Hess, Cluver et al. 2017 Chynoweth et al. 2008 Michel-Dansac et al. 2010 CLOSING IN ON THE DR MICHELLE CLUVER ARC FUTURE FELLOW HI-DDEN UNIVERSE mcluver@swin.edu.au Collaborators: Dr Lourdes Verdes-Montenegro (IAA, Spain), Dr Kelly Hess (Kapteyn Institute/ASTRON)
Discovery and exploration are such an important part of science
it can be challenging… Ade et al. (2014) Bowman et al. (2018)
THE SEARCH FOR DARK MATTER: THE WAITING GAME AHG Peter (2012) Hoh, Komaragiri, Abdullah (2016)
THE SEARCH FOR DARK MATTER: THE WAITING GAME AHG Peter (2012) Hoh, Komaragiri, Abdullah (2016) How will this change the landscape of our science?
Ofer Lahav
“I FIND IT INTERESTING THAT NATURE IS MORE IMAGINATIVE THAN ASTRONOMERS” Ofer Lahav
“I FIND IT INTERESTING THAT NATURE IS MORE IMAGINATIVE THAN ASTRONOMERS” Ofer Lahav TBT: finding snowballs in hell
A Spitzer study of the Shock in Stephan’s Quintet Optical (CFHT/Coelum) + Radio continuum (Allen, 1970) shows the X-ray (NASA/CXC/CfA/E.O’Sullivan) outline of the shock (from Cluver et al. 2010)
Intruder galaxy colliding at ~900 km/s Widespread excited H 2 detected within the group Cluver et al. (2010)
Warm Molecular Hydrogen Emission • Mid-IR emission from pure rotational H 2 is a direct • detection of H 2 —> associated with starbursts, (U)LIRGs, AGN Transitions: H 2 0-0 S(0), S(1) – 28.22µm, 17.03µm (traces “coolest” warm H 2 ) H 2 0-0 S(2) – S(5) – 12.28µm, 9.67µm, 8.03µm, 6.91µm ortho to para ratio ~ 3
The projected co-existence of energetic X-rays (10 5 <T<10 6 K) and warm H 2 (10 2 <T<10 3 K) The warm H 2 emission is more than three times more powerful than the X-ray emission
Powerful Cooling Pathway
Tidal HI Debris has been transformed into molecular hydrogen HI from VLA (courtesy of L. Verdes-Montenegro)
Multiphase Media
Multiphase Media Image Credit: Robert Hurt and Michelle Cluver (SSC/Caltech)
Multiphase Medium • High-speed collision with a multi-phase medium creates multiple shocks (speeds) • Low density HI --> hot plasma (X-rays) • Denser clumps of HI --> fragment and form H 2 • Slow MHD shocks (5-20km/s) excite H 2 (Guillard et al. 2009) • Clouds of H 2 are heated by turbulence in the hot gas i.e. kinetic energy of shock fuels H 2 emission • Molecular gas is continuously excited by supersonic turbulence •
How extreme is this? HI from VLA (courtesy of L. Verdes-Montenegro)
C OMPACT G ROUPS O F G ALAXIES WHY ARE THEY KEY LABORATORIES?
C OMPACT G ROUPS O F G ALAXIES WHY ARE THEY KEY LABORATORIES? • HI deficiency of groups similar to Virgo or Coma clusters — Single dish analysis of 72 Hickson Compact Groups (Verdes- Montenegro et al 2001)
C OMPACT G ROUPS O F G ALAXIES WHY ARE THEY KEY LABORATORIES? • HI deficiency of groups similar to Virgo or Coma clusters — Single dish analysis of 72 Hickson Compact Groups (Verdes- Montenegro et al 2001) • negligible ram-pressure stripping (insufficient hot, tenuous medium / not in hydrostatic equilibrium) — Rasmussen et al. (2008), Desjardins et al. (2013), tidal interactions dominate
C OMPACT G ROUPS O F G ALAXIES WHY ARE THEY KEY LABORATORIES? • HI deficiency of groups similar to Virgo or Coma clusters — Single dish analysis of 72 Hickson Compact Groups (Verdes- Montenegro et al 2001) • negligible ram-pressure stripping (insufficient hot, tenuous medium / not in hydrostatic equilibrium) — Rasmussen et al. (2008), Desjardins et al. (2013), tidal interactions dominate • accelerated evolution — bimodality in mid-infrared galaxy colours (Johnson et al. 2007, Walker et al. 2010, 2012, Zucker et al. 2016)
C OMPACT G ROUPS O F G ALAXIES WHY ARE THEY KEY LABORATORIES? • HI deficiency of groups similar to Virgo or Coma clusters — Single dish analysis of 72 Hickson Compact Groups (Verdes- Montenegro et al 2001) • negligible ram-pressure stripping (insufficient hot, tenuous medium / not in hydrostatic equilibrium) — Rasmussen et al. (2008), Desjardins et al. (2013), tidal interactions dominate • accelerated evolution — bimodality in mid-infrared galaxy colours (Johnson et al. 2007, Walker et al. 2010, 2012, Zucker et al. 2016) • shock excitation (collisions) linked to accelerated evolution of molecular hydrogen in 14/74 galaxies in 23 groups — Spitzer mid- infrared spectroscopy (Cluver et al. 2013)
