Mathieu PUECH GEPI

Observatoire de Paris

Rebuilding discs with gas-rich major merger

ESO 3D2014 – March 2014

, R. Delgado, M. Rodrigues, S. Fouquet+ J.L. Wang, L. Athanassoula, P.

Hopkins

M 31

NGC 2997

M83

M100 SABbcNGC 1365

Mstellar > 2x1010 Mo

72% of local galaxies are spiral

Intermediate-mass galaxies

Mstellar > 1.5x1010Mʘ

Likeliest progenitors of present-day ~M* spirals,

sixbillion years ago

Sample selection

MJ < -20.3 & 0.4 < z < 0.9

4 fields, including the CDFS

SF sub-sampleEW0([OII])>15 Å

0.4 < z < 0.75

The IMAGES survey

3D SpectroscopyVLT/FLAMES-GIRAFFE

(R~10000, 8-24hrs exposure)

ImagingACS images (≥ 3 orbits)

Multi-λ photometrySpitzer, GALEX, ACS, EIS,etc.

Integrated spectroscopyVLT/FORS2 (600RI+600z) (≥ 3 hrs each)

Yang+08

LF, z=0.5 Pozzetti+03

Representativity

IMAGES = representative sample of 63 M* galaxies selected in 4 different fields of view

(unbiased by cosmic variance)

LF, z=1.0

z=0.45-0.7 SFR-M*

Sequence from Noeske+07;Dutton+10

Half of z~0.6 spirals had peculiar morphologies

Delgado-Serrano+10

Morpho-kinematic classification

50% of intermediate-mass galaxies at z~0.6 are not relaxed morphologically OR kinematicallyHammer+09b

80% of RD are Sp

95% of CK are

M, or Pec/M-T

Neichel+08

86% of PR are M, or Pec/M-T

Anomalous kinematics of the ionized gas is linked to anomalous morphological

distribution of the stars

Associating Morpho-kinematicswith physical processes

COLD

STREAMS

CLUMP

FRAGMENT.

MAJOR

MERGERS

MINOR

MERGERSOUTFLOWS

SECULAR

EVOLUTION

Associating Morpho-kinematicswith physical processes

COLD

STREAMS

CLUMP

FRAGMENT.

MAJOR

MERGERS

MINOR

MERGERSOUTFLOWS

SECULAR

EVOLUTION

20 % of z~0.6 M* galaxies

10 % of rotators(Puech10)

Associating Morpho-kinematicswith physical processes

COLD

STREAMS

CLUMP

FRAGMENT.

MAJOR

MERGERS

MINOR

MERGERSOUTFLOWS

SECULAR

EVOLUTION

20 % of z~0.6 M* galaxies

10 % of rotators(Puech10)

<8 % of z~0.6M* galaxies

(Rodrigues+12)

Associating Morpho-kinematicswith physical processes

COLD

STREAMS

CLUMP

FRAGMENT.

MAJOR

MERGERS

MINOR

MERGERSOUTFLOWS

SECULAR

EVOLUTION

20 % of z~0.6 M* galaxies

10 % of rotators(Puech10)

<8 % of z~0.6M* galaxies

(Rodrigues+12)

GIRAFFU IFU resolution ~ 7 kpc

@ z=0.6

(Puech+07,12)

Associating Morpho-kinematicswith physical processes

COLD

STREAMS

CLUMP

FRAGMENT.

MAJOR

MERGERS

MINOR

MERGERSOUTFLOWS

SECULAR

EVOLUTION

20 % of z~0.6 M* galaxies

10 % of rotators(Puech10)

<8 % of z~0.6M* galaxies

(Rodrigues+12)

GIRAFFU IFU resolution ~ 7 kpc

@ z=0.6

(Puech+07,12)

Cold flows ↘ (Keres+09,Nelson+

13)Kinematic imprint

too weak (Hopkins+10;Puech+

12)

Associating Morpho-kinematicswith physical processes

COLD

STREAMS

CLUMP

FRAGMENT.

MAJOR

MERGERS

MINOR

MERGERSOUTFLOWS

SECULAR

EVOLUTION

20 % of z~0.6 M* galaxies

10 % of rotators(Puech10)

<8 % of z~0.6M* galaxies

(Rodrigues+12)

GIRAFFU IFU resolution ~ 7 kpc

@ z=0.6

(Puech+07,12)

Cold flows ↘ (Keres+09,Nelson+

13)Kinematic imprint

too weak (Hopkins+10;Puech+

12)

Kinematic imprinttoo weak

(Hopkins+10;Puech+12)

Hammer et al. 2009b

18/27 non (or semi-)relaxed galaxies have « secured » merger models(ZENO or GADGET2 codes)

When (the best) model

matches theobservations Peirani et al. 2009

Dating the observation timeBeginning of the

simulationTime

Time

Puech+12

Gas compression phases are well constrained and consistant with expectations

Merger rate: observations vs. theory

The apparent large occurrence (~33%) of merger features in z~0.6 galaxies is

due to the large visibility timescale of the morpho-kinematic observations (~1.8

Gyr in the pre-fusion phase and post-fusion phases).

