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Articles 6691 - 6720 of 8870

Full-Text Articles in Astrophysics and Astronomy

A Determination Of The Spin-Orbit Alignment Of The Anomalously Dense Planet Orbiting Hd 149026, Aaron S. Wolf, Gregory Laughlin, Gregory W. Henry, Debra A. Fischer, Geoffrey W. Marcy, R. Paul Butler, Steve Vogt Sep 2007

A Determination Of The Spin-Orbit Alignment Of The Anomalously Dense Planet Orbiting Hd 149026, Aaron S. Wolf, Gregory Laughlin, Gregory W. Henry, Debra A. Fischer, Geoffrey W. Marcy, R. Paul Butler, Steve Vogt

Information Systems and Engineering Management Research Publications

We report 35 radial velocity measurements of HD 149026 taken with the Keck Telescope. Of these measurements, 15 were made during the transit of the companion planet HD 149026b, which occurred on 2005 June 25. These velocities provide a high-cadence observation of the Rossiter-McLaughlin effect, the shifting of photospheric line profiles that occurs when a planet occults a portion of the rotating stellar surface. We combine these radial velocities with previously published radial velocity and photometric data sets and derive a composite best-fit model for the star-planet system. This model confirms and improves previously published orbital parameters, including the remarkably …

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The First Frontier: High Altitude Ballooning And Access To Near Space, Shane L. Larson Sep 2007

The First Frontier: High Altitude Ballooning And Access To Near Space, Shane L. Larson

Colloquia and Seminars

No abstract provided.

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A Burst Chasing X-Ray Polarimeter, Joanne E. Hill, Scott Barthelmy, J Kevin Black, Philip Deines-Jones, Keith Jahoda, Takanori Sakamoto, Philip Kaaret, Mark L. Mcconnell, Peter F. Bloser, John R. Macri, Jason S. Legere, James M. Ryan, Billy R. Smith Jr, Bing Zhang Sep 2007

A Burst Chasing X-Ray Polarimeter, Joanne E. Hill, Scott Barthelmy, J Kevin Black, Philip Deines-Jones, Keith Jahoda, Takanori Sakamoto, Philip Kaaret, Mark L. Mcconnell, Peter F. Bloser, John R. Macri, Jason S. Legere, James M. Ryan, Billy R. Smith Jr, Bing Zhang

Space Science Center

Gamma-ray bursts are one of the most powerful explosions in the universe and have been detected out to distances of almost 13 billion light years. The exact origin of these energetic explosions is still unknown but the resulting huge release of energy is thought to create a highly relativistic jet of material and a power-law distribution of electrons. There are several theories describing the origin of the prompt GRB emission that currently cannot be distinguished. Measurements of the linear polarization would provide unique and important constraints on the mechanisms thought to drive these powerful explosions. We present the design of …

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Constraining F(R) Gravity As A Scalar-Tensor Theory, Thomas Faulkner, Max Tegmark, Emory F. Bunn, Yi Mao Sep 2007

Constraining F(R) Gravity As A Scalar-Tensor Theory, Thomas Faulkner, Max Tegmark, Emory F. Bunn, Yi Mao

Physics Faculty Publications

We search for viable f(R) theories of gravity, making use of the equivalence between such theories and scalar-tensor gravity. We find that models can be made consistent with solar system constraints either by giving the scalar a high mass or by exploiting the so-called chameleon effect. However, in both cases, it appears likely that any late-time cosmic acceleration will be observationally indistinguishable from acceleration caused by a cosmological constant. We also explore further observational constraints from, e.g., big bang nucleosynthesis and inflation.

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The Agn-Obscuring Torus: The End Of The "Doughnut" Paradigm?, Moshe Elitzur, Isaac Shlosman Sep 2007

The Agn-Obscuring Torus: The End Of The "Doughnut" Paradigm?, Moshe Elitzur, Isaac Shlosman

Physics and Astronomy Faculty Publications

Unified schemes of active galactic nuclei (AGNs) require an obscuring dusty torus around the central engine. The compact sizes (only a few parsecs) determined in recent high-resolution observations require that the obscuring matter be clumpy and located inside the region where the black hole gravity dominates over the galactic bulge. This location is in line with the scenario depicting the torus as the region of the clumpy wind coming off the accretion disk in which the clouds are dusty and optically thick. We study here the outflow scenario within the framework of hydromagnetic disk winds, incorporating the cloud properties determined …

