Evolution of Stellar-to-Halo Mass Ratio at z=0-7
from Hubble Imaging & Early Subaru/HSC Data
(Harikane+16, ApJ 821, 123, HSC project 87)Yuichi&Harikane&(The&University&of&Tokyo),&&M.&Ouchi,&Y.&Ono,&S.&More,&S.&Saito,&Y.&Lin,&J.&Coupon,&K.&Shimasaku,&T.&Shibuya,&P.&Price,&L.&Lin,&B.&Hsieh,&M.&Ishigaki,&Y.&Komiyama,&J.&Silverman,&T.&Takata,&H.&Tamazawa,&and&J.&ToshikawaOutline• Stellar-to-halo mass ratio (SHMR)• HSC & Hubble Data and LBG Sample• Clustering Analysis• Results and Discussion

Galaxy Formation is Inefficient• All of baryons are not converted to stars.
– SN or AGN feedbacks? Inefficient gas cooling?
– How do we understand this?

Kormendy+13&

Galaxy-Dark Matter Halo Connection
• Galaxy formation processes are closely related
to dark matter halo mass (Mh).
• Stellar-to-halo mass ratio (SHMR=M*/Mh)

SHMR=M*/Mh– Fraction of mass converted to stars (Mh=~Mtotal)

Halo&mass&Mh
Leauthaud+12&

SHMR=M*/Mh at High Redshift• Related to evolution of cooling, feedback, merger…
• Theoretical predictions at high redshift– Monotonic increase from high-z to low-z at fixed Mh• Observation: poor due to limited data (Foucaud+10)(c.f., abundance matching)

Thompson+14&Somerville+15&
Okamoto+15&

This Study
Data:|Hubble comprehensive archival data (10 fields)|Subaru Hyper-Suprime Cam (HSC) early data

Method: Clustering Analysis

SHMR at high redshiftData & Sample Selection

Lyman break galaxy (LBG) selection @z~4, 5, 6, 7
UDF12 AEGISCOSMOS UDS Hubble (~600arcmin2)

N=614

N=510

N=455N=400

GN-DeepGN-WideGS-DeepGS-Wide
N=2534 N=1124 N=3082

N=734A2744P M0416P XMM GAMA09h
N=70

N=129

N=451

N=279

Subaru/HSC (~15deg2)

Total of 10,381 LBGs at z=4-7

How to Measure Galaxy’s Halo Mass
Num. of Galaxies RedshiftWeak LensingClusteringAbundance Matching(AM)

Assumptions

>~10000

0<z<2

>~1000

0<z<7 Structure formation,
HOD (later)

>~100

0<z<8

Weak&Lensing&-+ Duty cycle,
Satellite galaxy(subhalo)

Abundance&Matching&NASA/STScI&

Finkelstein+15&Galaxy Clustering• Structure formation in Lambda CDM universe– High mass halos are strongly clustered
Initial Fluctuation!Collapse(Extreme examples)
Galaxies in high mass halos In low mass halos&δcrit=1.69

Clustering Analysis w/ HOD Model
Angular correlation function
Galaxy power spectrum from(observed clustering strength) halo occupation distribution(HOD) model (function of Mh)HOD model
1 halo term
2 halo termDark Matter Halo Mass• Hubble: Mh~1011-1012 Msun.
• Subaru/HSC: Mh>1012 Msun.

●z~4●z~5○z~5 (HSC)●z~6●z~7

Stellar Mass Estimate M* from MUV using the tight correlation at high-z

Shibuya,&Ouchi&&&YH+15

SHMR

SHMR

• We estimate SHMR=M*/Mh at z~4-7●z~4●z~5○z~5 (HSC)
●z~6
●z~7

SHMR

SHMR

• We estimate SHMR=M*/Mh at z~4-7• SHMR evolution w/ redshift is found (>98% CL)●z~4
●z~5○z~5 (HSC)
●z~6
●z~7

SHMR

Comparison with AM• The difference is up to a factor of ~3 in Mh.
– AM is useful to estimate Mh of high-z galaxy, if one allows thesystematic uncertainties up to a factor of 3.

Evolution of SHMR• SHMR (Mh=1011 Msun)– Decrease from z~7 to 4, increase from z~4 to 0

DecreaseIncrease

Comparison with Theoretical Studies
SPH&simula^on
Semi_analy^c&model

Discrepancy

• z~4->0: models reproduce our obs results• z~7->4: models do not explain our obs resultsSummary
1. SHMR evolution:
decrease from z~7 to 4
increase from z~4 to 0(>98%CL for Mh~1011Msun)
2. Our clustering results agreewith the AM within a factorof 3 in Mh.
3. Theoretical models do not
reproduce the SHMR evolat z~4-7.