Star formation in counter-rotating galaxies. Observations and - - PowerPoint PPT Presentation

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Star formation in counter-rotating galaxies. Observations and - - PowerPoint PPT Presentation

Apr 01, 2024 163 likes •471 views

Star formation in counter-rotating galaxies. Observations and Simulations Alessandro Pizzella Physics and Astronomy Dept, University of Padova, Italy Morelli, Coccato, Corsini, Dalla Bont, Fabricius, Saglia, Debattista Summary - MUSE

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Star formation in counter-rotating galaxies. Observations and Simulations

Alessandro Pizzella Physics and Astronomy Dept, University of Padova, Italy Morelli, Coccato, Corsini, Dalla Bontà, Fabricius, Saglia, Debattista

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  • MUSE spectroscopic Observations

– results

  • Modelling the counter-rotation with simulations

– results

Summary

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  • Counter-rotation: when in one galaxy components

with opposite spin co-exits (see review by Corsini 2014)

  • Stars vs. Gas
  • Stars vs. Stars
  • Stars vs. (Stars + Gas)
  • whole galaxy
  • inner/outer region
  • About 15% of S0 counter-rotates Pizzella et al.(2004)
  • We can detect up to a fraction of 20% (in luminosity)

counter-rotating stars

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MUSE @VLT à IC 719 – S0 27kpc; B

T

=14.00

Reconstructed image spaxel 0.2”x0.2”, seeing~1.4”

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IC 719 Ca Triplet region MUSE@VLT Δλ=2.5Å

R=2000-3500 ; σ = 65 - 35 km/s

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IC 719: full spectral fitting

Stellar templates eMiles-MIUSCAT (Vazdekis et al. 2012) pPXF (Cappellari & Emsellem 2004) based code (Coccato et al. 2011)

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MUSE@VLT - IC 719: full spectral fitting

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For each of the two stellar components we can measure:

  • kinematics: velocity and velocity dispersion
  • line strength à age and metallicity
  • the luminosity ratio Main/secondary à spatial shape
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IC 719 kinematics -Velocity field

Secondary component Main component

Ionized gas

1'x1' Main=70%

  • f total light
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IC 719 kinematics -Velocity dispersion

Ionized gas

Secondary component Main component 1'x1'

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Major Axis Velocity dispersion Velocity

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IC 719 2d maps: Lick Indices

Hβ Mgb

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Main Secondary

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MUSE - IC 719 Narrow band imaging

Hβ Hα [NII]658nm [SII]671nm

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Observational Results

  • Secondary component: same kinematics and same spatial

distribution as the ionized gas.

  • Secondary component: younger and metal poor in comparison with

the main component (see also Katkov, Sil’chenko et al 2013)

  • There is Star formation associated to the secondary component
  • Secondary component: thinner (q<0.15) than the main component

(q=0.2-0.3)

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Observations - Conclusions

  • The counter-rotating stellar component originated from a

gaseous disk.

  • The cold gas, acquired from outside, settled onto the galaxy

plane and formed the counter-rotating stars than now form a young, star forming thin disk

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IC 719 one of the ETG in the sample with the brightest and more extended HI emission (Grossi et al. 2009)

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Goals: test observational limits – understand the processes THE MODEL: Number of stars particles=1,838,606; Total Mass=5.683e10 Msun; Spatial resolution=50pc. Stars of different ages: stars older than 6 Gyr represent 2/3 of the total mass of the galaxy and we assume are the prograde stellar component (Debattista in prep.). We used the code SYNTRA (Portaluri+2017 MNRAS 467, 1008) à simulated MUSE datacube

We now need models to compare with

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RESULTS: the machine is working. We successfully recovered the original velocity field of both the pro-grade and counter- rotating components. NEXT STEPS: Measurements: the minimum percentage of counter-rotating stars we can detect recovering the kinematics, age and metallicity of the stellar populations; Science: the astrophysical process that brings to the formation of such galaxies.

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Summary

  • The counter-rotating disk is cold, thin, metal poor and young.
  • The counter-rotating stellar component originated from the

gaseous disk that formed form the acquisition of a gas cloud

  • We started modelling the formation of such galaxies to

properly test observational limits and better understand the acquisition mechanism.

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  • Counter-rotation: when in one galaxy components

with opposite spin co-exits (see review by Corsini 2014)

  • Stars vs. Gas
  • Stars vs. Stars
  • Gas vs. Gas
  • Stars vs. (Stars + Gas)
  • whole galaxy
  • inner/outer region
  • About 15% of S0 counter-rotates Pizzella et al.(2004)
  • We can detect up to a fraction of 20% (in luminosity)

counter-rotating stars

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Distribution of ages

  • n. of Prograde star particles

6-->8 Gyr=213,355 8-->11 Gyr=1,002,081

  • n. of Counter-rotating particles

0-->2 Gyr=213,858 2-->4 Gyr=257,693 4-->6 Gyr=151,619

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IC 719 kinematics -Velocity field

1'x1'

Secondary component Main stellar component Ionized gas

1'x1' Main=70%

  • f total light
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IC 719 ages and metallicities of stellar populations