Thin radiating shock layer about a blunt body

Boundary layer flow in thin shock layer about axisymmetric blunt bodies studied by Blasius type series expansion techniqu

Determining the HI content of galaxies via intensity mapping cross-correlations

We propose an innovative method for measuring the neutral hydrogen (HI) content of an optically-selected spectroscopic sample of galaxies through cross-correlation with HI intensity mapping measurements. We show that the HI-galaxy cross-power spectrum contains an additive shot noise term which scales with the average HI brightness temperature of the optically-selected galaxies, allowing constraints to be placed on the average HI mass per galaxy. This approach can estimate the HI content of populations too faint to directly observe through their 21cm emission over a wide range of redshifts. This cross-correlation, as a function of optical luminosity or colour, can be used to derive HI-scaling relations. We demonstrate that this signal will be detectable by cross-correlating upcoming Australian SKA Pathfinder (ASKAP) observations with existing optically-selected samples. We also use semi-analytic simulations to verify that the HI mass can be successfully recovered by our technique in the range M_HI > 10^8 M_solar, in a manner independent of the underlying power spectrum shape. We conclude that this method is a powerful tool to study galaxy evolution, which only requires a single intensity mapping dataset to infer complementary HI gas information from existing optical and infra-red observations.Comment: 8 pages, 4 figures, submitted to MNRA

Intensity mapping cross-correlations II: HI halo models including shot noise

HI intensity mapping data traces the large-scale structure matter distribution using the integrated emission of neutral hydrogen gas (HI). The cross-correlation of the intensity maps with optical galaxy surveys can mitigate foreground and systematic effects, but has been shown to significantly depend on galaxy evolution parameters of the HI and the optical sample. Previously, we have shown that the shot noise of the cross-correlation scales with the HI content of the optical samples, such that the shot noise estimation infers the average HI masses of these samples. In this article, we present an adaptive framework for the cross-correlation of HI intensity maps with galaxy samples using our implementation of the halo model formalism (Murray et al 2018, in prep) which utilises the halo occupation distribution of galaxies to predict their power spectra. We compare two HI population models, tracing the spatial halo and the galaxy distribution respectively, and present their auto- and cross-power spectra with an associated galaxy sample. We find that the choice of the HI model and the distribution of the HI within the galaxy sample have minor significance for the shape of the auto- and cross-correlations, but highly impact the measured shot noise amplitude of the estimators, a finding we confirm with simulations. We demonstrate parameter estimation of the HI halo occupation models and advocate this framework for the interpretation of future experimental data, with the prospect of determining the HI masses of optical galaxy samples via the cross-correlation shot noise.Comment: 15 pages, 8 figures, 3 tables. Comments welcom

A λ = 1.3 Millimeter Aperture Synthesis Molecular Line Survey of Orion Kleinmann-Low

We present a 1".3 spatial resolution interferometric spectral line survey of the core of the Orion molecular cloud, obtained with the OVRO millimeter array. Covering 4 GHz bandwidth in total, the survey contains ~100 emission lines from 18 chemical species. The spatial distributions of a number of molecules point to source I near the IRc2 complex as the dominant energy source in the region but do not rule out the presence of additional lower luminosity objects. At arcsecond resolution, the offsets between dust emission and various molecular tracers suggest that the spectacular "hot core" emission in the Orion core arises via the heating and ablation of material from the surfaces of very high density clumps located ≳500 AU from source I and traced by the dust emission. We find no evidence for a strong internal heating source within the hot core condensation(s)

Clathrate type 2 hydrate formation in vacuo under astrophysical conditions

The properties of clathrate hydrates were used to explain the complex and poorly understood physical processes taking place within cometary nuclei and other icy solar system bodies. Most of all the experiments previously conducted used starting compositions which would yield clathrate types I hydrates. The main criterion for type I vs. type II clathrate hydrate formation is the size of the guest molecule. The stoichiometry of the two structure types is also quite different. In addition, the larger molecules which would form type II clathrate hydrates typically have lower vapor pressures. The result of these considerations is that at temperatures where we identified clathrate formation (120-130 K), it is more likely that type II clathrate hydrates will form. We also formed clathrate II hydrates of methanol by direct vapor deposition in the temperature range 125-135 K