Puech, Hammer, Hopkins et al. (2012)

See also Lopez-Sanjuan+13 (MASSIV)

• Observations (IMAGES)

Theory (Hopkins' semi-empirical model)

μbaryon ≥ 0.25 and Mbaryon=1010.2-1011 M⊙Impact of possible systematics from Mstellar measurements

on theoretical predictions

Hammer et al. 2009b

z=0 ; Schiminovich08z=0 ; GASS survey

z=0.6, IMAGES

z=2, Erb+06

z=1, Tacconi+10

z=2, Erb+06

z=2, Tacconi+10

z=1.5, Daddi+10

Properties of the IMAGES merger progenitors

Reformation of a significant disk expected after such gas-rich major mergers

(Hopkins+09-12 ; Keres+12 w/ AREPO)

Rodrigues+12

Semi-empirical models with gas-rich mergers

Rodrigues+12

Gas

fra

ctio

n G

as f

ract

ion

(%)

(%)

Lookback time Lookback time (Gyr)(Gyr)

Hopkins et al 2010

IMAGES

Hopkins+10

See also cosmological simulations: Keres+12;

Guedes+11, Font+11,

Brook+11, Aumer+13 and

others

Hopkins et al. (2009-2011)

+

Main sequence of SFGs & major

mergers

19Tension between the SFR peak duration and

the duty cycle of major mergers (Noeske+07)?

0.3 dex

Duty cycle:0.4-2.5 Gyr(1-2 )

Cox+08

Individual major mergers:Small SFR peak duration

Main sequence of SFGs & major

mergers

20Duty cycle is statistical: need to consider the

average SFR peak duration in an representative sample!

0.3 dex

Duty cycle:0.4-2.5 Gyr(1-2 )

Cox+08

Average: much larger SFR peak duration

Main sequence of SFGs & major

mergers

21No contradiction between duration of the average SFR peak and major merger duty

cycle (Noeske+07)

1.8 Gyr

0.3 dex

Duty cycle:0.4-2.5 Gyr(1-2 )

22

SFR fraction associated to

mergers

≈ Morphologically-selected mergersConsistent with Robaina+09: 15-21% (see also Jogee+09)

±5%

23

SFR fraction associated to

mergers

SFR enhancementConsistent with Robaina+09: 8±3% (see also Jogee+09)

SFR fraction associated to

mergers

24

Total SFR fraction

associated to major mergers:

53-88%

Conclusions Morpho-kinematic observations are sensitive to all the phases of the major merger process

The observed major (μbaryon

≥ 0.25) in Mstellar

=1010-1011 M⊙ is found to be in

very good agreement with theoretical predictions, without any fine-tuning

33 % of all z~0.6 interm.-mass galaxies are on-going major mergers, which show strong kinematic and morphological perturbations. 50 % of local galaxies have undergone a major merger since z=1.5 (see also MASSIV results).

There is no tension between these fractions and the Main Sequence of star-forming galaxies, the fraction of local bulgeless galaxies (B/T < 0.2, Puech+12), or the fraction of LIRGs

Such mergers should on average produce bulge galaxies with a significant disk. Simulated examples: M31 (Hammer+10), NGC5907 (Wang+12).

26

Example of NGC 5907

Wang+12

Best models : 1:3 to 1:5 major mergers with fgas=60-80% in the progenitors

IRAC

MartinezDelgado+08

Optical vs. IR/Spitzer:

Extras

Adapted from Contini+11

Observing galaxy evolution

+zC-SINF

DYNAMO

MASSIV

● RD

■ PR

▲ CK

20%

16%

27%

32%

25%

43%

HST VF S/N VF-model −model

+/- (<)12%(upper limit:Kutdemir+08,10)

? ?

● RD

■ PR

▲ CK

Flores+06Puech+06aYang+07

Sample Gal. Population

Kinematic ClassificationFLAMES-GIRAFFE 3D spectroscopy

Associating Morpho-kinematicswith physical processes

CK galaxies: Morpho-kinematic disturbances are global, not local:

GIRAFFU IFU

resolution

~ 7 kpc @ z=0.6

Puech et al. (2007)

Puech (2010)

Clumpy galaxies in IMAGES

They represent only ~20% of z~0.6, intermediate-mass galaxies

@ z>1 (Elmegreen+05)

Clumpy galaxies in IMAGES

Half of them are rotators (RD or PR) as

expected in clumpy galaxies (Bournaud et

al. 2007, 2008).

Gas is not necessarly shock-heated at the Virial Radius:

Binney 1977

Birnboim & Dekel 2003

Keres et al. 2005

Dekel & Birnboim 2006

Dekel et al. 2009

Keres et al. 2009

Spherical cold gas

accretion

Streams of cold gas

entering massive haloes

The standard picture of galaxy formation:Recent developments

Brooks+09shocked« Clumpy »

Unshocked

Cold gas accretion tends to vanish in massive halos at z<1 (<1.5 Mo/yr at z~0.6,

see Keres et al. 2009, Brooks et al. 2009):

z~0.6

Cold streams at z~0.6

Puech (2010)

Global perturbationsHopkins et al. (2010)

Merger rate

Secular

Perturbation/merger

Accretion rate

Puech, Hammer, Hopkins et al. (2012)

Rotators:

Time-scale amplification for

internal or external global perturbations

IMAGES

Kinematic perturbations are too strong to be associated to accretion or internal perturbations

Associating Morpho-kinematicswith physical processes

Only a handful of galaxies have significant shifts between

abs. and emission lines (Puech10; Rodrigues+12).

[NeIII] HeI Hβ

Integrated FORS2 spectroscopy

~162km/s

Barden et al. (2009)

hardly detectable abovez~0.5-1

Absence of tidail tails, shells, etc. is not an

evidence of anabsence of merger

above z~0.5-1

ObservingLSB

material