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Identification of Large-Scale (>100 kpc) Radio Jets in Narrow-Line Seyfert 1 Galaxies

S. Umayal, Vaidehi S. Paliya, D. J. Saikia, C. S. Stalin, S. Muneer, Maheswar Gopinathan

TL;DR

This study tests whether narrow-line Seyfert 1 (NLSy1) galaxies can host large-scale radio jets, challenging the view that such jets require massive elliptical hosts. By cross-matching a large NLSy1 catalog with diverse radio surveys and overlaying optical imaging, the authors identify 34 NLSy1s with $D_{ ext{proj}} \ge 100\,\mathrm{kpc}$, including a 4.3 Mpc jet in J1318+2626. The sample reveals diverse FR morphologies (10 FR II, 21 FR I, 3 FR I–II) with a median size around 285 kpc, and LOFAR data prove crucial for detecting diffuse emission, uncovering four giant radio galaxies. The findings imply orientation alone does not set black hole masses and indicate a potentially larger population of large-scale jets in NLSy1s, motivating deeper, next-generation surveys to map jet formation and evolution in low-mass black hole systems.

Abstract

Powerful, large-scale relativistic jets are usually associated with massive, old elliptical galaxies. This paradigm has recently been challenged by the identification of narrow-line Seyfert 1 (NLSy1) galaxies, thought to be young active galactic nuclei with low-mass black holes, harboring relativistic jets. Among them, sources hosting $>$100 kpc radio jets are extremely rare. Here, we report the discovery of large-scale, double-lobed radio structures in 33 NLSy1s with the projected linear size of at least 100 kpc from a recently published catalog of 22656 NLSy1 galaxies. These 33 include 29 confirmed double-lobed sources and 4 candidates whose radio structure requires further study. We suggest that their low black hole masses are unlikely to be due to their small angles of inclination to the line of sight. These enigmatic sources were identified by examining the radio observations taken with the Faint Images of the Radio Sky at Twenty centimeters, Very Large Array Sky Survey, Low Frequency Array, and Rapid ASKAP Continuum Survey. Among them, the NLSy1 source J1318+2626 ($z=0.62$) is found to host a radio jet with the projected linear size of 4.3 Mpc, making it the only NLSy1 galaxy hosting a Mpc-scale radio jet known as of today. We conclude that future observations of NLSy1 sources with the next generation of sensitive telescopes may reveal a much larger population harboring large-scale jets, thus providing crucial clues on their origin, propagation, and interaction with the ambient environment.

Identification of Large-Scale (>100 kpc) Radio Jets in Narrow-Line Seyfert 1 Galaxies

TL;DR

This study tests whether narrow-line Seyfert 1 (NLSy1) galaxies can host large-scale radio jets, challenging the view that such jets require massive elliptical hosts. By cross-matching a large NLSy1 catalog with diverse radio surveys and overlaying optical imaging, the authors identify 34 NLSy1s with , including a 4.3 Mpc jet in J1318+2626. The sample reveals diverse FR morphologies (10 FR II, 21 FR I, 3 FR I–II) with a median size around 285 kpc, and LOFAR data prove crucial for detecting diffuse emission, uncovering four giant radio galaxies. The findings imply orientation alone does not set black hole masses and indicate a potentially larger population of large-scale jets in NLSy1s, motivating deeper, next-generation surveys to map jet formation and evolution in low-mass black hole systems.

Abstract

Powerful, large-scale relativistic jets are usually associated with massive, old elliptical galaxies. This paradigm has recently been challenged by the identification of narrow-line Seyfert 1 (NLSy1) galaxies, thought to be young active galactic nuclei with low-mass black holes, harboring relativistic jets. Among them, sources hosting 100 kpc radio jets are extremely rare. Here, we report the discovery of large-scale, double-lobed radio structures in 33 NLSy1s with the projected linear size of at least 100 kpc from a recently published catalog of 22656 NLSy1 galaxies. These 33 include 29 confirmed double-lobed sources and 4 candidates whose radio structure requires further study. We suggest that their low black hole masses are unlikely to be due to their small angles of inclination to the line of sight. These enigmatic sources were identified by examining the radio observations taken with the Faint Images of the Radio Sky at Twenty centimeters, Very Large Array Sky Survey, Low Frequency Array, and Rapid ASKAP Continuum Survey. Among them, the NLSy1 source J1318+2626 () is found to host a radio jet with the projected linear size of 4.3 Mpc, making it the only NLSy1 galaxy hosting a Mpc-scale radio jet known as of today. We conclude that future observations of NLSy1 sources with the next generation of sensitive telescopes may reveal a much larger population harboring large-scale jets, thus providing crucial clues on their origin, propagation, and interaction with the ambient environment.

Paper Structure

This paper contains 10 sections, 3 equations, 5 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Sample Selection
  3. Multiwavelength Catalogs and Search Strategy
  4. Results and Discussion
  5. Radio structure and sizes
  6. Comparison with radio-detected NLSy1s
  7. Orientation and core dominance
  8. Radio luminosity-Projected size diagram
  9. Conclusions
  10. Acknowledgements

Figures (5)

  • Figure 1: Total intensity maps of all the 34 NLSy1 sources, with projected sizes of at least 100 kpc. The background grey images are the Pan-STARRS r-band images, while the contours are the radio images from VLASS (red), FIRST (green), LOFAR 6$\hbox{$^{\prime\prime}$}$ resolution (orange), LOFAR 20$\hbox{$^{\prime\prime}$}$ resolution (blue) and RACS-low (violet). The contour levels are at 3$\sigma \times [-(\sqrt{2}^m), (\sqrt{2})^n]$ with m=0 and n=[0, 1, 2, 3, 4, 5,...] mJy/beam. The dashed contours represent negative values. The lower left corner of each image shows the beams of the different surveys. The names of the sources are given in the respective panels.
  • Figure 1: (Continued) Total intensity maps of NLSy1 sources.
  • Figure 2: Distributions of (a) redshift z, (b) Bolometric luminosity and (c) radio loudness parameter are shown in the upper panels; while those of (d) absolute B magnitude, (e) mass of BHs and (f) Eddington ratio are shown in the bottom panels. The radio-detected NLSy1 sources plotted in gray do not include the $>$100 kpc NLSy1s.
  • Figure 3: Upper: Histogram of the estimated core dominance of the NLSy1s listed in Table \ref{['table-2']}. Lower: Relation between core dominance and black hole mass.
  • Figure 4: Power vs projected size (P--D diagram) plot of all the double-lobed NLSy1 sources $>$ 100 kpc (listed in Table \ref{['table-2']}) overlaid onto LOFAR$-$detected sources published in Hardcastle2023.