Model [i]

• Based on RAMSES-RT (Rosdahl+13)
• Out-of-equilibrium chemistry (Katz 23)
  Primordial species: \(\text{H~{\small I}-{\small II}}\), \(\text{He~{\small I}-{\small III}}\), \(e^{-}\)
  Metal ions: \(\text{C~{\small I}-{\small VI}}\), \(\text{N~{\small I}-{\small VII}}\), \(\text{O~{\small I}-{\small VIII}}\), \(\text{Ne~{\small I}-{\small X}}\), \(\text{Mg~{\small I}-{\small X}}\), \(\text{Si~{\small I}-{\small XI}}\), \(\text{S~{\small I}-{\small XI}}\) & \(\text{Fe~{\small I}-{\small XI}} \)
  Molecules: \(\text{H}_2\) & \(\text{CO}\)
• Dust model (Rémy-Ruyer+14)
  Assuming dust-to-gas ratio
• Heating & Cooling
  photoheating, photoelectric heating, excitation/dissociation heating, primordial, dust recombination, dust-gas collisions, metal lines
  • \(\text{C~{\small I}}\), \(\text{C~{\small II}}\), \(\text{N~{\small II}}\), \(\text{O~{\small I}}\), \(\text{O~{\small III}}\), \(\text{Ne~{\small II}}\), \(\text{Si~{\small I}}\), \(\text{Si~{\small II}}\), \(\text{S~{\small I}}\), \(\text{Fe~{\small I}}\), \(\text{Fe~{\small II}}\)

\(\text{O\small{II}}\)

\(\text{O\small{I}}\)

\(\text{N\small{I}}\)

\(\text{Mg\small{II}}\)

\(\text{Ne\small{II}}\)

\(\text{CO}\)

\(\rho\)

\(v_r\)

\(\text{O\small{III}}\)

Model [ii]

• Turbulence-based star formation (Padoan & Nordlund 11, Agertz+21)
  \(\dot{\rho_\star} = \varepsilon_\star\rho/t_\mathrm{ff}\)
  • if \(Z<10^{-6}Z_\odot\) ⇒ Pop. III
  • if \(Z\geq10^{-6}Z_\odot\) ⇒ Pop. I & II, Kroupa
• \(M_\star = 500\,\mathrm{M}_\odot\)
  \(M_{\star,\rm III} \sim 100\,\mathrm{M}_\odot\)
• Feedback (Agertz+21; Rey+23)
  core-collapse SN, type Ia, winds + HN (Nomoto+06).
• Yields (Limongi & Chieffi 18)
  AGB winds (Ritter+18)

Model [iii]

• MW analogue @ \(z=0\)
• Genetically engineered to form earlier
  ICs generated with genetIC
• 2 main runs
  • constant physical \(\Delta x_\mathrm{min} \approx 20-40\,\mathrm{pc}\)
    3 runs with ≠ ICs
  • constant comoving \(\Delta x_\mathrm{min}(z=2) = 20\,\mathrm{pc}\)
    \(\Delta x_\mathrm{min}(z=5)=10\,\mathrm{pc}\)
    \(\Delta x_\mathrm{min}(z=14)=4\,\mathrm{pc}\)
    3 runs: efficient feedback, variable IMF, hypernova

• Early forming MW mass galaxy
• \(1.6\times 10^{4}\mathrm{M}_\odot\) DM, \(500\, \mathrm{M}_\odot\) Pop. II stars, individual Pop III stars, \(1\, \mathrm{pc}\) resolution at first star formation
• IMF sampled chemical enrichment from individual stars for all relevant elements
• SN (CC, Ia, HN, PISN), Winds → follows Vintergatan (validated for MW galaxies at z = 0)
• 81 species chemistry coupled to 8 bin RT
• PRISM ISM model
• Enhanced resolution in the CGM
• Calibration sims with IMF variations and physical model variations

Introducing MEGATRON

Mocks in absorption:

