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Neutral Hydrogen in Galaxy Groups

Neutral Hydrogen in Galaxy Groups. Duncan Forbes (Swinburne) Baerbel Koribalski (ATNF) David Barnes (Melbourne) Nuria McKay (Liverpool) Carole Mundell (Liverpool) Ruth Musgrave (Swinburne). Virginia Kilborn Swinburne University of Technology. The GEMS HI survey. Aims:

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Neutral Hydrogen in Galaxy Groups

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  1. Neutral Hydrogen in Galaxy Groups Duncan Forbes (Swinburne) Baerbel Koribalski (ATNF) David Barnes (Melbourne) Nuria McKay (Liverpool) Carole Mundell (Liverpool) Ruth Musgrave (Swinburne) Virginia Kilborn Swinburne University of Technology

  2. The GEMS HI survey • Aims: • To investigate the interplay between hot and cold gas in groups • To study the evolutionary history of the groups and the part evolution plays in gas content of the groups • To study gas removal mechanisms in low-density parts of the Universe • To find new group members, and possible HI clouds

  3. The GEMS HI Survey • 17 groups surveyed in HI at Parkes using the 13 beam multibeam receiver • Field of view 5.5 x 5.5o • Velocity resolution ~1.6 km/s • Bandwidth ~2500 km/s • Spatial resolution 14.5 arcmin • Sensitivity MHI ~108-109 Msun

  4. HI Group Details • Groups in our sample: NGC 524, 720, 1332, 1400, 1566, 1792/1808, 3783, 3923, 4636, 7144, 7176, 7714, 1052, 3557, 5044, IC 1459 & Grus group. • Data reduced using the aips++ routines “livedata” and “gridzilla” (as with HIPASS), producing 3-D HI datacubes • Data search conducted visually by 2 people (hope to supplement this with automated search in future) • Sixteen groups searched to date: ~10% new group members / group found

  5. GEMS Groups Details

  6. The NGC 1566 Group

  7. LSBG F157-081 APMBGC157+016+068 NGC 1566 - HI Distribution

  8. The NGC 5044 Group

  9. Mckay et al. 2004, astro-ph/0405241 NGC 5044 - HI Distribution

  10. The NGC 3783 Group

  11. NGC 3783 - HI Distribution

  12. NGC 1792/1808 Group

  13. NGC1792/1808 HI distribution

  14. HI deficiency in group galaxies? • Several studies have indicated HI deficiencies in cluster galaxies and compact groups (eg Solanes et al. 2001, ApJ 548, 97; Verdes-Montenegro et al. 2001, A&A 377, 812) • Would like to see if this extends to loose groups • What is the mechanism - can RAM pressure stripping work in a low IGM environment or are interactions more important? • Firstly - need to determine expected HI mass for a galaxy of given optical morphology • Morphology, combined with optical diameter good indicator (eg: Solanes et al. 1996, ApJ 461, 609; Haynes & Giovanelli 1984, AJ 89, 758)

  15. Expected HI content of late-type galaxies • Used the HIPASS Bright Galaxy Catalogue (BGC; Koribalski et al. 2004, AJ, 128, 16) - HI selected galaxies • Divided the ~800 late-type galaxies into optical morphological type • Fit linear regression to relationship between optical diameter and HI mass for each morphology • Use these fit lines to determine expected HI mass (with upper and lower limits) for the group galaxies to determine whether they have a typical HI content

  16. NGC 1792/1808 NGC 1566 NGC 5044 HI content of group galaxies

  17. NGC 1566 Group NGC 1566 & NGC 5044 HI Content and Deficiency NGC 1566 group No overall HI deficiency for the NGC 1566 group + Why do these galaxies contain less HI than expected? - Previous gravitational interactions? - Ram pressure stripping from IGM? + Need higher resolution observations to study the HI distribution of these galaxies. + Expect to find more examples of HI deficiency in the other 13 groups However, two group members display deficiencies - NGC 1515 (12) & NGC 1536 (2) NGC 5044 group - one late-type with HI deficiency, ESO 576-G 017 (9)

  18. Summary -17 Groups observed for the GEMS HI survey -Find ~10% new group members - thus providing a more complete view of the groups -Found a number of ‘new’ dwarf galaxies, and some possible HI clouds -No systematic HI deficiency seen in the late-type members of the groups, although several examples of individual galaxies being deficient -HI deficient galaxies not found in the centre of the groups where the intra-group x-ray emission is (eg n5044) -What is the history of these galaxies? Need to find more examples to complete the picture.

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