Open Access. Powered by Scholars. Published by Universities.®
- Discipline
- Institution
-
- Dartmouth College (36)
- Wayne State University (20)
- Munster Technological University (10)
- University of Louisville (5)
- University of Richmond (4)
-
- Chapman University (3)
- University of Kentucky (3)
- Georgia Southern University (2)
- James Madison University (2)
- Old Dominion University (2)
- University of Arkansas, Fayetteville (2)
- West Virginia University (2)
- Cal Poly Humboldt (1)
- California Polytechnic State University, San Luis Obispo (1)
- City University of New York (CUNY) (1)
- Clemson University (1)
- Gettysburg College (1)
- Illinois Math and Science Academy (1)
- Southern Methodist University (1)
- University of Minnesota Morris Digital Well (1)
- University of New Mexico (1)
- Publication Year
- Publication
-
- Dartmouth Scholarship (36)
- Physics and Astronomy Faculty Research Publications (20)
- Physical Sciences Publications (10)
- Physics Faculty Publications (6)
- Faculty and Staff Scholarship (3)
-
- Mathematics, Physics, and Computer Science Faculty Articles and Research (3)
- Theses and Dissertations--Physics and Astronomy (3)
- Graduate Theses and Dissertations (2)
- Graduate Theses, Dissertations, and Problem Reports (ETD) (2)
- All Dissertations (1)
- College of Arts & Sciences Senior Theses (1)
- Dissertations, Theses, and Capstone Projects (1)
- Honors College Theses (1)
- IdeaFest: Interdisciplinary Journal of Creative Works and Research from Cal Poly Humboldt (1)
- Physics (1)
- Physics & Astronomy ETDs (1)
- Physics & Astronomy: Faculty Publications (1)
- Physics Theses and Dissertations (1)
- Physics and Astronomy Faculty Publications (1)
- Scholarly Horizons: University of Minnesota, Morris Undergraduate Journal (1)
- Senior Honors Projects, 2010-2019 (1)
- Senior Honors Projects, 2020-current (1)
- Student Publications & Research (1)
- The Cardinal Edge (1)
- Publication Type
Articles 61 - 90 of 100
Full-Text Articles in External Galaxies
Initial Calibration Of Ccd Images For The Dark Energy Survey, Deokgeun Park '12, H. Thomas Diehl, Douglas Tucker
Initial Calibration Of Ccd Images For The Dark Energy Survey, Deokgeun Park '12, H. Thomas Diehl, Douglas Tucker
Student Publications & Research
Astronomical images taken from a telescope must go through “astronomical image processing” to remove instrumental signatures. The Dark Energy Survey (DES), which will start operations in 2012, will use a 570 megapixel Dark Energy Camera (DECam) to study the mystery of the acceleration of the expanding universe. The DECam will use DES filters and 74 of a new type of astronomical Charge Coupled Device (CCD) that is particularly efficient in detecting near-infrared light. Together, the DES filters and DECam CCDs are optimized for the measurement of redshifts of distant galaxies. In preparation for the DES, data were collected from the …
Veritas Observations Of The Unusual Extragalactic Transient Swift J164449.3+573451, P. T. Reynolds, Et Al
Veritas Observations Of The Unusual Extragalactic Transient Swift J164449.3+573451, P. T. Reynolds, Et Al
Physical Sciences Publications
We report on very high energy (>100 GeV) gamma-ray observations of Swift J164449.3+573451, an unusual transient object first detected by the Swift Observatory and later detected by multiple radio, optical, and X-ray observatories. A total exposure of 28 hr was obtained on Swift J164449.3+573451 with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) during 2011 March 28-April 15. We do not detect the source and place a differential upper limit on the emission at 500 GeV during these observations of 1.4 × 10–12 erg cm–2 s–1 (99% confidence level). We also present time-resolved upper limits and use a …
Dynamical Masses Of Early-Type Galaxies: A Comparison To Lensing Results And Implications For The Stellar Initial Mass Function And The Distribution Of Dark Matter, J. Thomas, R. P. Saglia, R. Bender, D. Thomas, K. Gebhardt, J. Magorrian, E. M. Corsini, G. Wegner, S. Seitz
