Download presentation
Presentation is loading. Please wait.
Published bySilas Ball Modified over 8 years ago
1
The cosmic evolution of star formation and metallicity over the last 13 billion years (an observational perspective) Andrea Cimatti (INAF - Osservatorio Astrofisico di Arcetri)
2
OUTLINE SFR indicators High-z star-forming galaxies “Fossil” galaxies Cosmic evolution of SF density Cosmic evolution of stellar mass “Downsizing” Metallicity indicators Metallicity of high-z galaxies Cosmic evolution of the mass-metallicity relation
3
The 1996+ revolution HST ESO VLTJCMT Keck
4
The “historical” Lilly – Madau plot Lilly et al. 1996 Madau et al. 1996
5
Star formation rate (SFR) main indicators L(recombination lines) (e.g. Hα) (primary) L(forbidden lines) (e.g. [OII]3727) (empirical, not universal) L(Lya) L(UV continuum) from OB stars (1500-2800 Å) L(FIR) (and L(MIR) ?) (10-1000μm) L(radio) (1.4 GHz) L(X) (2-10 keV) Caveat: AGN “contamination”, dust extinction, IMF assumption Specific star formation rate = SSFR = SFR/(stellar mass) [yr -1 ] Small SSFR most mass was already built-up in the past Large SSFR significant mass is still building Star formation
6
The star formation that we see: high-z galaxies which are forming stars
7
Optical selection based on broad-band colors Steidel et al. 2005 Magenta (“BM” selection): 1.5 < z < 2 Cyan (“BX” selection): 2 < z < 2.5 Yellow+Green (LBG selection): z ~ 3 BM BX LBG
8
Optically-selected star-forming galaxies at 1<z<4 (Shapley et al. 2003) = 10.3 ± 0.5 = 30 ± 20 Msun/yr 0 < E(B-V) < 0.3 N ~ 3x10 -3 Mpc -3 1/3 < Z/Zsun < 1 (Steidel et al. 2004, Reddy et al. 2005, Shapley et al. 2003, 2005, Erb et al. 2006) Selected in the optical with the so called BM/BX/LBG color criteria (Steidel et al. 1996, Adelberger et al. 2004)
9
Photometric candidates at 7 < z < 10 HUDF data. Bouwens et al. 2004, 2005 No secure genuine “primordial” (Pop III) objects identified to date
10
… K- to mm-selected dusty starbursts (1<z<5) E(B-V)>>0.3 ~ 11 SFR ~ 100-(1000) Msun/yr, Z ~ Zsun N ~ 10 -4 Mpc -3 (10 -5 for submm galaxies) Problem for galaxy formation models (dEROs, SMGs, DRGs, sfBZKs, HyEROs, IEROs…; Totani et al. 2001, Cimatti et al. 2002, Daddi et al. 2004, Chapman et al. 2005; Franx et al. 2003; Chen et al. 04) Spitzer IRAC-EROs Submm/mm galaxies K-selected starbursts Dusty EROs
11
High-z dusty AGN Dust thermal emission from a quasar at z=6.42 CO(3-2) emission from the same quasar (Bertoldi et al. 2003) (Walter et al. 2004) Many high-z quasars have high FIR luminosity (up to 1e13 Lsun), dust continuum emission consistent with mass of ~ several x 1e8 Msun and molecular gas with mass of the order of 1e10 Msun SFR > 1000 Msun/yr !?
12
Emission line galaxies Line emitting galaxies are generally found with narrow-band imaging or “slitless” spectroscopy (1 < z < 6.6) McCarthy et al. 1999, Hu et al. 2002, Glazebrook et al. 2004, Kurk et al. 2004, Malhotra et al., Rhoads et al., Taniguchi et al. 2005, Bunker et al., Doherty et al. 2006 Lya at z=6.56 (Hu et al. 2002) Kurk et al. 2004 Lya at z=6.54
13
OPTICAL SELECTION NEAR-IR SELECTION
14
The star formation that we do not see: “fossil” galaxies which had star formation
15
Old passive spheroids at z>1 E/S0 galaxies Passively evolving 1 < z < 2 1 – 4 Gyr old M(stellar) > 10 11 Msun Problem for galaxy formation models z(SF onset) > 2 – 3 Short-lived, powerful starbursts It is possible to derive SF history from spectra Cimatti et al. 2002, 2004, McCarthy et al. 2004, Daddi et al. 2005, Saracco et al. 2005
16
A massive galaxy candidate at z~6.5 Photometric candidate (no spectroscopic redshift) Consistent with a galaxy at z=6.5 with a large stellar Stellar mass of 6e11 Msun (!) z(form) > 9 Alternative: very dusty starburst at z=2.5 (Mobasher et al. 2005) See also Eyles et al. 2005, Yan et al. 2006
17
Other massive galaxy candidates at 5 < z < 8 z J H K 3.6 4.5 5.8 8.0 24 micron HST ACS: B+V+I+z K ≥ 25 (AB) STACKING (3”x3”) Rodighiero et al. 2006
18
The cosmic evolution
19
The Lilly-Madau plot 10 years ago
20
The Lilly – Madau plot now Hopkins et al. 2005, 2006 Hatched and green: 24μm Red star: radio Blue: optical/UV DLAs
21
Cosmic evolution from “archeology” of z~0 galaxies Heavens et al. 2004 SDSS data + MOPED
22
Dependence on luminosity and sample selection K-selected samples miss a significant fraction of SF galaxies with L<L* At all z, L>L* galaxies contribute only 1/3 to the SFR density L<L* galaxies are the dominant sites of star formation SFR density ~constant at 1<z<4, drops by 2x at z~4.5 (Gabasch et al. 2005)
23
“Downsizing” (Cowie et al. 1996)
24
