Proto-star

In another photograph of hydrogen gas far out in space, small black spots can be seen. These spots are globules of hydrogen, proto-stars that are now in the process of being formed. 

It seems appropriate to conclude this short discussion of interstellar masers and star-formation with the question of the problems left open. It is clearly one of the most fascinating areas of astronomical research to study regions of star-formation and hopefully find additional tracers and criteria for the investigation of these regions. The question of the interaction between a newly born star and its parental molecular cloud is one of the most fascinating areas of future research. The study of this detailed problem has to be complemented by the conduct of unbiased surveys for star-forming regions in molecular clouds to enhance the statistical material with the aim to understand more about the possible evolutionary track of a proto-star on its way to the main sequence. 

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. 2.3 The HH 30 system ([27]). The background image, taken with the Hubble Space Telescope (HST [28]), shows an edge-tm disk traced by the dark bar, a jet perpendicular to the disk and scattered light from the embedded proto-star. The left panel presents the CO(/ = 2 — 1) emission at large positive and negative velocities relative to the dense core narrow emission. This high velocity CO emission follows the narrow jet. The middle panel presents the CO (7 = 2 — 1) emission in two velocity intervals indicated with blue and red contours the emission approaching us/ieceding from us. This velocity pattern is consistent with Keplerian rotation around a solar mass star. The right panel presents the continuum emission due to dust grains in the circumstellar disk. The spatial resolution of the millimetre observations is 1" [27]...

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]...

Fig. 4.2 Temperature and density of H2 profiles in the envelope of the low mass proto-star IRAS 16293-2422 based on multi-wavelength observations from Grimier et ai. [19]...

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