Physical Sciences and Mathematics Commons^™

The Loneliest Galaxies In The Universe: A Gama And Galaxy Zoo Study On Void Galaxy Morphology., Lori E. Porter

College of Arts & Sciences Senior Honors Theses

The large-scale structure (LSS) of the Universe is comprised of galaxy filaments, tendrils, and voids. The majority of the Universe’s volume is taken up by these voids, which exist as underdense, but not empty, regions. The galaxies found inside voids are void galaxies and expected to be some of the most isolated objects in the Universe. However, their standard morphology remains poorly studied. This study, using the Galaxy and Mass Assembly (GAMA) data and Galaxy Zoo survey, aims to remedy this. For completeness purposes, we use void galaxies identified by Alpaslan et al. (2014) with stellar masses (M*) of 10 …

Where Are The Habitable Planets In Our Local Group Of Galaxies?, William C. Windsor

Undergraduate Student Research Internships Conference

No abstract provided.

Characterizing Agn Influence On The Calculated Metallicities Of Adjacent Star-Forming Spaxels, Aidan Khelil

Honors Papers

In this thesis, I introduce a method to identify and characterize the effects of active galactic nuclei (AGN) on the spectra of nearby star-forming regions. I analyze spatially-resolved areas of galaxies called “spaxels” within Data Release 15 of the Sloan Digital Sky Survey (SDSS) with the goal of locating those which are physically close to AGN. I find those spaxels with calculated metallicities which lie adjacent to AGN-flagged spaxels and characterize their metallicity values relative to the spaxels which are not adjacent to AGN-flagged spaxels, using a total of 11 separate metallicity calibrations. I find that the current methods to …

Luminosity Functions Of Galaxy Clusters In The Aquarius And Microscopium Superclusters, Logan A. Hess

Electronic Theses and Dissertations

We examine physical properties of several galaxy clusters located within the Aquarius (AQR) and Microscopium (MSC) super-cluster complexes via their luminosity functions, fitted using Schechter functions. Images of clusters were acquired via the DECam (Dark Energy Camera) imager of the 4-meter diameter telescope at CTIO (Cerro Tololo Inter-American Observatory). We observe six clusters in our sample; four from the Aquarius supercluster (AQR 2541, 2546, 2554, 2555) and two from the Microscopium supercluster (MSC 3695, 3696). Magnitude information and density of member galaxies in each cluster were extracted via the SExtractor software utility from obtained images. We correct for background by …

Problems Of Classification Of Globular Clusters And Their Systems, Nuritdinov Saloxutdin, Ikram Tadjibaev

Bulletin of National University of Uzbekistan: Mathematics and Natural Sciences

A review is carried out mainly of the classification problems of globular clusters (GC) of our Galaxy. Classification of GC has a rich history, since it was first considered by Shapley and Sawyer [1] over 90 years ago. After them, a number of authors [2-8] tried to classify GC in various ways, but however, before our work no one was able to solve this problem to the desired level. We first studied the physical characteristics of the GC of our Galaxy by constructing diagrams of the relationship between these characteristics. Next, we decided to answer the question of whether it …

Comparing Dust In Other Galaxies To Dust In Our Galaxy, Fatima Elkhatib

Senior Theses

Interstellar dust in galaxies has a profound effect on the galaxies’ light output and apparent properties as well as on the physical processes connected to star formation. Therefore, to understand the true properties of the galaxies around us, it is important to understand the dust in those galaxies and compare it to the dust in our galaxy. To do this, we study the effects of dust on background quasars by analyzing interstellar reddening and extinction. It has been shown that many quasars look redder and dimmer than the average quasar when observing them from Earth, due to the dust in …

Towards Gross-Pitaevskiian Description Of Solar System & Galaxies, Florentin Smarandache, Victor Christianto, Yunita Umniyati

Branch Mathematics and Statistics Faculty and Staff Publications

In this paper, we argue that Gross-Pitaevskii model can be a more complete description of both solar system and spiral galaxies, especially taking into account the nature of chirality and vortices in galaxies. We also hope to bring out some correspondence among existing models, e.g., the topological vortex approach, Burgers equation in the light of KAM theory, and the Cantorian Navier-Stokes approach. We hope further investigation can be done around this line of approach.

