Star Formation & the Morphology-Density Relation in the Local Universe

1. Star Formation & the Morphology-Density Relation in the Local Universe Marianne T. Doyle Ph.D. Project

2. 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 Project’s 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

3. Spiral Galaxy Elliptical Galaxy Galaxy cluster in Hercules Abell 2151 650 million light year across Centaurus A Irregular galaxy 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

4. 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.

5. 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

6. 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

7. HIPASS position error 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

8. ADRIC Interactive Program written by David Rohde Visually matching: M. Drinkwater,D. Rohde, D. Parmenter & Myself Selection parameters Original HICAT parameters 15 x 15 arcmin images to allow for the 6 arcmin position error Centred on HICAT positions Superimposed ellipses Yellow for correct match Superimposed and listed Published velocities

9. Results Analysis of 4315 Radio Sources - 84% identified Velocity Match44%1882 • With published velocity • Good Guesses20% 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

10. Optical Matching Conclusions • ٠Optical Catalogue 1882 (44 %) identified • × “Confused” Sources 2217 (51%) • High resolution radio observations needed • + 216 (5%)Blank Fields • 19 non-galactic plane blank fields

11. 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.

12. Australia Telescope Compact Array • HI rest λ 21cm detectable by radio • 4.4 km baseline • 2.5 arcmin beam • High resolution sky coverage Radio Telescope Resolution • Parkes Radio Telescope • HI rest λ 21cm detectable by radio • 64 metre dish • 15 arcmin beam • Large sky coverage

13. Correct match: HI contouring centred on large galaxy HI contours Possible galaxies High Resolution Radio Observation Large galaxy: NGC1532 Small interacting galaxy:NGC1531

14. Calculate SFE & relate to galaxy morphology Use Infrared & Radio Continumn to measure SFR Determine which theory contributes toward the Morphology-density relation Determine local galaxy density Continuing Path To The Answer Optical matching process Completed HOPCAT

15. 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