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Full-Text Articles in Physical Sciences and Mathematics

A Comparison Of X-Ray And Optical Emission In Cassiopeia A, Daniel J. Patnaude, Robert A. Fesen Mar 2014

A Comparison Of X-Ray And Optical Emission In Cassiopeia A, Daniel J. Patnaude, Robert A. Fesen

Dartmouth Scholarship

Broadband optical and narrowband Si XIII X-ray images of the young Galactic supernova remnant Cassiopeia A (Cas A) obtained over several decades are used to investigate spatial and temporal emission correlations on both large and small angular scales. The data examined consist of optical and near infrared ground-based and Hubble Space Telescope images taken between 1951 and 2011, and X-ray images from Einstein, ROSAT, and Chandra taken between 1979 and 2013. We find weak spatial correlations between the remnant’s X-ray and optical emission features on large scales, but several cases of good optical/X-ray correlations on small scales for features which …

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Deep Silicate Absorption Features In Compton-Thick Active Galactic Nuclei Predominantly Arise Due To Dust In The Host Galaxy, A. D. Goulding, D. M. Alexander, F. E. Bauer, W. R. Forman, R. C. Hickox Jul 2012

Deep Silicate Absorption Features In Compton-Thick Active Galactic Nuclei Predominantly Arise Due To Dust In The Host Galaxy, A. D. Goulding, D. M. Alexander, F. E. Bauer, W. R. Forman, R. C. Hickox

Dartmouth Scholarship

We explore the origin of mid-infrared (mid-IR) dust extinction in all 20 nearby (z < 0.05) bona fide Compton-thick (N H > 1.5 × 1024 cm–2) active galactic nuclei (AGNs) with hard energy (E > 10 keV) X-ray spectral measurements. We accurately measure the silicate absorption features at λ ~ 9.7 μm in archival low-resolution (R ~ 57-127) Spitzer Infrared Spectrograph spectroscopy, and show that only a minority (≈45%) of nearby Compton-thick AGNs have strong Si-absorption features (S 9.7 = ln (f int/f obs) 0.5) which would indicate significant dust attenuation. The majority (≈60%) are star …

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Confirmation Of 1rxs J165443.5–191620 As An Intermediate Polar And Its Orbital And Spin Periods, S. Scaringi, S. Connolly, J. Patterson, J. R. Thorstensen Mar 2011

Confirmation Of 1rxs J165443.5–191620 As An Intermediate Polar And Its Orbital And Spin Periods, S. Scaringi, S. Connolly, J. Patterson, J. R. Thorstensen

Dartmouth Scholarship

We investigate the physical nature of the X-ray emitting source 1RXS J165443.5−191620 through optical photometry and time-resolved spectroscopy. Optical photometry is obtained from a variety of telescopes all over the world spanning ≈27 days. Additionally, time-resolved spectroscopy is obtained from the MDM observatory.

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Faint X‐Ray Structure In The Crab Pulsar Wind Nebula, F. D. Seward, W. H. Tucker, R. A. Fesen Dec 2006

Faint X‐Ray Structure In The Crab Pulsar Wind Nebula, F. D. Seward, W. H. Tucker, R. A. Fesen

Dartmouth Scholarship

We report on a Chandra observation of the Crab Nebula that gives the first clear view of the faint boundary of the Crab's X-ray-emitting pulsar wind nebula. There is structure in all directions. Fingers, loops, bays, and the south pulsar jet all indicate that either filamentary material or the magnetic field is controlling the relativistic electrons. In general, spectra soften as distance from the pulsar increases but do not change rapidly along linear features. This is particularly true for the pulsar jet. The termination of the jet is abrupt; the east side is close to an [O III] optical filament, …

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Parallaxes And Distance Estimates For 14 Cataclysmic Variable Stars, John R. Thorstensen Dec 2003

Parallaxes And Distance Estimates For 14 Cataclysmic Variable Stars, John R. Thorstensen

Dartmouth Scholarship

I used the 2.4 m Hiltner Telescope at MDM Observatory in an attempt to measure trigonometric parallaxes for 14 cataclysmic variable stars. Techniques are described in detail. In the best cases the parallax uncertainties are below 1 mas, and significant parallaxes are found for most of the program stars. A Bayesian method that combines the parallaxes together with proper motions and absolute magnitude constraints is developed and used to derive distance estimates and confidence intervals. The most precise distance derive here is for WZ Sge, for which I find 43: 3.1:6 1:5 pc. Six Luyten Half-Second stars with previous precise …

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Redshift-Distance Survey Of Early-Type Galaxies: Circular-Aperture Photometry, M. V. Alonso, M. Bernardi, L. N. Da Costa, G. Wegner May 2003

Redshift-Distance Survey Of Early-Type Galaxies: Circular-Aperture Photometry, M. V. Alonso, M. Bernardi, L. N. Da Costa, G. Wegner

Dartmouth Scholarship

We present R -band CCD photometry for 1332 early-type galaxies, observed as part of the ENEAR survey of peculiar motions using early-type galaxies in the nearby universe. Circular apertures are used to trace the surface brightness profiles, which are then fitted by a two-component bulge-disk model. From the fits, we obtain the structural parameters required to estimate galaxy distances using the Dn - and fundamental plane relations. We find that about 12% of the galaxies are well represented by a pure r1/4 law, while 87% are best fitted by a two-component model. There are 356 repeated observations of 257 galaxies …

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Chandra Observations Of The Luminous, Oxygen‐Rich Supernova Remnants In The Irregular Galaxy Ngc 4449, Daniel J. Patnaude, Robert A. Fesen Apr 2003