Main object, \(z=4\), raw file outputs, no postprocessing

The Megatron suite of simulations

The Megatron suite of simulations

4 High-z ISM

The Megatron suite of simulations

4 High-z ISM

3+2 "low"-z CGM

RTZ model

\[ \frac{\mathrm{d}n_i}{\mathrm{d}t} = \textcolor{red}{n_{i+1}\alpha_{i+1}n_\mathrm{e}} + \left(\sum_k [ \textcolor{blue}{n_{i+1}\xi_{i+1}}+ \textcolor{green}{n_{i-1}\chi_{i-1}}]n_k\right)\! + n_{i-1}(\textcolor{purple}{\beta_{i-1}n_\mathrm{e}} + \textcolor{brown}{\Gamma_{i-1}})\\ \]

\(\textcolor{red}{X^+ + e^- \rightarrow X }\)              (recombination)

\(\textcolor{blue}{X^+ + Y \rightarrow X + Y^+}\)     (charge exchange recombination)

\(\textcolor{green}{X^- + Y \rightarrow X + Y^-}\)     (charge exchange ionization)

\(\textcolor{purple}{X + e^{-*} \rightarrow X^+ + 2e^-} \)  (collisional excitation)

\(\textcolor{brown}{X + h\nu \rightarrow X^+ + e^-} \)     (photoionization)

\[ \frac{\mathrm{d} E}{\mathrm{d}t} = \sum_{k}^{\mathrm{processes}}\sum_i^{\mathrm{species}} n_i \Gamma_k - \sum_{k}^{\mathrm{processes}}\sum_i^{\mathrm{species}}\sum_j^{\mathrm{species}} n_i n_j \Lambda_k\]

Katz 22, Katz+22, Katz+CC+24

\[- \ \textcolor{red}{n_i \alpha_i n_\mathrm{e}} - \left(\sum_k[ \textcolor{blue}{n_i\xi_i} + \textcolor{green}{n_i\chi_i}]n_k\right) - n_i(\textcolor{purple}{\beta_i n_\mathrm{e}} + \textcolor{brown}{\Gamma_i})\]

RTZ model

\[ \frac{\mathrm{d}n_i}{\mathrm{d}t} = \textcolor{red}{n_{i+1}\alpha_{i+1}n_\mathrm{e}} + \left(\sum_k [ \textcolor{blue}{n_{i+1}\xi_{i+1}}+ \textcolor{green}{n_{i-1}\chi_{i-1}}]n_k\right)\! + n_{i-1}(\textcolor{purple}{\beta_{i-1}n_\mathrm{e}} + \textcolor{brown}{\Gamma_{i-1}})\\ \]

\[- \ \textcolor{red}{n_i \alpha_i n_\mathrm{e}} - \left(\sum_k[ \textcolor{blue}{n_i\xi_i} + \textcolor{green}{n_i\chi_i}]n_k\right) - n_i(\textcolor{purple}{\beta_i n_\mathrm{e}} + \textcolor{brown}{\Gamma_i})\]

\[ \frac{\mathrm{d} E}{\mathrm{d}t} = \sum_{k}^{\mathrm{processes}}\sum_i^{\mathrm{species}} n_i \Gamma_k - \sum_{k}^{\mathrm{processes}}\sum_i^{\mathrm{species}}\sum_j^{\mathrm{species}} n_i n_j \Lambda_k\]

• CR heating
• photoheating
• \(\mathrm{H}_2\) heating (formation, dissoc., pumping)

• H+He cooling (\(T>8000\,\mathrm{K}\))
• \(\mathrm{H}_2\) cooling (esp. \(Z < 10^{-5}\))
• metal-line cooling
  fine-structure O I, O III, C I, C II, N II, Fe I, Fe II, Si I, Si II, S I, Ne II @ \(T<10^{4}\,\mathrm{K}\)
  otherwise cloudy table
• CO cooling + dust recombination + grain-gas collisional cooling

Katz 22, Katz+22, Katz+CC+24

State of the CGM of a MW progenitor at \(z \approx 3-4\)

CGM at \(z \approx 3-4\)

