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“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

“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
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.
galform model
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

slide4

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
slide5

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

slide6

Luminosity Function

Redshift Distribution

Swinbank et al. 2008

Late type galaxies

Baugh et al. 2005

Gonzalez et al. 2009

slide7

The nature of:

    • Sub-mm galaxies (SMGs).
    • Lyman-break galaxies (LBGs).
submillimetre galaxies smgs
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.
slide9

Galaxy merger tree

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

Red: SMGs

following the smgs evolution
Following the SMGs evolution

Central Galaxy

Flux Sν (850 µm)

following the smgs evolution1
Following the SMGs evolution

Central Galaxy

Flux Sν (850 µm)

following the smgs evolution2
Following the SMGs evolution

Central Galaxy

Stellar Mass

Flux Sν (850 µm)

slide13

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๏

slide14

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๏

following the smgs evolution3
Following the SMGs evolution

Central Galaxy

Flux Sν (850 µm)

duration of sub mm phase
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

smgs evolution
SMGs evolution
  • Stellar mass?
stellar mass evolution
Stellar mass evolution

First SMGs end up in more massive galaxies

Stellar mass growths with time

smgs descendants
SMGs descendants
  • What are the properties of the descendants of SMGs?
  • Find all the SMGs
smgs descendants b t distribution
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

smgs descendants stellar mass distribution
SMGs descendants (stellar mass distribution)

M*= 2 x 1011 h-1 M๏

Mhalo = 6 x 1013 h-1 M๏

satellites

central

slide23

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.

slide24

The nature of:

    • Sub-mm galaxies (SMGs).
    • Lyman-break galaxies (LBGs).
lyman break galaxies lbgs
Lyman-Break Galaxies (LBGs)

Star forming galaxies

Spectral break around 912 Å by absorption by neutral H.

slide26

Characteristic Luminosity L*UV at z=3.

Bright LBGs: LUV > L*UV

Faint LBGs:

LUV > 0.1 L*UV

slide27

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)

slide28

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)

slide29

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

slide30

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.

slide31

Different question:

    • What is the fraction of the total galaxies at z=0 that are descendants of LBGs?
slide32

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.

slide33

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

conclusions
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.