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Dr Rogier A. Windhorst (Arizona State University)

Imaging Nearby Galaxies with Hubble in the mid-UV: Tools to Understand High-Redshift Galaxy Morphology - Dr Rogier A. Windhorst Colloquium

The Australia Telescope National Facility Colloquium
15:30-16:30 Wed 10 Jul 2002

ATNF Marsfield Lecture Theatre


Faint and distant galaxies observed in deep CCD images are primarily seen in
their rest-frame mid-UV (200-300 nm). One of the dramatic results with the
Hubble Space Telescope (HST) is that these distant objects resemble nearby
late-type galaxies, but are they really similar classes of objects? This is a
critical issue for understanding the process of galaxy formation. We therefore
present a systematic imaging survey with the Hubble Space Telescope/Wide Field
Planetary Camera-2 of nearby galaxies in the rest-frame mid-UV and in the red
(800 nm). The sample covers a wide range of galaxy types and inclinations.
Most objects have ground-based optical images (360-700 nm), and some have
near-IR images (1.25-2.2 micron), or far-UV images (150 nm; from ASTRO/UIT).

I will discuss the panchromatic properties of these galaxies from this ongoing
HST project. Results will be shown separately for early-type galaxies,
mid-type spirals, and for late-type, irregular, and peculiar/merging galaxies.
In conclusion, when observed in the rest-frame mid-UV, early- to mid-type
galaxies are more likely to be misclassified as later-types than late-type
galaxies are misclassified as earlier-types. The apparent change of galaxy
morphology with rest-frame wavelength can explain part, but not all of the
excess faint blue late-type galaxies seen in the deepest HST fields.

Finally, I will show what galaxies like these would look like to the Next
Generation Space Telescope (NGST), if they were observed in their restframe
UV, and if they existed as observed nearby but at redshifts z=1--15.

More information

Roopesh Ojha

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