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V magistrskem delu je raziskana kemijska homogenost Orionovega kompleksa molekularnih oblakov na podlagi meritev zastopanosti kisika v posameznih zvezdah. Najprej so predstavljene osnove zvezdne spektroskopije. Opisana sta spekter črnega telesa in formacija absorpcijskih črt. Podrobneje je opisan teoretični Voightov profil absorpcijskih črt z upoštevanjem tlačne in termične razširitve, opisani pa so tudi premiki in razširitve črt, ki izvirajo iz zvezdne dinamike. Predstavljena je tehnika Echelle spektroskopije, HR in Kielov diagram ter spektralna klasifikacija zvezd na podlagi podobnosti v njihovih spektrih. Sledi opis procesov življenja zvezd -- od njihove formacije iz molekularnih oblakov in obdobja na glavni veji, do razvoja v orjakinje ter smrti zvezd in obogatitve okoliškega prostora z elementi nukleosinteze. Predstavljene so tudi glavne fizične in kemijske značilnosti Orionovega kompleksa. V praktičnem delu naloge so uporabljena spektroskopska opazovanja 30 zvezd iz območij molekularnih oblakov v Orionu in Samorogu v območju valovnih dolžin od 395 do 680,nm. V glavnem so to vroče zvezde glavne veje, nekaj pa je tudi orjakinj. Opisan je postopek obdelave surovih spektrov v programu IRAF, za katere sem nato z uporabo programa iSpec določil vrednosti radialne hitrosti, atmosferskih parametrov (efektivna temperatura, gravitacijski pospešek na površju, mikro- in makroturbulenčna hitrost, projekcija rotacijske hitrosti in koeficient robne zatemnitve) in zastopanosti kisika. Zastopanosti kisika sem določil pod predpostavko kemijske homogenosti kompleksa v kovinskosti in zastopanosti $alpha$ elementov -- pričakoval sem torej enakomerno zastopanost kisika v različnih spektralnih tipih zvezd. Območji sta glede na zastopanosti kisika v zvezdah homogeni. Določena absolutna zastopanost kisika v opazovanih zvezdah znaša $A$(O)$=(8,33 pm 0,49),$dex, določena relativna zastopanost glede na železo pa [O/Fe]$=(-0,26pm0,49),$dex. Povprečna velikost napake določene zastopanosti kisika vseh zvezd je enaka $0,54,$dex. Raziskani so tudi vplivi posameznih parametrov na končne določene zastopanosti kisika. Med vsemi parametri na končno napako najbolj vplivata natančnost določitve efektivne temperature in gravitacijskega pospeška na površju. The Master’s thesis explores the chemical homogeneity of the stars of the Orion Molecular Complex, based on measurements of Oxygen abundance in individual stars. Stellar spectroscopy is introduced, followed by the description of a blackbody spectrum and the formation of absorption lines. Theoretical Voigt profile of absorption lines is described in detail by taking pressure and thermal broadening into account. Doppler shift and rotational broadening of lines that originate from the star dynamics are described as well. Furthermore, the Echelle Spectroscopy technique, HR and Kiel diagram, and the spectral classification of stars, based on similarities in their spectra, are presented. The process of the stellar life is described from the formation in molecular clouds and the main sequence phase, to the evolution into giants and finally deaths that enrich the surrounding environment with the elements of stellar nucleosynthesis. Theoretical part is concluded with the presentation of physical and chemical features of the Orion Complex. In practical part, spectroscopical observations of 30 stars from the molecular cloud areas in Orion and Monoceros, covering the area of wavelengths from 395 to 680 nm, have been used. Mainly, these are hot main sequence stars, including a few giants. It is described how raw spectra have been processed in IRAF programme and how iSpec programme has been used to determine the radial velocities, atmospheric parameters (effective temperature, gravitational acceleration on the surface, micro- and macro-turbulence velocities, the projection of the rotational velocity and the limb darkening coefficient) and most importantly, the Oxygen abundances of observed stars. Oxygen abundance have been determined under the assumption that Orion complex is chemically homogeneous in metallicities and abundances of $alpha$ elements – therefore, the Oxygen abundance should not vary between different spectral types. Considering Oxygen abundance, the Orion Complex is proven homogenous. The determined absolute Oxygen abundance in the observed stars is $A$(O)$=(8,33pm0,49),$dex, while the determined abundance, relative to iron is [O/Fe]$=(-0,26pm0,49),$dex. The average spread of determined Oxygen abundances of all stars is equal to 0,54,dex. Lastly, the relations between the determined Oxygen abundances and uncertainties of individual parameters have been researched. Among all the parameters, what affects the Oxygen abundances the most, is the accuracy of determining the effective temperature and the gravitational acceleration on the surface.