The Acs Survey Of Galactic Globular Clusters Xiv: Bayesian Single-Population Analysis Of 69 Globular Clusters, R. Wagner-Kaiser, Ted Von Hippel, A. Sarajedini, D. C. Stenning, D. A. Van Dyck, Et Al.

Ted von Hippel

We use Hubble Space Telescope (HST) imaging from the ACS Treasury Survey to determine fits for single population isochrones of 69 Galactic globular clusters. Using robust Bayesian analysis techniques, we simultaneously determine ages, distances, absorptions, and helium values for each cluster under the scenario of a \single" stellar population on model grids with solar ratio heavy element abundances. The set of cluster parameters is determined in a consistent and reproducible manner for all clusters using the Bayesian analysis suite BASE-9. Our results are used to re-visit the age-metallicity relation. We find correlations with helium and several other parameters such as …

A Hierarchical Model For The Ages Of Galactic Halo White Dwarfs, Shijing Si, Ted Von Hippel, David A. Van Dyk, Elliot Robinson, Aaron Webster, Et Al.

Ted von Hippel

In astrophysics, we often aim to estimate one or more parameters for each member object in a population and study the distribution of the fitted parameters across the population. In this paper, we develop novel methods that allow us to take advantage of existing software designed for such case-by-case analyses to simultaneously fit parameters of both the individual objects and the parameters that quantify their distribution across the population. Our methods are based on Bayesian hierarchical modelling which is known to produce parameter estimators for the individual objects that are on average closer to their true values than estimators based …

Infrared Properties Of Stars In The Bulge Asymmetries And Dynamical Evolution Survey, Eddie Hilburn

Physics & Astronomy ETDs

The Bulge Asymmetries and Dynamical Evolution (BAaDE) survey is an SiO maser survey of 28,062 infrared-selected evolved stars primarily in the Galactic plane. By cross-matching the BAaDE target sources with nine different infrared catalogs, we have constructed a catalog with wavelength coverage from 0.71 to 80 m. Using this catalog, we fit the data for each source to a model spectral energy distribution (SED) generated with the radiation transport program DUSTY in order to obtain characteristics such as bolometric flux, source effective temperature, and the optical depth of the circumstellar envelope.

The overall goal of the BAaDE survey is to …

Almost Dark Galaxies: The Search For Optical Counterparts, Quinton O. Singer

Macalester Journal of Physics and Astronomy

Presented in this paper are results from neutral hydrogen (HI) imaging and analysis of the "Almost Dark" galaxies AGC 219533, AGC 227982, and AGC 268363 using new, higher resolution observations from the Very Large Array (VLA). Selected from the ALFALFA survey, "Almost Dark" galaxies possess significant HI reservoirs but, when the HI data is compared to survey-depth ground-based optical imaging, their optical stellar counterparts have extremely low surface brightnesses. AGC 219533 is one such object. The other two sources, AGC 227982 and AGC 26833, were candidate dark galaxies, as no stellar counterpart was identified in initial ALFALFA optical matching, and …

A Hierarchical Model For The Ages Of Galactic Halo White Dwarfs, Shijing Si, Ted Von Hippel, David A. Van Dyk, Elliot Robinson, Aaron Webster, Et Al.

Publications

In astrophysics, we often aim to estimate one or more parameters for each member object in a population and study the distribution of the fitted parameters across the population. In this paper, we develop novel methods that allow us to take advantage of existing software designed for such case-by-case analyses to simultaneously fit parameters of both the individual objects and the parameters that quantify their distribution across the population. Our methods are based on Bayesian hierarchical modelling which is known to produce parameter estimators for the individual objects that are on average closer to their true values than estimators based …

The Acs Survey Of Galactic Globular Clusters Xiv: Bayesian Single-Population Analysis Of 69 Globular Clusters, R. Wagner-Kaiser, Ted Von Hippel, A. Sarajedini, D. C. Stenning, D. A. Van Dyck, Et Al.

