1.0 Flux in Jy 0.1 • Hundreds of debris disks detected • Only ~40-50 have been spatially 1 10 100 1000 resolved [µm] 5 • Fractional luminosity: Spectral energy f = LIR / Lstar distribution ! ! 10.0 ! ! 1.0 !Flux in Jy Lstar ! 0.1 LIR ! 1 10 100 1000 ! [µm] • f ~ optical thickness ≪ 1 u the disk is optically thin In this example: f = 3x10-4 6 • Fit of a blackbody to the disk emission Spectral energy u disk mean temperature Tdust distribution ! • Spherical blackbody grains in thermal equilibrium: Tdust u disk radius Labsorbed = Lemitted L (⇡a2) ? =(4⇡a2)σT 4 4⇡r2 dust 10.0 L? rbb = 4 1.0 16⇡T Flux in Jy s dust 0.1 1 10 100 1000 [µm] 7 • Blackbody vs observed disk Spectral energy radii distribution Spectral L Star T r robserved Type (Lsun) Fomalhaut A3 16.6 65 K 75 AU HR 4796 A0 21 110 K 30 AU HD 181327 F6 3.3 75 K 25 AU q1 Eri F8 1.6 60 K 27 AU HD 15115 F2 3.1 65 K 32 AU HD 207129 G2 1.3 50 K 35 AU 8 • Blackbody vs observed disk Spectral energy radii distribution Spectral L Star T r robserved Type (Lsun) Fomalhaut A3 16.6 65 K 75 AU ~140 AU HR 4796 A0 21 110 K 30 AU HD 181327 F6 3.3 75 K 25 AU q1 Eri F8 1.6 60 K 27 AU HD 15115 F2 3.1 65 K 32 AU HD 207129 G2 1.3 50 K 35 AU 9 • Blackbody vs observed disk Spectral energy radii distribution Spectral L Star T r robserved Type (Lsun) Fomalhaut A3 16.6 65 K 75 AU ~140 AU HR 4796 A0 21 110 K 30 AU ~70 AU HD 181327 F6 3.3 75 K 25 AU q1 Eri F8 1.6 60 K 27 AU HD 15115 F2 3.1 65 K 32 AU HD 207129 G2 1.3 50 K 35 AU VLT/SPHERE press release image Beuzit et al. 2014 10 • Blackbody vs observed disk Spectral energy radii distribution Spectral L Star T r robserved Type (Lsun) Fomalhaut A3 16.6 65 K 75 AU ~140 AU HR 4796 A0 21 110 K 30 AU ~70 AU HD 181327 F6 3.3 75 K 25 AU ~90 AU q1 Eri F8 1.6 60 K 27 AU HD 15115 F2 3.1 65 K 32 AU HST/STIS, Schneider et al. 2014 HD 207129 G2 1.3 50 K 35 AU Figure 5. Comparison of PSF-subtraction methods revealing the HD 181327 debris ring in HST coronagraphic images with (A–D) derived from the same raw data (NICMOS 1.1 µm imagery) and (E) STIS 6 roll (6R) contemporaneous observationally matched-PSF template subtracted coronagraphy (PSFTSC). A: NICMOS discovery image using two (of ten) non-contemporaneously observed PSF template stars (Schneider et al, 2006; HST GO program 10177). B: “LAPLACE” (HST AR program 11279) re-processing and globally optimized re-reduction with PSF-matching from a down-selected 53 template ensemble (Schneider et al., 2010). C: LOCI re-processing (without regularization) with a 232 LAPLACE recalibrated PSF template library. D: KLIP re-processing (35 coefficients) using same PSF template library as (C) with regularization. C and D from Soummer, Pueyo, and Larkin 2012 (HST AR program 12652). E: STIS 6R-PSFTSC (result from this program discussed in this paper). Gray circle indicates the location and size of the NICMOS r = 0.3" coronagraphic circular obscuration. 6.2. Comparison with HST/ACS Observations While the large angular extent of the ACS coronagraphic masks (r = 0.9" and r = 1.8") preclude CS observations at small IWA’s the instrument (unlike NICMOS) does provide a coronagraphic FOV comparable to STIS. This has been used advantageously for (angularly) large CS debris systems, but is significantly less efficient than STIS. For example, the full extent of the HD 181327 debris system (unseen with NICMOS) is revealed with STIS six-roll PSFTCS and compared in Fig. 6, over the full dynamic range of imaging sensitivity, to a discovery epoch PSF-subtracted ACS image at very similar central wavelength (from Schneider et al 2006). Nebulosity in the STIS image is traced to stellocentric distances of 9.5" with more complete sampling about the star, better image fidelity, and higher sensitivity to low surface-brightness