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HD 100453 An Evolutionary Link Between Protoplanetary Disks and Debris Disks Karen Collins Master’s Thesis Defense April 24th, 2008 University of Louisville Department of Physics and Astronomy Supported by a Fellowship from the Kentucky Space Grant Consortium Thesis Directors Dr. Gerard Williger - UofL Dr. Carol Grady - NASA GSFC Journal Paper Co-authors Co-authors(s) Affiliation Contribution C. A. Grady Eureka Scientific and NASA GSFC overall direction, science mentor, HST and Chandra PI, and day-to-day support K. Hamaguchi & R. Petre X-ray Astrophysics Laboratory NASA/GSFC Chandra observations, data reduction, and results J. P. Wisniewski NASA/GSFC, NPP Fellow HST ACS HRC observations, data reduction, and results S. Brittain Clemson University Gemini South observations of warm CO, data reduction, and results M. Sitko & W. J. Carpenter SSI, University of Cincinnati SED and modeling data, general support G. M. Williger University of Louisville FUSE observations, data reduction, results, and general day-to-day support R. van Boekel Max-Planck-Institut für Astronomie VLT NACO NIR observations, data reduction, common proper motion results, and related photometric results A. Carmona Max-Planck-Institut für Astronomie, ESO, ISDC & Geneva Observatory VLT SINFONI NIR spectroscopy, data reduction, spectral typing, and other related results. M. E. van den Ancker European Southern Observatory VLT SINFONI NIR spectroscopy, data reduction, spectral typing, and other related results. G. Meeus Astrophysikalisches Institut Potsdam FEROS Ca II spectroscopic data J. P. Williams, G. S. Mathews University of Hawaii JCMT HARP CO spectroscopic observations, data reduction, dust mass calculations, gas mass calculations, and related results X. P. Chen Max-Planck-Institut für Astronomie VLT NACO Brγ common proper motion data reduction B. E. Woodgate NASA/GSFC overall scientific interpretation Karen Collins Master's Thesis Defense 4/24/2008 Star Formation Overview Start with molecular cloud Four phases of collapse dense rotating core forms collapses from inside out bipolar outflows carry away angular momen. (L) star and disk revealed Shu et al. 1987 Conservation of L cloud rotates slowly star rotates more rapidly High L material forms disk disk accretes onto star Wood 1997 Karen Collins Master's Thesis Defense 4/24/2008 Pre-Main Sequence Stars Pre-main sequence (PMS) stars fully revealed stars still gravitationally contracting toward main sequence hydrogen fusion not started yet PMS stars are called T Tauri if 0.1 M < M < 2 M (M, K, G, F type stars) Herbig Ae/Be if 2 M < M < 8 M (F, A, B type stars) higher mass stars emerge from cloud on main sequence Observable characteristics Balmer emission lines in stellar spectrum (Hα, Hβ, Hγ, …) transition (32, 42, 52, …) infrared excess due to circumstellar dust (next slides) Karen Collins Master's Thesis Defense 4/24/2008 Spectral Energy Distribution Spectral Energy Distribution (SED) plot of radiated energy vs. wavelength Stellar photosphere ~blackbody peaks in optical Sun 5778 K A-type stars 7500-10,000 K M-type stars 3000-4000 K Karen Collins Master's Thesis Defense 4/24/2008 Infrared Excess IR excess total emission − stellar contribution stellar contribution determined from a model fit to UV and Optical data source is circumstellar dust dust absorbs stellar radiation re-radiates as thermal emission IR excess source inner disk NIR (1 - 7 μm) outer disk MID to FIR (10 - 50 μm) disk midplane FIR to mm (>50 μm) Karen Collins adapted from M.Sitko simulation Master's Thesis Defense 4/24/2008 Disk Evolution Protoplanetary Disks (initial phase) gas rich + small dust grains (submicron) gas:dust ~100:1 (as in interstellar medium (ISM)) high accretion rates (> ~1108 M yr1) gas and dust well mixed hydrostatic equilibrium dust material supported above midplane disk can maintain scale height disk expected to “flare” Karen Collins Master's Thesis Defense 4/24/2008 Flared Disk "bowl" shaped disk h r, where > 1.0 relatively flat SED in IR inner rim NIR BB disk surface MIR - FIR disk midplane FIR - mm Dullemond et al. 2006 Dullemond et al. 2006 Karen Collins Master's Thesis Defense 4/24/2008 Disk Vertical Structure inner-most part of the disk is dust free beyond sublimation temperature the inner rim is illuminated face-on from the star, the gas heats up more and causes an increased scale height (i.e. it "puffs up") as the disk ages, the dust grains grow in size disk becomes vertically stratified larger grains in midplane smaller grains in upper layers Dullemond et al. 2006 Karen Collins Master's Thesis Defense 4/24/2008 Disk Evolution Continued accretion rates ~10 - 100x lower than protoplanetary disks IR excess similar to pp disk at >10 μm Van den Ancker 1999 Transitional Disks (intermediate phase) Protoplanetary Disk IR excess significantly less at <10 μm result of less dust, or optically thin dust, in the inner disk Transitional Disk photoevaporation grain growth until optically thin gap creation by massive planet Karen Collins Master's Thesis Defense 4/24/2008 Disk Evolution Continued Protoplanetary Disk Debris Disks (final phase) accretion has stopped moderate IR excess at >10 μm very little to no IR excess at <10 μm Transitional Disk no inner disk at all primordial dust has grown to rocks, protoplanets, and terrestrial planets remaining dust is second generation gas-poor Karen Collins Master's Thesis Defense Van den Ancker 1999 from collisions of massive bodies Debris Disk 4/24/2008 Meeus Groups Meeus et al. (2001) divided 14 Herbig stars into two groups Group I blackbody in MIR high fraction of IR excess (LIR/L* ~ 0.5) steep submm slope (i.e. small grains) Group II no blackbody in MIR low fraction of IR excess (LIR/L* ~ 0.2) shallow submm slope (i.e. larger grains) Meeus et al. suggested Group I sources evolve to Group II sources Meeus et al. 2001 Karen Collins Master's Thesis Defense 4/24/2008 Meeus Physical Model 3 components disk midplane - optically thick inner disk with scale height outer disk Group I inner disk optically thin outer disk is directly illuminated outer disk heats & flares creates MIR BB Group II inner disk optically thick outer disk shielded outer disk stays flat no MIR BB Karen Collins Master's Thesis Defense 4/24/2008 Thesis Goal Test idea that Meeus Group I sources evolve to Meeus Group II sources at time of Meeus et al. (2001) paper, many age estimates were not available accretion rates were not considered (recall that accretion rate is tied to disk evolution) Karen Collins Master's Thesis Defense 4/24/2008 Thesis Approach Compare ages and accretion rates between the groups we focus on HD 100453 in this work because: Herbig AeBe stars are difficult to date after about 5 Myr low-mass stars are easier to date and often form together with A-stars we can determine the age of the A-star from a companion low-mass star a candidate low-mass companion was recently reported for HD 100453A (Chen et al. 2006) determine age and accretion rate for HD 100453A (this work) determine age and accretion rate for other stars from the literature Karen Collins Master's Thesis Defense 4/24/2008 HD 100453A Southern Hemisphere (Lower Centaurus-Crux Assn) Distance 114 pc v=7.78 (not visible by naked eye) Spectral Type A9Ve Age > ~10 Myr Karen Collins Master's Thesis Defense 4/24/2008 Summary of Observations Instrument Chandra K. Hamaguchi Direct Image HST ACS HRC J. Wisniewski HST ACS HRC J. Wisniewski HST ACS SBC VLT NACO C. Grady K. Collins R van Boekel VLT SINFONI A. Carmona NIR Spectral Type of Companion FUSE G.M. Williger FUV Accretion Rate Phoenix S. Brittain NIR Warm Gas Limits JCMT HARP J. Williams G. Mathews G. Meeus K. Collins Submm Cold Gas Limits Optical Accretion Rate FEROS Karen Collins Prime Coron. Image Spectra Wavelength Scientific Purpose X-ray Accretion Rate Optical Companion Location & Photometry Optical Disk Detection & Photometry FUV Companion Detection NIR Companion Proper Motion & Photometry Master's Thesis Defense 4/24/2008 Test of Companion Status To date an A-star from a low-mass companion, we need to know that they are physical companions Two tests: determine motion of A-star & candidate companion If motion through space is common, they are likely physical companions determine spectral type of companion for the brightness contrast between the two stars, a physical companion would be a low-mass star Karen Collins Master's Thesis Defense 4/24/2008 The Candidate Companion HST optical direct image B located 1.05 @ 126° east of north mv = 15.87 (A:B = 1500:1 contrast) optical HST ACS HRC F606W Karen Collins Master's Thesis Defense 4/24/2008 Candidate Companion Spectral Type Need high spatial resolution spectroscopy to separate the light from the two stars Optical Spectroscopy is first choice need A/O for ~1 separation none available NIR is good second choice SINFONI on VLT with A/O Integral Field Spectrograph 0.8 x 0.8 field of view J, H, K band gratings (NIR) Karen Collins Master's Thesis Defense 4/24/2008 Candidate Companion Spectral Type Compare to 4 standard stars M3.5V M4.0V M4.5V M5.0V Find closest match to features in all 3 bands Spectral Type is M4.0V - M4.5V Karen Collins Master's Thesis Defense 4/24/2008 Relative Proper Motion Determine movement of A star over 3 years Hipparcos data 0.111 ± 0.003 Determine relative motion of candidate companion over 3 years use VLT NACO Brγ imagery 2003 data (Chen et al. 2006) 2006 data (this work) compare change in position of B w.r.t. A 0.020 ± 0.010 Common proper motion confirmed Residual could be orbital motion Karen Collins Master's Thesis Defense 4/24/2008 Candidate Confirmation Common proper motion suggests both stars originated from same cloud suggests physically companions Spectral Type M4.0V - M4.5V class “V” not a distant red giant (high luminosity) A9:M4 has proper contrast ratio Confirmation that candidate companion is a physical companion Karen Collins Master's Thesis Defense 4/24/2008 Companion Photometry Object Mode Filter magnitude HD 100453B Direct mF606W 15.6 HD 100453B Coron mF606W 15.8 HD 100453B Combined mF606W 15.7 0.2 Notes (prime) HST HRC (J. Wisniewski) HST HRC (J. Wisniewski) (J. Wisniewski) HD 100453B Direct Ks 10.66 0.1 HD 100453B Coron L 10.13 0.1 HD 100453B Coron M 9.99 0.1 HD 100453B Calculated V 15.87 0.2 (Chen et al. 2006) VLT NACO (R. van Boekel) VLT NACO (R. van Boekel) (K. Collins) HD 100453B Calculated K 10.64 0.1 (K. Collins) HD 100453B Calculated L 10.27 0.1 (K. Collins) • Key Point: Candidate companion has NO IR Excess Can use K-band in H-R diagram for age estimate Karen Collins Master's Thesis Defense 4/24/2008 Age Determination (from A-star) PMS H-R diagram - derived from Siess et al. stellar models if we know magnitude and effective temperature we can determine age and mass HD 100453A mv = 7.7 A9Ve Teff = 7400 K Results age: 10 Myr - ZAMS mass: 1.6 - 1.8 M Age is not well constrained because of compressed isochrones at >10 Myr Karen Collins Master's Thesis Defense 4/24/2008 Age Determination (from Companion) Note wider separation of isochrones for low-mass stars HD 100453B (input data) mK = 10.64 ± 0.1 M4.0V – M4.5V Teff = 3300 K – 3400 K Results (Siess Model) age: 10 15 Myr mass: 0.21 0.23 M Results (Baraffe Model) age: 11 18 Myr mass: 0.24 0.30 M Results (Combined) age: 14 ± 4 Myr mass: 0.21 0.30 M Karen Collins Master's Thesis Defense 4/24/2008 Mass Accretion onto A-star Mass accretion rate gives insight into the evolutionary phase of the disk We investigate the following accretion indicators: enhanced FUV continuum Herbig-Haro knots in Lyα enhanced emission of Ca II λ8662 Å Hard X-rays Hα (6563 Å) Brγ (2.166 μm) Karen Collins Master's Thesis Defense 4/24/2008 Accretion - FUV Continuum FUV continuum upper limit from FUSE spectra <1.51015 ergs s1 cm2 Å1 (1σ) (-14.8 in log space) Karen Collins Master's Thesis Defense 4/24/2008 Accretion - FUV Continuum Plot accretion rate vs. FUV continuum accretion rates based on Brγ (Garcia Lopez et al. 2006) FUV values from literature note power law trend except HD 100453 Karen Collins Master's Thesis Defense 4/24/2008 Accretion - FUV Continuum Plot accretion rate vs. FUV continuum accretion rates based on Brγ (Garcia Lopez et al. 2006) FUV values from literature note power law trend except HD 100453 relocate HD 100453 to fit trend log (Accr Rate) < -9.6 < 2.5x10-10 M yr-1 (1σ) Stellar activity can also be a source of Brγ emission HD 100453 Brγ emission is contaminated by stellar activity Karen Collins Master's Thesis Defense 4/24/2008 Accretion - Herbig-Haro Knots HH knots from jets FUV Are Lyα bright in FUV Use scaling argument HD 163296 has HH knots (Wassell et al. 2006) F122M = 2.0 cnts s1 arcsec2 accretion ~1×107 M yr1 HD 100453 - no knots detected HST ACS SBC F122M 3σ upper limit <1.1x10-4 cnt s-1 arcsec-2 scaling ~<6×1011 M yr1 Karen Collins Master's Thesis Defense 4/24/2008 Accretion- Ca II 8662 Å emission Use scaling argument again HD 163296 Ca II 8662 Å EW = 4.18 Å (Hamann & Persson 1992) accretion rate ~1×107 M yr1 (Wassel et al. 2006) HD 100453 in absorption find emission upper limit Ca II 8662 Å EW <410-3 Å assume linear relation accretion rate <1×1010 M yr1 (4σ) Karen Collins Master's Thesis Defense 4/24/2008 Accretion - Hα HD 100453 Hα emission variable, weak lowest EW of 91 Herbig Ae/Be stars (Manoj et al. 2006) at best a very weak accretor Karen Collins Master's Thesis Defense 4/24/2008 Accretion - X-ray Chandra In A-stars: accretion produces hard X-rays winds produce soft X-rays HD 100453A produces soft X-rays not a strong accretor Chandra X-ray HD 100453A HD 100453B energy (keV) Karen Collins 1 red 0.35 − 0.70 keV green 0.70 − 0.90 keV blue 0.90 − 2.00 keV 2 Master's Thesis Defense 4/24/2008 Accretion Rate Summary Accretion Indicator Accretion Level Significance FUV Continuum < 2.5×1010 M yr1 1 Lack of Ca II 8662 Å emission line < 1.0×1010 M yr1 4 Lack of HH Knots in Ly < ~6×1011 M yr1 factor of 10 weak accretor not strong accretor H X-ray Karen Collins Master's Thesis Defense 4/24/2008 Constraints on Disk Structure From Meeus et al. 2001, 2002 strong IR excess blackbody in NIR inner rim < ~0.5 AU From Habart et al. 2006 M. Sitko, private communication spatially resolved PAH features out to ~0".3 (~40 projected AU) disk outer radius > ~40 AU Habart et al. (2006) Karen Collins Master's Thesis Defense 4/24/2008 HST ACS Coronagraphy Need ~1x106 contrast to image disk around A star Use coronagraph to block light from central star Use psf-subtraction to reduce remaining stray light ACS HRC provides contrast of: ~1x105 in direct mode ~1x106 in coronagraphic mode ~1x107 in coronagraphic mode with psf-subtraction HRC has 0".9 radius spot size, but psf-subtraction residuals out to ~2-3" Clampin et al. 2003 Karen Collins Master's Thesis Defense 4/24/2008 Constraints on Disk Structure HST ACS HRC Coron w/psf-sub HD 100453 psf-subtracted coronagraphic image (HST ACS HRC F606W) HD 100453 Limiting surface brightness from azimuthally averaged radial profile No detection of disk in scattered light psf residuals dominate to ~2-3" scattered light disk < ~250 AU Karen Collins Master's Thesis Defense 4/24/2008 Constraints on Disk Structure Third object in field HST ACS - 2003 (red) HST ACS - 2003 (red) VLT NACO - 2006 (blue) VLT NACO - 2006 (blue) Overlay aligned by diffraction spikes B positioned according to relative motion determined previously C has retrograde relative motion compared to B C proper motion ~ zero Likely a background star Disk is optically thin in the optical and IR by a projected distance of ~90 AU Karen Collins Master's Thesis Defense 4/24/2008 Disk Structure Summary Line of Sight Outer Edge Optically Thin <90 proj. AU (star C) Inner Rim <0.5 AU (NIR BB) A Scattered Light Outer Radius <250 AU Companion 120 proj. AU Outer Radius >40 AU (PAH) i? B Gap (SED dip)? C Karen Collins Master's Thesis Defense 4/24/2008 Gas and Dust in Inner Disk Carmona et al. (2008) found no evidence for molecular