2018 MASC Presentation List

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The following provides you with a summary of the presentations that will be given at the Meeting of Astronomers of South Carolina. Order in the table does not reflect order of presentations.

Last Name First Name Institution Title of Presentation Abstract
2018 Presentation List
Myers Jeannette Francis Marion University Celebrating 40 Years of Astronomy at Francis Marion University In January 1978, the Planetarium at Francis Marion College first began hosting free programs to the Pee Dee Region. In this presentation we will look back at some of the events from our history and plans we have for the next few years. We'll also discuss our plans for the 50th anniversary of Apollo 11.
Hartmann Dieter Clemson University Binary Neutron Star Mergers: Catching the electromagnetic afterglows of gravitational wave events The LIGO/VIRGO /Fermi discovery of nearby GW170817/GRB170817A and its global follow-up pushed the Multimessenger window wide open. I will discuss the new area of kilonova astrophysics revealed by this groundbreaking event and plans for the next round of ground- and space-based follow-up of gravitational wave events. The improved sensitivity of the coming installment of laser interferometers will push the diastase limit to which we can see such mergers and thus produce these opportunities at an increased rate, so the community is gearing up for exciting times.
Kirby Alexander University of South Carolina Constraining Extinction due to Dust in Distant Galaxies Extinction due to interstellar dust is a ubiquitous phenomenon that dims and reddens the light of background objects. As such, it is essential to apply extinction corrections to observations of distant objects in order to deduce their properties. Since the discovery of interstellar extinction in 1930, astronomers have developed a fairly detailed understanding of the interstellar dust in the Milky Way and other Local Group galaxies, especially the Magellanic Clouds. However, studies of extinction by dust in galaxies beyond the Local Group have been limited. In this work, we seek to generate better constraints on dust extinction in other galaxies in order to improve corrections for observations of objects that lie beyond them. As such, we are constructing spectral energy distributions (SEDs) for quasars/active galactic nuclei whose lines of sight go through foreground galaxies at lower redshifts. We will describe our compilation of archival optical, UV, and IR spectroscopic and photometric data from various observatories. Using the SEDs compiled from these data, and fitting the underlying continuum of the background quasar/AGN, we will estimate dust extinction curves for each foreground galaxy, and compare those with extinction curves in the Milky Way and the Magellanic Clouds.
Desai Abhishek Clemson University EBL with Pass 8 The extragalactic background light (EBL), from ultra-violet to infrared, that encodes the emission from all stars, galaxies and actively accreting black holes in the observable Universe is critically important to probe models of star formation and galaxy evolution, but remains at present poorly constrained. The Large Area Telescope (LAT), on board Fermi, produced an unprecedented measurement (relying on 750 blazars and the first 9 years of Pass 8 data) of the EBL optical depth at 12 different epochs from redshift 0 up to a redshift of 3. In this talk, I will present the measurement and how it constrains the EBL energy density and its evolution with cosmic time. I will also discuss how this paves the road to the first point-source-independent determinations of the star-formation history of the Universe.
Marchesi Stefano Clemson University A multi-observatory X-ray approach to characterize heavily obscured AGN According to the different models of Cosmic X-ray Background (CXB), the diffuse X-ray emission observed in the 1 to ~200-300 keV band, is mainly caused by accreting supermassive black holes, the so-called active Galactic Nuclei (AGN). Particularly, at the peak of the CXB (~30 keV) a significant fraction of emission (10-25%) is expected to be produced by a numerous population of heavily obscured, Compton thick (CT-) AGN, having intrinsic column density NH>=1E24 cm{-2}. Nonetheless, in the nearby Universe (z<=0.1) the observed fraction of CT-AGN with respect to the total population appears to be lower than the one expected on the basis of the majority of CXB model predictions (~20-30%), being between 5 and 10%. This discrepancy between data and models is one of the open challenges for X-ray astronomers, and needs to be solved to get a complete understanding of the AGN population. In this presentation, I will discuss a multi-observatory X-ray approach to find and characterize heavily obscured AGN. Candidate sources are first selected in the 100-month Swift-BAT catalog, the result of a ~7 years all-sky survey in the 15-150 keV band. These objects are then targeted with snapshot (5-10 ks) observations with Chandra and Swift-XRT, which allow us to constrain the intrinsic absorption value within a 20-30% uncertainty. Finally, deep (25-50 ks) observations with XMM-Newton and NuSTAR allow us to study the physics of these complex and elusive sources.
