The HST raw data of our survey are public immediately, and can be accessed through the HST archive.
We are pleased to announce the first, partial data release of the HDUV Survey. This includes a first reduction of science-grade UV images in the GOODS-N field at 60mas pixel scale.
In particular, we provide background-subtracted, drizzled F275W and F336W images of the first complete epoch of the HDUV survey in GOODS-N in addition to CANDELS F275W UV imaging.
The HDUV survey is about 50% complete overall, with 5 out of the 8 pointings in GOODS-N completed, which are all included in this release.
The raw files were CTE-corrected, and WCS-aligned, before drizzling onto a common output grid. The reduction includes the creation and subtraction of a sky dark image to minimize detector artefacts which are present after standard dark subtraction. Specifically, after a first pass reduction, all objects are masked before stacking all the data for a sky dark image. This is shown in the figure below. The sky dark (produced separately for each filter and for the CANDELS and HDUV data) is subtracted from all images before the final drizzle iteration.
example sky dark image
WCS registration was performed relative to the 3DHST HST images (Skelton et al. 2014; available here). The F275W data also contains all the CANDELS imaging taken over this field (with post-flash). Those images were aligned using relative shifts determined by the F350LP exposures taken just prior to the F275W frames. Relative alignments are typically better than 10 mas.
Frames are stacked using an inverse variance map weighting (including the uncertainties from the postflash electrons), and we provide the corresponding RMS maps of the final drizzled images in the release. These were renormalized to account for correlated noise using the standard correction factors from Casertano et al. (2000).
- hduv_hst_wfc3-60mas_goodsn_f275w_epoch1_v0.5_drz.fits.gz F275W science image on 3DHST pixel frame
- hduv_hst_wfc3-60mas_goodsn_f275w_epoch1_v0.5_rms.fits.gz F275W rms map
- hduv_hst_wfc3-60mas_goodsn_f336w_epoch1_v0.5_drz.fits.gz F336W science image on 3DHST pixel frame
- hduv_hst_wfc3-60mas_goodsn_f336w_epoch1_v0.5_rms.fits.gz F336W rms map
The Galactic dust-corrected WFC3/UVIS AB zeropoints to be used in GOODS-N are:
- F275W: 24.065
- F336W: 24.615
These values were derived from the original WFC3/UVIS zeropoints provided by STScI and include a correction for Galactic dust based on Schlafly & Finkbeiner (2011): E(B-V) for GOODS-N = 0.0105 mag (see here).
This release is on a best-effort basis, as data reduction procedures are still updated and improved. In particular, future v1 releases will include:
- 1) CTE corrected darks, and improved handling of dark subtraction
- 2) improved cosmic ray cleaning on individual frames
- 3) improved masking of warm/hot pixels for each exposure
- 4) refined alignment of individual exposures in a second pass
For more information, please contact us at: pascal.oesch[at]yale.edu