Evolu&on(with(redshi1(of(the(star( formaon(in((galaxies ... · Evolu&on(with(redshi1(of(the(star( formaon(in((galaxies ... ... 2

Evolution with redshift

Evolu&on with redshi1 of the star forma&on in galaxies

detec&on and analysis Véronique Buat

Bologna PhD school-‐May 2014

Outline of the lecture

•  Mul&wavelength observa&ons of distant galaxies (including IR)

•  The global evolu&on of the star forma&on and dust aKenua&on with redshi1

•  Spectral energy distribu&ons •  Fundamental rela&ons between SFR, Mgas & Mstar


Outline

•  Mul$wavelength observa$ons of distant galaxies (including IR)

IR observa&ons & K-‐correc&ons, cross-‐matches and stacking techniques,

•  The global evolu&on of the star forma&on and dust aKenua&on with redshi1: analysis of the luminosity func&ons



The emission of dust: mid and far-‐IR

PAH 0.4-‐1.2 nms VSG 1-‐15 nms BG 15-‐100 nms

AKARI/IRC AKARI/FIS

Spitzer/IRAC Spitzer/MIPS

Herschel/PACS SPIRE


Polycyclic Aroma&c Hydrocarbons: PAHs


Adding mm facili$es

The drama&c advantage of sub-‐mm observa&ons: the posi$ve K-‐correc$ons


For a modified BB: Lν ~ {ν(em)}2+ß and DL ~ (1+z)2

Sν(obs) = Sν(em)* ν(em)/ν(obs) Sν(obs) =Sν(em)*(1+z) = Lν(em)*(1+z)/(1+z)4 Sνobs ~ {ν(em)}2+ß * (1+z) /(1+z)4 = {ν(obs)}2+ß *(1+z)2+β* (1+z) /(1+z)4 with ß=1.5-‐2 Sνobs does not vary a lot with z

Sensi$vity in total LIR (5-‐1000 µm) also depends on the assumed IR SED (peak of the SED) but remains roughly constant in submm and at large redshi1s


Casey & Cooray 2014)

X-‐match at different wavelength: Main issue: the different spa&al resolu&ons

Subaru I-‐band IRAC 3.6 µm MIPS 24 µm PACS 100 µm

SPIRE 250 µm SPIRE 350 µm SPIRE 500 µm SCUBA-‐2 450 µm

VLA 20 cm MAMBO 1.2 mm AzTEC 1.1 mm SCUBA-‐2 850 µm


X-‐match can be (is o1en) ambiguous

SDSS image (g+r+i) IRAC 3.6 µm IRAC 4.5 µm SPIRE PSF


Counterparts of optical sources in far-IR images: U-band versus SPIRE/250µm Almost nothing clearly identified…….

COSMOS meeting DC June 2012

On the need of stacking ...

4

U 250 microns

Less than 1% of galaxies are detected ⇒ stacking

Z = 1.5


Heinis+13

A stacking technique is needed! Heinis et al. 2013 SPIRE-‐ 250, 350 et 500 µm

Dole et al. 2006 MIPS stacking, CIB


Stacking is needed essen&ally in IR only average trends are measured


Reddy+12: Op&cal limits deep enough to detect L* galaxies, not in IR-‐mm

Buat+12 Galaxies detected individually

Heinis+13 Stacking only



•  The global evolu$on of star forma$on and dust aRenua$on with redshiS:

Luminosity func$ons and densi$es, evolu$on with redshiS



The shape of the luminosity functions:

L<<L* ~power law L>>L* ~ Gaussian in log(L) Saunders+90

2 power-‐laws (Sanders+03)

Schechter func$on

Φ(L) = ϕ0 (L/L*)-‐0.6 L<L*, Φ(L) = ϕ0 (L/L*)-‐2.2 L>L*

A Schechter func&on in UV-‐op&cal, a double power law or a log-‐normal+power law in IR to avoid the sharp decrease oShe Schechter func$on and reproduce the high number of luminous IR galaxies

L* = close to the « knee » of the Luminosity Func&on

Calcula&ons for the Schechter func&on only

The limits of the integral can be chosen different of 0 and ∞, with more realis&c values (106 to 1014 L for example)

€

Ntot = Φ(L)dL0

∞

∫

€

ρ(L) = L Φ0

∞

∫ (L)dL

€

Φ0

∞

∫ (L)dL = Φ*Γ(1+α)

Luminosity density

IR luminosity func$ons (IRLF) with Spitzer and Herschel data (mainly)


Evolu&on of the IRLF with z Herschel data up to z~3

Compiled by Casey & Cooray 2014)

And the corresponding luminosity & SFR densi&es


The contribu&on of LIRGs and ULIRGs increases with z LIRGs contribu$on peaks at z~1 ULIRGs contribu$on increases up to z~2

