AbstractsAstronomy & Space Science

This thesis presents the search for the \cii 158 $\mu$m emission line, one of the brightest far-infrared (FIR) emission lines, in a selection of $z>6$ (the Universe was less than 1 Gyr old) galaxies. These galaxies have been observed with CARMA and PdBI millimeter interferometers and no \cii nor continuum emission is detected. The estimated upper limits show that the \cii line in these galaxies is not as bright as in some galaxies with similar values of star formation rates at lower redshifts. These results indicate that the low metallicity expected for these type of galaxies could be the reason of the non-detection of \cii. For a lensed multiple-imaged galaxy (MACS0329-iD) observed with the ALMA millimeter interferometer a tentative detection of the \cii emission line with a $3.7\sigma$ significance has been detected. This detection would put the galaxy at a spectroscopic redshift of $z=6.17722 \pm 0.00005$, in agreement with the photometric redshift previously estimated. The galaxy is not detected in the continuum, with a $3\sigma$ upper limit of 1.8 mJy at 158 $\mu$m restframe. The ratio between the tentative observed \cii emission line and the far-infrared luminosity of $>5.0\times10^{-4}$ puts this galaxy near what is typically found in the local star-forming galaxies. In conclusion, significantly deeper \cii observations than previously thought are need in the future to securely detect \cii emission in the highest redshift galaxies. This work also presents the search for lensed submillimeter galaxies with the goal of studying the faint population of dusty starbursting galaxies. Observations were made of 15 galaxy clusters using the bolometers LABOCA at APEX telescope and GISMO at IRAM 30 meters telescope. Of the 62 unique sources detected, we were able to find the galaxy counterpart to the far-infrared emission when was possible. Our sample of lensed submillimeter galaxies appears to be within the range of observed infrared luminosities at $z<2$ and being lower than other samples at $z>2$. When comparing the stellar masses and the SFR of our sample, they appear to agree well with the main-sequence of galaxies at $z\sim2$. This thesis presents the efforts of studying high redshift galaxies with submillimeter and millimeter observations and some techniques to better analyze and understand them. Diese Doktorarbeit beschreibt sensitive Beobachtungen der \cii 158 $\mu$m Emissionslinie, eine der hellsten Emissionslinien im Ferninfraroten (FIR), in Galaxien bei Rotverschiebungen von $z>6$ (Alter des Universums: weniger als 1 Gyr). Die Galaxien wurden mit den CARMA und PdBI Millimeterinterferometern beobachtet, und es wurde weder die die \cii Linie noch Kontinuumsemission detektiert. Die erzielte Empfindlichkeit zeigt, dass diese Galaxien nicht so hell in \cii Emission sind, wie Galaxien bei geringeren Rotverschiebungen mit \"ahnlichen Sternentstehungsraten. Diese Ergebnisse lassen darauf schliessen, dass eventuell die geringe Metallizit\"at der Galaxien der Grund f\"ur die schwache \cii Emission…