Progressing diversity in HRD theory and practice

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Karen Students’ Social and Academic Experiences in Minnesota K-12 Schools

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Observations of Outflowing UV Absorbers in NGC 4051 with the Cosmic Origins Spectrograph

We present new Hubble Space Telescope (HST)/Cosmic Origins Spectrograph observations of the Narrow-Line Seyfert 1 galaxy NGC 4051. These data were obtained as part of a coordinated observing program including X-ray observations with the Chandra/High Energy Transmission Grating (HETG) Spectrometer and Suzaku. We detected nine kinematic components of UV absorption, which were previously identified using the HST/Space Telescope Imaging Spectrograph. None of the absorption components showed evidence for changes in column density or profile within the \sim 10 yr between the STIS and COS observations, which we interpret as evidence of 1) saturation, for the stronger components, or 2) very low densities, i.e., n_H < 1 cm^-3, for the weaker components. After applying a +200 km s^-1 offset to the HETG spectrum, we found that the radial velocities of the UV absorbers lay within the O VII profile. Based on photoionization models, we suggest that, while UV components 2, 5 and 7 produce significant O VII absorption, the bulk of the X-ray absorption detected in the HETG analysis occurs in more highly ionized gas. Moreover, the mass loss rate is dominated by high ionization gas which lacks a significant UV footprint.Comment: 41 pages, 10 Figures; accepted for publication in the Astrophysical Journa

Transcapillary fluid shifts in head and neck tissues during and after simulated microgravity

To understand the mechanism, magnitude, and time course of facial puffiness that occurs in microgravity, seven male subjects were tilted 6 degrees head down for 8 hr, and all four Starling transcapillary pressures were directly measured before, during, and after tilt. Head-down tilt (HDT) caused facial edema and a significant elevation of microvascular pressures measured in the lower lip: capillary pressures increased from 27.2 +/- 5 mm Hg pre-HDT to 33.9 +/- 1.7 mm Hg by the end of tilt. Subcutaneous and intramuscular interstitial fluid pressures in the neck also increased as a result of HDT, while interstitial fluid colloid osmotic pressures remained unchanged. Plasma colloid osmotic pressures dropped significantly after 4 hr of HDT, suggesting a transition from fluid filtration to absorption in capillary beds between the heart and feet during HDT. After 4 hr of seated recovery from HDT, microvascular pressures remained significantly elevated by 5 to 8 mm Hg above baseline values, despite a significant HDT diuresis and the orthostatic challenge of an upright, seated posture. During the control (baseline) period, urine output was 46.7 ml/hr; during HDT, it was 126.5 ml/hr. These results indicate that facial edema resulting from HDT is primarily caused by elevated capillary pressures and decreased plasma colloid osmotic pressures. Elevation of cephalic capillary pressures sustained for 4 hr after HDT suggests that there is a compensatory vasodilation to maintain microvascular perfusion. The negativity of interstitial fluid pressures above heart level also has implications for the maintenance of tissue fluid balance in upright posture

Significant X-ray Line Emission in the 5-6 keV band of NGC 4051

A Suzaku X-ray observation of NGC 4051 taken during 2005 Nov reveals line emission at 5.44 keV in the rest-frame of the galaxy which does not have an obvious origin in known rest-frame atomic transitions. The improvement to the fit statistic when this line is accounted for establishes its reality at >99.9% confidence: we have also verified that the line is detected in the three XIS units independently. Comparison between the data and Monte Carlo simulations shows that the probability of the line being a statistical fluctuation is p < 3.3 x 10^-4. Consideration of three independent line detections in Suzaku data taken at different epochs yields a probability p< 3 x 10^-11 and thus conclusively demonstrates that it cannot be a statistical fluctuation in the data. The new line and a strong component of Fe Ka emission from neutral material are prominent when the source flux is low, during 2005. Spectra from 2008 show evidence for a line consistent with having the same flux and energy as that observed during 2005, but inconsistent with having a constant equivalent width against the observed continuum. The stability of the line flux and energy suggests that it may not arise in transient hotspots, as has been suggested for similar lines in other sources, but could arise from a special location in the reprocessor, such as the inner edge of the accretion disk. Alternatively, the line energy may be explained by spallation of Fe into Cr, as discussed in a companion paper.Comment: 18 pages, accepted for publication by Ap

Simultaneous X-ray and Ultraviolet spectroscopy of the Seyfert galaxy NGC 5548. III. X-ray time variability

The Seyfert 1 galaxy NGC 5548 was observed for a week by Chandra using both the HETGS and LETGS spectrometers. In this paper we study the time variability of the continuum radiation. During our observation, the source showed a gradual increase in flux over four days, followed by a rapid decrease and flattening of the light curve afterwards. Superimposed upon these relatively slow variations several short duration bursts or quasi-periodic oscillations occured with a typical duration of several hours and separation between 0.6-0.9 days. The bursts show a delay of the hard X-rays with respect to the soft X-rays of a few hours. We interprete these bursts as due to a rotating, fluctuating hot spot at approximately 10 gravitational radii; the time delay of the hard X-rays from the bursts agree with the canonical picture of Inverse Compton scattering of the soft accretion disk photons on a hot medium that is relatively close to the central black hole.Comment: 6 pages, 7 figures, accepted for publication in Astronomy and Astrophysic

Tennessee’s Unique Religious Protections in Employment: Do They Mean What They Say?