Dynamical Masses Of Early-Type Galaxies: A Comparison To Lensing Results And Implications For The Stellar Initial Mass Function And The Distribution Of Dark Matter, J. Thomas, R. P. Saglia, R. Bender, D. Thomas, K. Gebhardt, J. Magorrian, E. M. Corsini, G. Wegner, S. Seitz
Dartmouth Scholarship
This work aims to study the distribution of the luminous and dark matter in Coma early-type galaxies. Dynamical masses obtained under the assumption that mass follows light do not match with the masses of strong gravitational lens systems of similar velocity dispersions. Instead, dynamical fits with dark matter haloes are in good agreement with lensing results. We derive mass-to-light ratios of the stellar populations from Lick absorption line indices, reproducing well the observed galaxy colours. Even in dynamical models with dark matter haloes the amount of mass that follows the light increases more rapidly with the galaxy velocity dispersion than …
The Double Galaxy Cluster Abell 2465 - I. Basic Properties: Optical Imaging And Spectroscopy, Gary A. Wegner
The Double Galaxy Cluster Abell 2465 - I. Basic Properties: Optical Imaging And Spectroscopy, Gary A. Wegner
Dartmouth Scholarship
Optical imaging and spectroscopic observations of the z= 0.245 double galaxy cluster Abell 2465 are described. This object appears to be undergoing a major merger. It is a double X-ray source and is detected in the radio at 1.4 GHz. The purpose of this paper is to investigate signatures of the interaction of the two components. Redshifts were measured to determine velocity dispersions and virial radii of each component. The technique of fuzzy clustering was used to assign membership weights to the galaxies in each clump. Using redshifts of 93 cluster members within 1.4 Mpc of the subcluster centres, …
The Arcade 2 Instrument, Jack Singal, D. J. Fixsen, A. Kogut, S. Levin, M. Limon, P. Lubin, P. Mirel, M. Seiffert, T. Villela, E. Wollack, C. A. Wuensche
The Arcade 2 Instrument, Jack Singal, D. J. Fixsen, A. Kogut, S. Levin, M. Limon, P. Lubin, P. Mirel, M. Seiffert, T. Villela, E. Wollack, C. A. Wuensche
Physics Faculty Publications
The second generation Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission (ARCADE 2) instrument is a balloon-borne experiment to measure the radiometric temperature of the cosmic microwave background and Galactic and extragalactic emission at six frequencies from 3 to 90 GHz. ARCADE 2 utilizes a double-nulled design where emission from the sky is compared to that from an external cryogenic full-aperture blackbody calibrator by cryogenic switching radiometers containing internal blackbody reference loads. In order to further minimize sources of systematic error, ARCADE 2 features a cold fully open aperture with all radiometrically active components maintained at near 2.7 K without …
A Distinctive Disk-Jet Coupling In The Seyfert-1 Active Galactic Nucleus Ngc 4051, A. L. King, J. M. Miller, E. M. Cackett, A. C. Fabian, S. Markoff, M. A. Nowak, M. Rupen, K. Gültekin, M. T. Reynolds
A Distinctive Disk-Jet Coupling In The Seyfert-1 Active Galactic Nucleus Ngc 4051, A. L. King, J. M. Miller, E. M. Cackett, A. C. Fabian, S. Markoff, M. A. Nowak, M. Rupen, K. Gültekin, M. T. Reynolds
Physics and Astronomy Faculty Research Publications
We report on the results of a simultaneous monitoring campaign employing eight Chandra X-ray (0.5-10 keV) and six Very Large Array/Extended Very Large Array (8.4 GHz) radio observations of NGC 4051 over seven months. Evidence for compact jets is observed in the 8.4 GHz radio band; this builds on mounting evidence that jet production may be prevalent even in radio-quiet Seyferts. Assuming comparatively negligible local diffuse emission in the nucleus, the results also demonstrate an inverse correlation of L radio ∝ L -0.72±0.04 X-ray . If the A configuration is excluded in the case where diffuse emission plays a significant …
