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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Lyα and C iii] emission in z = 7–9 Galaxies: accelerated reionization around luminous star-forming systems?

Stark, Daniel P., Ellis, Richard S., Charlot, Stéphane, Chevallard, Jacopo, Tang, Mengtao, Belli, Sirio, Zitrin, Adi, Mainali, Ramesh, Gutkin, Julia, Vidal-García, Alba, Bouwens, Rychard, Oesch, Pascal 01 January 2017 (has links)
We discuss new Keck/MOSFIRE spectroscopic observations of four luminous galaxies at z similar or equal to 7-9 selected to have intense optical line emission by Roberts-Borsani et al. Previous follow-up has revealed Ly alpha in two of the four galaxies. Our new MOSFIRE observations confirm that Lya is present in the entire sample. We detect Lya emission in the galaxy COS-zs7-1, confirming its redshift as z.(Ly alpha) = 7.154, and we detect Lya in EGS-zs8-2 at z(Ly alpha) = 7.477, verifying an earlier tentative detection. The ubiquity of Lya in this sample is puzzling given that the IGM is expected to be significantly neutral over 7 < z < 9. To investigate this result in more detail, we have initiated a campaign to target UV metal lines in the four Lya emitters as a probe of both the ionizing field and the Lya velocity offset at early times. Here we present the detection of C III] emission in the z = 7.73 galaxy EGS-zs8-1, requiring an intense radiation field and moderately low metallicity. We argue that the radiation field is likely to affect the local environment, increasing the transmission of Lya through the galaxy. Moreover, the centroid of C III] indicates that Lya is redshifted by 340 km s (1). This velocity offset is larger than that seen in less luminous systems, providing an explanation for the transmission of Lya emission through the IGM. Since the transmission is further enhanced by the likelihood that such systems are also situated in large ionized bubbles, the visibility of Lya at z > 7 is expected to be strongly luminosity-dependent, with transmission accelerated in systems with intense star formation.
2

ALMA SPECTROSCOPIC SURVEY IN THE HUBBLE ULTRA DEEP FIELD: SURVEY DESCRIPTION

Walter, Fabian, Decarli, Roberto, Aravena, Manuel, Carilli, Chris, Bouwens, Rychard, Cunha, Elisabete da, Daddi, Emanuele, Ivison, R. J., Riechers, Dominik, Smail, Ian, Swinbank, Mark, Weiss, Axel, Anguita, Timo, Assef, Roberto, Bacon, Roland, Bauer, Franz, Bell, Eric F., Bertoldi, Frank, Chapman, Scott, Colina, Luis, Cortes, Paulo C., Cox, Pierre, Dickinson, Mark, Elbaz, David, Gónzalez-López, Jorge, Ibar, Edo, Inami, Hanae, Infante, Leopoldo, Hodge, Jacqueline, Karim, Alex, Fevre, Olivier Le, Magnelli, Benjamin, Neri, Roberto, Oesch, Pascal, Ota, Kazuaki, Popping, Gergö, Rix, Hans-Walter, Sargent, Mark, Sheth, Kartik, Wel, Arjen van der, Werf, Paul van der, Wagg, Jeff 08 December 2016 (has links)
We present the rationale for and the observational description of ASPECS: the ALMA SPECtroscopic Survey in the Hubble Ultra-Deep Field (UDF), the cosmological deep field that has the deepest multi-wavelength data available. Our overarching goal is to obtain an unbiased census of molecular gas and dust continuum emission in high-redshift (z > 0.5) galaxies. The similar to 1' region covered within the UDF was chosen to overlap with the deepest available imaging from the Hubble Space Telescope. Our ALMA observations consist of full frequency scans in band. 3 (84-115 GHz) and band. 6 (212-272 GHz) at approximately uniform line sensitivity (L'(CO) similar to 2 x 10(9) K km s(-1) pc(2)), and continuum noise levels of 3.8 mu Jy beam(-1) and 12.7 ae Jy beam(-1), respectively. The molecular surveys cover the different rotational transitions of the CO molecule, leading to essentially full redshift coverage. The [C II] emission line is also covered at redshifts 6.0 < z < 8.0. We present a customized algorithm to identify line candidates in the molecular line scans. and quantify our ability to recover artificial sources from our data. Based on whether multiple CO lines are detected, and whether optical spectroscopic redshifts as well as optical counterparts exist, we constrain the most likely line identification. We report 10 (11) CO line candidates in the 3mm (1mm) band, and our statistical analysis shows that < 4 of these (in each band) are likely spurious. Less than one-third. of the total CO flux in the low-J CO line candidates are from sources that are not associated with an optical/NIR counterpart. We also present continuum maps of both the band. 3 and band. 6 observations. The data presented here form the basis of a number of dedicated studies that are presented in subsequent papers.

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