Thomas et al. 2004 Constraints from σ, Hβ, Mgb,, stellar populations More massive spheroids form earlier and faster Formation time scales independent of environment ~1-2 Gyr younger in low density environments Mass assembly almost completed around z~1 (see also Cimatti, Daddi & Renzini 2006) Dependence on mass and environment Mass-dependent SFHs for z~0 galaxies (Heavens et al. 2004) Latest results confirm that massive galaxies which dominated cosmic SF at z~3 are in clusters today, whereas galaxies dominating SF at z~0 inhabit low density regions (Poggianti et al. 2006, Sheth et al. 2006) Early-type galaxies
25
The evolution of the stellar mass function Stellar mass function evolution per galaxy type (Bundy et al. 2006) Shaded areas = 1 σ confidence regions Increase of N(red) mirrored by decrease of N(blue) Fractional contributions of red and blue galaxy populations to the stellar mass function Largest sample analyzed to date: DEEP2 spectroscopy + optical-NIR SEDs >8000 galaxies over 1.5 square degrees (4 fields) M(tr)
26
Specific star formation Feulner et al. 2005 SSFR = SFR/M(stars) Higher in lower mass galaxies at all redshifts Oldest stars in largest mass galaxies Massive galaxies are in a quiescent state at z<2 (no significant change in stellar mass) Strong increase of at z>2-3 for most massive galaxies Downsizing of SF See also Juneau et al. 2005, Caputi et al. 2006
27
Metallicity
28
Metallicity indicators IONIZED GAS R 23 = ([OII]3727+[OIII]4959,5007) / Hβ (Pagel et al. 1979) N2 = [NII]6584 / Hα (Denicolò et al. 2002) O3N2 = ([OIII]5007/Hβ)/([NII]6584/Hα) (Pettini & Pagel 2004) R 23 + [OIII]5007/[OII]3727 (Nagao et al. 2006) [NeIII]3869/[OII]3727 (Nagao et al. 2006) CAVEAT: shock-ionized gas, AGN photoionization ISM and STARS Optical absorption features in E/S0 galaxies (e.g. Lick indices, Fe4383) Iron absorption lines at 2000-3000 Å (e.g. Savaglio et al. 2004) UV absorption features (e.g. 1370 Å, 1425 Å, 1978 Å, Rix et al. 2004) Metal absorption lines in DLAs (e.g. Pettini et al. )
29
Nagao et al. 2006 Emission line indicators
30
Stellar mass – ionized gas metallicity relation Tremonti et al. 2004 (SDSS)
31
Stellar vs. ionized gas metallicity Gallazzi et al. 2005 (SDSS)
32
Mass – metallicity relation at 0.4 < z < 1.0 A M-Z relation exists at ~0.7 and evolves with redshift At a given mass, a galaxy at z~0.7 has lower metallicity vs. z~0 Evolution more rapid at lower masses. Massive galaxies have Z(solar) at z~0.7 (bulk of SF completed) A more rapidly declining SF in more massive galaxies is consistent with the results (downsizing…) (see also Carollo & Lilly 2001, Lilly et al. 2003, Kobulnicky & Kewley 2004, Maier et al. 2004, 2006) Savaglio et al. 2005 (CFRS + GDDS samples)
33
Optically-selected star-forming galaxies at z~2 Shapley et al. 2004 Erb et al. 2006
34
Mass – metallicity relation at z~2 Erb et al. 2006 Optically-selected
35
Metal-rich starbursts at z>2 Submm galaxies (Tecza et al. 2004, Swinbank et al. 2005) Distant Red Galaxies (J-K>2.3) (van Dokkum et al. 2004) K-band bright optically-selected galaxies (BX) (Shapley et al. 2004) BzK-selected starbursts (De Mello et al. 2004) Very few observations Emission line ratios and UV absorptions suggest solar to super-solar metallicities
36
Metallicity at z>3 Metal abundance derived from R 23 1/10 < Z/Zsun < 1 (highly uncertain) For the only certain galaxy: 1/6 < Z/Zsun < 1/2 Pettini et al. 2001
37
A cautionary tale… [OII], Hβ, [OIII], Hα, [NII] Line ratios imply AGN and/or shock ionization (winds) H-band spectrum only low metallicity K-band spectrum only high-metallicity (van Dokkum et al. 2005) z ~ 2.5 K-selected
38
The problem of “missing metals” For a given IMF and a mean stellar yield (e.g. =2.4%, Madau et al. 1996), the total amount of metals formed by a given time t is: ρ(Z,t) = ∫ dρ(stars,t)/dt Only a fraction of the expected metals is actually seen in galaxies ! At z~2 : 5% DLAs 5% Submm galaxies 5% Distant Red Galaxies 15% Optically-selected star-forming galaxies ~30% (50-60% if corrected for incompleteness) (Bouché et al. 2006a, 2006b) At z~3 the problem is even more serious : 5-10% Lyman-break galaxies The rest could be in hot phase with T~10 6 K (e.g. Ferrara, Scannapieco & Bergeron 2005)
39
Multi-wavelength surveys are needed to unveil diverse populations of high-z star-forming galaxies (but no Pop III objects detected yet) The cosmic SFR density increases rapidly to z~1-2, but evolution unclear at z > 2 The old, massive, passive E/S0 galaxies already present at 1 2-3 and short-lived powerful starbursts Dusty, massive, high-metallicity starbursts at z~2-3: E/S0 progenitors ? Mass is more important than environment in driving galaxy evolution “Downsizing”: massive galaxies form stars earlier and faster A mass-metallicity relation exists up to z ~ 2 (“downsizing” evolution) Only a fraction of the expected metals is seen in galaxies New generation of hierarchical merging models start to agree better with obs The global picture
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.