Events at Physics |
Events on Thursday, August 21st, 2008
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- The quest for missing baryons through X-ray spectroscopy
- Time: 4:00 pm
- Place: 4274 Chamberlin
- Speaker: Yoh Takei, ISAS in Tokyo
- Abstract: Recent cosmic microwave background observations determined that 96 percent of the Universe is "dark" (dark energy and dark matter). Baryons account for only 4 percent of the Universe. However about a half of the baryons still remain to be observed. These are the "missing baryons". Since baryons are rather familiar and even exciting -- stars, galaxies, planets and creatures are all baryons -- it is a shame that we don't understand a large part of them. Simulations of the cosmic large scale structure formation predict that the missing baryons exist as intergalactic gas with a temperature of about one million K, the so-called warm-hot intergalactic medium (WHIM). If the WHIM exists, the highly ionized metals (O, Ne, etc) in the WHIM produce emission and/or absorption lines in the X-ray energy range. The limited sensitivity of the detectors, however, makes WHIM still undetected. We have been searching cluster vicinities for the evidence of the WHIM, where the existence of relatively denser and hotter WHIM is expected, through X-ray spectroscopy (more particularly, O and Ne emission/absorption features). Despite some early positive reports, evidence for the WHIM has not yet been obtained. But the upper limits of the signals we have from recent observations indicate that our sensitivity is reaching the expected signal level. I present the details of our study, mainly those from Suzaku (Japanese X-ray satellite), and then show the future prospects of this field.
- Host: Dan McCammon