Surface Brightness of Starbursts at Low and High Redshifts

Observations in the rest frame ultraviolet from various space missions are used to define the nearby starburst regions having the highest surface brightness on scales of several hundred pc. The bright limit is found to be 6x10^-16 ergs/cm^2-s-A-arcsec^2 for rest frame wavelength of 1830 A. Surface brightness in the brightest pixel is measured for 18 galaxies in the Hubble Deep Field having z > 2.2. After correcting for cosmological dimming, we find that the high redshift starbursts have intrinsic ultraviolet surface brightness that is typically four times brighter than low redshift starbursts. It is not possible to conclude whether this difference is caused by decreased dust obscuration in the high redshift starburst regions or by intrinsically more intense star formation. Surface brightness enhancement of starburst regions may be the primary factor for explaining the observed increase with redshift of the ultraviolet luminosity arising from star formation.
accepted for publication in AJ; 11 pages text, 3 tables, 3 figures (embedded)