Star Formation

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Star Formation the Morphology-Density Relation
in the Local Universe

• Marianne T. Doyle
• Ph.D. Project

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Content
Supervisor Michael J. Drinkwater UQ Assoc
Supervisors John Ross - UQ Elaine Sadler Uni
Sydney Collaborators David J. Rohde - UQ Mike
Read WFAU Edinburgh Baerbel S Koribalski
ATNF, Epping 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.......

• The Morphology-density relation
• This Projects Question How does star formation
  depend upon environment and other factors?
• Proposed theories
• Progress
• The Radio Detected Galaxy Sample
• Optical Matches for Radio Detections
• High resolution Radio observations
• The continuing path to the answer

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Morphology, Density The Relationship

• Morphology?
• Galaxy types Irregular, Spiral and elliptical
  galaxies and everything in between.
• Galaxy Density?
• Alone?
• Is the galaxy in a group?
• In a cluster?
• The Morphology-Density Relation?
• The observation that there are few spiral
  galaxies in areas of high galaxy density.

Hickson Compact Group HCG87 170,000 light year
across
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This Project

• The question How does the conversion of hydrogen
  to stars (star formation) depend upon environment
  and other factors?
• Testing two theories
• Either fewer star forming galaxies actually
  form in regions of high galaxy density,
• OR
• There are physical processes that directly
  suppresses star formation.

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This Project

• Use radio detected galaxy sample instead of
  optical sample
• Optical samples are biased towards star forming
  galaxies which is what we are trying to measure.
• Measure the Star Formation Rate (SFR)
• The rate stars are forming in galaxies
• Calculated using luminosity of galaxy
• Determine the Star Formation Efficiency (SFE)
• A ratio of SFR and mass of neutral hydrogen (HI)
  in the galaxy
• Estimate the local galaxy density

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The Radio Galaxy Sample

• Neutral hydrogen (HI) is
• The fuel for star formation
• Has a rest wavelength of 21cm, detectable by
  radio
• HI Parkes Sky Survey (HIPASS) (Stavely-Smith et
  al 2001)
• HI blind radio survey of the southern sky
• HIPASS Catalogue (HICAT) (Meyer et al submitted)
• Very large survey containing 4315 HI radio
  sources
• Previous HI surveys have numbered in the hundreds
  (Braun et al 2003 Lee et al 2003)
• Position error of 6arcmins
• Accurate galaxy positions needed to measure
  luminosity to estimate SFR
• Optically match all 4315 HI radio detections for
  accurate positions

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Optical Counterparts

• Objective Find the optical counterparts for the
  HI radio sources
• Problem Um.. Which galaxy was the original HI
  detection?
• Need an interactive program to visually match
  radio sources to their optical counterparts

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• ADRIC Interactive Program written by David Rohde
• Visually matching M. Drinkwater, D. Rohde, D.
  Parmenter Myself

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Results Analysis of 4315 Radio Sources - 84
identified

• Velocity Match 44 1882
• With published velocity
• Good Guesses 20 851
• But no published velocity
• Velocity Multi Match 14 634
• Compact group of galaxies with published velocity
• Good Guess Multi Match 6 256
• Compact group of galaxies no velocity
• No Guess 11 476
• Several galaxies no velocities
• Blank Field 5 216
• No visible galaxy

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Optical Matching Conclusions

• ? Optical Catalogue 1882 (44 ) identified
• Confused Sources 2217 (51)
• High resolution radio observations needed
• 216 (5) Blank Fields
• 19 non-galactic plane blank fields

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Sanity Check

• Radio flux from HIPASS radio sources and Apparent
  Magnitudes from Optical matches
• Totally independent variables
• Correlation shown

(Faint to bright)
Log HIPASS Peak Flux Vs Optical Apparent
Magnitude Objects matched by published
velocities, educated guesses without velocity and
velocity matches where multiple galaxies match.
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Radio Telescope Resolution

• Parkes Radio Telescope
• HI rest ? 21cm detectable by radio
• 64 metre dish
• 15 arcmin beam
• Large sky coverage

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High Resolution Radio Observation
Large galaxy NGC1532 Small interacting
galaxyNGC1531
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Continuing Path To The Answer
Optical matching process Completed HOPCAT
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Thank you Michael Drinkwater Supervisor
extraordinaire David Rohde Computer wiz Kevin
Pimbblet The answer giver
Lagoon Nebula 100LY across Contains many young
stars hot gas
Luke Pegg Continual support wonderful
hugs Jacob Doyle My wonderful teenage son