Clusters In the Zone of Avoidance


Clusters of galaxies behind the Galactic plane from ROSAT All-Sky Survey data:

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Clusters In the Zone of Avoidance



The CIZA team:

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Project overview:

The CIZA project (Clusters In the Zone of Avoidance) is the first systematic X-ray search for clusters of galaxies behind the Milky Way. CIZA uses a combined X-ray/optical/NIR approach to identify clusters of galaxies at |b| < 20 deg, i.e., in a region of the sky that has traditionally been excluded from earlier cluster catalogues because of massive obscuration and extinction problems. So far, CIZA has identified and spectroscopically confirmed 101 galaxy clusters in what used to be the zone of avoidance; 74 (73%) of these are new discoveries. An additional 10 clusters have been confirmed in imaging observations and await spectroscopic observation.

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The sample:

The following figure shows the column density of neutral Hydrogen in the Galactic plane region. Regions of very high nH close to the Galactic center are impenetrable even to X-rays. At moderate Galactic latitude, however, and in the direction of the Galactic anticenter X-ray vision allows us to effectively look through the Milky Way in search of extragalactic objects such as clusters of galaxies.

click to see larger image plus CIZA sample

Weather permitting we shall finish the compilation of a statistically complete subset of the X-ray brightest CIZA clusters by mid 2001. We intend to publish the resulting subsample before the end of the year.

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CIZA publications (by the CIZA team):

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(page last updated by H. Ebeling, January 4, 2001)