Probing AGN duty cycle and cluster-driven morphology in a giant episodic radio galaxy

TL;DR

This study investigates the duty cycle and environment-driven morphology of the giant radio galaxy J1007+3540 in a cluster, using LOFAR 144 MHz and uGMRT 400 MHz data plus optical/IR SED modelling. It reveals clear signs of episodic jet activity, with inner lobes aging ~$t_{ m rad} obreaksim140$ Myr and outer relic structures ~ $t_{ m rad} obreaksim240$–260 Myr, and a diffuse southwestern tail showing evidence of re-acceleration and a relatively young $t_{ m rad} obreaksim100$ Myr. The host is an evolved elliptical with $ obreaksim10^{11} M_ot$, hosting a radiatively efficient yet obscured AGN ($L_{ m AGN} obreaksim6 imes10^{44}$ erg s$^{-1}$) and a high infrared SFR ($ obreaksim106~M_ot$ yr$^{-1}$), suggesting merger-driven fueling. X-ray data from eROSITA indicate cluster-scale hot gas ($T_X obreaksim1.8$ keV; $L_X obreaksim3.2 imes10^{43}$ erg s$^{-1}$), consistent with strong jet–ICM interaction. Overall, the work demonstrates how dense cluster environments can prolong radio lifetimes, shape jet duty cycles, and support re-acceleration in fossil plasma, offering a valuable laboratory for AGN feedback and galaxy–cluster co-evolution.

Abstract

The evolution of radio jet morphology and its energetics is significantly influenced by the environment in which the host galaxy resides. As giant radio galaxies (GRGs) often extend to the scale of entire galaxy clusters ($\sim$Mpc) and beyond, they are a suitable class of objects for studying jet--intracluster medium interactions. This paper presents a multiwavelength study of a GRG, J1007+3540, using the LOFAR Two-metre Sky Survey second data release (LoTSS DR2) at 144 MHz and the upgraded Giant Metrewave Radio Telescope (uGMRT) at 400 MHz. The source has a projected linear extension of 1.45 Mpc and is hosted by MaxBCG J151.77665+35.67813, within the WHL 100706.4+354041 cluster. At both frequencies, the source exhibits clear signatures of recurrent jet activity, a one-sided, extended, tail-like diffuse structure with a morphological break in the tail. The estimated radiative ages of the inner lobes and outer north lobe are $\sim$140 Myr and $\sim$240 Myr, respectively. In addition to the radio analysis, we performed optical--to--infrared spectral energy distribution modelling. The host galaxy is an evolved elliptical system with a stellar mass of $\log_{10}(M_\star/M_\odot) = 11.0$ and an old stellar population age of $\sim$12 Gyr. The high infrared-derived star formation rate ($\sim106~M_\odot$~yr$^{-1}$) of the source implies significant dust-obscured star formation, potentially linked to merger-driven gas inflows. J1007+3540 presents a rare combination of a restarted jet, a detached tail-like structure, and unusual spectral flattening beyond the tail break, which is very rare to report together in a GRG. This rare and remarkable system offers a unique laboratory for probing the interplay between active galactic nucleus activity, star formation, and environmental effects in cluster-surrounded GRGs.

Figures (8)

• Figure 1: LoTSS DR2 image of J1007+3540 at 144 MHz (in contour) superimposed with Pan-STARRS1 optical r-band image Ch16. The contour levels are at 0.24, 1.3, 2.6, 4.3, 5.2, 6.0, 7.0, 8.0, 8.5, 9.0, 12.2, 20.6, 34.8 mJy beam$^{-1}$. The lowest contour level of J1007+3540 is set at 3$\sigma$, where $\sigma = 80$$\mu$Jy beam$^{-1}$ represents the mean RMS noise measured around the source. The red colour represents the LoTSS DR2 image at 144 MHz, and the green colour represents the Pan-STARRS1 optical image. The upper right-side inset represents the overlaid image of J1007+3540 with LoTSS DR2 at 144 MHz (green contour), VLASS at 3 GHz (red contour), and optical in the background.
• Figure 2: LoTSS DR2 image at 144 MHz at 20$"$ resolution (low-resolution beam). The contour levels are at 0.42, 0.87, 2.07, 2.85, 3.79, 4.91, 6.26, 7.88, 9.83, 12.2, 15.0, 18.3, 22.4, 28.6, 36.3 mJy beam$^{-1}$. The lowest contour level is set at 3$\sigma$, where $\sigma = 0.14$ mJy beam$^{-1}$ represents the mean RMS noise measured around the source. The synthesized beam of J1007+3540, shown as a white circle in the bottom-left corner of the image, has an angular resolution of $20\arcsec \times 20\arcsec$. The colour scale represents the specific intensity of the source in Jy beam$^{-1}$.
• Figure 3: Plot of galaxies resides within the cluster radius of R$_{500}$ = 0.89 Mpc. The large black dashed circle is the locus of all points whose sky-projected distance from the cluster centre is R$_{500}$. Small black circles overplotted on the LoTSS DR2 image (in blue contour) represent optical galaxies within the R$_{500}$. The contour levels are at 0.23, 0.63, 1.60, 2.83, 4.40, 5.34, 6.40, 7.60, 8.96, 10.50, 13.0 mJy beam$^{-1}$. The background image is the optical image taken from the Pan-STARRS Ch16.
• Figure 4: Left: High-resolution uGMRT image of J1007+3540 at 400 MHz (with resolution of $9.20"\times 6.23"$; position angle = 57.85$^{\circ}$). The contour levels are at 0.06, 0.15, 0.28, 0.44, 0.66, 0.96, 1.36, 1.91, 2.64, 3.64, 4.98, 6.79 mJy beam$^{-1}$. The lowest contour level is at 3$\sigma$, where $\sigma=21 \mu$Jy beam$^{-1}$ is the mean RMS around the source. Right: uGMRT image of J1007+3540 at 400 MHz by applying uv taper (with synthesized beam of resolution $21.55" \times 17.3"$; position angle: 48.35$^{\circ}$). The contour levels are at 0.09, 0.19, 0.32, 0.47, 0.67, 0.91, 1.22, 1.60, 2.07, 2.67, 3.42, 4.35, 5.51, 6.97, 8.78 mJy beam$^{-1}$. The lowest contour level is at 3$\sigma$, where $\sigma=30 \mu$Jy beam$^{-1}$ is the mean RMS around the source. The colour scale represents the intensity of the source in Jy beam$^{-1}$.
• Figure 5: Spectral index map of J1007+3540 using LoTSS DR2 at 144 MHz and uGMRT at 400 MHz with $9.20\arcsec \times 9.20\arcsec$ resolution. The contour plot presents the LoTSS DR2 map of J1007+3540 at 144 MHz. The contour levels are at 3$\sigma \times (\sqrt{2})^{n}$, where $n$ = 0, 1, 2, 3,....