Tracing Evolutionary Processes In Stellar Disks In Nearby Dwarf Galaxies From X-Ray Light,
2014
University of Alabama in Huntsville
Tracing Evolutionary Processes In Stellar Disks In Nearby Dwarf Galaxies From X-Ray Light, Sarthak Dasadia
Von Braun Symposium Student Posters
No abstract provided.
A Spectroscopic Survey Of Wise -Selected Obscured Quasars With The Southern African Large Telescope,
2014
Dartmouth College
A Spectroscopic Survey Of Wise -Selected Obscured Quasars With The Southern African Large Telescope, Kevin N. Hainline, Ryan C. Hickox, Christopher M. Carroll, Adam D. Myers
Dartmouth Scholarship
We present the results of an optical spectroscopic survey of a sample of 40 candidate obscured quasars identified on the basis of their mid-infrared emission detected by the Wide-Field Infrared Survey Explorer (WISE). Optical spectra for this survey were obtained using the Robert Stobie Spectrograph on the Southern African Large Telescope. Our sample was selected with WISE colors characteristic of active galactic nuclei (AGNs), as well as red optical to mid-IR colors indicating that the optical/UV AGN continuum is obscured by dust. We obtain secure redshifts for the majority of the objects that comprise our sample (35/40), and …
Constraints On Very High Energy Emission From Grb 130427a,
2014
Department of Physical Sciences, Cork Institute of Technology, Bishopstown, Cork, Ireland
Constraints On Very High Energy Emission From Grb 130427a, P. T. Reynolds, Et Al
Physical Sciences Publications
Prompt emission from the very fluent and nearby (z = 0.34) gamma-ray burst GRB 130427A was detected by several orbiting telescopes and by ground-based, wide-field-of-view optical transient monitors. Apart from the intensity and proximity of this GRB, it is exceptional due to the extremely long-lived high-energy (100 MeV to 100 GeV) gamma-ray emission, which was detected by the Large Area Telescope on the Fermi Gamma-Ray Space Telescope for ~70 ks after the initial burst. The persistent, hard-spectrum, high-energy emission suggests that the highest-energy gamma rays may have been produced via synchrotron self-Compton processes though there is also evidence that …
A Physically-Based Type Ii Supernova Feedback Model In Sph Simulations,
2014
University of Nevada, Las Vegas
A Physically-Based Type Ii Supernova Feedback Model In Sph Simulations, Keita Todoroki
UNLV Theses, Dissertations, Professional Papers, and Capstones
We implement and test a core-collapse Type II SN feedback that is physically motivated and produces good agreement with observations in galaxy formation simulations. The model includes both kinetic and thermal feedback, allowing wind particles to receive a velocity kick that mimics galactic winds and distributes mass and metallicity to the interstellar and intergalactic medium. We also include a phenomenological stellar feedback to study a possible enhancement of the efficiency of the SN-II feedback by creating lower-density ambient gas medium of the stellar populations by distribution of thermal energy. Our SN-II model is unique in the sense that it computes …
A Uv To Mid-Ir Study Of Agn Selection,
2014
The Ohio State University
A Uv To Mid-Ir Study Of Agn Selection, Sun Mi Chung, Christopher S. Kochanek, Roberto Assef, Michael J. I. Brown, Daniel Stern, Buell T. Jannuzi, Anthony H. Gonzalez, Ryan C. Hickox, John Moustakas
Dartmouth Scholarship
We classify the spectral energy distributions (SEDs) of 431,038 sources in the 9 deg2 Boötes field of the NOAO Deep Wide-Field Survey (NDWFS). There are up to 17 bands of data available per source, including ultraviolet (GALEX), optical (NDWFS), near-IR (NEWFIRM), and mid-infrared (IRAC and MIPS) data, as well as spectroscopic redshifts for ~20,000 objects, primarily from the AGN and Galaxy Evolution Survey. We fit galaxy, active galactic nucleus (AGN), stellar, and brown dwarf templates to the observed SEDs, which yield spectral classes for the Galactic sources and photometric redshifts and galaxy/AGN luminosities for the extragalactic sources. …
