Title Monte Carlo simulacija protojata galaksija u Cosmos pregledu neba Title (english) Monte Carlo simulations of galaxy protoclusters in Cosmos Survey Author Neven Tomičić Mentor Vernesa Smolčić (mentor)Committee member Vernesa Smolčić (predsjednik povjerenstva)Committee member Krešimir Pavlovski (član povjerenstva)Committee member Krešimir Kumerički (član povjerenstva)Committee member Matko Milin (član povjerenstva)Committee member Hrvoje Buljan (član povjerenstva)Granter University of Zagreb Defense date and country 2015-03-27, Croatia Scientific / art field, NATURAL SCIENCES Abstract Jata tj. skupovi galaksija su veliki virializirani skupovi galaksija. Galaksije doprinose oko 5% mase jata, unutar-klasterski medij oko 10% mase i tamna tvar do 85% mase. Te strukture su nastale iz protojata galaksija. Protojato je rani oblik jata sa manje galaksija i sa uočenom većom gustoćom broja galaksija u odnosu na ostale dijelove promatranog neba. Cilj ovog rada jest simuliranje protojata galaksija na različitim crvenim pomacima (z=2, 3, 4 i 5), pomoću Monte Carlo simulacije, prateći unaprijed definirane površinske profile protojata i uzimajući u obzir pogreške fotometrijskih crvenih pomaka (naspram spektroskopskih crvenih pomaka) specifičnih za COSMOS pregled neba. Simuliranjem 1,000 protojata različitih tipova (prema jatima potomcima ukupnih masa ≥ 10^15M , 3 - 10 x 10^14M⊙ i 1:37 - 3 x 10^14M⊙), kvantificirali smo karakteristike metode traženja protojata u COSMOS pregledu neba, poput kompletnosti (broj koji definira udio galaksija nakon izvedene metode traženja, naspram cijelog broja galaksija protojata), kontaminacije (broj koji definira udio galaksija na nebu koji ne pripada protojatu), gustoće broja (broj galaksija na povr šini neba) i efektivnog radijusa (radijus unutar kojeg se nalazi 68% mase protojata), te njihovo ponašanje za različite tipove protojata i crvene pomake. Također smo izveli metodu traženja protojata pomoću Voronoi dijagrama i metode određivanja ponašanja diferencijalnog viška gustoće (kojem je mjera δ_g) u ovisnosti o udaljenosti od središta protojata. Rezultati pokazuju da se kompletnost protojata ne mjenja u odnosu na crveni pomak, dok kontaminacija očekivano raste sa udaljenosti od središta protojata. Izračunati efektivni radijusi naših simuliranih protojata se slažu do na faktor 2 sa početnim efektivnim radijusima protojata, izračunatim u Chiang et al. (2013). Unatoč tom nepodudaranju, unutar naših efektivnih radijusa nalazi se 55-65% galaksija u protojatu, što je sukladno rezultatima Chiang et al. (2013). Objašnjenje za razlike među radijusima nalazimo u tome što u našim simulacijama nismo uzeli u obzir raspodjelu mase u protojatima. Pretpostavili smo da sve galaksije imaju istu masu, što može značajno utjecati na izračun efektivnog radijusa. Na kraju smo primijenili metode traženja protojata i metodu računanja efektivnog radijusa na postojeća protojata u COSMOS polju, na različitim crvenim pomacima.
Abstract (english) Galaxy clusters are large virialized collections of galaxies. Galaxies contribute about 5% to the mass of the cluster, the intracluster medium about 10% and the dark matter up to 85%. These structures are formed from galaxy protoclusters. A protocluster is an early type of cluster with fewer galaxies and an observed higher number density of galaxies, compared to other parts of the observed sky. The goal of this paper is to simulate galaxy protoclusters at different redshifts (z = 2, 3, 4 and 5), using Monte Carlo simulations, following the predefined surface profiles of the protoclusters and taking into account the errors of photometric redshifts (versus spectroscopic redshifts) specifically for the COSMOS survey. By simulating 1,000 different types of protoclusters (by the descendant clusters of the total masses ≥ 10^15M , 3 - 10 x 10^14M⊙ i 1:37 - 3 x 10^14M⊙), we quantified the characteristics of the search methods of protoclusters in the COSMOS sky survey, such as completeness (a number that defines the share of galaxies derived after search methods, compared to the total number of galaxies in the protocluster), contamination (a number that defines the share of galaxies in the sky that does not belong to the protocluster), number density (number of galaxies on the surface of the sky) and effective radius (radius within which there is 68% of the protocluster mass), and their behavior for different types of protoclusters and different redshifts. The results show that completeness of the protoclusters does not change compared to the redshift, while the contamination expectedly increases with distance from the centre of protoclusters. The calculated effective radii of our simulated protoclusters agree within a factor of 2 with the initial effective radii of protoclusters, calculated in Chiang et al. (2013). Despite this discrepancy within our effective radii, 55-65% of galaxies are in protoclusters, which is consistent with the results of Chiang et al. (2013). We believe that the differences between the radii are caused by the fact that our simulations do not take into account the distribution of the mass in the protoclusters. We assumed that all galaxies have the same mass, which can significantly affect the calculation of the effective radius. In the end we applied the search methods of protoclusters and the method of calculating the effective radius to existing protoclusters in COSMOS field, at different redshifts.
Keywords
projata galaksija
jata galaksija
Monte Carlo simulacija
COSMOS pregled neba
Keywords (english)
galaxy proclusters
galaxy clusters
Monte Carlo simulation
COSMOS sky survey
Language croatian URN:NBN urn:nbn:hr:217:152261 Study programme Title: Physics; specializations in: Research Type of resource Text File origin Born digital Access conditions Open access Terms of use Created on 2017-04-04 20:59:24
