On the Star Formation Histories of Massive Galaxies Casey Papovich (Texas A&M University) Massive Galaxies through Cosmic Time 3, Tucson, AZ credit: Volker Springel Tuesday, November 9, 2010
On the Star Formation Histories of Massive Galaxies
Casey Papovich (Texas A&M University)Massive Galaxies through Cosmic Time 3, Tucson, AZ
credit: Volker Springel
Tuesday, November 9, 2010
• How and when do galaxies acquire their gas ?
• How is it converted to stars ?
-What are the Star Formation Histories of Galaxies ?
-What is the duty cycle of high-z star-forming galaxies ?
-When do galaxies assemble their stars? (Where do the stars form?)
Some Questions in the Formation of Massive Galaxies
Tuesday, November 9, 2010
What are the Star Formation Histories of Galaxies ?
Finlator, Davé, & Oppenheimer (2010, arXiv:1005.4066)
Tuesday, November 9, 2010
What are the Star Formation Histories of Galaxies ?
Finlator, Davé, & Oppenheimer (2010, arXiv:1005.4066)
SFR ∼ M*
high duty cycle
> 0d(SFR)
dt
Tuesday, November 9, 2010
What are the Star Formation Histories of Galaxies ?
K.-S. Lee, Dey, Reddy et al. (arXiv:1009.3022)
See also, Renzini (2009), Maraston et al. (2010), Lee et al. (2010).
Magn
itude
(AB)
Wavelength [micron]1 2 4 7 100.5
21
22
23
24
25
26
27
28
Stacked SEDs of z=3.7 galaxies.
Tuesday, November 9, 2010
Star-Formation and Mass Growth in High-z Galaxies
Finkelstein, Papovich, Giavalisco, Reddy, Ferguson, Dickinson(2010, ApJ, 719, 1250)
Tuesday, November 9, 2010
Do high redshift galaxies have Star Formation Histories that Rise with Time ?
Tuesday, November 9, 2010
Empirical Constraints on Star-Formation Histories and Mass Growth in High-z Galaxies
•Trace mass growth by comparing massive high-z galaxies at constant number density:
- track descendants and progenitors in galaxies in a relatively robust way (van Dokkum et al. 2010; similar to abundance matching Conroy & Weschler 2009)
- SFRs of galaxies with n=2 x 10-4 Mpc-3 increase from z=8 to z=3.
- galaxies with this number density have M=1.5 x 1011 M⊙ at z=0,
- star formation history of these galaxies matches stellar mass growth.
Tuesday, November 9, 2010
z=7.3 z=5.7 z=4.9
z=4.2 z=3.6 z=3.0
1 2 3 1 2 3 1 2 3Log (Mass / 1010 M⊙)
n(>
M)
[10-4
Mpc
-3]
3
2
1
0
3
2
1
0
Mass Functions and Halo Merger Trees from Millennium (Springel+05)
Track the Progenitors and Descendants of High-z Galaxies by Comparing at Constant Number Density
Tuesday, November 9, 2010
z=7.3 z=5.7 z=4.9
descendants of z=7.5 galaxies
z=4.2 z=3.6 z=3.0
1 2 3 1 2 3 1 2 3Log (Mass / 1010 M⊙)
n(>
M)
[10-4
Mpc
-3]
3
2
1
0
3
2
1
0
Mass Functions and Halo Merger Trees from Millennium (Springel+05)
Track the Progenitors and Descendants of High-z Galaxies by Comparing at Constant Number Density
Tuesday, November 9, 2010
Completeness = Fraction of selected galaxies with a progenitor selected at z=7.5 (descendant selected at z=3.0).
Similar results from simulations of the effects of mergers on mass functions (van Dokkum et al. 2010).
Progenitors of z=3 Galaxies
Descendants of z=7.5 Galaxies
Track the Progenitors and Descendants of High-z Galaxies by Comparing at Constant Number Density
Papovich, Finkelstein, Ferguson, Lotz, Giavalisco (2010, arXiv:1007.4554)
Tuesday, November 9, 2010
Integrated UV Luminosity Functions (Reddy & Steidel 2008; Bouwens et al. 2007, 2010).
