Astrophysics (index)about

Balmer-break galaxy

(a galaxy emitting very little shorter than 3646 angstroms)

A Balmer-break galaxy (BBG) is a galaxy identified as star forming by the lack of radiation with wavelength shorter than 3646 angstroms, the Balmer limit, i.e., the lower limit on wavelengths in the Balmer series. It is analogous to Lyman-break galaxies and the Lyman series.

The spectral feature, known as the Balmer jump, is common in A-type star, whose presence and limited lifetime indicate recent star formation. The feature's use in identifying the galaxies is that it can be found not only by spectrography but by photometry, i.e., a specifically-chosen color index, even at high redshift, thus gives a way to find samples of past star-forming galaxies, e.g., during the peak star-formation epoch.

(galaxy type,Balmer series)