Meghan Sullivan

- Constraining the cosmological parameters and understanding Dark Energy have tremendous implications for the nature of the Universe and its physical laws. - The pervasive limit of systematic uncertainties reached by cosmography based on Cepheids and Type Ia supernovae warrants a search for complementary approaches. - Type II SNe have been shown to offer such a path. Their distances can be well constrained by luminosity-based or geometric methods. Competing, complementary, and concerted efforts are underway, to explore and exploit those objects that are extremely well matched to next generation facilities. Spectroscopic follow-up will be enabled by space- based and 20-40 meter class telescopes. - Some systematic uncertainties of Type II SNe, such as reddening by dust and metallicity effects, are bound to be different from those of SNe Ia. Their stellar progenitors are known, promising better leverage on cosmic evolution. In addition, their rate - which closely tracks the ongoing star formation rate - is expected to rise significantly with look- back time, ensuring an adequate supply of distant examples. - These data will competitively constrain the dark energy equation of state, allow the determination of the Hubble constant to 5%, and promote our understanding of the processes involved in the last dramatic phases of massive stellar evolution.

We present new results on the Hubble diagram of distant type Ia supernovae segregated according to the type of host galaxy. This makes it possible to check earlier evidence for a cosmological constant by explicitly comparing SNe residing in galaxies likely to contain negligible dust with the larger sample. The cosmological parameters derived from these SNe Ia hosted by presumed dust-free early-type galaxies support earlier claims for a cosmological constant, which we demonstrate at ≃5σ significance, and the internal extinction implied is small even for late-type systems. Thus, our data demonstrate that host galaxy extinction is unlikely to systematically dim distant SNe Ia in a manner that would produce a spurious cosmological constant. Our analysis is based on new Hubble Space Telescope STIS 'snapshot' images and Keck-II echellette spectroscopy at the locations of the SNe, spanning the redshift range 0 < z < 0.8. Selecting from the sample discovered by the Supernova Cosmology Project, we classify the host galaxies of 39 distant SNe using the combination of STIS imaging, Keck spectroscopy and ground-based broad-band photometry. The distant data are analysed in comparison with a low-redshift sample of 25 SNe Ia re-calibrated according to the precepts of the SCP. The scatter observed in the SNe Ia Hubble diagrams correlates closely with host galaxy morphology. We find this scatter is smallest for SNe Ia occurring in early-type hosts and largest for those occurring in late-type galaxies. Moreover, SNe residing in late-type hosts appear ≃0.14 ± 0.09 mag fainter in their light-curve-width-corrected luminosity than those in early-type hosts, as expected if a modest amount of dust extinction is a contributing factor. As in previous studies, these results are broadly independent of whether corrections based upon SN light-curve shapes are performed. We also use our high-redshift data set to search for morphological dependences in the SNe light curves, as are sometimes seen in lowredshift samples. No significant trends are found, possibly because the range of light-curve widths is too limited.

© 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.We use observedUVthrough near-IR spectra to examine whether SN 2011fe can be understood in the framework of Branch-normal Type Ia supernovae and to examine its individual peculiarities. As a benchmark, we use a delayed-detonationmodel with a progenitormetallicity of Z⊙/20. We study the sensitivity of features to variations in progenitor metallicity, the outer density profile, and the distribution of radioactive nickel. The effect of metallicity variations in the progenitor have a relatively small effect on the synthetic spectra. We also find that the abundance stratification of SN 2011fe resembles closely that of a delayed-detonation model with a transition density that has been fit to other Branch-normal SNe Ia. At early times, the model photosphere is formed in material with velocities that are too high, indicating that the photosphere recedes too slowly or that SN 2011fe has a lower specific energy in the outer ≈0.1 M⊙ than does the model. We discuss several explanations for the discrepancies. Finally, we examine variations in both the spectral energy distribution and in the colours due to variations in the progenitor metallicity, which suggests that colours are only weak indicators for the progenitor metallicity, in the particular explosion model that we have studied. We do find that the flux in the U band is significantly higher at maximum light in the solar metallicity model than in the lower metallicity model and the lower metallicity model much better matches the observed spectrum.

