Stellar Population Effects on the Inferred Photon Density at Reionization

The relationship between stellar populations and the ionizing flux with which they irradiate their surroundings has profound implications for the evolution of the intergalactic medium. We quantify the ionizing flux arising from synthetic stellar populations which incorporate the evolution of interacting binary stars. We determine that these show ionizing flux boosted by 60 per cent at 0.05 < Z < 0.3 Z_sun and a more modest 10-20 per cent at near-Solar metallicities relative to star-forming populations in which stars evolve in isolation. The relation of ionizing flux to observables such as 1500A continuum and ultraviolet spectral slope is sensitive to attributes of the stellar population including age, star formation history and initial mass function. For a galaxy forming 1 M_sun yr^{-1}, observed at > 100 Myr after the onset of star formation, we predict a production rate of photons capable of ionizing hydrogen, N_ion = 1.4 x 10^{53} s^{-1} at Z = Z_sun and 3.5 x 10^{53} s^{-1} at 0.1 Z_sun, assuming a Salpeter-like initial mass function. We evaluate the impact of these issues on the ionization of the intergalactic medium, finding that the known galaxy populations can maintain the ionization state of the Universe back to z ~ 9, assuming that their luminosity functions continue to M_UV = -10, and that constraints on the intergalactic medium at z ~ 2 - 5 can be satisfied with modest Lyman continuum photon escape fractions of 4 - 24 per cent depending on assumed metallicity.Comment: 17 pages, accepted by MNRAS. BPASS models can be found at http://bpass.auckland.ac.nz

Evaluating the impact of binary parameter uncertainty on stellar population properties

Binary stars have been shown to have a substantial impact on the integrated light of stellar populations, particularly at low metallicity and early ages - conditions prevalent in the distant Universe. But the fraction of stars in stellar multiples as a function of mass, their likely initial periods and distribution of mass ratios are all known empirically from observations only in the local Universe. Each has associated uncertainties. We explore the impact of these uncertainties in binary parameters on the properties of integrated stellar populations, considering which properties and timescales are most susceptible to uncertainty introduced by binary fractions and whether observations of the integrated light might be sufficient to determine binary parameters. We conclude that the effects of uncertainty in the empirical binary parameter distributions are likely smaller than those introduced by metallicity and stellar population age uncertainties for observational data. We identify emission in the He II 1640Å emission line and continuum colour in the ultraviolet-optical as potential indicators of a high mass binary presence, although poorly constrained metallicity, dust extinction and degeneracies in plausible star formation history are likely to swamp any measurable signal

Stratospheric measurement requirements and satellite-borne remote sensing capabilities

The capabilities of specific NASA remote sensing systems to provide appropriate measurements of stratospheric parameters for potential user needs were assessed. This was used to evaluate the capabilities of the remote sensing systems to perform global monitoring of the stratosphere. The following conclusions were reached: (1) The performance of current remote stratospheric sensors, in some cases, compares quite well with identified measurement requirements. Their ability to measure other species has not been demonstrated. (2) None of the current, in-situ methods have the capability to satisfy the requirements for global monitoring and the temporal constraints derived from the users needs portion of the study. (3) Existing, non-remote techniques will continue to play an important role in stratospheric investigations for both corroboration of remotely collected data and in the evolutionary development of future remote sensors

Exploring the impact of IMF and binary parameter stochasticity with a binary population synthesis code

Low mass star formation regions are unlikely to fully populate their initial mass functions, leading to a deficit of massive stars. In binary stellar populations, the full range of binary separations and mass ratios will also be underpopulated. To explore the effects of stochastic sampling in the integrated light of stellar clusters, we calculate models at a broad range of cluster masses, from 10^2 to 10^7 M_sun, using a binary stellar population synthesis code. For clusters with stellar masses less than 10^5 M_sun, observable quantities show substantial scatter and their mean properties reflect the expected deficit of massive stars. In common with previous work, we find that purely stochastic sampling of the initial mass function appears to underestimate the mass of the most massive star in known clusters. However, even with this constraint, the majority of clusters likely inject sufficient kinetic energy to clear their birth clusters of gas. For quantities which directly measure the impact of the most massive stars, such as N_{ion}, xi_{ion} and beta_{UV}, uncertainties due to stochastic sampling dominate over those from the IMF shape or distribution of binary parameters, while stochastic sampling has a negligible effect on the stellar continuum luminosity density.Comment: 15 pages and 8 page appendix. Accepted for publication in MNRA

Far-infrared properties of trimethylammonium iodide tetracyanoquinodimethane

Journal ArticleWe present the powder absorption spectrum of (TMA) (I)(TCNQ) in the far-infrared as a function of temperature. Below 16 K new absorption features appear and others increase in intensity. This behaviour supports the electron and neutron diffraction evidence of a distortion on the TCNQ chains below the first phase transition temperature of 159 K (in the deuterated sample

Far-infrared powder spectrum of (N(CH3)3D)(I)(TCNQ)

Journal ArticleWe present the powder absorption spectrum of (TMA)(I)(TCNQ) in the far-infrared as a function of temperature. Below 160 K new absorption features appear and others increase in intensity. This behaviour supports the electron- neutron-diffraction evidence of a distortion on the TCNQ chains below the first phase-transition temperature. Effects due to the second phase transition at 89 K are also observed. The results of a group-theoretical analysis are presented. These show that totally-symmetric internal modes ag are to be expected in the infrared spectra of this compound even in the undistorted phase

Tourism, nightlife and planning: challenges and opportunities for community liveability in La Barceloneta

In La Barceloneta, one of the beachfront quarters of the city of Barcelona, the rapid expansion of mainly illegal short-term rental apartments for tourists and noise problems related to alcohol-fuelled nightlife consumption, are challenging community liveability and peaceful urban coexistence between different social groups. Similar to other cases worldwide, the rapid expansion of touristification on the urban and socio-economic fabric of the city has become an increasing source of dispute and residents' contestation. By taking a diachronical critical review, the first part of this paper examines the role of urban planning developed in La Barceloneta during the period 1950–2016 and how it transformed the area into a leisure-oriented and tourist-oriented quarter. The second part of the paper is based on two years of ethnographic fieldwork that was conducted to capture the range of different voices, stories and discourses produced and reproduced by different actors affected and/or involved in the recent touristification of La Barceloneta. Findings obtained confirm that current urban policy and planning are clearly insufficient to tackle and address negative community-based impacts aforementioned. Hence, the final section highlights the urgent need for the development and implementation of new, community-based urban planning with the aim of ensuring community liveability and peaceful urban coexistence between different social groups in La Barceloneta

Conceptual design studies of candidate V/STOL lift fan commercial short haul transport for 1980 - 1985 V/STOL lift fan study

Conceptual designs of V/STOL lift fan commercial short haul transport aircraft for the 1980-85 time period were studied to determine their technical and economic feasibility. The engine concepts included both integral and remote fans. The scope of the study included definition of the hover control concept for each propulsion system, aircraft design, aircraft mass properties, cruise performance, noise and ride qualities evaluation. Economic evaluating was also studied on a basis of direct operating costs and route structure