Dust and Cool Gas Content and Distribution in Early-Type Galaxies

This thesis considers the content and distribution of cool Interstellar Medium (ISM) in Early-Type Galaxies (ETGs), and how it can be used to infer the evolutionary mechanisms responsible for forming ETGs in the local Universe. High-resolution observations of molecular gas via carbon monoxide (CO) emission with the Atacama Large Millimetre /submillimetre Array (ALMA) interferometric telescope in five Dusty ETGs were analysed by fitting of kinematic models, to reveal any asymmetries or additional features. A new, clean and complete sample of galaxies was created within the Galaxy and Mass Assembly (GAMA) project equatorial regions to a redshift of 0.06, with visual morphological classifications assigned where possible. Masses and properties of cool dust for galaxies with suitable photometry in the sample were obtained by fitting a single modified blackbody (SMBB) model to sub-mm photometry from the Herschel-ATLAS project. New observations of molecular gas via CO emission for 32 Dusty ETGs from the clean and complete sample were also obtained using the IRAM 30m telescope. The results of the work indicate that for dusty ETGs in the local Universe, in low density environments such as those in the GAMA equatorial regions, interactions and minor mergers play a significant role in their formation. These events are apparent for four of the five ALMA-observed Dusty ETGs, with the fifth affected by contamination with a background object. Molecular gas-to-dust mass ratios derived from IRAM 30m Telescope observations are less scattered at stellar masses <3 _ 1010 M_, indicating less introduction of ISM as a result of disturbance to form the ETGs. At higher stellar masses, gas-to-dust mass ratios are lower and more scattered, with minor mergers appearing to be more significant. The observed Dusty ETGs are mostly star-forming, and appear to have been observed at a stage where ISM has settled, allowing star formation to recommence. The estimation of dust masses using Herschel-ATLAS photometry for lower stellar mass galaxies (_109:5 M_) appears to have been affected by lack of quantification of sub-mm excess emission, which may have led to under-estimation of dust mass. This is unavoidable without photometry at wavelengths greater than 500 _m, to constrain the longer-wavelength region of the dust emission spectrum. Nonetheless, dust masses were shown to be reduced in Dusty ETGs compared to Late-Type Galaxies (LTGs) above a stellar mass of _ 109:5 M_, while temperature and emissivity co effcient were found to be indistinguishable between Dusty ETGs and LTGs. Power-law relations from this work are shown for information between dust mass and star formation rate, and molecular gas mass and either dust mass or star formation rate, as expected if these properties in star-forming galaxies are linked. Opportunities for further work have been identified. Possible projects include further observations with ALMA and the IRAM 30m telescope, to extend the results presented. Radiative transfer modelling for Dusty ETGs is also a possibility, to investigate nonequilibrium dust temperatures as an indicator of recent acquisition of dust

Cool Interstellar Medium as an Evolutionary Tracer in ALMA-Observed Local Dusty Early-Type Galaxies

The content and distribution of cool interstellar medium (ISM, <30K) can indicate the evolutionary mechanisms that transform late-type to early-type galaxies (ETGs). To investigate this, ALMA observations of 12CO[2-1] line emission were obtained for five dusty ETGs from a complete sample in low-density environments. Four of the ETGs have massive (∼109 M⊙), extended molecular gas reservoirs with effective radii ∼3-5 kpc. This work provides a kinematic and structural analysis of these observations, to explore possible evolutionary mechanisms. Axisymmetric or bisymmetric kinematic models were fitted to observations of molecular gas discs, to quantify the dominant structures present and highlight additional structures or asymmetries. Integral Field Unit (IFU) observations of these ETGs were also examined where available. Two of the ETGs, GAMA64646 and 622305, appear to have undergone tidal disturbance leading to molecular gas discs and/or star-forming inner rings. GAMA272990 may have undergone a merger, leading to an elliptical galaxy with an embedded star-forming molecular gas disc. GAMA622429 has probably undergone a minor merger, indicated by asymmetry in molecular gas distribution and disturbance in optical images. The remaining ETG, GAMA177186, was affected by source confusion from an offset source which could be a high-mass, dust- and gas-rich object at high redshift. Overall, it appears that a high proportion of dusty ETGs in low-density environments have massive, extended molecular gas reservoirs, and have undergone some kind of interaction as part of their recent evolution. Secular evolution can then (re-)transform the ETGs from star-forming to passive galaxies

ALMA observations of massive molecular gas reservoirs in dusty early-type galaxies