We present a measurement of the rate of distant Type la supernovae derived using four large subsets of data from the Supernova Cosmology Project. Within this fiducial sample, which surveyed about 12 deg2, 38 supernovae were detected at redshifts 0.25-0.85. In a spatially flat cosmological model consistent with the results obtained by the Supernova Cosmology Project, we derive a rest-frame Type la supernova rate at a mean redshift z ≃ 0.55 of 1.53-0.25-0.31-0.28-0.32 × 10-4 h 3 Mpc-3 yr-1 or 0.58-0.09-0.09-0.10-0.10 h2 SNu, where the first uncertainty is statistical and the second includes systematic effects. The dependence of the rate on the assumed cosmological parameters is studied and the redshift dependence of the rate per unit comoving volume is contrasted with local estimates in the context of possible cosmic star formation histories and progenitor models.

We present a method for selecting high-redshift Type la supernovae located via rolling SN searches. The technique, using both color and magnitude information of events from only two to three epochs of multiband real-time photometry, is able to discriminate between SNe la and core-collapse SNe. Furthermore, for SNe la the method accurately predicts the redshift, phase, and light-curve parameterization of these events based only on pre-maximum-light data. We demonstrate the effectiveness of the technique on a simulated survey of SNe la and core-collapse SNe, where the selection method effectively rejects most core-collapse SNe while retaining SNe la. We also apply the selection code to real-time data acquired as part of the Canada-France-Hawaii Telescope Supernova Legacy Survey. During the period 2004 May to 2005 January in the SNLS, 440 SN candidates were discovered, of which 70 were confirmed spectroscopically as SNe la and 15 as core-collapse events. For this test data set, the selection technique correctly identifies 100% of the identified SNe II as non-SNe la with only a 1%-2% false rejection rate. The predicted parameterization of the SNe la has a precision of | Δz|/ < 0.09 in redshift and ±2-3 rest-frame days in phase, providing invaluable information for planning spectroscopic follow-up observations. We also investigate any bias introduced by this selection method on the ability of surveys such as SNLS to measure cosmological parameters and find any effect to be negligible. © 2006. The American Astronomical Society. All rights reserved.

This chapter presents Peter van Inwagen's defense to the local argument from evil. According to van Inwagen, God may have been required to allow at least some contingent pointless evils because he faced a kind of sorites problem in deciding which world to create. This response stands in contrast to the more common strategy – skepticism about our ability to detect contingent pointless evils. The chapter unpacks van Inwagen's proposed explanation of pointless evils, surveys and responds to three objections, and proposes two extensions of his defense.

Notre Dame Philosophy professors Meghan Sullivan and Paul Blaschko have gone deep with that work in their wildly popular and influential undergraduate course GOD AND THE GOOD LIFE, in which they wrestle with the big questions about how to live and what makes life meaningful. Now they invite us into the classroom to tackle such issues as what justifies your beliefs, whether you should practice a religion, and what sacrifices you should make for others--as well as to investigate what Aristotle, Plato, Descartes, Kant, and Murdoch have to say about how to live well. Sullivan and Blaschko teach us how to reason through real-world case studies by doing the timeless work of philosophy like escaping our own caves, learning to doubt everything, asking strong questions, grasping our own purpose, and wrestling with the problem of evil and the existence of God. For at least the past 2500 years philosophers have taught that goal-seeking is an essential part of what it is to be human--and crucially that we could find our own good life by asking better questions. Their virtue ethics approach resonates profoundly in our own moment. Philosophers know that our "good life plan" is one that we as individuals need to be constantly and actively writing. In that work, we can achieve some meaningful control even if the world keeps throwing surprises our way. THE GOOD LIFE is a winning guide to tackling the big questions of being human with the wisdom of the ages.

Following the 2018 Pennsylvania grand jury report, which detailed the sexual abuse of clergy members, many have questioned the value of personal institutional commitment to the Catholic Church, preferring instead more individualistic expressions of faith. Alongside the sex abuse crisis, the age of free information makes the Church’s epistemology appear antiquated. This article explores the individualistic versus community-based practice of Catholicism, drawing a distinction between private conversion versus public conversion. The article offers a defense of public conversion, arguing it explains the rationality of conversion and offers a solution to the problem of divine hiddenness. Using details from her own faith journey, Sullivan explores why God graces us with less perspicuous knowledge, causing subluminous conversions, as opposed to the more glaring, which leads to luminous conversions. Sullivan suggests that we obtain knowledge of God by loving one another, which takes place in the framework of the institutional Church. She subsequently uses this Church-making theodicy to offer five ideas about how we might engage the Church institutionally as Catholic philosophers.