Bright & Dark Galaxies from the HIPASS Radio Survey

1. SUMMARY • We have identified 84% of the 4315 HI detected sources • We have identified 3 possible candidates for “Dark Galaxies” Screen shot of the ADRIC program showing 15’ SuperCOSMOS field centred on a HIPASS source, with published velocities in red, blue ellipses from SExtractor catalogue (selected galaxy in yellow). The buttons classify the selected optical counterpart (allowing cases of poor photometry due to merged objects or poor image segmentation to be noted). Skyplot: Declination vs. Right Ascenition for HIPASS radio source co-ordinates. Note the concentration of “blank fields” in the Galactic Plane Log HIPASS Integrated Flux Vs Optical Apparent Blue Magnitude from Optical matches Totally independent variables. Clear correlation shown. ATCA HI contour map overlaying DSS image. The large galaxy is the correct optical match for the HIPASS HI detection. 3 candidate “Dark Galaxies” • Log Integrated Radio flux vs. App. Blue Magnitudes • 3 candidate “Dark Galaxies” compared to optical counterparts for HIPASS4 galaxies. These objects are very different from the optically matched galaxies. • Their flux puts them outside the range for the optical matches objects • The apparent blue magnitude limits for the matched galaxies and SuperCOSMO5 images are 18 & 22 respectively, hence the blue magnitude for these objects may be <22. HIPASSJ0546-08; Velocity=3361; Width=103; Integrated Flux=4; Peak Flux=0.047 HIPASSJ1638-15; Velocity=7442; Width=192; Integrated Flux=8; Peak Flux=0.049 HIPASSJ1946-48; Velocity=7745; Width=134; Integrated Flux=5; Peak Flux=0.036 WHERE TO FROM HERE? • Estimators of TOTAL Star Formation Rate (SFR) to be investigated: • Radio Continuum • High resolution radio observations • Sydney University Molonglo Sky SurveySUMSS10 • Reanalysis of the raw HIPASS data11 • Mid Infrared • Infrared Astronomical Satellite (IRAS) mission12 • Correlation of SFR with local galaxy density THE UNIVERSITY OF QUEENSLAND • Bright & Dark Galaxies • from the HIPASS Radio Survey • Marianne T. Doyle*1, Michael J. Drinkwater1, David J. Rohde1, Mike Read2, • Baerbel S Koribalski3 and The HIPASS Team • Department of Physics, University of Queensland, Brisbane, Queensland 4072, Australia. • WFAU, Institute for Astronomy, Royal Observatory, Blackford Hill Edinburgh, EH9 3HJ, UK • ATNF, PO Box 76 Epping NSW 1710 Australia • * Email: mtdoyle@physics.uq.edu.au • We have searched for optical counterparts for the 4315 HI Parkes All-Sky 21cm Survey (HIPASS4) detections • We used images from the SuperCOSMOS optical southern sky survey5 • Using the HIPASS catalogue we are investigating • Estimators of Star Formation Rates (SFR) • Star Formation Efficiency (SFE) • Dependence of Star Formation on local galaxy density OPTICAL COUNTERPARTS FOR HIPASS SOURCES • Input Data • Radio: • HIPASS catalogue 1,2 - 4315 neutral hydrogen (HI) detected sources • Optical: • SuperCOSMOS5: Optical images • SExtractor6: image analysis with BRI photometry • 6dF Galaxy Survey7: velocity matching • NED Database8: velocity matching • Matching Process – ADRIC • ADRIC: Matlab Program to display and select optical data for each HIPASS4 source • Velocities from NED8 and the 6dF Galaxy Survey7 used to match the HIPASS radio sources velocities to confirm optical matches • When no velocities were available proximity to the HIPASS co-ordinates and other image features were used to assist optical matching Results & Match Categories • Analysis of 4315 Radio Sources • Velocity Match44% With published velocity • Good Guess20% But no published velocity • Velocity Multi Match14% Compact group of galaxies with similar published velocity • Good Guess Multi Match6% Compact group of galaxies no velocity • No Guess 11% Several galaxies no velocities • Blank Field5% No visible galaxy • When Optical Matches Are Confused? • ATCA high resolution observation are carried out where possible • 48 observations of “Confused Sources” completed in August 2003 • A further 100 ATCA high resolution observations have been applied for DARK GALAXIES & BLANK FIELDS • Disney9 hypothesised that the baryonic content of the universe might be in low surface brightness galaxies know as “Dark Galaxies” • HIPASS being a HI All-sky southern survey should find “Dark Galaxies” if they exist • Dark Galaxies in HIPASS • HI strongly detected but no possible optical counterpart found. • We have found 3 candidate Dark Galaxies • Will be included in follow-up ATCA high resolution observation • Not previously observed by the ATCA • Not listed in published catalogues or literature NED8 • Not high velocity clouds References • Meyer et al., MNRAS, 350,1210 (HICAT) • Zwaan et al., MNRAS, 350, 1195 (HICAT) • Doyle et al., in preparation (HOPCAT) • Stavely-Smith et al (2001) Stavely-Smith, Lister, 2001, MNRAS, 322, http://www.atnf.csiro.au/research/multibeam/ • Hambly et al, 2001, MNRAS, 326,1279-1294,1295-1314,1315-1327 • Bertin E., Arnouts S., AASS, (1996) 117, 393-404 • Wakamatsu, K., Colless M.M., Jarrett T., Parker Q., Saunders W. and Watson F., 2002, IAU Regional Assembly, ASP Conf. Series (in press) • Madore Barry F., Helou George, Corwin Harold G. Jr.,Schmitz Marion, Wu Xiuqiv and Bennett Judy, 1992, ADASS I ASP Conf Series, 25 • Disney, M., 1976, Nature 263,573 • Sadler E.M., Hunstead R.W., 2001, ASP, 232, 53 • Barnes et al. in preparation • Neugebauer G., et al., 1984, ApJ, 278, L1 ASA CONFERENCE 2004 – BRISBANE, JULY 4-8TH, 2004