Colours Of Bulges And Discs Within Galaxy Clusters And The Signature Of Disc Fading On Infall, Michael J. Hudson, Jeffrey B. Stevenson, Russell J. Smith, Gary A. Wegner
Colours Of Bulges And Discs Within Galaxy Clusters And The Signature Of Disc Fading On Infall, Michael J. Hudson, Jeffrey B. Stevenson, Russell J. Smith, Gary A. Wegner
Dartmouth Scholarship
The origins of the bulge and disc components of galaxies are of primary importance to understanding galaxy formation. Here bulge–disc decomposition is performed simultaneously in B and R bands for 922 bright galaxies in eight nearby (z < 0.06) clusters with deep redshift coverage using photometry from the National Optical Astronomy Observatory (NOAO) Fundamental Plane Survey. The total galaxy colours follow a universal colour–magnitude relation (CMR). The discs of L* galaxies are 0.24 mag bluer in B−R than bulges. Bulges have a significant CMR slope while the CMR slope of discs is flat. Thus the slope of the CMR of the total light is driven primarily (60 per cent) by the bulge CMR, and to a lesser extent (40 per cent) by the change in the bulge‐to‐total ratio …
Stirring Up The Pot: Can Cooling Flows In Galaxy Clusters Be Quenched By Gas Sloshing?, J. A. A. Zuhone, M. Markevitch, R. E. Johnson
Stirring Up The Pot: Can Cooling Flows In Galaxy Clusters Be Quenched By Gas Sloshing?, J. A. A. Zuhone, M. Markevitch, R. E. Johnson
Dartmouth Scholarship
X-ray observations of clusters of galaxies reveal the presence of edges in surface brightness and temperature, known as "cold fronts." In relaxed clusters with cool cores, these commonly observed edges have been interpreted as evidence for the "sloshing" of the core gas in the cluster's gravitational potential. Such sloshing may provide a source of heat to the cluster core by mixing hot gas from the cluster outskirts with the cool-core gas. Using high-resolution N-body/Eulerian hydrodynamic simulations, we model gas sloshing in galaxy clusters initiated by mergers with subclusters. The simulations include merger scenarios with gas-filled and gasless subclusters. The …
The Discovery Of Gamma-Ray Emission From The Blazar Rgb J0710+591, P. T. Reynolds, Et Al
The Discovery Of Gamma-Ray Emission From The Blazar Rgb J0710+591, P. T. Reynolds, Et Al
Physical Sciences Publications
The high-frequency-peaked BL Lacertae object RGB J0710+591 was observed in the very high-energy (VHE; E > 100 GeV) wave band by the VERITAS array of atmospheric Cherenkov telescopes. The observations, taken between 2008 December and 2009 March and totaling 22.1 hr, yield the discovery of VHE gamma rays from the source. RGB J0710+591 is detected at a statistical significance of 5.5 standard deviations (5.5σ) above the background, corresponding to an integral flux of (3.9 ± 0.8) × 10–12 cm–2 s–1 (3% of the Crab Nebula's flux) above 300 GeV. The observed spectrum can be fit by a power law from 0.31 …
Core Gas Sloshing In Abell 1644, Ryan E. Johnson, Maxim Markevitch, Gary A. Wegner, Christine Jones, William R. Forman
Core Gas Sloshing In Abell 1644, Ryan E. Johnson, Maxim Markevitch, Gary A. Wegner, Christine Jones, William R. Forman
Dartmouth Scholarship
We present an analysis of a 72 ks Chandra observation of the double cluster Abell 1644 (z = 0.047). The X-ray temperatures indicate that the masses are M 500 = (2.6 ± 0.4) × 1014 h –1 M ☉ for the northern sub-cluster and M 500 = (3.1 ± 0.4) × 1014 h –1 M ☉ for the southern, main cluster. We identify a sharp edge in the radial X-ray surface brightness of the main cluster, which we find to be a cold front, with a jump in temperature of a factor of ~3. This edge possesses …
The Fundamental Plane Of Accretion Onto Black Holes With Dynamical Masses, Kayhan Gültekin, Edward M. Cackett, Jon M. Miller, Tiziana Di Matteo, Sera Markoff, Douglas O. Richstone
