External Galaxies Commons^™

Detection Of Baryonic Acoustic Oscillations In The Matter Power Spectrum, Spencer Everett, Ian Johnson, Jon Murphy, Mary Tarpley

DePaul Discoveries

Using the spectra of 22,923 high-redshift quasars from the Baryon Oscillation Spectrosocpic Survey (BOSS) subset of the Sloan Digital Sky Survey (SDSS), the authors detect evidence of the primordial baryonic acoustic oscillations (BAOs) in the matter power spectrum. The detection further endorses the currently accepted Lambda-CDM model of cosmology based upon the existence of dark energy (Lambda) and cold dark matter (CDM). Additionally, the use of the continuous wavelet transform to calculate the power spectrum has many advantages over traditional Fourier methods and independently corroborates previous detections.

Galaxy Pairs In The Sloan Digital Sky Survey - Xii. The Fuelling Mechanism Of Low-Excitation Radio-Loud Agn, Sara L. Ellison, David R. Patton, Ryan C. Hickox

Dartmouth Scholarship

We investigate whether the fuelling of low-excitation radio galaxies (LERGs) is linked to major galaxy interactions. Our study utilizes a sample of 10 800 spectroscopic galaxy pairs and 97 post-mergers selected from the Sloan Digital Sky Survey with matches to multiwavelength data sets. The LERG fraction amongst interacting galaxies is a factor of 3.5 higher than that of a control sample matched in local galaxy density, redshift and stellar mass. However, the LERG excess in pairs does not depend on projected separation and remains elevated out to at least 500 h70−1" role="presentation">h−170

kpc, suggesting that major mergers are not …

The Role Of Cold Gas In Low-Level Supermassive Black Hole Activity, Erik D. Alfvin

Macalester Journal of Physics and Astronomy

The nature of the relationship between low-level supermassive black hole activity and galactic cold gas, if any, is currently unclear. It has been hypothesized that feedback may heat or expel gas and quench star formation; alternatively, central black holes may feed at higher rates (either directly or as a secondary effect from stellar winds) in gas-rich galaxies. We use a combination of radio data from the on-going ALFALFA survey and from the literature, along with archival X-ray flux measurements from the Chandra X-ray observatory, to investigate this potential relationship. We construct a sample of 136 late-type galaxies, with MB < −18 out to 50 Mpc, that have both HI masses and sensitive X-ray coverage. Of these, 76 host a nuclear X-ray source, a 56% detection fraction. There is a highly significant correlation between LX and Mstar with a slope of 1.5±0.2, and a tentative correlation (significant at the 2.5σ level) between LX and MHI. However, a joint fit to LX as a function of both Mstar and MHI finds no significant dependence on MHI, and similarly the residuals of LX − LX(Mstar) show no trend with MHI. We conclude that the galaxy-wide cold gas content in these spirals does not strongly influence their low-level supermassive black hole activity.

How Elevated Is The Dynamical-To-Stellar Mass Ratio Of The Ultracompact Dwarf S999?, Joachim Janz, Duncan Forbes, Mark Norris, Jay Strader, Samantha Penny, Martina Fagioli, Aaron Romanowsky

Faculty Publications

No abstract provided.

Population Dynamics In Active Galactic Nuclei, Jon Bessler

Graduate Theses and Dissertations

The goal of this thesis is to present an approach to understanding the dynamics that govern the evolution of active galactic nuclei (AGN) in general, and those associated with spiral galaxies in particular. This approach starts with the continuity equation governing the mass function for a population of supermassive black holes (SMBHs). This approach is then extended to the luminosity function for AGN. Where the dynamical parameters that govern accretion are fairly well known, those values are adopted. The values that are not as well known are constrained by comparing evolved luminosity functions with observed luminosity functions. Boundary conditions for …

Logarithmic Spiral Arm Pitch Angle Of Spiral Galaxies: Measurement And Relationship To Galactic Structure And Nuclear Supermassive Black Hole Mass, Benjamin Lee Davis

Graduate Theses and Dissertations

In this dissertation, I explore the geometric structure of spiral galaxies and how the visible structure can provide information about the central mass of a galaxy, the density of its galactic disk, and the hidden mass of the supermassive black hole in its nucleus. In order to quantitatively measure the logarithmic spiral pitch angle (a measurement of tightness of the winding) of galactic spiral arms, I led an effort in our research group (the Arkansas Galaxy Evolution Survey) to modify existing two-dimensional fast Fourier transform software to increase its efficacy and accuracy. Using this software, I was able to lead …

Vegas-Sss. A Vst Early-Type Galaxy Survey: Analysis Of Small Stellar Systems: Testing The Methodology On The Globular Cluster System In Ngc 3115⋆, Michele Cantiello, Massimo Capaccioli, Nicola Napolitano, Aniello Grado, Luca Limatola, Maurizio Paolillo, Enrica Iodice, Aaron Romanowsky, Duncan Forbes, Gabriella Raimondo, Marilena Spavone, Francesco La Barbera, Thomas Puzia, Pietro Schipani