Kulkarni Varsha University of South Carolina Probing Structure in Cold Gas in Galaxies with Gravitationally Lensed Quasars Absorption lines in quasar spectra offer a powerful tool to study the gas and metals in and around galaxies. Gravitationally lensed quasars (GLQs) probe multiple sight lines through foreground galaxies, and can thus enable comparisons of the gas and metal content in different parts of the galaxies. We report spectroscopic observations of 4 GLQs, each consisting of a pair of images with a projected separation of a few kpc at the redshift of the foreground galaxy. We measure the H I absorption lines using HST STIS UV spectra, and metal absorption lines using optical spectra of the GLQs. Combining the H I and metal information, we estimate element abundances along the two sight lines for each field. Using these measurements, together with projected separations between the two sight lines derived from HST imaging data, we estimate the gradients in H I column density and metallicity  through the foreground galaxies.
Marcotulli Lea Clemson University The Density of Blazars above 100 MeV and the Origin of the Extragalactic Gamma-ray Background Relying on the first 104 months of Fermi-LAT Pass 8 data, using detailed Monte Carlo simulations, we obtained the most sensitive measurement of the source count distribution of blazars above 100 MeV. The result shows, with high statistical significance, the presence of a break in the distribution at low fluxes. From this, we provide a precise measurement of the contribution of blazars to the extragalactic gamma-ray background (EGB). Furthermore, we confirm that they can not account for the total EGB, therefore, another source class is required to explain the remaining component. In this talk, we will present this new measurement and discuss alternatives for the origin of the missing EGB component.
Poudel Suraj University of South Carolina Metallicity measurements of elements in gas-rich absorbers at redshift z ~5 Element abundances in high-redshift galaxies offer key constraints on models of the chemical evolution of galaxies. The chemical composition of galaxies at z~5 are especially important since they constrain the star formation history in the first ~1 Gyr after the Big Bang and the initial mass function of early stars. Observations of damped Lyman-alpha (DLA) absorbers in quasar spectra enable robust measurements of the element abundances in distant gas-rich galaxies. In particular, abundances of volatile elements such as S, O and refractory elements such as Si, Fe allow determination of the dust-corrected metallicity and the depletion strength in the absorbing galaxies. Unfortunately measurements for volatile (nearly undepleted) elements are very sparse for DLAs at z > 4.5. We present abundance measurements of O, C, Si and Fe for three gas-rich galaxies at z ∼ 5 using observations from the Very Large Telescope (VLT) X-shooter spectrograph and the Keck ESI (Echellette Spectrograph and Imager). Our study has doubled the existing sample of measurements of undepleted elements at z > 4.5. After combining our measurements with those from the literature, we find that the NHI-weighted mean metallicity of z ∼ 5 absorbers is lower at < 0.5 level compared to the prediction based on z < 4.5 DLAs. Thus, we find no significant evidence of a sudden drop in metallicity at z > 4.7 as reported by prior studies. Some of the absorbers show evidence of depletion of elements on dust grains, e.g. low [Si/O] or [Fe/O]. These absorbers along with other z ∼ 5 absorbers from the literature show some peculiarities in the relative abundances, e.g. low [C/O] in several absorbers and high [Si/O] in one absorber. We also find that the metallicity vs. velocity dispersion relation of z ∼ 5 absorbers may be different from that of lower-redshift absorbers. 
We acknowledge support from NASA grant NNX14AG74G and NASA/STScI support for HST programs GO-12536, 13801 to the Univ. of South Carolina. 
Cashman Francie University of South Carolina Determining Chemical Gradients in Hot Gas at z~2.2 using Sight Lines to Gravitationally Lensed Quasars

