Molecular Outflows from Newly Formed Massive Stars

We map 6 massive young stellar objects (YSOs) in the CO J=2-1 line and survey 18 massive YSOs, including the six, in the HCO+ J=1-0, SiO J=2-1, H2O 6(16) - 5(23) maser, and CH3OH 7(0) - 6(1) A(+) maser lines. We detect CO bipolar outflows in all the six mapped sources. Four of them are newly discovered (07299-1651, 21306+5540, 22308+5812, 23133+6050), while 05490+2658 is mapped in the CO J=2-1 line for the first time. The detected outflows are much more massive and energetic than outflows from low-mass YSOs with masses >20 M-circle dot and momenta >300 M-circle dot km s(-1). They have mass outflow rates (3-6) x 10(-4) M-circle dot yr(-1), which are at least one order of magnitude greater than those observed in low-mass YSOs. We detect HCO+ and SiO line emission in 18 (100%) and 4 (22%) sources, respectively. The HCO+ spectra show high-velocity wings in 11 (61%) sources. We detect H2O maser emission in 13 (72%) sources and 44 GHz CH3OH maser emission in 8 (44%) sources. Of the detected sources, 5 H2O and 6 CH3OH maser sources are new discoveries. 20081+3122 shows high-velocity (>30 km s(-1)) H2O maser lines. We find good correlations of the bolometric luminosity of the central (proto)star with the mechanical force, mechanical luminosity, and mass outflow rate of molecular outflow in the bolometric luminosity range of 10(-1)-10(6) L-circle dot, and identified 3 intermediate- or high-mass counterparts of Class 0 objects.