light-scattering material in the outermost, photon-limited, portions of the HD 181327 debris system. The STIS instrument’s near full-throughput pupil (compared to ~ 50% for ACS in its coronagraphic mode), and unfiltered spectral sensitivity (∆λ/λ = 75%, compared to 25% for ACS/F606W) together provide an ≈ 6x gain in exposure depth per unit integration time. For these STIS observations, with the additional investment in exposure time of a factor ≈ 4.5x over the ACS images, an improvement in exposure depth by a factor of ≈ x27 and photon-limited S/N 11 • Blackbody vs observed disk Spectral energy radii distribution Spectral L Star T r robserved −1.6 Type (Lsun) −1.7 log −1.8 10 (Flux) in Jy / arcsec Fomalhaut A3 16.6 65 K 75 AU ~140 AU −1.9 −2.0 HR 4796 A0 21 110 K 30 AU ~70 AU −2.1 HD 181327 F6 3.3 75 K 25 AU ~90 AU −2.2 −2.3 2 q1 Eri F8 1.6 60 K 27 AU ~75 AU −2.4 −2.5 HD 15115 F2 3.1 65 K 32 AU Herschel/PACS deconvoled image, HD 207129 G2 1.3 50 K 35 AU DUNES consortium Gemini/NICI, Mazoyeral.subm. et distribution Spectral energy Mazoyer et al.: Is the HD15115 inner disk really asymmetrical? -2.10-7 -1.10-7 0 1.10-7 2.10-7 Figure 2. Final KLIP image of the disk around HD 15115 in H band on the November 7, 2011. We pointed out the zones of interest. The color scale indicates the contrast with respect to the maximum intensity in the PSF image. • Blackbodyobserved vs disk But more importantly, these NICI data, of better quality than the previous ones, are radii the first to suggest a ring-like inner disk (labelled (3) in Fig. 2), which directly implies a strong dust depletion within a radius of about 2”. On the Nov. 7th, 2011 data (Fig. 2), the edges of this ring are visible in the two sides, while the Nov. 22th, 2011 data (Fig. 1, bottom, left) shows this feature in the east side only. Finally, on the west part of the disk, the bottom part of the ring below the midplane is also barely suspected in Fig. 2. A simple ellipse fitting of the suspected ring, directly in a KLIP image from Nov 7th, 2011, yields a first rough estimation of the disk parameter. We found PA 98.5◦, i 86.2◦, ⇡ ⇡ radius 2.0”. Noticeably, the ring appears almost symmetrical in size, which contrasts with ⇡ the brightness asymmetry. In addition, we didn’t measure any significant o↵set along the major axis neither along the minor axis, with respect to the star position. 3.2. Signal to noise ratio 0 2 4 6 8 10 12 0 2 4 6 8 10 12 Spectral L Star T r robserved Type (Lsun) N N 1" 1" E FomalhautE A3 16.6 65 K 75 AU ~140 AU Figure 3. Signal to noise ratio maps, calculated for the H (left)HR and Ks4796 (right) bands in A0 21 110 K 30 AU ~70 AU the Nov. 7th, 2011 data. Color scales indicate the S/N per resolution element. HD 181327 F6 3.3 75 K 25 AU ~90 AU We calculated the signal to noise ratio (S/N) in the H (Fig. 3, left) and Ks (Fig. 3, right) bands in the Nov. 7th, 2011 data. The noise is estimated in theq1 upper Eri part of the image F8 1.6 60 K 27 AU ~75 AU (PA=30 to 180◦) and per resolution element. The disk is detected as close as a separation of 1” in both sides. In the Ks band the disk has a lower S/N thanHD in the 15115 H band as we can F2 3.1 65 K 32 AU ~90 AU expect from its blue color (Debes et al. 2008). Finally, the S/N map confirms the brightness 12 asymmetry, and the rather symmetrical ring-like pattern of theHD inner disk.207129 G2 1.3 50 K 35 AU 6 13 T. Löhne et al.: Modelling the huge, Herschel-resolved debris ring around HD 207129 • Blackbody vs observed disk Spectral energy radii distribution Spectral L Star T r robserved Type (Lsun) Fomalhaut A3 16.6 65 K 75 AU ~140 AU HR 4796 A0 21 110 K 30 AU ~70 AU HD 181327 F6 3.3 75 K 25 AU ~90 AU q1 Eri F8 1.6 60 K 27 AU ~75 AU HD 15115 F2 3.1 65 K 32 AU ~90 AU Herchel/PACS, Löhne et al.