Early-Type Galaxies In The Chandra Cosmos Survey,
2014
Dartmouth College
Early-Type Galaxies In The Chandra Cosmos Survey, F. Civano, G. Fabbiano, S. Pellegrini, D.-W. Kim
Dartmouth Scholarship
We study a sample of 69 X-ray detected early-type galaxies (ETGs), selected from the Chandra COSMOS survey, to explore the relation between the X-ray luminosity of hot gaseous halos (L X, gas) and the integrated stellar luminosity (LK ) of the galaxies, in a range of redshift extending out to z = 1.5. In the local universe, a tight, steep relationship has been established between these two quantities, suggesting the presence of largely virialized halos in X-ray luminous systems. We use well-established relations from the study of local universe ETGs, together with the expected evolution …
Obscuration By Gas And Dust In Luminous Quasars,
2014
Johns Hopkins University
Obscuration By Gas And Dust In Luminous Quasars, S. M. Usman, S. S. Murray, R. C. Hickox, M. Brodwin
Dartmouth Scholarship
We explore the connection between absorption by neutral gas and extinction by dust in mid-infrared (IR) selected luminous quasars. We use a sample of 33 quasars at redshifts 0.7 < z < 3 in the 9 deg^2 Bo\"otes multiwavelength survey field that are selected using Spitzer Space Telescope Infrared Array Camera colors and are well-detected as luminous X-ray sources (with >150 counts) in Chandra observations. We divide the quasars into dust-obscured and unobscured samples based on their optical to mid-IR color, and measure the neutral hydrogen column density N_H through fitting of the X-ray spectra. We find that all subsets of quasars have consistent power law photon indices equal to 1.9 that are uncorrelated with N_H. We classify the quasars as gas-absorbed or gas-unabsorbed if N_H > 10^22 cm^-2 or N_H < 10^22 cm^-2, respectively. Of 24 dust-unobscured quasars in the sample, only one shows clear evidence for significant intrinsic N_H, while 22 have column densities consistent with N_H < 10^22 cm^-2. In contrast, of the nine dust-obscured quasars, six show evidence for intrinsic gas absorption, and three are consistent with N_H < 10^22 cm^-2. We conclude that dust extinction in IR-selected quasars is strongly correlated with significant gas absorption as determined through X-ray spectral fitting. These results suggest that obscuring gas and dust in quasars are generally co-spatial, and confirm the reliability of simple mid-IR and optical photometric techniques for separating quasars based on obscuration.
Test Of Models Of The Cosmic Infrared Background With Multiwavelength Observations Of The Blazar 1es 1218+30.4 In 2009,
2014
Department of Physical Sciences, Cork Institute of Technology, Bishopstown, Cork, Ireland
Test Of Models Of The Cosmic Infrared Background With Multiwavelength Observations Of The Blazar 1es 1218+30.4 In 2009, P. T. Reynolds
Physical Sciences Publications
We present the results of a multi-wavelength campaign targeting the blazar 1ES 1218+30.4 with observations with the 1.3 m McGraw-Hill optical telescope, the Rossi X-ray Timing Explorer (RXTE), the Fermi Gamma-Ray Space Telescope, and the Very Energetic Radiation Imaging Telescope Array System (VERITAS). The RXTE and VERITAS observations were spread over a 13 day period and revealed clear evidence for flux variability, and a strong X-ray and γ-ray flare on 2009 February 26 (MJD 54888). The campaign delivered a well-sampled broadband energy spectrum with simultaneous RXTE and VERITAS very high energy (VHE, >100 GeV) observations, as well as …
The Angular Clustering Of Infrared-Selected Obscured And Unobscured Quasars,
2014
University of Wyoming
The Angular Clustering Of Infrared-Selected Obscured And Unobscured Quasars, M. A. Dipompeo, A. D. Myers, R. C. Hickox, J. E. Geach, K. N. Hainline
Dartmouth Scholarship
