
Gas Inflow and Cosmic Star Formation
Efficiency in Galaxies at z>3
Fuyan Bian
Stromlo Fellow
Research School of Astronomy and Astrophysics,
Australian National University
Collaborators: Xiaohui Fan, Linhua Jiang, Ian McGreer, Dan Stark, Arjun Dey, Richard Green,
Roberto Maiolino, Fabian Walter, Romeel Dave, Kyoung-Soo Lee , Yen-Ting Lin
2015 Gas Accretion on Galaxies@NRAO
Galaxy Formation Efficiency
~3% at 1012 M⊙ halo
mass.
 Much less than the global
baryon fraction ~ 17%.
 Conversion of baryons to
stars has maximum
efficiency ~10-30% and is
much smaller at higher
and lower halo mass.
Stellar Mass/Halo Mass
 M*/Mhalo maximizes at
Halo Mass
Behroozi+2012
See also Kravstov talk
Star-Forming Band in Dark Matter Halo
 Halo and stellar growths
AGN feedback and mass quenching
are associated with each
other in the star-forming
band
 Mcrit, Mthresh, and galaxy
UV background and SN feedback
from Joel Primack
formation efficiency(halos
mass, galaxy property)
are critical parameters for
the galaxy formation
models
Questions to Explore
 How does the stellar mass grows with dark mater halo?
Or how do the gas accretion process and feedback
regulates and the star formation in high-redshift galaxies?
 What is the galaxy formation efficiency (the efficiency
converting baryon into stars) in high-redshift galaxies
and how does it change with the redshift, galaxy
luminosity, and halo mass?
Galaxy Formation Efficiency at High-z
 Galaxy formation efficiency = SFR/Gas accretion rate
 SFR: from SFR indicators (dust-corrected UV
luminosities)
 Gas accretion rate = Ωb/Ωd × dark matter accretion rate
 Dark matter accretion rate: a function of redshift (z) and
halo mass (Mhalo) (e.g. EPS theory, Neistein 2008).
 Request a sample of high-z galaxies with known SFRs,
redshifts, and halo masses.
Break Galaxies
AnLyman
L* Star-forming
Galaxy

Luminous Z~3 Lyman Break
at z=2-3: Galaxies
Lyman
limits
at z=0:
U-G
in
M*~a few x 1010 M⊙
M*~a few x 1010 M⊙
the
Deep
and Wide
Field
Surveys
Extended,
thin, smooth
disk
Compact,
thick, clumpy disk
SFR~a few M⊙/yr
SFR~ a few ten M⊙/yr
Quiescent star formation
Intensive star formation
Molecular Gas fraction <Fuyan
0.1
Molecular Gas fraction ~ 0.5
Bian
Research School of Astronomy andG-R
Astrophysics,
Australian National University
8kpc
Collaborators: Xiaohui Fan (Arizona), Linhua Jiang (KIAA), Ian McGreer
Wavelength
(Arizona), Dan Stark (Arizona), Arjun Dey (NOAO), Richard Green (LBTO),
Lisa
Kewley
(ANU)rate
Roberto
Maiolino (Cambridge), Fabian Walter (MPIA),
Contamination
is
low
• Select
high-z star-forming
galaxies
Romeel
Daveobscured
(Steward),galaxies
Kyoung-Soo Lee (Purdue), Yen-Ting Lin (ASIAA)
effectively.
No highly
No quiescentredshift
galaxies
• Well-understood
distribution
based-on broad-band photometry.
Redshift
Genzel+2012
Steidel+2004
2015 Tsinghua
Seminar
NOAO Deep and Wide Field Survey
 NOAO Deep Wide-Field
Survey (Jannuzi & Dey 1999) is
a deep multicolor survey which
covers two 9 deg2 areas:
Bootes Field and Centus field.
 The Bootes field is also
covered by the new U- and Yband data with the LBT/LBC
(Bian+2013).
 Multi-wavelength coverage in
the Bootes field from X-ray to
radio.
Lyman Break Galaxies (LBGs) in Bootes Field
U Bw R
With the large survey
volume, 15,000 bright
LBGs at z~3 are selected
in the Bootes field.
Clustering of z~3 Luminous LBGs
Redshift Distribution
ω(θ)
Angular Correlation Function
θ (arcsec)

2D angular correlation function + Redshift distribution

=>Clustering (3D distribution) of two subsample of LBGs (L*1.5L* and 1.5L*-2.5L*) with r0=5.14h-1Mpc and r0=5.77h-1Mpc
ω(θ)
Dark Matter Halo Mass of Luminous LBGs
θ (arcsec)

Galaxy distributions trace underlying
dark matter distributions

Dark matter halo power spectrum
+ halo occupation distribution
function to fit the galaxy clustering.

The average hosting dark matter
halo masses are:
3x1012M⊙ for 1.5L* LBGs,
5x1012M⊙ for 2.5L* LBGs
Dark Mater Halo Mass of Faint LBGs
 LBGs at z~4 0.2-0.4 L* in GOODS field (Lee+06):
Halo mass 4-8x1011M⊙
 LBGs at z~5 0.4-1.0L* in GOODS field (Lee+06):
Halo mass 2-4x1011M⊙
 LBG at z~4 0.2-1L* in Subaru/XMM-Newton field (Ouchi+05):
Halo mass 4x1011-2x1012M⊙
 The existing LBG samples allow us to probe the halo mass
from 2x1011 to 5x1012M⊙
Baryonic Gas Accretion on Galaxies
The baryonic gas accretion rate
depends on redshift and halo mass
(Dekel+2009)
.
Lilly+2013
Galaxy formation efficiency in LBGs

A tight relation between redshiftscaled SFR and halo mass in LBGs.

The SF process in high-z LBG is
feed by the gas accretion process.

The galaxy formation efficiency is
5%-20%.

This efficiency does not change
significantly with redshift, galaxy
luminosity, halo mass (2x10115x1012 M⊙)
Bian+2013
Conclusion
 A tight relation between the redshift-scaled SFR and hosting
halo mass in LBGs at z>3, which follows the slope predicted
by the baryonic flow accretion.
 This relation suggests that the star formation process is
regulated by the gas accretion process in high-z galaxies
 The galaxy formation efficiency is 5%-20%, and does not
change with redshift, galaxy luminosity and halo mass.