Due to the evoluAon of the IRLF with z

SFR only measured in IR

ρSFR ~ρIR Magnelli+13

Combining UV and IR LFs: a measure of the whole star forma&on

(‘visible ’ and hidden by dust)


As shown before the LF are very different

Burgarella+13

Total SFR density and dust aRenua$on

ρSFR (tot) = ρSFR(UV)+ρSFR(IR)

ρSFR(IR)> ρSFR(UV) at all redshi1s (z<3.5) A plateau (or slight increase) of ρSFR at z>1

AKenua&on: ρ(LIR) / ρ(LUV), proxy of Auv

AKenua&on increases up to z=1 and then decreases AUV(z=0) ~AUV(z=4)


ρ(L IR) / ρ(L

UV)

AUV (m

ag)

ρ SFR(M

yr

-‐1 M

p-‐3 )

M* density directly measured or deduced from ρSFR (t): In reasonable agreement

NO MEASURE OF IR, dust aRenua$on measured with the UV slope


Madau & Dickinson 2014

The UV slope difficult to measure with a few photometric data Finkelstein+12

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5AUV,CIGALE**(mag)*

AUV**(m

ag)*from*Eq.7*and**α*

αref*

�

�

AUV( SED fiyng with IR data)

Auv (from β) X GALEX bands

+ Filters 1 & 3 o Filters 1 & 2 ☐ Filters 2 & 3

β mul&-‐bands


Buat+13, intermediate band filters, z=2



•  The global evolu&on of the star forma&on and dust aKenua&on with redshi1:

•  Spectral energy distribu$ons Evolu$on with redshiS

•  Fundamental rela&ons between SFR, Mgas & Mstar


Herschel-‐PACS/SPIRE Elbaz+10, A&A Herschel special issue

• LIRtot: 8-‐1000 µm; best fit with templates, data above 30 µm -‐-‐> Secure value of LIRtot • LIR(λ) from the SED-‐LIR library of local templates (Chary & Elbaz 01) (cf lecture 2) -‐-‐> LIR(λ) depends on local calibra$ons

• For z<1.5, 24 µm data give correct es&mate of Lir, • For z > 1.5, best es&mates with 160 and 250 µm data, 24 µm data over-‐es&mate LIRtot


Checking pre-‐Herschel local templates

250 and 350 µm data over-‐esAmate at LIR at z<1.5: presence of cold dust

L IR(λ)/L

IRtot

When using local templates, LIR calculated with 24 µm only is overes&mated at z=2( Nordon+11) local templates are not representa$ve of the PAH emission of high-‐z galaxies (Elbaz+11)

24 µm obs. 8 μm rest frame 100-‐160 µm 30-‐50 µm rest frame 250-‐500 µm 80-‐160 µm rest frame

log(L iRto

t ) (with

Hersche

l data)

Local templates versus high redshift (z=2) observations

ISAS-‐ 27 nov. 2013

Z=2, Nordon+11

Log(LIR(24µm)) with local templates

Z=2

Templates for the distant universe dependent on the SFR ac$vity

• ‘Normal’, Main Sequence galaxies:(average SFR/M*) PAH are prominent at all redshi1, the dust temperature increase with redshi1 • Starburst galaxies: (high SFR/M*), less PAH, warm dust


MS= « normal galaxies »

SB= Starburs&ng galaxies

Magdis+12

Original local templates New Main Sequence templates

L IR from

mon

ochrom

a&c flu

x/L IR (total-‐all MIPS-‐Hersche

l data)


The measure of LIRtot remains robust when Herschel data are available


Berta+13

Example of global fits…. Berta+13


Some examples of SEDs, with their best fit obtained with CIGALE Buat+11 An absorp$on feature at 2175 A rest frame clearly seen and modeled. The full UV-‐to-‐IR SED fiRed.

Cf Lecture 2





•  Spectral energy distribu&ons •  Fundamental rela$ons between SFR, Mgas & Mstar:

SFR-‐Mstar : Main Sequence

SFR-‐Mgas : Schmidt-‐KennicuK law







SFR-‐Mgas : Schmidt-‐KennicuK law


We are trying to understand very basic trends for local and distant galaxies: the definition of the Main Sequence


Stellar Mass

Star fo

rma$

on ra

te


Measured in the nearby universe with SDSS data and ac$ve star forming galaxies (Brinchmann+04, Salim+07, Peng+10)

τ=M*/SFR~10 Gyr in the nearby universe Specific star sSFR= SFR/M*

Measures at intermediate redshi1 with IR (SPITZER) data


Noeske+07

sSFR (specific star forma&on rate): SFR/Mstar


Evidence for downsizing: sSFR decreases when Mstar increases  Slope of the SFR-‐Mstar different from 1

May differ if only ac&ve star forming galaxies are selected

A huge amount of papers on the topic….

