Studies of neutral hydrogen gas in distant galaxies using the spectral stacking technique

Ceraj, Lana (2015) Studies of neutral hydrogen gas in distant galaxies using the spectral stacking technique. Diploma thesis, Faculty of Science > Department of Physics.

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Abstract

Neutral hydrogen gas (HI) is the building block of galaxies as it is a primary fuel for star formation. Direct observations of the HI 21 cm emission line are restricted by the limited sensitivities of radio telescopes. To overcome this issue, we employ the relatively new technique of spectral stacking to push the redshift limits of radio observations further than otherwise possible. This thesis presents an HI spectral stacking analysis of galaxies within the Galaxy and Mass Assembly (GAMA) 9^h field and over the redshift range 0.039< z <0.134. HI data was collected with the Parkes radio telescope in New South Wales, Australia. Galaxy positions and spectroscopic redshifts are provided by the GAMA survey. By co-adding the spectra of 7049 galaxies extracted from the Parkes data cube, we obtain a strong integrated signal-to-noise ratio of S/N=11.9. The rms noise behaves in a Gaussian manner, with slight deviation caused by the residual radio frequency interference and continuum source emission in the data. We measure average HI properties by integrating stacked spectra over ±300 kms^−1 from rest frame, the range equivalent to the maximum expected width of the HI profile. The resulting average flux density, average HI mass and average HI mass-to-light ratio are, respectively: (S)=(1.07±0.09)mJy, (M_HI)=(2.97±0.38)×10^9h^−2 M_⊙ and (M_HI/L_r)=(1.58±0.39)M_⊙L_⊙^1. We test two different strategies in calculating the cosmic HI mass density (ΩHI). To account for source confusion effect, we apply the confusion factor

Item Type: Thesis (Diploma thesis)
Keywords: neutral hydrogen gas, distant galaxies
Supervisor: Smolčić, Vernesa
Date: 25 September 2015
Number of Pages: 40
Subjects: NATURAL SCIENCES > Physics > Astronomy and Astrophysics
Divisions: Faculty of Science > Department of Physics
Depositing User: Gordana Stubičan Ladešić
Date Deposited: 18 Nov 2015 16:45
Last Modified: 19 Jan 2017 14:46
URI: http://digre.pmf.unizg.hr/id/eprint/4347

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