Spectroscopy of Globular Clusters in the Sculptor Group Galaxies NGC 253 and NGC 55

We have obtained spectra for 103 published globular cluster candidates in the Sculptor Group galaxies NGC 253 and NGC 55. On the basis of radial velocities and digitized plate images, 14 globular clusters are identified in NGC 253 and one probable globular cluster is identified in NGC 55. The majority of the objects in the sample appear to be background galaxies. We have obtained and analysed COSMOS plate scans of NGC 253 and NGC 55 and use these along with the spectroscopically identified clusters to define new samples of globular cluster candidates in the two galaxies which should have reduced contamination.Comment: 11 pages, 9 postscript figures, accepted for publication in MNRA

HST Observations of Gravitationally Lensed Features in the Rich Cluster Ac114

Deep Hubble Space Telescope images of superlative resolution obtained for the distant rich cluster AC114 (z=0.31) reveal a variety of gravitational lensing phenomena for which ground-based spectroscopy is available. We present a luminous arc which is clearly resolved by HST and appears to be a lensed z=0.64 sub-L star spiral galaxy with a detected rotation curve. Of greatest interest is a remarkably symmetrical pair of compact blue images separated by 10 arcsec and lying close to the cluster cD. We propose that these images arise from a single very faint background source gravitationally lensed by the cluster core. Deep ground-based spectroscopy confirms the lensing hypothesis and suggests the source is a compact star forming system at a redshift z=1.86. Taking advantage of the resolved structure around each image and their very blue colours, we have identified a candidate third image of the same source roughly 50 arcsec away. The angular separation of the three images is much larger than previous multiply-imaged systems and indicates a deep gravitational potential in the cluster centre. Resolved multiply-imaged systems, readily recognised with HST, promise to provide unique constraints on the mass distribution in the cores of intermediate redshift clusters.Comment: submitted to ApJ, 6 pages (no figures), uuencoded Postscript, compressed TAR of Postscript figures available via anonymous ftp in users/irs/figs/ac114_figs.tar.gz on astro.caltech.edu. PAL-IRS-

Dust-lanes in elliptical and lenticular galaxies

A small proportion of elliptical and lenticular galaxies show evidence of well-defined dust-lanes when examined on deep survey plates. New near-infrared (JHK) observations of 46 dust-lane galaxies are presented and compared with those for a sample of 24 morphologigally normal systems. Infrared excesses are found preferentially in galaxies which exhibit at least weak signs of a stellar disc ; the physics of the emission mechanism is discussed in the light of additional 3.5 y observations and published optical spectra. The most extreme properties are those of the heavily obscured edge-on galaxy NGC7172. In this case, the infrared emission is variable on a timescale ^0.5 yrs. New optical spectra are also discussed and support the identification of the hard X-ray source H2158-321 with this galaxy.A restricted sample of 'elliptical-like' galaxies with dust-lanes, but containing no significant luminous disc, has been defined. It is demonstrated that these galaxies cannot be distinguished from a comparable sample of morphologically normal ellipticals on the basis of UBV colours or luminosity. Four examples have been selected for a detailed study of their structure and dynamics. Rotation curves and velocity dispersion profiles have been derived from long-slit spectra using Fourier analysis techniques ; surface photometry was obtained from large-scale photographic plates. The data reduction and analysis techniques are discussed in some detail. In three cases the angular momentum axis of the dust-lane is different from that of the stellar component, favouring an external origin for the dust and gas. Two of the galaxies rotate as rapidly as oblate models with isotropic velocity dispersions ; this property is characteristic. of the luminous bulges in disc systems. The orientation of the dust-lane favours a prolate geometry for one of these bulges. It is demonstrated that the kinematics are inconsistent with two recently published models of prolate.galaxies

Thermal comfort analysis for the first Passivhaus in Qatar

The Passivhaus standard is a well-established energy efficient standard, initially developed for central European countries, where heating is the dominant building requirement. The success of the Passivhaus standard has attracted the attention of architects and engineers around the world, including Qatar. Qatar has recently announced the first Passivhaus project in the MENA region. The project is experimental in nature - two villas have been constructed side-by-side, one according to the Passivhaus standard and the other according to conventional construction practices in the country. The objective of the study is to test the environmental performance of the Passivhaus standard in a hot and arid climate. The performance of the two villas has been analysed using the IES-VE building performance simulation tool, with the focus on the thermal comfort of the indoor environment. The indoor temperature and relative humidity were the main indicators of occupant comfort levels. Annual hourly data were analysed and, in addition, a detailed analysis of the occupied spaces in both villas on the typically hottest and coldest days of the year was undertaken. The findings indicated a consistent and more uniform level of comfort in the Passivhaus model compared to the standard base model; additionally, the cooling energy requirements to achieve comfort in the Passivhaus villa could frequently be met by the villa’s own on-site renewable energy system. Initial findings suggest that the Passivhaus standard is potentially viable in a hot and arid climate

