Constraining the Thermal Dust Content of Lyman-Break Galaxies in an Overdense Field at z~5

We have carried out 870 micron observations in the J1040.7-1155 field, known to host an overdensity of Lyman break galaxies at z=5.16 +/- 0.05. We do not detect any individual source at the S(870)=3.0 mJy/beam (2 sigma) level. A stack of nine spectroscopically confirmed z>5 galaxies also yields a non-detection, constraining the submillimeter flux from a typical galaxy at this redshift to S(870)<0.85 mJy, which corresponds to a mass limit M(dust)<1.2x10^8 M_sun (2 sigma). This constrains the mass of thermal dust in distant Lyman break galaxies to less than one tenth of their typical stellar mass. We see no evidence for strong submillimeter galaxies associated with the ultraviolet-selected galaxy overdensity, but cannot rule out the presence of fainter, less massive sources.Comment: 5 pages, 2 figures. MNRAS in pres

Compound-specific carbon isotope analysis of volatile organic compounds in water using solid-phase microextraction.

The compound-specific isotope analysis technique in conjunction with solid-phase microextraction using a Carboxen-polydimethylsiloxane fiber was tested and implemented for isotopes analysis of organic compounds aiming for environmental application in contaminated groundwater. δ13C values of several chlorinated methanes and ethenes, toluene and chlorobenzene were determined using a gas chromatograph coupled to an isotope ratio mass spectrometer through a combustion interface. Direct and headspace solid-phase microextraction (D-SPME, HS-SPME) methods were tested in order to determine the optimum conditions to obtain reproducible δ13C values at very low concentration (ug/L range) and, to elucidate the carbon isotopic effects associated with the competitive extraction. For D-SPME higher accuracy and precision of δ13C results were obtained with no salted aqueous standards. Despite that the δ13C of those compounds analyzed with both methods showed similar precision (< 0.5 ¿) and accuracy, the highest sensitivity was reached with HS-SPME. Furthermore, the δ13C values of cis-1,2-dichloroethylene, chorinated methanes and aromatic compounds obtained using HS-SPME showed measurable deviations respect to the isotopic composition of pure phase compounds, however, these deviations are constant according to the analytical uncertainties, indicating that they are not affected by competitive extraction and, they could be corrected using standard correction technique based on internal calibrated standards