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The Acs Survey Of Galactic Globular Clusters: M54 And Young Populations In The Sagittarius Dwarf Spheroidal Galaxy, Michael H. Siegel, Aaron Dotter, Steven R. Majewski, Ata Sarajedini, Brian Chaboyer, David L. Nidever, Jay Anderson, Antonio Martin-French, Alfred Rosenberg, Luigi R. Bedin, Antonio Aparicio, Ivan King, Giampolo Piotto, I. Neill Reid Sep 2007

The Acs Survey Of Galactic Globular Clusters: M54 And Young Populations In The Sagittarius Dwarf Spheroidal Galaxy, Michael H. Siegel, Aaron Dotter, Steven R. Majewski, Ata Sarajedini, Brian Chaboyer, David L. Nidever, Jay Anderson, Antonio Martin-French, Alfred Rosenberg, Luigi R. Bedin, Antonio Aparicio, Ivan King, Giampolo Piotto, I. Neill Reid

Dartmouth Scholarship

As part of the ACS Survey of Galactic Globular Clusters, we present new Hubble Space Telescope photometry of the massive globular cluster M54 (NGC 6715) and the superposed core of the tidally disrupted Sagittarius (Sgr) dSph galaxy. Our deep (F606W ~ 26.5), high-precision photometry yields an unprecedentedly detailed color-magnitude diagram showing the extended blue horizontal branch and multiple main sequences of the M54+Sgr system. The distance and reddening to M54 are revised using both isochrone and main-sequence fitting to (m - M)0 = 17.27 and E(B - V) = 0.15. Preliminary assessment finds the …

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Development Of A Method For Calculating Delta Scuti Rotational Velocities And Hydrogen Beta Color Indices, Tabitha Christi Buehler Sep 2007

Development Of A Method For Calculating Delta Scuti Rotational Velocities And Hydrogen Beta Color Indices, Tabitha Christi Buehler

Theses and Dissertations

To add to the understanding of the structure and evolution of Delta Scuti stars, 167 Delta Scutis north of -01 degrees declination and brighter than 13th magnitude have been observed spectroscopically. A method for calculating rotational velocity values and Hydrogen-Beta color indices for the stars in the data set with no previously published values is developed, using the stars in the data set brighter than 7th magnitude. Rotational velocity values for four stars with previously unknown values and Hydrogen-Beta index values for five stars with previously unknown values are calculated.

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Testing Thermal Reprocessing In Active Galactic Nuclei Accretion Discs, Edward M. Cackett, Keith Horne, Hartmut Winkler Sep 2007

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 …

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Near-Terminator Venus Ionosphere: Evidence For A Dawn/Dusk Asymmetry In The Thermosphere, Jane L. Fox, W. T. Kasprzak Sep 2007

Near-Terminator Venus Ionosphere: Evidence For A Dawn/Dusk Asymmetry In The Thermosphere, Jane L. Fox, W. T. Kasprzak

Physics Faculty Publications

Recent models of the near-terminator ionosphere of Venus constructed using neutral density profiles from the VTS3 model of Hedin et al. (1983) have shown that altitudes of the electron density peaks are in agreement with those measured by Pioneer Venus (PV) Orbiter Radio Occultation (ORO) and other radio occultation profiles in the solar zenith angle (SZA) range 60 to 70°, where they are near 140 km (Fox, 2007). The model peaks in the 75–85° range, however, do not decrease in altitude to near 135 km, as do the PV ORO electron density peaks shown in the study of Cravens et …

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Near-Terminator Venus Ionosphere: How Chapman-Esque?, Jane L. Fox Sep 2007

Near-Terminator Venus Ionosphere: How Chapman-Esque?, Jane L. Fox

Physics Faculty Publications

We have modeled the near-terminator ionosphere of Venus for solar zenith angles χ between 60 and 85° in 5° increments, and from 86 to 90° in 1° increments. The most important neutral densities of the background thermospheres have been adopted from the VTS3 model of Hedin et al. (1983), which is based on densities from the Pioneer Venus (PV) Orbiter Neutral Mass Spectrometer (e.g., Niemann et al., 1980) that are normalized to the PV Orbiter Atmospheric Drag data (e.g., Keating et al., 1980). We compare the ion density profiles to those of a Chapman layer and to those obtained from …

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1139-3159_Nir_Spex, Dagny L. Looper Sep 2007

1139-3159_Nir_Spex, Dagny L. Looper

Publications and Research

No abstract provided.

