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The interaction of young stars with their environments.

Objectives:

To determine the nature and implications of outflows from young stars by analysing their physical parameters and spatial structure, via:
  1. Observation. To apply 3D spectroscopy to the study of outflowing phenomena from pre-main sequence stars. To obtain good quality data for selected nebulous objects in star forming regions through the detailed spectro-imaging and spectrophotometric study at the 2.6m and 6m telescopes of Byurakan Observatory and Special Astrophysical Observatory (SAO).

  2. Analysis. To compare the data with existing theoretical models for the dynamics and evolution of stellar environments. To elaborate new theoretical models and simulations, especially for such phenomena as helical jets and helical structures in nebulae.

  3. Interpretation. To explore
    1. the hidden inflow-outflow connection at the heart of a young stellar system,
    2. the evolution of the system's spin by searching for the signs of rotation and precession,
    3. the dynamical feedback into the environment and
    4. the physics of shock waves and magnetic fields in the interstellar medium.

  4. Advancement. To improve the observational capabilities of the 2.6m and 6m telescopes by purchasing and installation of optical elements (high-resolution grism, filters, gratings) specific to the above goals.

Background & Justification:

Stars are the basic constituents of the visible Universe. How and why interstellar clouds turn into stars has, until very recently, been mainly a subject of conjecture. Our instruments have not been sufficiently sensitive or tuned to explore or penetrate the obscuring clouds. Star formation is the single most urgent problem waiting to be elucidated in stellar evolution. And without an understanding of how stars form, we cannot hope to understand how galaxies evolve.

Young stars drive atomic and molecular outflows. Perhaps the most spectacular manifestations of these flows are Herbig-Haro objects and jets. Herbig-Haro (HH) flows are optically visible shock-excited nebulae, and they demonstrate the existence of exceedingly well-collimated and highly supersonic wind components (e.g. Reipurth et al., 1986). The HH flows have proven to be key phenomena for deciphering events in the earliest stellar evolutionary phases, which are otherwise very difficult to study. We reason that stars cannot form without these flows to carry away the collapse-resisting angular momentum.

Small cometary nebulae near the young stars represent the illuminated cavities through which the jets flow. Another very interesting problem is represented by recently detected helical structures in these nebulae (Magakian & Movsessian, 1999). On the other hand, quite a number of very small jets (so-called microjets) with an extent of only 3-5 arcsec have been found. Their evolutionary status and relation with other kinds of jets are not very well understood yet. Their spectroscopic investigation is particularly interesting because it allows us to study the launch and collimation region of jets (Solf, 1997). 3D spectroscopy (Fabri-Perot scanning interferometry, multi-pupil spectroscopy) offers unique possibilities to obtain simultaneously spectral information from the full spatial extent of the object, thus greatly increasing the efficiency of the observations. The main advantage of 3D spectroscopy is the possibility of obtaining the full maps of physical parameters for various astronomical objects, thus producing the high-quality material for the further theoretical analysis.

It should be also remarked that 3D spectroscopy would permit us to study faint emission structures superimposed on the bright continuum background (e.g., jets in the bright cometary nebulae), which are very difficult to analyze by means of the usual methods.

In our work we plan to study the kinematics of the HH jets, distributions of the physical parameters, morphology of the faint structures in cometary nebula, spectral asymmetry in cometary nebula, .interpret the observations in terms of geometry and physics and predict the global flow conditions which determine the observed properties. The 2.6m Byurakan telescope is equipped with prime-focus pointing and auto-guiding system "Bonnette", which allows to extend the exposures for full night if necessary and to position objects with high accuracy. The system is under remote control. On this adapter could be attached different instruments. The 6m SAO telescope is one of the largest telescopes in the world (see the Web site www.sao.ru). For our purposes for 3D spectroscopy we plan to use the new MPFS integral field spectrograph (with fiber optics) and Fabry-Perot scanning interferometer in the prime focus.

Programme:

The project tasks are to be performed in parallel:
  1. Preparation of the best targets for the observations (Byurakan, Armagh).
  2. Conduction of spectroscopic observations at Byurakan and SAO by means of Fabry-Perot and multi-pupil spectroscopy. (Byurakan, SAO)
  3. Purchasing and installation of the new necessary equipment at Byurakan and SAO: the optics and gratings for higher-dispersion spectroscopy, interference filters, polarimetric analyzer. (Marseille, Byurakan, SAO)
  4. Software development and refining, data processing and analysis (Marseille, Byurakan, SAO)
  5. Theoretical models and simulations. Analysis of shock wave physics. Development of 3D visualisation procedures. (Armagh)
  6. Theoretical models and simulations. Analysis of shock wave physics. Development of 3D visualisation procedures. (Armagh)
  7. Final report and publication of the first results of studies of the selected objects (all participants)

The task division is as follows:
Armagh team : Overall Management and Coordination; Preparation of the best targets for spectroscopy; Theoretical analysis and models; Analysis and publication of the results.

Byurakan team : Preparation of the best targets for spectroscopy; Conduction of spectroscopic observations; Purchasing and Installation of the new necessary equipment at Byurakan (filters, grism); Software Development; Data handling and reduction; Analysis and publication of the results.

Marseille : Equipment installation (Fabry-Perot scanning interferometer); Software Development; Data handling and reduction; Analysis and publication of the results;

SAO team : Purchasing and Installation of the new necessary equipment at SAO (Optics and grating for high-resolution spectroscopy). Conduction of spectroscopic observations; Software Development; Data handling and reduction; Analysis and publication of the results.

The schedule is as follows:

Start of the project : June 2001, Total duration : 24 months

Action/Duration
  1. Preparation of the observational programme / 2 months
  2. Conduction of spectroscopic observations at Byurakan and SAO/ 24 months
  3. Purchase and transfer to Byurakan of the red grism and filters and to SAO optics and grating / 6 months
  4. Software development and data reduction / 18 months
  5. Development of theoretical models, computer code and numerical telescope and grism for atomic gas simulations. /12 months;
  6. Application and model fitting, interpretation and introduction of new physics and dynamics / 12 months
  7. Publication of results in main astrophysical journals, mentioned Web sites, and Final Report to INTAS - at the end of the first and second years of the project.
Coordinator: Michael D.Smith
Armagh Observatory,
Fax : +44 2837 527174
Tel  : +44 2837 522928
E-mail : mds@star.arm.ac.uk
 
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