We present high-resolution (∼300 au) Atacama Large Millimeter/submillimeter Array observations of the massive young stellar object G11.92-0.61 MM 1. We resolve the immediate circumstellar environment ...of MM 1 in 1.3 mm continuum emission and CH3CN emission for the first time. The object divides into two main sources-MM 1a, which is the source of a bipolar molecular outflow, and MM 1b, located 0 57 (1920 au) to the southeast. The main component of MM 1a is an elongated continuum structure, perpendicular to the bipolar outflow, with a size of 0 141 × 0 050 (480 × 170 au). The gas kinematics toward MM 1a probed via CH3CN trace a variety of scales. The lower energy J = 12-11 K = 3 line traces extended, rotating gas within the outflow cavity, while the v8 = 1 line shows a clearly resolved Keplerian rotation signature. Analysis of the gas kinematics and dust emission shows that the total enclosed mass in MM 1a is 40 5 M (where between 2.2 and 5.8 M is attributed to the disk), while MM 1b is <0.6 M . The extreme mass ratio and orbital properties of MM 1a and MM 1b suggest that MM 1b is one of the first observed examples of the formation of a binary star via disk fragmentation around a massive young (proto)star.
Near-infrared H- and K-band spectra are presented for 247 objects, selected from the Red MSX Source (RMS) survey as potential young stellar objects (YSOs). 195 (∼80 per cent) of the targets are YSOs, ...of which 131 are massive YSOs (L
BOL > 5 × 103 L, M > 8 M). This is the largest spectroscopic study of massive YSOs to date, providing a valuable resource for the study of massive star formation. In this paper, we present our exploratory analysis of the data. The YSOs observed have a wide range of embeddedness (2.7 < A
V
< 114), demonstrating that this study covers minimally obscured objects right through to very red, dusty sources. Almost all YSOs show some evidence for emission lines, though there is a wide variety of observed properties. The most commonly detected lines are Brγ, H2, fluorescent Fe ii, CO bandhead, Fe ii and He i 2-1 1S-1P, in order of frequency of occurrence. In total, ∼40 per cent of the YSOs display either fluorescent Fe ii 1.6878 μm or CO bandhead emission (or both), indicative of a circumstellar disc; however, no correlation of the strength of these lines with bolometric luminosity was found. We also find that ∼60 per cent of the sources exhibit Fe ii or H2 emission, indicating the presence of an outflow. Three quarters of all sources have Brγ in emission. A good correlation with bolometric luminosity was observed for both the Brγ and H2 emission line strengths, covering 1 < L
BOL < 3.5 × 105 L. This suggests that the emission mechanism for these lines is the same for low-, intermediate- and high-mass YSOs, i.e. high-mass YSOs appear to resemble scaled-up versions of low-mass YSOs.
The LOFAR Two-metre Sky Survey Shimwell, T. W.; Röttgering, H. J. A.; Best, P. N. ...
Astronomy and astrophysics (Berlin),
02/2017, Volume:
598
Journal Article
Peer reviewed
Open access
The LOFAR Two-metre Sky Survey (LoTSS) is a deep 120–168 MHz imaging survey that will eventually cover the entire northern sky. Each of the 3170 pointings will be observed for 8 h, which, at most ...declinations, is sufficient to produce ∼5 resolution images with a sensitivity of ∼100 µJy/beam and accomplish the main scientific aims of the survey, which are to explore the formation and evolution of massive black holes, galaxies, clusters of galaxies and large-scale structure. Owing to the compact core and long baselines of LOFAR, the images provide excellent sensitivity to both highly extended and compact emission. For legacy value, the data are archived at high spectral and time resolution to facilitate subarcsecond imaging and spectral line studies. In this paper we provide an overview of the LoTSS. We outline the survey strategy, the observational status, the current calibration techniques, a preliminary data release, and the anticipated scientific impact. The preliminary images that we have released were created using a fully automated but direction-independent calibration strategy and are significantly more sensitive than those produced by any existing large-area low-frequency survey. In excess of 44 000 sources are detected in the images that have a resolution of 25 , typical noise levels of less than 0.5 mJy/beam, and cover an area of over 350 square degrees in the region of the HETDEX Spring Field (right ascension 10h45m00s to 15h30m00s and declination 45 • 00 00 to 57 • 00 00).
We present the results of a recent re-reduction of the data from the Very Large Array (VLA) Low-frequency Sky Survey (VLSS). We used the VLSS catalogue as a sky model to correct the ionospheric ...distortions in the data and create a new set of sky maps and corresponding catalogue at 73.8 MHz. The VLSS Redux (VLSSr) has a resolution of 75 arcsec, and an average map rms noise level of σ ∼ 0.1 Jy beam−1. The clean bias is 0.66 × σ and the theoretical largest angular size is 36 arcmin. Six previously unimaged fields are included in the VLSSr, which has an unbroken sky coverage over 9.3 sr above an irregular southern boundary. The final catalogue includes 92 964 sources. The VLSSr improves upon the original VLSS in a number of areas including imaging of large sources, image sensitivity, and clean bias; however the most critical improvement is the replacement of an inaccurate primary beam correction which caused source flux errors which vary as a function of radius to nearest pointing centre in the VLSS.
