Formation of mega-parsec giant radio sources from hosts residing in dark matter halos of different masses and with normal hot baryonic gas fractions

Abstract

Mega-parsec giant radio sources (GRSs) have been known for decades. Their known population has soared from several hundred to more than $10^4$ in recent years. However, the formation mechanisms of GRSs remain elusive, and one explanation suggested is that they form in a low-density environment. In this work, we study the formation and properties of GRSs associated with dark matter halos of different masses and normal gas density environment. This study can lay the groundwork for future observations aimed at probing the gas environment, particularly the baryonic gas fraction, in the host dark matter halos of GRSs. We use magnetohydrodynamic simulations to study the formation of GRSs from hosts residing in dark matter halos with masses of $10^{13}$, $10^{14}$ and $10^{15}$ solar masses, adopting normal hot baryonic gas fractions (0.02, 0.05, and 0.1). We inject jet energy of 0.06 percent of the central black hole's relativistic energy in their host galaxies with power of 0.05 percent of the Eddington luminosity. The successful formation of GRSs from hosts in all three dark matter halos with normal hot baryonic gas fractions indicates that an unusual low-density gas environment is not a necessary condition for their formation. The jetted lobe growing from hosts in dark matter halo of $\rm 10^{13}$ solar masses exhibits a wider shape than those in dark matter halos of $\rm 10^{14}$ and $\rm 10^{15}$ solar masses. The evolution of the simulated GRSs in the radio power-linear size diagram shows that their radio power can reach values comparable to observational data at similar physical scales. Furthermore, the radio power typically increases with dark matter halo mass. When we simulate a higher-power jet in a lower-mass dark matter halo, the results reveal a deviation from the simple linear relation between jet power and radio luminosity.

Figures (5)

• Figure 1: Evolution of the traveling distance $\rm r_h$ of the bubble heads (one-sided scale of the GRSs, top panel) and the lobe width $\rm w_{lobe}$ varying with $\rm r_h$ (bottom panel). The vertical dotted lines in the top panel indicate the times when the jets are shut off, while the horizontal dashed lines denote the virial radius of the dark matter halos. Different line colors represent different dark matter halo masses.
• Figure 2: Evolution of the simulated radio sources in the P-D diagram (top panel) and the relation between power and radio power (luminosity) of jets at three typical scales (50kpc, 800kpc and 1200kpc) of radio sources (bottom panel). In top panel, different line colors represent different masses of dark matter halos. The radio power is calculated at 144(1+z) MHz, where we adopt redshift $\rm z=0.2$. The data points utilized in this analysis are sourced from dabhade20a with in the redshift range $\rm 0.1 < z <0.3$. In bottom panel, different line colors represent different scales of the simulated radio sources plotted in the top panel. The dotted line show the linear related given by hardcastle18: $\rm P_{radio}(150MHz) = 3\times 10^{27} (P_{jet}/10^{38} W)\ W Hz^{-1}$.
• Figure 3: Profiles of electron number density, temperature, and pressure for dark matter halos of virial mass ($\rm M_{\rm vir}$) $10^{13}$ (black), $10^{14}$ (blue), and $10^{15}$ (red) solar masses. The dotted lines for density and pressure correspond to hot gas fractions ($\rm f_{g}$) lower than the adopted normal value. The temperature profiles are independent of the gas fraction in our model. Profiles outside the virial radius are fitted as extensions of the inner profiles.
• Figure 4: Snapshots of the density distribution for our four runs, captured when the bipolar radio lobes reach a scale of about 1 Mpc.
• Figure 5: Density snapshots for runs of jets injected with kinetic energy dominant, taken when the bipolar lobes reach $\sim 1$ Mpc. The runs M13fk9, M14fk9, and M15fk9 differ from M13, M14, and M15 solely in their injected energy fractions: $\rm f_k = 0.9$ (kinetic), $\rm f_m = 0.05$ (magnetic), and $\rm f_{th} = 0.05$ (thermal).