STAR-FORMATION IN BAR ENVIRONMENTS .1. MORPHOLOGY, STAR-FORMATION RATES AND GENERAL-PROPERTIES

A study of the morphological properties and star formation rates (SFRs ) of H II regions located along the bars of a sample of eleven late-ty pe barred systems is presented and compared with numerical simulations . According to the relative intensity of star formation along the bar with respect to that of the nuclear region, three types of distributio ns are observed. They may be related to the age of the bar. Other impo rtant characteristics include angular misalignments (up to 15 degrees) between the stellar bar and the ''H alpha bar'', a correlation betwee n the location of the H II regions and dust lanes in certain bars (mos tly early-type spirals), and a difference in axial ratio and length be tween stellar and H alpha bars. A wide range of SFRs (from 0.03 to 1.4 4 M. yr(-1)) is observed, and star formation is generally highly asymm etric with respect to the bar minor axis. All these features can be re produced in numerical models provided that the global mechanical energ y release remains low (but non-zero). In NGC 7479, the total gas-to-st ar transformation efficiency inside the bar is estimated at about 0.26 , meaning that, at present, maybe as nearly as 75% of the gas flowing into the bar region is not transformed into stars.