1. Young Stellar Objects: The Inner AU John D. Monnier University of Michigan Art Credit: Luis Belerique Collaborators Ajay Tannirkulam (UM)Rafael Millan-Gabet (Caltech) Tim Harries (Exeter)Peter Tuthill (Sydney) Wes Traub (CfA)Jean-Philippe Berger (Grenoble) Rachel Akeson (Caltech)Theo ten Brummelaar (GSU) Ettore Pedretti (St. Andrews) Nathalie Thureau (Cambridge) and IOTA/iKeck/CHARA teams

2. Art Credit: Luis Belerique Standard Disk Model (Herbig Ae/Be and T Tauris) Gas and Dust in (sub?) orbits Gas and Dust in (sub?) Keplerian orbits disk flaring, physical conditions of planet formation Dust Evaporation Front dust properties, disk scale height Gas line emission, Only inner disk winds Matter Falls onto Star (accretion) jets, magnetic fields 1 AU X 1 AU 0.01” X 0.01”

3. Young Stellar Objects (e.g., Hillenbrand et al. 1992 + flaring) Flat, Optically-thick Disk Model from 1990s (e.g., Tuthill et al 2001; Natta et al. 2001; Monnier & Millan-Gabet 2006) Optically-thin Cavity Disk Model

4. Comprehensive Size-Luminosity Plot (from Protostars & Planets V Review, Millan-Gabet et al. 2006) Monnier & Millan-Gabet (2002, ApJ 579, 694 ) Millan-Gabet et al. (2001, ApJ, 546, 358) Eisner et al. (2003, ApJ, 588, 360) Wilkin & Akeson (2003, Ap&SS, 286, 145) Eisner et al. (2004, ApJ, 613, 1049) Akeson et al. (2004, ApJ, 622, 440) Eisner et al. (2005, ApJ, 623, 952) Monnier et al. (2005, ApJ 624, 832) Akeson et al. (2005, ApJ 635 1173) Flat, Optically-thick Optically-thin Cavity

5. Swept under the rug… Vertical wall problems.. IR excess not very inclination dependent (Isella & Natta 2005) IOTA interferometer found small closure phase (Monnier et al. 2006) In detail, observed sizes are much too small for some objects when taking into account disk backwarming (e.g., Isella et al. 2006) Lambda-dependence on size (Eisner et al. 2006) Gas emission component? (RY Tau, Akeson et al. 2005)

6. Dust settling and/or growth curves hot inner wall… Tannirkulam et al. 2007 Tannirkulam, Harries & Monnier 2007

7. Tannirkulam et al. 2007 Tannirkulam et al. 2007 (see poster)

8. CHARA Interferometer Georgia State University 330 meters 1 milliarcsecond resolution at K band 1/10 AU for the closest YSOs

9. MWC 275 (see Tannirkulam et al. 2007, in prep) Gas emission? Pure “hot inner rim” models can not fit the CHARA data at long baselines (>200meters); gas emission within the evaporation radius can explain our new data.

10. Golden Age for YSO Interferometry Inner Disks of Young Stellar Objects Well-defined near-IR size-luminosity relation (Monnier et al. 2005) Gas disk detected New flood of mid-infrared sizes (VLTI + Keck) Silicates of inner disk are more crystalline (van Boekel et al.) T Tauri and FU Ori objects, too! (Millian-Gabet, Akeson et al. 2006) Sizes of spectral line emitting regions: Br-gamma (Tatulli et al.) and CO bandhead (Eisner et al) Imaging with CHARA/MIRC and VLTI Art Credit: Luis Belerique