The Metallicity-Luminosity Relation, Effective Yields, and Metal Loss in Spiral and Irregular Galaxies

I present results on the correlation between galaxy mass, luminosity, and metallicity for a sample of spiral and irregular galaxies having well-measured abundance profiles, distances, and rotation speeds. Additional data for low surface brightness galaxies from the literature are also included for comparison. These data are combined to study the metallicity-luminosity and metallicity-rotation speed correlations for spiral and irregular galaxies. The metallicity luminosity correlation shows its familiar form for these galaxies, a roughly uniform change in the average present-day O/H abundance of about a factor 100 over 11 magnitudes in B luminosity. However, the O/H - V(rot) relation shows a change in slope at a rotation speed of about 125 km/sec. At faster V(rot), there appears to be no relation between average metallicity and rotation speed. At lower V(rot), the metallicity correlates with rotation speed. This change in behavior could be the result of increasing loss of metals from the smaller galaxies in supernova-driven winds. This idea is tested by looking at the variation in effective yield, derived from observed abundances and gas fractions assuming closed box chemical evolution. The effective yields derived for spiral and irregular galaxies increase by a factor of 10-20 from V(rot) approximately 5 km/sec to V(rot) approximately 300 km/sec, asympotically increasing to approximately constant y(eff) for V(rot) > 150 km/sec. The trend suggests that galaxies with V(rot) < 100-150 km/sec may lose a large fraction of their SN ejecta, while galaxies above this value tend to retain metals.Comment: 40 pages total, including 7 encapsulated postscript figures. Accepted for publication in 20 Dec 2002 Ap

A quest for Q fever

International audienceA 9-year-old girl was admitted to our hospital with status epilepticus. Earlier in the day, she had complained of a headache and started vomiting. She then lost consciousness and began having a fit; the status epilepticus lasted 30 min and was stopped by phenobarbital. She had a congenital heart defect—truncus arteriosus with interventricular communication—which was surgically corrected a few days after birth. The girl was on long-term treatment with low-dose aspirin as the antiaggregant. She had no features of Marfan's or Ehlers–Danlos syndromes. Laboratory investigations showed leucopenia, low platelet count, and anaemia. Her C-reactive protein (CRP) was 45 mg/L and her erythrocyte sedimentation rate (ESR) was 50 mm/h. Her liver enzymes were also slightly raised. A CT scan of her brain showed an intraparenchymal haematoma and intraventricular haemorrhage. Three-vessel arteriography showed a right Sylvian artery aneurysm (figure). Successive blood cultures and broad-range 16S recombinant DNA PCR—as well as PCR for herpes simplex viruses 1–5—were all negative. At this stage, our working diagnosis was endocarditis leading to the mycotic cerebral aneurysm, despite no signs of a fever. We drained the haematoma and commenced treatment with antibiotics; 2 days later, we embolised the aneurysm. The patient recovered and had a mild, left-sided hemiparesis when she left hospital after 4 weeks

Sea level at Saint Paul Island, southern Indian Ocean, from 1874 to the present

International audienceA data archeology exercise was carried out on sea level observations recorded during the transit of Venus across the Sun observed in 1874 from Saint Paul Island (38°41′S, 77°31 E) in the southern Indian Ocean. Historical (1874) and recent (1994-2009) sea level observations were assembled into a consistent time series. A thorough check of the data and its precise geodetic connection to the same datum was only possible thanks to the recent installation of new technologies (GPS buoy and radar water level sensor) and leveling campaigns. The estimated rate of relative sea level change, spanning the last 135 years at Saint Paul Island, was not significantly different from zero (−0.1 ± 0.3 mm yr−1), a value which could be reconciled with estimates of global average sea level rise for the 20th century assuming the DORIS vertical velocity estimate at Amsterdam Island (100 km distant) could be applied to correct for the land motion at the tide gauge. Considering the scarcity of long-term sea level data in the Southern Hemisphere, the exercise provides an invaluable additional observational constraint for further investigations of the spatial variability of sea level change, once vertical land rates can be determined