Modelling CGM in emission/absorption

Corentin Cadiou

CNRS @ IAP, Paris

C-line d'Ion in the NIR, far, wherever they are

Modelling ions in the CGM: a view from the Megatron simulations

Co-Is: Harley Katz, Martin Rey

Collaborators: Agertz, Blaizot, Cameron, Choustikov, Devriendt, Jones, Kimm, Saxena, Martin-Alvarez, Matsumato, Pearce, Rodriguez-Montero, Rosdahl, Slyz, Stiskalek, Storck, Yee

Tillson+15

Dekel&Birnboim 06

High-\(z\):
most of mass + AM flow along filaments

⇒ Natural interface between cosmo scales & galaxy formation
Circum Galactic Medium (\(r>R_\mathrm{vir}/3\))

Modelling challenge:

space filling (\(\sim 30\times\) more \(V\) in CGM than ISM);
low-density (\(\lessapprox 10^{-2}\,\mathrm{m_p/cm^{-3}}\));
multiphase (see rev. by Fumagali 24);

Gible project, Ramesh+24

Observables in the CGM?

Absorption

Emission

Zou+24

Pen+25 (\(z\approx2.8\))

How we typically model ion abundances & lines

Lots of assumptions

(equilibrium, geometry, element abundances, …)

\(\rho, T, Z,v\)
sometimes \(n_\mathrm{H}, n_{\mathrm{HI}}, n_\mathrm{HeI}, n_\mathrm{HeII},n_\mathrm{HeIII},\)

Cooling and chemical timescales go as \(n^2\)

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

\(\Sigma\)HI

\(\Sigma\)HII

\(\Sigma\)MgII

\(\Sigma\)OII

\(\Sigma\)OI

\(\Sigma\)OII

\(\Sigma\)OIII

Create “twin” simulation relaxed to photo-ionization equilibrium (PIE):

Haardt-Madau UV bg,
Local Habing field (\(6-13.6\,\mathrm{eV}\)),
Dust-to-gas ratio (Rémy-Ruyer+14),
Iterate until

\(\dfrac{\mathrm{d} n_{X_i}}{\mathrm{d} t} = 0\quad\) at fixed \(T\).

Code: Katz & CC, in prep.

Electron abundances

\(M_\star \approx 10^{10}\,M_\odot, \quad z=4\)

Effect on \(\mathrm{He\,III}\)

Data within \(r>R_\mathrm{vir}/4\)

\(M_\star \approx 10^{10}\,M_\odot, \quad z=4\)

Effect on \(\mathrm{He\,II}\)

\(M_\star \approx 10^{10}\,M_\odot, \quad z=4\)

Overall trend:

high-ionization lines boosted with neq

\(M_\star \approx 10^{10}\,M_\odot, \quad z=4,\quad r>R_\mathrm{vir}/4\)

Overall trend:

lower-ionization lines damped with neq

\(M_\star \approx 10^{10}\,M_\odot, \quad z=4,\quad r>R_\mathrm{vir}/4\)

Overall trend:

intermediate-ionization lines unchanged

HeII @ (PIE)

\(M=1.2\,10^9\,\mathrm{M_\odot}\)

HeII @ (neq)

\(M=8.8\,10^8\,\mathrm{M_\odot}\)

+\(30\%\)

[CIII]\(\lambda\lambda 1907\rm Å\) @ (PIE)

[CIII]\(\lambda\lambda 1907\rm Å\) @ (neq)

[CIII]\(\lambda\lambda 1907\rm Å\) @ (PIE)

[CIII]\(\lambda\lambda 1907\rm Å\) @ (neq)

[OIII]\(\lambda\lambda 1664\rm Å\) @ (PIE)

[OIII]\(\lambda\lambda 1664\rm Å\) @ (neq)

[OIII]\(\lambda\lambda 1664\rm Å\) @ (PIE)

[OIII]\(\lambda\lambda 1664\rm Å\) @ (neq)

Cooling length refinment

Refining where

\( \Delta x > 2 \sqrt{\dfrac{P_\mathrm{th}}{\rho}}\times {t_\mathrm{cool}},\)

(Rey+23)

up to \(80\,\mathrm{pc}\)
turned on at key moments

Cooling length refinment

\(+120\,\mathrm{Myr}\)

Quasi-Lagrangian + Jeans

Quasi-Lagrangian + Jeans + CGM ref

\(\mathrm{CII\, 158µm}\)

\(\mathrm{OIII\, 88µm}\)

Take home messages

Megatron simulation suite
200,000+ spectra in 3 “ISM” runs (\(z\gtrapprox 8\)) ⇒ Katz, CC+in prep.
3 “CGM” runs (\(z\gtrapprox 3.5\)) ⇒ CC+in prep.
Link to near-field cosmology ⇒ Rey, CC+ in prep.
Do we really need out-of-equilibrium thermochemistry?
To compare to observations: yes (but depends on the line/ion)!
For self-consistency: yes!
Does resolution matter?
Effect on CGM structures (e.g., [OIII] emission, column densities?)
Really good resolution (\(<100\,\mathrm{pc}\)) achievable
Bonus: can we visualize high-res simulations on the fly?
Come to the yt hack session!

(My) route to high-\(z\) kinematics

Effect of cosmo. env. (Musso+19, Kraljic+20,21, Cadiou+21, Storck+24)
Cosmology-galaxy connection (Cadiou+21)
Cosmological accretion (Cadiou+19, Kocjan+24)
But what are we actually observing? This talk

Low grav. tides

Large grav. tides

cosmological environment \(\sim 50-100\,\mathrm{Mpc}\)
resolve Strömgren spheres \(\sim 10\,\mathrm{pc}\)
radiative-transfer
proper multi-phase ISM \(T \lesssim 10^4\,\mathrm{K}\)
Track ion abundances out-of-equilibrium

Wishlist for proper modelling of emission lines + kinematics

Background: Vintage Gordon (follow-up of Vintergatan) simulation
(PI: Cadiou)

\(t_\mathrm{chem} \propto 1/n^2\)

\(t_\mathrm{dyn} \propto 1/\sqrt{n}\)

\(t_\mathrm{burst} \sim 10-100\,\mathrm{Myr}\)

Processes that control ion and molecular properties:

Collisional, photo, cosmic-ray ionization
Radiative, dielectronic, dust recombination
Charge exchange

RAMSES-RTZ + PRISM: Non-equilibrium chemistry coupled to on-the-fly radiative transfer

Processes that control gas temperature:

Cosmic-ray, photo, photo-electric, H2, dust heating
Primordial, \(\mathrm{H}_2\), CO, metal, dust* recombination, dust-gas collisional cooling
Adiabatic (expansion), shocks (e.g. SN, turbulence), gravitational, etc.

Image: Cadiou/Katz/Rey+in prep

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)
82 species chemistry coupled to 8 bin RT
PRISM ISM model
Enhanced resolution in the CGM
Calibration sims with IMF variations and physical model variations