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Rebuilding discs with gas-rich major merger
Mathieu PUECH GEPI Observatoire de Paris
, R. Delgado, M. Rodrigues, S. Fouquet
J.L. Wang, L. Athanassoula, P. Hopkins
ESO 3D2014 March 2014
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72 of local galaxies are spiral
Mstellar gt 2x1010 Mo
NGC 2997
NGC 1365
M100 SABbc
M 31
M83
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The IMAGES survey
Sample selection MJ lt -20.3 0.4 lt z lt 0.9 4
fields, including the CDFS
Intermediate-mass galaxies Mstellar gt
1.5x1010M? Likeliest progenitors of present-day
M spirals, six billion years ago
SF sub-sample
EW0(OII)gt15 Å 0.4 lt z lt 0.75
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Representativity
LF, z0.5
Pozzetti03
LF, z1.0
z0.45-0.7 SFR-M Sequence from
Noeske07Dutton10
Yang08
IMAGES representative sample of 63 M galaxies
selected in 4 different fields of view
(unbiased by cosmic variance)
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(No Transcript)
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Morpho-kinematic classification
Neichel08
Anomalous kinematics of the ionized gas is linked
to anomalous morphological distribution of the
stars
50 of intermediate-mass galaxies at z0.6 are
not relaxed morphologically OR kinematically
Hammer09b
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Associating Morpho-kinematics with physical
processes
COLD STREAMS
CLUMP FRAGMENT.
MAJOR MERGERS
MINOR MERGERS
SECULAR EVOLUTION
OUTFLOWS
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Associating Morpho-kinematics with physical
processes
20  of z0.6 M galaxies 10  of
rotators (Puech10)
COLD STREAMS
CLUMP FRAGMENT.
MAJOR MERGERS
MINOR MERGERS
SECULAR EVOLUTION
OUTFLOWS
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Associating Morpho-kinematics with physical
processes
20  of z0.6 M galaxies 10  of
rotators (Puech10)
COLD STREAMS
CLUMP FRAGMENT.
MAJOR MERGERS
lt8  of z0.6 M galaxies (Rodrigues12)
MINOR MERGERS
SECULAR EVOLUTION
OUTFLOWS
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Associating Morpho-kinematics with physical
processes
20  of z0.6 M galaxies 10  of
rotators (Puech10)
COLD STREAMS
CLUMP FRAGMENT.
MAJOR MERGERS
GIRAFFU IFU resolution 7 kpc _at_
z0.6 (Puech07,12)
lt8  of z0.6 M galaxies (Rodrigues12)
MINOR MERGERS
SECULAR EVOLUTION
OUTFLOWS
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Associating Morpho-kinematics with physical
processes
Cold flows ? (Keres09,Nelson13) Kinematic
imprint too weak (Hopkins10Puech12)
20  of z0.6 M galaxies 10  of
rotators (Puech10)
COLD STREAMS
CLUMP FRAGMENT.
MAJOR MERGERS
GIRAFFU IFU resolution 7 kpc _at_
z0.6 (Puech07,12)
lt8  of z0.6 M galaxies (Rodrigues12)
MINOR MERGERS
SECULAR EVOLUTION
OUTFLOWS
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Associating Morpho-kinematics with physical
processes
Cold flows ? (Keres09,Nelson13) Kinematic
imprint too weak (Hopkins10Puech12)
20  of z0.6 M galaxies 10  of
rotators (Puech10)
COLD STREAMS
CLUMP FRAGMENT.
MAJOR MERGERS
Kinematic imprint too weak (Hopkins10Puech12)
GIRAFFU IFU resolution 7 kpc _at_
z0.6 (Puech07,12)
lt8  of z0.6 M galaxies (Rodrigues12)
MINOR MERGERS
SECULAR EVOLUTION
OUTFLOWS
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18/27 non (or semi-)relaxed galaxies have
 secured  merger models (ZENO or GADGET2 codes)
Hammer et al. 2009b
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Dating the observation time
Time
Beginning of the simulation
Time
Peirani et al. 2009
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Gas compression phases are well constrained and
consistant with expectations
Puech12
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Merger rate observations vs. theory
Theory (Hopkins' semi-empirical model) µbaryon
0.25 and Mbaryon1010.2-1011 M?
Impact of possible systematics from Mstellar
measurements on theoretical predictions

• Observations (IMAGES)

