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Register a new userThe Gray Needle: Large Grains in the HD 15115 Debris Disk from LBT/PISCES/Ks and LBTI/LMIRcam/L Adaptive Optics Imaging
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We present diffraction-limited ks band and lprime adaptive optics images of the edge-on debris disk around the nearby F2 star HD 15115, obtained with a single 8.4 m primary mirror at the Large Binocular Telescope. At ks band the disk is detected at signal-to-noise per resolution element (SNRE) about 3-8 from about 1-2fasec 5 (45-113 AU) on the western side, and from about 1.2-2fasec 1 (63-90 AU) on the east. At lprime the disk is detected at SNRE about 2.5 from about 1-1fasec 45 (45-90 AU) on both sides, implying more symmetric disk structure at 3.8 microns . At both wavelengths the disk has a bow-like shape and is offset from the star to the north by a few AU. A surface brightness asymmetry exists between the two sides of the disk at ks band, but not at lprime . The surface brightness at ks band declines inside 1asec (about 45 AU), which may be indicative of a gap in the disk near 1asec. The ks - lprime disk color, after removal of the stellar color, is mostly grey for both sides of the disk. This suggests that scattered light is coming from large dust grains, with 3-10 microns -sized grains on the east side and 1-10 microns dust grains on the west. This may suggest that the west side is composed of smaller dust grains than the east side, which would support the interpretation that the disk is being dynamically affected by interactions with the local interstellar medium.
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We have used the Submillimeter Array (SMA) to make 1.3 millimeter observations of the debris disk surrounding HD 15115, an F-type star with a putative membership in the beta Pictoris moving group. This nearly edge-on debris disk shows an extreme asymmetry in optical scattered light, with an extent almost two times larger to the west of the star than to the east (originally dubbed the Blue Needle). The SMA observations reveal resolved emission that we model as a circumstellar belt of thermal dust emission. This belt extends to a radius of ~110 AU, coincident with the break in the scattered light profile convincingly seen on the western side of the disk. This outer edge location is consistent with the presence of an underlying population of dust-producing planetesimals undergoing a collisional cascade, as hypothesized in birth ring theory. In addition, the millimeter emission shows a ~3 sigma feature aligned with the asymmetric western extension of the scattered light disk. If this millimeter extension is real, then mechanisms for asymmetry that affect only small grains, such as interactions with interstellar gas, are disfavored. This tentative feature might be explained by secular perturbations to grain orbits introduced by neutral gas drag, as previously invoked to explain asymmetric morphologies of other, similar debris disks.
We present adaptive optics images of the extreme red supergiant VY Canis Majoris in the Ks, L and M bands (2.15 to 4.8 micron) made with LMIRCam on the Large Binocular Telescope (LBT). The peculiar Southwest Clump previously imaged from 1 to 2.2 micron appears prominently in all three filters. We find its brightness is due almost entirely to scattering, with the contribution of thermal emission limited to at most 25%. We model its brightness as optically thick scattering from silicate dust grains using typical size distributions. We find a lower limit mass for this single feature of 5E-03 Msun to 2.5E-02 Msun depending on the assumed gas-to-dust ratio. The presence of the Clump as a distinct feature with no apparent counterpart on the other side of the star is suggestive of an ejection event from a localized region of the star and is consistent with VY CMas history of asymmetric high mass loss events.
We present deep near-infrared (NIR) J, Ks photometry of the old, metal-poor Galactic globular cluster M,15 obtained with images collected with the LUCI1 and PISCES cameras available at the Large Binocular Telescope (LBT). We show how the use of First Light Adaptive Optics system coupled with the (FLAO) PISCES camera allows us to improve the limiting magnitude by ~2 mag in Ks. By analyzing archival HST data, we demonstrate that the quality of the LBT/PISCES color magnitude diagram is fully comparable with analogous space-based data. The smaller field of view is balanced by the shorter exposure time required to reach a similar photometric limit. We investigated the absolute age of M,15 by means of two methods: i) by determining the age from the position of the main sequence turn-off; and ii) by the magnitude difference between the MSTO and the well-defined knee detected along the faint portion of the MS. We derive consistent values of the absolute age of M15, that is 12.9+-2.6 Gyr and 13.3+-1.1 Gyr, respectively.
We present a Subaru/IRCS H-band image of the edge-on debris disk around the F2V star HD 15115. We detected the debris disk, which has a bow shape and an asymmetric surface brightness, at a projected separation of 1--3 (~50--150 AU). The disk surface brightness is ~0.5--1.5 mag brighter on the western side than on the eastern side. We use an inclined annulus disk model to probe the disk geometry. The model fitting suggests that the disk has an inner hole with a radius of 86 AU and an eccentricity of 0.06. The disk model also indicates that the amount of dust on the western side is 2.2 times larger than that on the eastern side. A several Jupiter-mass planet may exist at $gtrsim$45 AU and capture grains at the Lagrangian points to open the eccentric gap. This scenario can explain both the eccentric gap and the difference in the amount of dust. In case of the stellar age of several 100 Myr, a dramatic planetesimal collision possibly causes the dust to increase in the western side. Interstellar medium interaction is also considered as a possible explanation of the asymmetric surface brightness, however, it hardly affect large grains in the vicinity of the inner hole.
We present observations of the HD 15115 debris disk from ALMA at 1.3 mm that capture this intriguing system with the highest resolution ($0.!!^{primeprime}6$ or $29$ AU) at millimeter wavelengths to date. This new ALMA image shows evidence for two rings in the disk separated by a cleared gap. By fitting models directly to the observed visibilities within a MCMC framework, we are able to characterize the millimeter continuum emission and place robust constraints on the disk structure and geometry. In the best-fit model of a power law disk with a Gaussian gap, the disk inner and outer edges are at $43.9pm5.8$ AU ($0.!!^{primeprime}89pm0.!!^{primeprime}12$) and $92.2pm2.4$ AU ($1.!!^{primeprime}88pm0.!!^{primeprime}49$), respectively, with a gap located at $58.9pm4.5$~AU ($1.!!^{primeprime}2pm0.!!^{primeprime}10$) with a fractional depth of $0.88pm0.10$ and a width of $13.8pm5.6$ AU ($0.!!^{primeprime}28pm0.!!^{primeprime}11$). Since we do not see any evidence at millimeter wavelengths for the dramatic east-west asymmetry seen in scattered light, we conclude that this feature most likely results from a mechanism that only affects small grains. Using dynamical modeling and our constraints on the gap properties, we are able to estimate a mass for the possible planet sculpting the gap to be $0.16pm0.06$ $M_text{Jup}$.
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