Publications

We use Hubble Space Telescope (HST) imaging from the ACS Treasury Survey to determine fits for single population isochrones of 69 Galactic globular clusters. Using robust Bayesian analysis techniques, we simultaneously determine ages, distances, absorptions, and helium values for each cluster under the scenario of a \single" stellar population on model grids with solar ratio heavy element abundances. The set of cluster parameters is determined in a consistent and reproducible manner for all clusters using the Bayesian analysis suite BASE-9. Our results are used to re-visit the age-metallicity relation. We find correlations with helium and several other parameters such as …

An Empirical Approach To Understanding Of Star Formation In Dark Matter Halos, Zhankui Lu

Doctoral Dissertations

We present a data-driven approach to understand the star formation in dark matter halos over cosmic time. With a simple empirical model and advanced tools for Bayesian inference, we try to constrain how galaxies have assembled their stars across cosmic time using stellar mass functions (SMFs) and the luminosity function of cluster galaxies. The key ingredients of the empirical model include dark halo merger trees and a generic function that links star formation rate (SFR) to the host halos. We found a new characteristic redshift z_c ~ 2 above which the SFR in low mass halos < 10¹¹ solar mass …

A Re-Interpretation Of The Triangulum-Andromeda Stellar Clouds: A Population Of Halo Stars Kicked Out Of The Galactic Disk, Adrian M. Price-Whelan, Kathryn V. Johnston, Allyson A. Sheffield, Chervin F. P. Laporte, Branimir Sesar

Publications and Research

The Triangulum–Andromeda stellar clouds (TriAnd1 and TriAnd2) are a pair of concentric ring- or shell-like overdensities at large R (≈30 kpc) and Z (≈−10 kpc) in the Galactic halo that are thought to have been formed from the accretion and disruption of a satellite galaxy. This paper critically reexamines this formation scenario by comparing the number ratio of RR Lyrae to M giant stars associated with the TriAnd clouds with other structures in the Galaxy. The current data suggest a stellar population for these overdensities (fRR: MG < 0.38 at 95 per cent confidence) quite unlike any of the known satellites of the Milky Way (fRR: MG ≈ 0.5 for the very largest and f …

Bayesian Anatomy Of Galaxy Structure, Ilsang Yoon

Open Access Dissertations

In this thesis I develop Bayesian approach to model galaxy surface brightness and apply it to a bulge-disc decomposition analysis of galaxies in near-infrared band, from Two Micron All Sky Survey (2MASS). The thesis has three main parts.

First part is a technical development of Bayesian galaxy image decomposition package Galphat based on Markov chain Monte Carlo algorithm. I implement a fast and accurate galaxy model image generation algorithm to reduce computation time and make Bayesian approach feasible for real science analysis using large ensemble of galaxies. I perform a benchmark test of Galphat and demonstrate significant improvement in parameter …

Abundance Patterns In The Spiral Galaxy Messier 33, Melissa A. Siemer, Ravi Sankrit

STAR Program Research Presentations

Messier 33 (M33) is a spiral disk galaxy, similar to our galaxy, approximately 3 million light-years from Earth. Because of its proximity to Earth and face-on viewing angle, it is easy to see individual objects. Consequently, M33 is in an ideal position for obtaining data on elemental abundances. By studying M33, we learn how galaxies like our own form and change over time.

We use published optical spectroscopic data, obtained and assembled from online sources, to map the abundances of various elements (Helium, Nitrogen, Oxygen, Neon, Argon, Sulfur) in the planetary nebula and HII region populations of M33. We classify …

A Four-Year Xmm-Newton/Chandra Monitoring Campaign Of The Galactic Centre: Analysing The X-Ray Transients, N. Degenaar, R. Wijnands, E. M. Cackett, J. Homan, J. J. M. In 'T Zand, E. Kuulkers, T. J. Maccarone, M. Van Der Klis

Physics and Astronomy Faculty Research Publications

We report on the results of a four-year long X-ray monitoring campaign of the central 1.2 square degrees of our Galaxy, performed with Chandra and XMM-Newton between 2005 and 2008. Our study focuses on the properties of transient X-ray sources that reach 2-10 keV luminosities of L_X ≳ 10³⁴ erg s^-1 for an assumed distance of 8 kpc. There are 17 known X-ray transients within the field of view of our campaign, eight of which were detected in outburst during our observations: the transient neutron star low-mass X-ray binaries GRS 1741-2853, AX J1745.6-2901, SAX J1747.0-2853, KS 1741-293 …

Stellar Fossils: Globular Clusters As Probes Of The Galaxy, Shane L. Larson

Public Talks

No abstract provided.

