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

Marianne T. DoylePh.D. Project

Content 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

Supervisor:Michael J. Drinkwater – UQAssoc Supervisors:John Ross - UQElaine Sadler – Uni SydneyCollaborators David J. Rohde - UQMike Read – WFAU EdinburghBaerbel S Koribalski – ATNF, EppingHIPASS Team – ATNF Parkes &

Epping, Universities of : Melbourne, Cardiff, Western Sydney Macarthur, Wales, Swinburne, Technology Sydney, New Mexico, Manchester, Colorado, Sydney, LeicesterASTRON The Netherlands,AAO Sydney,WIYN Tucson etc….......

Hickson Compact Group

HCG87

170,000 light year across

Galaxy cluster in Hercules

Abell 2151

650 million light year across

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.

Spiral Galaxy

Elliptical Galaxy

Irregular galaxy

Centaurus A

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.

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

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

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

HIPASS position error

Superimposed ellipses

Yellow for correct match

15 x 15 arcmin images to allow

for the 6 arcmin position errorCentred on

HICAT positions

Selection parametersOriginal

HICAT parameters

ADRIC Interactive Program written by David Rohde

Visually matching: M. Drinkwater, D. Rohde, D. Parmenter & Myself

Superimposed and listedPublished velocities

ResultsAnalysis 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

Optical Matching Conclusions ٠ Optical

Catalogue 1882 (44 %) identified

× “Confused” Sources 2217 (51%) High

resolution radio observations needed

+ 216 (5%) Blank Fields 19 non-

galactic plane blank fields

Sanity Check

Log HIPASS Peak Flux Vs Optical Apparent MagnitudeObjects matched by published velocities, educated guesses without

velocity and velocity matches where multiple galaxies match.

Radio flux from HIPASS radio sources and Apparent Magnitudes from Optical matches Totally independent

variables Correlation shown

(Faint to bright)

Radio Telescope Resolution

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

Australia Telescope Compact Array HI rest λ 21cm detectable by radio 4.4 km baseline 2.5 arcmin beam High resolution sky coverage

HI contours

Correct match:

HI contouring centred on

large galaxy

Possible galaxies

High Resolution Radio Observation

Large galaxy: NGC1532Small interacting galaxy:NGC1531

Continuing Path To The Answer

Optical matching process

CompletedHOPCAT

Use Infrared & Radio

Continumn to measure SFR

Determine local galaxy

density

Calculate SFE &

relate to galaxy

morphology

Determine which theory contributes toward the

Morphology-density relation

Luke Pegg – Continual support & wonderful hugsJacob Doyle – My wonderful teenage son

Thank youMichael Drinkwater – Supervisor extraordinaireDavid Rohde – Computer wizKevin Pimbblet – The answer giver

Lagoon Nebula100LY across

Contains many young stars

& hot gas