Bulletin of the American Physical Society
Annual Meeting of the Four Corners Section of the APS
Volume 59, Number 11
Friday–Saturday, October 17–18, 2014; Orem, Utah
Session K5: Galaxies and Cosmology |
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Chair: Joseph Jensen, Utah Valley University Room: Science Building 260 |
Saturday, October 18, 2014 1:15PM - 1:39PM |
K5.00001: The Long Wavelength Array Invited Speaker: Greg Taylor The Long Wavelength Array (LWA) will be a new multi-purpose radio telescope operating in the frequency range 5-88 MHz with angular resolution of a few arcseconds. Scientific programs include exploration of the high-z universe, extrasolar planets, ionospheric physics and space weather. The LWA will consist of 50 stations that are each comprised of 256 pairs of crossed dipoles. The first station of the LWA, called LWA1, is located near the center of the Very Large Array (VLA) and has been operating since 2011 as a stand-alone instrument. The new LWA-OVRO station (located at the Owens Valley Radio Observatory) has been completed and a new station LWA-SV is under construction at the Sevilleta Wildlife Refuge just north of Socorro, NM. We have also developed basic station infrastructure and have 32 antennas at LWA-NA (located near the end of the VLA's North Arm). There may also be a possibility to combine these stations with the new, wide-band, low frequency capability on the VLA. I will discuss how these activities might be used to optimally design the LWA, and how we plan to carry out scientific observations every step on the way to the LWA. As an example of this philosophy I will present a number of scientific results obtained from LWA1. [Preview Abstract] |
Saturday, October 18, 2014 1:39PM - 1:51PM |
K5.00002: Assessing the H$_2$O and OH Megamaser Connection: H$_2$O Megamasers in OH Megamaser Hosts Brandon Wiggins, Victor Migenes Through megamasers are used to probe extragalactic phenomenon, questions continue to surround their production and connection to galactic processes. The observation that water and hydroxyl megamasers rarely coexist in the same galaxy has given rise to the hypothesis that the two megamaser species appear in different phases of nuclear activity. However, simultaneous hydroxyl and water megamaser emission has recently been detected in IC694. Studies of this object are underway but, because many megamasers have not been surveyed for emission in the other molecule, it remains unclear whether IC694 occupies a narrow phase of galaxy evolution or whether the relationship between megamaser species and galactic processes is more complicated than previously believed. We present results from the first 70 hours of a systematic search with the Green Bank Telescope for additional objects hosting both megamaser species. We provide discussion on our findings and their implications for the current paradigm. [Preview Abstract] |
Saturday, October 18, 2014 1:51PM - 2:03PM |
K5.00003: Probing Stellar Populations in the Virgo and Fornax Clusters with Infrared Surface Brightness Fluctuations Zachary Gibson, Joseph Jensen We extracted surface brightness fluctuation magnitudes and colors from Hubble Space Telescope images for 16 elliptical galaxies as a function of radius. Our plots show the internal gradients in fluctuation magnitude and color for each galaxy. The near-IR SBF measurements help break the age-metallicity degeneracy present at optical wavelengths and reveal the presence of young stars in galaxies with known distances. We compare our SBF measurements to four new stellar population models. Since SBFs are sensitive to the brightest stars in a galaxy, SBFs provide a powerful way to test the models. Most of the galaxies follow lines of constant metallicity, with SBF and color gradients arising from age variations. Stellar population models lead to the conclusion that most of the dwarf galaxies have younger populations near their centers and nearly constant metallicities. While the models agree with these trends they disagree quite broadly on the quantitative side. These observations lead to the conclusion that bluer dwarf galaxies are not well-suited for precise SBF distance measurements because population variations between galaxies are large. More work is needed to determine if the bluest low-luminosity dwarf ellipticals are young or not. [Preview Abstract] |
Saturday, October 18, 2014 2:03PM - 2:15PM |
K5.00004: The Surface Brightness Fluctuation Distance to the Coma Cluster Crystal-Lynn Bartier, Joseph Jensen With measuring accurate distances to nearby galaxies using surface brightness fluctuations (SBF), we can further our knowledge of the size, expansion rate, and age of the Universe. The Coma cluster is an important cluster for which there are several existing distance measurements, including a recent one using Cepheid variable stars in the spiral galaxy NGC 4921. Despite the fact that SBF analysis is not typically reliable for spiral galaxies, we were able to do SBF analysis on NGC 4921 using images gathered from the Space Telescope archive. Optical images in the I and r filters were cleaned and combined to make two separate images of NGC 4921. We also measured the SBF distance to the central giant elliptical galaxy NGC 4874 using Space Telescope infrared images. The result of this work was a SBF distance measurement that will help us calculate the distance to the Coma cluster and understand the properties of the stars in these galaxies. We then compare the Cepheid and SBF distances to the Coma cluster to yield a new measurement of the relative distance between the Virgo and Coma clusters. [Preview Abstract] |
Saturday, October 18, 2014 2:15PM - 2:27PM |
K5.00005: Tidal Dwarf Galaxies and the SMOC Carla Carroll, David Martinez-Delgado In a recent paper, Pavel Kroupa from the University of Bonn, Germany, attacked the Standard Model of Cosmology (SMoC) arguing that it demands that we see two distinct types of dwarf galaxies: dark matter galaxy satellites and tidal dwarf galaxies. All observed characteristics of dwarf galaxies suggest that only one type of dwarf galaxy actually exists: tidal dwarf galaxies. As the SMoC is the only currently accepted theory for cosmology, this puts great emphasis on enhancing our understanding of the properties of tidal dwarf galaxies. We present observational properties of several tidal dwarf galaxy candidates in two nearby interacting fields, NGC 3166/9 and NGC 7770/1 determined via photometric analysis as well as galaxy modelling. [Preview Abstract] |
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