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Stellar Populations Across The Ngc 4244 Truncated Galactic Disk., Roelof De Jong, A. C. Seth, D. Radburn-Smith, E. F. Bell, T. M. Brown, J. S. Bullock, S. Courteau, J. J. Dalcanton, H. C. Ferguson, P. Goudfrooij, S. Holfeltz, Benne W. Holwerda, C. Purcell, J. Sick, D. B. Zucker Sep 2007

Stellar Populations Across The Ngc 4244 Truncated Galactic Disk., Roelof De Jong, A. C. Seth, D. Radburn-Smith, E. F. Bell, T. M. Brown, J. S. Bullock, S. Courteau, J. J. Dalcanton, H. C. Ferguson, P. Goudfrooij, S. Holfeltz, Benne W. Holwerda, C. Purcell, J. Sick, D. B. Zucker

Faculty and Staff Scholarship

We use the Hubble Space Telescope ACS to study the resolved stellar populations of the nearby, nearly edgeon galaxy NGC 4244 across its outer disk surface density break. The stellar photometry allows us to study the distribution of different stellar populations and reach very low equivalent surface brightnesses. We find that the break occurs at the same radius for young, intermediate-age, and old stars. The stellar density beyond the break drops sharply by a factor of at least 600 in 5 kpc. The break occurs at the same radius independent of height above the disk, but is sharpest in the …

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Book Review: Moore On Mercury: The Planet And The Missions, T. D. Oswalt Sep 2007

Book Review: Moore On Mercury: The Planet And The Missions, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of Moore on Mercury : the Planet and the Missions by Patrick Moore. Springer, 2006 139p, 1846282578 $29.95, 9781846282577 $29.95

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Stellar Population Models And Individual Element Abundances. I. Sensitivity Of Stellar Evolution Models, Aaron Dotter, Brian Chaboyer, Jason W. Ferguson, Hyun Chul Lee, Guy Worthey, Darko Jevremović, E. Baron Sep 2007

Stellar Population Models And Individual Element Abundances. I. Sensitivity Of Stellar Evolution Models, Aaron Dotter, Brian Chaboyer, Jason W. Ferguson, Hyun Chul Lee, Guy Worthey, Darko Jevremović, E. Baron

Physics & Astronomy Faculty Publications

Integrated light from distant galaxies is often compared to stellar population models via the equivalent widths of spectral features-spectral indices-whose strengths rely on the abundances of one or more elements. Such comparisons hinge not only on the overall metal abundance, but also on relative abundances. Studies have examined the influence of individual elements on synthetic spectra but little has been done to address similar issues in the stellar evolution models that underlie most stellar population models. Stellar evolution models will primarily be influenced by changes in opacities. In order to explore this issue in detail, 12 sets of stellar evolution …

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Search For Gravitational Wave Radiation Associated With The Pulsating Tail Of The Sgr 1806−20 Hyperflare Of 27 December 2004 Using Ligo, B. P. Abbott, R. Abbott, Mario C. Diaz, R. Grosso, Soumya Mohanty, Soma Mukherjee, Cristina V. Torres Sep 2007

Search For Gravitational Wave Radiation Associated With The Pulsating Tail Of The Sgr 1806−20 Hyperflare Of 27 December 2004 Using Ligo, B. P. Abbott, R. Abbott, Mario C. Diaz, R. Grosso, Soumya Mohanty, Soma Mukherjee, Cristina V. Torres

Physics & Astronomy Faculty Publications

We have searched for gravitational waves (GWs) associated with the SGR 1806−20 hyperflare of 27 December 2004. This event, originating from a Galactic neutron star, displayed exceptional energetics. Recent investigations of the x-ray light curve’s pulsating tail revealed the presence of quasiperiodic oscillations (QPOs) in the 30–2000 Hz frequency range, most of which coincides with the bandwidth of the LIGO detectors. These QPOs, with well-characterized frequencies, can plausibly be attributed to seismic modes of the neutron star which could emit GWs. Our search targeted potential quasimonochromatic GWs lasting for tens of seconds and emitted at the QPO frequencies. We have …

