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“Nature and Descendants of Sub-mm and Lyman-break Galaxies in Lambda-CDM ”

“Nature and Descendants of Sub-mm and Lyman-break Galaxies in Lambda-CDM ”. Juan Esteban González. Collaborators: Cedric Lacey , Carlton Baugh, Carlos Frenk , Andrew Benson. Obergurgl , 13/12/09. OUTLINE. Semi-analytical modelling: Durham Galform model Physical processes,

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“Nature and Descendants of Sub-mm and Lyman-break Galaxies in Lambda-CDM ”

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  1. “Nature and Descendants of Sub-mm and Lyman-break Galaxies in Lambda-CDM” Juan Esteban González Collaborators: Cedric Lacey, Carlton Baugh, Carlos Frenk, Andrew Benson. Obergurgl, 13/12/09

  2. OUTLINE • Semi-analytical modelling: • Durham Galform model • Physical processes, • Building Galaxy Merger Trees. • High-redshift populations: • Sub-mm galaxies (SMGs), • Lyman-break galaxies (LBGs), faint and bright criteria.

  3. Galform Model: • Processes included in the model: • gas cooling, • star formation, supernova feedback, • galaxy mergers, • chemical enrichment, • stellar population evolution, • dust extinction and emission. Cole, Lacey, Baugh & Frenk, 2000, MNRAS, 319, 168

  4. Galaxy mergers & morphology • The model distinguish two type of mergers: • major mergers: stellar disks -> stellar bulge • minor mergers: the disk of the central galaxy is preserved • In all major mergers and in some minor mergers: • -> burst of star formation • bulge can grow new disks

  5. Durham GalformModel • Parameters are the same used in Baugh et al. 2005: • - Reproduce the z=3 LF of LBGs • - Reproduce the number of SMGs. • Top-heavy IMF in burst: • in disks: • standard IMF (Kennicut) • Increase the amount of UV radiation heating the dust. • Higher yield of metals from II SNe=>more dust produced. The cumulative number counts at 850 µm. Baugh et al. 2005

  6. Luminosity Function Redshift Distribution Swinbank et al. 2008 Late type galaxies Baugh et al. 2005 Gonzalez et al. 2009

  7. The nature of: • Sub-mm galaxies (SMGs). • Lyman-break galaxies (LBGs).

  8. Submillimetre galaxies (SMGs) • Star-forming galaxies at high z (z ~2-3) • SMGs discovered using SCUBA instrument on the JCMT telescope (850 µm). • Submm: • Galaxies with starburst surrounded by dust, the dust is being heated by UV radiation from young stars, • the UV stellar emission is reradiated by the dust in far-infrared/submm bands, • Observationally selected having fluxes Sν (850µm) > 5.0 mJy.

  9. Galaxy merger tree • Galaxy mergers: • -> can trigger burst of star formation • In the model, SMGs: • Sv (850um) > 5.0mJy, • Redshift z>1. Red: SMGs

  10. Following the SMGs evolution Central Galaxy Flux Sν (850 µm)

  11. Following the SMGs evolution Central Galaxy Flux Sν (850 µm)

  12. Following the SMGs evolution Central Galaxy Stellar Mass Flux Sν (850 µm)

  13. B/T: Bulge to Total Stellar Mass Examples of Galxy Merger Trees B/T=1, pure bulge galaxy B/T=0, pure disk galaxy M*(z=0) = 1011 h-1 M๏

  14. B/T: Bulge to Total Stellar Mass Examples of Galxy Merger Trees B/T=1, pure bulge galaxy B/T=0, pure disk galaxy M*(z=0) = 1.1 x 1012 h-1 M๏

  15. SMG Triggering, Minor or Major Mergers?

  16. Following the SMGs evolution Central Galaxy Flux Sν (850 µm)

  17. Duration of Sub-mm phase Distribution of the time that a galaxy is considered as a SMG Sν(850µm) > 5.0 mJy, z > 1 The typical duration of the Sub-mm phase is ~ 0.1 h-1Gyr

