The Black Hole Mass - Spheroid Luminosity relation

The differing M_bh-Luminosity relations presented in McLure & Dunlop, Marconi & Hunt and Erwin et al. have been investigated. A number of issues have been identified and addressed in each of these studies, including but not limited to: the removal of a dependency on the Hubble constant; a correction for dust attenuation in the bulges of disc galaxies; the identification of lenticular galaxies previously treated as elliptical galaxies; and application of the same (Y|X) regression analysis. These adjustments result in relations which now predict similar black hole masses. The optimal K-band relation is log(M_bh/M_sun) = -0.37(+/-0.04)[M_K +24] + 8.29(+/-0.08), with a total (not intrinsic) scatter in log M_bh equal to 0.33 dex. This level of scatter is similar to the value of 0.34 dex from the M_bh-sigma relation of Tremaine et al. and compares favourably with the value of 0.31 dex from the M_bh-n relation of Graham & Driver. Using different photometric data, consistent relations in the B- and R-band are also provided, although we do note that the small (N=13) R-band sample used by Erwin et al. is found here to have a slope of -0.30(+/-0.06) and a total scatter of 0.31 dex. Performing a symmetrical regression on the larger K-band sample gives a slope of -0.40, implying M_bh ~ L^{1.00}. Implications for galaxy-black hole coevolution, in terms of dry mergers, are briefly discussed, as are predictions for intermediate mass black holes. Finally, as previously noted by Tundo et al., a potential bias in the galaxy sample used to define the M_bh-L relations is shown and a corrective formula provided.Comment: 12 pages, to appaer in MNRA

Active engagement with assessment and feedback can improve group-work outcomes and boost student confidence

This study involves evaluation of a novel iterative group-based learning task developed to enable students to actively engage with assessment and feedback in order to improve the quality of their written work. The students were all in the final semester of their final year of study and enrolled on either BSc Zoology or BSc Marine and Freshwater Biology at a mainstream UK university, but the findings of this research can be generalised to a wider student body. The main findings are that in a group work context, individual students can use provided assessment criteria to accurately assess the work produced by their group and that their ability to produce and recognise work of a higher quality improves as a result of a social dialogue around self/peer assessment and self/tutor generated feedback. The study also reveals that producing poorer work over-assess and those achieving the highest marks under-assess. Over-assessing students focus to a greater extent upon the superficial deficiencies in their work, whereas under assessing students are more likely to focus on more significant issues. High-achieving under-assessing students lack confidence in their own abilities, but believe feedback provides a confidence boost

Comment on "A Non-Parametric Estimate of Mass 'Scoured' in Galaxy Cores" (arXiv:1006.0488)

This comment is in response to the article titled "A Non-Parametric Estimate of Mass Scoured in Galaxy Cores" (arXiv:1006.0488) written by Hopkins and Hernquist. This comment politely mentions two relevant papers in which the main conclusion from Hopkins & Hernquist had already been published six years ago using the core-Sersic model. It then explains why Hopkins & Hernquist's concern about the core-Sersic model is not valid.Comment: 1 page of text, plus reference

Theoretical study of refraction effects on noise produced by turbulent jets

The transmission of acoustic disturbances from the interior of a jet into the ambient air is studied. The jet is assumed infinitely long with mean velocity profile independent of streamwise location. The noise generator is a sequence of transient sources drifting with the local fluid and confined to a short length of the jet. In Part 1, supersonic jets are considered. Numerical results for mean-square pressure versus angle in the far-field show unexpected peaks which are very sharp. Analysis of simplified models indicates that these are complex quasi-resonant effects which appear to the stationary observer in a high frequency range. The peaks are real for the idealized model, but would be smoothed by mathematical integration over source position, velocity, and frequency. Subsonic jets were considered in part 2, and a preliminary study of the near-field was attempted. Mean-square radial displacements (or mean radial energy flow or space-time correlations of radial pressure gradient) are first found for very simple cases. The most difficult case studied is a sequence of transient sources at the center of a uniform-velocity circular cylindrical jet. Here a numerical triple integration is required and seems feasible although only preliminary results for mean square radial displacement are now available. These preliminary results show disturbances decreasing with increasing radial distance, and with increasing distance upstream and downstream from the source. A trend towards greater downstream disturbances appears even in the near field