{"id":15,"date":"2019-09-10T18:40:19","date_gmt":"2019-09-10T17:40:19","guid":{"rendered":"http:\/\/www.josephcaruana.co.uk\/science\/?page_id=15"},"modified":"2025-09-20T14:21:17","modified_gmt":"2025-09-20T13:21:17","slug":"research","status":"publish","type":"page","link":"https:\/\/www.josephcaruana.co.uk\/science\/research\/","title":{"rendered":"Research"},"content":{"rendered":"\t\t
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Research Areas<\/h1>\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
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Galaxy Formation & Evolution and Reionization<\/h2>\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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One of my main research interests lies in galaxy formation and evolution, in particular the observational study of galaxies in the early universe (z > 7). A lot of my work has involved designing, undertaking and analysing follow-up spectroscopic surveys of high-redshift candidate galaxies. <\/span><\/p>\n

At such high redshifts, a particularly useful emission line is Lyman alpha.  This emission line can be used to gain a lot of information about these objects, including confirmation of their redshift.<\/span><\/p>\n

For objects lying at such large distances, the Lyman-alpha line is redshifted to the infrared region of the electromagnetic spectrum. In analysing this data, where any potential signal is very faint and the infrared background sky varies a lot over short time-scales, a lot of effort goes into developing optimal data reduction techniques.<\/span>
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These galaxies are viewed at a time before the “fog” of neutral hydrogen has been cleared, so these galaxies are used as probes of the ionization state of the universe during its infancy. Of particular interest is the question of whether these first objects provided sufficient photons to reionize the universe.<\/span><\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t

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A colour composite of SMACS 0723. Image: Joseph Caruana using public JWST data reduced by Ferreira et al. (2022).<\/figcaption>\n\t\t\t\t\t\t\t\t\t\t<\/figure>\n\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
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Some of our inferences about the universe at high redshift base upon extrapolations from lower redshifts, such as the fraction of Lyman alpha emitters in the z=3-5 universe; to this end I have also carried out work studying galaxies in this redshift range.<\/p>

The observatories I use for this work are both space-based, e.g. the NASA\/ESA James Webb Space Telescope<\/a> and\u00a0Hubble Space Telescope<\/a>, and ground-based. \u00a0For my spectroscopic studies, I have been using various spectrographs installed on ground-based observatories to carry out long-slit, cross-dispersed, multiple-slit, and multi-object IFU spectroscopy. These instruments include:\u00a0<\/p>