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

Science and the “Civilizing Mission”: <br />France and the Colonial Enterprise

Which part was played by science in the French “civilizing mission” ? From the 1880s, the interests of science were combined with those of national prestige. Colonization was undertaken in the name of science. To civilize, in official French colonial ideology, was to bring the benefits of science, just as for other countries, it was to bring the benefits of religion or free trade. The “civilizing mission” thus managed to combine elements of Eurocentrism and scientism. It represented a cultural consensus from the 1880s until the 1930s, and conditioned many generations of French scientists in their training, in their scientific practices, and in their mentalities. Many societies and institutions were established to organize colonial scientific activities : learned societies (Geographical Society, Anthropological Society, and so on), the Association Science and Colonies, the Colonial Academy of Science, the Colonila Scientific Congresses,...The aim of this essay is to analyse this colonial function of science, far to be only a technical tool. It is to describe how it occupied such a central part in colonial ideology and policy from the 1880s, with the name of "civilizing mission"

Quand la politique interpelle les historiens des sciences. L'Académie Internationale d'Histoire des Sciences dans les années 1930 et 1940

Communication présentée à l'Université de Lille en mai 2007 lors du symposium organisé par la Société Française d'Histoire des Sciences et des techniques "Quelle histoire font les historiens des sciences ? État des lieux des méthodes en histoire des sciences et des techniques ". En cours de publication dans les Actes.Les congrès internationaux d'histoire des sciences ont rarement été à l'abri des controverses politiques ou sociales, notamment dans les années 1930 et 1940. L'Académie internationale d'histoire des sciences, organisatrice des premiers congrès, n'a pu échapper aux débats publics sur le fascisme ou sur la fonction sociale de la science et de l'histoire des sciences. Le cas du 2e congrès (Londres, 1931) a été très étudié, avec la présence d'une délégation soviétique dirigée par Boukharine. Le 3e congrès, programmé à Berlin pour 1934, a été déplacé au Portugal après d'âpres débats. Le 4e a eu lieu en 1937 à Prague. Après une interruption pendant la guerre, le 5e congrès (Lausanne 1947) a vu la création de l'Union internationale d'histoire des sciences, avec une commission "histoire des relations sociales de la science" (Léon Rosenfeld, Samuel Lilley) sous la pression politique de l'Unesco, et plus particulièrement de Joseph Needham et de ses amis progressistes