Tennessee has a long history of strongly held and diverse religious beliefs and practices. Equally firmly established is its “at-will” employment rule that allows businesses to create and control their workforces to maximize operations and profits to the benefit of employers and employees. When an employee’s religious beliefs conflict with his obligations to his employer, state and federal laws resolve the tension. Employees who experience this tension and feel they have been discriminated against based on their religion generally have the choice to bring their claims of discrimination under federal law, state law, or both. Because claims under federal law may be removed to federal court, and because state courts are generally perceived to be more favorable to employees, some employees strategically elect to pursue only selected state law claims. An employee might also be forced to bring a claim only under state law if she works for a small employer, since the federal law’s reach is limited to employers with at least fifteen employees. This Article examines whether a Tennessee employee who brings claims only under Tennessee’s statutory protection against religious discrimination in employment has the same protections as he would if he proceeded under federal law. Part I discusses employers’ obligations under the Tennessee Human Rights Act (“THRA”), the primary Tennessee religious anti-discrimination statute, and Title VII of the Civil Rights Act of 1964 (“Title VII”), the primary federal religious anti-discrimination law. Part II discusses the background of both the THRA and Title VII and how it informs the analysis. Part III proposes that the THRA not be interpreted to import the reasonable accommodation requirement from Title VII. This interpretation is consistent with the textual language of the statute, courts’ interpretation of the Tennessee Disability Act, existing case law, and Tennessee’s history of limiting exceptions to the at-will employment doctrine. The Article proposes that this different interpretation is more consistent with the THRA as it is currently written and invites discussion of whether this interpretation is ultimately better for employees and employers

Interpretation of UV Absorption Lines in SN1006

We present a theoretical interpretation of the broad silicon and iron UV absorption features observed with the Hubble Space Telescope in the spectrum of the Schweizer-Middleditch star behind the remnant of Supernova 1006. These features are caused by supernova ejecta in SN1006. We propose that the redshifted SiII2 1260 A feature consists of both unshocked and shocked SiII. The sharp red edge of the line at 7070 km/s indicates the position of the reverse shock, while its Gaussian blue edge reveals shocked Si with a mean velocity of 5050 km/s and a dispersion of 1240 km/s, implying a reverse shock velocity of 2860 km/s. The measured velocities satisfy the energy jump condition for a strong shock, provided that all the shock energy goes into ions, with little or no collisionless heating of electrons. The line profiles of the SiIII and SiIV absorption features indicate that they arise mostly from shocked Si. The total mass of shocked and unshocked Si inferred from the SiII, SiIII and SiIV profiles is M_Si = 0.25 \pm 0.01 Msun on the assumption of spherical symmetry. Unshocked Si extends upwards from 5600 km/s. Although there appears to be some Fe mixed with the Si at lower velocities < 7070 km/s, the absence of FeII absorption with the same profile as the shocked SiII suggests little Fe mixed with Si at higher (before being shocked) velocities. The column density of shocked SiII is close to that expected for SiII undergoing steady state collisional ionization behind the reverse shock, provided that the electron to SiII ratio is low, from which we infer that most of the shocked Si is likely to be of a fairly high degree of purity, unmixed with other elements. We propose that the ambient interstellar density on the far side of SN1006 is anomalously low compared to the density around the rest of the remnant. ThisComment: 24 pages, with 8 figures included. Accepted for publication in the Astrophysical Journa

Resolved Spectroscopy of the Narrow-Line Region in NGC 1068. I. The Nature of the Continuum Emission

We present the first long-slit spectra of the Seyfert 2 galaxy NGC 1068 obtained by the Space Telescope Imaging Spectrograph (STIS); the spectra cover the wavelength range 1150 - 10,270 Angstroms at a spatial resolution of 0.05 - 0.1 arcsec and a spectral resolving power of 1000. In this first paper, we concentrate on the far-UV to near-IR continuum emission from the continuum ``hot spot'' and surrounding regions extending out to +/- 6 arcsec (+/-432 pc) at a position angle of 202 degrees In addition to the broad emission lines detected by spectropolarimetry, the hot spot shows the ``little blue bump'' in the 2000 - 4000 Ang. range, which is due to Fe II and Balmer continuum emission. The continuum shape of the hot spot is indistinguishable from that of NGC 4151 and other Seyfert 1 galaxies. Thus, the hot spot is reflected emission from the hidden nucleus, due to electron scattering (as opposed to wavelength-dependent dust scattering). The hot spot is ~0.3 arcsec in extent and accounts for 20% of the scattered light in the inner 500 pc. We are able to deconvolve the extended continuum emission in this region into two components: electron-scattered light from the hidden nucleus (which dominates in the UV) and stellar light (which dominates in the optical and near-IR). The scattered light is heavily concentrated towards the hot spot, is stronger in the northeast, and is enhanced in regions of strong narrow-line emission. The stellar component is more extended, concentrated southwest of the hot spot, dominated by an old (> 2 x 10 Gyr) stellar population, and includes a nuclear stellar cluster which is ~200 pc in extent.Comment: 32 pages, Latex, includes 11 figures (postscript), to appear in the Astrophysical Journa