David Elbaz – Gas content and cosmic star formation history – SKA 2019 1
Gas content and cosmic star formation history:
Open issues at the dawn of SKA
D.Elbaz
1. The missing side of the cosmic SFR history
2. The paradox of star-formation and gas flows
3. Resolving star-formation in galaxies
4. What is the role of galaxy mergers in the end ?
David Elbaz – Gas content and cosmic star formation history – SKA 2019 2
1. The missing side of the cosmic SFR history
David Elbaz – Gas content and cosmic star formation history – SKA 2019 3
Madau & Dickinson 2014
David Elbaz – Gas content and cosmic star formation history – SKA 2019 4
Madau & Dickinson 2014Gruppioni +2017
GRB
Herschel
UV
David Elbaz – Gas content and cosmic star formation history – SKA 2019 5
David Elbaz – Gas content and cosmic star formation history – SKA 2019 6
David Elbaz – Gas content and cosmic star formation history – SKA 2019 7
MUSE
Lya traces the CGM3<z<6 ~10x UV sizeWisotzki et al 2018
+ 72 HST-dark galaxies detected by MUSEBacon et al 2017
David Elbaz – Gas content and cosmic star formation history – SKA 2019 8
2. The paradox:
universality & inefficiency of observed SF
vs
efficiency of gas flows & expected peculiarity
David Elbaz – Gas content and cosmic star formation history – SKA 2019 9
A paradoxMain sequence => galaxies secularly evolve without caringabout their environment
infall (M¤yr-1)
But their growth is regulated by their environment through infall
Infall needed since depletion times of a few 100Myr
David Elbaz – Gas content and cosmic star formation history – SKA 2019 10
A paradoxUniverse highly inefficient in making stars
Universe highly efficient in concentrating starsTumlinson +2017, adapted from Behroozi +2010
adapted from Van der Wel +14
David Elbaz – Gas content and cosmic star formation history – SKA 2019 1111
Can feedback save our representation of the Universe ?
observations
theory
redshift evolution of sSFR=SFR/M*
Illustris simulationVogelsberger +2014, Nature
galaxies on FIRE simulationHopkins +2014, MNRAS
David Elbaz – Gas content and cosmic star formation history – SKA 2019 12
3. Resolving star-formation in galaxies
David Elbaz – Gas content and cosmic star formation history – SKA 2019 13
Franco, Elbaz +19, in prep.
David Elbaz – Gas content and cosmic star formation history – SKA 2019 14
ALMA targets: 4.5µm sources undetected by HSTin GOODS-S, UDS and CANDELS-COSMOS
Wang, Schreiber, Elbaz +18
0.4-4 mJystacked IR SED peaks@350-500μmà z ~ 4
H-d
rop
outs
[4.5] brighter than 24à M�> 1010.1-10.4 M⊙ at z ∼ 3 − 6
HST H-band fainter than 27 (AB)(Wang, Elbaz +16)
David Elbaz – Gas content and cosmic star formation history – SKA 2019 15
Wang, Schreiber, Elbaz et al. 2019
David Elbaz – Gas content and cosmic star formation history – SKA 2019 16
ALMA (0.2” resolution) vs HST (0.1”)
Elbaz et al. 2018See also Barro et al. 2016,17
A population of compact MSgalaxies with short depletion timesà Compact SB within the MSà Origin ?
IR luminosity surface density
Depletion time (Myr)
MS
David Elbaz – Gas content and cosmic star formation history – SKA 2019 17
Resolving star formation within galaxies with SKA
1
z=0.11 z=0.189 z=0.56 z=2.39
HST H
Resolved SF
SKA
Ultradeep0.05uJy/beam
Deep0.2uJy/beam
Wide1uJy/beam
Coogan +2019 in prep
SKA simulation in collaboration with the SKA O
ffice in M
anchester -1.4 GHz, FW
HM=0.6’’
David Elbaz – Gas content and cosmic star formation history – SKA 2019 18
Scoville +17
gas depletion times gas mass fractions
z
SFRhigher star formation at high zdue equally to : more gas & higher SF efficiency
But aCO & G/D uncertain…
David Elbaz – Gas content and cosmic star formation history – SKA 2019 19
Walter +2019 – White Paper
1000h ngVLA
Cosmic history ofcold molecular gas
But aCO, G/D uncertain
David Elbaz – Gas content and cosmic star formation history – SKA 2019 20
4. What is the role of galaxy mergers in the end ?
David Elbaz – Gas content and cosmic star formation history – SKA 2019 2121
% starbursts
redshift
2.5xMS
3xMS
4xMS
Merger rate / simulations (Hopkins +10)
Merger rate / pairs (Kartaltepe +07)
Role of merger-driven starbursts…
Schreiber et al. 2017
David Elbaz – Gas content and cosmic star formation history – SKA 2019 22
Falgarone +17& in prep
David Elbaz – Gas content and cosmic star formation history – SKA 2019 23
Gas content and cosmic star formation history:
Open issues at the dawn of SKA
1. The missing side of the cosmic SFR history
SKA will provide both deep and wide surveys key to probe the missing side
2. The paradox of star-formation and gas flows
SKA will provide both atomic and molecular gas reservoirs measurements
3. Resolving star-formation in galaxies
SKA will resolve star-formation in galaxies potentially even at z≥2
3. What is the role of galaxy mergers in the end ?
SKA will allow us to better understand the origin of starbursts in relation with mergers
