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HI in Galaxy Groups

HI in Galaxy Groups. Duncan Forbes Baerbel Koribalski Sarah Brough David Barnes. Virginia Kilborn Swinburne University of Technology. GEMS HI Survey. Aims: To investigate the interplay between hot and cold gas in groups

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HI in Galaxy Groups

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  1. HI in Galaxy Groups Duncan Forbes Baerbel Koribalski Sarah Brough David Barnes Virginia Kilborn Swinburne University of Technology

  2. 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. HI in GEMS groups • 16 groups were observed at Parkes using the multibeam receiver - 5.5x5.5 degree fields • Groups have varying x-ray properties • 8 have intra-group X-ray emission • 6 have X-rays from central group galaxy • 2 undetected in X-rays • The 16 groups lie between 1000-3000 km/s (~13-40 Mpc) • Detection limit for HI is around 5x108 M • Number of group members varies from ~10 to >150 - very diverse range of groups

  4. HI Findings • Total Galaxies detected: 210 • Uncatalogued HI detections:14 (7 %) • New redshifts: 8 (5 %) • HI Clouds: 1 definite, 3+ candidates • Total new group members: (10 %) • Also - added in 6dFGS galaxies for further group members

  5. Groups with intra-group X-ray emission

  6. Intra-group X-rays II

  7. Intra-group X-rays III

  8. Groups with central galaxy X-ray emission

  9. Galaxy X-rays II

  10. Groups with no detected X-ray emission

  11. Lack of central HI Others LX LX and HI distribution

  12. TX and HI concentration Lack of central HI Others

  13. Spiral fraction vs Tx

  14. Group HI deficiency? Result: No HI deficiency for the NGC 1566 group • Several studies have indicated HI deficiencies in cluster galaxies and compact groups • 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 • We use both optical sample and BGC to make predictions for NGC 1566 group (spiral and late-type galaxies) Several members display Individual deficiency - NGC 1515 (12) & NGC 1536 (2) Kilborn et al. 2005

  15. Minchin et al 2005 1993 Oosterloo & van Gorkom, astro-ph/0505397 HI ‘clouds’ in groups • How common are HI clouds without visible stars in galaxy groups? • What is the formation Scenario? • interactions culminating in HI stripping • Ram pressure stripping • Primordial? • HI clouds in our GEMS groups - • One confirmed cloud in NGC 3783 group • One possible cloud in same group • Plus several candidates in the NGC 5044 group

  16. MHI = 5x109M NGC 3783 MHI = 1010M NGC 3783 Group

  17. ATCA HI map and DSSII R-band Keck B-band image Keck R-band image

  18. NGC 5044 HI cloud candidates

  19. Conclusions • New group members found in HI surveys of groups (~1-2 per galaxy group) • Some groups lack HI in central regions - correlated with TX • HI clouds - at least one in our study, several more candidates. Likely formation scenario: tidal debris

  20. Future Work • Statistical analysis of HI content of the groups • High resolution ATCA HI obs of cloud candidates • 2dF redshifts for galaxies in N3783 cloud fields • HI deficiency of group galaxies? • SFR of group galaxies

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