1 / 6

VLT calibration issues IR instruments

VLT calibration issues IR instruments. N. Ageorges (ESO – Paranal). Photometry. Essentially ISAAC concerned here Many standard star fields taken during all the time of the operations Data available but not reduced/analysed properly + no publication (for large public)

senona
Download Presentation

VLT calibration issues IR instruments

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. VLT calibration issuesIR instruments N. Ageorges (ESO – Paranal)

  2. Photometry • Essentially ISAAC concerned here • Many standard star fields taken during all the time of the operations • Data available but not reduced/analysed properly + no publication (for large public) • Thinking of getting a student to do this • For mid_IR: VISIR is just starting but excellent example of TIMMI2, which provided its own list after monitoring

  3. Spectroscopy • Almost no spectrophotometric standards like in the visible • At VLT for each spectroscopic set_up, a telluric standard (essentially from the Hipparcos catalog) is observed • To determine the flux loss due to the slit, it is observed with the appropriate slit & a larger one (e.g. 2” slit for ISAAC) • No other calibration plan

  4. Polarimetry Facilities exist on almost all IR instruments at ESO but not much used & very few publications. - Why? Predominant polarization origin = Mie scattering IR techniques: sources less polarized Calibration issue: only few NIR polarimetric standards known • essentially too bright for 8-10m telescopes • Situation worse at 10mm • NIR instruments at ESO: all at Nasmyth focus • variable instrumental polarization • One more degree of complexity with adaptive optics but seems nevertheless the most requested mode • WHY?? Because of Differential polarimetric techniques (Kuhn et al., 2001, ApJ 553, L189) ?? Few calibration data available in the archive

  5. Establishing NIR polarimetric standards for large telescopes (8-10m) Granted technical project: N. Ageorges & J. Walsh Aim = use the SOFI polarimetric mode to obtain polarized & unpolarized standards in JHK with targets of K > 10mag. Data will be made available to the community as soon as available Strategy: • Observe selected fields in nearby molecular clouds (partially studied in terms of interstellar polarisation) • Observe each field in JHK, at 3 elevations • Take 3images for 3 detector positions & 4 different rotator angle Expected accuracy: 0.2% linear polarisation, 1 degree in position angle

  6. Astrometry • No proper calibration plan • Measurements done during commissionning/ paranalisation • Should we give this issue a bigger place in the future?

More Related