Puech, Hammer, Hopkins et al. (2012) See also
Lopez-Sanjuan13 (MASSIV)
The apparent large occurrence (33) of merger
features in z0.6 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).
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Properties of the IMAGES merger progenitors
Rodrigues12
Hammer et al. 2009b
z2, Erb06
z2, Erb06
z1.5, Daddi10
z0.6, IMAGES
z2, Tacconi10
z1, Tacconi10
z0  Schiminovich08
z0  GASS survey
Reformation of a significant disk expected after
such gas-rich major mergers (Hopkins09-12 
Keres12 w/ AREPO)
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Semi-empirical models with gas-rich mergers

See also cosmological simulations Keres12
Guedes11, Font11, Brook11, Aumer13 and others
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Main sequence of SFGs major mergers
0.3 dex
Duty cycle 0.4-2.5 Gyr (1-2 s)
Individual major mergers Small SFR peak duration
Tension between the SFR peak duration and the
duty cycle of major mergers (Noeske07)?
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Main sequence of SFGs major mergers
0.3 dex
Duty cycle 0.4-2.5 Gyr (1-2 s)
Average much larger SFR peak duration
Duty cycle is statistical need to consider the
average SFR peak duration in an representative
sample!
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Main sequence of SFGs major mergers
1.8 Gyr
0.3 dex
Duty cycle 0.4-2.5 Gyr (1-2 s)
No contradiction between duration of the average
SFR peak and major merger duty cycle (Noeske07)
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SFR fraction associated to mergers
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Morphologically-selected mergers Consistent
with Robaina09 15-21 (see also Jogee09)
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SFR fraction associated to mergers
SFR enhancement Consistent with Robaina09 83
(see also Jogee09)
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SFR fraction associated to mergers
Total SFR fraction associated to major mergers
53-88
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Conclusions

• Morpho-kinematic observations are sensitive to
  all the phases of the major merger process
• The observed major (µbaryon 0.25) in
  Mstellar1010-1011 M? is found to be in very good
  agreement with theoretical predictions, without
  any fine-tuning
• 33  of all z0.6 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 z1.5 (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 lt 0.2,
  Puech12), or the fraction of LIRGs
• Such mergers should on average produce bulge
  galaxies with a significant disk. Simulated
  examples M31 (Hammer10), NGC5907 (Wang12).

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Example of NGC 5907
Best models 13 to 15 major mergers with
fgas60-80 in the progenitors
Optical vs. IR/Spitzer
MartinezDelgado08
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IRAC
Wang12
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Extras
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Observing galaxy evolution
MASSIV
DYNAMO
zC-SINF
Adapted from Contini11
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Kinematic Classification
FLAMES-GIRAFFE 3D spectroscopy
Sample
Gal. Population
? RD
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/- (lt)12 (upper limit Kutdemir08,10)
Flores06 Puech06a Yang07
PR
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25
? CK
27
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HST VF
s S/N
VF-model
s-model
? RD
PR
?
?
? CK
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Associating Morpho-kinematics with physical
processes
CK galaxies Morpho-kinematic disturbances are
global, not local
Puech et al. (2007)
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Clumpy galaxies in IMAGES
Puech (2010)
They represent only 20 of z0.6,
intermediate-mass galaxies
_at_ zgt1 (Elmegreen05)
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Clumpy galaxies in IMAGES
Half of them are rotators (RD or PR) as expected
in clumpy galaxies (Bournaud et al. 2007, 2008).
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The standard picture of galaxy formation Recent
developments
Gas is not necessarly shock-heated at the Virial
Radius
Streams of cold gas entering massive haloes
Binney 1977 Birnboim Dekel 2003 Keres et al.
2005 Dekel Birnboim 2006 Dekel et al.
2009 Keres et al. 2009
Spherical cold gas accretion
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Cold streams at z0.6
shocked
 Clumpy 
Brooks09
Unshocked
z0.6
Cold gas accretion tends to vanish in massive
halos at zlt1 (lt1.5 Mo/yr at z0.6, see Keres et
al. 2009, Brooks et al. 2009)
Puech (2010)
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Global perturbations
Hopkins et al. (2010)
Puech, Hammer, Hopkins et al. (2012)
Merger rate
Time-scale amplification for internal or external
global perturbations
Accretion rate
Perturbation/merger
Secular
IMAGES
Rotators
Kinematic perturbations are too strong to be
associated to accretion or internal perturbations
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Associating Morpho-kinematics with physical
processes
Only a handful of galaxies have significant
shifts between abs. and emission lines (Puech10
Rodrigues12).
162km/s
Hß
NeIII
HeI
Integrated FORS2 spectroscopy
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ObservingLSB material
hardly detectable above z0.5-1 Absence of
tidail tails, shells, etc. is not an evidence of
an absence of merger above z0.5-1
Barden et al. (2009)