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
Mar 242015
 

We are pleased to announce the first 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). In this second epoch, the orientation of HST enables the instruments to be swapped, in order to obtain WFC3/IR imaging on the main cluster field and ACS imaging on the parallel field, with a total of 28 orbits so far that have been obtained from this program during this epoch. We have combined these data with archival data from programs 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:

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 8:47 am
Feb 022015
 

We are pleased to announce the Version 1.0 release of Epoch 1 of MACSJ1149.5+2223, after the completion of the first 70 orbits of ACS and WFC3/IR imaging on this cluster and its parallel field from our Frontier Fields program ID 13504 (PI: J. Lotz). These v1.0 mosaics have been fully recalibrated relative to the v0.5 mosaics that we have released during the course of this epoch from November 2014 to January 2015. For ACS, the v1.0 mosaics incorporate new bias and dark current reference files, along with CTE correction and bias destriping, and also include a set of mosaics that have been processed with the new selfcal approach to better account for the low level dark current structure. The WFC3/IR v1.0 mosaics have improved masking for persistence and bad pixels, and in addition include a set of mosaics that have been corrected for time-variable sky emission that can occur during the orbit and can otherwise impact the up-the-ramp count-rate fitting if not properly corrected. Further details are provided in the readme file, which can be obtained along with all the mosaics at the following location:

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 10:19 pm
Jan 102015
 

We are pleased to announce new v0.5 HST mosaics for the cluster MACSJ1149.5+2223, from the observations of this target from our Frontier Fields program ID 13504 (PI: J. Lotz). The observations for this epoch are now complete at a total of 70 orbits, which we have combined into mosaics on the main cluster field observed with WFC3/IR (F105W, F125W, F140W, F160W) and on the parallel field with ACS (F435W, F606W, F814W). We note that these v0.5 mosaics do not yet include older archival data from CLASH or from other programs; this is to help facilitate study of transient phenomena, for which the data from our program 13504 can be compared with other datasets. All other archival data will be combined together with the Frontier Fields data when we release the full-depth v1.0 mosaics. The current v0.5 mosaics have all been processed beyond the default pipeline calibration. For ACS, these mosaics incorporate CTE correction and bias destriping, while the WFC3/IR mosaics have been masked for persistence, bad pixels, and other detector defects, and also include a set that have been corrected for time-variable background emission in the IR. All the mosaics are aligned to a common pixel grid, as well as to an absolute astrometric frame based on pre-existing catalogs of this field. Further details are provided in the readme file, which can be obtained along with all the mosaics at the following link:

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 2:32 pm
Jan 102015
 

We are pleased to announce the Version 1.0 release of Epoch 1 of MACSJ0717.5+3745, after the completion of the first 70 orbits of ACS and WFC3/IR imaging on this cluster and its parallel field from our Frontier Fields program ID 13498 (PI: J. Lotz). These full-depth v1.0 mosaics also include archival ACS and WFC3/IR data in the Frontier Fields filter set, from programs 9722 and 10420 (PI: H. Ebeling), programs 10493 and 10793 (PI: A. Gal-Yam), program 12103 (PI: M. Postman), program 13389 (PI: B.Siana), and program 13459 (PI: T. Treu). These v1.0 mosaics have been fully recalibrated relative to the v0.5 mosaics that we have released during the course of this epoch in October and November 2014. For ACS, the v1.0 mosaics incorporate new bias and dark current reference files, along with CTE correction and bias destriping, and also include a set of mosaics that have been processed with the new selfcal approach to better account for the low-level dark current structure. The WFC3/IR v1.0 mosaics have improved masking for persistence and bad pixels, and in addition include a set of mosaics that have been corrected for time-variable sky emission that can occur during the orbit and can otherwise impact the up-the-ramp count-rate fitting if not properly corrected. Further details are provided in the readme file, which can be obtained along with all the mosaics at the following location:

