Star formation rates and stellar contributions in elliptical galaxies at 12- and 22- μm / Nur Hidayah Mohd Ali
The star formation rates (SFRs) is one of the most important characteristics in determining galaxy evolution. Investigations on star formation were done using the mid-infrared indicators. In this study, the SFRs were investigated from a sample of selected galaxies from the Sloan Digital Sky Survey (...
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| Format: | Thesis |
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2018
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| Online Access: | http://studentsrepo.um.edu.my/14984/1/Nur_Hidayah.pdf http://studentsrepo.um.edu.my/14984/2/Nur_Hidayah.pdf http://studentsrepo.um.edu.my/14984/ |
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| Summary: | The star formation rates (SFRs) is one of the most important characteristics in determining galaxy evolution. Investigations on star formation were done using the mid-infrared indicators. In this study, the SFRs were investigated from a sample of selected galaxies from the Sloan Digital Sky Survey (SDSS) MPA-JHU catalogue with morphologically-classified elliptical galaxies by Galaxy Zoo. The sample galaxies were astrometric-matched for the mid-infrared emission data from the Wide-field Infrared Survey Explorer (WISE), which was equipped with the four mid-infrared bandpass filters centered at 3.4, 4.6, 12, and 22 μm. The highly sensitive W3 (12 μm) and W4 (22 μm) bands that cover the emission for hot dust and polycyclic hydrocarbon were used to estimate the SFRs of the sources. Due to the stellar emission, this could overestimate the W3- and W4-based derived SFRs in the low star forming galaxy. The fractions of stellar contributions at W3 and W4 bands respective to W1 band were found to be about 0.125 ± 0.001 and 0.0107 ± 0.0003, respectively. Better SFRs were proposed by subtracting the stellar contributions of the sources. The study of intrinsic properties of galaxies that are highly affected by stellar contributions suggests that the star forming elliptical galaxies (SFEGs) show different star formation properties with stellar populations of different ages and masses at their central regions. By implementing the model of star formation history (SFH), the SFEGs have also showed continuous star formation activities that are comparable to spiral galaxies at the central regions. The results highlighted the possibility of unknown mechanism exists in triggering the star formation activities in the elliptical galaxies.
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