Other
Scientific paper
May 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993phdt.......177g&link_type=abstract
Ph.D. Thesis, Univ. of Granada, Spain, (1993)
Other
3
Scientific paper
We have studied several outflow phenomena in star-forming regions, as well as the ambient molecular gas with which they interact, all this for different spacial scales. These scales range from ˜1 pc in the champagne flow of the HII region GM 24 and in the molecular outflows of AFGL 437 and NGC 2024, to the 100 AU in the protoplanetary disks of HL Tau and L1551-IRS 5. Such disks, in addition to being the likely precursors of new planetary systems, seem to be responsible for the collimation of stellar jets, like the ones present in the regions of Serpens and HH 1-2. With these studies we intend to obtain an overview of the process of star formation, instead of focusing in only one of its manifestations.
In the regions of high-mass star formation of GM 24, AFGL 437 and NGC 2024 we find that anisotropic distributions of the ambient molecular gas determine the geometry, kinematics and evolution of the outflow processes, leading in some cases to novel interpretations on the nature of these outflows.
We find ammonia emission downstream of the Herbig-Haro object 2. The lack of heating and turbulence in the ammonia condensations, as well as the fast proper motions of HH 2 make us favor a stellar jet model to explain the origin of this HH object.
Also with ammonia observations we confirm that the triple radio-continuum source in Serpens is located in our galaxy, since local heating of the galactic molecular gas and widening of the molecular lines are observed toward its position. We think that the heating may be produced by the radiation field from the central low-mass star. On the other hand, the most likely cause of the line widening is the presence of shocks produced by a stellar jet.
Using the VLA with 0.''4 resolution, we tried to obtain the first direct detection of protoplanetary disks of ˜100 AU radius around young stars. The continuum observations at 1.3 cm of HL Tau show an elongated structure whose size and flux density suggest that it represents the protoplanetary disk we are looking for. However, we can not confirm this interpretation, since the orientation of the observed structure is not consistent with the orientation of the outflow processes and other structures interpreted as disks in HL Tau. Our ammonia observations of the postulated protoplanetary molecular disks around HL Tau and L1551-IRS 5 did not show any emission of this molecule. This non-detection allowed us to derive upper limits of 0.02 and 0.1 Modot to the mass of the disks in HL Tau and L1551-IRS 5, respectively. By comparing these limits with the masses deduced from previous indirect observations, we conclude that even though we must be close to detect protoplanetary structures with the current instruments, we may have to wait for a new generation of telescopes to confirm their existence.
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