Rebuilding local discs with gas-rich major mergers Mathieu PUECH - - PowerPoint PPT Presentation

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Rebuilding local discs with gas-rich major mergers Mathieu PUECH - - PowerPoint PPT Presentation

Nov 13, 2023 191 likes •396 views

Rebuilding local discs with gas-rich major mergers Mathieu PUECH Coll.: F. Hammer, H. Flores, M. Rodrigues, Y. Yang, J. Wang, L. Athanassoula, P. Hopkins et al. Malta Conf. Oct. 2017 Local Hubble Sequence 72% of M stellar = 2x10 10-11 M o

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Mathieu PUECH

Coll.: F. Hammer, H. Flores, M. Rodrigues, Y. Yang, J. Wang,

  • L. Athanassoula, P. Hopkins et al.

Rebuilding local discs with gas-rich major mergers

Malta Conf. Oct. 2017

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Local Hubble Sequence

SDSS images Delgado-Serrano et al. 2010

72% of Mstellar = 2x1010-11 Mo galaxies are spirals

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Hubble Sequence at z~0.6

HST/ACS images Delgado-Serrano et al. 2010

31% of Mstellar > 1.5x1010 Mo galaxies are spirals

Same depth, resolution and rest-frame wavelengths than SDSS

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Morphology vs. Kinematics

# Complex # Perturbed # Rotating

IMAGES survey z~0.6, Neichel+08 86% of perturbed rotation have Pec morpho. 95% of complex kinematics have Pec morpho. 80% of rotating galaxies have Sp morpho.

50% of intermediate-mass galaxies at z~0.6 have perturbed morphologies OR kinematics

Hammer+09

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How to identify all mergers?

Rotation-dominated Rotating disc

Adapted from Turner+17; Puech et al., in prep.

  • 1. VF with single gradient
  • 2. V/s > 1
  • 3. s peak = rotation center
  • 4. PAkin = PAmorph
  • 5. rotation center = center of mass

Re-analysis of KMOS3D data z~0.9 Rodrigues+17 IMAGES z~0.6

See also Kassin+12, Simons+17

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Rotation-dominated Rotating disc

Adapted from Turner+17; Puech et al., in prep.

  • 1. VF with single gradient
  • 2. V/s > 1
  • 3. s peak = rotation center
  • 4. PAkin = PAmorph
  • 5. rotation center = center of mass

Interacting discs can look like rotating discs

Re-analysis of KMOS3D data z~0.9 Rodrigues+17 IMAGES z~0.6

How to identify all mergers?

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Rotation-dominated See Rodrigues+17 See M. Rodrigues’ poster

Adapted from Turner+17; Puech et al., in prep.

  • 1. VF with single gradient
  • 2. V/s > 1
  • 3. s peak = rotation center
  • 4. PAkin = PAmorph
  • 5. rotation center = center of mass

See also Robertson&Bullock08; Gonçalves+10; Hung+15,16

How to identify all mergers?

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SLIDE 8

Hammer+09

Major merger models

2/3 of perturbed galaxies have secured major merger models

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Merger rate: observations vs. theory

Puech+12, IMAGES Rodrigues+17, KMOS Rodrigues+17b, pairs

Excellent agreement on the gas-rich major merger rate

Puech+12, IMAGES

Curves: LCDM predictions from Hopkins+10

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z=0 ; Schiminovich08 z=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

Expected Impact of gas fraction

Reformation of a significant disk after gas-rich major mergers

Barnes02; Springel & Hernquist05; Robertson+08; Hopkins+09-12 ; Governato+09; Aumer+13,14; Athanassoula+16

Rodrigues+12 Hopkins et al 2010

I M A G E S

Hopkins+10

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“Mergers do not contribute significantly to the star formation history”

Puech+12, 14

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“Mergers do not contribute significantly to the star formation history”

≈ Morphologically-selected mergers

Consistent with Robaina+09: 15-21% (see also Jogee+09)

23% Puech+12, 14

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“Mergers do not contribute significantly to the star formation history”

SFR enhancement

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

Puech+12, 14 11%

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“Mergers do not contribute significantly to the star formation history”

Puech+12, 14 23%

Total SFR fraction associated to major mergers: 53-88%

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Scatter of the SFR-mass relation

0.3 dex Duty cycle: 0.4-2.5 Gyr (1-2 s)

Puech+14 Cox+08

SFR Peak amplitude and duration too small/short?

Duty cycle is statistical: need to consider the average SFR peak duration in an representative sample!

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Scatter of the SFR-mass relation

0.3 dex Duty cycle: 0.4-2.5 Gyr (1-2 s)

Puech+14 Cox+08

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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Scatter of the SFR-mass relation

No tension between major mergers and the SFR-mass relation

0.3 dex Duty cycle: 0.4-2.5 Gyr (1-2 s)

Puech+14 1.8 Gyr

Average peak in the IMAGES representative sample

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LIRGs and major mergers

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IMAGES sample: 58% of LIRGS are in the fusion phase

From Melbourne+06, see also Zheng+04

Compact LIRGs

Elbaz+11

~ 42% expected to have spiral morphologies

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Most present-day spirals have no or pseudo-bulges (Kormendy+10)

Sauvaget+17 See also Kelseman&Nusser12

Gas-rich major mergers can (often) produce pseudo-bulges

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Conclusions

  • 50 % of z~0.6 intermediate-mass galaxies show strong kinematic and morphological

perturbations; interacting galaxies can look like rotation-dominated or even rotating discs!

  • The 2/3 of them are well reproduced by major merger models and match merger rate

expectations from LCDM: ~ 50 % of local galaxies have undergone a major merger since z~1.5

  • These mergers are gas-rich => disk dominated remnants => ~ 50% local spiral

galaxies should have rebuilt a disc since z~1.5

  • Fraction of SFR associated to major mergers at z~0.6: hugely definition-dependent!

<10% if just considering the SFR enhancement; > 50% if accounting for all merger phases

  • There is no tension between the role of major mergers and the scatter of the SFR-

mass relation, the fraction of LIRGs with Sp morphologies, or the fraction of local pseudo-bulged galaxies