205 research outputs found
The M81 Group Dwarf Irregular Galaxy DDO 165. II. Connecting Recent Star Formation with ISM Structures and Kinematics
We compare the stellar populations and complex neutral gas dynamics of the
M81 group dIrr galaxy DDO 165 using data from the HST and the VLA. Paper I
identified two kinematically distinct HI components, multiple localized high
velocity gas features, and eight HI holes and shells (the largest of which
spans ~2.2x1.1 kpc). Using the spatial and temporal information from the
stellar populations in DDO 165, we compare the patterns of star formation over
the past 500 Myr with the HI dynamics. We extract localized star formation
histories within 6 of the 8 HI holes identified in Paper I, as well as 23 other
regions that sample a range of stellar densities and neutral gas properties.
From population synthesis modeling, we derive the energy outputs (from stellar
winds and supernovae) of the stellar populations within these regions over the
last 100 Myr, and compare with refined estimates of the energies required to
create the HI holes. In all cases, we find that "feedback" is energetically
capable of creating the observed structures in the ISM. Numerous regions with
significant energy inputs from feedback lack coherent HI structures but show
prominent localized high velocity gas features; this feedback signature is a
natural product of temporally and spatially distributed star formation. In DDO
165, the extended period of heightened star formation activity (lasting more
than 1 Gyr) is energetically capable of creating the observed holes and high
velocity gas features in the neutral ISM.Comment: The Astrophysical Journal, in press. Full-resolution version
available on request from the first autho
The M81 Group Dwarf Irregular Galaxy DDO 165. I. High Velocity Neutral Gas in a Post-Starburst System
We present new multi-configuration VLA HI spectral line observations of the
M81 group dIrr post-starburst galaxy DDO 165. The HI morphology is complex,
with multiple column density peaks surrounding a large region of very low HI
surface density that is offset from the center of the stellar distribution. The
bulk of the neutral gas is associated with the southern section of the galaxy;
a secondary peak in the north contains ~15% of the total HI mass. These
components appear to be kinematically distinct, suggesting that either tidal
processes or large-scale blowout have recently shaped the ISM of DDO 165. Using
spatially-resolved position-velocity maps, we find multiple localized
high-velocity gas features. Cross-correlating with radius-velocity analyses, we
identify eight shell/hole structures in the ISM with a range of sizes (~400-900
pc) and expansion velocities (~7-11 km/s). These structures are compared with
narrow- and broad-band imaging from KPNO and HST. Using the latter data, recent
works have shown that DDO 165's previous "burst" phase was extended temporally
(>1 Gyr). We thus interpret the high-velocity gas features, HI holes, and
kinematically distinct components of the galaxy in the context of the immediate
effects of "feedback" from recent star formation. In addition to creating HI
holes and shells, extended star formation events are capable of creating
localized high velocity motion of the surrounding interstellar material. A
companion paper connects the energetics from the HI and HST data.Comment: The Astrophysical Journal, in press. Full-resolution version
available on request from the first autho
Physical Properties and Gas Hydrate at a Near-Seafloor Thrust Fault, Hikurangi Margin, New Zealand
The selection of comparators for randomized controlled trials of health-related behavioral interventions : recommendations of an NIH expert panel
Funding and logistical support for the expert panel was provided by the National Institutes of Health Office of Behavioral and Social Sciences Research.Peer reviewedPostprin
Testing gravitational-wave searches with numerical relativity waveforms: Results from the first Numerical INJection Analysis (NINJA) project
The Numerical INJection Analysis (NINJA) project is a collaborative effort
between members of the numerical relativity and gravitational-wave data
analysis communities. The purpose of NINJA is to study the sensitivity of
existing gravitational-wave search algorithms using numerically generated
waveforms and to foster closer collaboration between the numerical relativity
and data analysis communities. We describe the results of the first NINJA
analysis which focused on gravitational waveforms from binary black hole
coalescence. Ten numerical relativity groups contributed numerical data which
were used to generate a set of gravitational-wave signals. These signals were
injected into a simulated data set, designed to mimic the response of the
Initial LIGO and Virgo gravitational-wave detectors. Nine groups analysed this
data using search and parameter-estimation pipelines. Matched filter
algorithms, un-modelled-burst searches and Bayesian parameter-estimation and
model-selection algorithms were applied to the data. We report the efficiency
of these search methods in detecting the numerical waveforms and measuring
their parameters. We describe preliminary comparisons between the different
