Exploring star formation in dwarf galaxies at Z1

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dc.contributor.advisorGilbank, Daviden_ZA
dc.contributor.advisorBlyth, SLen_ZA
dc.contributor.authorRamraj, Rionaen_ZA
dc.date.accessioned2014-11-05T03:55:14Z
dc.date.available2014-11-05T03:55:14Z
dc.date.issued2014en_ZA
dc.descriptionIncludes bibliographical references.en_ZA
dc.description.abstractThis dissertation presents the first H α measurements of star formation rates (SFRs) for dwarf galaxies at z~1 (when the Universe was approximately half its current age) using the Hubble Space Telescope (HST).We target a sample derived from the Redshift One LDSS3 Emission Line Survey (ROLES), which used [OII]3727 as a tracer of star formation to target very low stellar masses (M~10 8:5M) at this epoch. In this dissertation, we study these low mass ROLES galaxies using near-infrared slitless spectroscopy from HST. We target and measure the luminosity of the H α emission line. Even though H_ is a more direct SFR indicator, H α derived SFRs still need to be corrected for dust which is normally done using Balmer decrement measurements that are not available for our spectra. We find that using SED-fitted dust estimates, in the V-band, underestimates the extinction in high mass galaxies, in agreement with a recent result obtained by Price et al. (2013). We instead derive an empirical mass-dependent dust correction to take into account the extra extinction needed in high mass galaxies. We compare our dust corrected H α SFRs to the [OII] SFRs from ROLES. The [OII] SFRs were calculated using a mass-dependent empirical correction derived for galaxies in the Local Universe (Gilbank et al. 2010a). We find that the empirically corrected [OII] SFRs agree quite well with our dust corrected H α SFRs, having a slope of 1.6±0.7. This confirms that the mass-dependent empirical correction to [OII] works at z~1. We study the H α SSFR-mass relation for galaxies. We confirm previous results that at similar redshifts, low mass galaxies form their stars later and on longer timescales than high mass galaxies. However, our study probes down to lower limiting SFRs and lower stellar masses than any other previous studies, placing tighter constraints on galaxy evolution at this epoch.en_ZA
dc.identifier.apacitationRamraj, R. (2014). <i>Exploring star formation in dwarf galaxies at Z1</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Astronomy. Retrieved from http://hdl.handle.net/11427/9183en_ZA
dc.identifier.chicagocitationRamraj, Riona. <i>"Exploring star formation in dwarf galaxies at Z1."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Astronomy, 2014. http://hdl.handle.net/11427/9183en_ZA
dc.identifier.citationRamraj, R. 2014. Exploring star formation in dwarf galaxies at Z1. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Ramraj, Riona AB - This dissertation presents the first H α measurements of star formation rates (SFRs) for dwarf galaxies at z~1 (when the Universe was approximately half its current age) using the Hubble Space Telescope (HST).We target a sample derived from the Redshift One LDSS3 Emission Line Survey (ROLES), which used [OII]3727 as a tracer of star formation to target very low stellar masses (M~10 8:5M) at this epoch. In this dissertation, we study these low mass ROLES galaxies using near-infrared slitless spectroscopy from HST. We target and measure the luminosity of the H α emission line. Even though H_ is a more direct SFR indicator, H α derived SFRs still need to be corrected for dust which is normally done using Balmer decrement measurements that are not available for our spectra. We find that using SED-fitted dust estimates, in the V-band, underestimates the extinction in high mass galaxies, in agreement with a recent result obtained by Price et al. (2013). We instead derive an empirical mass-dependent dust correction to take into account the extra extinction needed in high mass galaxies. We compare our dust corrected H α SFRs to the [OII] SFRs from ROLES. The [OII] SFRs were calculated using a mass-dependent empirical correction derived for galaxies in the Local Universe (Gilbank et al. 2010a). We find that the empirically corrected [OII] SFRs agree quite well with our dust corrected H α SFRs, having a slope of 1.6±0.7. This confirms that the mass-dependent empirical correction to [OII] works at z~1. We study the H α SSFR-mass relation for galaxies. We confirm previous results that at similar redshifts, low mass galaxies form their stars later and on longer timescales than high mass galaxies. However, our study probes down to lower limiting SFRs and lower stellar masses than any other previous studies, placing tighter constraints on galaxy evolution at this epoch. DA - 2014 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2014 T1 - Exploring star formation in dwarf galaxies at Z1 TI - Exploring star formation in dwarf galaxies at Z1 UR - http://hdl.handle.net/11427/9183 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/9183
dc.identifier.vancouvercitationRamraj R. Exploring star formation in dwarf galaxies at Z1. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Astronomy, 2014 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/9183en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDepartment of Astronomyen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.titleExploring star formation in dwarf galaxies at Z1en_ZA
dc.typeMaster Thesis
dc.type.qualificationlevelMasters
dc.type.qualificationnameMScen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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