The H2CO abundance in the inner warm regions of low mass protostellar envelopes

摘要: We present a survey of the formaldehyde emission in sample eight Class 0 protostars obtained with IRAM and JCMT telescopes. The data have been analyzed three different methods increasing level sophistication. first analyze observed LTE approximation, derive rotational temperatures between 11 40 K, column densities 1 20 x 10^13 cm^-2. Second, we use LVG code larger kinetic temperatures, 30 90 consistent subthermally populated levels from to 6 10^5 cm^-3. modeling are within factor 10 respect those derived approximation. Finally, observations based upon detailed models for envelopes surrounding protostars, using temperature density profiles previously continuum observations. approximate abundance across envelope jump function, occurring when dust reaches 100 evaporation grain mantles. is well reproduced only if there jump, more than two orders magnitude, four sources. In remaining sources but evidence marginal (~2 sigma). inferred inner H2CO varies 10^-8 10^-6. discuss implications these jumps our understanding origin evolution ices low mass star forming regions. give predictions submillimeter lines, which particularly sensitive jumps.