38,364 research outputs found
Globular cluster population of the HST frontier fields galaxy J07173724+3744224
We present the first measurement of the globular cluster population
surrounding the elliptical galaxy J07173724+3744224 (z=0.1546). This galaxy is
located in the foreground in the field-of-view of the Hubble Space Telescope
(HST) Frontier Fields observations of galaxy cluster MACS J0717.5+3745
(z=0.5458). Based on deep HST ACS F435W, F606W, and F814W images, we find a
total globular cluster population of N_tot = 3441 +/- 1416. Applying the
appropriate extinction correction and filter transformation from ACS F814W to
the Johnson V-band, we determine that the host galaxy has an absolute magnitude
of M_V = -22.2. The specific frequency was found to be S_N = 4.5 +/- 1.8. The
radial profile of the globular cluster system was best fit using a powerlaw of
the form , with the globular cluster population found to
be more extended than the halo light of the host galaxy (). The F435W-F814W colour distribution suggests a bimodal population,
with red globular clusters 1-3x more abundant than blue clusters. These results
are consistent with the host elliptical galaxy J07173724+3744224 having formed
its red metal-rich GCs in situ, with the blue metal-poor globular clusters
accreted from low-mass galaxies.Comment: 21 pages, 14 figures, 2 tables, revised following peer-review,
accepted for publication in MNRA
Silicene Like Domains on IrSi3 Crystallites
Recently, silicene, the graphene equivalent of silicon, has attracted a lot
of attention due to its compatibility with Si-based electronics. So far,
silicene has been epitaxy grown on various crystalline surfaces such as
Ag(110), Ag(111), Ir(111), ZrB2(0001) and Au(110) substrates. Here, we present
a new method to grow silicene via high temperature surface reconstruction of
hexagonal IrSi3 nanocrystals. The h-IrSi3 nanocrystals are formed by annealing
thin Ir layers on Si(111) surface. A detailed analysis of the STM images shows
the formation of silicene like domains on the surface of some of the IrSi3
crystallites. We studied both morphology and electronic properties of these
domains by using both scanning tunneling microscopy/spectroscopy and
first-principles calculation methods
The Brightest Cluster Galaxy in Abell 85: The Largest Core Known so far
We have found that the brightest cluster galaxy (BCG) in Abell~85, Holm 15A,
displays the largest core so far known. Its cusp radius, kpc (), is more than 18 times
larger than the mean for BCGs, and kpc larger than A2261-BCG, hitherto
the largest-cored BCG (Postman, Lauer, Donahue, et al. 2012) Holm 15A hosts the
luminous amorphous radio source 0039-095B and has the optical signature of a
LINER. Scaling laws indicate that this core could host a supermassive black
hole (SMBH) of mass . We
suggest that cores this large represent a relatively short phase in the
evolution of BCGs, whereas the masses of their associated SBMH might be set by
initial conditions.Comment: 14 pages, 3 figure, 2 tables, accepted for publication in ApJ Letters
on October 6th, 2014, replacement of previous manuscript submitted on May
30th, 2014 to astro-p
A Spatial Characterization of the Sagittarius Dwarf Galaxy Tidal Tails
We measure the spatial density of F turnoff stars in the Sagittarius dwarf
tidal stream, from Sloan Digital Sky Survey (SDSS) data, using statistical
photometric parallax. We find a set of continuous, consistent parameters that
describe the leading Sgr stream's position, direction, and width for 15 stripes
in the North Galactic Cap, and 3 stripes in the South Galactic Cap. We produce
a catalog of stars that has the density characteristics of the dominant leading
Sgr tidal stream that can be compared with simulations. We find that the width
of the leading (North) tidal tail is consistent with recent triaxial and
axisymmetric halo model simulations. The density along the stream is roughly
consistent common disruption models in the North, but possibly not in the
South. We explore the possibility that one or more of the dominant Sgr streams
has been mis-identified, and that one or more of the `bifurcated' pieces is the
real Sgr tidal tail, but we do not reach definite conclusions. If two dwarf
progenitors are assumed, fits to the planes of the dominant and `bifurcated'
tidal tails favor an association of the Sgr dwarf spheroidal galaxy with the
dominant Southern stream and the `bifurcated' stream in the North. In the North
Galactic Cap, the best fit Hernquist density profile for the smooth component
of the stellar halo is oblate, with a flattening parameter q = 0.53, and a
