Patricia Novais Seminário de Extragaláctica 09/06/16

Overview

Understand how the stellar counter-rotating components in the galaxy were formed, through the study of their kinematics and properties.

2

Counter-rotating discs in galaxies! 3

For a review: Corsini et al. 2014 For a review:

Corsini et al. 2014 For a review: Corsini et al. 2014 For a review:

Corsini et al. 2014 For a review: Corsini et al. 2014

For a review: Corsini et al. 2014

I.  Gas vs. stars (NGC4546)

II.  Stars vs. stars (NGC4550)

III.  Gas vs. gas (NGC7332)

Counter-rotating discs in galaxies! 4

For a review: Corsini et al. 2014 For a review:

Corsini et al. 2014 For a review: Corsini et al. 2014 For a review:

Corsini et al. 2014 For a review: Corsini et al. 2014

For a review: Corsini et al. 2014

I.  retrograde acquisition of external gas and subsequent star formation

II.  assembly of the counter-rotating stellar component from mergers

III.  or internal instabilities.

Scenarios

NGC 4191

Ø  S0 isolated galaxy at D = 42.4 Mpc Ø  Stellar velocity field reveals an irregular structure with little rotation Ø  Stellar velocity dispersion field shows two symmetric peaks Ø  VIRUS-W IFU Spectrograph Ø  Low resolution mode, 4340Å-6040Å 5

Analysis 6

I.  Kinematics

II.  Photometry

III.  Stellar Populations

Kinematics

Line-of-sight velocity distribution (LOSVD) with double peak

Clear bimodal structure

7

Photometry

▹  2D image-fitting with IMFIT: a Sérsic bulge + 2 exponential discs. ▹  Residual map: spiral-arm pattern? Faint spiral arm?

8

Photometry 9

In fact, 3 components is a good choice to describe the surface brightness radial profile.

Kinematics 10

Main V = 70 km/s σ= 120 km/s

Secondary V = 130 km/s σ= 90 km/s

Gas V = 150 km/s σ= from 60km/s to 30km/s

Stellar Populations 11

▹  Hβ, MG b, Fe5270, Fe5335 for both components: ▹  Properties very similar… ▹  Age radial profile: negative gradients.

Stellar Populations

▹  α elements and metallicity: no significant radial gradients

12

Main: Age: ~12Gyr to ~6Gyr

Secondary: Age: ~12Gyr to ~3Gyr

Gas

▹  A elongated ring-like structure (or spiral arms) with 3 blobs within 25 ▹  Similar spiral-like structure in the residual maps

13

Possible scenario

▹ 2 components: bulge and disk + disk ▹ 2nd component more faster than the 1st. ▹ Properties of stellar populations very similar ▹ α elements and metallicity: no radial significant grandients ▹ Negative age radial gradient: inside-out formation ▹ Δage(main-sec) ~ 2Gyr

14

I - Accretion scenario is better than merger scenario…

Conclusion 15

▹ Galaxy w/ 2 components rotating in opposite directions ▹  Inside-out formation for the 2nd component ▹ Accretion scenario ▹ Faint spiral-like structure

16

THANKS!