What is T-PHOT 

T-PHOT (Merlin et al. 2015, 2015A&A…582A..15M; Merlin et al. 2016, accepted on A&A, arXiv:1609.00146) is a new software designed for high precision, prior-based photometry in crowded, deep extragalactic fields, developed by the Astrodeep collaboration.

Example of a simulation set used to test the accuracy of the T_PHOT performance: LRI (top left), residual image (top middle) and accuracy of the flux determination (bottom, relative flux difference [f_meas − f_input] / f_input ; different symbols and colors for points refer to various diagnostics as explained in the legend; black line: average in bins; yellow shade: standard deviation) relative a simulated IRAC1 image with synthetic PSF processed with whole image fitting.

Example of a simulation set used to test the accuracy of the T_PHOT performance: LRI (top left), residual image (top middle) and accuracy of the flux determination (bottom, relative flux difference [f_meas − f_input] / f_input ; different symbols and colors for points refer to various diagnostics as explained in the legend; black line: average in bins; yellow shade: standard deviation) relative a simulated IRAC1
image with synthetic PSF processed with whole image fitting.

It represents an evolution of its direct predecessors TFIT (Laidler et al. 2007) and CONVPHOT (Grazian et al. 2007).
T-PHOT uses the data from a high resolution image of the a region of the sky as priors for position and morphology.

It can use as priors:

  1. the observed 2-D profiles in the high resolution image, gathering it from a detection catalog and segmentation map,
  2. input analytical models (e.g. Galfit stamps), or
  3. a list of positions for unresolved objects.

Convolving such data with a convolution kernel, T-PHOT then produces low-resolution templates which will be used to obtain precision photometric measurements on a lower resolution image of the same field. Compared to its predecessors, T-PHOT is much faster (up to 100x faster than TFIT when used with identical parameters), more accurate and versatile. It has already been tested on a wide range of images from the far infrared to the UV domains, proving to be an excellent tool for photometric analysis.

The latest public version is v2.0, which includes new features and options; see this page to download the code tarball. If you wish to get the previous publicly released version (v1.5.11) please contact emiliano.merlin@oa-roma.inaf.it.