Faculty Publications

We present a study of globular clusters (GCs) and other small stellar systems (SSSs) in the field of NGC 3115, observed as part of the ongoing wide-field imaging survey VEGAS, carried out with the 2.6 m VST telescope. We used deep g and i observations of NGC 3115, a well-studied lenticular galaxy that is covered excellently well in the scientific literature. This is fundamental to test the methodologies, verify the results, and probe the capabilities of the VEGAS-SSS. Leveraging the large field of view of the VST allowed us to accurately study the distribution and properties of SSSs as a …

Supermassive Black Hole Scaling Relations, Ismaeel Abdulla Akhlite Al-Baidhany

Theses and Dissertations

In this dissertation, the determination of the masses of supermassive black holes (SMBHs) and the properties of their host spiral galaxies are focused for the purposes of constraining scaling relations and with the aim of understanding the role of SMBHs in the evolution of galaxies. The several techniques in this work as summarized are focused on in Chapter 2. Direct techniques (reverberation mapping, stellar and gas dynamics, maser modeling) and indirect techniques (the SMBH mass versus stellar/gas velocity dispersion relation and the SMBH mass versus spiral arm pitch angle relation) have been used to estimate SMBH masses. Then the measurement …

Determination Of Resonance Locations In Barred Spiral Galaxies, Amber Sierra

Theses and Dissertations

We applied a method identified by Puerari & Dottori (1997) to find the corotation radii of 57 galaxies. This entailed taking Fourier transforms along radial cuts in the u, g, r, i, and z wavebands and comparing the phase angles as a function of radius between them. The radius at which the phase angles cross indicates the location of the corotation radius. We then calculated the relative bar pattern speed, R and classified the bar as fast, less than 1.4, or slow, greater than or equal to 1.4. Finally, we found that our results were consistent with previously determined values …

A Connection Between Obscuration And Star Formation In Luminous Quasars, Chien-Ting J. Chen, Ryan C. Hickox, Stacey Alberts, Chris M. Harrison

Dartmouth Scholarship

We present a measurement of the star formation properties of a uniform sample of mid-IR selected, unobscured and obscured quasars (QSO1s and QSO2s) in the Bo\"otes survey region. We use an spectral energy distribution (SED) analysis for photometric data spanning optical to far-IR wavelengths to decompose AGN and host galaxy components. We find that when compared to a matched sample of QSO1s, the QSO2s have higher far-IR detection fractions, far-IR fluxes and infrared star formation luminosities (L^SF_IR) by a factor of ∼2. Correspondingly, we show that the AGN obscured fraction rises from 0.3 to 0.7 between 4−40×10 …

Spectroscopic Confirmation Of An Ultramassive And Compact Galaxy At Z = 3.35: A Detailed Look At An Early Progenitor Of Local Giant Ellipticals, Z. Cemile Marsan, Danilo Marchesini, Gabriel B. Brammer, Mauro Stefanon, Adam Muzzin, Alberto Fernández-Soto, Stefan Geier, Kevin N. Hainline

Dartmouth Scholarship

We present the first spectroscopic confirmation of an ultra-massive galaxy at redshift z>3 using data from Keck-NIRSPEC, VLT-Xshooter, and GTC-Osiris. We detect strong [OIII] and Lyα emission, and weak [OII], CIV, and HeII, placing C1-23152 at a spectroscopic redshift of zspec=3.351. The modeling of the emission-line corrected spectral energy distribution results in a best-fit stellar mass of M∗=3.1+0.6−0.7×1011M⊙, a star-formation rate of <7 M⊙yr−1, and negligible dust extinction. The stars appear to have formed in a short intense burst ~300-500 Myr prior to the observation epoch, setting the formation redshift of this galaxy at z~4.1. From the analysis of the line ratios and widths, and the observed flux at 24μm, we confirm the presence of a luminous hidden active galactic nucleus (AGN), with bolometric luminosity of ~1046ergs−1. Potential contamination to the observed SED from the AGN continuum is constrained, placing a lower limit on the stellar mass of 2×1011M⊙. HST/WFC3 H160 and ACS I814 images are modeled, resulting in an effective radius of re~1 kpc in the H160 band and a Sersic index n~4.4. This object may be a prototype of the progenitors of local most massive elliptical galaxies in the first 2 Gyr of cosmic history, having formed most of its stars at z>4 in a highly dissipative, intense, and short burst of star formation. C1-23152 is completing its transition to a post-starburst phase while hosting a powerful AGN, potentially responsible for the quenching of the star formation activity.

