Physical Sciences and Mathematics Commons^™

On The Impact Of Inclination-Dependent Attenuation On The Derived Star Formation Histories Of Disk Galaxies, Keith Doore

Graduate Theses and Dissertations

The physical properties of a galaxy (e.g., its star-formation history and dust content) regulate the distribution of light that is emitted by stars and attenuated by the interstellar gas and dust. This attenuation by dust can have a significant impact on the observed spectral energy distribution (SED) of a disk galaxy, especially when taking into account its viewing angle (i.e., inclination). For example, as the inclination angle of a galactic disk changes from face-on to edge-on (i.e., i = 0 deg to i = 90 deg), the proportion of light that is attenuated along the line of sight increases, due …

Galaxy And Mass Assembly (Gama): Low-Redshift Quasars And Inactive Galaxies Have Similar Neighbors, Maria B. Stone, Clare F. Wethers, Roberto De Propris, Jari Kotilainen, Nischal Acharya, Benne W. Holwerda, Jonathan Loveday, Steven Phillipps

Faculty Scholarship

We explore the properties of galaxies in the proximity (within a ∼2 Mpc radius sphere) of Type I quasars at 0.1 <z <0.35, to check whether and how an active galaxy influences the properties of its neighbors. We further compare these with the properties of neighbors around inactive galaxies of the same mass and redshift within the same volume of space, using the Galaxy and Mass Assembly spectroscopic survey. Our observations reveal no significant difference in properties such as the number of neighbors, morphologies, stellar mass, star formation rates, and star formation history between the neighbors of quasars and those of the comparison sample. This implies that quasar activity in a host galaxy does not significantly affect its neighbors (e.g., via interactions with the jets). Our results suggest that quasar host galaxies do not strongly differ from the average galaxy within the specified mass and redshift range. Additionally, the implication of the relatively minor importance of the environmental effect on and from quasars is that nuclear activity is more likely triggered by internal and secular processes.

How Do Galaxies Form Their Stars Over Cosmic Time?, Jed H. Mckinney

Doctoral Dissertations

Galaxies in the past were forming more stars than those today, but the driving force behind this increase in activity remains uncertain. In this thesis I explore the origin of high star-formation rates today and in the past by studying the properties of gas and dust in the cold interstellar medium (ISM) of dusty galaxies over cosmic time. Critically, we do not yet understand how these galaxies could form so many stars. This work began with my discovery of unusual infrared (IR) emission line ratios in the class of dusty galaxies where most of the Universe’s stars were formed. To …

Probing Galaxy Evolution Through Deep Radio Continuum Observations, Hansung Gim

Doctoral Dissertations

One of the most important questions in modern astrophysics is how galaxies form and evolve. There are numerous processes involved in galaxy evolution, but the stellar mass buildup and supermassive black hole growth are two main drivers in galaxy evolution. Those activities are heavily obscured by dust, so we need another tracer without dust attenuation: low-frequency radio continuum observation. We understand the galaxy evolution through the deep radio continuum observations on the Great Observatories Origins Deep Survey (GOODS)-North, -South, and the COSMOS HI Large Extragalactic Survey (CHILES) fields. Exploiting the multi-wavelength dataset, we define the radio populations such as star-formation …

The Clustering Of Young Stellar Clusters In Nearby Galaxies, Kathryn Grasha

Doctoral Dissertations

Star clusters form the basic building blocks of galaxies. They span a wide range of ages, from a few million years to billions of years, making them exceptional tracers of the star formation histories of their host galaxies. Star formation is the process by which galaxies build up their stellar populations and their visible mass and occurs in a continuous, hierarchical "social" fashion across a large dynamical range, from individual stars up to kiloparsec-scale ensembles of stellar aggregates. It is the formation, evolution, and eventual destruction of these large hierarchical star-forming complexes that provide an essential role in understanding the …

Ultraviolet To Infrared Star Formation Rate Tracers: Characterizing Dust Attenuation And Emission, Andrew Battisti

Doctoral Dissertations

Star formation rates (SFRs) are among the fundamental properties used to characterize galaxies during their evolution across cosmic times. In the first part of this dissertation, we calibrate continuous, monochromatic SFR indicators over the mid-infrared wavelength range of 6-70 micron. We use a sample of 58 local star-forming galaxies for which there is a rich suite of multi-wavelength photometry and spectroscopy from the ultraviolet through far-infrared. Our results indicate that our mid-infrared SFR indicators are applicable to galaxies over a large range of distances, proving their robustness. We have made the calibrations and diagnostics publicly available to achieve the broadest …

The Effect Of A Growing Black Hole On The Infrared Emission Of Dusty Galaxies In The Distant Universe, Allison Kirkpatrick

Doctoral Dissertations

The buildup of stellar and black hole mass peaked during z=1-3. Infrared (IR) luminous galaxies, which are massive and heavily dust obscured (L_IR > 10¹¹ L_sun), dominate the stellar growth during this era, and many are harboring a hidden active galactic nucleus (AGN). We have quantified the contribution of AGN heating to the infrared emission of a large sample of dusty, luminous galaxies from z=0.5-4 using Spitzer mid-IR spectroscopy, available for every source. We classify sources as star forming galaxies, AGN, or composites based on the presence of mid-IR continuum emission due to a dusty …

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 …

Topics In Galaxy Formation: Pairwise Velocities Of Dark Matter Halos And Molecular Hydrogen Regulated Star Formation In Cosmological Simulations, Robert Jo Thompson

UNLV Theses, Dissertations, Professional Papers, and Capstones

In this dissertation we investigate two distinct challenges within the concordance LCDM model and an unrelated project.

