A sensitive search for CO emission from faint blue galaxies at z ∼ 0.5

We have obtained sensitive upper limits on the CO J=2-1 and CO J=3-2 emission lines for five faint blue galaxies with redshifts z ∼ 0.5 using the IRAM 30 m telescope. These observations would have been able to detect the luminous infrared galaxy IRAS F10214+4724 if it were located at this redshift and unlensed. However, they are not sensitive enough to detect the prototype starburst galaxy M82 or the HII galaxy UM448 if they were located at …