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An observational study of the z~4 strongly lensed dusty star-forming galaxy MM18423+5938

F. Sweijen (2017) An observational study of the z~4 strongly lensed dusty star-forming galaxy MM18423+5938. Master's Thesis / Essay, Astronomy.

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In this thesis we present the result of a study on the strongly gravitationally lensed dusty star-forming galaxy (DSFG) MM18423+5938. We use data from the HST at 1.1 µm to discuss the lens morphology, which is more complex than it appears to be. With the VLA, we use 5 GHz observations to add a second photometric data point to the synchrotron part of the spectrum. The system is doubly imaged in the radio continuum, with S_5GHz = 74 ± 19 mJy. We find a spectral index of α = -0.83 ± 0.34; consistent with other DSFG samples. The molecular gas content was studied through CO(1-0) and CO(2-1) emission using both previously published data and archival data. We find the CO(1-0) line intensity to be I_CO(1-0) = 0.5 ± 0.3 μ⁻¹ Jy km s⁻¹, with a line luminosity of L'_CO(1-0) = 3.1 ± 1.9 × 10¹¹ μ⁻¹ K km s⁻¹ pc², resulting in a molecular gas mass of M_gas = 2.5 ± 0.5 × 10¹¹ μ⁻¹ M_sol. For the CO(2-1) emission we find a lensed line intensity I_CO(2-1) = 2.8 ± 1.5 μ⁻¹ Jy km s⁻¹, where μ is the magnification, resulting in a line luminosity of L'_CO(2-1) = 4.5 ± 0.8 × 10¹¹ μ⁻¹ K km s⁻¹ pc². We identify a possible double peak profile, which would be a hint of a rotating disk, but detailed dynamical modeling is required to test this. Splitting the line into a (relative) red, green and blue part shows different spatial structures, further hinting at a rotating structure. Finally 250 μm, 350 μm and 500 μm measurements from the Herschel Observatory were used to constrain the peak of the SED. We fitted an MBB and power law to the spectrum. From the SED, we then obtained T_d = 37.8^{+2.0}_{-1.9} K, β = 1.7 ± 0.2, L_FIR = 9.76 ± 0.30 × 10¹³ μ⁻¹L_sol, q = 2.59 ± 0.47 and SFR = 1.7 × 10^4 μ⁻¹ M_sol yr⁻¹. All of the parameters are consistent with other, unlensed DSFGs assuming a magnification μ ~ 12, where applicable.

Item Type: Thesis (Master's Thesis / Essay)
Degree programme: Astronomy
Thesis type: Master's Thesis / Essay
Language: English
Date Deposited: 15 Feb 2018 08:31
Last Modified: 15 Feb 2018 08:31

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