CGM at \(z \approx 3-4\)

\[ \frac{\mathrm{d}n_i}{\mathrm{d}t} = \textcolor{red}{n_{i+1}\alpha_{i+1}n_\mathrm{e}} + \left(\sum_k [ \textcolor{blue}{n_{i+1}\xi_{i+1}}+ \textcolor{green}{n_{i-1}\chi_{i-1}}]n_k\right)\! + n_{i-1}(\textcolor{purple}{\beta_{i-1}n_\mathrm{e}} + \textcolor{brown}{\Gamma_{i-1}})\\ \]

\[- \ \textcolor{red}{n_i \alpha_i n_\mathrm{e}} - \left(\sum_k[ \textcolor{blue}{n_i\xi_i} + \textcolor{green}{n_i\chi_i}]n_k\right) - n_i(\textcolor{purple}{\beta_i n_\mathrm{e}} + \textcolor{brown}{\Gamma_i})\]

RTZ model

• Out of equilibrium
• Depends on past thermochemical state
• Depends on local radiation field through \(\Gamma\)
• Ion-ion dependencies

\[ \frac{\mathrm{d}n_i}{\mathrm{d}t} = \textcolor{red}{n_{i+1}\alpha_{i+1}n_\mathrm{e}} \phantom{+ \left(\sum_k [ \textcolor{blue}{n_{i+1}\xi_{i+1}}+ \textcolor{green}{n_{i-1}\chi_{i-1}}]n_k\right)}\! + n_{i-1}(\textcolor{purple}{\beta_{i-1}n_\mathrm{e}} + \textcolor{brown}{\Gamma_{i-1}})\\ \]

\[- \ \textcolor{red}{n_i \alpha_i n_\mathrm{e}} \phantom{- \left(\sum_k[ \textcolor{blue}{n_i\xi_i} + \textcolor{green}{n_i\chi_i}]n_k\right)} - n_i(\textcolor{purple}{\beta_i n_\mathrm{e}} + \textcolor{brown}{\Gamma_i})\]

Photoionization equilibrium

Photoionization equilibrium

\[0 = \textcolor{red}{n_{i+1}\alpha_{i+1}n_\mathrm{e}}+ n_{i-1}(\textcolor{purple}{\beta_{i-1}n_\mathrm{e}} + \textcolor{brown}{\Gamma_{i-1}})- \ \textcolor{red}{n_i \alpha_i n_\mathrm{e}} - n_i(\textcolor{purple}{\beta_i n_\mathrm{e}} + \textcolor{brown}{\Gamma_i}) \]

• In equilibrium
• Suppose \(n_\mathrm{e} = n_\mathrm{H\,II} + n_\mathrm{He\,II} + 2n_\mathrm{He\,III}\)
• Suppose \(\Gamma\) is UV background only

CGM at \(z \approx 3-4\)

Is the CGM in equilibrium?

CGM at \(z \approx 3-4\)

Is the CGM in equilibrium?

\(\Sigma \propto n\)

\(L \propto n^2\)

CGM at \(z \approx 3-4\)

Is the CGM in equilibrium?

CGM at \(z \approx 3-4\)

Is the CGM in equilibrium?

NEq.

PIE

Assuming PIE ⇒ biased towards colder/denser gas

\(n_\mathrm{H}\)

CGM at \(z \approx 3-4\)

Is the CGM in equilibrium?

\(\pm0.5\,\mathrm{dex}\)

CGM at \(z \approx 3-4\)

Is the CGM in equilibrium?

Non-equilibrium effects:

\(\Delta(T, n_\mathrm{H}) \sim 0.2-0.5\,\mathrm{dex}\)

CGM at \(z \approx 3-4\)

CGM out of equilibrium: why?

40 kpc

1. Local radiation dominate locally over UVB
   Anisotropic effects
    
2. Recombination lag
   \(t_\mathrm{cool} \ll t_\mathrm{rec}\), worse with time

CGM at \(z \approx 3-4\)

CGM out of equilibrium: why?

1. Local radiation dominate locally over UVB
   Anisotropic effects
    
2. Recombination lag
   \(t_\mathrm{cool} \ll t_\mathrm{rec}\), worse at low \(z\)

Recombination lag in the CGM

fast cooling,
slow recombination

slow cooling,
fast recombination

Upcoming: MEGATRON data release

Data viewer

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  (RAMSES outputs, catalogues, spectra)
• ✔ everything local — except data.
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