AGN Disks as Supernova Mufflers I: 3D Local Hydrodynamic Models

Abstract

Supernova (SN) shocks that originate from stars on orbits embedded in dense active galactic nuclei (AGN) accretion disks evolve differently from those that occur in the interstellar medium. We aim to assess how shocks evolve in this dense stratified medium and understand where SNe are muffled and have their kinetic energy absorbed by an AGN disk versus escaping. We use Sirko \& Goodman (SG) and Thompson, Quataert \& Murray (TQM) AGN disk models for midplane radial profiles, generated with the pAGN code; we compare the disk pressure to the energy of a standard core-collapse SN ($10^{51}\,{\rm erg}$) to find radii where shock breakout can occur. For verification, we evolve three-dimensional hydrodynamic shearing box simulations of stratified Gaussian disks constructed from the midplane values that are injected with energy and mass from SNe placed at multiple radii and vertical locations, using the Athena code. We find SN shocks in SG disks around black holes with mass $\Mbh=10^6\,\Msun$ become muffled beyond $R\sim10^6\,\Rs$, and that this muffling radius is inversely proportional to supermassive black hole (SMBH) mass with muffling occurring at $R\sim10^2\,\Rs$ for $\Mbh=10^9\,\Msun$. Around TQM disks, the muffling radius occurs at $R\sim10^6\,\Rs$, independent of $\Mbh$. The largest determining factor for muffling a SN shock is the local scale height of the AGN disk. In conclusion, we developed a predictive analytic criterion to identify where AGN disks can muffle SNe shocks depending on their density and vertical scale.

Figures (5)

• Figure 1: SirkoGoodman03 (left column) and Thompson+05 (right column) accretion disk models of midplane density (A, B), midplane temperature (C, D), local scale height (E, F), and optical depth (G, H) as functions of radius for disks orbiting various SMBH masses. Vertical lines indicate where $\mathcal{C}=1$ for accretion disk models corresponding to SMBH with the same line style.
• Figure 2: Breakout parameter $C$ versus SMBH mass and radius in the accretion disk for SNe detonating at the disk midplane. Top Panel: In SG disks around SMBH with mass $10^6\,M_{\odot}$, SNe with energy $10^{51}\,{\rm erg\ s}^{-1}$ will strongly break free from all radii $\leq5\times10^6\,R_{\rm s}$. The muffling radius decreases in $R_{\rm s}$ as SMBH mass increases, reaching $10^2R_{\rm s}$ for those with $M=10^9\,M_{\odot}$. Stars indicate the $M_{\rm BH}$ and radial locations we use to set up our hydrodynamic shearing box simulations to test this prediction. The dashed line marks where Moranchel+21 calculated the muffling radius for SNe when radiative cooling is not important (their scenario A) which closely matches the line for $\mathcal{C}=1$. The dotted line marks their scenario B in which radiative cooling becomes important by the free expansion phase, reducing the pressure interior to the shell. Bottom Panel: The same for TQM disks. The location of the muffling radius is located at $R_{\rm m}=10^6\,R_{\rm s}$ for all SMBH masses.
• Figure 3: Breakout parameter $\mathcal{C}$ for SNe at height $z=1\,H$ for an SG disk. The lower density offers less resistance to the shock expansion, making breakout easier, and pushing the muffling boundary outward compared to midplane detonations in Fig. \ref{['fig:breakout-midplane']}. The star marks the location that our off-midplane run samples this analytic prediction.
• Figure 4: Time series of vertical slices ($x-z$) showing the gas volume density evolution for SNe embedded in accretion disks around an SMBH with mass $M=10^8\,M_{\odot}$. Top row: Midplane detonation at $R=10^3\,R_{\rm s}$. Middle row: Midplane detonation at $R=10^5\,R_{\rm s}$. Bottom row: Offset detonation ($z=1H$) at $R=10^3\,R_{\rm s}$.
• Figure 5: Time series of midplane slices ($x-y$) showing the gas volume density evolution for SNe embedded in accretion disks around an SMBH with mass $M=10^8\,M_{\odot}$. Top row: Midplane detonation at $R=10^3\,R_{\rm s}$. Middle row: Midplane detonation at $R=10^5\,R_{\rm s}$. Bottom row: Offset detonation ($z=1H$) at $R=10^3\,R_{\rm s}$.