hydrogen emission upper limit of ~0.2 MJ of optically thin warm H2 (150 K) upper limit of ~0.007 MJ of optically thin hot H2 (300 K and above) NIR BB in SED hot dust We detected no warm CO emission (4.97 μm) unlike other HAeBe with hot dust Could have optically thick gas in disk midplane Low accretion rate suggests little optically thick or thin gas dust-rich gas-poor inner disk Karen Collins (after Brittain et al. 2007) Master's Thesis Defense 4/24/2008 Gas and Dust in Outer Disk Cold gas (from submm emission line) we found no CO J = 32 (868 m) emission toward HD 100453 cold gas mass of < 0.2 MJ (1000x depletion) Cold dust (from mm continuum) Strong 1.2 mm continuum flux of 265 mJy (Meeus et al. 2003) cold dust mass ~0.1 MJ Gas:dust upper limit is 2:1 (for 1000x depletion) typical protoplanetary disk is 100:1 (like ISM) Gas-poor outer disk Karen Collins Master's Thesis Defense 4/24/2008 Where Does It Belong? 14 ± 4 Myr transitional disk character High NIR excess protoplanetary disk character Low accretion rate transitional or debris disk character Gas-poor disk debris disk character High total IR excess flared disk? requires gas? HD 100453A does not fit in any classically defined disk group (protoplanetary, transitional, debris) Karen Collins Master's Thesis Defense 4/24/2008 Thesis Results Recall we set out to test idea that Meeus Group I sources evolve to Group II ... by comparing ages & accretion between the groups determine for HD 100453 collect new and updated data from literature Karen Collins Master's Thesis Defense 4/24/2008 Thesis Results Group I sources are slightly older than Group II on average (but are within 1σ) Group I accretion rates are slightly lower than Group II accretion rates on average (but are within 1σ) Karen Collins Master's Thesis Defense 4/24/2008 Thesis Results Age range significantly overlaps between the two groups Accretion slows as star ages in both groups Meeus suggested star and disk evolution may be decoupled for this sample We find that the star, accretion rate, and disk evolve together. We conclude that the hypothesis suggesting Meeus Group I sources evolve to Meeus Group II sources does not hold. Karen Collins Master's Thesis Defense 4/24/2008 Possible Physical Explanation HD 100546 example (Group I) after Bouwman et al. 2003) cavity confirmed by interferometry & STIS (Lui et al. 2003) (Grady et al. 2005) inner rim of inner and outer disk creates NIR and MIR blackbody components in SED and high Lexcess/L* possible giant planet in gap is causing collisional cascade collisions produce small dust grains radiation pressure blows the grains onto surface of cold outer disk small grains cause steep submm slope Meeus groups may be more representative of differences in disk structure rather than differences in disk evolution. Karen Collins Master's Thesis Defense 4/24/2008 Future Directions To lift disk structure degeneracy allowed by SED need high contrast, high spatial resolution imaging high spatial resolution interferometry NICMOS on HST (coron. imaging, 0.075 pixel1 , 0".3 hole) My collaborators have submitted a proposal (March 2008) for NICMOS observations of several T Tauri and Herbig Ae/Be stars, including HD 100453. Near-term prospects HST SM4 (8/2008) set to repair other key instruments ACS (down since June 2006) coron. imaging mode, 0.025 pixel1, 0".9 radius spot STIS (down since 2004) coron. imaging mode, 0.05 pixel1, 0".5-2.8" wedges Karen Collins Master's Thesis Defense HD 141569 (from Krist 2004) We can do this with existing instrumentation 4/24/2008 Long -Term Prospects Atacama Large Millimeter Array (ALMA) 0.3 - 9.6 mm (cold dust and gas) 0".01 resolution, no occulter needed 64 x 12-meter antennas completion expected in 2012 Simulation 0.5 M star 1 MJ planet 5 AU orbit Mdisk = 10 MJ Wolf & D'Angelo 2005 Karen Collins Master's Thesis Defense 4/24/2008 Thank You! A possible view of the HD 100453 system? adapted from NASA/JPL-Caltech/T. Pyle (SSC) Karen Collins Master's Thesis Defense 4/24/2008