Analysing Gas Kinematics in Star-Forming Galaxies using Disc Modelling

The work in this thesis aims to accurately determine the gas kinematics in disc galaxies and relate those inferences to their drivers. For this thesis a Bayesian disc modelling technique, known as Blobby3D, was developed to infer the gas kinematics of galaxies while limiting the effects of beam smearing. Blobby3D was applied to samples of galaxies from the SAMI Galaxy Survey, DYnamics of Newly Assembled Massive Objects (DYNAMO) survey, and the KMOS Redshift One Spectroscopic Survey (KROSS). The results of these analyses were used to gain accurate measures of the velocity dispersion and rotational velocity in galaxies from z ~ 0.1 to z ~ 1 with wide ranging galaxy properties. Using these results it was found that the gas velocity dispersion in galaxies at z ~ 0.1 slowly increases from σ ~ 17±3 km/s to σ ~ 24±5 km/s across the range log(SFR/ M/yr) in [-3, 0]. A sharper increase in velocity dispersion occurs for log(SFR/ M/yr) > 0, where the velocity dispersion increases to as high as σ ~ 80 km/s. The SFR–σ relation was found to be consistent with turbulence driven by models that incorporated both star-formation feedback processes and gravitational transport of gas through the disc. Comparisons of the results from KROSS at z ~ 1 to those from the SAMI Galaxy Survey and DYNAMO survey were used to determine the change in gas kinematics across epochs. The typical velocity dispersion at z ~ 1 was found to be consistent with galaxies from the DYNAMO survey that have similar galaxy properties. This suggests that the galaxy properties are playing a major factor in the intrinsic velocity dispersion of the galaxy. It was then shown that disc galaxies are consistent with being marginally stable from gravitational collapse. The consistency of SFR-σ with the theoretical models that include star-formation feedback and gas transport are also shown to extend to galaxies at z ~ 1. The usefulness and future applicability of using Blobby3D in future studies is then outlined in the conclusion

New families of single integration vectors and gene tagging plasmids for genetic manipulations in budding yeast.

The tractability of the budding yeast genome has provided many insights into the fundamental mechanisms regulating cellular life. With the advent of synthetic biology and single-cell measurements, novel tools are required to manipulate the yeast genome in a more controlled manner. We present, here, a new family of yeast shuttle vectors called single integration vectors (pSIV). Upon transformation in yeast, these plasmids replace the entire deficient auxotrophy marker locus by a cassette containing an exogenous marker. As shown using flow cytometry, this complete replacement results in a unique integration of the desired DNA fragment at the marker locus. In addition, a second transcriptional unit can be inserted to achieve the simultaneous integration of two constructs. The selection marker cassettes, present in the pSIV, were also used to generate a complete set of gene tagging plasmids (pGT) encompassing a large palette of fluorescent proteins, from a cyan fluorescent protein to a near-infrared tandem dimer red fluorescent protein. These tagging cassettes are orthogonal to each other thanks to the use of different TEF promoter and terminator couples, thereby avoiding marker cassette switching and favoring integration in the desired locus. In summary, we have created two sets of robust molecular tools for the precise genetic manipulation of the budding yeast

Actionneur à deux degrés de liberté pour micro robot mobile

Ce projet présente un actionneur à deux degrés de liberté (mouvement verticale et rotation) pour des micro-robots mobiles. L’actionneur possède un encombrement de 12 x 10.4 x 3 mm3 et une course de 5.5 mm. L’actionnement est basé sur le principe du stick-slip avec des actionneurs piézo-électriques avec des pieds conducteurs pour éviter des fils. L’actionneur est capable de soulever un poids de 2.5 g et présente des vitesses maximales de 0.7 mm/s en verticale et 0.18 rad/s en rotation

Clinical staging and the differential risks for clinical and functional outcomes in young people presenting for youth mental health care

Background: Clinical staging proposes that youth-onset mental disorders develop progressively, and that active treatment of earlier stages should prevent progression to more severe disorders. This retrospective cohort study examined the longitudinal relationships between clinical stages and multiple clinical and functional outcomes within the frst 12 months of care. Methods: Demographic and clinical information of 2901 young people who accessed mental health care at age 12–25 years was collected at predetermined timepoints (baseline, 3 months, 6 months, 12 months). Initial clinical stage was used to defne three fxed groups for analyses (stage 1a: ‘non-specifc anxious or depressive symptoms’, 1b: ‘attenuated mood or psychotic syndromes’, 2+: ‘full-threshold mood or psychotic syndromes’). Logistic regression models, which controlled for age and follow-up time, were used to compare clinical and functional outcomes (role and social function, suicidal ideation, alcohol and substance misuse, physical health comorbidity, circadian disturbances) between staging groups within the initial 12 months of care. Results: Of the entire cohort, 2093 young people aged 12–25 years were followed up at least once over the frst 12 months of care, with 60.4% female and a baseline mean age of 18.16 years. Longitudinally, young people at stage 2+ were more likely to develop circadian disturbances (odds ratio [OR]=2.58; CI 1.60–4.17), compared with individuals at stage 1b. Additionally, stage 1b individuals were more likely to become disengaged from education/employment (OR=2.11, CI 1.36–3.28), develop suicidal ideations (OR=1.92; CI 1.30–2.84) and circadian disturbances (OR=1.94, CI 1.31–2.86), compared to stage 1a. By contrast, we found no relationship between clinical stage and the emergence of alcohol or substance misuse and physical comorbidity. Conclusions: The diferential rates of emergence of poor clinical and functional outcomes between early versus late clinical stages support the clinical staging model’s assumptions about illness trajectories for mood and psychotic syndromes. The greater risk of progression to poor outcomes in those who present with more severe syndromes may be used to guide specifc intervention packages