The first is a discrepancy between theory and observation. A massive galaxy sub-cluster known as the `bullet' has fallen through a more massive parent galaxy cluster at a redshift of z=0.296.

Theory finds that in order to reproduce the observational quantities of this cluster, an unusually high relative velocity of v12=3000 km/s between the two cluster's parent halos is required.

We quantify the statistical probability of producing a `bullet-like' halo pair within large N-body simulations, and

conclude that either the LCDM model is …

Energetic Galaxy-Wide Outflows In High-Redshift Ultraluminous Infrared Galaxies Hosting Agn Activity, C. M. Harrison, D. M. Alexander, A. M. Swinbank, Ian Smail, S. Alaghband-Zadeh, F. E. Bauer, S. C. Chapman, A. Del Moro, R. C. Hickox

Dartmouth Scholarship

We present integral field spectroscopy observations, covering the [O III]4959,5007 emission-line doublet of eight high-redshift (z=1.4-3.4) ultra-luminous infrared galaxies (ULIRGs) that host Active Galactic Nuclei (AGN) activity, including known sub-millimetre luminous galaxies (SMGs). The targets have moderate radio luminosities that are typical of high-redshift ULIRGs (L(1.4GHz)=10^(24)-10^(25)W/Hz) and therefore are not radio-loud AGN. We de-couple kinematic components due to the galaxy dynamics and mergers from those due to outflows. We find evidence in the four most luminous systems (L([O III])>~10^(43)erg/s) for the signatures of large-scale energetic outflows: extremely broad [O III] emission (FWHM ~ 700-1400km/s) across ~4-15kpc, with high velocity …

The Clustering Of Ha Emitters At Z=2.23 From Hizels, J. E. Geach, D. Sobral, R. C. Hickox, D. A. Wake

Dartmouth Scholarship

We present a clustering analysis of 370 high-confidence Hα emitters (HAEs) at z = 2.23. The HAEs are detected in the Hi-Z Emission Line Survey (HiZELS), a large-area blank field 2.121 μm narrow-band survey using the United Kingdom Infrared Telescope Wide Field Camera (WFCAM). Averaging the two-point correlation function of HAEs in two ∼1° scale fields [United Kingdom Infrared Deep Sky Survey/Ultra Deep Survey (UDS) and Cosmological Evolution Survey (COSMOS) fields] we find a clustering amplitude equivalent to a correlation length of r0 = 3.7 ± 0.3 h−1 Mpc for galaxies with star formation rates of ≳7 M⊙ yr−1. The …

Near Ultraviolet–Infrared Colours Of Red-Sequence Galaxies In Local Clusters, Timothy D. Rawle, Russell J. Smith, John R. Lucey, Michael J. Hudson, Gary A. Wegner

Dartmouth Scholarship

We present GALEX near‐ultraviolet (NUV) and Two‐Micron All‐Sky Survey J‐band photometry for red‐sequence galaxies in local clusters. We define quiescent samples according to a strict emission threshold, removing galaxies with very recent star formation. We analyse the NUV–J colour–magnitude relation (CMR) and find that the intrinsic scatter is an order of magnitude larger than for the analogous optical CMR (∼0.35 rather than 0.05 mag), in agreement with previous studies. Comparing the NUV–J colours with spectroscopically derived stellar population parameters, we find a strong (>5.5σ) correlation with metallicity, only a marginal trend with …

The Noao Fundamental Plane Survey - Iii. Variations In The Stellar Populations Of Red-Sequence Galaxies From The Cluster Core To The Virial Radius, Russell J. S. Smith, Michael J. Hudson, John R. Lucey, Jenica E. Nelan, Gary A. Wegner

Dartmouth Scholarship

We analyse absorption line-strength indices for ~3000 red-sequence galaxies in 94 nearby clusters, to investigate systematic variations of their stellar content with location in the host cluster. The data are drawn from the NOAO Fundamental Plane Survey. Our adopted method is a generalization of that introduced by Nelan et al. to determine the global age-mass and metallicity-mass relations from the same survey. We find strong evidence for a change in galaxy properties, at fixed mass, over a range from the cluster centre to the virial radius, R_200. For example, red-sequence galaxies further out in the clusters have weaker Mgb5177 (at …