Hubble Ultra-Deep Field

The Hubble Ultra-Deep Field (HUDF) is a deep-field image of a small region of space in the constellation Fornax, containing an estimated 10,000 galaxies.

The HUDF image was taken in a section of the sky with a low density of bright stars in the near-field, allowing much better viewing of dimmer, more distant objects.

This is about one-tenth of the angular diameter of a full moon viewed from Earth (less than 34 arcminutes),[3] smaller than a 1 mm2 piece of paper held 1 m away, and equal to roughly one twenty-six-millionth of the total area of the sky.

[8] On January 23, 2019, the Instituto de Astrofísica de Canarias released an even deeper version[9] of the infrared images of the Hubble Ultra Deep Field obtained with the WFC3 instrument, named the ABYSS Hubble Ultra Deep Field.

When the Advanced Camera for Surveys (ACS) detector was installed on the HST, it was realized that an ultra-deep field could observe galaxy formation out to even higher redshifts than had currently been observed, as well as providing more information about galaxy formation at intermediate redshifts (z~2).

At the workshop Massimo Stiavelli advocated an Ultra Deep Field as a way to study the objects responsible for the reionization of the Universe.

Unlike the Deep Fields, the HUDF does not lie in Hubble's Continuous Viewing Zone (CVZ).

The field is 200 arcseconds to a side, with a total area of 11 square arcminutes,[12] and lies in the constellation of Fornax.

[14] The orientation of the HST was chosen so that further NICMOS parallel images would fall on top of the main UDF field.

After the installation of WFC3 on Hubble in 2009, the HUDF09 programme (GO-11563) devoted 192 orbits to observations of three fields, including HUDF, using the newly available F105W, F125W and F160W infra-red filters (which correspond to the Y, J and H bands):[5][15] The HUDF is the deepest image of the universe ever taken and has been used to search for galaxies that existed between 400 and 800 million years after the Big Bang (redshifts between 7 and 12).

[1][obsolete source] Several galaxies in the HUDF are candidates, based on photometric redshifts, to be amongst the most distant astronomical objects.