Molecular outflow

Herbig-Haro objects are often found to be associated with molecular outflows observed in rotational lines of cosmically abundant molecules (e.g. CO, NH3) that come from regions enveloping the jet. The outflow velocity is generally much lower. The origin of these molecular outflows is not clear either they result from winds from the accretion disk or from the interaction between the jet and its surroundings. 

Spitzer Reveals a Molecular Outflow from a Low Mass Protostar... 

Fig. 2.2 Sketch of the environment of the low mass proto-star IRAS16293-2422 [23]. A binary system with sources A and B is located at the centre of a cold dense core. Sources A and B have distinct chemistries with a richer composition of organic species in sotnce A. This system is associated with two molecular outflows, in the East-west and North-East-South-West directions represented by arrows. The former outflow is compressing a second dense core to the East (core E), triggering a new generation of star formation...

In the classical view of star formation [21,26], young proto-stars are surrounded by an accretion disk, also called a circumstellar disk, which contributes to the feeding of the proto-star before it reaches its final mass. The so called class 0 proto-stars are deeply embedded and radiate mostly in the far infrared and sub-millimetre spectral range. At this stage, proto-stars are actively accreting, as testified by the presence of jets and molecular outflows. These outflows contribute to the release of energy and... 

Fig. 2.6 The molecular outflow created by the class 0 proto-star LI 157 viewed in the infrared by the Spitzer (left) and in the far infrared with Herschel (right) satellites. The Spitzer image taken with the IRAC camera is dominated by emission from the rotational lines of H2. The Herschel image taken with the PACS instrument at 179 pm, the wavelength of one of the strongest lines of water vapour (2j 2 — lo.i) shows the excellent agreement between the H2 and water vapour morphology [35]...

FIGURE 9 Spectrally Integrated CO 2-1 emission Image of a portion of the Ophiuchus star formation region. The intensity scale Is in K + km seo . Symbols identify the positions of the young stellar objects in the region, some of which possess molecular outflows. 

Andr4 P., Ward-Thompson, D., and Baisony, M. (2000). Prom Pre-Stellar Cores to Protostars The Initial Conditions of Star Eormation. In Protostars and Planets IV (V. Mannings, A. P. Boss, and S. S. Russell, eds.), in press. University of Arizona Press, Tucson, AZ. Bachiller, R. (1996). Bipolar molecular outflows from young stars and protostars, Ann. Rev. Astron. Astrophys. 34,111-154. 

DO PRE-MAIN-SEQUENCE STARS DRIVE BIPOLAR MOLECULAR OUTFLOWS ... 

Abstract. In some interpretations, the onset of a high vdodty molecular outflow signals the end of the Class I stage of pre-main-sequence stellar life and marks an evolutionary period after whidi a Class II pre-main-sequence star remains. Since all but a handful of the hundreds of known molecular outflow sources are associated with Class I sources, this interpretation appears reasonable. The handful of more evolved Class II sources that apparently drive outflows are exceptions, hi our infrared, polarimetric imaging program, we have made serendipitous discoveries that indicate the number of Class II sources that drive outflows may now be smaller by at least two than was previously thought. 

Fig. 1. Recent high resolution maps of the IRc 2 region at 3.8,12.4, and 18.7/ m. Top left Deconvolved shift-and-add 3.8 m image with a spatial resolution of 0.45" (Dougados et al. 1993). SiO maser positions as weU as molecular outflows are indicated. Top rightiDirect imaging of IRc2 at 12.4 m with a resolution of about 0.9" (Gez ud 1992). SiO and H2O maser positions as well as the position of a 22GHz continuum point source. Bottom A 3x3 mosaic at 18.7/mi and a resolution of about l" (Cameron et al. 1993). Several luminous members of the complex are labeled. The contours indicate the distribution of dense gas traced by the (3,2) inversion line of NH3 at 1.2cm (Migenes et al. 1989). are indicated.

Abstract. We present observations of the molecular outflow sources S106 and GL 2591. The IRTF Cryogenic Echelle Spectrograph (CSHELL) was used to acquire long-slit HI Br 7 and Ha S(l) 1-0 spectra with I. O spatial and 14 km sec spectral resolution. These data show the outflows to be both spatially and spectrally resolved, with distinct emissions from the YSOs and the extended flows. We interpret the kinematics and spatial variations in terms of the outflows central exciting sources and their surrounding environments. 

Molecular outflows are spectacular indicators of the earliest phases of star formation, but their physical origins are not well understood. Observational tests of outflow mechanism theories have been hampered by the relatively poor spatial resolution of radio telescopes and the relatively poor spectral resolution of infrared spectrometas. 

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