1. A Population of Old and Massive Galaxies at z > 5
T. Wiklind ESA/STScI
B. Mobasher ESA/STScI, M. Dickinson NOAO,
H. Ferguson STScI, M. Giavalisco STScI, N. Grogin JHU,
N. Panagia STScI
December 8, 2018
Galaxies and Structure Through Cosmic Times

2. Galaxies and Structure Through Cosmic Times
Evidence for evolved (age > 1 Gyr) and massive (M* > 1011 Mo) at z ~ 2 – 3
(many talks this meeting; posters: Kriek et al.)
There are also evidence for galaxies of similar characteristics at z ~ 3 – 5
(this meeting; posters: Eyles et al.)
Members of the high-z galactic zoo
Lyman Break Galaxies (LBG) (z ~ 3-6)
Lyman-a emitters (LAE) (z ~ 4-6)
Submillimeter detected galaxies (SMG) (z ~ 2-3)
High-z AGNs (z ~ 6)
Old and massive galaxies (DRG) (z ~ 2-3)
Old and massive galaxies at z > 5
December 8, 2018
Galaxies and Structure Through Cosmic Times

3. Galaxies and Structure Through Cosmic Times
JD2
December 8, 2018
Galaxies and Structure Through Cosmic Times

4. Galaxies and Structure Through Cosmic Times
JD2 (J-dropout) in HUDF
(see talk by Bahram Mobasher)
z = 6.5
age ~ Gyr
EB-V = 0.0
M* = Mo
Z ~ 0.2 Zo
December 8, 2018
Galaxies and Structure Through Cosmic Times

5. Galaxies and Structure Through Cosmic Times
The Balmer break is a prominent feature for stellar populations age t > 100 Myrs
z = 7
no extinction
t = 50 Myr
t = 100 Myr
t = 300 Myr
t = 500 Myr
t = 600 Myr
t = 800 Myr
December 8, 2018
Galaxies and Structure Through Cosmic Times

6. Galaxies and Structure Through Cosmic Times
z = 5
z = 8
z = 5
z = 8
z = 2
z = 4
December 8, 2018
Galaxies and Structure Through Cosmic Times

7. There is no ‘clean’ way of color selecting old z > 5 galaxies
Use a two-step process:
Color selection:
The main index is the Ks–3.6mm color
Use J–K and H–3.6mm as secondary color
This will result in a relatively large fraction of interlopers
Population synthesis models (Bruzual & Charlot 2003):
Redshift range z =
Age range = 5 Myr Gyr
Calzetti extinction law EB-V =
IGM absorption
Metallicities Z = 0.2, , 2.5 Zo
Salpeter IMF: 0.1 – 100 Mo
Star formation history: exponentially declining SFR
t = Gyr
December 8, 2018
Galaxies and Structure Through Cosmic Times

8. Galaxies and Structure Through Cosmic Times
K-selected sample from GOODS-S
HST/ACS (BViz); VLT/ISAAC (JHKs); SST/IRAC (3.6, 4.5, 5.8, 8mm)
5754 sources: 75 / 62 selected; 12/12 z > 5 (total 18)
December 8, 2018
Galaxies and Structure Through Cosmic Times

9. Galaxies and Structure Through Cosmic Times
December 8, 2018
Galaxies and Structure Through Cosmic Times

10. Galaxies and Structure Through Cosmic Times
December 8, 2018
Galaxies and Structure Through Cosmic Times

11. Galaxies and Structure Through Cosmic Times
z = 5.1
EB-V = 0.0
age = 0.8 Gyr
t = 0
Z = 0.4 Zo
zform = 12
M* = Mo
Best-fit parameters
December 8, 2018
Galaxies and Structure Through Cosmic Times

12. Galaxies and Structure Through Cosmic Times
z = 6.1
EB-V = 0.025
age = 0.2 Gyr
t = 0
Z = 0.2 Zo
zform = 7
M* = Mo
Best-fit parameters
December 8, 2018
Galaxies and Structure Through Cosmic Times

13. Galaxies and Structure Through Cosmic Times
Not everything which is a J-band dropout is at z > 5
2102 Images of an elliptical galaxy
December 8, 2018
Galaxies and Structure Through Cosmic Times

14. Galaxies and Structure Through Cosmic Times
z = 2.6, EB-V = 0.2, age = 1.8 Gyr, t = 0.1, Z = Zo
December 8, 2018
Galaxies and Structure Through Cosmic Times

15. Galaxies and Structure Through Cosmic Times
December 8, 2018
Galaxies and Structure Through Cosmic Times

16. Galaxies and Structure Through Cosmic Times
BBGs are very difficult to observe spectroscopically
No on-going star formation
no strong line emission
Faint continuum
absorption lines not possible
We can test the method by
applying it to objects with
known redshift
December 8, 2018
Galaxies and Structure Through Cosmic Times

17. Galaxies and Structure Through Cosmic Times
A total of 19 BBGs at z > 5 (including JD2)
Typical values:
Stellar masses ~ Mo
Ages 0.2 – 1.0 Gyr
Modest or no extinction
No on-going star formation
Formation redshift 9 – >25
Less than half detected with MIPS at 24mm
Small systems (diameter ~ 4 kpc)
Not detected in X-rays / radio continuum
Number density 3– Mpc-3
December 8, 2018
Galaxies and Structure Through Cosmic Times

18. Galaxies and Structure Through Cosmic Times
A total of 19 BBGs at z > 5 (including JD2)
Typical values:
Stellar masses ~ Mo
Ages 0.2 – 1.0 Gyr
Modest or no extinction
No on-going star formation
Formation redshift 9 – >25
Less than half detected with MIPS at 24mm
Small systems (diameter ~ 4 kpc)
Not detected in X-rays / radio continuum
Number density 3– Mpc-3
Thermally Pulsing AGB stars. Luminosity and time-scale
at near-IR wavelengths? (Maraston this meeting)
December 8, 2018
Galaxies and Structure Through Cosmic Times

19. Galaxies and Structure Through Cosmic Times
zspec = 5.83
zphot = 5.7
age = 1.0 Gyr
log(M*) = 10.34
EB-V = 0.0
Z = 0.2 Zo
zspec = 5.05
zphot = 4.8
age = 0.01 Gyr
log(M*) = 8.53
EB-V = 0.0
Z = 0.2 Zo
Models BC03.
Data from Yan et al. 2005
December 8, 2018
Galaxies and Structure Through Cosmic Times

20. Galaxies and Structure Through Cosmic Times
zspec = 5.90
zphot = 5.8
age = 1.0 Gyr
log(M*) = 10.49
EB-V = 0.0
Z = 1.0 Zo
zspec = 4.65
zphot = 4.5
age = 0.4 Gyr
log(M*) = 10.10
EB-V = 0.0
Z = 0.2 Zo
Models BC03.
Data from Yan et al. 2005
December 8, 2018
Galaxies and Structure Through Cosmic Times

21. Galaxies and Structure Through Cosmic Times
zspec = 4.78
zphot = 4.5
age = 0.7 Gyr
log(M*) = 9.81
EB-V = 0.0
Z = 0.2 Zo
zspec = 5.49
zphot = 4.8
age = Gyr
log(M*) = 9.56
EB-V = 0.10
Z = 0.2 Zo
Models BC03.
Data from Yan et al. 2005
December 8, 2018
Galaxies and Structure Through Cosmic Times

22. Galaxies and Structure Through Cosmic Times
z=0 galaxies
M*> MO
M*> MO
LBGs
K20
EROs
BBGs
sub-mm
SDSS
QSOs
Somerville 2004
December 8, 2018
Galaxies and Structure Through Cosmic Times