Investigating X-ray emission from radio-detected broad- and narrow-line Seyfert 1 galaxies

Abstract

This paper presents a study of the X-ray emission for a sample of radio-detected (RD-) broad- and narrow-line Seyfert 1 galaxies (BLS1s and NLS1s). Our aim is to investigate the X-ray emission properties of early-stage accretion activity or early jets in RD-NLS1s. By fitting XMM-Newton X-ray spectra and combining them with multi-band data from SDSS and FIRST, we conducted a statistical comparative study on the X-ray emission and multi-band correlations of RD-NLS1s and RD-BLS1s. RD-NLS1s and RD-BLS1s show no significant difference in their soft X-ray blackbody temperatures, but RD-NLS1s exhibit steeper hard X-ray photon indices and optical-to-X-ray slopes (( ̊m ox )). Moreover, correlation analyses of various parameters reveal intrinsic differences in the X-ray emission between the two samples. For instance, at comparable optical luminosities, RD-NLS1s exhibit a higher ( α_ ̊m ox ) (i.e. weaker X-ray emission), marginally distinct dependencies between the radio luminosity and black hole mass in the fundamental plane, and different correlations between ( α_ ̊m ox ) and radio loudness. Based on the relationship between the UV luminosity and ( α_ ̊m ox ) in radio-quiet (RQ-) active galactic nuclei (AGNs), the estimated X-ray excess (( Δ α_ ̊m ox )) in both samples is positively correlated with the radio loudness. RQ-BLS1s generally display an X-ray excess (( Δ α_ ̊m ox < 0 )), whereas RQ-NLS1s tend to show an X-ray deficiency (( Δ α_ ̊m ox > 0 )). The Eddington ratio of RQ-NLS1s derived from X-ray luminosity is lower than that inferred from optical luminosity, further supporting their intrinsically weaker X-ray emission. These differences in X-ray emission between RD-NLS1s and RD-BLS1s may ultimately stem from the earlier evolutionary stage of NLS1s. Multi-variate linear fits among the radio luminosity, X-ray luminosity, and radio loudness for RD-NLS1s and RD-BLS1s support a multi-wavelength emission connection associated with jets.