Revisiting the Fraction of Radio-Loud Narrow Line Seyfert 1 Galaxies with LoTSS DR1

Radio-Loud narrow-line Seyfert 1 galaxies (NLS1s), especially the extremely radio-loud ones, are widely accepted as the jetted versions of NLS1s. We explore the radio-loud fraction for NLS1s with recently released LoTSS DR1 at 150 MHz. The radio detection rate is about 28% for LoTSS DR1. The radio detected NLS1s have lower redshift than the non-detected ones. Moreover, the 150 MHz radio luminosities of NLS1s detected by LoTSS are about two orders of magnitude weaker than those of the previous samples. By defining the radio loudness with the ratio between 150 MHz radio flux and SDSS r band flux, the radio-loud fraction is about 1% with the critical radio loudness equalling 100. Radio loudness shows no dependence on central black hole mass, while weak correlations are found between radio loudness and disk luminosity, as well as Eddington ratio.