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Recent Submissions
Galaxy and Mass Assembly (GAMA): Stellar-to-dynamical Mass Relation. I. Constraining the Precision of Stellar Mass Estimates
(American Astronomical Society, 2023) Dogruel, M.Burak; Taylor, Edward; Cluver, Michelle; D�Eugenio, Francesco; Graaff, Anna de; Colless, Matthew; Sonnenfeld, Alessandro
In this empirical work, we aim to quantify the systematic uncertainties in stellar-mass (M⋆) estimates made from spectral energy distribution (SED) fitting through stellar population synthesis (SPS) for galaxies in the local Universe by using the dynamical mass (Mdyn) estimator as an SED-independent check on stellar mass. We first construct a statistical model of the high-dimensional space of galaxy properties; including size (Re), velocity dispersion (σe), surface brightness (Ie), mass-to-light ratio (M⋆/L), rest-frame color, Sérsic index (n), and dynamical mass (Mdyn), and accounting for selection effects and covariant errors. We disentangle the correlations among galaxy properties and find that the variation in M⋆/Mdyn is driven by σe, Sérsic index and color. We use these parameters to calibrate an SED-independent M⋆ estimator,
. We find the random scatter of the relation
to be 0.108 dex and 0.147 dex for quiescent and star-forming galaxies, respectively. Finally, we inspect the residuals as a function of SPS parameters (dust, age, metallicity, and star formation rate) and spectral indices (Hα, Hδ, and Dn4000). For quiescent galaxies, ∼65% of the scatter can be explained by the uncertainty in SPS parameters, with dust and age being the largest sources of uncertainty. For star-forming galaxies, while age and metallicity are the leading factors, SPS parameters account for only ∼13% of the scatter. These results leave us with remaining unmodelled scatters of 0.055 dex and 0.122 dex for quiescent and star-forming galaxies, respectively. This can be interpreted as a conservative limit on the precision in M⋆ that can be achieved via simple SPS modeling.
Variability in zinc:phosphorous and zinc:silicon ratios and zinc isotope fractionation in Southern Ocean diatoms: Observations from laboratory and field experiments
(Elsevier, 2023) Grun, Robin; Samanta, Moneesha; Ellwood, Michael
We studied the impact of iron limitation on zinc uptake and the zinc isotope (δ66Zn) composition for Southern Ocean phytoplankton. We undertook laboratory culture and field incubation experiments, and linked these to in situ depth profiles of dissolved (dZn) and particulate (pZn) zinc collected from three sites in the Southern Ocean. For the laboratory experiments, diatom growth rates, cellular zinc accumulation, and δ66Zn all responded to changes in iron and zinc bioavailability. A significant increase in the cellular quota for zinc (expressed as zinc:phosphorous (Zn:P)) occurred upon iron limitation and zinc enrichment. At the same time, δ66Zn for organic tissues became isotopically light under high zinc and low iron concentrations. The opposite occurred for frustule δ66Zn values. Here δ66Znfrustule-organic for cultured phytoplankton became isotopically heavier under high zinc and low iron concentrations. For senescing and dead cells, Zn:P declined and δ66Zn increased, indicating a loss of isotopically light zinc from organic matter. For field incubation experiments, δ66Znfrustule was isotopically heavier than seawater, except for added zinc treatments. The percentage of zinc associated with frustule material for laboratory and field incubations encompassed a wide range with values between 1 and 57%. Depth profiles of δ66Zn for dZn and pZn varied, with dZn being isotopically lighter than pZn in low dZn concentration subantarctic waters, whereas the opposite occurred in polar waters where dZn was isotopically heavier than pZn at higher dZn concentrations. Our results show that iron and zinc availability regulates the zinc content of phytoplankton and the δ66Zn composition of the Southern Ocean, which is propagated to other parts of the world ocean.
Homer and the Art of Storytelling
(Joint Association of Classical Teachers, 1999) Minchin, Elizabeth
There is not a day that passes when we do not tell a friend or a family member an anecdote concerning events that have happened to us in the course of the day, or pass on a story that we ourselves have heard. We make stories out of events of all kinds: the shocking, the amusing, the trivial, and the momentous. Each of us is something of an expert on storytelling:we all know, instinctively, how to go about it, and there are some who can make a great success of any story. Western culture, like any other, has a long tradition of storytelling, which we can trace back for thousands of years. The first of our storytellers to be recorded, the epic poet Homer, has always been regarded as a master-storyteller. But few have paused to examine his storytelling habits from the perspective of storytellers today.
Call to action for equitable access to human milk for vulnerable infants
(Elsevier, 2019) Israel-Ballard, Kiersten; Cohen, Jessica; Mansen, Kimberly; Parker, Michael; Engmann, Cyril; Kelley, Maureen; Smith, Julie
Paramedics and the Mentally Ill - Victoria
(Australian Emergency Law, 2016-01-02) Eburn, Michael; Townsend, R.