The total stellar halo mass of the Milky Way

We measure the total stellar halo luminosity using red giant branch (RGB) stars selected from Gaia data release 2. Using slices in magnitude, colour, and location on the sky, we decompose RGB stars belonging to the disc and halo by fitting two-dimensional Gaussians to the Galactic proper motion distributions. The number counts of RGB stars are converted to total stellar halo luminosity using a suite of isochrones weighted by age and metallicity, and by applying a volume correction based on the stellar halo density profile. Our method is tested and calibrated using Galaxia and N-body models. We find a total luminosity (out to 100 kpc) of Lhalo = 7.9 ± 2.0 × 108 L excluding Sgr, and Lhalo = 9.4 ± 2.4 × 108 L including Sgr. These values are appropriate for our adopted stellar halo density profile and metallicity distribution, but additional systematics related to these assumptions are quantified and discussed. Assuming a stellar mass-to-light ratio appropriate for a Kroupa initial mass function (M/L = 1.5), we estimate a stellar halo mass of M halo = 1.4 ± 0.4 × 109 M. This mass is larger than previous estimates in the literature, but is in good agreement with the emerging picture that the (inner) stellar halo is dominated by one massive dwarf progenitor. Finally, we argue that the combination of a ∼109 M mass and an average metallicity of [Fe/H]∼−1.5 for the Galactic halo points to an ancient (∼10 Gyr) merger event

The nitty gritty of South Carolina soil orders

Detailed information on soil orders of South Carolina is available but not in a digestible format for various state stakeholders. The goal of this first-semester Creative Inquiry is to develop stakeholder appropriate tools regarding general soil characteristics of South Carolina. A poster and interactive Web map depicting and explaining the soil orders of South Carolina are the first tools produced. Both the poster and Web map are targeted for K-12 teachers as teaching aids and will accompany a lesson plan for meeting school standards. The Web map will also be available for the public to use in exploring the soil orders of South Carolina. By the end of the first semester, students will determine complete lesson plans and present a lesson to two 7th grade science classes, and will identify at what classification level will soil attributes be used to integrate in to the interactive Web map

The Imprint of Cosmic Reionization on the Luminosity Function of Galaxies

The (re)ionization of hydrogen in the early universe has a profound effect on the formation of the first galaxies: by raising the gas temperature and pressure, it prevents gas from cooling into small halos, thus affecting the abundance of present-day small galaxies. Using the Galform semi-analytic model of galaxy formation, we show that two key aspects of the reionization process—when reionization takes place and the characteristic scale below which it suppresses galaxy formation—are imprinted in the luminosity function of dwarf galaxies. We focus on the luminosity function of satellites of galaxies like the Milky Way and the LMC, which is easier to measure than the luminosity function of the dwarf population as a whole. Our results show that the details of these two characteristic properties of reionization determine the shape of the luminosity distribution of satellites in a unique way, and are largely independent of the other details of the galaxy formation model. Our models generically predict a bimodality in the distribution of satellites as a function of luminosity: a population of faint satellites and population of bright satellites separated by a "valley" forged by reionization. We show that this bimodal distribution is present at high statistical significance in the combined satellite luminosity function of the Milky Way and M31. We make predictions for the expected number of satellites around LMC-mass dwarfs where the bimodality may also be measurable in future observational programs. Our preferred model predicts a total of 26 ± 10 (68% confidence) satellites brighter than M V = 0 in LMC-mass systems

Can we really pick and choose? Benchmarking various selections of Gaia Enceladus/Sausage stars in observations with simulations

Large spectroscopic surveys plus Gaia astrometry have shown us that the inner stellar halo of the Galaxy is dominated by the debris of Gaia Enceladus/Sausage (GES). With the richness of data at hand, there are a myriad of ways these accreted stars have been selected. We investigate these GES selections and their effects on the inferred progenitor properties using data constructed from APOGEE and Gaia. We explore selections made in eccentricity, energy-angular momentum (E-Lz), radial action-angular momentum (Jr-Lz), action diamond, and [Mg/Mn]-[Al/Fe] in the observations, selecting between 144 and 1279 GES stars with varying contamination from in-situ and other accreted stars. We also use the Auriga cosmological hydrodynamic simulations to benchmark the different GES dynamical selections. Applying the same observational GES cuts to nine Auriga galaxies with a GES, we find that the Jr-Lz method is best for sample purity and the eccentricity method for completeness. Given the average metallicity of GES (−1.28 < [Fe/H] < −1.18), we use the z = 0 mass–metallicity relationship to find an average of ∼4 × 108 M⊙. We adopt a similar procedure and derive for the GES-like systems in Auriga and find that the eccentricity method overestimates the true by ∼2.6 × while E-Lz underestimates by ∼0.7 ×. Lastly, we estimate the total mass of GES to be using the relationship between the metallicity gradient and the GES-to-in-situ energy ratio. In the end, we cannot just ‘pick and choose’ how we select GES stars, and instead should be motivated by the science question

Senior Capstone Lecture Recital: J. Jakari Rush, composer and pianist

This recital is presented in partial fulfillment of requirements for the degree Bachelor of Arts in Music. Mr. Rush studies composition with Laurence Sherr.https://digitalcommons.kennesaw.edu/musicprograms/1945/thumbnail.jp

Can we really pick and choose? Benchmarking various selections of Gaia Enceladus/Sausage stars in observations with simulations

Large spectroscopic surveys plus Gaia astrometry have shown us that the inner stellar halo of the Galaxy is dominated by the debris of Gaia Enceladus/Sausage (GES). With the richness of data at hand, there are a myriad of ways these accreted stars have been selected. We investigate these GES selections and their effects on the inferred progenitor properties using data constructed from APOGEE and Gaia. We explore selections made in eccentricity, energy-angular momentum (E-Lz), radial action-angular momentum (Jr-Lz), action diamond, and [Mg/Mn]-[Al/Fe] in the observations, selecting between 144 and 1,279 GES stars with varying contamination from in-situ and other accreted stars. We also use the Auriga cosmological hydrodynamic simulations to benchmark the different GES dynamical selections. Applying the same observational GES cuts to nine Auriga galaxies with a GES, we find that the Jr-Lz method is best for sample purity and the eccentricity method for completeness. Given the average metallicity of GES (-1.28 < [Fe/H] < -1.18), we use the $z=0$ mass-metallicity relationship to find an average $\rm M_{\star}$ of $\sim 4 \times 10^{8}$ $\rm M_{\odot}$. We adopt a similar procedure and derive $\rm M_{\star}$ for the GES-like systems in Auriga and find that the eccentricity method overestimates the true $\rm M_{\star}$ by $\sim2.6\times$ while E-Lz underestimates by $\sim0.7\times$. Lastly, we estimate the total mass of GES to be $\rm 10^{10.5 - 11.1}~M_{\odot}$ using the relationship between the metallicity gradient and the GES-to-in-situ energy ratio. In the end, we cannot just `pick and choose' how we select GES stars, and instead should be motivated by the science question.Comment: 20 pages, 14 figures, submitted to MNRA

2000 Philip C. Jessup

The State of Kuraca and the Republic of Senhava have submitted their differences concerning the vaccine trials to the International Court of Justice for resolution through a Special Agreement, in accordance with Article 40(1) of the Statute of the International Court of Justice