The Globular Cluster System of NGC 5128: Ages, Metallicities, Kinematics, and Structural Parameters

Abstract: We review our recent studies of the globular cluster system of NGC 5128. First, we have obtained low-resolution, high signal-to-noise spectroscopy of 72 globular clusters using Gemini-S/GMOS to obtain the ages, metallicities, and the level of alpha enrichment of the metal-poor and metal-rich globular cluster subpopulations. Second, we have explored the rotational signature and velocity dispersion of the galaxy’s halo using over 560 globular clusters with radial velocity measurements. We have also compared the dependence of these properties on galactocentric distance and globular cluster age and metallicity. Using globular clusters as tracer objects, we have analyzed the mass, and M/L ratio of NGC 5128. Last, we have measured the structural parameters, such as half-light radii, of over 570 globular clusters from a superb 1.2 square degree Magellan/IMACS image. We will present the findings of these studies and discuss the connection to the formation and evolution of NGC 512

Sizes of Confirmed Globular Clusters in NGC 5128: A Wide-Field High-Resolution Study

Using Magellan/IMACS images covering a 1.2 x 1.2 sq. degree FOV with seeing of 0.4"-0.6", we have applied convolution techniques to analyse the light distribution of 364 confirmed globular cluster in the field of NGC 5128 and to obtain their structural parameters. Combining these parameters with existing Washington photometry from Harris et al. (2004), we are able to examine the size difference between metal-poor (blue) and metal-rich (red) globular clusters. For the first time, this can be addressed on a sample of confirmed clusters that extends to galactocentric distances about 8 times the effective radius, R$_{eff}$, of the galaxy. Within 1 R$_{eff}$, red clusters are about 30% smaller on average than blue clusters, in agreement with the vast majority of extragalactic globular cluster systems studied. As the galactocentric distance increases, however, this difference becomes negligible. Thus, our results indicate that the difference in the clusters' effective radii, r$_e$, could be explained purely by projection effects, with red clusters being more centrally concentrated than blue ones and an intrinsic r$_e$--R$_{gc}$ dependence, like the one observed for the Galaxy.Comment: 4 figures, accepted for publication in ApJ

The Centaurus Group and the Outer Halo of NGC 5128: Are they Dynamically Connected?

NGC 5128, a giant elliptical galaxy only $\sim 4$ Mpc away, is the dominant member of a galaxy group of over 80 probable members. The Centaurus group provides an excellent sample for a kinematic comparison between the halo of NGC 5128 and its surrounding satellite galaxies. A new study, presented here, shows no kinematic difference in rotation amplitude, rotation axis, and velocity dispersion between the halo of NGC 5128, determined from over $\sim340$ of its globular clusters, and those of the Centaurus group as a whole. These results suggest NGC 5128 could be behaving in part as the inner component to the galaxy group, and could have begun as a large initial seed galaxy, gradually built up by minor mergers and satellite accretions, consistent with simple cold dark matter models. The mass and mass-to-light ratios in the B-band, corrected for projection effects, are determined to be $(1.3\pm0.5) \times 10^{12}$ M_{\sun} and $52\pm22$ M_{\sun}/L_{\sun} for NGC 5128 out to a galactocentric radius of 45 kpc, and $(9.2\pm3.0) \times 10^{12}$ M_{\sun} and $153\pm50$ M_{\sun}/L_{\sun} for the Centaurus group, consistent with previous studies.Comment: 14 pages, 3 tables, 7 figures, Accepted for publication in A

Studying the effect of industrial operating conditions on enzyme kinetics and stability

Please click Additional Files below to see the full abstrac

Tuning Knobs for the NLC Final Focus

Compensation of optics errors at the Interaction Point (IP) is essential for maintaining maximum luminosity at the NLC. Several correction systems (knobs) using the Final Focus sextupoles have been designed to provide orthogonal compensation of linear and the second order optics aberrations at IP. Tuning effects of these knobs on the 250 GeV beam were verified using tracking simulations.Comment: 4 pages, 3 figure

Womanism and Snowball Sampling: Engaging Marginalized Populations in Holistic Research

