Barnes Hospital Bulletin

https://digitalcommons.wustl.edu/bjc_barnes_bulletin/1041/thumbnail.jp

Discovery Of Cold, Pristine Gas Possibly Accreting Onto An Overdensity Of Star-Forming Galaxies At Redshift z ~ 1.6

We report the discovery of large amounts of cold (T ~ 10^4 K), chemically young gas in an overdensity of galaxies at redshift z ~ 1.6 in the Great Observatories Origins Deep Survey southern field (GOODS-S). The gas is identified thanks to the ultra-strong Mg II absorption features it imprints in the rest-frame UV spectra of galaxies in the background of the overdensity. There is no evidence that the optically-thick gas is part of any massive galaxy (i.e. M_star > 4x10^9 M_sun), but rather is associated with the overdensity; less massive and fainter galaxies (25.5 < z_850 < 27.5 mag) have too large an impact parameter to be causing ultra-strong absorption systems, based on our knowledge of such systems. The lack of corresponding Fe II absorption features, not detected even in co-added spectra, suggests that the gas is chemically more pristine than the ISM and outflows of star-forming galaxies at similar redshift, including those in the overdensity itself, and comparable to the most metal-poor stars in the Milky Way halo. A crude estimate of the projected covering factor of the high-column density gas (N_H >~ 10^20 cm-2) based on the observed fraction of galaxies with ultra-strong absorbers is C_F ~ 0.04. A broad, continuum absorption profile extending to the red of the interstellar Mg II absorption line by <~ 2000 km/s is possibly detected in two independent co-added spectra of galaxies of the overdensity, consistent with a large-scale infall motion of the gas onto the overdensity and its galaxies. Overall, these findings provides the first tentative evidence of accretion of cold, chemically young gas onto galaxies at high redshift, possibly feeding their star formation activity. The fact that the galaxies are members of a large structure, as opposed to field galaxies, might play a significant role in our ability to detect the accreting gas.Comment: 57 pages, 17 figures, 1 table; accepted for publication by ApJ (Aug 9, 2011); minor modifications to match the accepted versio

Exclusive vector meson production at HERA

Exclusive vector meson production from real and virtual photons is, for the most part, described well by soft pomeron exchange. However, there are some unsolved normalisation problems, and just a hint that an additional contribution from hard pomeron exchange may be needed.Comment: 12 pages, uuencoded postscript, including 5 figure

Autour du livre de Anni Borzeix & Gwenaële Rot : Genèse d'une discipline, naissance d'une revue Sociologie du travail

Le 20 mai 2011, lors d'une séance du séminaire du centre de sociologie des organisations, Anni Borzeix et Gwenaëlle Rot ont présenté leur ouvrage sur la naissance de la revue sociologie du travail. Ce livre a été écrit à voix multiples et sa construction a pris plusieurs années. Il s'agit à la fois d'histoire de la sociologie et de sociologie historique. Le projet est venu notamment d'une constatation : les sociologues du travail se définissent quelquefois, sur un mode humoristique ou non, par opposition à la sociologie des organisations. D'où vient cette sorte de tension disciplinaire ? Autre élément déclencheur du projet : lors d'un colloque sur George Friedmann, un phénomène paradoxal est intervenu : on y a très peu parlé de sociologie du travail, alors que Friedmann est connu comme un des maîtres de la discipline. La question de départ a donc été : pourquoi donc, en 1959, Michel Crozier, Jean-Daniel Reynaud, Alain Touraine, et Jean-René Tréanton ont-ils fondé la revue Sociologie du travail ?revue Sociologie du travail; naissance d'une revue; Genèse d'une discipline.