Mase supermasivnih crnih rupa u kvazarima

master's thesis

• Title (english): Masses of supermassive black holes in quasars
• Author: Luka Matijević
• Mentor: Vernesa Smolčić (mentor)
• Committee member: Vernesa Smolčić (predsjednik povjerenstva)
• Committee member: Matko Milin (član povjerenstva)
• Committee member: Vibor Jelić (član povjerenstva)
• Committee member: Ivica Smolić (član povjerenstva)
• Committee member: Ivica Friščić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Physics); Zagreb
• Defense date and country: 2023-09-05, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics

Abstract

Vjeruje se da se supermasivne crne rupe nalaze u središtima većine galaksija te da su njihove mase povezane sa svojstvima galaksije u kojoj se nalaze. Određivanje mase supermasivnih crnih rupa je stoga važno za razumijevanje koevolucije galaksija i njihovih središnjih supermasivnih crnih rupa. Jedna od najpouzdanijih metoda procjene mase supermasivnih crnih rupa je metoda kartiranja jeke. Ta metoda je vremenski zahtjevna i njen uspjeh ovisi o mnoštvu faktora. Rezultati te metode po kazuju da postoji empirijska korelacija između 1) veličine područja širokih linija, a to je područje ioniziranog plina koji okružuje supermasivnu crnu rupu i 2) monokromatskog luminoziteta kontinuuma. U ovom radu te korelacije će se koristiti kako bi se izračunale virijalne mase supermasivnih crnih rupa koristeći dva različita pristupa. U prvom pristupu analizirali su se spektri kvazara iz Data Release 3 baze pregleda neba Sloan Digital Sky Survey (SDSS). Ti kvazari nalaze se na crvenim pomacima 0.7 < z < 2 te je stoga u analizi korištena emisijska linija Mg II, kao i monokromatski luminozitet na 3000 A. Monokromatski luminoziteti su izračunati koristeći monokromatske tokove zračenja interpolacijom njihovih vrijednosti kroz 3 najbliže vrijednosti oko zadane valne duljine što se pokazalo pouzdanijim od vrijednosti dobivenih koristeći prilagodbu zakona potencije. Prije računa svih parametara, na spektar se primijenio Savitzky-Golay filter kako bi se uklonio šum. Rezultati dobiveni ovim pristupom pokazali su konzistentnost s masama supermasivnih crnih rupa prethodno određenim sličnim metodama iz literature. Drugi pristup koristi najnoviju SDSS-ovu bazu spektara kvazara Data Release 16 Quasar Catalog koja pokriva crvene pomake 0.1 ≲ z ≲ 6. Veći interval crvenih po maka znači da emisijska linija Mg II nije prisutna u svim spektrima. Zbog toga se uz nju koriste i emisijske linije Hβ te C IV. Za račun spektralnih karakteristika koristi se PyQSOFit algoritam. PyQSOFit je moćan alat za prilagodbu kontinuiranog zračenja i emisijskih linija na spektre kvazara te se može koristiti za računanje širine linija, monokromatskih luminoziteta, itd. Od izabranog uzorka ∼ 85 % masa se slaže do na ∼ 0.1 dex s masama prethodno određenima sličnim metodama. Rezultati su potom uspoređeni s masama dobivenima u prvom pristupu te se pokazalo da je medijan distribucije omjera masa pomaknut od jedinice za ≈ 40 %. Unatoč tomu, mase do bivene PyQSOFit algoritmom se smatraju pouzdanima jer ovaj pristup uzima u obzir više parametara od prethodnog. Naposljetku, PyQSOFit algoritam za račun masa supermasivnih crnih rupa je primijenjen na spektre kvazara iz pregleda neba Cosmic Evolution Survey (COSMOS). Iako su COSMOS spektri snimani s različitom tehnikom spektroskopije te se vrijednosti toka zračenja u nekim slučajevima razlikuju u usporedbi sa SDSS spektrima zbog varijabilnosti, pokazalo se da se ∼ 80 % masa dobivenih iz COSMOS spektara nalazi oko ∼ 0.4 dex od usporednog uzorka dobivenog iz SDSS spektara.

Abstract (english)

Supermassive black holes (SMBHs) are believed to reside at the center of most galaxies, and their masses are correlated with the properties of their host galaxy. The determination of SMBH masses is therefore a crucial ingredient for understanding the co-evolution of galaxies and their central black holes. One of the most accurate methods for estimating the mass of SMBHs is reverberation mapping (RM). Reverbe ration mapping campaigns are time consuming, and their success depends on vari ous factors. The RM results show an empirical correlation between 1) the size of the broad line region (BLR), which is a region of ionized gas that surrounds the SMBH, and 2) a monochromatic continuum luminosity. In this thesis, those correlations are used to estimate virial SMBH masses using two different approaches. In the first approach a sample of quasar spectra from Sloan Digital Sky Survey’s (SDSS) Data Release 3 was analyzed. Those quasars are located at redshifts 0.7 < z < 2 and therefore the emission line used in the analysis is Mg II with monochromatic luminosities at 3000 A. Monochromatic luminosities were calculated from monochro- ˚ matic fluxes by interpolating their values over the three nearest values on specified wavelength which showed greater reliability than using values from fitted power-law. Before all calculations of parameters, the Savitzky-Golay filter was fitted on spectra to decrease the noise. Results from this approach showed consistence with SMBH mass estimates from similar approaches in the literature. The second approach used the newest SDSS quasar spectra from the Data Rele ase 16 Quasar Catalog which covers redshifts 0.1 ≲ z ≲ 6. Greater redshift range means that Mg II line is not present in all spectra. Hence Hβ and C IV emission lines are used in addition to the Mg II line. For calculating spectral characteristics, the PyQSOFit algorithm is used. PyQSOFit is a powerful tool which fits continuum emi ssion and emission lines on a given spectra and can be used to calculate line FWHM, monochromatic luminosities, etc. From the selected sample ∼ 85 % of the masses are scattered ∼ 0.1 dex from the comparison sample taken from the literature. The results were then compared to the first approach, and it was shown that the median of the distribution of the ratio of SMBH masses is shifted by ≈ 40 % from unity. However, PyQSOFit masses were chosen as fiducial because they are calculated by taking more parameters into account. Lastly, PyQSOFit algorithm was used to calculate SMBH masses from quasars in Cosmic Evolution Survey (COSMOS). Although COSMOS spectra used different kind of spectroscopy than SDSS spectra and flux values differed because of variability, it was shown that ∼ 80 % masses are scattered around ∼ 0.4 dex from the comparison sample from SDSS.

• Keywords: supermasivne crne rupe; područja širokih linija; monokromatski luminozitet; disperzija linija; puna širina na polovici maksimuma; Sloan Digital Sky Survey; aktivne galaktičke jezgre; PyQSOFit; COSMOS
• Keywords (english): Supermassive black holes; Broad line region; Monochromatic luminosity; Line dispersion; Full width at half maximum; Sloan Digital Sky Survey; Active Galactic Nuclei; PyQSOFit; COSMOS
• Language: croatian
• URN:NBN: urn:nbn:hr:217:109337
• 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: 2023-11-23 11:18:48