Absorption line spectroscopy using quasars is a powerful method to study galaxies and intergalactic systems. Multiple systems along the line of sight to a quasar can be differentiated, since absorption lines are redshifted to longer wavelengths at higher redshifts. Use of gravitationally lensed quasars (GLQs) can extend this technique by probing multiple sight lines through these foreground galaxies, offering an in-depth look at the internal structure of the environment. GLQs with closely spaced sight lines (< 10 kpc) allow us to probe smaller structure within the galaxy’s ISM and thereby study variations in gas, metal, and dust in different regions. We report spectroscopic observations of 2 separate absorbing systems at z=2.2 and z=2.3 along the line of sight to a GLQ at z=2.5. Each observation consists of a pair of images with a projected separation of 6.9 and 7.0 kpc respectively at the redshifts of the foreground galaxies. The H I and metal absorption lines were measured using optical spectra taken with the MagE spectrograph on the 6.5 meter Magellan telescope in Chile and were used to estimate column densities along the lines of sight. We detect elements in high ionization stages, i.e., O VI, C IV, N V, Si IV, and Fe III, allowing us to probe different directions through the high temperature outer envelope of each galaxy.

Co-authors:
Varsha Kulkarni, Dept. of Physics & Astronomy, University of South Carolina, USA

Sebastian Lopez, Dept. de Astronomia, Universidad de Chile, Casilla 36-D, Santiago, Chile

Sara Ellison, University of Victoria, Dept. of Physics and
Astronomy, Victoria, BC, V8W 2Y2, Canada

Debopam Som, Aix Marseille Universit ́e, CNRS, Laboratoire d’Astrophysique de Marseille, UMR 7326, 13388, Marseille, France

Roberts-Pierel Justin University of South Carolina Extending Supernova Spectral Templates for Next Generation Space Telescope Observations Widely used empirical supernova (SN) Spectral Energy Distributions (SEDs) have not historically extended meaningfully into the ultraviolet (UV), or the infrared (IR). However, both are critical for current and future aspects of SN research including UV spectra as probes of poorly understood SN Ia physical properties, and expanding our view of the universe with high-redshift James Webb Space Telescope (JWST) IR observations. We therefore present a comprehensive set of SN SED templates that have been extended into the UV and IR, as well as an open-source software package written in Python that enables a user to generate their own extrapolated SEDs. We have taken a sampling of core-collapse (CC) to get a time-dependent distribution of UV and IR colors (U-B,r’-[JHK]), and then generated color curves are used to extrapolate SEDs into the UV and IR. Type Ia SNe with observations in the UV and IR are used to extrapolate the existing Type Ia SALT2-4 parameterized model. The SED extrapolation process is now easily duplicated using a user’s own data and parameters via our open-source Python package: SNSEDextend. This work develops the tools necessary to explore the JWST’s ability to discriminate between CC and Type Ia SNe, as well as provides a repository of SN SEDs that will be invaluable to future JWST and WFIRST SN studies.
Garrity April Francis Marion University Recoil Detection and Focal Plane Detectors for the SEparator for CApture Reactions (SECAR) The Separator for Capture Reactions (SECAR) will be installed at NSCL/FRIB to directly measure (p,$\gamma$) and ($\alpha$,$\gamma$) reactions that are important in extreme stellar environments. Time-of-flight detectors like those implemented in SECAR are necessary to distinguish between the heavy products of the desired reactions and the unreacted beam. The time resolution and position sensitivity of a micro-channel plate (MCP) detector for the SECAR focal plane instrumentation were tested. We will present the findings of these tests as well as an alternate high energy design of a stopping detector. The new stopping detector will be characterized in further in-beam studies, and both it and the MCP detectors will be installed at NSCL/FRIB by 2022.
Zhao Xiurui Clemson University NuSTAR and XMM-Newton view of NGC 1358 The obscuration of active galactic nuclei (AGN) is important for the co-evolution of the supermassive black hole and its host galaxy, and for cosmic X-ray background (CXB). Significant number of heavily obscured AGNs are thought needed to reproduce the peak (~30 keV) of CXB in nearby universe, while only part of them are found. Marchesi et al. (2018), utilizing Chandra and Swift-BAT spectra, analyze several Seyfert 2 galaxies from the Swift-BAT 100 month catalog. Following this work, we study one of their Compton-Thick AGN (with column density NH >= 1024 cm-2) candidate, NGC 1358, with unprecedented statistics by using NuSTAR (3-79 keV, 50 ks) and XMM-Newton (0.3-10 keV, 48 ks) pointed observations. In this presentation, I will report some physical properties of our target such as the photon index and column density of the absorption material by using phenomenological model and physical models.