HST Images of Very Compact Blue Galaxies at Z approximately 0.2
Bershady, Matthew A.; Majewski, Steven R.; Koo, David C.; Stanford, S. Adam; Wirth, Gregory D.
United States
Abstract
We present the results of HST Wide-Field Camera (WFC) imaging of seven very compact, very blue galaxies with B <= 21 and redshifts z ~ 0.1 to 0.35. Based on deconvolved images, we estimate typical half-light diameters of ~0.65", corresponding to ~1.4 h^-1^ kpc at redshifts z~0.2. The average rest frame surface brightness within this diameter is μ_v_~ 20.5 mag arcsec^-2^, ~1 mag brighter than that of typical late- type blue galaxies. Ground-based spectra show strong, narrow emission lines indicating high ionization; their very blue colors suggest recent bursts of star-formation; their typical luminosities are ~4 times fainter than that of field galaxies. These characteristics suggest H II galaxies as likely local counterparts of our sample, though our most luminous targets appear to be unusually compact for their luminosities.