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Gas Feedback On Stellar Bar Evolution, Ingo Berentzen, Isaac Shlosman, Inma Martinez-Valpuesta, Clayton Heller Sep 2007

Gas Feedback On Stellar Bar Evolution, Ingo Berentzen, Isaac Shlosman, Inma Martinez-Valpuesta, Clayton Heller

Physics & Astronomy: Faculty Publications

We analyze evolution of live disk-halo systems with gas fractions, fgas ≤ 8% of the disk mass, for 5 Gyr. Specifically, we have addressed the issue of angular momentum (J) transfer from the gas to the stellar bar and its effect on the bar. We find that the bar weakening, reported in the literature, is not related to the gas, but is caused by the vertical buckling instability in the gas-poor disks and by a steep stellar heating by the central mass concentration (CMC) in the gas-rich disks. However, the gas has a profound effect on the …

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Stellar Population Models And Individual Element Abundances. I. Sensitivity Of Stellar Evolution Models, Aaron Dotter, Brian Chaboyer, Jason W. Ferguson, Hyun-Chul Lee Sep 2007

Stellar Population Models And Individual Element Abundances. I. Sensitivity Of Stellar Evolution Models, Aaron Dotter, Brian Chaboyer, Jason W. Ferguson, Hyun-Chul Lee

Dartmouth Scholarship

Integrated light from distant galaxies is often compared to stellar population models via the equivalent widths of spectral features—spectral indices—whose strengths rely on the abundances of one or more elements. Such comparisons hinge not only on the overall metal abundance, but also on relative abundances. Studies have examined the influence of individual elements on synthetic spectra but little has been done to address similar issues in the stellar evolution models that underlie most stellar population models. Stellar evolution models will primarily be influenced by changes in opacities. In order to explore this issue in detail, 12 sets of stellar evolution …

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The Tennessee State University Automatic Spectroscopic Telescope: Data Processing And Velocity Variation Of Cool Giants, Joel A. Eaton, Michael H. Williamson Aug 2007

The Tennessee State University Automatic Spectroscopic Telescope: Data Processing And Velocity Variation Of Cool Giants, Joel A. Eaton, Michael H. Williamson

Information Systems and Engineering Management Research Publications

This paper discusses data reduction for an echelle spectrograph we have developed for an automatic telescope at Tennessee State University and are using to monitor radial velocities and line profiles of cool giant and supergiant stars. Although our approach to data reduction is rather conventional, we discuss flat‐fielding and extraction of velocities in ways that should be of general interest, establish a transformation to the IAU radial velocity system (+0.35 ± 0.09 km s−1), and determine the external precision for measured velocities (0.10–0.11 km s−1). Also, we present results of the first 2–3 years of monitoring radial velocities in about …

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Optimization Of Control Source And Error Sensor Locations In Free Field Active Noise Control, Connor Raymond Duke Aug 2007

Optimization Of Control Source And Error Sensor Locations In Free Field Active Noise Control, Connor Raymond Duke

Theses and Dissertations

Previous work has shown that active noise control (ANC) can be applied to axial cooling fans. Optimization of the control source and error sensor placement is desired to maximize the attenuation using ANC. A genetic algorithm was developed to find the optimal placement of control sources for a given primary source. The optimal configuration of control sources around a single primary source was shown to be a linear arrangement of the sources. This holds true for both two-dimensional as well as three-dimensional configurations. The higher-order radiation of the linear arrangement has also been verified experimentally, but the improvement in the …

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Dynamical Modelling Of Luminous And Dark Matter In 17 Coma Early-Type Galaxies, J. Thomas, R. O. Saglia, R. Bender, D. Thomas, J K. Gebhardt, J. Magorrian, E. M. Corsini, G. Wegner Aug 2007

Dynamical Modelling Of Luminous And Dark Matter In 17 Coma Early-Type Galaxies, J. Thomas, R. O. Saglia, R. Bender, D. Thomas, J K. Gebhardt, J. Magorrian, E. M. Corsini, G. Wegner

