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Hubble "Traps" a Vermin Galaxy

The NASA/ESA Hubble Space Telescope is famous for its jaw-dropping snapshots of the cosmos. At first glance this Picture of the Week appears to be quite the opposite, showing just a blur of jagged spikes, speckled noise, and weird, clashing colors - but once you know what you are looking at, images like this one are no less breathtaking.
This shows a distant galaxy - visible as the smudge to the lower right - as it begins to align with and pass behind a star sitting nearer to us within the Milky Way. This is an event known as a transit. The star is called HD 107146, and it sits at the center of the frame. Its light has been blocked in this image to make its immediate surroundings and the faint galaxy visible - the position of the star is marked with a green circle.

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Title: ALMA observations of the debris disk around the young Solar Analogue HD 107146
Author: L. Ricci, J. M. Carpenter, B. Fu, A. M. Hughes, S. Corder, A. Isella

We present ALMA continuum observations at a wavelength of 1.25 mm of the debris disk surrounding the ~ 100 Myr old solar analogue HD 107146. The continuum emission extends from about 30 to 150 AU from the central star with a decrease in the surface brightness at intermediate radii. We analyse the ALMA interferometric visibilities using debris disk models with radial profiles for the dust surface density parametrised as i) a single power-law, ii) a single power-law with a gap, and iii) a double power-law. We find that models with a gap of radial width ~8 AU at a distance of ~80 AU from the central star, as well as double power-law models with a dip in the dust surface density at ~70 AU provide significantly better fits to the ALMA data than single power-law models. We discuss possible scenarios for the origin of the HD 107146 debris disk using models of planetesimal belts in which the formation of Pluto-sized objects trigger disruptive collisions of large bodies, as well as models which consider the interaction of a planetary system with a planetesimal belt and spatial variation of the dust opacity across the disk. If future observations with higher angular resolution and sensitivity confirm the fully-depleted gap structure discussed here, a planet with a mass of approximately a few Earth masses in a nearly circular orbit at ~80 AU from the central star would be a possible explanation for the presence of the gap.

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Title: Multi-wavelength modelling of the spatially resolved debris disk of HD 107146
Authors: Steve Ertel, Sebastian Wolf, Stanimir Metchev, Glenn Schneider, John M. Carpenter, Michael R. Meyer, Lynne A. Hillenbrand, Murray D. Silverstone

We aim to constrain the location, composition, and dynamical state of planetesimal populations and dust around the young, sun-like (G2V) star HD 107146}. We consider coronagraphic observations obtained with the Advanced Camera for Surveys (HST/ACS) onboard the HST in broad V and broad I filters, a resolved 1.3mm map obtained with the Combined Array for Research in Millimetre-Wave Astronomy (CARMA), Spitzer/IRS low resolution spectra, and the spectral energy distribution (SED) of the object at wavelengths ranging from 3.5micron to 3.1mm. We complement these data with new coronagraphic high resolution observations of the debris disk using the Near Infrared Camera and Multi-Object Spectrometer (HST/NICMOS) aboard the HST in the F110W filter. The SED and images of the disk in scattered light as well as in thermal reemission are combined in our modelling using a parameterised model for the disk density distribution and optical properties of the dust. A detailed analytical model of the debris disk around HD 107146 is presented that allows us to reproduce the almost entire set of spatially resolved and unresolved multi-wavelength observations. Considering the variety of complementary observational data, we are able to break the degeneracies produced by modelling SED data alone. We find the disk to be an extended ring with a peak surface density at 131AU. Furthermore, we find evidence for an additional, inner disk probably composed of small grains released at the inner edge of the outer disk and moving inwards due to Poynting-Robertson drag. A birth ring scenario (i.e., a more or less broad ring of planetesimals creating the dust disk trough collisions) is found to be the most likely explanation of the ringlike shape of the disk.

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Title: A Resolved Ring of Debris Dust Around the Solar Analog HD 107146
Authors: S. A. Corder, J. M. Carpenter, A. I. Sargent, B. A. Zauderer, M. C. H. Wright, S. White, D. P. Woody, P. Teuben, S. L. Scott, M. W. Pound, R. L. Plambeck, J. W. Lamb, J. Koda, M. W. Hodges, D. W. Hawkins, D. C.-J. Bock
(Version v2)

We present resolved images of the dust continuum emission from the debris disk around the young (80-200 Myr) solar-type star HD 107146 with CARMA at \lambda 1.3 mm and the CSO at \lambda 350 \mu m. Both images show that the dust emission extends over an ~10\arcsec diameter region. The high resolution (3\arcsec) CARMA image further reveals that the dust is distributed in a partial ring with significant decrease in flux inward of 97 AU. Two prominent emission peaks appear within the ring separated by ~140 degrees in position angle. The morphology of the dust emission is suggestive of dust captured into a mean motion resonance, which would imply the presence of a planet at an orbital radius of ~45-75 AU.

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