Optical / IR interferometry by the IR and Technology Group

 

Part of the IR and Technology Group of the Rome Astronomical Observatory has been involved since 2003 in different aspects (technology, science and data reduction) of optical/IR interferometry

Hereafter a brief summary of our activity in this field is presented.

 

  • People

    • Simone Antoniucci, PhD: VINCI and MIDI data reduction – YSO’s modelling

    • Teresa Giannini: data analysis – science

    • Gianluca Li Causi: software development, optics and mechanics

    • Dario Lorenzetti: P.I. LINC-NIRVANA Patrol Camera

    • Brunella Nisini: science coordination, AMBER proposals


  • Technology

Our technological activity in the interferometry field is currently related to the LINC-NIRVANA interferometer for LBT. LINC-NIRVANA will be the first combined beam instrument at LBT, which will give coherent IR images thanks to a Layer-Oriented Multiple Field adaptive optics system.

On behalf of the COFIN 2003 funding, a collaboration has started between the LINC-NIRVANA team and our Group who has the responsibility to design, realize and integrate the star finding and monitoring system (called Patrol Camera), to serve the Mid-High Wavefront Sensor of the adaptive optics.

Participation to the phase A study of the VLTI Spectro-Imager: our group has the responsibility of the design of the IR spectrograph for that 2nd generation VLTI instrument. (grant PRIN INAF 2005)

 

Patrol Camera overwiev


The Patrol Camera Assembly mounted on the optical bench (April 2006)

  • Scientific activity related to interferometry

    Our scientific activity is currently related to the investigation of the inner (<10 AU) regions around Young Stellar Objects (YSOs). Such regions are characterized by a complex morphology where different components responsible for the source activity are present (circumstellar disks, accretion flows, collimated jets) which cannot be spatially separated by standard techniques.

    The studies in which we are currently involved are:

    • MIDI observations of the circumstellar environment of Herbig Ae/Be stars: we are comparing MIDI visibility spectra with models for the circumstellar structure of these young stars in order to constraints their geometry.

    • AMBER observations of the emission region of IR HI lines in YSOs. Current hypothesis is that NIR HI lines originate both in the accretion flows connecting the disk to the protostar and at the base of the ionized collimated winds responsible for the angular momentum removal. We are now modelling the two different scenarios to derive the corresponding visibilities and visibility contrast with respect to the continuum emission. An example is given in the following figures where the visibility at the wavelength of the Brackett gamma line (2.16 µ m) is compared with that in the adjacent continuum due to the circumstellar disk and the star, for the two cases of wind and accretion gas emission.

    • LINC-NIRVANA – Definition of targets for simulations and image reconstruction: working group on Young Stellar Objects (coordinated by B.Nisini and D.Lorenzetti)


    Expected visibility curves for wind (left) and accretion (right). (CLIK TO ENLARGE)

    Papers and Conference Proceedings

     

     

  • IDL software tool for Interferometry Visibility Computation

    Due to the lack of software tools which compute visibilities by interfacing with user’s own modelling software, an IDL (Interactive Data Language) program for that scope is currently under final developing stages: it is now available as Version 0.9 by clicking HERE. It aims to compute the interferometric visibility of a modelled source as seen by a given instrument, by allowing the user to:

    • provide multiple and custom model geometries as input;
    • use it as a subroutine within a modelling code, thus making possible to perform simultaneous fitting on different observables (e.g. a simultaneous fit of both interferometric and spectral observations).