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

1. Department of Physics, University of Queensland, Brisbane, Queensland 4072, Australia.2. WFAU, Institute for Astronomy, Royal Observatory, Blackford Hill Edinburgh, EH9 3HJ, UK

3. ATNF, PO Box 76 Epping NSW 1710 Australia* Email: mtdoyle@physics.uq.edu.au

References

1. Meyer et al., MNRAS, 350,1210 (HICAT)2. Zwaan et al., MNRAS, 350, 1195 (HICAT)3. Doyle et al., in preparation (HOPCAT)4. Stavely-Smith et al (2001) Stavely-Smith, Lister, 2001, MNRAS, 322,

http://www.atnf.csiro.au/research/multibeam/5. Hambly et al, 2001, MNRAS, 326,1279-1294,1295-1314,1315-13276. Bertin E., Arnouts S., AASS, (1996) 117, 393-4047. Wakamatsu, K., Colless M.M., Jarrett T., Parker Q., Saunders W. and Watson F., 2002,

IAU Regional Assembly, ASP Conf. Series (in press)8. Madore Barry F., Helou George, Corwin Harold G. Jr.,Schmitz Marion, Wu Xiuqiv and

Bennett Judy, 1992, ADASS I ASP Conf Series, 259. Disney, M., 1976, Nature 263,57310. Sadler E.M., Hunstead R.W., 2001, ASP, 232, 5311. Barnes et al. in preparation12. Neugebauer G., et al., 1984, ApJ, 278, L1

We have identified 84% of the 4315 HI detected sourcesWe have identified 3 possible candidates for “Dark Galaxies”

SUMMARY

ASA CONFERENCE 2004 – BRISBANE, JULY 4-8TH, 2004

DARK GALAXIES & BLANK FIELDSDisney9 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 existDark Galaxies in HIPASS

HI strongly detected but no possible optical counterpart found.

We have found 3 candidate Dark GalaxiesWill be included in follow-up ATCA high resolution observationNot previously observed by the ATCANot listed in published catalogues or literature NED8

Not high velocity clouds

Matching Process – ADRICADRIC: Matlab Program to display and select optical data for each HIPASS4 sourceVelocities 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

Input DataRadio:

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

OPTICAL COUNTERPARTS FOR HIPASS SOURCES

Results & Match CategoriesAnalysis of 4315 Radio Sources

Velocity Match 44%With published velocity

Good Guess 20%

But no published velocityVelocity Multi Match 14%

Compact group of galaxies with similar published velocityGood Guess Multi Match 6%

Compact group of galaxies no velocityNo Guess 11%

Several galaxies no velocities Blank Field 5%

No visible galaxy

Estimators of TOTAL Star Formation Rate (SFR) to be investigated:Radio Continuum

High resolution radio observationsSydney University Molonglo Sky Survey SUMSS10

Reanalysis of the raw HIPASS data11

Mid InfraredInfrared Astronomical Satellite (IRAS) mission12

Correlation of SFR with local galaxy density

WHERE TO FROM HERE?

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).

When Optical Matches Are Confused?ATCA high resolution observation are carried out where possible48 observations of “Confused Sources” completed in August 2003A further 100 ATCA high resolution observations have been applied for

ATCA HI contour map overlaying DSS image. The large galaxy is the correct optical match for the HIPASS HI detection.

THE UNIVERSITY

OF QUEENSLAND

Using the HIPASS catalogue we are investigatingEstimators of Star Formation Rates (SFR)Star Formation Efficiency (SFE)Dependence of Star Formation on local galaxy density

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

Log HIPASS Integrated Flux Vs Optical Apparent Blue Magnitude from Optical matches

Totally independent variables. Clear correlation shown.

Skyplot: Declination vs. Right Ascenition for HIPASS radio source co-ordinates.

Note the concentration of “blank fields” in the Galactic Plane

HIPASSJ0546-08; Velocity=3361; Width=103; Integrated Flux=4;

Peak Flux=0.047 HIPASSJ1638-15; Velocity=7442; Width=192; Integrated Flux=8;

Peak Flux=0.049HIPASSJ1946-48; Velocity=7745; Width=134; Integrated Flux=5;

Peak Flux=0.036

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.

3 candidate “Dark Galaxies”