1 of 19

1

Rapid evolution of galaxies before cluster infall

Lister Staveley-Smith (ICRAR/UWA) + WALLABY team

2 of 19

VIRGO CLUSTER

VIVA (HI) x10

(Chung+ 2009)

VERTICO (CO) x20

(Brown+ 2021)

2

3 of 19

3

Klemola 13

WALLABY J103508-283427: An ‘almost’ dark cloud: 𝛍g=27 mag/arcsec2 (O’Beirne+ 2024)

41% of cool gas is circumgalactic!

ESO 501-G075 (Reynolds+ 2021)

Diversity in ram pressure (Wang+ 2021) and structural parameters (Reynolds+ 2023) at r < 2.5r200

Galaxy pair in clusters (Kim+ 2023)

Cluster distance (Courtois+ 2023)

The Hydra Cluster

3

4 of 19

Environmental evolution

4

Antennae

ESO 137-001 (jellyfish galaxy)

Tidal interaction

Ram pressure stripping

Cortese+

4

5 of 19

Tidal + ram pressure

5

Simulation (Lucchini+ 2020)

GASS

5

6 of 19

Pre-processing: quenching outside clusters

6

‘field’ SFR

suppressed SFR

star formation rate

cluster distance

Lewis+ (2002)

6

7 of 19

Pre-processing mechanisms

  • Hierarchical group pre-processing:
    • RPS/tides in precursor groups
  • Nature v nurture:
    • Galaxies form differently in different environments
  • Overshoot:
    • non-radial ‘grazing’ orbits
  • Cluster tides:
    • Suppression of merging
  • IGM ram pressure:
    • IGM gas content and peculiar velocities can be high in filaments and at up to ~10 r200

7

7

8 of 19

8

ESO/L.Calçada

small galaxies

small groups

large groups

cluster of galaxies

Hierarchical growth

8

9 of 19

Pre-processing mechanisms

  • Hierarchical group pre-processing:
    • RPS/tides in precursor groups
  • Nature v nurture:
    • Galaxies form differently in different environments
  • Overshoot:
    • non-radial ‘grazing’ orbits
  • Cluster tides:
    • Suppression of merging
  • IGM ram pressure:
    • IGM gas content and peculiar velocities can be high in filaments and at up to ~10 r200

9

9

10 of 19

10

WALLABY 123424+062511

10

11 of 19

WALLABY 123424+062511

11

11

12 of 19

12

WALLABY 123424+062511

12

13 of 19

13

NGC 4532

DDO 137

ALFALFA HI

contours

ROSAT image

WALLABY PDR1

contours on Legacy DR9

14 of 19

14

NGC 4532

DDO 137

ALFALFA HI

contours

ROSAT image

ALFALFA contours

on WALLABY image

Koopman+ (2008)

15 of 19

15

NGC 4532

DDO 137

S-Smith+ (2025)

ALFALFA HI

contours

ROSAT image

ALFALFA contours

on WALLABY image

HI tail originally

Discovered by Hoffmann+ (1992)

16 of 19

16

NGC 4532

DDO 137

S-Smith+ (2025)

ALFALFA HI

contours

Virgo cluster

(ROSAT X-ray)

17 of 19

Ratio of gravitational to ram pressure

17

Virgo

M49

NGC 4532/DDO 137

Earth

ICM

1.2x10-5 cm-3

880 km s-1

17

18 of 19

18

500 kpc

FEASTS + MeerKAT HI study in progress (Kale Boyes+ in prep)

QSO SDSSJ123235.82+060310.0

Tololo 1232+052

18

19 of 19

Summary

  • WALLABY HI images and kinematics are a new tool for exploring galaxy interactions and evolution in different environments in the local Universe.
  • WALLABY 123424+062511 (aka NGC 4532/DDO 137), at the edge of the Virgo Cluster (3r200) is a good example; also an analogue of the Magellanic Stream.
  • Cluster tides, galaxy tides and ram pressure all important even outside the virial radius in Virgo (and Hydra) clusters.
  • Evidence for the formation of ‘almost dark’ clouds, tidal dwarfs and ultra diffuse galaxies.
  • NGC 4532 HI tail must be clumpy: sightline of QSO SDSS J123235.82+ 060310.0 shows no HI or metal lines.
  • Great synergies between ASKAP WALLABY and FAST (FEASTS, CRAFTS, FASHI) for equatorial fields.

19

WALLABY PDR1 data

19