The interaction of the solar wind with Earth's magnetosphere gives rise to the bright polar aurorae and to geomagnetic storms, but the relation between the solar wind and the dynamics of the outer ...planets' magnetospheres is poorly understood. Jupiter's magnetospheric dynamics and aurorae are dominated by processes internal to the jovian system, whereas Saturn's magnetosphere has generally been considered to have both internal and solar-wind-driven processes. This hypothesis, however, is tentative because of limited simultaneous solar wind and magnetospheric measurements. Here we report solar wind measurements, immediately upstream of Saturn, over a one-month period. When combined with simultaneous ultraviolet imaging we find that, unlike Jupiter, Saturn's aurorae respond strongly to solar wind conditions. But in contrast to Earth, the main controlling factor appears to be solar wind dynamic pressure and electric field, with the orientation of the interplanetary magnetic field playing a much more limited role. Saturn's magnetosphere is, therefore, strongly driven by the solar wind, but the solar wind conditions that drive it differ from those that drive the Earth's magnetosphere.
Fabry disease is a rare X-linked lysosomal storage disorder characterised by severe multisystemic involvement that leads to major organ failure and premature death in affected men and women. Over the ...past 7 years, the Fabry Outcome Survey (FOS) has collected data on the natural history of Fabry disease, and the long-term efficacy and safety of enzyme-replacement therapy. This paper provides an update on the first analysis of FOS data.
Baseline data on clinical manifestations and causes of death in a cohort of 1453 patients (699 male, 754 female) from 19 countries worldwide were analysed. Causes of death of affected relatives were analysed separately.
The most frequently reported signs and symptoms of Fabry disease were neurological. Cardiac, ocular, gastrointestinal, dermatological, auditory and renal manifestations were also common. The principal causes of death among 181 affected relatives of patients in FOS (most of whom had died before 2001) were renal failure in males (42%) and cerebrovascular disease in females (25%). In contrast, of the 42 patients enrolled in FOS whose deaths were reported between 2001 and 2007, cardiac disease was the main cause of death in both male (34%) and female (57%) patients.
These data suggest that the importance of renal disease as a cause of death in patients with Fabry disease is decreasing while the importance of cardiac disease is increasing. This pattern probably reflects improvements in the management of renal disease in patients with Fabry disease.
Kisspeptin is the product of the Kiss1 gene that regulates GnRH secretion. In sheep, Kiss1 mRNA-expressing cells are found in the preoptic area (POA) and arcuate nucleus (ARC), and expression is ...up-regulated in the caudal ARC during the periovulatory period. We hypothesized that kisspeptin neurons in the ARC are activated by estradiol-17β prior to the preovulatory LH surge. Ovariectomized ewes were treated as follows: 1) estradiol-17β implants (sc 2 wk) to cause tonic negative feedback; 2) vehicle (no estrogen negative or positive feedback); or 3) positive feedback/GnRH surge-inducing injection of estradiol-17β (50 μg iv). For groups 2 and 3, brains were collected 1 h after treatment and kisspeptin/Fos immunoreactivity was examined. In the caudal and mid-ARC, the percentage of kisspeptin cells that were Fos immunoreactive increased after acute estradiol treatment (group 3) over that seen in the other two groups. Kisspeptin/Fos colocalization was also quantified in ewes during the luteal and late-follicular phase of the estrous cycle, showing a trend toward an increase in colocalization in the late-follicular phase. Kisspeptin/Fos colocalization was similar in the POA across groups in both experiments. Analysis of Kiss1 mRNA by in situ hybridization revealed an increase in expression during the late-follicular phase in the caudal ARC and POA. These data suggest kisspeptin neurons located in the caudal extent of the ARC are involved in generating the positive feedback preovulatory GnRH/LH surge in the ewe, but there may also be a role for Kiss1-expressing cells in the POA.
Estradiol stimulates the activation of kisspeptin neurons located in the arcuate nucleus of the brain, which leads to the estradiol positive feedback preovulatory GnRH/LH surge in the ewe.
Rapid, accurate assessment of the yield of a large-scale urban explosion will assist in implementing emergency response plans, will facilitate better estimates of areas at risk of high damage and ...casualties, and will provide policy makers and the public with more accurate information about the event. On 4 August 2020, an explosion occurred in the Port of Beirut, Lebanon. Shortly afterwards, a number of videos were posted to social media showing the moment of detonation and propagation of the resulting blast wave. In this article, we present a method to rapidly calculate explosive yield based on analysis of 16 videos with a clear line-of-sight to the explosion. The time of arrival of the blast is estimated at 38 distinct positions, and the results are correlated with well-known empirical laws in order to estimate explosive yield. The best estimate and reasonable upper limit of the 2020 Beirut explosion determined from this method are 0.50 kt TNT and 1.12 kt TNT, respectively.
Population numbers at local levels are fundamental data for many applications, including the delivery and planning of services, election preparation, and response to disasters. In resource-poor ...settings, recent and reliable demographic data at subnational scales can often be lacking. National population and housing census data can be outdated, inaccurate, or missing key groups or areas, while registry data are generally lacking or incomplete. Moreover, at local scales accurate boundary data are often limited, and high rates of migration and urban growth make existing data quickly outdated. Here we review past and ongoing work aimed at producing spatially disaggregated local-scale population estimates, and discuss how new technologies are now enabling robust and cost-effective solutions. Recent advances in the availability of detailed satellite imagery, geopositioning tools for field surveys, statistical methods, and computational power are enabling the development and application of approaches that can estimate population distributions at fine spatial scales across entire countries in the absence of census data. We outline the potential of such approaches as well as their limitations, emphasizing the political and operational hurdles for acceptance and sustainable implementation of new approaches, and the continued importance of traditional sources of national statistical data.
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