We exploit the unprecedented depth of integral field data from the KMOS Ultra-deep Rotational Velocity Survey (KURVS) to analyse the strong (H alpha) and forbidden ([MI], [SII]) emission line ratios in 22 main-sequence galaxies at z approximate to 1.5. Using the (NII]/H alpha emission-line ratio, we confirm the presence of the stellar mass-gas-phase metallicity relation at this epoch, with galaxies exhibiting on average 0.13 +/- 0.04 dex lower gas-phase metallicity (12 + log(O/H)(M13) = 8.40 +/- 0.03) for a given stellar mass (log(10)(M-*[M-circle dot] = 10.1 +/- 0.1) .than local main-sequence galaxies. We determine the galaxy-integrated [SII] doublet ratio, with a median value of [SII]lambda 6716/lambda 6731 = 1.26 +/- 0.14 equivalent to an electron density of log(10)(n(e)[cm(-3)]) = 1.95 +/- 0.12. Utilising CANDELS HST multi-band imaging we define the pixel surface-mass and star-formation rate density in each galaxy and spatially resolve the fundamental metallicity relation at z approximate to 1.5, finding an evolution of 0.05 +/- 0.01 dex compared to the local relation. We quantify the intrinsic gas-phase metallicity gradient within the galaxies using the [NII]/H alpha calibration, finding a median annuli-based gradient of Delta Z/Delta R = -0.015 +/- 0.005 dex kpc(-1). Finally, we examine the azimuthal variations in gas-phase metallicity, which show a negative correlation with the galaxy integrated star-formation rate surface density (r(s) = -0.40, p(s) = 0.07) but no connection to the galaxies kinematic or morphological properties nor radial variations in stellar mass surface density or star formation rate surface density. This suggests both the radial and azimuthal variations in interstellar medium properties are connected to the galaxy integrated density of recent star formation.

The determination of the solar oxygen abundance is a topic that has long beenunder debate, where the exact value has varied between researchers. These variationsin the oxygen abundance have implications on our understanding of the Sun and itsinterior as well as our understanding of other stars. The aim of this report is to explorethe di erences between three observations; the Liège, Hamburg and SST, and their effecton the solar oxygen abundance calculated from the 777 nm triplet. In the reportit was found that the abundance from the Liège and SST data was lower and in betteragreement (A(O) ≈ 8.709 dex) compared to the Hamburg data (A(O) ≈ 8.732 dex).One of the potential reasons for these di erences explored in the thesis were the e ectsof magnetic elds. After comparing the di erences it was argued that the SST dataset as well as the Liège could be considered more reliable compared to the Hamburg.The argued abundance was therefore of a somewhat lower value which does not helplessen the inconsistency between solar models and helioseismology. Bestämningen av mängden syre i solen har länge varit ett debatterat område där det exakta numeriska värdet varierat bland forskare. Dessa variationer av mängden syre ger konsekvenser för vår förståelse av solen och dess inre samt för vår förståelse av andra stjärnor. Syftet med denna rapport är att utforska skillnaderna mellan tre observationer; från Liège, Hamburg och SST, samt deras påverkan på mängden syre i solen beräknad från 777 nm tripletten. Rapporten fann att mängden syre beräknad från Liège- och SST-datan både var lägre samt stämde bättre överens (A(O) ≈ 8.709 dex) i jämförelse med mängden från Hamburg observationen (A(O) ≈ 8.732 dex). En potentiell anledning till skillnaden i resultat som utforskades i denna uppsats var påverkan av magnetiska fält. Efter jämförelse av skillnaderna kunde det konstateras att datan från SST så väl som från Liège kan anses mer pålitliga i förhållande till Hamburg-datan. Den förespråkade mängden syre var åt det lägre hållet vilket inte bidrar till minskningen av avvikelserna mellan modeller av solen och mätningar via helioseismologi.

Understanding the spatial distribution of metals within galaxies allows us to study the processes of chemical enrichment and mixing in the interstellar medium. In this work, we map the 2D distribution of metals using a Gaussian Process Regression (GPR) for 19 star-forming galaxies observed with the Very Large Telescope/Multi Unit Spectroscopic Explorer (VLT–MUSE) as a part of the PHANGS–MUSE survey. We find that 12 of our 19 galaxies show significant 2D metallicity variation. Those without significant variations typically have fewer metallicity measurements, indicating this is due to the dearth of ${\rm H\, {\small II}}$ regions in these galaxies, rather than a lack of higher-order variation. After subtracting a linear radial gradient, we see no enrichment in the spiral arms versus the disc. We measure the 50 per cent correlation scale from the two-point correlation function of these radially subtracted maps, finding it to typically be an order of magnitude smaller than the fitted GPR kernel scale length. We study the dependence of the two-point correlation scale length with a number of global galaxy properties. We find no relationship between the 50 per cent correlation scale and the overall gas turbulence, in tension with existing theoretical models. We also find more actively star-forming galaxies, and earlier type galaxies have a larger 50 per cent correlation scale. The size and stellar mass surface density do not appear to correlate with the 50 per cent correlation scale, indicating that perhaps the evolutionary state of the galaxy and its current star formation activity is the strongest indicator of the homogeneity of the metal distribution.