2026-09-23T15:18:26Zhttps://helda.helsinki.fi/server/oai/requestoai:helda.helsinki.fi:10138/6010022026-07-23T15:15:59Zcom_10138_18086com_10138_17738col_10138_18093
Syrjärinne, Inkeri
Helsingin yliopisto, Matemaattis-luonnontieteellinen tiedekunta
University of Helsinki, Faculty of Science
Helsingfors universitet, Matematisk-naturvetenskapliga fakulteten
2025-09-11T08:29:38Z
2025-09-11T08:29:38Z
2025-09-11
2025-06-24
http://hdl.handle.net/10138/601002
URN:NBN:fi:hulib-202509113869
This thesis presents stellar mass estimates for a sample of 141 narrow-line Seyfert 1 (NLS1) galaxies.
NLS1s are active galactic nuclei (AGN) known for their relatively low black hole masses, disk-like
host galaxies, high accretion rates and their ability to host powerful relativistic jets. The stellar
masses are derived using the Code Investigating GALaxy Emission (CIGALE) which models galaxy
spectral energy distributions through a Bayesian comparison of theoretical and observed data. The
NLS1 sample used in this work is notably clean, with each source carefully verified to be an NLS1
through multiple selection criteria and visual inspection. The observations used in the CIGALE
analysis range from radio to X-ray.
The average stellar mass of the final sample was 3.0×10*10 M_⊙, which is typical for spiral galaxies. In
addition to stellar masses, this work estimated star formation rates (SFR), AGN luminosities, radio
luminosities and Eddington ratios for the sample. The average SFR was approximately 25 M_⊙/yr
and strong correlations were found between SFR and radio luminosity (Spearman correlation of
0.91–0.92), supporting the interpretation that radio emission in these galaxies primarily originates
from star formation. The average Eddington ratio was high (0.82), even extending into super Eddington values for radio sources (1.42) which indicates very fast black hole accretion.
Despite some correlations between AGN activity and star formation, no significant relationship
was found between AGN luminosity and SFR. The black hole mass also appeared to have little
influence on the stellar mass. These results align with previous studies. Uncertainties mostly
originate from variability in NLS1s and computational constraints. Future work should focus on
using more efficient computers, allowing for more individualised parameters to improve the accuracy
of the results.
eng
Helsingin yliopisto
University of Helsinki
Helsingfors universitet
CC BY 4.0
galaxies
radio astronomy
star formation
active galactic nuclei
narrow-line Seyfert 1 galaxies
Alkeishiukkasfysiikan ja astrofysikaalisten tieteiden maisteriohjelma
Master's Programme in Particle Physics and Astrophysical Sciences
Magisterprogrammet i elementarpartikelfysik och astrofysikaliska vetenskaper
Estimating the stellar masses of NLS1 galaxies using multifrequency data
pro gradu -tutkielma
master's thesis
pro gradu -avhandling
open.access