scale length of r_0 = 6.73. The Southern data for both the tidal debris and the
smooth component of the stellar halo do not match the model fits to the North,
although the stellar halo is still overwhelmingly oblate. Finally, we verify
that we can reproduce the parameter fits on the asynchronous Milkyway@home
volunteer computing platform.Comment: 35 pages, 8 figures, 9 tables. Accepted for publication in The
Astrophysical Journa
Multi-band Optical and Near-infrared Properties of Faint Submillimeter Galaxies with Serendipitous ALMA Detections
We present a catalog of 26 faint submillimeter galaxies (SMGs) in the XMM-LSS
field identified by cross-matching serendipitously detected sources in archival
ALMA Band 6 and 7 data with multi-band near-infrared (NIR) and optical data
from the Spitzer Extragalactic Representative Volume Survey, the VISTA Deep
Extragalactic Survey, the Canada-France-Hawaii Telescope Legacy Large Survey,
and the Hyper Suprime-Cam Subaru Strategic Program. Of the 26 SMGs in our
sample, 15 are identified here for the first time. The majority of the sources
in our sample (16/26) have faint submm fluxes (). In addition to the 26 SMGs with multi-band optical and NIR
detections, there are 60 highly-reliable () ALMA sources with no
counterpart in any other band down to an IRAC [4.5] magnitude of . To further characterize the 26 galaxies with both ALMA and optical/NIR
counterparts, we provide 13-band forced photometry for the entire catalog using
the Tractor and calculate photometric redshifts and rest-frame colors. The
median redshift of our sample is . We find that our
sample galaxies have bluer colors compared to bright SMGs, and the UVJ color
plot indicates that their colors are consistent with main sequence star-forming
galaxies. Our results provide new insights into the nature of the faint
population of SMGs, and also highlight opportunities for galaxy evolution
studies based on archival ALMA data.Comment: Accepted for publication in ApJ, 32 pages, 11 figures, 4 table
Drug prescription support in dental clinics through drug corpus mining
The rapid increase in the volume and variety of data poses a challenge to safe drug prescription for the dentist. The increasing number of patients that take multiple drugs further exerts pressure on the dentist to make the right decision at point-of-care. Hence, a robust decision support system will enable dentists to make decisions on drug prescription quickly and accurately. Based on the assumption that similar drug pairs have a higher similarity ratio, this paper suggests an innovative approach to obtain the similarity ratio between the drug that the dentist is going to prescribe and the drug that the patient is currently taking. We conducted experiments to obtain the similarity ratios of both positive and negative drug pairs, by using feature vectors generated from term similarities and word embeddings of biomedical text corpus. This model can be easily adapted and implemented for use in a dental clinic to assist the dentist in deciding if a drug is suitable for prescription, taking into consideration the medical profile of the patients. Experimental evaluation of our model’s association of the similarity ratio between two drugs yielded a superior F score of 89%. Hence, such an approach, when integrated within the clinical work flow, will reduce prescription errors and thereby increase the health outcomes of patients
Dark Energy Survey Year 1 results: cosmological constraints from galaxy clustering and weak lensing
We present cosmological results from a combined analysis of galaxy clustering and weak gravitational lensing, using 1321 deg 2 of griz imaging data from the first year of the Dark Energy Survey (DES Y1). We combine three two-point functions: (i) the cosmic shear correlation function of 26 million source galaxies in four redshift bins, (ii) the galaxy angular autocorrelation function of 650,000 luminous red galaxies in five redshift bins, and (iii) the galaxy-shear cross-correlation of luminous red galaxy positions and source galaxy shears. To demonstrate the robustness of these results, we use independent pairs of galaxy shape, photometric redshift estimation and validation, and likelihood analysis pipelines. To prevent confirmation bias, the bulk of the analysis was carried out while blind to the true results; we describe an extensive suite of systematics checks performed and passed during this blinded phase. The data are modeled in flat Λ CDM and w CDM cosmologies, marginalizing over 20 nuisance parameters, varying 