The Fundamental Plane Of Accretion Onto Black Holes With Dynamical Masses, Kayhan Gültekin, Edward M. Cackett, Jon M. Miller, Tiziana Di Matteo, Sera Markoff, Douglas O. Richstone
Physics and Astronomy Faculty Research Publications
Black hole accretion and jet production are areas of intensive study in astrophysics. Recent work has found a relation between radio luminosity, X-ray luminosity, and black hole mass. With the assumption that radio and X-ray luminosities are suitable proxies for jet power and accretion power, respectively, a broad fundamental connection between accretion and jet production is implied. In an effort to refine these links and enhance their power, we have explored the above relations exclusively among black holes with direct, dynamical mass-measurements. This approach not only eliminates systematic errors incurred through the use of secondary mass measurements, but also effectively …
Constraining The Spin Of The Black Hole In Fairall 9 With Suzaku, S. Schmoll, J. M. Miller, M. Volonteri, E. Cackett, C. S. Reynolds, A. C. Fabian, L. W. Brenneman, G. Miniutti, L. C. Gallo
Constraining The Spin Of The Black Hole In Fairall 9 With Suzaku, S. Schmoll, J. M. Miller, M. Volonteri, E. Cackett, C. S. Reynolds, A. C. Fabian, L. W. Brenneman, G. Miniutti, L. C. Gallo
Physics and Astronomy Faculty Research Publications
We report on the results of spectral fits made to data obtained from a 168 ks Suzaku observation of the Seyfert 1 galaxy Fairall 9. The source is clearly detected out to 30 keV. The observed spectrum is fairly simple; it is well described by a power law with soft excess and disk reflection. A broad iron line is detected, and easily separated from distinct narrow components owing to the resolution of the CCDs in the X-ray Imaging Spectrometer (XIS). The broad line is revealed to be asymmetric, consistent with a disk origin. We fit the XIS and Hard X-ray …
Long-Term Optical And X-Ray Variability Of The Seyfert Galaxy Markarian 79, E. Breedt, P. Arévalo, I. M. Mchardy, P. Uttley, S. G. Sergeev, T. Minezaki, Y. Yoshii, C. M. Gaskell, E. M. Cackett, K. Horne, S. Koshida
Long-Term Optical And X-Ray Variability Of The Seyfert Galaxy Markarian 79, E. Breedt, P. Arévalo, I. M. Mchardy, P. Uttley, S. G. Sergeev, T. Minezaki, Y. Yoshii, C. M. Gaskell, E. M. Cackett, K. Horne, S. Koshida
Physics and Astronomy Faculty Research Publications
We present the results of concurrent X-ray and optical monitoring of the Seyfert 1 galaxy Mrk 79 over a period of more than 5yr. We find that on short to medium time-scales (days to a few tens of days) the 2-10 keV X-ray and optical u- and V-band fluxes are significantly correlated, with a delay between the bands consistent with 0d. We show that most of these variations may be well reproduced by a model where the short-term optical variations originate from reprocessing of X-rays by an optically thick accretion disc. The optical light curves, however, also display long time-scale …
Veritas Observations Of A Very High Energy Gamma-Ray Flare From The Blazar 3c 66a, P. T. Reynolds, Et Al
Veritas Observations Of A Very High Energy Gamma-Ray Flare From The Blazar 3c 66a, P. T. Reynolds, Et Al
Physical Sciences Publications
The intermediate-frequency peaked BL Lacertae (IBL) object 3C 66A is detected during 2007-2008 in VHE (very high energy; E > 100 GeV) γ rays with the VERITAS stereoscopic array of imaging atmospheric Cherenkov telescopes. An excess of 1791 events is detected, corresponding to a significance of 21.2 standard deviations (σ), in these observations (32.8 hr live time). The observed integral flux above 200 GeV is 6% of the Crab Nebula's flux and shows evidence for variability on the timescale of days. The measured energy spectrum is characterized by a soft power law with photon index Γ = 4.1 ± 0.4stat ± …
