TXS 1206+549: a new $\gamma$-ray detected narrow-line Seyfert 1 galaxy at redshift 1.34?

TL;DR

This paper reports the discovery of TXS 1206+549, the most distant gamma-ray emitting narrow-line Seyfert 1 galaxy at redshift 1.344, providing new insights into relativistic jet formation in such objects.

Contribution

The identification of a new gamma-ray NLS1 at high redshift expands the known population and offers valuable data on jet formation and evolution in early universe conditions.

Findings

TXS 1206+549 is the most distant gamma-ray NLS1 known.

The source exhibits typical blazar-like SED and strong multi-wavelength variability.

It has a flat radio spectrum and high radio loudness.

Abstract

Radio and $\gamma$-ray loud narrow-line Seyfert 1 galaxies (NLS1s) are unique objects to study the formation and evolution of relativistic jets, as they are believed to have high accretion rates and powered by low mass black holes contrary to that known for blazars. However, only about a dozen $\gamma$-ray detected NLS1s ($\gamma$-NLS1s) are known to date and all of them are at $z\le1$. Here, we report the identification of a new $\gamma$-ray emitting NLS1 TXS 1206+549 at $z=1.344$. A near-infrared spectrum taken with the Subaru telescope showed H$\beta$ emission line with FWHM of $1194\pm77$ km s$^{-1}$ and weak [O III] emission line but no optical Fe II lines, due to the limited wavelength coverage and poor signal-to-noise ratio. However, UV Fe II lines are present in the SDSS optical spectrum. The source is very radio-loud, unresolved, and has a flat radio spectrum. The broadband SED of the source has the typical two hump structure shown by blazars and other $\gamma$-NLS1s. The source exhibits strong variability at all wavelengths such as the optical, infrared, and $\gamma$-ray bands. All these observed characteristics show that TXS 1206+549 is the most distant $\gamma$-NLS1 known to date.