Proučavanje plina neutralnog vodika u dalekim galaksijama koristeći metodu slaganja spektara

master's thesis

• Title (english): Studies of neutral hydrogen gas in distant galaxies using the spectral stacking technique
• Author: Lana Ceraj
• Mentor: Vernesa Smolčić (mentor)
• Committee member: Vernesa Smolčić (predsjednik povjerenstva)
• Committee member: Mirko Planinić (član povjerenstva)
• Committee member: Ivica Smolić (član povjerenstva)
• Committee member: Krešimir Pavlovski (član povjerenstva)
• Committee member: Krešimir Kumerički (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Physics); Zagreb
• Defense date and country: 2015-09-25, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics; Astronomy and Astrophysics

Abstract

Plin neutralnog vodika (HI) smatra se građevnom jedinicom galaksija jer služi kao primarno gorivo za stvaranje zvijezda. Izravna opažanja HI emisijske linije na 21 cm ograničena su granicama osjetljivosti radio teleskopa. Kako bi nadišli ovaj problem, koristimo relativno novu metodu slaganja spektara kako bi pomaknuli granice crvenih pomaka u radio opažanjima dalje nego li je moguće ostalim opažačkim metodama. U ovom radu predstavljena je statistička metoda slaganja HI spektara galaksija lociranih u tzv. G09 nebeskom polju, u rasponu crvenih pomaka 0.039<z<0.134. HI opažanja smiljena su Parkes radio teleskopom (New South Wales, Australija). Položaji galaksija i crveni pomaci nalaze se u katalogu dobavljenom iz baze podataka Galaxy and Mass Assembly (GAMA) istraživanja. Slažući spektre 7049 galaksija, ekstrahirane iz Parkes podatkovne kocke, postižemo dobar omjer signala i šuma, S/N=11.9. Šum pokazuje karakteristike Gaussiana, uz malo odstupanje zbog prisutnosti rezidualne radio-frekventne interferencije i emisije od snažnih izvora u podacima. Usrednjene veličine karakteristične HI dobivamo integrirajući složene spektre u granicama ±300 kms^−1 od sustava mirovanja. Taj raspon odgovara iznosu najveće očekivane širine HI profila. Srednja vrijednost gustoće toka, usrednjena masa HI i usrednjeni omjer mase i luminoziteta HI su (tim redoslijedom): (S)=(1.07±0.09)mJy, (M_HI)=(2.97±0.38)×10^9ℎ^−2M_⊙ i M_HI/L_r)=(1.58±0.39) M_⊙L_⊙^−1. Pri izračunu kozmičke gustoće mase HI (Ω_HI) testiramo dvije formule. Kako bi u izračun uključili i efekt konfuzije, koristimo faktor konfuzije.

Abstract (english)

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

• Keywords: plin neutralnog vodika; daleke galaksije
• Keywords (english): neutral hydrogen gas; distant galaxies
• Language: croatian
• URN:NBN: urn:nbn:hr:217:694269
• Study programme: Title: Physics; specializations in: Research; Course: Research; Study programme type: university; Study level: integrated undergraduate and graduate; Academic / professional title: magistar/magistra fizike (magistar/magistra fizike)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2017-04-04 20:03:35