Low-pressure clathrate-hydrate formation in amorphous astrophysical ice analogs

In modeling cometary ice, the properties of clathrate hydrates were used to explain anomalous gas release at large radial distances from the Sun, and the retention of particular gas inventories at elevated temperatures. Clathrates may also have been important early in solar system history. However, there has never been a reasonable mechanism proposed for clathrate formation under the low pressures typical of these environments. For the first time, it was shown that clathrate hydrates can be formed by warming and annealing amorphous mixed molecular ices at low pressures. The complex microstructures which occur as a result of clathrate formation from the solid state may provide an explanation for a variety of unexplained phenomena. The vacuum and imaging systems of an Hitachi H-500H Analytical Electron Microscope was modified to study mixed molecular ices at temperatures between 12 and 373 K. The resulting ices are characterized by low-electron dose Transmission Electron Microscopy (TEM) and Selected Area Electron Diffraction (SAED). The implications of these results for the mechanical and gas release properties of comets are discussed. Laboratory IR data from similar ices are presented which suggest the possibility of remotely observing and identifying clathrates in astrophysical objects

Parent psychological adjustment, donor conception and disclosure: a follow-up over 10 years.

STUDY QUESTION: What is the relationship between parent psychological adjustment, type of gamete donation (donor insemination, egg donation) and parents' disclosure of their use of donated gametes to their children. SUMMARY ANSWER: Disclosure of donor origins to the child was not always associated with optimal levels of psychological adjustment, especially for fathers in donor insemination families. WHAT IS KNOWN ALREADY: Cross-sectional analyses have found mothers and fathers who conceived a child using donated sperm or eggs to be psychologically well-adjusted, with few differences emerging between parents in gamete donation families and parents in families in which parents conceived naturally. The relationship between mothers' and fathers' psychological well-being, type of gamete donation (donor insemination, egg donation) and parents' disclosure decisions has not yet been examined. STUDY DESIGN, SIZE, DURATION: In this follow-up study, data were obtained from mothers and fathers in donor insemination and egg donation families at 5 time points; when the children in the families were aged 1, 2, 3, 7 and 10. In the first phase of the study, 50 donor insemination families and 51 egg donation families with a 1-year-old child participated. By age 10, the study included 34 families with a child conceived by donor insemination and 30 families with a child conceived by egg donation, representing 68 and 58% of the original sample, respectively. PARTICIPANTS/MATERIALS, SETTING, METHODS: Families were recruited through nine fertility clinics in the UK. Standardized questionnaires assessing depression, stress and anxiety were administered to mothers and fathers in donor insemination and egg donation families. MAIN RESULTS AND THE ROLE OF CHANCE: Mothers and fathers in both donor insemination and egg donation families were found to be psychologically well-adjusted; for the vast majority of parents' levels of depression, anxiety and parenting stress were found to be within the normal range at all 5 time points. Disclosure of the child's donor origins to the child was not always associated with optimal levels of parental psychological adjustment. For example, disclosure was associated with lower levels of psychological well-being for certain groups in particular (such as fathers in donor insemination families), at certain times (when children are in middle childhood and have a more sophisticated understanding of their donor origins). LIMITATIONS, REASONS FOR CAUTION: Owing to small sample sizes, the value of this study lies not in its generalizability, but in its potential to point future research in new directions. WIDER IMPLICATIONS OF THE FINDINGS: Donor insemination and egg donation families are a heterogeneous group, and future research should endeavour to obtain data from fathers as well as mothers. Support and guidance in terms of disclosure and family functioning might be most beneficial for parents (and especially fathers) in donor insemination families, particularly as the child grows older. The more that is known about the process of disclosure over time, from the perspective of the different members of the family, the better supported parents and their children can be.The first three phases of this study were supported by funding from the Wellcome Trust. The final two phases of this study were supported by grant number RO1HD051621 from the National Institute of Child Health and Human Developmen