Recent studies of luminous infrared-selected active galactic nuclei (AGN) suggest that the reddest, most obscured objects display a higher angular clustering amplitude, and thus reside in higher-mass dark matter halos. This is a direct contradiction to the prediction of the simplest unification-by-orientation models of AGN and quasars. However, clustering measurements depend strongly on the "mask" that removes low-quality data and describes the sky and selection function. We find that applying a robust, conservative mask to WISE-selected quasars yields a weaker but still significant difference in the bias between obscured and unobscured quasars. These findings are consistent with results from previous …
Gemini Long-Slit Observations Of Luminous Obscured Quasars: Further Evidence For An Upper Limit On The Size Of The Narrow-Line Region,
2014
Dartmouth College
Gemini Long-Slit Observations Of Luminous Obscured Quasars: Further Evidence For An Upper Limit On The Size Of The Narrow-Line Region, Kevin N. Hainline, Ryan C. Hickox, Jenny E. Greene, Adam D. Myers
Dartmouth Scholarship
We examine the spatial extent of the narrow-line regions (NLRs) of a sample of 30 luminous obscured quasars at 0.4 < z < 0.7 observed with spatially resolved Gemini-N GMOS long-slit spectroscopy. Using the [O III] λ5007 emission feature, we estimate the size of the NLR using a cosmology-independent measurement: the radius where the surface brightness falls to 10–15 erg s–1 cm–2 arcsec–2. We then explore the effects of atmospheric seeing on NLR size measurements and conclude that direct measurements of the NLR size from observed profiles are too large by 0.1-0.2 dex on average, as compared to measurements made to best-fit Sérsic or Voigt profiles convolved with the seeing. These data, which span a full order of magnitude in IR luminosity (log (L 8 μm/erg s–1) = 44.4-45.4), …
The Catalog Of Edge-On Disk Galaxies From Sdss. I. The Catalog And The Structural Parameters Of Stellar Disks,
2014
Apache Point Observatory and New Mexico State University; Moscow State University
The Catalog Of Edge-On Disk Galaxies From Sdss. I. The Catalog And The Structural Parameters Of Stellar Disks, D. V. Bizyaev, Stefan Kautsch, A. V. Mosenkov, V. P. Reshetnikov, N. Ya. Sotnikova, N. V. Yablokova
Chemistry and Physics Faculty Articles
We present a catalog of true edge-on disk galaxies automatically selected from the Seventh Data Release of the Sloan Digital Sky Survey (SDSS). A visual inspection of the g, r, and iimages of about 15,000 galaxies allowed us to split the initial sample of edge-on galaxy candidates into 4768 (31.8% of the initial sample) genuine edge-on galaxies, 8350 (55.7%) non-edge-on galaxies, and 1865 (12.5%) edge-on galaxies not suitable for simple automatic analysis because these objects either show signs of interaction and warps, or nearby bright stars project on it. We added more candidate galaxies from RFGC, EFIGI, …
Galaxy Pairs In The Sloan Digital Sky Survey - Ix. Merger-Induced Agn Qctivity As Traced By The Wide-Field Infrared Survey Explorer,
2014
George Mason University
Galaxy Pairs In The Sloan Digital Sky Survey - Ix. Merger-Induced Agn Qctivity As Traced By The Wide-Field Infrared Survey Explorer, Shobita Satyapal, Sara L. Ellison, William Mcalpine, Ryan C. Hickox
Dartmouth Scholarship
Interactions between galaxies are predicted to cause gas inflows that can potentially trigger nuclear activity. Since the inflowing material can obscure the central regions of interacting galaxies, a potential limitation of previous optical studies is that obscured Active Galactic Nuclei (AGNs) can be missed at various stages along the merger sequence. We present the first large mid-infrared study of AGNs in mergers and galaxy pairs, in order to quantify the incidence of obscured AGNs triggered by interactions. The sample consists of galaxy pairs and post-mergers drawn from the Sloan Digital Sky Survey that are matched to detections by the Wide …
Massive Compact Galaxies With High-Velocity Outflows: Morphological Analysis And Constraints On Agn Activity,
2014
University of Wisconsin-Madison
Massive Compact Galaxies With High-Velocity Outflows: Morphological Analysis And Constraints On Agn Activity, P. H. Sell, C. A. Tremonti, R. C. Hickox, A. M. Diamond-Stanic
Dartmouth Scholarship
