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Register a new userFeasibility of the debris ring transit method for the solar-like star HD 107146 by an occulted galaxy
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Authors
L. van Sluijs
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Occulting galaxy pairs have been used to determine the transmission and dust composition within the foreground galaxy. Observations of the nearly face-on ring-like debris disk around the solar-like star HD 107146 by HST/ACS in 2004 and HST/STIS in 2011 reveal that the debris ring is occulting an extended background galaxy over the subsequent decades. Our aim is to use 2004 HST observations of this system to model the galaxy and apply this to the 2011 observation in order to measure the transmission of the galaxy through the outer regions of the debris disk. We model the galaxy with an exponential disk and a S{e}rsic pseudo-bulge in the V- and I-band, but irregularities due to small scale structure from star forming regions limits accurate determination of the foreground dust distribution. We show that debris ring transit photometry is feasible for optical depth increases of $Delta tau geq$ 0.04 ($1 sigma$) on tens of au scales the width of the background galaxy { when the 2011 STIS data are compared directly with new HST/STIS observations, instead of the use of a smoothed model as a reference.
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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 $sim$10arcsec diameter region. The high resolution (3arcsec) 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 $sim$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 $sim$45-75 AU.
We present resolved scattered-light images of the debris disk around HD 107146, a G2 star 28.5 pc from the Sun. This is the first debris disk to be resolved in scattered light around a solar-type star. We observed it with the HST/ACS coronagraph, using a 1.8 occulting spot and the F606W (broad V) and F814W (broad I) filters. Within 2 from the star, the image is dominated by PSF subtraction residuals. Outside this limit, the disk looks featureless except for a northeast-southwest brightness asymmetry that we attribute to forward scattering. The disk has scattered-light fractional luminosities of $(L_{Sca}/L_*)_{F606W}=6.8 pm 0.8 times 10^{-5}$ and $(L_{Sca}/L_*)_{F814W}=10 pm 1 times 10^{-5}$ and it is detected up to 6.5 away from the star. To map the surface density of the disk, we deproject it by $25^circ pm 5^circ$, divide by the dust scattering phase ($g_{F606W} = 0.3 pm 0.1$, $g_{F814W} = 0.2 pm 0.1$) and correct for the geometric dilution of starlight. Within the errors, the surface density has the same shape in each bandpass, and it appears to be a broad (85 AU) ring with most of the opacity concentrated at 130 AU. The ratio of the relative luminosity in F814W to that in F606W has the constant value of $1.3pm0.3$, with the error dominated by uncertainties in the value of $g$ in each filter. An examination of far infrared and submillimeter measurements suggests the presence of small grains. The colors and the derived values of $g$ are consistent with the presence of dust particles smaller than the radiation pressure limit. The dust generated by the creation of a small planet or the scattering and circularization of a large one, are possible scenarios that may explain the shape of the surface density profile.
We present 880 um Submillimeter Array observations of the debris disks around the young solar analogue HD 107146 and the multiple-planet host star HR 8799, at an angular resolution of 3 and 6, respectively. We spatially resolve the inner edge of the disk around HR 8799 for the first time. While the data are not sensitive enough (with rms noise of 1 mJy) to constrain the system geometry, we demonstrate that a model by Su et al. (2009) based on the spectral energy distribution (SED) with an inner radius of 150 AU predicts well the spatially resolved data. Furthermore, by modeling simultaneously the SED and visibilities, we demonstrate that the dust is distributed in a broad (of order 100 AU) annulus rather than a narrow ring. We also model the observed SED and visibilities for the HD 107146 debris disk and generate a model of the dust emission that extends in a broad band between 50 and 170 AU from the star. We perform an a posteriori comparison with existing 1.3 mm CARMA observations and demonstrate that a smooth, axisymmetric model reproduces well all of the available millimeter-wavelength data.
Dust in debris discs is constantly replenished by collisions between larger objects. In this paper, we investigate a method to detect these collisions. We generate models based on recent results on the Fomalhaut debris disc, where we simulate a background star transiting behind the disc, due to the proper motion of Fomalhaut. By simulating the expanding dust clouds caused by the collisions in the debris disc, we investigate whether it is possible to observe changes in the brightness of the background star. We conclude that in the case of the Fomalhaut debris disc, changes in the optical depth can be observed, with values of the optical depth ranging from $10^{-0.5}$ for the densest dust clouds to $10^{-8}$ for the most diffuse clouds with respect to the background optical depth of $sim1.2times10^{-3}$.
Recent observations of resolved cold debris disks at tens of au have revealed that gaps could be a common feature in these Kuiper belt analogues. Such gaps could be evidence for the presence of planets within the gaps or closer-in near the edges of the disk. We present SPHERE observations of HD 92945 and HD 107146, two systems with detected gaps. We constrained the mass of possible companions responsible for the gap to 1-2 M Jup for planets located inside the gap and to less than 5 M Jup for separations down to 20 au from the host star. These limits allow us to exclude some of the possible configurations of the planetary systems proposed to explain the shape of the disks around these two stars. In order to put tighter limits on the mass at very short separations from the star, where direct imaging data are less effective, we also combined our data with astrometric measurements from Hipparcos and Gaia and radial velocity measurements. We were able to limit the separation and the mass of the companion potentially responsible for the proper motion anomaly of HD 107146 to values of 2-7 au and 2-5 M Jup , respectively.
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