High-Resolution Ultraviolet Spectroscopy Of Gas In Galaxy Halos And Large-Scale Structures, Limin Song

Open Access Dissertations

This dissertation presents spectroscopic studies of gas in galaxy halos and large-scale structures through high-resolution quasar absorption lines. The broad goal of this effort is to learn how galaxies acquire their gas and how they return it to the intergalactic medium, or more generally, how galaxies interact with their environment. The study of the absorption lines due to the extraplanar 21cm "Outer Arm'' (OA) of the Milky Way toward two quasars, H1821+643 and HS0624+6907, provides valuable insight into the gas accretion processes. It yields the following results. (1) The OA is a multiphase cloud and high ions show small but …

The Dark Side Of The Universe: Dark Matter In The Galaxy And Cosmos, Shane L. Larson

Public Talks

No abstract provided.

The Acs Survey Of Galactic Globular Clusters. Vii. Relative Ages, Antonio Marín-Franch, Antonio Aparicio, Giampaolo Piotto, Alfred Rosenberg, Brian Chaboyer

Dartmouth Scholarship

The ACS Survey of Galactic globular clusters is a Hubble Space Telescope Treasury program designed to provide a new large, deep, and homogeneous photometric database. Based on observations from this program, we have measured precise relative ages for a sample of 64 Galactic globular clusters by comparing the relative position of the clusters' main-sequence (MS) turnoffs, using MS fitting to cross-compare clusters within the sample. This method provides relative ages to a formal precision of 2%-7%. We demonstrate that the calculated relative ages are independent of the choice of theoretical model. We find that the Galactic globular cluster sample can …

The Acs Survey Of Galactic Globular Clusters. Iii. The Double Subgiant Branch Of Ngc 1851, A. P. Milone, L. R. Bedin, G. Piotto, J. Anderson, I. R. King, A. Sarajedini, A. Dotter, B. Chaboyer, A. Marin Franch, S. Majewski, A. Aparicio, M. Hempel, N. E.Q Paust, I. N. Reid, A. Rosenberg, M. Siegel

Dartmouth Scholarship

Photometry with the Hubble Space Telescope Advanced Camera for Surveys (HST ACS) reveals that the subgiant branch (SGB) of the globular cluster NGC 1851 splits into two well-defined branches. If the split is due only to an age effect, the two SGBs would imply two star formation episodes separated by ~1 Gyr. We discuss other anomalies in NGC 1851 that could be interpreted in terms of a double stellar population. Finally, we compare the case of NGC 1851 with the other two globulars known to host multiple stellar populations, and show that all three clusters differ in several important …

Songs From The Milky Way: Our Galaxy In Low Frequency Gravitational Waves, Shane L. Larson

Colloquia and Seminars

No abstract provided.

Dark Side Of The Universe: Dark Matter In The Galaxy And Cosmos, Shane L. Larson

Public Talks

No abstract provided.

First Glimpse Results On The Stellar Structure Of The Galaxy., R. Benjamin, E. Churchwell, B. Babler, R. Indebetouw, M. Meade, B. Whitney, C. Watson, M. Wolfire, M. Wolff, Richard Ignace, T. Bania, S. Bracker, D. Clemens, L. Chomiuk, M. Cohen, J. Dickey, J. Jackson, H. Kobulnicky, E. Mercer, J. Mathis, S. Stolovy, B. Uzpen