We investigate the process of rapid star formation quenching in a sample of 12 massive galaxies at intermediate redshift (z~0.6) that host high-velocity ionized gas outflows (v>1000 km/s). We conclude that these fast outflows are most likely driven by feedback from star formation rather than active galactic nuclei (AGN). We use multiwavelength survey and targeted observations of the galaxies to assess their star formation, AGN activity, and morphology. Common attributes include diffuse tidal features indicative of recent mergers accompanied by bright, unresolved cores with effective radii less than a few hundred parsecs. The galaxies are extraordinarily compact for their …
Deep Broadband Observations Of The Distant Gamma-Ray Blazar Pks 1424+240,
2014
Department of Physical Sciences, Cork Institute of Technology, Bishopstown, Cork, Ireland
Deep Broadband Observations Of The Distant Gamma-Ray Blazar Pks 1424+240, P. T. Reynolds, Et Al
Physical Sciences Publications
We present deep VERITAS observations of the blazar PKS 1424+240, along with contemporaneous Fermi Large Area Telescope, Swift X-ray Telescope, and Swift UV Optical Telescope data between 2009 February 19 and 2013 June 8. This blazar resides at a redshift of z ≥ 0.6035, displaying a significantly attenuated gamma-ray flux above 100 GeV due to photon absorption via pair-production with the extragalactic background light. We present more than 100 hr of VERITAS observations over three years, a multiwavelength light curve, and the contemporaneous spectral energy distributions. The source shows a higher flux of (2.1 ± 0.3) × 10–7 photons m–2 …
Weighing Obscured And Unobscured Quasar Hosts With The Cosmic Microwave Background,
2014
University of Wyoming
Weighing Obscured And Unobscured Quasar Hosts With The Cosmic Microwave Background, M. A. Dipompeo, A. D. Myers, R. C. Hickox, J. E. Geach, G. Holder, K. N. Hainline, S. W. Hall
Dartmouth Scholarship
We cross-correlate a cosmic microwave background (CMB) lensing map with the projected space densities of quasars to measure the bias and halo masses of a quasar sample split into obscured and unobscured populations, the first application of this method to distinct quasar subclasses. Several recent studies of the angular clustering of obscured quasars have shown that these objects likely reside in higher-mass halos compared to their unobscured counterparts. This has important implications for models of the structure and geometry of quasars, their role in growing supermassive black holes, and mutual quasar/host galaxy evolution. However, the magnitude and significance of this …
Star Formation And Substructure In Galaxy Clusters,
2014
Dartmouth College
Star Formation And Substructure In Galaxy Clusters, Seth A. Cohen, Ryan C. Hickox, Gary A. Wegner, Maret Einasto, Jaan Vennik
Dartmouth Scholarship
We investigate the relationship between star formation (SF) and substructure in a sample of 107 nearby galaxy clusters using data from the Sloan Digital Sky Survey (SDSS). Several past studies of individual galaxy clusters have suggested that cluster mergers enhance cluster SF, while others find no such relationship. The SF fraction in multi-component clusters (0.228 +/- 0.007) is higher than that in single-component clusters (0.175 +/- 0.016) for galaxies with M^0.1_r < -20.5. In both single- and multi-component clusters, the fraction of star-forming galaxies increases with clustercentric distance and decreases with local galaxy number density, and multi-component clusters show a higher SF fraction than single-component clusters at almost all clustercentric distances and local densities. Comparing the SF fraction in individual clusters to several statistical measures of substructure, we find weak, but in most cases significant at greater than 2 sigma, correlations between substructure and SF fraction. These results could indicate that cluster mergers may cause weak but significant SF enhancement in clusters, or unrelaxed clusters exhibit slightly stronger SF due to their less evolved states relative to relaxed clusters.