Dark Matter Scaling Relations And The Assembly Epoch Of Coma Early-Type Galaxies, J. Thomas, R. P. Saglia, R. Bender, D. Thomas, K. Gebhardt, J Magorrian, E. M. Corsini, G. Wegner
Dark Matter Scaling Relations And The Assembly Epoch Of Coma Early-Type Galaxies, J. Thomas, R. P. Saglia, R. Bender, D. Thomas, K. Gebhardt, J Magorrian, E. M. Corsini, G. Wegner
Dartmouth Scholarship
Axisymmetric, orbit-based dynamical models are used to derive dark matter scaling relations for Coma early-type galaxies. From faint to bright galaxies, halo core radii and asymptotic circular velocities increase. Compared to spirals of the same brightness, the majority of Coma early-type galaxies—those with old stellar populations—have similar halo core radii but more than two times larger asymptotic halo velocities. The average dark matter density inside 2 r eff decreases with increasing luminosity and is 6.8 times larger than in disk galaxies of the same B-band luminosity. Compared at the same stellar mass, dark matter densities in ellipticals are 13.5 …
The June 2008 Flare Of Markarian 421 From Optical To Tev Energies, P. T. Reynolds, Et Al
The June 2008 Flare Of Markarian 421 From Optical To Tev Energies, P. T. Reynolds, Et Al
Physical Sciences Publications
We present optical, X-ray, high-energy (30 GeV) and very high energy (100 GeV; VHE) observations of the high-frequency peaked blazar Mrk 421 taken between 2008 May 24 and June 23. A high-energy γ-ray signal was detected by AGILE with between June 9 and 15, with F(E>100 MeV) = 42+14 –12 × 10–8 photons cm–2 s–1. This flaring state is brighter than the average flux observed by EGRET by a factor of ~3, but still consistent with the highest EGRET flux. In hard X-rays (20-60 keV) SuperAGILE resolved a five-day flare (June 9-15) peaking at ~55 mCrab. SuperAGILE, …
Discovery Of Very High-Energy Gamma-Ray Radiation From The Bl Lac 1es 0806+524, P. T. Reynolds, Et Al
Discovery Of Very High-Energy Gamma-Ray Radiation From The Bl Lac 1es 0806+524, P. T. Reynolds, Et Al
Physical Sciences Publications
The high-frequency-peaked BL Lacertae object 1ES 0806+524, at redshift z = 0.138, was observed in the very high energy (VHE) gamma-ray regime by VERITAS between 2006 November and 2008 April. These data encompass the two- and three-telescope commissioning phases, as well as observations with the full four-telescope array. 1ES 0806+524 is detected with a statistical significance of 6.3 standard deviations from 245 excess events. Little or no measurable variability on monthly timescales is found. The photon spectrum for the period 2007 November to 2008 April can be characterized by a power law with photon index 3.6 ± 1.0stat ± 0.3sys …
The Acs Survey Of Galactic Globular Clusters. Vi. Ngc 6366: A Heavily Stripped Galactic Globular Cluster, Nathaniel E. Q. Paust, Antonio Aparicio, Giampaolo Piotto, I. Neill Reid, Jay Anderson, Ata Sarajedini, Luigi R. Bedin, Brian Chaboyer
The Acs Survey Of Galactic Globular Clusters. Vi. Ngc 6366: A Heavily Stripped Galactic Globular Cluster, Nathaniel E. Q. Paust, Antonio Aparicio, Giampaolo Piotto, I. Neill Reid, Jay Anderson, Ata Sarajedini, Luigi R. Bedin, Brian Chaboyer
Dartmouth Scholarship
We have used observations obtained as part of the Hubble Space Telescope/ACS Survey of Galactic globular clusters (GCs) to construct a color-magnitude diagram for the bulge cluster, NGC 6366. The luminosity function derived from those data extends to M F606W ~ 9, or masses of ~0.3 M ☉. Unlike most GCs, the mass function peaks near the main-sequence turnoff with significantly fewer low-mass stars even after correction for completeness and mass segregation. Using a multimass King model, we extrapolate the global cluster behavior and find the global mass function to be poorly matched by a power law, with …
Ages And Metallicities Of Early-Type Void Galaxies From Line Strength Measurements, Gary Wegner, Norman A. Grogin
Ages And Metallicities Of Early-Type Void Galaxies From Line Strength Measurements, Gary Wegner, Norman A. Grogin