  18. SMGs evolution • Stellar mass?

  19. Stellar mass evolution First SMGs end up in more massive galaxies Stellar mass growths with time

  20. SMGs descendants • What are the properties of the descendants of SMGs? • Find all the SMGs

  21. SMGs descendants (B/T distribution) B/T: Bulge to Total Stellar Mass B/T=1, pure bulge galaxy B/T=0, pure disk galaxy Mainly bulge dominated descendants. 70% have B/T>0.5

  22. SMGs descendants (stellar mass distribution) M*= 2 x 1011 h-1 M๏ Mhalo = 6 x 1013 h-1 M๏ satellites central

  23. Contribution of the SMG phase Evolution of the cosmic star formation rate SMGs The star formation produced in the z>1 SMG phase contribute only0.06% of the total present-day stellar mass density.

  24. The nature of: • Sub-mm galaxies (SMGs). • Lyman-break galaxies (LBGs).

  25. Lyman-Break Galaxies (LBGs) Star forming galaxies Spectral break around 912 Å by absorption by neutral H.

  26. Characteristic Luminosity L*UV at z=3. Bright LBGs: LUV > L*UV Faint LBGs: LUV > 0.1 L*UV

  27. B/T: Bulge to Total Stellar Mass Examples of Galxy Merger Trees B/T=1, pure bulge galaxy B/T=0, pure disk galaxy redshift Bright LBGs (LUV > L*UV) M*(z=0) = 6.6 x 1010 h-1 M๏ Faint LBGs (LUV > 0.1 L*UV) Normal (LUV < 0.1 L*UV)

  28. B/T: Bulge to Total Stellar Mass Examples of Galxy Merger Trees B/T=1, pure bulge galaxy B/T=0, pure disk galaxy redshift Bright LBGs (LUV > L*UV) M*(z=0) = 2.1 x 1011 h-1 M๏ Faint LBGs (LUV > 0.1 L*UV) Normal (LUV < 0.1 L*UV)

  29. Stellar mass distribution, BRIGHT LBGs and their descendants Bright LBGs: LUV > L*UV Bright LBGs at z=3 are five times more massive than LBGs at z=6

  30. Stellar mass distribution, BRIGHT LBGs and their descendants Faint LBGs:LUV > 0.1L*UV Faint LBGs at z=3 are more than a order of Magnitude more massive.

  31. Different question: • What is the fraction of the total galaxies at z=0 that are descendants of LBGs?

  32. Fraction of the total galaxies at z=0 with LBG progenitors BRIGHT LBGs FAINT LBGs z = 3 z = 6 A Milky Way mass galaxy is predicted to have a 50% of prob. of having a faint LBG progenitor. & to have a 6% (at z=3) and a 2% (at z=6) of probability of having a bright LBG progenitor.

  33. Sub-mm flux (850µm). of LBGs, how many are predicted to be SMGs? z = 6 0.5% of the Bright-LBGs at z=6 are SMGs z = 3 2% of the Bright-LBGs at z=3 are SMGs

  34. Conclusions • The model make predictions in a unified way, • For SMGs brighter than 5.0 mJy we find the following: • Duration of the sub-mm phase is typically 0.1/h Gyr, • Median stellar mass of their descendants is 2 x 1011h-1M⊙, • 70% of the SMGs end up as bulge-dominated galaxies, • however, the stellar mass produced in the sub-mm phase in these bright SMGs is only a tiny fraction (0.06%) of the total present day stellar mass density. • For LBGs: • Median stellar mass of the descendants is 4 x 1010h-1M⊙ (of bright z=3 LBGs) and 1011h-1M⊙ (of bright z=6 LBGs), • Median stellar mass of the descendants is 8 x 109h-1M⊙ (of both faint z=3 LBGs and faint z=6 LBGs), • One every 10 and one every 50 Milky Way mass galaxy is predicted to be descendants of z=3 and z=6 LBGs. • 2% and 0.5% of the LBGs at z=6 and z=3 are found to be SMGs.

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