6 (for Λ CDM) or 7 (for w CDM) cosmological parameters including the neutrino mass density and including the 457 × 457 element analytic covariance matrix. We find consistent cosmological results from these three two-point functions, and from their combination obtain S 8 ≡σ 8 (Ω m /0.3) 0.5 =0.783 +0.021 −0.025 and Ω m =0.264 +0.032 −0.019 for Λ CDM for w CDM, we find S 8 =0.794 +0.029 −0.027, Ω m =0.279 +0.043 −0.022, and w=−0.80 +0.20 −0.22 at 68% CL. The precision of these DES Y1 results rivals that from the Planck cosmic microwave background measurements, allowing a comparison of structure in the very early and late Universe on equal terms. Although the DES Y1 best-fit values for S 8 and Ω m are lower than the central values from Planck
Minimum Aerosol Layer Detection Sensitivities and Their Subsequent Impacts on Aerosol Optical Thickness Retrievals in CALIPSO Level 2 Data Products
Due to instrument sensitivities and algorithm detection limits, level 2 (L2) Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) 532 nm aerosol extinction profile retrievals are often populated with retrieval fill values (RFVs), which indicate the absence of detectable levels of aerosol within the profile. In this study, using 4 years (20072008 and 20102011) of CALIOP version 3 L2 aerosol data, the occurrence frequency of daytime CALIOP profiles containing all RFVs (all-RFV profiles) is studied. In the CALIOP data products, the aerosol optical thickness (AOT) of any all-RFV profile is reported as being zero, which may introduce a bias in CALIOP-based AOT climatologies. For this study, we derive revised estimates of AOT for all-RFV profiles using collocated Moderate Resolution Imaging Spectroradiometer (MODIS) Dark Target (DT) and, where available, AErosol RObotic NEtwork (AERONET) data. Globally, all-RFV profiles comprise roughly 71 % of all daytime CALIOP L2 aerosol profiles (i.e., including completely attenuated profiles), accounting for nearly half (45 %) of all daytime cloud-free L2 aerosol profiles. The mean collocated MODIS DT (AERONET) 550 nm AOT is found to be near 0.06 (0.08) for CALIOP all-RFV profiles. We further estimate a global mean aerosol extinction profile, a so-called noise floor, for CALIOP all-RFV profiles. The global mean CALIOP AOT is then recomputed by replacing RFV values with the derived noise-floor values for both all-RFV and non-all-RFV profiles. This process yields an improvement in the agreement of CALIOP and MODIS over-ocean AOT
Utility of international normative 20 m shuttle run values for identifying youth at increased cardiometabolic risk
The purpose of this study was to examine the ability of international normative centiles for the 20 m shuttle run test (20mSRT) to identify youth at increased cardiometabolic risk. This was a cross-sectional study involving 961 children aged 10–17 years (53% girls) from the United Kingdom. Receiver operating characteristic (ROC) curves determined the discriminatory ability of cardiorespiratory fitness percentiles for predicting increased cardiometabolic risk. ROC analysis demonstrated a significant but poor discriminatory accuracy of cardiorespiratory fitness in identifying low/high cardiometabolic risk in girls (AUC = 0.58, 95% CI: 0.54–0.63; p = 0.04), and in boys (AUC = 0.59, 95% CI: 0.54–0.63; p = 0.03). The cardiorespiratory fitness cut-off associated with high cardiometabolic risk was the 55th percentile (sensitivity = 33.3%; specificity = 84.5%) in girls and the 60th percentile (sensitivity = 42.9%; specificity = 73.6%) in boys. These 20mSRT percentile thresholds can be used to identify children and adolescents who may benefit from lifestyle intervention. Nonetheless, further work involving different populations and cardiometabolic risk scores comprising of different variables are needed to confirm our initial findings
PM wind generator topologies\ud
The objective of this paper is to provide a comparison among permanent magnet (PM) wind generators of different topologies. Seven configurations are chosen for the comparison, consisting of both radial-flux and axial-flux machines. The comparison is done at seven power levels ranging from 1 to 200 kW. The basis for the comparison is discussed and implemented in detail in the design procedure. The criteria used for comparison are considered to be critical for the efficient deployment of PM wind generators. The design data are optimized and verified by finite-element analysis and commercial generator test results. For a given application, the results provide an indication of the best-suited machine.\u
- …