Connecting the earliest galaxies to the Local Group and Milky Way

Transcription

1 Connecting the earliest galaxies to the Local Group and Milky Way Brian O Shea Michigan State University With: Pengfei Chen (UCSD) David Collins (FSU) Cameron Hummels (Caltech) Michael Norman (UCSD/SDSC) Devin Silvia (MSU) Britton Smith (U. Edinburgh) John Wise (Georgia Tech) Hao Xu (UCSD) NSF PRAC ACI NSF PRAC ACI Blue Waters Symposium, June 13, 2016

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5 Image credit: Anna Frebel (MIT)

6 Image credit: Anna Frebel (MIT)

7 Big questions How do the first stars affect later generations of galaxies? What are the observable properties of the earliest galaxies? How do the earliest galaxies relate to the Milky Way and its environments?

8 Why is studying galaxy formation challenging? 1. Complex physics 2. Dynamic range 3. Statistics/sampling

9 Results The transition to metal-enriched star formation: Britton Smith*, John Wise, BWO Evolution of early galaxy populations: Hao Xu*, Pengfei Chen, Mike Norman, Kyungjin Ahn, BWO * Ran the simulations

10 The transition to metal-enriched star formation 0.5 Mpc/h box 13 levels of AMR prior to explosion (0.119 pc comoving max); 30 after (~1 au comoving) ~0.19 M gas, 0.92 M dm mass resolution Primordial gas + metal + dust chemistry & cooling Radiation transport for Pop III stars; core-collapse supernovae w/11.2 M of metals Britton Smith et al. 2015, MNRAS, 452, 2822

11 Britton Smith et al. 2015, MNRAS, 452, 2822

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14 Evolution of early galaxy populations 40 Mpc box, refine on three separate ~225 Mpc 3 regions (overdense, average, low density) Simulation at 12 levels of AMR (19 comoving pc), primordial + metal-enriched chemistry, Pop III and metal-enriched SF 13,000 Pop III stars formed, ~3,000 halos > 10 7 M (with star formation) by end of simulations Multiple Pop III stars per halo at later times! Hao Xu et al. 2014, 15, 16; Chen et al. 2014; O Shea et al. 2015

15 Movie c/o Bob Patterson, NCSA Advanced Visualization Laboratory

16 Luminosity function of early galaxies O Shea et al. 2015

17 Luminosity function of early galaxies O Shea et al. 2015

18 Luminosity function of early galaxies O Shea et al. 2015

19 Luminosity function of early galaxies Density Detection by Red: HUDF Blue: JWST Ultra-deep Green: JWST + 10x mag. O Shea et al Electron fraction (ionizing radiation)

20 Escape fraction of ionizing radiation Density [g cm 3 ] xh Xu et al. 2016, submitted (arxiv: ) 100

21 Escape fraction of ionizing radiation Xu et al. 2016, submitted (arxiv: )

22 Escape fraction of ionizing radiation Xu et al. 2016, submitted (arxiv: )

23 Escape fraction of ionizing radiation Xu et al. 2016, submitted (arxiv: )

24 Escape fraction of ionizing radiation fstar fescaping photons Void: z=15.0 Void: z=10.0 Void: z=8.0 Normal: z=15.0 Normal: z=12.5 Rarepeak: z=18.5 Rarepeak: z= log 10 (M vir /M ) Fraction of halos w/active star formation log 10 (M vir /M ) Fraction of halos w/escaping photons Xu et al. 2016, submitted (arxiv: )

25 Connecting to the Milky Way Work in progress: O Shea, B. Smith, J. Wise, D. Collins, D. Silvia, C. Hummels

26 Main challenge: We don t know some critical things about the Milky Way - particularly mass and formation history!

27 Halo mass function evolution c/o B. Smith

28 Halo growth c/o B. Smith

29 Halo growth c/o B. Smith

30 Simulation goals Evolution of progenitors of MW-like galaxies (conn. to Renaissance Simulations) Growth of magnetic fields in galaxies over the age of the universe Baryon cycle in galaxies - the intergalactic and circumgalactic medium; baryon recycling Exploration of star formation and feedback algorithms Stay tuned!

31 Takeaways The transition between primordial and metal-enriched star formation is locally complex, and the outcome is strongly affected by the presence of dust. Star formation is inefficient (and sometimes suppressed entirely) in small, high-z galaxies - turnover in UV luminosity function predicted. Escape fraction of ionizing radiation at high z is (on average) ~ 0.05, but highly variable depending on recent star formation rate! We re working on making connections to the Milky Way and its neighbors in the Local Group - simulations are ongoing!

32 Questions?