Galaxy Populations selected at constant luminosity (or mass) correspond to very different number densities at different redshifts.
n=2x10-4 Mpc-3
Track the Progenitors and Descendants of High-z Galaxies by Comparing at Constant Number Density
Tuesday, November 9, 2010
Star Formation Histories of High-z Galaxies
SFH of galaxies with n(>LUV) = 2 x 10-4 Mpc-3
Dust
Corre
cted S
FR
Papovich, Finkelstein, Ferguson, Lotz, Giavalisco (2010, arXiv:1007.4554)
Daddi et al. 2005
Tuesday, November 9, 2010
Star Formation Histories of High-z GalaxiesStar Formation History of simulated galaxies show Rising SFRs
(Finlator, Davé, Papovich & Hernquist 2006, ApJ, 639, 672)
SFR ~ tα
Tuesday, November 9, 2010
Stellar Mass Growth of High-z Galaxies
Mass Growth of Galaxies
Masses of galaxies withn(>LUV) = 2 x 10-4 Mpc-3 (Shapley et al. 2005; Gonzalez et al. 2010;
Finkelstein et al. 2010)
Papovich, Finkelstein, Ferguson, Lotz,
Giavalisco (2010, arXiv:1007.4554)
Tuesday, November 9, 2010
Stellar Mass Growth of High-z Galaxies
Mass Growth of Galaxies
Papovich, Finkelstein, Ferguson, Lotz,
Giavalisco (2010, arXiv:1007.4554)
Tuesday, November 9, 2010
Stellar Mass Growth of High-z Galaxies
Masses of galaxies withn(>M) = 2 x 10-4 Mpc-3
from stellar-mass functions(Marchesini et al. 2009)
Mass Growth of Galaxies
Papovich, Finkelstein, Ferguson, Lotz,
Giavalisco (2010, arXiv:1007.4554)
Tuesday, November 9, 2010
Empirical Constraints on Star-Formation Histories and Mass Growth in High-z Galaxies
•Trace mass growth by comparing galaxies at constant number density:
- Massive galaxies have empirical star-formation histories that increase from z=8 to z=3.
- Basic agreement between empirical and theoretical SFHs.
- Star formation History of these galaxies matches stellar mass growth:
‣ if near unity “Duty cycle” of Star-formation,
‣ then high-mass end of IMF approximately Salpeter/Chabrier-like.
• Prediction: Star-formation and Mass growth predict Gas masses must Increase and that the Gas Accretion Rate tracks SFR.
Tuesday, November 9, 2010
What are the Star Formation Histories of Massive Galaxies?
Redshift
SFR
I. Period from 3 < z < 8 characterized by increasing SFRs.
II. Period from z < 3 with exponentially decreasing SFRs.
III
Tuesday, November 9, 2010
Assembly Histories of Massive Galaxies
Oser, Ostriker, Naab, Johansson, & Burkert (arXiv:1010.1381)
See also talks by Ostriker and Naab tomorrow.
Log R / Rvir
-4 -3 -2 -1 0 1 2Ag
e [Gy
r]
02
0
0.3
0.6
11.5248
468
1012
RedshiftM
/ M
tot material
formed in situ
material accreted outside Rvir
total
in situ
accreted
Tuesday, November 9, 2010
Growth of Massive Galaxies at z < 2
z=2.0z=1.6z=1.1z=0.6
van Dokkum et al. (2010)
redshift0 0.5 1 1.5 2
10.6
10.8
11
11.2
11.4
Log
(M/M
⊙)
total mass
mass > 5 kpc
mass < 5 kpc
Tuesday, November 9, 2010
Summary: On the Star Formation Histories of Massive Galaxies
• Some convergence between Theory and Observations on Star Formation Histories.
‣ empirically, period at high redshifts 3 < z < 8 where SFRs increase with time.
‣ prediction that gas accretion rate also increases with time.
‣ period of declining SFRs at z <~ 3 in accord with observations of galaxy colors and stellar population ages.
‣ period at z < 3 possibly marked by rapid accretion of stars formed at large virial radii. Perhaps testable from metallicity gradients in early-type galaxies ?
Open questions:
-How and when do galaxies acquire their gas ?
-How well do we know the Duty Cycle of high-z star-forming galaxies ?
-What causes galaxies to stop forming stars ?
Tuesday, November 9, 2010