Noeske+07


z~2: Herschel data to measure reliable SFR

Only high SFR Biased towards massive starbursts

Starbursts represent only 10% of the SFR density

Rodighiero+11

The specific star forma$on rate sSFR is used to measure star forma&on ac&vity and to be compared to models Par&cularly interes&ng at high z to calibrate models

the sSFR measured with UV and IR stacked data in the COSMOS field: high values from z=1.5 and 4, seems inconsistent with models. Possible presence of a plateau for z>2


Heinis+13

de Barros+13

A plateau of sSFR at z>2 is also reported from op&cal surveys but the presence of emission lines in the band may strongly modify the results



Trying to understand galaxy evolu&on from the evolu&on of the SFR-‐Mstar rela&on: evolu&on of MW like galaxies

S&ll controversed

Van Dokkum+13

Following galaxies on the main Sequence and across &me

MW model






SFR-‐Mgas : Schmidt-‐KennicuR law


Stars form from gas: searching for the physical rela&on SFR-‐Mgas

KennicuW & Evans 2012 Black points: normal galaxies Red points: IR selected galaxies Green points: starburs&ng galaxies Blue open squares: low mass galaxies Purple crosses: low surface brightness galaxies Magenta square: Milky Way

Blue line: n=1.4


Schmidt-‐KennicuK rela&on Gas= HI+H2

Z=0


Bigiel+08

Re-‐inves&ga&on inside nearby galaxies: careful measure of SFR (composite star forma&on tracer (FUV+24µm) and HI and H2 (CO (2-‐1)) surface densi&es

 No correla&on with HI (sharp increase)  A linear rela&on with slope unity with H2


Deple$on $mescale: tdep= Mgas/SFR

Low values of tdep in galaxies forming stars ac&vely: Evidence for gas accre$on or rapid evolu$on of galaxies

Connec&ng the evolu&on of sSFR & of the molecular gas frac&on


tdep=0.7 Gyr

Gas frac$on correlates with sSFR FiKed with a constant tdep= 0.7 Gyr offset from the mean MS controlled by the gas frac&on

MH2/(M

H2+M

*) z=1-‐1.5 & 2-‐3

tdep= MH2/SFR

Main Sequence (MS) Galaxies

€

MH 2

MH 2 +M*=

1

(1+ sSFR× tdep[ ]−1)

slight decrease of tdep with z  Increase of the SFE = 1/tdep  Secondary effect

z=0

z=1-‐1.5 z=2-‐3

Connec&ng the evolu&on of sSFR & of the molecular gas frac&on (cont’d)


Tacconi+13

MS galaxies only

X10

Much smaller deple&on &mescale for starburst galaxies

Daddi+10

H2 is measured with the emission of CO lines


Poten&al Issue: H2 (total molecular mass) ra&o to CO(luminosity)

Well measured in the MW only α(MW) ~ 4 M/(K kms-‐1pc2)

Local starburst: α(SB) ~ 0.8 M/(K kms-‐1pc2)

Distant galaxies? Starburst or MW values? MS galaxies: α(MW) High sSFR galaxies: α(SB)

Combes+13

α(MW)

Gas content & dust mass

Based on the gas to dust ra&o δGDR * Mdust = Mgas = MH2 +MHI

depends on metallicity calibrated


δ G

DR

Leroy+11 (local universe), Magdis+11

• Mdust ,LCO and δGDR known αCO deduced • Mdust and δGDR known Mgas deduced

San&ni+14, Magdis+12


Which CO line? Thanks to the CO ladder, different CO lines can be measured at different redshi1

Panuzzo+10, M82 <10% ALMA sensi&vity

Toward an explana$on of the steep decline of the star forma$on from z=1 to z=0?

•  Most of the ac&ve star forming galaxies on the Main Sequence: LIRGs at z=1, ULIRGs become important at z>=2, starburst galaxies have minor role.

•  Stars form from the (Molecular) gas with a rather constant efficiency at a given z for MS galaxies (SFR/MH2~1/tdep)

•  The sSFR varia&on is mainly contolled by the varia&on of the molecular gas frac&on.

•  The schema may well not be valid for MW-‐like galaxies •  The CO-‐to-‐H2 conversion factor remains a source of uncertainty, possible measure of the gas content with the dust mass


Recent review papers

•  Casey & Cooray, 2014 Physics reports, in press •  Madau & Dickinson, ARAA 2014, arXiv:1403.007

•  Carilli & Walter, 2013, ARAA 51, 105

•  KennicuK & Evans 2012, ARAA 50, 531


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