search methods and suggest improvements for future NINJA analyses.Comment: 56 pages, 25 figures; various clarifications; accepted to CQ
Further clinical and molecular delineation of the 15q24 microdeletion syndrome
Background Chromosome 15q24 microdeletion syndrome is a rare genomic disorder characterised by intellectual disability, growth retardation, unusual facial morphology and other anomalies. To date, 20 patients have been reported; 18 have had detailed breakpoint analysis. Aim To further delineate the features of the 15q24 microdeletion syndrome, the clinical and molecular characterisation of fifteen patients with deletions in the 15q24 region was performed, nearly doubling the number of reported patients. Methods Breakpoints were characterised using a custom, high-density array comparative hybridisation platform, and detailed phenotype information was collected for each patient. Results Nine distinct deletions with different breakpoints ranging in size from 266 kb to 3.75 Mb were identified. The majority of breakpoints lie within segmental duplication (SD) blocks. Low sequence identity and large intervals of unique sequence between SD blocks likely contribute to the rarity of 15q24 deletions, which occur 8-10 times less frequently than 1q21 or 15q13 microdeletions in our series. Two small, atypical deletions were identified within the region that help delineate the critical region for the core phenotype in the 15q24 microdeletion syndrome. Conclusion The molecular characterisation of these patients suggests that the core cognitive features of the 15q24 microdeletion syndrome, including developmental delays and severe speech problems, are largely due to deletion of genes in a 1.1-Mb critical region. However, genes just distal to the critical region also play an important role in cognition and in the development of characteristic facial features associated with 15q24 deletions. Clearly, deletions in the 15q24 region are variable in size and extent. Knowledge of the breakpoints and size of deletion combined with the natural history and medical problems of our patients provide insights that will inform management guidelines. Based on common phenotypic features, all patients with 15q24 microdeletions should receive a thorough neurodevelopmental evaluation, physical, occupational and speech therapies, and regular audiologic and ophthalmologic screenin
LSST Science Book, Version 2.0
A survey that can cover the sky in optical bands over wide fields to faint
magnitudes with a fast cadence will enable many of the exciting science
opportunities of the next decade. The Large Synoptic Survey Telescope (LSST)
will have an effective aperture of 6.7 meters and an imaging camera with field
of view of 9.6 deg^2, and will be devoted to a ten-year imaging survey over
20,000 deg^2 south of +15 deg. Each pointing will be imaged 2000 times with
fifteen second exposures in six broad bands from 0.35 to 1.1 microns, to a
total point-source depth of r~27.5. The LSST Science Book describes the basic
parameters of the LSST hardware, software, and observing plans. The book
discusses educational and outreach opportunities, then goes on to describe a
broad range of science that LSST will revolutionize: mapping the inner and
outer Solar System, stellar populations in the Milky Way and nearby galaxies,
the structure of the Milky Way disk and halo and other objects in the Local
Volume, transient and variable objects both at low and high redshift, and the
properties of normal and active galaxies at low and high redshift. It then
turns to far-field cosmological topics, exploring properties of supernovae to
z~1, strong and weak lensing, the large-scale distribution of galaxies and
baryon oscillations, and how these different probes may be combined to
constrain cosmological models and the physics of dark energy.Comment: 596 pages. Also available at full resolution at
http://www.lsst.org/lsst/sciboo
The First Post-Kepler Brightness Dips of KIC 8462852
We present a photometric detection of the first brightness dips of the unique variable star KIC 8462852 since the end of the Kepler space mission in 2013 May. Our regular photometric surveillance started in 2015 October, and a sequence of dipping began in 2017 May continuing on through the end of 2017, when the star was no longer visible from Earth. We distinguish four main 1%-2.5% dips, named Elsie, Celeste, Skara Brae, and Angkor, which persist on timescales from several days to weeks. Our main results so far are as follows: (i) there are no apparent changes of the stellar spectrum or polarization during the dips and (ii) the multiband photometry of the dips shows differential reddening favoring non-gray extinction. Therefore, our data are inconsistent with dip models that invoke optically thick material, but rather they are in-line with predictions for an occulter consisting primarily of ordinary dust, where much of the material must be optically thin with a size scale ≪1 μm, and may also be consistent with models invoking variations intrinsic to the stellar photosphere. Notably, our data do not place constraints on the color of the longer-term secular dimming, which may be caused by independent processes, or probe different regimes of a single process
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