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“The Iceberg Beneath the Waves: Probing the Role of Intergalactic Gases and Galaxy-Environment Interactions in Galaxy Evolution” Dr. Todd Tripp University of Massachusetts |
| Cold dark matter (CDM) cosmology has successfully explained a number of fundamental aspects of the universe (e.g., the cosmic microwave background and nucleosynthesis of light elements). However, our understanding of galaxy formation and evolution, within the context of this cosmology, is riddled with problems. To solve many of these problems, theorists argue that galaxies interact with their environments in a variety of complex ways. For example, theorists appeal to "feedback" (energy and matter outflows driven by supernova explosions or active galactic nuclei) to shut down star formation in low-mass galaxies and thereby explain the observed paucity of small galaxies compared to CDM predictions. Unfortunately, theoretical work on galaxy-environment interactions has greatly outpaced observational verification, simply because most of the matter in galaxies and the intergalactic medium (IGM) is very challenging to observe with currently available techniques. Indeed, most of the quantity of baryonic matter predicted by CDM theory has yet to be observed in the nearby universe, the so-called "missing-baryons problem". Quasar-absorption lines provide a unique and sensitive observational probe of gases/plasmas within galaxies and their surrounding intergalactic regions. This talk will review an on-going program to study galaxy-IGM interactions using QSO absorption lines observed with the Hubble Space Telescope. A summary of a recent statistical study of the "warm-hot" IGM in the nearby universe, and its implications for the missing-baryons problem, will be presented. In addition, several observations of specific ways that galaxies and the IGM interact will be reviewed, and the talk will close with some (semi-political) remarks on the future of this technique. |