Nick Gnedin The Brief History of Time End of inflation: Today: - - PowerPoint PPT Presentation

Faintest Galaxies in the JWST Era

Nick Gnedin

The Brief History of Time

Today: z=0 t=13.7 Gyr End of inflation: z=1027 t=10-36s

The Brief History of Time

ionized neutral ionized RE-IONIZATION

What We Know Now : Galaxy Luminosity Functions

• Data (may) exist all the way to z=10 and MUV=-13.

Livermore+ 2016 Bouwens+2015

108L 106L

= -2.5 log10(L*)+5

What We Know Now : Galaxy Luminosity Functions

• High redshift galaxies are not particularly glaring.
• The faintest ones are detected with the help of

gravitational lensing in HST Frontier Fields.

The Flood Is Coming: JWST

• James Webb Space Telescope (JWST) is the

primary NASA mission for the next decade. Launch date: 2021? Destination: L2 Mirror: 6 meters

The Flood Is Coming: JWST

• Studying reionization sources is the primary

science goal of JWST. Mason+ 2015

• It will perform a

range of surveys of varying depth, greatly improving precision of luminosity functions, as well as studying individual galaxies.

• 25
• 15
• 13

Covered with lensing

The Flood Is Coming

• Reionization research is on the brink of a major

breakthrough(s). Forthcoming observations will make all existing models obsolete.

• Hence, theorists’ task is not to make more models

now, but rather to develop new modeling technology.

• And it is happening:
• Aurora
• Cosmic Dawn
• CRASH
• CROC
• DRAGONS
• Emma
• Renaissance Simulations
• SPHINX

The Flood Is Coming

• One (typical) example in action:
• Disclaimer: other projects/efforts are achieving

similar overall levels of computational scale, agreement with data, etc.

Simulating Reionization: Physics

• Dark matter
• Gas dynamics
• Atomic processes
• Radiative transfer
• Star formation &

stellar feedback

Simulating Reionization: Physics

• Star formation & stellar feedback are modeled as

a sub-grid recipe. We are not starting from scratch, just using what is shown to work by low-z projects (Illustris, EAGLE, NIHAO, MUFASA, …).

Simulating Reionization: Scales

• Capturing most of star-forming galaxies requires

boxes ~ 50-100 Mpc (comoving).

• Resolving star formation requires resolution

~100-200 pc (depends on your sub-grid model).

• Resolving all star-forming galaxies requires mass

resolution of about 106 M.

• Conclusion: we need simulations with
• spatial dynamic range L/∆x ~ 100,000
• mass dynamic range Mbox/Mcell ~ 10 billion

Moore’s Law

Doubling in speed every 13 months REIONIZATION

Simulating Reionization: CROC on Blue Waters

Box size: 120 Mpc Resolution: 100 pc

CROC in Blue Waters

The CROC Project: Convergence Study

Mass Space

100 pc 60 Mpc 120 Mpc 1017 M 107 M 106 M

The CROC Project: Success

• Galaxies (and many other things) are ok!

The Role of JWST: There Will Be Blood!

• All simulation agree with

the data where the data exist.

• They all disagree (for a

good reason!) strongly in the regime that JWST will probe.

• JWST will kill most (or

all) existing models. JWST

Take Aw ay Points

• Models will not die in vain – they differ for

physical reasons, encapsulating our ignorance

• f star formation and stellar feedback.
• JWST measurements will strongly constraint

such models, telling us important information about “sub-grid” processes (for example, whether stars can form in atomic gas).

• We are entering a golden age of reionization

studies, with observations and theory in good balance to ensure rapid progress.

• Lots of fun ahead…

The End