Womanist and feminist qualitative researchers continue to identify research methods and techniques that harness the power of social networking and personal connections while engaging with marginalized populations. Many have found that the use of snowball sampling allows increased access to individuals and groups that may otherwise remain inaccessible. The purpose of this article is to discuss the use of snowball sampling techniques within womanist and feminist research. The authors offer critical reflections of the use of this sampling technique as a tool that allows researchers access to “hidden” and marginalized populations. An example of the use of snowball sampling in a doctoral research project, which looks at the experiences of Black women faculty in New Mexico’s institutions of higher education, is provided. The article concludes with recommended strategies and key considerations about the use of snowball sampling in womanist research

Using protein engineering to accelerate implementation of continuous biocatalysis for API synthesis

Biocatalysis is an invaluable tool for the synthesis of many active pharmaceutical ingredients1,2. Enzymatic reactions are frequently performed in batch, but continuous biocatalysis is gaining interest in industry3, not least because it would allow better integration of chemical and enzymatic reaction steps4. However, selecting a suitable reactor configuration for continuous biocatalysis is often challenging due to the common limitations of enzymes, such as poor kinetic constants towards industrially relevant substrates, substrate/product inhibition, the need for an aqueous reaction environment and/or pH control. For this reason, we have recently developed a tool5 that presents a variety of reactor configurations, combining continuously stirred tank reactors (CSTRs) and continuous plug-flow reactors (CPFRs), to overcome the aforementioned limitations and facilitate reactor selection. However, the continued development of protein engineering technologies6,7 has revealed one of the strongest advantages of biocatalysis over chemocatalysis, namely that the properties of the catalyst can be modified to remove limitations and better suit industrial production processes.8,9 In this presentation we highlight how protein engineering, guided by process-specific targets, can streamline process development. For example, reducing product inhibition by protein engineering could allow operation in a single CPFR where the possibility of complete conversion greatly simplifies downstream processing, improving the tolerance of enzymes towards organic solvents could allow water-free operation without mass transfer limitations between phases and improving pH tolerance could remove the need for acid/base addition to combat pH changes during operation. Such changes to the catalyst could greatly facilitate process development in an industry where reduction of time-to-market is often critical. (1) Pollard, D. J.; Woodley, J. M. Trends Biotechnol. 2007, 25, 66–73. (2) Devine, P. N.; Howard, R. M.; Kumar, R.; Thompson, M. P.; Truppo, M. D.; Turner, N. J. Nat. Rev. Chem. 2018, 2, 409–421. (3) Tamborini, L.; Fernandes, P.; Paradisi, F.; Molinari, F. Trends Biotechnol. 2018, 36, 73–88. (4) Rudroff, F.; Mihovilovic, M. D.; Gröger, H.; Snajdrova, R.; Iding, H.; Bornscheuer, U. T. Nat. Catal. 2018, 1, 12–22. (5) Lindeque, R. M.; Woodley, J. M. Catalysts 2019, 9, 262. (6) Arnold, F. H. Angew. Chem. Int. Ed. 2018, 57, 4143–4148. (7) Yang, K. K.; Wu, Z.; Arnold, F. H. arXiv:1811.10775 2018. (8) Woodley, J. M. Curr. Opin. Chem. Biol. 2013, 17, 310–316. (9) Woodley, J. M. Phil. Trans. R. Soc. A 2017, 376

Understanding the effect of Air-liquid interface on enzyme stability in the presence of hydrophobins

Please click Additional Files below to see the full abstrac

Beam-Based Alignment, Tuning and Beam Dynamics Studies for the ATF2 Extraction Line and Final Focus System

MOPP039International audienceUsing a new extraction line currently under construction, the ATF2 experiment plans to test the novel compact final focus optics design with local chromaticity correction intended for use in future linear colliders. With a 1.3 GeV design beam of 30nm normalised vertical emittance extracted from the ATF damping ring, the primary goal is to achieve a vertical spot-size at the IP waist of 37nm. We discuss our planned strategy for tuning the ATF2 beam to meet the primary goal. Simulation studies have been performed to asses the effectiveness of the strategy, including “static” (installation) errors and dynamical effects (ground-motion, mechanical vibration, ring extraction jitter etc.). We have simulated all steps in the tuning procedure, from initial orbit establishment to final IP spot-size tuning. Through a Monte Carlo study of 100's of simulation seeds we find we can achieve a spot-size within ~10% of the design optics value in at least 75% of cases. We also ran a simulation to study the long-term performance with the use of beam-based feedbacks