Inhomogeneous metal enrichment at z \sim 1.9: the Lyman limit systems in the spectrum of the HDF-S quasar

We present a detailed analysis of three metal absorption systems observed in the spectrum of the HDF-South quasar J2233-606 (z_em = 2.238), taking advantage of new VLT-UVES high resolution data (R=45000, S/N = 40-60, \lambda\lambda 3050-10000 \AA). Three main components, spanning about 300 km/s, can be individuated in the Lyman limit system at z~1.92. They show a surprisingly large variation in metallicities, respectively ~1/500, 1/8 and 1/100 solar. The large value found for the second component at z=1.9259, suggests that the line of sight crosses a star-forming region. In addition, there is a definite correlation between velocity position and ionisation state in this component, which we interpret as a possible signature of an expanding H II region. The systems at z~1.94 and z~1.87 have also high metallicity, ~1/4 and 1/3 solar. We find that photoionisation and collisional ionisation are equal alternatives to explain the high excitation phase revealed by O VI absorption, seen in these two systems. From the width of the Si IV, C IV, Si III and C III lines in the system at z~1.87, we can estimate the temperature of the gas to be log T ~ 4.7, excluding collisional ionisation. Finally, we compute the Si IV/C IV ratio for all Voigt profile components in a sample of log N(C IV) > 14 systems at z < 2. The values show a dispersion of more than an order of magnitude and most of them are much larger than what is observed for weaker systems. This is probably an indication that high column density systems preferably originate in galactic halos and are mostly influenced by local ionising sources.Comment: 11 pages, 11 figures, accepted by A&A main journa

Multiwavelength investigation of a near-solar metallicity sub-DLA at z =1.3647 towards PKS 0237-233

We searched for 21-cm absorption associated with the z_abs = 1.3647 absorption system toward PKS 0237-233 using the GMRT. A high quality UVES spectrum shows that C I and C I* are detected at this redshift together with C II*, Mg I, Mg II, Si II, Al II, Fe II and Mn II. The complex profiles, spread over ~300 km/s, are fitted with 21 Voigt profile components. None of these components are detected in 21-cm absorption down to a detection limit of \tau(3\sigma)\le 3x10^{-3} (or N(HI)/T_S <10^{17} cm ^-2 K^-1). We derive log N(HI)<19.30$\pm$0.30 using the Lyman alpha absorption line detected in the IUE spectrum of the quasar. Mg II, Si II and Al II column densities are consistent with near solar metallicity and we measure [O/H]>-0.33. Using photoionization models constrained by the fine-structure excitations of C I and C II, and the 21-cm optical depth, we show that the C I absorption arises predominantly either in WIM or WNM in ionization and thermal equilibrium with the meta-galactic UV background dominated by QSOs and star forming galaxies. The estimated thermal pressure of the gas is of the same order of magnitude over different velocity ranges through the absorption profile (2.6\le log [P/k cm^{-3} K]\le 4.0). The gas-phase metallicity corrected for ionization is Z>0.5 Z_\odot with a signature of Fe co-production elements being under abundant compared to \alpha-process elements by ~0.5 dex. At z>1.9, C I absorption is usually associated with H_2 absorption arising from cold gas in DLAs. This system and the z=2.139 toward Tol 1037-270 are the only two systems known which show that C I absorption can also be detected in warm gas provided the metallicity is high enough. Interestingly, both the systems are part of unusual concentrations of absorption lines.Comment: 12 pages, 9 figures, accepted for publication in MNRA

Auguste Chevalier, Paul Le Cointe et l'Amazonie.: Les plantes utiles entre la botanique coloniale et l'ethnobotanique.

Version provisoire, avant révision pour publicationReprésentatifs du tournant colonial du Muséum national d'histoire naturelle à la fin du XIXe siècle, Auguste Chevalier et Paul Le Cointe ont suivi des carrières opposées. Le premier, dans la métropole, au centre de réseaux, sera la figure marquante de la botanique coloniale, jusqu'à présider l'Académie des sciences. Le second, installé en Amazonie pendant plus d'un demi-siècle produira une oeuvre géographique, botanique et chimique majeure, qu'il diffusera à travers les sociétés de géographie et la revue de Chevalier, recueillant de nombreux prix pour son ouvrage "L'Amazonie brésilienne". Chevalier et Le Cointe ont partagé le même intérêt pour les plantes utiles et les connaissances populaires.Auguste Chevalier e Paul Le Cointe são típicos do torno colonial do Muséum national d'histoire naturelle no fim do século 19. Mas seguem carreiras opostas. O primeiro, na metrópole, e no centro de redes científicas, será a figura marcante da botânica colonial, até a presidência da Academie des Sciences. O secundo, radicado na Amazônia durante mas de um médio século, produzira um obra importante de geografia, botânica e química, desusando-la a traves das sociedades de geografia e da revista de Chevalier. Le Cointe fui premiado varias vezes por seu livro l'Amazonie Brésilienne. Chevalier e Le Cointe compartilharon um mesmo interes para as plantas úteis e os saberes populares

The WFSW and Unesco in the late 1940s

A l'occasion du 60e anniversaire de l'Unesco, j'ai coordonné la première partie d'un ouvrage sur l'histoire du secteur des sciences naturelles à l'Unesco, Sixty years of Sciences at Unesco, principalement écrit par des fonctionnaires, retraités ou en activité du secteur des sciences de l'Unesco. Cette première partie concerne les 20 premières années (1945-1965). J'en ai écrit une grande partie, en coopération avec des historiens des sciences, l'introduction et neuf sections, soit 10 dépôts dans HAL, dans les versions qui précèdent l'édition finale. Le livre a été publié en novembre 2006, aux Éditions de l'Unesco : http://publishing.unesco.org/details.aspx?Code_Livre=4503The left-sided scientists, most of them being in fact British or French, established the World Federation of Scientific Workers (WFSW) in July 1946, when UNESCO was "a work in progress". UNESCO's science division and the WFSW had the same roots in the Social relations of Science Movement of the 1930s. Initially, the WFSW (Joliot and Bernal) and UNESCO (Needham and Huxley) were conceived as complementary. But the Cold War provoked an American hostility to the WFSW and a Russian hostility to UNESCO. Needham hoped an agreement between the WFSW and UNESCO similar to the one with the ICSU, but only obtained a limited one in July 1947, which was suppressed already in June 1950 following an American pression.The following text is the section (1st part of the book) dedicated to the first years of the failed partnership between UNESCO and the WFSW.Les scientifiques progressistes, principalement anglais et français, ont créé la Fédération Mondiale des Travailleurs Scientifiques (FMTS) en juillet 1946, en même temps que l'Unesco. La FMTS avait les mêmes racines que la division des sciences de l'Unesco dans le mouvement pour les relations sociales de la science des années 1930. La FMTS (Joliot, Bernal) et l'Unesco (Needham, Huxley) les concevaient à l'origine comme complémentaires. Mais la guerre froide, avec l'hostilité des États-Uniens envers la FMTS et des Russes envers l'Unesco allait bloquer une coopération entre les deux organismes. Needham souhaitait un accord identique à celui passé entre l'Unesco et l'ICSU, mais n'obtint qu'un accord limité en juillet 1947, supprimé dès juin 1950 sous pression des États-Uniens.Le texte qui suit est la section (première partie du livre) consacrée à l'échec initial du partenariat entre l'Unesco et la FMT