Unresolved gas and dust observations show a surprising diversity in the amount of interstellar matter in early-type galaxies. Using ALMA observations we resolve the ISM in z∼0.05 early-type galaxies. From a large sample of early-type galaxies detected in the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) we selected five of the dustiest cases, with dust masses Md ∼several× 107M⊙, with the aim of mapping their submillimetre continuum and 12CO(2-1) line emission distributions. These observations reveal molecular gas disks. There is a lack of associated, extended continuum emission in these ALMA observations, most likely because it is resolved out or surface brightness limited, if the dust distribution is as extended as the CO gas. However, two galaxies have central continuum ALMA detections. An additional, slightly offset, continuum source is revealed in one case, which may have contributed to confusion in the Herschel fluxes. Serendipitous continuum detections further away in the ALMA field are found in another case. Large and massive rotating molecular gas disks are mapped in three of our targets, reaching a few× 109M⊙. One of these shows evidence of kinematic deviations from a pure rotating disc. The fields of our two remaining targets contain only smaller, weak CO sources, slightly offset from the optical galaxy centres. These may be companion galaxies seen in ALMA observations, or background objects. These heterogeneous findings in a small sample of dusty early-type galaxies reveal the need for more such high spatial resolution studies, to understand statistically how dust and gas are related in early-type galaxies

JINGLE V: Dust properties of nearby galaxies derived from hierarchical Bayesian SED fitting

We study the dust properties of 192 nearby galaxies from the JINGLE survey using photometric data in the 22-850μm range. We derive the total dust mass, temperature T and emissivity index β of the galaxies through the fitting of their spectral energy distribution (SED) using a single modified black-body model (SMBB). We apply a hierarchical Bayesian approach that reduces the known degeneracy between T and β. Applying the hierarchical approach, the strength of the T-β anti-correlation is reduced from a Pearson correlation coefficient R = -0.79 to R = -0.52. For the JINGLE galaxies we measure dust temperatures in the range 17 - 30 K and dust emissivity indices β in the range 0.6 - 2.2. We compare the SMBB model with the broken emissivity modified black-body (BMBB) and the two modified black-bodies (TMBB) models. The results derived with the SMBB and TMBB are in good agreement, thus applying the SMBB, which comes with fewer free parameters, does not penalize the measurement of the cold dust properties in the JINGLE sample. We investigate the relation between T and β and other global galaxy properties in the JINGLE and Herschel Reference Survey (HRS) sample. We find that β correlates with the stellar mass surface density (R = 0.62) and anti-correlates with the HI mass fraction (MHI/M*, R = -0.65), whereas the dust temperature correlates strongly with the SFR normalized by the dust mass (R = 0.73). These relations can be used to estimate T and β in galaxies with insufficient photometric data available to measure them directly through SED fitting

Effects of antiplatelet therapy on stroke risk by brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases: subgroup analyses of the RESTART randomised, open-label trial

Background Findings from the RESTART trial suggest that starting antiplatelet therapy might reduce the risk of recurrent symptomatic intracerebral haemorrhage compared with avoiding antiplatelet therapy. Brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases (such as cerebral microbleeds) are associated with greater risks of recurrent intracerebral haemorrhage. We did subgroup analyses of the RESTART trial to explore whether these brain imaging features modify the effects of antiplatelet therapy

Measurement of the cosmic ray spectrum above 4×10184{\times}10^{18} eV using inclined events detected with the Pierre Auger Observatory

A measurement of the cosmic-ray spectrum for energies exceeding $4{\times}10^{18}$ eV is presented, which is based on the analysis of showers with zenith angles greater than $60^{\circ}$ detected with the Pierre Auger Observatory between 1 January 2004 and 31 December 2013. The measured spectrum confirms a flux suppression at the highest energies. Above $5.3{\times}10^{18}$ eV, the "ankle", the flux can be described by a power law $E^{-\gamma}$ with index $\gamma=2.70 \pm 0.02 \,\text{(stat)} \pm 0.1\,\text{(sys)}$ followed by a smooth suppression region. For the energy ($E_\text{s}$) at which the spectral flux has fallen to one-half of its extrapolated value in the absence of suppression, we find $E_\text{s}=(5.12\pm0.25\,\text{(stat)}^{+1.0}_{-1.2}\,\text{(sys)}){\times}10^{19}$ eV.Comment: Replaced with published version. Added journal reference and DO

New genetic loci link adipose and insulin biology to body fat distribution.

Body fat distribution is a heritable trait and a well-established predictor of adverse metabolic outcomes, independent of overall adiposity. To increase our understanding of the genetic basis of body fat distribution and its molecular links to cardiometabolic traits, here we conduct genome-wide association meta-analyses of traits related to waist and hip circumferences in up to 224,459 individuals. We identify 49 loci (33 new) associated with waist-to-hip ratio adjusted for body mass index (BMI), and an additional 19 loci newly associated with related waist and hip circumference measures (P < 5 × 10(-8)). In total, 20 of the 49 waist-to-hip ratio adjusted for BMI loci show significant sexual dimorphism, 19 of which display a stronger effect in women. The identified loci were enriched for genes expressed in adipose tissue and for putative regulatory elements in adipocytes. Pathway analyses implicated adipogenesis, angiogenesis, transcriptional regulation and insulin resistance as processes affecting fat distribution, providing insight into potential pathophysiological mechanisms