New time series photometry of WISE J152614.95-111326.4, an eclipsing binary candidate, has been obtained. Full cycles of variation were covered in five filters, ranging from B to z. Archival time series photometry is also available from several sources. The phased light curve shape changes from a double wave form in the red, to a single wave at shorter wavelengths. Analysis of the spectral energy distribution and SALT spectra shows the presence of a cool (∼ 7250−7900 K) white dwarf and an M6 star. The light curves can be explained by a hot spot on the opposing hemisphere of the white dwarf. The star may be in a pre-cataclysmic variable phase with a very low rate of mass flow from the red dwarf to the white dwarf, such that no flickering is evident. Evidence in favour of this hypothesis is that the period of the system (2.25 h) is in the cataclysmic variable period gap. It is speculated that a weak magnetic field associated with the white dwarf funnels accreted material onto a magnetic pole. Amplitudes of the W1 and W2 WISE light curves are anomalously large. The possibility is discussed that variability in this spectral region is primarily driven by electron cyclotron radiation.

Environment has long been known to have an impact on the evolution of galaxies, but disentangling its impact from mass evolution requires the careful analysis of statistically significant samples. By implementing cutting-edge visualisation methods to test and validate group-finding algorithms, we utilise a mass-complete sample of galaxies to z < 0.1 comprised of spectroscopic redshifts from prominent surveys such as the 2-degree Field Galaxy Redshift Survey and the Galaxy and Mass Assembly Survey. Utilising our group finding methods, we find 1,413 galaxy groups made up of 8,990 galaxies corresponding to 36% of galaxies associated with group environments. We also search for close pairs, with separations of rsep < 50 h−1kpc and vsep < 500 km s−1 within our sample and further classified them into major (Msec/Mprim ≤ 0.25) and minor (Msec/Mprim > 0.25) pairs. To examine the impact of environmental factors, we employ bespoke WISE photometry, which facilitates accurate measurements of stellar mass and star formation rates and hence the best possible description of the variation of galaxy properties as a function of the local environment. Our analysis, employing a derived star-forming main sequence relation, reveals that star-formation (SF) within galaxies are pre-processed as a function of group membership. This is evident from the evolution of the star-forming and quenched population of galaxies. We see an increase in the fraction of quiescent galaxies relative to the field as group membership increases and this excess of quenched galaxies relative to the field is later quantified through the use of the environmental quenching efficiency (εenv) metric. Within the star-forming population, we observe SF pre-processing with the relative difference in specific star formation rates (∆sSFR), where we see a net decrease in SF as group membership increases, particularly at larger stellar masses. We again quantify this change within the SF population with our star formation deficiency (εSFD) metric. Our sample of close pairs at low stellar masses exhibit enhanced star formation efficiencies compared to the field, and at larger stellar mass ranges show large deficiencies. Separating the close pairs into major/minors and primary/secondaries reveals SF enhancements projected separation decreases within the minor pairs, this effect is even more pronounced within minor primaries. This research emphasises the importance of carefully studying the properties of galaxies within group environments to better understand the pre-processing of SF within galaxies. Our results show that the small-scale environments of galaxies influence star-forming properties even when stellar masses are kept constant. This demonstrates that galaxies do not evolve in isolation over cosmic time but are shaped by a complex interaction between their internal dynamics and external influences.

Simulations suggest that slow rotating galaxies are the result of galaxy-galaxy mergers that have a tendency to randomise stellar orbits. The exact pathway for slow rotator formation, however, is still unclear. Our aim is to see whether there is a relationship between fossil groups - whose central galaxies are thought to have undergone more major merging than other central galaxies - and the stellar kinematic properties of those central galaxies. We classify all galaxy groups in the GAMA redshift survey whose central galaxies were observed with SAMI as: i) fossil groups, ii) mass gap groups (fossil-like groups), and iii) groups that are not dynamically evolved (NDEGs, i.e. controls). We compare the following properties of centrals across the three different group types: spin (λRe), the fraction of slow rotators (fSR), and age. We also repeat our analysis on data from the EAGLE and MAGNETICUM hydrodynamical cosmological simulations. In SAMI, we find that the spin parameter, slow rotator fraction, and age are broadly consistent across our three group types, i.e. the fossil groups, mass gap groups and NDEGs. We do find a weak indication that fSR is slightly lower for fossil group centrals as compared to NDEG centrals. In contrast, in EAGLE and MAGNETICUM, fossil and mass gap group centrals typically have a significantly lower λRe than NDEG centrals. Our results for SAMI suggest that the types of mergers that form fossil groups are not the types of mergers that form slow rotators. Merger count may be less important for slow rotator formation than specific merger conditions, such as the gas content of progenitors. When and where the merging occurs are also suspected to play an important role in slow rotator formation, and these conditions may differ for fossil group formation.