Excitation and Disruption of a Giant Molecular Cloud by the Supernova Remnant 3C391

Using the IRAM 30-m telescope, we observed the supernova remnant 3C 391 (G31.9+0.0) and its surroundings in the CO(2-1), HCO+(1-0), CS(2-1), CS(3-2), and CS(5-4) lines. The ambient molecular gas at the distance (9 kpc) of the remnant comprises a giant molecular cloud whose edge is closely parallel to a ridge of bright non-thermal radio continuum, which evidently delineates the blast-wave into the cloud. We found that in a small (0.6 pc) portion of the radio shell, the molecular line profiles consist of a narrow (2 km/s) component, plus a very wide (> 20 km/s) component. Both spectral components peak within 20" of a previously-detected OH 1720 MHz maser. We name this source 3C 391:BML (broad molecular line); it provides a new laboratory, similar to IC 443 but on a larger scale, to study shock interactions with dense molecular gas. The wide spectral component is relatively brighter in the higher-excitation lines. We interpret the wide spectral component as post-shock gas, either smoothly accelerated or partially dissociated and reformed behind the shock. The narrow component is either the pre-shock gas or cold gas reformed behind a fully dissociative shock. Using the 3 observed CS lines, we measured the temperature, CS column density, and H2 volume density in a dense clump in the parent molecular cloud as well as the wide-line and narrow-line portions of the shocked clump. The physical conditions of the narrow-line gas are comparable to the highest-density clumps in the giant molecular cloud, while the wide-line gas is both warmer and denser. The mass of compressed gas in 3C 391:BML is high enough that its self-gravity is significant, and eventually it could form one or several stars

Molecular and Ionic shocks in the Supernova Remnant 3C391

New observations of the supernova remnant 3C391 are in the H2 2.12 micron and [Fe II] 1.64 micron narrow-band filters at the Palomar 200-inch telescope, and in the 5-15 micron CVF on ISOCAM. Shocked H2 emission was detected from the region 3C391:BML, where broad millimeter CO and CS lines had previously been detected. A new H2 clump was confirmed to have broad CO emission, demonstrating that the near-infrared H2 images can trace previously undetected molecular shocks. The [Fe II] emission has a significantly different distribution, being brightest in the bright radio bar, at the interface between the supernova remnant and the giant molecular cloud, and following filaments in the radio shell. The near-infrared [Fe II] and the mid-infrared 12-18 micron filter images are the first images to reveal the radiative shell of 3C391. The mid-infrared spectrum is dominated by bright ionic lines and H2 S(2) through S(7). There are no aromatic hydrocarbons associated with the shocks, nor is their any mid-infrared continuum, suggesting that macromolecules and very small grains are destroyed. Comparing 3C391 to the better-studied IC443, both remnants have molecular- and ionic-dominated regions; for 3C391, the ionic-dominated region is the interface into the giant molecular cloud, showing that the main bodies of giant molecular clouds contain significant regions with densities 100 to 1000/cm^3 and a small filling factor with higher-density. The molecular shocked region resolves into 16 clumps of H2 emission, with some fainter diffuse emission but with no associated near-infrared continuum sources. One of the clumps is coincident with a previously-detected OH 1720 MHz maser. These clumps are interpreted as a cluster of pre-stellar, dense molecular cores that are presently being shocked by the supernova blast wave

Adjusting insulin doses : from knowledge to decision

The aim of this study was to analyze the absence of adjustment of insulin doses in type 1 diabetic patients with poorly controlled diabetes. Twenty-eight patients (HbA1c higher than 8.5% during the last 6 months, performing at least three capillary blood glucose determinations per day), completed a questionnaire on the degree of confidence in their own knowledge, the nature of their health beliefs, their fear of hypoglycemia, their own appreciation on how they adjust their insulin doses (subjective score). An analysis of their diabetes logbook provided an objective score of the adjustment of doses actually performed. The results show that the subjective and objective scores of adjustment were not significantly correlated. Further there was a significant negative correlation between the score of uncertainty on knowledge and the subjective score of adjustment of the insulin doses, but not with the objective score. There was a significant correlationbetween the score of positive health beliefs and the subjective score of adjustment of the insulin doses, but not with the objective score. No correlation was found between the score of fear of hypoglycemia and the subjective score of adjustment of the insulin doses. Correlation with the objective score was higher, but not significant. Actually, the fear of hypoglycemia was the most frequently given reason for not adjusting the insulin doses, when the question was asked to the patients with an open answer. This study illustrates the difference between thinking and doing. It also shows that the degree of confidence in one’s own knowledge, the health beliefs, and the fear of hypoglycemia differently influence the perception that the patients have of their behavior, and what they really do. © 2004 Elsevier Ireland Ltd. All rights reserved

Exclusion of Tiny Interstellar Dust Grains from the Heliosphere

The distribution of interstellar dust grains (ISDG) observed in the Solar System depends on the nature of the interstellar medium-solar wind interaction. The charge of the grains couples them to the interstellar magnetic field (ISMF) resulting in some fraction of grains being excluded from the heliosphere while grains on the larger end of the size distribution, with gyroradii comparable to the size of the heliosphere, penetrate the termination shock. This results in a skewing the size distribution detected in the Solar System. We present new calculations of grain trajectories and the resultant grain density distribution for small ISDGs propagating through the heliosphere. We make use of detailed heliosphere model results, using three-dimensional (3-D) magnetohydrodynamic/kinetic models designed to match data on the shape of the termination shock and the relative deflection of interstellar neutral H and He flowing into the heliosphere. We find that the necessary inclination of the ISMF relative to the inflow direction results in an asymmetry in the distribution of the larger grains (0.1 micron) that penetrate the heliopause. Smaller grains (0.01 micron) are completely excluded from the Solar System at the heliopause.Comment: 5 pages, 5 figures, accepted for publication in the Solar Wind 12 conference proceeding