C OMPACT G ROUPS O F G ALAXIES VLA study of 16 Hickson Compact Groups (Verdes-Montenegro et al 2001) Phase 1: Most gas Phase 2: Gas in Phase 3. No HI in the in galaxies tidal features galaxies Proposed evolutionary model: Amount of detected HI decreases further with evolution, by continuous tidal stripping —> supposed to turn up as X-rays
C OMPACT G ROUPS O F G ALAXIES Green Bank Telescope: HI observations of 22 HCGs ‣ HI deficiency reduced but not completely eliminated ‣ A diffuse HI component missed by the VLA • Spread over > 1000 km/s • Increasing with evolutionary stage • HI filling factor bimodal: suggests rapid transition from HSB to LSB (Borthakur, Yun & Verdes-Montenegro et al 2010)
C OMPACT G ROUPS O F G ALAXIES Green Bank Telescope: HI observations of 22 HCGs ‣ HI deficiency reduced but not completely eliminated ‣ A diffuse HI component missed by the VLA • Spread over > 1000 km/s • Increasing with evolutionary stage • HI filling factor bimodal: suggests rapid transition from HSB to LSB (Borthakur, Yun & Verdes-Montenegro et al 2010)
C OMPACT G ROUPS O F G ALAXIES Green Bank Telescope: HI observations of 22 HCGs ‣ HI deficiency reduced but not completely eliminated ‣ A diffuse HI component missed by the VLA GBT VLA • Gas dynamically similar to the one mapped with the VLA • More consistent with tidal stripping than with ram-pressure (Borthakur, Yun & Verdes-Montenegro et al 2010)
C OMPACT G ROUPS O F G ALAXIES Green Bank Telescope: HI observations of 22 HCGs ‣ HI deficiency reduced but not completely eliminated ‣ A diffuse HI component missed by the VLA GBT VLA • Gas dynamically similar to the one mapped with the VLA • More consistent with tidal stripping than with ram-pressure (Borthakur, Yun & Verdes-Montenegro et al 2010)
KAT-7: A PATHFINDER PATHFINDER
KAT-7 7 x 12m dishes Field of View: 1.08° Spatial Resolution: 3.5 ′ Pathfinder for MeerKAT Image credit: SKA-SA
Pilot on KAT-7: HCG 44 (P .I. Cluver) Serra et al. (2013) using WSRT Also: GBT observations (Borthakur et al. 2010, 2015)
achieved sensitivity: N HI < 2 × 10 18 cm -2 Hess, Cluver et al. (2017)
KAT-7 ONLY: LOWEST CONTOUR IS ~ 2 × 10 18 CM -2 extended tail: KAT-7 recovers as much emission as Arecibo (ALFALFA) ~450 kpc, 1.1 × 10 9 M ⦿
Why is this interesting?
Why is this interesting? According to photoionization and radiative transfer models HI should evaporate at column densities of <5 × 10 19 cm − 2 (Dove & Shull 1994) due to the lack of self-shielding against extragalactic ionizing photons
Why is this interesting? According to photoionization and radiative transfer models HI should evaporate at column densities of <5 × 10 19 cm − 2 (Dove & Shull 1994) due to the lack of self-shielding against extragalactic ionizing photons But, neutral HI detected below 2 × 10 18 cm -2
Why is this interesting? According to photoionization and radiative transfer models HI should evaporate at column densities of <5 × 10 19 cm − 2 (Dove & Shull 1994) due to the lack of self-shielding against extragalactic ionizing photons But, neutral HI detected below 2 × 10 18 cm -2 Proposed evolution of the group suggests neutral gas has survived at least 0.5-1 Gyr without being ionised (mass loss? lack of hot, dense IGM and associated ram pressure stripping?)
ARECIBO DIGITAL SS
ARECIBO DIGITAL SS
NGC 3162 ARECIBO DIGITAL SS
SIMILAR BEHAVIOUR SEEN IN LOOSE GROUP IC 1459
IC 1459 ASKAP-6 (Serra et al. 2015) KAT-7 (Osterloo et al. 2018)
IC 1459 ASKAP-6 (Serra et al. 2015) KAT-7 (Osterloo et al. 2018)
VLA D+CnB vs KAT-7 lowest contour: lowest contour: 1.2 x 10 19 cm -2 5 x 10 18 cm -2
Osterloo et al. (2018)
Osterloo et al. (2018) ~500 kpc tail ≃ 3 × 10 9 M ⦿ — morphology reminiscent of the Magellanic stream
Osterloo et al. (2018) ~500 kpc tail ≃ 3 × 10 9 M ⦿ — morphology reminiscent of the Magellanic stream age of the HI tail must be at least of order ≃ 2 Gyr
Osterloo et al. (2018) ~500 kpc tail ≃ 3 × 10 9 M ⦿ — morphology reminiscent of the Magellanic stream age of the HI tail must be at least of order ≃ 2 Gyr order of magnitude larger than the estimated ages of the HI tails seen in the Virgo cluster (Oosterloo & van Gorkom 2005)
Osterloo et al. (2018) ~500 kpc tail ≃ 3 × 10 9 M ⦿ — morphology reminiscent of the Magellanic stream age of the HI tail must be at least of order ≃ 2 Gyr order of magnitude larger than the estimated ages of the HI tails seen in the Virgo cluster (Oosterloo & van Gorkom 2005) reduced role for the intragroup medium in evaporating cold intragroup gas
ALSO NEARBY GALAXIES?
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