X-ray emission during the muonic cascade in hydrogen

We report our investigations of X rays emitted during the muonic cascade in hydrogen employing charge coupled devices as X-ray detectors. The density dependence of the relative X-ray yields for the muonic hydrogen lines (K_alpha, K_beta, K_gamma) has been measured at densities between 0.00115 and 0.97 of liquid hydrogen density. In this density region collisional processes dominate the cascade down to low energy levels. A comparison with recent calculations is given in order to demonstrate the influence of Coulomb deexcitation.Comment: 5 pages, Tex, 4 figures, submitted to Physical Review Letter

The SAMI Galaxy Survey: Bayesian Inference for Gas Disk Kinematics using a Hierarchical Gaussian Mixture Model

We present a novel Bayesian method, referred to as Blobby3D, to infer gas kinematics that mitigates the effects of beam smearing for observations using Integral Field Spectroscopy (IFS). The method is robust for regularly rotating galaxies despite substructure in the gas distribution. Modelling the gas substructure within the disk is achieved by using a hierarchical Gaussian mixture model. To account for beam smearing effects, we construct a modelled cube that is then convolved per wavelength slice by the seeing, before calculating the likelihood function. We show that our method can model complex gas substructure including clumps and spiral arms. We also show that kinematic asymmetries can be observed after beam smearing for regularly rotating galaxies with asymmetries only introduced in the spatial distribution of the gas. We present findings for our method applied to a sample of 20 star-forming galaxies from the SAMI Galaxy Survey. We estimate the global H$\alpha$ gas velocity dispersion for our sample to be in the range $\bar{\sigma}_v \sim$[7, 30] km s$^{-1}$. The relative difference between our approach and estimates using the single Gaussian component fits per spaxel is $\Delta \bar{\sigma}_v / \bar{\sigma}_v = - 0.29 \pm 0.18$ for the H$\alpha$ flux-weighted mean velocity dispersion.Comment: 23 pages, 12 figures, accepted for MNRA

The SAMI Galaxy Survey: a statistical approach to an optimal classification of stellar kinematics in galaxy surveys

Large galaxy samples from multi-object IFS surveys now allow for a statistical analysis of the z~0 galaxy population using resolved kinematics. However, the improvement in number statistics comes at a cost, with multi-object IFS survey more severely impacted by the effect of seeing and lower S/N. We present an analysis of ~1800 galaxies from the SAMI Galaxy Survey and investigate the spread and overlap in the kinematic distributions of the spin parameter proxy $\lambda_{Re}$ as a function of stellar mass and ellipticity. For SAMI data, the distributions of galaxies identified as regular and non-regular rotators with \textsc{kinemetry} show considerable overlap in the $\lambda_{Re}$-$\varepsilon_e$ diagram. In contrast, visually classified galaxies (obvious and non-obvious rotators) are better separated in $\lambda_{Re}$ space, with less overlap of both distributions. Then, we use a Bayesian mixture model to analyse the observed $\lambda_{Re}$-$\log(M_*/M_{\odot})$ distribution. Below $\log(M_{\star}/M_{\odot})\sim10.5$, a single beta distribution is sufficient to fit the complete $\lambda_{Re}$ distribution, whereas a second beta distribution is required above $\log(M_{\star}/M_{\odot})\sim10.5$ to account for a population of low-$\lambda_{Re}$ galaxies. While the Bayesian mixture model presents the cleanest separation of the two kinematic populations, we find the unique information provided by visual classification of kinematic maps should not be disregarded in future studies. Applied to mock-observations from different cosmological simulations, the mixture model also predicts bimodal $\lambda_{Re}$ distributions, albeit with different positions of the $\lambda_{Re}$ peaks. Our analysis validates the conclusions from previous smaller IFS surveys, but also demonstrates the importance of using kinematic selection criteria that are dictated by the quality of the observed or simulated data.Comment: 30 pages and 17 figures, accepted for publication in MNRAS. Abstract abridged for Arxiv. The key figures of the paper are: 3, 7, 8, and 1