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 2:30 pm
Sep 242014
 

We are pleased to announce the Version 1.0 release of Epoch 2 of MACSJ0416.1-2403 after the completion of all the ACS and WFC3/IR imaging on the main cluster and parallel field from our Frontier Fields program
(13496, PI: J. Lotz). These v1.0 mosaics have been fully recalibrated relative to the v0.5 mosaics that we released regularly throughout the course of this epoch during August and September 2014. For ACS, the v1.0 mosaics incorporate new bias and dark current reference files, along with bias destriping and correction for CTE losses, and also include a set of mosaics that have been processed with the new selfcal approach to better correct for low-level dark current structure. The WFC3/IR v1.0 mosaics have improved masking for persistence and bad pixels, and in addition include a set of mosaics that have been corrected for time-variable sky emission that can occur during the orbit and can otherwise impact the up-the-ramp count-rate fitting if not properly corrected. Further details are provided in the readme file, which can be obtained along with all the mosaics at the following location:

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 2:52 pm
Sep 162014
 

UPDATE — Light Sabers have Earthly Origin!

24 September 2014

New investigations of these artifacts have determined the root cause.  They are not due to internal light scattering. These so called light saber are the result of bright earth flat fields that left persistence, which was then imprinted on our Frontier Fields data. Some, but not all of the persistence was flagged, thereby resulting in the remaining persistence appearing in our final image products.

Now that we have identified the root cause, we are DOING SOMETHING BETTER…..

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

16 September 2014

A new undocumented artifact appeared in the Frontier Fields exposures of the MACSJ0416.1-2403 cluster on Visit 94. As seen in Figure 1, the artifact appears almost as a string of satellite trails that appear strongly on the left side of the images and diminish greatly towards the right side of the images.

Scattered light from a bright star just outside the field of view produced artifacts, affectionately called light sabers.

Figure 1:  Scattered light in the MACSJ0416 field of view, thought to be from a bright star just outside the field of view.

Due to their unique appearance, we call these artifacts “light sabers,” following the theme of the WFC3 “Death Star” artifact. Light sabers are most apparent in the first exposure of the F105w filter, and less intensely so in exposures 2-4 for F105w and in exposures 1-4 of the F160w filter. The suspect image is the first exposure in F105w, with the presence of the artifact in subsequent exposures and in the F160w images regarded as persistence of the initial light scattering.

The main cause of the light sabers artifact is considered to be internal scattering of the light from the bright star located at 04:16:6.9752, -24:05:43.01 (RA,DEC). The main light saber is marked in a purple (Figure 2) with the rest of sabers (thought to be harmonics of the primary) marked in other colors. The dashed green line seems more likely to be due to a satellite trail.

Figure 2:  Highlighted light saber artifacts, believed to be caused by the bright star just outside the field of view.

Figure 2: Highlighted light saber artifacts, believed to be caused by the bright star just outside the field of view.

To determine if a unique position on the detector would cause the effect, the centroid of the bright star was mapped onto WFC3 detector coordinates. The ACS drizzled image of MACS0416 from 2014-Jan-10 in F435W was used to determine the centroid of the bright star and obtain the precise RA/DEC coordinates. Drizzlepac’s SKYTOPIX was used to map the coordinates of the star to WFC3 and the results are shown in the plot.

Figure 3:

Figure 3:  The location of the bright star as determined in separate exposures in different filters, shown in WFC3 sky coordinates.

The light saber effect is caused by the exposure indicated with the red circle in Figure 3, with the gold points representing images showing the artifact via persistence. A well-documented and associated glint caused by the bright starlight is also indicated in green. The results seem to indicate that the light saber effect is primarily seen when the bright star is positioned very close to vertical center on the detector and -55 pixels off of WFC3’s frame. This position matches closely with the noted position of the instrument baffle as indicated in Tom Brown’s 2007 ISR 2007-16.

An example of the glint can be seen in Figure 4 inside the red circle.  Additional information and examples are available in Brown’s ISR 2008-06.  The associated glint is thought to be caused by bright starlight scattering off the knife-edge of the baffle, and we suspect the light saber effect to be caused by the same.

