HOPCAT, Dark Galaxies

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HOPCAT, Dark Galaxies Star Formation

• Marianne T. Doyle
• Ph.D. Project
• University of Queensland

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Content
Marianne Doyle Ph.D Project University of
Queensland Advisor Michael J. Drinkwater
UQ Assoc. Advisors Elaine Sadler Uni
Sydney John Ross - UQ Collaborators David J.
Rohde - UQ Kevin Pimbblet - UQ Mike Read WFAU
Edinburgh HIPASS Team ATNF Parkes Epping,
Universities of Melbourne, Cardiff, Western
Sydney Macarthur, Wales, Swinburne, Technology
Sydney, New Mexico, Manchester, Colorado, Sydney,
Leicester ASTRON The Netherlands, AAO
Sydney, WIYN Tucson etc.......

• HIPASS Optical Catalogue (HOPCAT)
• HOPCAT Science
• Isolated Dark Galaxies
• Star Formation Galaxy Density
• Summary Accessing HOPCAT

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HIPASS Optical Catalogues

• HI Parkes All Sky Survey (HIPASS) Catalogue
  (HICAT)
• Largest blind HI radio survey
• of the southern sky to Dec2o
• Velocity range 300 - 12700 km/s
• 4315 HI radio detected sources
• HIPASS Optical Catalogue (HOPCAT)
• 3618 (84) optical galaxies identified
• Galaxy Choice category useful for researchers

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Visually matched by 3 people to minimise galaxy
selection bias
2 Digit optical galaxy choice - match categories
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HOPCAT Science - Isolated Dark Galaxies

• 4315 HI radio detected objects
• Dust extinction cut at ABj lt 1 mag 3692
  objects
• Blank fields (galaxy choice category 30) 13
  objects
• Take out over crowded fields 2 objects
• 2 remaining objects?
• 1 - very faint previously observed optical galaxy
  in the Centaurus group Banks et al (1999)
• 1- non-detection - Narrow-band follow-up
  observations at Parkes (Thank you Ivy Wong)
• Conclusion No isolated dark galaxies are present
  within HIPASS
• Doyle et al. (MNRAS in press astro-ph/0505591)

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HOPCAT Science Star Formation Galaxy Density

• Previous optical surveys - rapid decrease in star
  formation with increasing galaxy density (Lewis
  et al. 2002) WHY??
• Morphology-Density Relation - Testing 2 theories
• In regions of high galaxy density either
• fewer HI rich galaxies
• OR
• HI rich galaxies present but physical process is
  suppressing star formation
• Star Formation Rate
• Infrared IRAS in 12, 25, 60 100 µm
• 1045 IRAS HOPCAT matches
• Galaxy Density - Local Surface Density S10
• SuperCOSMOS Galaxy Catalogue
• S10 based on radius to 10th nearest galaxy
  neighbour

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60s 40s 50s 10s
SFR calculated from IRAS fluxes
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60s 40s 50s 10s
S10 calculated using SuperCOSMOS Galaxy Catalogue
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Interesting preliminary results but little
time! HI Mass rapidly decrease as density
increases however Star Formation efficiency
not a rapid change as density
increases.. Afternoon tea bribe required for
further discussion
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SUMMARY

• HIPASS Optical Catalogue HOPCAT
• 84 Optical Galaxies identified
• HOPCAT Science
• No isolated dark galaxies are present within
  HIPASS
• With increasing galaxy density
• Star Formation Rate decreases
• HI Mass decreases rapidly (preliminary result)
• However - Star Formation Efficiency only slight
  decrease (preliminary result)
• HOPCAT available soon at
• http//HIPASS.aus-vo.org Searchable format
• Synergy MNRAS online Complete catalogue