https://nova.newcastle.edu.au/vital/access/ /manager/Index ${session.getAttribute("locale")} 5 https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:33990 Wed 04 Sep 2019 09:48:58 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:34083 ⊙), cold (12 K), and 3.6–70 μm IR dark clump (MM1) that has the potential to form high-mass stars. We observed this prestellar clump candidate with the Submillimeter Array (~3".5 resolution) and Jansky Very Large Array (~2farcs1 resolution) in order to characterize the early stages of high-mass star formation and to constrain theoretical models. Dust emission at 1.3 mm wavelength reveals five cores with masses ≤15 M_⊙. None of the cores currently have the mass reservoir to form a high-mass star in the prestellar phase. If the MM1 clump will ultimately form high-mass stars, its embedded cores must gather a significant amount of additional mass over time. No molecular outflows are detected in the CO (2-1) and SiO (5-4) transitions, suggesting that the SMA cores are starless. By using the NH₃ (1, 1) line, the velocity dispersion of the gas is determined to be transonic or mildly supersonic (ΔV_nt/ΔV_th ~ 1.1–1.8). The cores are not highly supersonic as some theories of high-mass star formation predict. The embedded cores are four to seven times more massive than the clump thermal Jeans mass and the most massive core (SMA1) is nine times less massive than the clump turbulent Jeans mass. These values indicate that neither thermal pressure nor turbulent pressure dominates the fragmentation of MM1. The low virial parameters of the cores (0.1–0.5) suggest that they are not in virial equilibrium, unless strong magnetic fields of ~1–2 mG are present. We discuss high-mass star formation scenarios in a context based on IRDC G028.23-00.19, a study case believed to represent the initial fragmentation of molecular clouds that will form high-mass stars.]]> Tue 03 Sep 2019 18:23:32 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:32088 Galaxy Evolution Explorer near-ultraviolet (NUV) galaxy photometry with the Sloan Digital Sky Survey group catalogue of Yang et al. We compared the (NUV − r) colours of grouped and non-grouped galaxies, and find a significant increase in the fraction of red sequence galaxies with blue (NUV − r) colours outside of groups. When comparing galaxies in mass-matched samples of satellite (non-central), and non-grouped galaxies, we found a >4σ difference in the distribution of (NUV − r) colours, and an (NUV − r) blue fraction >3σ higher outside groups. A comparison of satellite and non-grouped samples has found the NUV fraction is a factor of ∼2 lower for satellite galaxies between 10^10.5 and 10^10.7,M _⊙, showing that higher mass galaxies are more likely to have residual star formation when not influenced by a group potential. There was a higher (NUV − r) blue fraction of galaxies with lower Sérsic indices (n < 3) outside of groups, not seen in the satellite sample. We have used stellar population models of Bruzual & Charlot with multiple burst, or exponentially declining star formation histories to find that many of the (NUV − r) blue non-grouped galaxies can be explained by a slow (∼2 Gyr) decay of star formation, compared to the satellite galaxies. We suggest that taken together, the difference in (NUV − r) colours between samples can be explained by a population of secularly evolving, non-grouped galaxies, where star formation declines slowly. This slow channel is less prevalent in group environments where more rapid quenching can occur.]]> Fri 27 Apr 2018 15:08:51 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:32637 Fri 23 Jun 2023 12:15:31 AEST ]]>