Galaxy Cluster Gas Creates Hole in Microwave Background
Image Credit: ALMA (ESO/NAOJ/NRAO), Kitayama et al., NASA/ESA Hubble Space Telescope
Explanation: Why would this cluster of galaxy punch a hole in the cosmic microwave background (CMB)? First, the
famous CMB was created by
cooling gas in the
early universe and flies right through most gas and dust in the universe. It is
all around us. Large
clusters of galaxies have enough gravity to contain very
hot gas -- gas hot enough to up-scatter microwave photons into light of significantly higher energy, thereby creating a hole in CMB maps. This
Sunyaev–Zel'dovich (SZ) effect has been used for decades to reveal new information about hot gas in clusters and even to help discover galaxy clusters in a simple yet uniform way.
Pictured is the most detailed image yet obtained of the
SZ effect, now using both
ALMA to measure the CMB and the
Hubble Space Telescope to measure the galaxies in the massive galaxy cluster
RX J1347.5-1145.
False-color blue depicts light from the
CMB, while almost every yellow object is a galaxy. The shape of the
SZ hole indicates not only that hot gas is present in this galaxy cluster, but also that it is distributed in a surprisingly uneven manner.
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