Chandra Observations Of The Luminous, Oxygen‐Rich Supernova Remnants In The Irregular Galaxy Ngc 4449, Daniel J. Patnaude, Robert A. Fesen

Dartmouth Scholarship

An analysis of a 29 ks Chandra ACIS-S observation of the young, Cassiopeia A–like supernova remnant in the irregular galaxy NGC 4449 is presented. The observed 0.5–2.1 keV spectrum reveals the likely presence of several emission lines. A nonequilibrium ionization fit to the spectrum suggests an overabundance of oxygen around 20 times solar, consistent with the remnant’s UV and optical emission-line properties. We discuss the remnant’s approximate X-ray–derived elemental abundances and compare its X-ray spectrum and luminosity with other oxygen-rich remnants

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An Isolated, Recently Shocked Ism Cloud In The Cygnus Loop Supernova Remnant, D. J. Patnaude, R. A. Fesen, J. C. Raymond, N. A. Levenson Oct 2002

An Isolated, Recently Shocked Ism Cloud In The Cygnus Loop Supernova Remnant, D. J. Patnaude, R. A. Fesen, J. C. Raymond, N. A. Levenson

Dartmouth Scholarship

Spatially resolved ROSAT X-ray and ground-based optical data for the southwestern region of the Cygnus Loop supernova remnant (SNR) reveal in unprecedented detail the very early stages of a blast-wave interaction with an isolated interstellar cloud. Numerous internal cloud shock fronts near the upstream flow and along the cloud edges are visible optically as sharp filaments of enhanced H emission. Faint X-ray emission is seen along a line of Balmer-dominated shock filaments north and south of the cloud with an estimated X-ray gas temperature of 1.2 106 K (0.11 keV), corresponding to a shock velocity of 290 km s1 . …

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Mass Profile Of The Infall Region Of The Abell 2199 Supercluster, K. Rines, M. J. Geller, A. Diaferio, A. Mahdavi, J. J. Mohr, G. Wegner Sep 2002

Mass Profile Of The Infall Region Of The Abell 2199 Supercluster, K. Rines, M. J. Geller, A. Diaferio, A. Mahdavi, J. J. Mohr, G. Wegner

Dartmouth Scholarship

Using a redshift survey of 1323 galaxies (1092 new or remeasured) in a region of 95 deg2 centered on the nearby galaxy cluster Abell 2199, we analyze the supercluster containing A2199, A2197, and an X-ray group. The caustic technique accurately reproduces the true mass profiles of simulated simple superclusters (i.e., superclusters for which the virial mass of one cluster is 2–10 times the virial mass of all other clusters in the supercluster). We calculate the masses of the two main components of A2197 (A2197W and A2197E) by using archival X-ray observations and demonstrate that the A2199 supercluster is simple (the …

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Redshift-Distance Survey Of Early-Type Galaxies. I. The Enearc Cluster Sample*, M. Bernardi, M. V. Alonso, L. N. Da Costa, C. N. A. Willmer, A. Wegner Jun 2002

Redshift-Distance Survey Of Early-Type Galaxies. I. The Enearc Cluster Sample*, M. Bernardi, M. V. Alonso, L. N. Da Costa, C. N. A. Willmer, A. Wegner

Dartmouth Scholarship

This paper presents data on the ENEARc subsample of the larger ENEAR survey of nearby early-type galaxies. The ENEARc galaxies belong to clusters and were specifically chosen to be used for the construction of a D-n-sigma template. The ENEARc sample includes new measurements of spectroscopic and photometric parameters (redshift, velocity dispersion, line index Mg-2, and the angular diameter d(n)), as well as data from the literature. New spectroscopic data are given for 229 cluster early-type galaxies in 28 clusters. Objective criteria, based on catalogs of groups of galaxies derived from complete redshift surveys of the nearby universe, are used to …

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Starbursts Versus Truncated Star Formation In Nearby Clusters Of Galaxies, James A. Rose, Alejandro E. E. Gaba, Nelson Caldwell, Brian Chaboyer Feb 2001

Starbursts Versus Truncated Star Formation In Nearby Clusters Of Galaxies, James A. Rose, Alejandro E. E. Gaba, Nelson Caldwell, Brian Chaboyer

Dartmouth Scholarship

We present long-slit spectroscopy, B - and R -bandpass imaging, and 21 cm observations of a sample of early-type galaxies in nearby clusters, which are known to be either in a star-forming phase or to have had star formation that recently terminated. From the long-slit spectra, obtained with the Blanco 4 m telescope, we ‹nd that emission lines in the star-forming cluster galaxies are signi‹cantly more centrally concentrated than in a sample of ‹eld galaxies. The broadband imaging reveals that two currently starforming early-type galaxies in the Pegasus I cluster have blue nuclei, again indicating that recent star formation has …

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A Photometric And Kinematic Study Of Awm 7, Daniel M. Koranyi, Margaret Geller, Joseph J. Mohr, Gary Wegner Nov 1998

A Photometric And Kinematic Study Of Awm 7, Daniel M. Koranyi, Margaret Geller, Joseph J. Mohr, Gary Wegner

Dartmouth Scholarship

We have measured redshifts and Kron-Cousins R-band magnitudes for a sample of galaxies in the poor cluster AWM 7. We have measured redshifts for 172 galaxies; 106 of these are cluster members. We determine the luminosity function (LF) from a photometric survey of the central 1.2 × 1.2 h-1 Mpc. The LF has a bump at the bright end and a faint-end slope of α = -1.37 ± 0.16, populated almost exclusively by absorption-line galaxies. The cluster velocity dispersion is lower in the core (~530 km s-1) than at the outskirts (~680 km s-1), …

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