The Dawes Review 8: Measuring the Stellar Initial Mass Function

The birth of stars and the formation of galaxies are cornerstones of modern astrophysics. While much is known about how galaxies globally and their stars individually form and evolve, one fundamental property that affects both remains elusive. This is problematic because this key property, the birth mass distribution of stars, referred to as the stellar initial mass function (IMF), is a key tracer of the physics of star formation that underpins almost all of the unknowns in galaxy and stellar evolution. It is perhaps the greatest source of systematic uncertainty in star and galaxy evolution. The past decade has seen a growing number and variety of methods for measuring or inferring the shape of the IMF, along with progressively more detailed simulations, paralleled by refinements in the way the concept of the IMF is applied or conceptualised on different physical scales. This range of approaches and evolving definitions of the quantity being measured has in turn led to conflicting conclusions regarding whether or not the IMF is universal. Here I review and compare the growing wealth of approaches to our understanding of this fundamental property that defines so much of astrophysics. I summarise the observational measurements from stellar analyses, extragalactic studies and cosmic constraints, and highlight the importance of considering potential IMF variations, reinforcing the need for measurements to quantify their scope and uncertainties carefully, in order for this field to progress. I present a new framework to aid the discussion of the IMF and promote clarity in the further development of this fundamental field.Comment: Accepted for publication in PASA. 52 pages, 10 figures. A bug in pasa-mnras.bst causes references beginning with lower-case letters (e.g., "de", "van") to be placed at the end of the reference list, rather than alphabetically. Kindly and skilled people are encouraged to correct this and share with the PASA editor

The radio spectra of reddened 2MASS QSOs: evidence for young radio jets

Multifrequency radio continuum observations (1.4-22 GHz) of a sample of reddened QSOs are presented. We find a high incidence (13/16) of radio spectral properties, such as low frequency turnovers, high frequency spectral breaks or steep power-law slopes, similar to those observed in powerful compact steep spectrum (CSS) and gigahertz-peaked spectrum (GPS) sources. The radio data are consistent with relatively young radio jets with synchotron ages <1e6-1e7yr. This calculation is limited by the lack of high resolution (milli-arcsec) radio observations. For the one source in the sample that such data are available a much younger radio age is determined, <2e3yr, similar to those of GPS/CSS sources. These findings are consistent with claims that reddened QSOs are young systems captured at the first stages of the growth of their supermassive black holes. It also suggests that expanding radio lobes may be an important feedback mode at the early stages of the evolution of AGN.Comment: 9 pages, to appear in MNRA

TQM and CSR nexus

Purpose: The aim of this paper is to explore the similarities and differences between Total Quality Management (TQM) and Corporate Social Responsibility (CSR). Moreover, the paper considers the implications of these similarities and differences for the future development of TQM and CSR. Methodological approach: Structured discourse analysis is used to systematically explore these two discursive subjects. Both concepts encompass discursive ideas and practices. Findings: Our analyses suggest that the two concepts share similar philosophical roots, that there is a substantial overlap between the elements of the two concepts, and that the ultimate expected outcomes shows significant similarities. Despite these similarities however, implementation of TQM will not necessarily result in CSR. Practical implications: Our findings lead to the conclusion that it is important to recognise the specific needs of CSR and include them as an implicit part of TQM. This conclusion has an important practical and descriptive theoretical implication and the extent to which CSR is diffused as a part of TQM depends on it. Research implications: Our analysis highlights the need for the development of a descriptive theory, that is to say, the identification of the mechanism(s) through which elements of CSR could be developed and implemented alongside that of TQM. Original/value: The question of the intersection between CSR and TQM has attracted the interest of other researchers. The majority of the previous work is normative. We contribute to this developing literature by adopting a systematic discursive approach using philosophy, elements of TQM / CSR process and outcomes as the framework for the analysis

Measurement of minority-carrier drift mobility in solar cells using a modulated electron beam

A determination of diffusivity on solar cells is here reported which utilizes a one dimensional treatment of diffusion under sinusoidal excitation. An intensity-modulated beam of a scanning electron microscope was used as a source of excitation. The beam was injected into the rear of the cell, and the modulated component of the induced terminal current was recovered phase sensitively. A Faraday cup to measure the modulated component of beam current was mounted next to the sample, and connected to the same electronics. A step up transformer and preamplifier were mounted on the sample holder. Beam currents on the order of 400-pA were used in order to minimize effects of high injection. The beam voltage was 34-kV, and the cell bias was kept at 0-V

The star formation history of damped Lyman alpha absorbers

The local power law relationship between the surface densities of neutral hydrogen gas and star formation rate (SFR) can be used to explore the SFR properties of damped Lyman alpha (DLA) systems at higher redshift. We find that while the SFR densities for DLA systems are consistent with luminous star forming galaxies at redshifts below z~0.6, at higher redshifts their SFR density is too low for them to provide a significant contribution to the cosmic star formation history (SFH). This suggests that the majority of DLAs may be a distinct population from the Lyman break galaxies (LBGs) or submillimeter star-forming galaxies that together dominate the SFR density at high redshift. It is also possible that the DLAs do not trace the bulk of the neutral gas at high redshift. The metallicity properties of DLAs are consistent with this interpretation. The DLAs show a metal mass density lower by two orders of magnitude at all redshifts than that inferred from the SFH of the universe. These results are consistent with DLAs being dominated by low mass systems having low SFRs or a late onset of star formation, similar to the star formation histories of dwarf galaxies in the local universe.Comment: 9 pages, 5 figures, accepted for publication in Ap

Narrow band cross-correlation analysis of fluctuating pressures beneath a turbulent boundary layer

Selected band cross correlation analysis of fluctuating pressures under turbulent boundary layer flo