PSF Modelling Þ Find out the optical characteristics of your instrument i. e. how stable is the PSF with position? For HST, a PSF must be created for each object Þ TinyTim (HST) or DAOPHOT (Ground-based) Þ Limited PSF size means limited dynamic range ("The residual square") Þ Jitter in TinyTim : What value should you use? Recipe: Pick a star in your image Generate series of TinyTim PSFs with jitter values in the range 0-30 mas Run GIMFIT2D on star with the different PSFs For most HST data, no jitter will be fine. Þ Make sure PSF has NO background Þ GIM2D does normalize PSF volume to 1 for you Þ PSF Types : tiny_wfpc (Pixel scattering function is applied) tiny_nic tiny_stis gaussian (Needs both imscale and seeing to be defined) user (Use for ground based work) delta (i. e. no convolution, use with big galaxies, may still be a bit buggy ..)
| Previous slide | Next slide | Back to the index | View Graphic Version |
No notes for slide 11