The Progenitor of SN 2005cs in the Whirlpool Galaxy

The progenitor of SN 2005cs, in the galaxy M51, is identified in pre-explosion HST ACS WFC imaging. Differential astrometry, with post-explosion ACS HRC F555W images, permitted the identification of the progenitor with an accuracy of 0.006". The progenitor was detected in the F814W pre-explosion image with I=23.3+/-0.2, but was below the detection thresholds of the F435W and F555W images, with B<24.8 and V<25 at 5-sigma. Limits were also placed on the U and R band fluxes of the progenitor from pre-explosion HST WFPC2 F336W and F675W images. Deep images in the infra-red from NIRI on the Gemini-North telescope were taken 2 months prior to explosion, but the progenitor is not clearly detected on these. The upper limits for the JHK magnitudes of the progenitor were J<21.9,H<21.1 and K<20.7. Despite having a detection in only one band, a restrictive spectral energy distribution of the progenitor star can be constructed and a robust case is made that the progenitor was a red supergiant with spectral type between mid-K to late-M. The spectral energy distribution allows a region in the theoretical HR diagram to be determined which must contain the progenitor star. The initial mass of the star is constrained to be M(ZAMS)=9+3/-2 M_solar, which is very similar to the identified progenitor of the type II-P SN 2003gd, and also consistent with upper mass limits placed on five other similar SNe. The upper limit in the deep K-band image is significant in that it allows us to rule out the possibility that the progenitor was a significantly higher mass object enshrouded in a dust cocoon before core-collapse. This is further evidence that the trend for type II-P SNe to arise in low to moderate mass red supergiants is real.Comment: Accepted (31/08/05) for publication in MNRAS Letter

Fleeing War, Fighting Xenophobia

The purpose of this research is to identify the key differences between German and American refugee policies as they relate to the ability of each country’s native population to successfully integrate refugees into their society. This body of work looks specifically at the German and American Refugee Resettlement Programs submitted to the United Nations. As shown in this research, new legal policy that can fight systematic distrust and discrimination becomes achievable by identifying the practices that contribute to in- and out-group dynamics between host country and refugees. Such policies will allow for the building of stronger, more integrated societies in the future. While Germany and the United States display both strengths and weakness in varying aspects of their respective refugee policies, neither has a significantly superior Refugee Resettlement Program

IUE observations of oxygen-rich supernova remnants

The IUE observations were used to determine the composition of the ejecta (especially C and Si abundances) and to test models for the ionization and excitation of the ejecta of two oxygen-rich supernova remnants (N132D in the Large Magellanic Cloud and 1E 0102-7219 in the Small Magellanic Cloud). Time-dependent photoionization by the EUV and X-ray radiation from 1E 0102-7219 can qualitatively explain its UV and optical line emission, but the density and ionization structures are complex and prevent a unique model from being specified. Many model parameters are poorly constrained, including the time dependence and shape of the ionizing spectrum. Moreover, the models presented are not self-consistent in that the volumes and densities of the optically emitting gas imply optical depths of order unity in the EUV, but absorption of the ionizing radiation was ignored. It is possible that these shortcomings reflect a more fundamental limitation of the model assumptions. It is assumed that the electron velocity distribution is Maxwellian and that the energy deposited by photoionization heats the electrons directly. The 500 eV electrons produced by the Auger process may excite or ionize other ions before they slow down enough to share their energy with other electrons. Many of the excitations would produce photons that could ionize lower ionization stages

Paraphysial Cysts of the Third Ventricle

The radiographic appearances of the third ventricle in 26 patients with colloid cysts, have been reviewed. The constant radiographic features and the invectigations in which the diagnostic yield is good are stressed

Barriers to the Employment of Welfare Recipients

Dramatic reductions in welfare caseloads since passage of the Personal Responsibility and WorkOpportunity Reconciliation Act of 1996 have not allayed policy concerns about the employability of recipients remaining on the rolls. Analysis of potential barriers to employment can address whether current recipients have problems that either singly or in combination make it difficult for them to comply with the new requirements for getting and keeping jobs. In this paper, we explore the prevalence and work effects of 14 potential barriers in a new survey of a representative sample of 753 urban single-mother recipients. We report the prevalence of the barriers and how their number predicts employment rates, controlling for demographic characteristics. We also analyze which individual barriers are associated with employment and how a model inclusive of a comprehensive array of barriers improves upon a traditional human capital model of the work effects of education and work and welfare history. Single mothers who received welfare in 1997 had higher rates of personal health and mental health problems, domestic violence, and children’s health problems than do women in national samples, but they were no more likely than the general population to be drug or alcohol dependent. Only 15 percent of respondents had none of the barriers and almost two-thirds had two or more barriers. The numbers of multiple barriers were strongly and negatively associated with working, and among the individual barriers, low education, lack of access to transportation, poor health, having drug dependence or a major depressive disorder, and several experiences of workplace discrimination reduced employment. Welfare-to-work programs need to be more finely targeted with respect to exemptions and service provision, and states should consider providing longer-term and enhanced supports for those who face low prospects of leaving welfare for employment.

Unravelling the chemical inhomogeneity of PNe with VLT FLAMES integral-field unit spectroscopy

Recent weak emission-line long-slit surveys and modelling studies of PNe have convincingly argued in favour of the existence of an unknown component in the planetary nebula plasma consisting of cold, hydrogen-deficient gas, as an explanation for the long-standing recombination-line versus forbidden-line temperature and abundance discrepancy problems. Here we describe the rationale and initial results from a detailed spectroscopic study of three Galactic PNe undertaken with the VLT FLAMES integral-field unit spectrograph, which advances our knowledge about the small-scale physical properties, chemical abundances and velocity structure of these objects across a two-dimensional field of view, and opens up for exploration an uncharted territory in the study and modelling of PNe and photoionized nebulae in general.Comment: 4 pages; 3 figures; invited paper to appear in proceedings of IAU Symp. No. 234, 2006, Planetary Nebulae in our Galaxy and Beyond (held in Hawaii, April 2006

Dark matter in elliptical galaxies

We present measurements of the shape of the stellar line-of-sight velocity distribution out to two effective radii along the major axes of the four elliptical galaxies NGC 2434, 2663, 3706, and 5018. The velocity dispersion profiles are flat or decline gently with radius. We compare the data to the predictions of f=f(E,L_z) axisymmetric models with and without dark matter. Strong tangential anisotropy is ruled out at large radii. We conclude from our measurements that massive dark halos must be present in three of the four galaxies, while for the fourth galaxy (NGC 2663) the case is inconclusive.Comment: 15 pages, uuencoded compressed PostScript, includes 3 figure