Dartmouth Scholarship

Dynamical models for 17 early‐type galaxies in the Coma cluster are presented. The galaxy sample consists of flattened, rotating as well as non‐rotating early‐types including cD and S0 galaxies with luminosities between MB=−18.79 and −22.56. Kinematical long‐slit observations cover at least the major‐axis and minor‐axis and extend to 1–4reff. Axisymmetric Schwarzschild models are used to derive stellar mass‐to‐light ratios and dark halo parameters. In every galaxy, the best fit with dark matter matches the data better than the best fit without. The statistical significance is over 95 per cent for eight galaxies, around 90 per …

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Development Of A New Ca Ii H And K Spectrophotometric Temperature Index, Kathleen Elizabeth Moncrieff Aug 2007

Development Of A New Ca Ii H And K Spectrophotometric Temperature Index, Kathleen Elizabeth Moncrieff

Theses and Dissertations

We are developing a new spectrophotometric temperature index based on the Ca II H and K lines. Because these lines are present even in very cool stars and because the Ca II H line is blended with the H-epsilon line in hot stars, this index should cover a very broad range of spectral types. Our data set consisted of 95 stars with spectral types ranging from O9 to M1. We examined five different indices based on the Ca II H + H-epsilon and K lines, as well as single-wavelength indices centered on each of the H-delta and H-gamma lines, which …

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Diffusive Compression Acceleration Of Energetic Particles With An Application To Shock Acceleration Near Injection Energies, Ming Zhang Aug 2007

Diffusive Compression Acceleration Of Energetic Particles With An Application To Shock Acceleration Near Injection Energies, Ming Zhang

Aerospace, Physics, and Space Science Faculty Publications

The behavior of energetic charged particles accelerated by a continuous plasma compression profile is explored in the framework of diffusion. At high enough energies, the accelerated particles have a power-law spectrum with a slope generally steeper than a shock spectrum with the same compression ratio. The spectral slope depends on the ratio of the diffusion coefficient to the product of the upstream plasma speed and the thickness of the compression region. In the limit of large diffusion, the spectrum becomes identical to that of diffusive shock acceleration, and when diffusion is small enough, it is consistent with adiabatic acceleration by …

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The Effect Of Nonlinear Propagation On Near-Field Acoustical Holography, Micah Raymond Shepherd Aug 2007

The Effect Of Nonlinear Propagation On Near-Field Acoustical Holography, Micah Raymond Shepherd

Theses and Dissertations

Near-field acoustical holography (NAH) has been used extensively for acoustical imaging of infinitesimal-amplitude (or small-amplitude) sources. However, recent interests are in the application of NAH to image finite-amplitude (or high-amplitude) sources such as jets and rockets. Since NAH is based on linear equations and finite-amplitude sources imply nonlinear effects, which cause shock formation and consequently an altered spectral shape, a feasibility study is carried out to determine the effect of nonlinear propagation on NAH. Jet and rocket sources typically have a distinct spectral shape resembling a ‘haystack’ and center frequencies varying from 30 to 300 Hz. To test the effect …

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Monsters In The Cosmic Sea: Black Holes And Einstein's Astrophysical Legacy, Shane L. Larson Aug 2007

Monsters In The Cosmic Sea: Black Holes And Einstein's Astrophysical Legacy, Shane L. Larson

Public Talks

No abstract provided.

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Oases In The Dark: Galaxies As Probes Of The Cosmos, Shane L. Larson Aug 2007

Oases In The Dark: Galaxies As Probes Of The Cosmos, Shane L. Larson

Public Talks

No abstract provided.

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Mixing And Homogenization In The Early Solar System: Clues From Sr, Ba, Nd, And Sm Isotopes In Meteorites, Rasmus Andreasen, Mukul Sharma Aug 2007

Mixing And Homogenization In The Early Solar System: Clues From Sr, Ba, Nd, And Sm Isotopes In Meteorites, Rasmus Andreasen, Mukul Sharma

Dartmouth Scholarship

High-precision barium isotopic compositions of large samples of an ordinary chondrite and a eucrite are identical to the terrestrial values. In contrast, the carbonaceous chondrites reveal excesses in 135Ba and 137Ba of around +39 and +22 parts per million (ppm), respectively; no anomalies are resolvable in 130,132,138Ba. High-precision Sr isotopic compositions of all meteorites are identical within error. The data are consistent with the carbonaceous chondrites having an excess in the r-process 135,137Ba with respect to Earth, eucrite parent bodies, and ordinary chondrites. The carbonaceous chondrites, however, display no variation in the r- and …

