Estimating the stellar masses of NLS1 galaxies using multifrequency data

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.

Grantor dc:publisher

Helsingin yliopisto

Year dc:date.issued

2025

Author dc:creator

• Syrjärinne, Inkeri

• galaxies
• radio astronomy
• star formation
• active galactic nuclei
• narrow-line Seyfert 1 galaxies

Statement dc:rights

• CC BY 4.0

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/10138/601002

OAI identifier oai:identifier

oai:helda.helsinki.fi:10138/601002