Detection Of A Distinct Metal-Poor Stellar Halo In The Early-Type Galaxy Ngc 3115*, Mark Peacock, Jay Strader, Aaron Romanowsky, Jean Brodie

Faculty Publications

We present the resolved stellar populations in the inner and outer halo of the nearby lenticular galaxy NGC 3115. Using deep Hubble Space Telescope observations, we analyze stars 2 mag fainter than the tip of the red giant branch (TRGB). We study three fields along the minor axis of this galaxy, 19, 37, and 54 kpc from its center—corresponding to 7, 14, and 21 effective radii (re ). Even at these large galactocentric distances, all of the fields are dominated by a relatively enriched population, with the main peak in the metallicity distribution decreasing with radius from [Z/H] ~ –0.5 …

The Sluggs Survey: Globular Cluster Stellar Population Trends From Weak Absorption Lines In Stacked Spectra, Christopher Usher, Duncan Forbes, Jean Brodie, Aaron Romanowsky, Jay Strader, Charlie Conroy, Caroline Foster, Nicola Pastorello, Vincenzo Pota, Jacob Arnold

Faculty Publications

As part of the SAGES Legacy Unifying Globulars and GalaxieS (SLUGGS) survey, we stack 1137 Keck DEIMOS (Deep Imaging Multi-Object Spectrograph) spectra of globular clusters from 10 galaxies to study their stellar populations in detail. The stacked spectra have median signal-to-noise ratios of ∼90 Å−1. Besides the calcium triplet, we study weaker sodium, magnesium, titanium and iron lines as well as the Hα and higher order Paschen hydrogen lines. In general, the stacked spectra are consistent with old ages and a Milky Way-like initial mass function. However, we see different metal line index strengths at fixed colour and magnitude, and …

Ngc 3628-Ucd1: A Possible Ω Cen Analog Embedded In A Stellar Stream, Zachary Jennings, Aaron Romanowsky, Jean Brodie, Joachim Janz, Mark Norris, Duncan Forbes, David Martinez-Delgado, Martina Fagioli, Samantha Penny

Faculty Publications

No abstract provided.

Small Scatter And Nearly Isothermal Mass Profiles To Four Half-Light Radii From Two-Dimensional Stellar Dynamics Of Early-Type Galaxies, Michele Cappellari, Aaron Romanowsky, Jean Brodie, Duncan Forbes, Jay Strader, Caroline Foster, Sreeja Kartha, Nicola Pastorello, Vincenzo Pota, Lee Spitler, Christopher Usher, Jacob Arnold

Faculty Publications

No abstract provided.

Hiding In Plain Sight: Record-Breaking Compact Stellar Systems In The Sloan Digital Sky Survey, Michael Sandoval, Richard Vo, Aaron Romanowsky, Jay Strader, Jieun Choi, Zachary Jennings, Charlie Conroy, Jean Brodie, Caroline Foster, Alexa Villaume, Mark Norris, Joachim Janz, Duncan Forbes

Faculty Publications

No abstract provided.

Evidence Of Attenuation Of Vhe Blazar Spectra By Extragalactic Background Light, Cameron Allen

Physics

The spectrum of two blazar objects, 1ES 1959+650 and 1ES 2344+514, are analyzed for evidence of interactions with the Extragalactic Background Light (EBL), using combined data from the Very Energetic Radiation Imaging Telescope Array System and the Fermi Gamma-ray Space Telescope, By analyzing the distinct curvature across the combined spectrum, we infer that the very-high energy (VHE) gamma-rays must be attenuated by interactions with the EBL. We also find that the measured 1ES 1959+650 spectrum is sensitive to the intrinsic blazar model, with a preference for a power-law with an exponential cutoff (EPWL). The measured curvature is a combination of …

Unmatter Plasma, Relativistic Oblique-Length Contraction Factor, Neutrosophic Diagram And Neutrosophic Degree Of Paradoxicity: Articles And Notes, Florentin Smarandache

Branch Mathematics and Statistics Faculty and Staff Publications

This book has four parts. In the first part, we collected five recent papers, published before in Progress in Physics, but reviewed. In the first paper, we approach a novel form of plasma, Unmatter Plasma. The electron-positron beam plasma was generated in the laboratory in the beginning of 2015. This experimental fact shows that unmatter, a new form of matter that is formed by matter and antimatter bind together (mathematically predicted a decade ago) really exists. That is the electron-positron plasma experiment of 2015 is the experimentum crucis verifying the mathematically predicted unmatter. In the second paper, we generalize the …

Spectroscopic Confirmation Of The Existence Of Large, Diffuse Galaxies In The Coma Cluster, Pieter Van Dokkum, Aaron Romanowsky, Roberto Abraham, Jean Brodie, Charlie Conroy, Marla Geha, Allison Merritt, Alexa Villaume, Jielai Zhang

Faculty Publications

No abstract provided.

The Double Galaxy Cluster Abell 2465 – Ii. Star Formation In The Cluster, Gary A. Wegner, Devin S. Chu, Ho Seong Hwang

Dartmouth Scholarship

We investigate the star formation rate and its location in the major merger cluster Abell 2465 at z = 0.245. Optical properties of the cluster are described in Paper I. Measurements of the Hα and infrared dust emission of galaxies in the cluster were made with an interference filter centred on the redshifted line at a wavelength of 817 nm and utilized data from the WISE satellite 12 μm band. Imaging in the Johnson U and B bands was obtained, and along with SDSS u and r was used to study the blue fraction, which appears enhanced, as a further …