Apr 032015

We are pleased to announce new v0.5 HST mosaics for Epoch 2 of the cluster MACSJ0717.5+3745, from the observations of this target from our Frontier Fields program ID 13498 (PI: J. Lotz). These mosaics complete the full depth obtained on the second epoch of this cluster, adding a further 42 orbits of WFC3/IR imaging in F105W, F125W, F140W and F160W on the main cluster, along with ACS imaging in F435W and F814W on the parallel field, and completing the total exposure time of 70 orbits on each field for this epoch, and 140 orbits total for this cluster. We have combined these data with archival data from program ID 12103 (PI: M. Postman), 13389 (PI: B. Siana), and 13459 (PI.: T. Treu), to create mosaics that are intended to contain the full depth of WFC3/IR data on the main cluster and ACS data on the parallel field. These mosaics have all been processed beyond the default pipeline calibration, including correction for time-variable background and persistence effects in WFC3/IR, as well as self-calibration processing for ACS, and astrometric alignment to the previous mosaics that have already been constructed for this cluster. Further details are provided in the readme file, which can be obtained along with all the mosaics at the following location:

Since the observations for this cluster are now complete, we have started preparing the v1.0 release which will be available in a few weeks, once updated calibration reference files have been prepared by the instrument teams, and which will be announced once it is released.

In addition, we are starting to prepare for v2.0 releases for all the Frontier Fields clusters that are complete, including Abell 2744 and MACS J0416.1-2403, to be followed by MACS J0717.5+3745 and the subsequent clusters once these are complete. These v2.0 releases will contain a variety of processing and calibration improvements relative to the current v1.0 releases, including:

  •   Improved removal of low-level background flatfield residuals
  •   Improved astrometry, including new time-dependent distortion models
  •   Reprocessing using the latest ACS self-calibration algorithms and updated WFC3/IR time-variable background removal for all data
  •   Improved masking and removal of persistence in the WFC3/IR data
  •   Consolidating all ACS and WFC3 imaging for each cluster (including more recent data, if publicly available) into full-depth mosaics.

These v2.0 releases will be distributed in the coming months, as soon as the above processing improvements are complete, and will also be subsequently carried out on the remaining Frontier Fields clusters once their observations are complete.

More general information about the data for this project can be obtained from our Frontier Fields MAST archive website:

as well as our main Frontier Fields HST project website:

and our Frontier Fields astronomer’s blog and other social media:

We hope that these high-level science products are useful for your research, and we welcome any suggestions or questions that you may have about them.

 Posted by at 11:17 am