Dartmouth Scholarship
We present spectroscopic observations of 26 galaxies of type E and S0, based on their blue morphologies, located in voids by the study of Grogin & Geller in 1999. Measurements of redshift, velocity dispersion, and four Lick line indices, Mg b , Fe5270, Fe5335, and Hβ with their errors are given for all of these galaxies, along with Hβ, [O III], Hα, and [N II] emission line strengths for a subset of these objects. These sources are brighter than M* for low-density regions and tend to be bluer than their counterpart early-type objects in high-density regions. Using the models …
Structure Formation Inside Triaxial Dark Matter Halos: Galactic Disks, Bulges, And Bars, Clayton Heller, Isaac Shlosman, Evangelie Athanassoula
Structure Formation Inside Triaxial Dark Matter Halos: Galactic Disks, Bulges, And Bars, Clayton Heller, Isaac Shlosman, Evangelie Athanassoula
Physics & Astronomy: Faculty Publications
We investigate formation and evolution of galactic disks immersed in assembling live DM halos. Models have been evolved from cosmological initial conditions and represent the collapse of an isolated density perturbation. The baryons include gas participating in star formation (SF) and stars with the energy feedback onto the ISM. We find that (1) the triaxial halo figure tumbling is insignificant and the angular momentum (J) is channeled into the internal circulation, while the baryonic collapse is stopped by the centrifugal barrier; (2) density response of the (disk) baryons is out of phase with DM, thus washing out the …
Testing Thermal Reprocessing In Active Galactic Nuclei Accretion Discs, Edward M. Cackett, Keith Horne, Hartmut Winkler
Testing Thermal Reprocessing In Active Galactic Nuclei Accretion Discs, Edward M. Cackett, Keith Horne, Hartmut Winkler
Physics and Astronomy Faculty Research Publications
The thermal reprocessing hypothesis in active galactic nuclei (AGN), where extreme ultraviolet/X-ray photons are reprocessed by the accretion disc into optical/UV photons, predicts wavelength-dependent time-delays between the optical continuum at different wavelengths. Recent photometric monitoring by Sergeev et al. has shown that the time-delay is observed in 14 AGN, and generally seen to increase with increasing wavelength, as predicted in the reprocessing scenario. We fit the observed time-delays and optical spectral energy distribution using a disc reprocessing model. The model delivers estimates for the nuclear reddening, the product of black hole mass and accretion rate, and the distance to each …
Ngc 5548 In A Low-Luminosity State: Implications For The Broad-Line Region, Misty C. Bentz, Kelly D. Denney, Edward M. Cackett, Matthias Dietrich, Jeffery K. J. Fogel, Himel Ghosh, Keith Horne, Charles Kuehn, Takeo Minezaki, Christopher A. Onken, Bradley M. Peterson, Richard W. Pogge, Vladimir I. Pronik, Douglas O. Richstone, Sergey G. Sergeev, Marianne Vestergaard, Matthew G. Walker, Yuzuru Yoshii
Ngc 5548 In A Low-Luminosity State: Implications For The Broad-Line Region, Misty C. Bentz, Kelly D. Denney, Edward M. Cackett, Matthias Dietrich, Jeffery K. J. Fogel, Himel Ghosh, Keith Horne, Charles Kuehn, Takeo Minezaki, Christopher A. Onken, Bradley M. Peterson, Richard W. Pogge, Vladimir I. Pronik, Douglas O. Richstone, Sergey G. Sergeev, Marianne Vestergaard, Matthew G. Walker, Yuzuru Yoshii
Physics and Astronomy Faculty Research Publications
We describe results from a new ground-based monitoring campaign on NGC 5548, the best-studied reverberation-mapped AGN. We find that it was in the lowest luminosity state yet recorded during a monitoring program, namely L5100=4.7×1042 ergs s-1. We determine a rest-frame time lag between flux variations in the continuum and the Hβ line of 6.3+2.6-2.3 days. Combining our measurements with those of previous campaigns, we determine a weighted black hole mass of MBH=6.54+0.26-0.25×107 Msolar based on all broad emission lines with suitable variability data. We confirm the …
