A MULTITRANSITION CO STUDY OF GL-490

The environment of the young stellar object GL 490 has been studied us ing submillimeter emission lines of CO and fundamental vibrational ban d absorption lines of CO. High spatial resolution observations were ma de in the emission lines of CO J = 3-2, (CO)-C-13 J = 3-2, and CO J = 6-5. A high spectral resolution (lambda/Delta lambda = 43,000) M-band (4.7 mu m) spectrum of GL 490 was obtained and shows fundamental vibra tional band lines of CO and (CO)-C-13 from a range of rotational state s. CO J = 3-2 maps reveal numerous moving clumps with outflow speeds f rom a few km s(-1) to 40 km s(-1). The CO J = 3-2 emission, combined w ith (CO)-C-13 J = 3-2 and CO J = 2-1 emission, shows that the outflowi ng gas has temperatures from 10 K to 30 K. The CO J = 6-5 emission dem onstrates that the clumps also contain hotter gas, with excitation tem peratures from 30 K to 100 K. A range of temperatures is consistent wi th the presence of shocks. The masses of the dumps range from 0.01 to 0.5 M.. The absence of alignment of the clumps argues against their ej ection from the central object as interstellar ''bullets.'' The range of speeds of the outflowing gas is consistent with a wind-driven outfl ow, in which a fast stellar wind sweeps up a shelf of ambient gas. The clumps would represent shell fragments. The acceleration of preexisti ng clumps of ambient gas by the ram pressure of a fast wind can also p roduce the moving clumps. The CO lines in the absorption spectrum show a strong absorption component blueshifted by 13 km s(-1) with respect to the ambient cloud. The absence of an enhancement in CO J = 3-2 emi ssion at the same velocity suggests that the blueshifted absorbing gas fills only a small fraction of the 15'' beam. The (CO)-C-13 infrared absorption lines show that the quiescent gas in the line of sight to G L 490 contains two temperature components, T = 24 K and T = 107 K, wit h (CO)-C-13 column densities N-24K = 5.6 x 10(16) cm(-2) and N-107K = 6.9 x 10(16) cm(-2). The 24 K gas is the expected cold gas in the mole cular cloud. The 107 K gas is evidence for the existence of a ''hot co re'' about GL 490. Hot gas is also shown by the CO J = 6-5 emission. T he decrease in CO J = 6-5 intensity with distance from GL 490 is used to obtain a diameter for the hot core of 12,000 AU. The fact that the CO J = 6-5 intensity peaks at GL 490 suggests that GL 490 itself, rath er than external ultraviolet radiation, is the source of heating for t he 107 K gas.