Engaging with maths online - teaching mathematics collaboratively and inclusively through a pandemic and beyond

This case study details several concrete approaches to integrating the use of student-loaned iPads in the teaching of mathematics in Higher Education. Although there is a scarcity of rigorous studies into the efficacy of tablet devices for improved educational outcomes, previous case studies have argued that tablet devices, if used, should be integrated into the whole learning experience. The mathematics teaching team at Middlesex University have developed an inclusive digital pedagogy over the last five years that enabled us to effectively respond to the remote teaching imposed by the Covid-19 pandemic by loaning iPads to all students on specialist mathematics programmes. As we begin the return to campus we continue to integrate these devices into our teaching to address the observed “digital divide” in Generation-Z students which is characterised not by access to smart devices but by the digital skills to use them as effective learning tools. This is particularly relevant at Middlesex University which is disproportionately affected by digital poverty amongst its student population. We discuss the use of virtual whiteboard apps, the necessity of handwritten mathematics, the rich integration of multimedia content, persistent collaborative “problem solving spaces”, and how a common hardware platform allows for varied and equitable inclusive assessment. We also report the results of students’ surveys of iPad use during the remote-only 2020-21 academic year

Improving Design Characteristic to Estimate Load for Future Rock Climbing Studies

Rock climbing is an increasingly popular physical activity with indoor competition climbing accepted for inclusion at the summer 2020 Olympic Games in Tokyo. The International Olympic Committee consensus statement recommends the accurate monitoring of training load to reduce injury risk in athletes (Soligard, et al., 2016). Differences in acute/chronic training loads have been found to be predictive of injury occurrence (Gabbett, 2016). In published climbing literature to date, differences in injury terminology, data collection procedures, calculation of exposure and operational measures of performance used by authorship teams impedes comparison. At present, there is no consensus on design characteristics for use in epidemiological cohort studies in rock climbing. The aim of this article is to report a critical appraisal of methodologies used to estimate load and recommends an amendment to the IRCRA comparative grading scale to include British adjectival grade and design characteristics for future studies

Detecting the Gravitational Redshift of Cluster Gas

We examine the gravitational redshift of radiation emitted from within the potential of a cluster. Spectral lines from the intracluster medium (ICM) are redshifted in proportion to the emission-weighted mean potential along the line of sight, amounting to approximately 50 km/s at a radius of 100 kpc/h, for a cluster dispersion of 1200 km/s. We show that the relative redshifts of different ionization states of metals in the ICM provide a unique probe of the three-dimensional matter distribution. An examination of the reported peculiar velocities of cD galaxies in well studied Abell clusters reveals they are typically redshifted by an average of $\sim +200$ km/s. This can be achieved by gravity with the addition of a steep central potential associated with the cD galaxy. Note that in general gravitational redshifts cause a small overestimate of the recessional velocities of clusters by an average of $\sim$ 20 km/s.Comment: 6 pages, 3 figures, accepted to the Astrophysical Journal Letter

Evidence of a Metal Rich Galactic Bar from the Vertex Deviation of the Velocity Ellipsoid

We combine radial velocities, proper motions, and low resolution abundances for a sample of 315 K and M giants in the Baade's Window (l,b)=(0.9,-4) Galactic bulge field. The velocity ellipsoid of stars with [Fe/H]>-0.5 dex shows a vertex deviation in the plot of radial versus transverse velocity, consistent with that expected from a population with orbits supporting a bar. We demonstrate that the significance of this vertex deviation using non-parametric rank correlation statistic is >99%. The velocity ellipsoid for the metal poor ([FeH]<-0.5) part of the population shows no vertex deviation and is consistent with an isotropic, oblate rotating population. We find no evidence for kinematic subgroups, but there is a mild tendency for the vertical velocity dispersion sigma_b to decrease with increasing metallicity.Comment: 4 pages, ApJ Letters, submitte