The Mass Of The Black Hole In The Seyfert 1 Galaxy Ngc 4593 From Reverberation Mapping, Kelly D. Denney, Misty C. Bentz, Bradley M. Peterson, Richard W. Pogge, Edward M. Cackett, Matthias Dietrich, Jeffrey K. J. Fogel, Himel Ghosh, Keith D. Horne, Charles Kuehn, Takeo Minezaki, Christopher A. Onken, Vladimir I. Pronik, Douglas O. Richstone, Sergey G. Sergeev, Marianne Vestergaard, Matthew G. Walker, Yuzuru Yoshii
The Mass Of The Black Hole In The Seyfert 1 Galaxy Ngc 4593 From Reverberation Mapping, Kelly D. Denney, Misty C. Bentz, Bradley M. Peterson, Richard W. Pogge, Edward M. Cackett, Matthias Dietrich, Jeffrey K. J. Fogel, Himel Ghosh, Keith D. Horne, Charles Kuehn, Takeo Minezaki, Christopher A. Onken, Vladimir I. Pronik, Douglas O. Richstone, Sergey G. Sergeev, Marianne Vestergaard, Matthew G. Walker, Yuzuru Yoshii
Physics and Astronomy Faculty Research Publications
We present new observations leading to an improved black hole mass estimate for the Seyfert 1 galaxy NGC 4593 as part of a reverberation-mapping campaign conducted at the MDM Observatory. Cross-correlation analysis of the Hβ emission-line light curve with the optical continuum light curve reveals an emission-line time delay of τcent=3.73+/-0.75 days. By combining this time delay with the Hβ line width, we derive a central black hole mass of MBH=(9.8+/-2.1)×106 Msolar, an improvement in precision of a factor of several over past results.
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
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 …
Photoionized HΒ Emission In Ngc 5548: It Breathes!, Edward M. Cackett, Keith Horne
Photoionized HΒ Emission In Ngc 5548: It Breathes!, Edward M. Cackett, Keith Horne
Physics and Astronomy Faculty Research Publications
Emission-line regions in active galactic nuclei (AGNs) and other photoionized nebulae should become larger in size when the ionizing luminosity increases. This `breathing' effect is observed for the Hβ emission in NGC 5548 by using Hβ and optical continuum light curves from the 13-yr (1989-2001) AGN Watch monitoring campaign. To model the breathing, we use two methods to fit the observed light curves in detail: (i) parametrized models and, (ii) the MEMECHO reverberation-mapping code. Our models assume that optical continuum variations track the ionizing radiation, and that the Hβ variations respond with time-delays τ due to light travel-time. By fitting …
The Oxford-Dartmouth Thirty Degree Survey - Ii. Clustering Of Bright Lyman Break Galaxies: Strong Luminosity-Dependent Bias At Z = 4, Paul D. Allen, Leonidas A. Moustakas, Gavin Dalton, Emily Macdonald, Chris Blake, Lee Clewley, Catherine Heymans, Gary Wegner
The Oxford-Dartmouth Thirty Degree Survey - Ii. Clustering Of Bright Lyman Break Galaxies: Strong Luminosity-Dependent Bias At Z = 4, Paul D. Allen, Leonidas A. Moustakas, Gavin Dalton, Emily Macdonald, Chris Blake, Lee Clewley, Catherine Heymans, Gary Wegner
Dartmouth Scholarship
We present measurements of the clustering properties of bright (L > L*) z~4 Lyman break galaxies (LBGs) selected from the Oxford-Dartmouth Thirty Degree Survey (ODT). We describe techniques used to select and evaluate our candidates and calculate the angular correlation function, which we find best fitted by a power law, ω(θ) =Awθ−β with Aw= 15.4 (with θ in arcsec), using a constrained slope of β= 0.8. Using a redshift distribution consistent with photometric models, we deproject this correlation function and find a comoving Mpc in a Ωm= 0.3 flat λ cosmology for iAB≤ 24.5. This corresponds to a linear bias value …
Structural Properties Of Discs And Bulges Of Early-Type Galaxies, Roelof S. De Jong, Luc Simard, Roger L. Davies, R. P. Saglia, David Burstein, Matthew Colless, Robert Mcmahan, Gary Wegner