Figure 4:  An example of the glint.  See ISR 2008-06 for more information.

Figure 4: An example of the glint. See ISR 2008-06 for more information.

A mask has been created for light sabers and any images affected have been appropriately reduced.  All pixels impacted by this effect in the current epoch were fully masked, so that the final combined mosaics of MACSJ0416.1-2403 do not include any of the affected pixels.  Upcoming observations of MACS0717 are found to not be affected by this particular artifact, and future Frontier Fields observations will be positioned appropriately and taken with the effect of light sabers in mind.

Harish Khandrika – Frontier Fields Science Data Products Team Member – WFC3/IR

 Posted by at 11:55 am
Sep 082014
 

We are pleased to announce the Yale Frontier Fields Workshop November 12-14 in New Haven, CT.

This workshop will be an opportunity for observers and theorists to discuss their work on Frontier Fields data obtained by Hubble, Spitzer, and other telescopes, and to prepare for the remaining data yet to come.  Topics will include high-redshift galaxies, galaxy cluster lens modeling, cluster masses and dynamics, intracluster light, supernovae, and future science.

Please submit abstracts by September 20 to yalehffworkshop2014@gmail.com.  Include your name, institution, position, presentation title and abstract, and preference for a talk or poster.  There is no registration fee, but space is limited.

For more details, please see:
http://www.astro.yale.edu/yale_frontier_workshop/

FF-Yale-2014-logo

And please circulate to colleagues and students.

We hope to see you November 12-14 in New Haven!

-Priya Natarajan and Dan Coe (SOC chairs)

 Posted by at 10:33 am
Aug 022014
 

Epoch 2 observations for the MACSJ0416.1-2403 cluster and its parallel field have been scheduled and began executing yesterday.  This epoch places WFC3/IR on the main cluster and ACS/WFC on the parallel field.

These observations will continue through late August and probably early September.  You can watch the progress of the scheduling and execution of these observations on our status page:

http://archive.stsci.edu/prepds/frontier/obs-status/

The large exposure numbers listed in late August (at the time of this writing) merely indicate the total number of exposures during that observing window and that those exposures have not been planned on specific days yet.

Keep checking back and watch the observations add up!

 Posted by at 1:38 pm
Jul 282014
 

We are thrilled to announce the v1.0 release of Abell 2744, Epoch 2, which completes all the Frontier Fields observations of our first cluster!

The Abell 2744 cluster with all observations from both Frontier Fields epochs.

The Abell 2744 cluster with all observations from both Frontier Fields epochs.

This second epoch consisted of 70 orbits on the main cluster with ACS (in F435W, F606W, F814W) and on the parallel field with WFC3/IR (in F105W, F125W, F140W and F160W), thereby complementing the 70 orbits obtained in Epoch 1 with WFC3/IR on the main cluster and ACS on the parallel field, in the same filters.

Abell 2744 parallel field, with observations from both Frontier Fields epochs.

Abell 2744 parallel field, with all observations from both Frontier Fields epochs.

The v1.0 mosaics for this epoch are completely reprocessed and include the following:

  • recalibration of all exposures using the latest, up-to-date reference files for dark current, read-noise and bad pixel masks
  • high-quality astrometric alignment, generally achieving accuracies within 0.01 pixel for the mean offset measurements of exposures relative to one another.
  • for ACS data, an additional “self-calibration” step is included, which improves especially the low-level noise in the images by means of a more accurate treatment of the underlying dark current structure
  • for WFC3/IR data, improved flagging of pixels affected by persistence and detector defects, as well as correction and removal of issues related to time-variable sky background.

Together with the previous Epoch 1 release, the full dataset achieves final depths of ~28.7 – 29th ABmag across all filters. Further details on these science-ready mosaics can be found in the Readme file,
along with the full mosaics, which are all available at our MAST webpages:

http://archive.stsci.edu/prepds/frontier/

All of these mosaics are immediately ready for science!  What will you discover?

 Posted by at 3:31 pm