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Supernova Injection Of Short-Lived Radionuclides Into The Presolar Cloud: A Feasibility Study, Keith Davis Aug 2007

Supernova Injection Of Short-Lived Radionuclides Into The Presolar Cloud: A Feasibility Study, Keith Davis

All Dissertations

Meteorite inclusions show that the early solar system was radioactive with species of short lifetimes compared to the formation time of the solar system. Transporting the radioactive material from the creation site to the formation site of the sun was expected to take enough time that these species should have decayed to nonexistence. Some special series of events seems necessary to speed the process along. Cameron & Truran (1977) suggested that the source of these short-lived radionuclides could have been a supernova. Numerical hydrodynamic studies have shown that slow shockwaves can inject material into a small, dense cloud core. Most …

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Upper Limits On Gravitational Wave Emission From 78 Radio Pulsars, B. Abbott, R. Abbott, R. Adhikari, J. Agresti, P. Ajith, B. Allen, R. Amin, S. B. Anderson, W. G. Anderson, M. Arain, M. Araya, H. Armandula, M. Ashley, S. Aston, P. Aufmuth, C. Aulbert, S. Babak, S. Ballmer, H. Bantilan, B. C. Barish, C. Barker, D. Barker, B. Barr, P. Barriga, M. A. Barton, K. Bayer, K. Belczynski, J. Betzwieser, P. T. Beyersdorf, B. Bhawal, I. A. Bilenko, Tiffany Z. Summerscales Aug 2007

Upper Limits On Gravitational Wave Emission From 78 Radio Pulsars, B. Abbott, R. Abbott, R. Adhikari, J. Agresti, P. Ajith, B. Allen, R. Amin, S. B. Anderson, W. G. Anderson, M. Arain, M. Araya, H. Armandula, M. Ashley, S. Aston, P. Aufmuth, C. Aulbert, S. Babak, S. Ballmer, H. Bantilan, B. C. Barish, C. Barker, D. Barker, B. Barr, P. Barriga, M. A. Barton, K. Bayer, K. Belczynski, J. Betzwieser, P. T. Beyersdorf, B. Bhawal, I. A. Bilenko, Tiffany Z. Summerscales

Faculty Publications

We present upper limits on the gravitational wave emission from 78 radio pulsars based on data from the third and fourth science runs of the LIGO and GEO 600 gravitational wave detectors. The data from both runs have been combined coherently to maximize sensitivity. For the first time, pulsars within binary (or multiple) systems have been included in the search by taking into account the signal modulation due to their orbits. Our upper limits are therefore the first measured for 56 of these pulsars. For the remaining 22, our results improve on previous upper limits by up to a factor …

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Testing Lorentz Symmetry With Gravity, Quentin G. Bailey Aug 2007

Testing Lorentz Symmetry With Gravity, Quentin G. Bailey

Publications

In this talk, results from the gravitational sector of the Standard-Model Extension (SME) are discussed. The weak-field phenomenology of the resulting modified gravitational field equations is explored. The application of the results to a variety of modern gravity experiments, including lunar laser ranging, Gravity Probe B, binary pulsars, and Earth-laboratory tests, shows promising sensitivity to gravitational coefficients for Lorentz violation in the SME.

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A Dust Component ~2 Kpc Above The Plane In Ngc 891., P. Kamphuis, Benne W. Holwerda, R. J. Allen, R. F. Peletier, P. C. Van Der Kruit Aug 2007

A Dust Component ~2 Kpc Above The Plane In Ngc 891., P. Kamphuis, Benne W. Holwerda, R. J. Allen, R. F. Peletier, P. C. Van Der Kruit

Faculty and Staff Scholarship

Context.The halo of NGC 891 has been the subject of studies for more than a decade. One of its most striking features is the large asymmetry in H emission. In this letter, we will take a quantitative look at this asymmetry at different wavelengths for the first time.
Aims.We suggest that NGC 891 is intrinsically almost symmetric and the large asymmetry in H emission is mostly due to dust attenuation. We will quantify the additional optical depth needed to cause the observed asymmetry in this model.
Methods.By comparing large strips on the North East side of the …

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