Tracing The Evolution Of Active Galactic Nuclei Host Galaxies Over The Last 9 Gyr Of Cosmic Time,
2014
Harvard-Smithsonian Center for Astrophysics
Tracing The Evolution Of Active Galactic Nuclei Host Galaxies Over The Last 9 Gyr Of Cosmic Time, A. D. Goulding, W. R. Forman, R. C. Hickox, C. Jones
Dartmouth Scholarship
We present the results of a combined galaxy population analysis for the host galaxies of active galactic nuclei (AGN) identified at 0 < z < 1.4 within the Sloan Digital Sky Survey, Boötes, and DEEP2 surveys. We identified AGN in a uniform and unbiased manner at X-ray, infrared, and radio wavelengths. Supermassive black holes undergoing radiatively efficient accretion (detected as X-ray and/or infrared AGN) appear to be hosted in a separate and distinct galaxy population than AGN undergoing powerful mechanically dominated accretion (radio AGN). Consistent with some previous studies, radiatively efficient AGN appear to be preferentially hosted in modest star-forming galaxies, with little dependence on AGN or galaxy luminosity. AGN exhibiting radio-emitting jets due to mechanically dominated accretion are almost exclusively observed in massive, passive galaxies. Crucially, we now provide strong evidence that the observed host-galaxy trends are independent of redshift. In particular, these different accretion-mode AGN have remained as separate galaxy populations throughout the last 9 Gyr. Furthermore, it appears that galaxies hosting AGN have evolved along the same path as galaxies that are not hosting AGN with little evidence for distinctly separate evolution.
Black Hole Variability And The Star Formation-Active Galactic Nucleus Connection: Do All Star-Forming Galaxies Host An Active Galactic Nucleus?,
2014
Dartmouth College
Black Hole Variability And The Star Formation-Active Galactic Nucleus Connection: Do All Star-Forming Galaxies Host An Active Galactic Nucleus?, Ryan C. Hickox, James R. Mullaney, David M. Alexander, Chien-Ting J. Chen, Francesca M. Civano, Andy D. Goulding, Kevin N. Hainline
Dartmouth Scholarship
We investigate the effect of active galactic nucleus (AGN) variability on the observed connection between star formation and black hole accretion in extragalactic surveys. Recent studies have reported relatively weak correlations between observed AGN luminosities and the properties of AGN hosts, which has been interpreted to imply that there is no direct connection between AGN activity and star formation. However, AGNs may be expected to vary significantly on a wide range of timescales (from hours to Myr) that are far shorter than the typical timescale for star formation (100 Myr). This variability can have important consequences for observed correlations. We …
Dynamical Models Of Elliptical Galaxies – I. Simple Methods,
2014
University of Cambridge
Dynamical Models Of Elliptical Galaxies – I. Simple Methods, A. Angello, N. Evans, Aaron Romanowsky
Faculty Publications
We study dynamical models for elliptical galaxies, deriving the projected kinematic profiles in a form that is valid for general surface-brightness profiles and (spherical) total mass profiles, without the need for any explicit deprojection. We then show that an almost flat rotation curve, combined with modest velocity anisotropy, is already sufficient to recover the kinematic profiles of nearby ellipticals. As an application, we provide two different sets of mass estimators for elliptical galaxies, based on either the velocity dispersion at a specific location near the effective radius, or the aperture-averaged velocity dispersion. In the large aperture (virial) limit, mass estimators …
Proceedings Of The First International Conference On Superluminal Physics & Instantaneous Physics As New Fields Of Research,
2014
University of New Mexico
Proceedings Of The First International Conference On Superluminal Physics & Instantaneous Physics As New Fields Of Research, Florentin Smarandache
Branch Mathematics and Statistics Faculty and Staff Publications
In a similar way as passing from Euclidean Geometry to Non-Euclidean Geometry, we can pass from Subluminal Physics to Superluminal Physics, and further to Instantaneous Physics (instantaneous traveling). In the lights of two consecutive successful CERN experiments with superluminal particles in the fall of 2011, we believe these two new fields of research should begin developing. A physical law has a form in Newtonian physics, another form in the Relativity Theory, and different form at Superluminal theory, or at Instantaneous (infinite) speeds – according to the S-Denying Theory spectrum. First, we extend physical laws and formulas to superluminal traveling and …
