Herschel images of Fomalhaut An extrasolar Kuiper belt at the height of its dynamical activity B. Acke, M. Min, C. Dominik, B. Vandenbussche, B. Sibthorpe, C. Waelkens, G. Olofsson, P. Degroote, K. Smolders, E. Pantin, M. J. Barlow, J. A. D. L. Blommaert, A. Brandeker, W. De Meester, W. R. F. Dent, K. Exter, J. Di Francesco, M. Fridlund, W. K. Gear, A. M. Glauser, J. S. Greaves, P. M. Harvey, Th. Henning, M. R. Hogerheijde, W. S. Holland, R. Huygen, R. J. Ivison, C. Jean, R. Liseau, D. A. Naylor, G. L. Pilbratt, E. T. Polehampton, S. Regibo, P. Royer, A. Sicilia- Aguiler, and B. M. Swinyard presented by Richard L. Pearson III University of Denver, AJC May 2, 2012

Outline Fomalhaut introduction Data collection & initial analysis – Geometric properties extrapolation Modeling – The dust – Best model fit (and process to get there) Discussion – Spectral energy distributions – Interior excess emission – Cometary debris – Mass loss 2 1/2

Fomalhaut Overview 3 1/3 1 According to Astronomical League’s Astronomical Pronunciation Guide 2 According to Earth & Sky’s Star Pronunciation Guide 3 According to Sandburg Center for Sky Awareness’ A Skywatcher’s Pronunciation Guide 22 h 57 m 39.1 s, -29° 37’ 20” Andromeda Pisces Pegasus Aquarius Pisces Austrinus Fomalhaut

Fomalhaut Overview 4 2/3 Obtained from HubbleSite, attributed to NASA, ESA, & A. Feild (STScI)

“Controversial” Fomalhaut 5 3/3 Aumann, H. H. 1985, PASP, 97, 885. Kalas, P., Graham, J. R., Chiang, E., et al. 2008, Science, 322, Boley, A. C., Payne, M. J., Corder, S., Dent, W., Ford, E. B., & Shabram, M. 2012, arXiv: v1.

Instrumentation Instrument Physical Resolution (AU) HERSCHEL PACS PACS SPIRE SPIRE SPIRE SPITZER MIPS246 ~ 46 MIPS7018 ~ 137 HUBBLE SPACE TELESCOPE Optical /2 Present Work (with Herschel) vs. Previous Work (with Spitzer)

Herschel Images Smooth features o Indicative of high dust replenishment rate by many collisions Unresolved central star o Excess “stellar” flux attributed to hot dust 1 Interior region not void o Space between center and belt shows (dust) emission o Dust present from in-fall from outer belt or out-fall from unresolved inner belt 7 2/2 1 Absil, O., Mennesson, B., Le Bouquin, J. B., et al. 2009, ApJ,

Geometric Properties from Herschel Images 8 1/2 a Kalas et al. 2005: Using HST images

Inconsistencies in Geometric Properties 9 2/2 Good Okay, except last Bad a Kalas et al. 2005: Using HST images

The Model: dust grain size distributions 10 1/4 1 assuming Poynting-Robertson drag of particles moving inward due to radiation slowing down momentum

The Model: collisional ring radii 11 2/4 Inner Ring Outer Ring

The Model: dust grain composition 12 3/4 1 proposed by Min et al. (2011), derived from solar abundances from Grevesse & Sauval (1998) These are averaged values throughout the disk, so, depending on disk location and hence, radiation dynamics, the particle size distributions are varied

The Model: fitting the model images 13 4/4 1 See Min, M. Dullemond, C. P., Dominik, C., de Koter, A. & Hovenier, J. W. 2009, A&A, 497, 155.

MCMax 14 1/1

Spectral Energy Distributions (SEDs) 15 1/2 interior excess

Interior Excess SED 16 2/2 1 Absil O., Mennesson, B. Le Bouquin, J. B., et al. An interformetric strudy of the Fomalhaut inner debris disk. I. Near-infrared detection of hot dust with VLTI/VINCI. 2009, ApJ, 704, 150.

Interior Excess Emission 17 2/2 1 From Panagia & Felli (1975)

Cometary Debris “grains that absorb and emit like small grains, but scatter like large particles” – Based on scattered light & thermal IR images – i.e. fluffy aggregates – e.g. cometary dust (like in our solar system) Most of the light scattered is not into our line of sight, providing apparently low scattering cross sections They do exclude very large compact grains, as these grains do not have the thermal properties needed to explain the far-IR images and SED 18 1/3 1 From Panagia & Felli (1975)

Comet Mass Loss 19 2/3

Comet Population 20 3/3

Conclusion Open up discussion of free-free emission in interior, diffuse region High-mass in blow-out particles, evidence of extreme activity Dust particles are fluffy aggregates similar to cometary particles in our own solar system 21