ETSU Faculty Works

The GLIMPSE (Galactic Legacy Mid-Plane Survey Extraordinaire) Point Source Catalog of ~ 30 million mid-infrared sources towards the inner Galaxy, 10 < |l| < 65 degrees and |b| < 1 degree, was used to determine the distribution of stars in Galactic longitude, latitude, and apparent magnitude. The counts versus longitude can be approximated by the modified Bessel function N=N_0*(l/l_0)*K_1(l/l_0), where l_0 is insensitive to limiting magnitude, band choice, and side of Galactic center: l_0= 17-30 degrees with a best fit value in the the 4.5 micron band of l_0=24 +/- 4 degrees. Modeling the source distribution as an exponential disk yields a radial scale length of H= 3.9 +/- 0.6 kpc. There is a pronounced north-south asymmetry in source counts for |l| < 30 degrees, with ~ 25% more stars in the north. For l=10-30 degrees, there is a strong enhancement of stars of m= 11.5-13.5 mag. A linear bar passing through the Galactic center with half-length R_bar=4.4 +/- 0.5 kpc, tilted by phi=44 +/- 10 degrees to the Sun-Galactic Center line, provides the simplest interpretation of this data. We examine the possibility that enhanced source counts at l=26-28 degrees, 31.5-34 degrees, and 306-309 degrees are related to Galactic spiral structure. Total source counts are depressed in regions where the counts of red objects (m_K-m_[8.0] >3) peak. In these areas, the counts are reduced by extinction due to molecular gas and/or high diffuse backgrounds associated with star formation.

X-Ray Variability During The Quiescent State Of The Neutron Star X-Ray Transient In The Globular Cluster Ngc 6440, Edward M. Cackett, Rudy Wijnands, Craig O. Heinke, Peter D. Edmonds, Walter H. G. Lewin, David Pooley, Jonathan E. Grindlay, Peter G. Jonker, Jon M. Miller

Physics and Astronomy Faculty Research Publications

The globular cluster NGC 6440 is known to harbor a bright neutron star X-ray transient. We observed the globular cluster with Chandra on two occasions when the bright transient was in its quiescent state, in 2000 July and 2003 June (both observations were made nearly 2 yr after the end of their preceding outbursts). The quiescent spectrum during the first observation is well represented by a two-component model (a neutron star atmosphere model plus a power-law component that dominates at energies above 2 keV). During the second observation (which was roughly of equal duration to the first observation) we found …

New Nonthermal Filaments At The Galactic Center: Are They Tracing A Globally Ordered Magnetic Field?, Ted La Rosa, Michael E. Nord, Joseph W. Lazlo, Namir E. Kassim

Faculty and Research Publications

New high-resolution, wide-field 90 cm VLA observations of the Galactic center (GC) region by Nord and coworkers have revealed 20 nonthermal filament (NTF) candidates. We report 6 cm polarization observations of six of these. All of the candidates have the expected NTF morphology, and two show extended polarization, confirming their identification as NTFs. One of the new NTFs appears to be part of a system of NTFs located in the Sgr B region, 64 pc in projection north of Sgr A. These filaments cross the Galactic plane with an orientation similar to the filaments in the Galactic center radio arc. …

A New System Of Parallel Isolated Nonthermal Filaments Near The Galactic Center: Evidence For A Local Magnetic Field Gradient, Ted N. La Rosa, Joseph W. Lazio, Nasir E. Kassim

Faculty and Research Publications

We report the discovery of a system of isolated nonthermal filaments approximately 0fdg5 northwest (75 pc in projection) of Sgr A. Unlike other isolated nonthermal filaments which show subfilamentation, braiding of subfilaments, and flaring at their ends, these filaments are simple linear structures and more closely resemble the parallel bundled filaments in the Galactic center radio arc. However, the most unusual feature of these filaments is that the 20/90 cm spectral index uniformly decreases as a function of length, in contrast to all other nonthermal filaments in the Galactic center. This spectral gradient may not be due to simple particle …

A Search For Previously Unrecognized Metal-Poor Subdwarfs In The Hipparcos Astrometric Catalogue, I. N. Reid, F. Van Wyk, F. Marang, G. Roberts, D. Kilkenny, S. Mahoney

Dartmouth Scholarship

We have identified 317 stars included in the Hipparcos astrometric catalogue that have parallaxes measured to a precision of better than 15 per cent, and the location of which in the (M_V,(B−V)_T) diagram implies a metallicity comparable to or less than that of the intermediate‐abundance globular cluster M5. We have undertaken an extensive literature search to locate Strömgren, Johnson/Cousins and Walraven photometry for over 120 stars. In addition, we present new UBV(RI)_C photometry of 201 of these candidate halo stars, together with similar data for a further 14 known metal‐poor subdwarfs. These …