522 research outputs found
Multiple Gaps in the Disk of the Class I Protostar GY 91
We present the highest spatial resolution ALMA observations to date of the
Class I protostar GY 91 in the Ophiuchus L1688 molecular cloud complex.
Our 870 m and 3 mm dust continuum maps show that the GY 91 disk has a
radius of 80 AU, and an inclination of 40, but most
interestingly that the disk has three dark lanes located at 10 AU, 40 AU, and
70 AU. We model these features assuming they are gaps in the disk surface
density profile and find that their widths are 7 AU, 30 AU, and 10 AU. These
gaps bear a striking resemblance to the gaps seen in the HL Tau disk,
suggesting that there may be Saturn-mass planets hiding in the disk. To
constrain the relative ages of GY 91 and HL Tau, we also model the disk and
envelope of HL Tau and find that they are of similar ages, although GY 91 may
be younger. Although snow lines and magnetic dead zones can also produce dark
lanes, if planets are indeed carving these gaps then Saturn-mass planets must
form within the first 0.5 Myr of the lifetime of protoplanetary disks.Comment: 9 pages, 6 figures, 2 tables. Accepted for publication in Ap
An ALMA Dynamical Mass Estimate of the Proposed Planetary-mass Companion FW Tau C
Dynamical mass estimates down to the planet-mass regime can help to
understand planet formation. We present Atacama Large Millimeter/submillimeter
Array (ALMA) 1.3 mm observations of FW Tau C, a proposed ~10
planet-mass companion at ~330 au from the host binary FW Tau AB. We spatially
and spectrally resolve the accretion disk of FW Tau C in CO (2-1). By
modeling the Keplerian rotation of gas, we derive a dynamical mass of ~0.1
. Therefore, FW Tau C is unlikely a planet, but rather a low-mass star
with a highly inclined disk. This also suggests that FW Tau is a triple system
consisting of three ~0.1 stars.Comment: Accepted for publication in ApJ
WL 17: A Young Embedded Transition Disk
We present the highest spatial resolution ALMA observations to date of the
Class I protostar WL 17 in the Ophiuchus L1688 molecular cloud complex,
which show that it has a 12 AU hole in the center of its disk. We consider
whether WL 17 is actually a Class II disk being extincted by foreground
material, but find that such models do not provide a good fit to the broadband
SED and also require such high extinction that it would presumably arise from
dense material close to the source such as a remnant envelope. Self-consistent
models of a disk embedded in a rotating collapsing envelope can nicely
reproduce both the ALMA 3 mm observations and the broadband SED of WL 17. This
suggests that WL 17 is a disk in the early stages of its formation, and yet
even at this young age the inner disk has been depleted. Although there are
multiple pathways for such a hole to be created in a disk, if this hole were
produced by the formation of planets it could place constraints on the
timescale for the growth of planetesimals in protoplanetary disks.Comment: 7 pages, 3 figures, 2 tables, accepted for publication in ApJ
A VLA Survey For Faint Compact Radio Sources in the Orion Nebula Cluster
We present Karl G. Janksy Very Large Array (VLA) 1.3 cm, 3.6 cm, and 6 cm
continuum maps of compact radio sources in the Orion Nebular Cluster. We
mosaicked 34 square arcminutes at 1.3 cm, 70 square arcminutes at 3.6 cm and
109 square arcminutes at 6 cm, containing 778 near-infrared detected YSOs and
190 HST-identified proplyds (with significant overlap between those
characterizations). We detected radio emission from 175 compact radio sources
in the ONC, including 26 sources that were detected for the first time at these
wavelengths. For each detected source we fit a simple free-free and dust
emission model to characterize the radio emission. We extrapolate the free-free
emission spectrum model for each source to ALMA bands to illustrate how these
measurements could be used to correctly measure protoplanetary disk dust masses
from sub-millimeter flux measurements. Finally, we compare the fluxes measured
in this survey with previously measured fluxes for our targets, as well as four
separate epochs of 1.3 cm data, to search for and quantify variability of our
sources.Comment: 13 pages, 6 figures, 4 tables, ApJ, in pres
Evaluating circadian dysfunction in mouse models of Alzheimer\u27s disease: Where do we stand?
Circadian dysfunction has been described in patients with symptomatic Alzheimer\u27s disease (AD), as well as in presymptomatic phases of the disease. Modeling this circadian dysfunction in mouse models would provide an optimal platform for understanding mechanisms and developing therapies. While numerous studies have examined behavioral circadian function, and in some cases clock gene oscillation, in mouse models of AD, the results are variable and inconsistent across models, ages, and conditions. Ultimately, circadian changes observed in APP/PS1 models are inconsistent across studies and do not always replicate circadian phenotypes observed in human AD. Other models, including the 3xTG mouse, tau transgenic lines, and the accelerated aging SAMP8 line, show circadian phenotypes more consistent with human AD, although the literature is either inconsistent or minimal. We summarize these data and provide some recommendations to improve and standardize future studies of circadian function in AD mouse models
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