Structural Properties Of Discs And Bulges Of Early-Type Galaxies, Roelof S. De Jong, Luc Simard, Roger L. Davies, R. P. Saglia, David Burstein, Matthew Colless, Robert Mcmahan, Gary Wegner
Dartmouth Scholarship
We have used the EFAR sample of galaxies to investigate the light distributions of early-type galaxies. We decompose the two-dimensional light distribution of the galaxies in a flattened spheroidal component with a Sérsic radial light profile and an inclined disc component with an exponential light profile. We show that if we assume that all galaxies can have a spheroidal and a disc component, then the brightest, bulge-dominated elliptical galaxies have a fairly broad distribution in the Sérsic profile shape parameter nB, with a median of approximately 3.7 and with σ∼ 0.9. Other galaxies have smaller nB values. …
The Oxford-Dartmouth Thirty Degree Survey - I. Observations And Calibration Of A Wide-Field Multiband Survey, Emily C. Macdonald, Paul Allen, Gavin Dalton, Leonidas A. Moustakas, Catherine Heymans, Edward Edmondso N, Chris Blake, Lee Clewley, Molly C. Hammell, Ed Olding, Lance Miller, Steve Rawlings, Jasper Wall, Gary Wegner, Christian Wolf
The Oxford-Dartmouth Thirty Degree Survey - I. Observations And Calibration Of A Wide-Field Multiband Survey, Emily C. Macdonald, Paul Allen, Gavin Dalton, Leonidas A. Moustakas, Catherine Heymans, Edward Edmondso N, Chris Blake, Lee Clewley, Molly C. Hammell, Ed Olding, Lance Miller, Steve Rawlings, Jasper Wall, Gary Wegner, Christian Wolf
Dartmouth Scholarship
The Oxford–Dartmouth Thirty Degree Survey (ODTS) is a deep, wide, multiband imaging survey designed to cover a total of 30 deg2 in BV Ri′Z, with a subset of U- and K-band data, in four separate fields of 5–10 deg2 centred at 00:18:24 +34:52, 09:09:45 +40:50, 13:40:00 +02:30 and 16:39:30 +45:24. Observations have been made using the Wide Field Camera on the 2.5-m Isaac Newton Telescope (INT) in La Palma to average limiting depths (5σ Vega, aperture magnitudes) of U= 24.8, B= 25.6, V= 25.0, R= 24.6 and i′= …
Spatially Resolved Spectroscopy Of Coma Cluster Early-Type Galaxies - Ii. The Minor Axis Dataset, G. Wegner, E. M. Corsini, R. P. Saglia, R. Bender
Spatially Resolved Spectroscopy Of Coma Cluster Early-Type Galaxies - Ii. The Minor Axis Dataset, G. Wegner, E. M. Corsini, R. P. Saglia, R. Bender
Dartmouth Scholarship
We present minor axis, offset major axis and one diagonal long slit spectra for 10 E and S0 galaxies of the Coma cluster drawn from a magnitude-limited sample studied before. We derive rotation curves, velocity dispersion profiles and the H3 and H4 coefficients of the Hermite decomposition of the line of sight velocity distribution. Moreover, we derive the line index profiles of Mg, Fe and Hβ line indices and assess their errors. The data will be used to construct dynamical models of the galaxies and study their stellar populations.
Comparing The Sfi Peculiar Velocities With The Pscz Gravity Field: A Velmod Analysis, E. Branchini, W. Freudling, L. N. Da Costa, C. S. Frenk, R. Giovanelli, M. P. Haynes, J. J. Salzer, G. Wegner, I. Zehavi
Comparing The Sfi Peculiar Velocities With The Pscz Gravity Field: A Velmod Analysis, E. Branchini, W. Freudling, L. N. Da Costa, C. S. Frenk, R. Giovanelli, M. P. Haynes, J. J. Salzer, G. Wegner, I. Zehavi
Dartmouth Scholarship
We compare the peculiar velocities derived from the I-band Tully–Fisher (TF) relation for 989 field spiral galaxies in the SFI catalogue with the predicted velocity field derived from the IRAS PSCz galaxy redshift survey. We assume linear gravitational instability theory and apply the maximum likelihood technique, VELMOD to SFI galaxies within a redshift cz LG =6000 km s−1. The resulting calibration of the TF relation is consistent with a previous, independent calibration for a similar sample of spirals residing in clusters. Our analysis provides an accurate estimate of the quantity βI ≡ Ωm0.6 …