Candidates for asteroid dust trails

The contribution of different sources to the circumsolar dust cloud (known as the zodiacal cloud) can be deduced from diagnostic observations. We used the Spitzer Space Telescope to observe the diffuse thermal emission of the zodiacal cloud near the ecliptic. Several structures were identified in these observations, including previously known asteroid dust bands, which are thought to have been produced by recent asteroid collisions, and cometary trails. Interestingly, two of the detected dust trails, denoted t1 and t2 here, cannot be linked to any known comet. Trails t1 and t2 represent a much larger integrated brightness than all known cometary trails combined and may therefore be major contributors to the circumsolar dust cloud. We used our Spitzer observations to determine the orbits of these trails and were able to link them to two ("orphan" or type II) trails that were discovered by the Infrared Astronomical Satellite (IRAS) in 1983. The orbits of trails t1 and t2 that we determined by combining the Spitzer and IRAS data have semimajor axes, eccentricities, and inclinations like those of the main-belt asteroids. We therefore propose that trails t1 and t2 were produced by very recent (<~100 kyr old) collisional breakups of small, <~10 km diameter main-belt asteroids

On the Unusual Depletions toward Sk 155, or What Are the Small Magellanic Cloud Dust Grains Made of?

The dust in the Small Magellanic Cloud (SMC), an ideal analog of primordial galaxies at high redshifts, differs markedly from that in the Milky Way by exhibiting a steeply rising far-ultraviolet extinction curve, an absence of the 2175 Angstrom extinction feature, and a local minimum at ~12 micron in its infrared emission spectrum, suggesting the lack of ultrasmall carbonaceous grains (i.e. polycyclic aromatic hydrocarbon molecules) which are ubiquitously seen in the Milky Way. While current models for the SMC dust all rely heavily on silicates, recent observations of the SMC sightline toward Sk 155 indicated that Si and Mg are essentially undepleted and the depletions of Fe range from mild to severe, suggesting that metallic grains and/or iron oxides, instead of silicates, may dominate the SMC dust. However, in this Letter we apply the Kramers-Kronig relation to demonstrate that neither metallic grains nor iron oxides are capable of accounting for the observed extinction; silicates remain as an important contributor to the extinction, consistent with current models for the SMC dust.Comment: 12 pages, 3 figures; The Astrophysical Journal Letters, in pres

The Rich Mid-Infrared Environments of Two Highly-Obscured X-ray Binaries: Spitzer Observations of IGR J16318-4848 and GX 301-2

We present the results of Spitzer mid-infrared spectroscopic observations of two highly-obscured massive X-ray binaries: IGR J16318-4848 and GX301-2. Our observations reveal for the first time the extremely rich mid-infrared environments of this type of source, including multiple continuum emission components (a hot component with T > 700 K and a warm component with T ~ 180 K) with apparent silicate absorption features, numerous HI recombination lines, many forbidden ionic lines of low ionization potentials, and pure rotational H2 lines. This indicates that both sources have hot and warm circumstellar dust, ionized stellar winds, extended low-density ionized regions, and photo-dissociated regions. It appears difficult to attribute the total optical extinction of both sources to the hot and warm dust components, which suggests that there could be an otherwise observable colder dust component responsible for the most of the optical extinction and silicate absorption features. The observed mid-infrared spectra are similar to those from Luminous Blue Variables, indicating that the highly-obscured massive X-ray binaries may represent a previously unknown evolutionary phase of X-ray binaries with early-type optical companions. Our results highlight the importance and utility of mid-infrared spectroscopy to investigate highly-obscured X-ray binaries.Comment: To appear in ApJ Letter

Detailed compositional analysis of the heavily polluted DBZ white dwarf SDSS J073842.56+183509.06: A window on planet formation?

We present a new model atmosphere analysis of the most metal contaminated white dwarf known, the DBZ SDSS J073842.56+183509.06. Using new high resolution spectroscopic observations taken with Keck and Magellan, we determine precise atmospheric parameters and measure abundances of 14 elements heavier than helium. We also report new Spitzer mid-infrared photometric data that are used to better constrain the properties of the debris disk orbiting this star. Our detailed analysis, which combines data taken from 7 different observational facilities (GALEX, Gemini, Keck, Magellan, MMT, SDSS and Spitzer) clearly demonstrate that J0738+1835 is accreting large amounts of rocky terrestrial-like material that has been tidally disrupted into a debris disk. We estimate that the body responsible for the photospheric metal contamination was at least as large Ceres, but was much drier, with less than 1% of the mass contained in the form of water ice, indicating that it formed interior to the snow line around its parent star. We also find a correlation between the abundances (relative to Mg and bulk Earth) and the condensation temperature; refractory species are clearly depleted while the more volatile elements are possibly enhanced. This could be the signature of a body that formed in a lower temperature environment than where Earth formed. Alternatively, we could be witnessing the remains of a differentiated body that lost a large part of its outer layers.Comment: 16 pages, 17 figures, accepted for publication in The Astrophysical Journa

Shocked Molecular Gas in the Supernova Remnant HB 21

We report the discovery of the shocked molecular gas in the supernova remnant HB 21. We derive the physical parameters of the shocked gas from CO J=1-0 and J=2-1 line observations. We discuss the correlation of the shocked molecular gas with the previously detected, shocked atomic gas and the associated infrared emission.Comment: 24 pages, 10 figures, To appear in the ApJ, scheduled for the April 10, 2001 issue (v551