“Nature and Descendants of Sub-mm and Lyman-break Galaxies in Lambda-CDM” Juan Esteban González Obergurgl, 13/12/09 Collaborators: Cedric Lacey, Carlton Baugh, Carlos Frenk, Andrew Benson.
Feb 24, 2016
“Nature and Descendants of Sub-mm and Lyman-break Galaxies in Lambda-CDM”
Juan Esteban González
Obergurgl, 13/12/09
Collaborators: Cedric Lacey, Carlton Baugh, Carlos Frenk, Andrew Benson.
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:• 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
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
Galaxy mergers & morphology
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)
Þ Increase the amount of UV radiation heating the dust.
Þ Higher yield of metals from II SNe=>more dust produced.
The cumulative number counts at 850 µm. Baugh et al. 2005
Durham Galform Model
Luminosity Function
Baugh et al. 2005
Late type galaxies
Gonzalez et al. 2009
Redshift Distribution
Swinbank et al. 2008
• The nature of:
–Sub-mm galaxies (SMGs).
– Lyman-break galaxies (LBGs).
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.
Galaxy mergers:-> can trigger burst of star formation
In the model, SMGs:- Sv (850um) > 5.0mJy,- Redshift z>1.
Red: SMGs
Galaxy merger tree
Following the SMGs evolutionCentral Galaxy
Flux Sν (850 µm)
Following the SMGs evolutionCentral Galaxy
Flux Sν (850 µm)
Following the SMGs evolutionCentral Galaxy
Flux Sν (850 µm)Stellar Mass
Examples of Galxy Merger Trees
M*(z=0) = 1011 h-1 M๏
B/T: Bulge to Total Stellar Mass
B/T=1, pure bulge galaxyB/T=0, pure disk galaxy
Examples of Galxy Merger Trees
M*(z=0) = 1.1 x 1012 h-1 M๏
B/T: Bulge to Total Stellar Mass
B/T=1, pure bulge galaxyB/T=0, pure disk galaxy
SMG Triggering, Minor or Major Mergers?
Following the SMGs evolutionCentral Galaxy
Flux Sν (850 µm)
Duration of Sub-mm phase
Distribution of the time that a galaxy is considered as a SMGSν(850µm) > 5.0 mJy, z > 1
The typical duration of the Sub-mm phase is ~ 0.1 h-1 Gyr
SMGs evolution
• Stellar mass?
Stellar mass evolution
Stellar mass
growths with time
First SMGs end up in more massive galaxies
SMGs descendants
• What are the properties of the descendants of SMGs?
• Find all the SMGs
SMGs descendants (B/T distribution)
B/T: Bulge to Total Stellar Mass
B/T=1, pure bulge galaxyB/T=0, pure disk galaxy
Mainly bulge dominated descendants. 70% have B/T>0.5
SMGs descendants (stellar mass distribution)
satellitescentral
M*= 2 x 1011 h-1 M๏ Mhalo = 6 x 1013 h-1 M๏
Evolution of the cosmic star formation rate
SMGs
The star formation produced in the z>1 SMG phase contribute only 0.06% of the total present-day stellar mass density.
Contribution of the SMG phase
• The nature of:
– Sub-mm galaxies (SMGs).–Lyman-break galaxies (LBGs).
Lyman-Break Galaxies (LBGs)
Star forming galaxies
Spectral break around 912 Å by absorption by neutral H.
Characteristic Luminosity L*UV at z=3.
Bright LBGs: LUV > L*UV
Faint LBGs: LUV > 0.1 L*UV
Examples of Galxy Merger Trees
Bright LBGs (LUV > L*UV)Faint LBGs (LUV > 0.1 L*UV)
redshift
B/T: Bulge to Total Stellar Mass
B/T=1, pure bulge galaxyB/T=0, pure disk galaxy
M*(z=0) = 6.6 x 1010 h-1 M๏ Normal (LUV < 0.1 L*UV)
Examples of Galxy Merger Trees
redshift
B/T: Bulge to Total Stellar Mass
B/T=1, pure bulge galaxyB/T=0, pure disk galaxy
M*(z=0) = 2.1 x 1011 h-1 M๏ Bright LBGs (LUV > L*UV)Faint LBGs (LUV > 0.1 L*UV)Normal (LUV < 0.1 L*UV)
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
Faint LBGs:LUV > 0.1L*UV
Stellar mass distribution, BRIGHT LBGs and their descendants
Faint LBGs at z=3 are more than a order of Magnitude more massive.
• Different question:– What is the fraction of the total galaxies at z=0
that are descendants of LBGs?
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.
0.5% of the Bright-LBGs at z=6 are SMGs
2% of the Bright-LBGs at z=3 are SMGs
Sub-mm flux (850µm). of LBGs, how many are predicted to be SMGs?
z = 6
z = 3
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.