Cosmic Microwave Background constraint on residual annihilations of relic particles

Energy injected into the Cosmic Microwave Background at redshifts z<10^6 will distort its spectrum permanently. In this paper we discuss the distortion caused by annihilations of relic particles. We use the observational bounds on deviations from a Planck spectrum to constrain a combination of annihilation cross section, mass, and abundance. For particles with (s-wave) annihilation cross section, =\sigma_0, the bound is f[(\sigma_0/6e-27cm^3/s)(\Omega_{X\bar{X}}h^2)^2]/(m_X/MeV)<0.2, where m_X is the particle mass, \Omega_{X\bar{X}} is the fraction of the critical density the particle and its antiparticle contribute if they survive to the present time, h=H_0/(100km/s/Mpc), H_0 is the Hubble constant, and f is the fraction of the annihilation energy that interacts electromagnetically. We also compute the less stringent limits for p-wave annihilation. We update other bounds on residual annihilations and compare them to our CMB bound.Comment: submitted to Phys. Rev.

Toward an internally consistent astronomical distance scale

Accurate astronomical distance determination is crucial for all fields in astrophysics, from Galactic to cosmological scales. Despite, or perhaps because of, significant efforts to determine accurate distances, using a wide range of methods, tracers, and techniques, an internally consistent astronomical distance framework has not yet been established. We review current efforts to homogenize the Local Group's distance framework, with particular emphasis on the potential of RR Lyrae stars as distance indicators, and attempt to extend this in an internally consistent manner to cosmological distances. Calibration based on Type Ia supernovae and distance determinations based on gravitational lensing represent particularly promising approaches. We provide a positive outlook to improvements to the status quo expected from future surveys, missions, and facilities. Astronomical distance determination has clearly reached maturity and near-consistency.Comment: Review article, 59 pages (4 figures); Space Science Reviews, in press (chapter 8 of a special collection resulting from the May 2016 ISSI-BJ workshop on Astronomical Distance Determination in the Space Age

WALLABY - an SKA Pathfinder Hi survey

The Widefield ASKAP L-band Legacy All-sky Blind surveY (WALLABY) is a next-generation survey of neutral hydrogen (H I) in the Local Universe. It uses the widefield, high-resolution capability of the Australian Square Kilometer Array Pathfinder (ASKAP), a radio interferometer consisting of 36×12-m dishes equipped with Phased-Array Feeds (PAFs), located in an extremely radio-quiet zone in Western Australia. WALLABY aims to survey three-quarters of the sky (−90∘<δ<+30∘) to a redshift of z≲0.26, and generate spectral line image cubes at ∼30 arcsec resolution and ∼1.6 mJy beam−1 per 4 km s−1 channel sensitivity. ASKAP’s instantaneous field of view at 1.4 GHz, delivered by the PAF’s 36 beams, is about 30 sq deg. At an integrated signal-to-noise ratio of five, WALLABY is expected to detect around half a million galaxies with a mean redshift of z∼0.05 (∼200 Mpc). The scientific goals of WALLABY include: (a) a census of gas-rich galaxies in the vicinity of the Local Group; (b) a study of the H I properties of galaxies, groups and clusters, in particular the influence of the environment on galaxy evolution; and (c) the refinement of cosmological parameters using the spatial and redshift distribution of low-bias gas-rich galaxies. For context we provide an overview of recent and planned large-scale H I surveys. Combined with existing and new multi-wavelength sky surveys, WALLABY will enable an exciting new generation of panchromatic studies of the Local Universe. — First results from the WALLABY pilot survey are revealed, with initial data products publicly available in the CSIRO ASKAP Science Data Archive (CASDA)

Zastosowanie monitoringu wysokiej czestotliwosci do okreslenia strat w wyniku parowania z terenu lak wilgotnych [Oxfordshire, Wielka Brytania]

A strong diurnal regime in water levels (maximum range 10 cm) was discovered by pressure transducers programmed to measure water levels at high frequency. The wetland site is a restored wet grassland floodplain in a clay basin. These water table fluctuations are used to estimate evaporative loss from the soil profile assuming constant head recovery, and compared to actual evaporation measurements derived from eddy correlation-energy budget methods. The former performed well on dry days with a strong diurnal regime, and information gained from high temporal resolution monitoring improved hydrological understanding of the wetland considerably.Wyraźny dzienny reżim zmian położenia zwierciadła wody (maksymalna rozpiętość zmian 10 cm) został zaobserwowany przy pomocy przetworników ciśnieniowych zaprogramowanych do pomiaru zmian położenia zwierciadła wody z wysoką częstotliwością. Monitoring tych zmian położenia zwierciadła wody prowadzony był na obszarze zrekultywowanych mokradeł o charakterze wilgotnych łąk znajdującym się na równinie zalewowej w zlewni o podłożu gliniastym. Zaobserwowane wielkości zmian położenia zwierciadła wody zostały wykorzystane do określenia wielkości strat w wyniku parowania z profilu glebowego, przy założeniu stałej wielkości zasilania poziomu wód gruntowych w wodę, oraz do porównania z wielkościami parowania rzeczywistego obliczonymi na podstawie bilansu cieplnego metodą korelacji pulsacji. Zastosowana metoda dała poprawne wyniki, szczególnie w przypadku dni bez opadu z wyraźnym dziennym reżimem zmian położenia zwierciadła wody, a zebrane w wyniku zastosowania monitoringu wysokiej częstotliwości obserwacje oraz otrzymane dane przyczyniły się znacząco do zrozumienia hydrologicznego funkcjonowania analizowanego obszaru mokradłowego