A Wide-Field WFC3 Imaging Survey with Grism Spectroscopy in the COSMOS Field ("3D-DASH")
Primary Investigator: Iva Momcheva
HLSP Authors: Lamiya Mowla, Sam Cutler, Gabe Brammer, Iva Momcheva, Kate Whitaker, Pieter van Dokkum
Primary Reference(s): Mowla et al. 2022
Citations: See ADS Statistics
The 3D-Drift And SHift (3D-DASH) program is a Hubble Space Telescope WFC3 F160W imaging and G141 grism survey of the equatorial COSMOS field. 3D-DASH is the widest HST/WFC3 imaging survey in the F160W filter to date, subsuming the COSMOS-DASH pilot survey. 3D-DASH extends the legacy of HST near-infrared imaging and spectroscopy to degree-scale swaths of the sky, enabling the identification and study of distant galaxies (z > 2) that are rare or in short-lived phases of galaxy evolution at rest-frame optical wavelengths. The region covered by the survey spans RA 09:58:00 to 10:02:57 and dec +01:36:00 to +02:51:00 (ICRS).
Observed with the efficient DASH technique, the F160W imaging mosaic comprises 1256 individual WFC3 pointings corresponding to a total area of 1.35 deg2, extending to 1.43 deg2 when combined with ancillary archival data. The total footprint is about twice the area of COSMOS-DASH. Generally, guide star acquisitions make it impractical to observe multiple pointings per orbit, so very wide near-IR surveys with HST are inefficient. However, this limitation can be overcome by guiding with gyros alone, which is possible when HST operates with three gyros. 3D-DASH, like COSMOS-DASH, observed eight independent WFC3-IR pointings per orbit, taking advantage of the fact that HST drifts by only a very small amount in the 25 seconds between non-destructive reads of unguided exposures.
Because the DASH method leads to shifts during exposures, reducing DASH data is more complex than for guided exposures. For full details, see Momcheva et al. (2017) for the DASH technique, Mowla et al. (2019) for the pilot COSMOS-DASH image, and Mowla et al. (2022) for the 3D-DASH image. Results from the COSMOS-DASH program showed that with appropriate data reduction methods, the DASH technique preserves the WFC3 spatial resolution, and that galaxy structural parameters are consistent with those measured from guided surveys (see Mowla et al. 2019 and Cutler et al. 2022).
In this first 3D-DASH release, the team presents the reduced F160W imaging mosaic. Grism spectroscopy covering 1.43 deg2 will be made available in a future release.
The initial release of 3D-DASH provides imaging products only. These imaging mosaic products are available at MAST in multiple formats. Each mosaic is available as a single, large image (and an accompanying weight map) with the following naming convention:
- <pointings> = the source data from which the mosaic was constructed, either "combined" (DASH pointings combined with ancillary archival data, covering 1.43 deg2) or "dash" (DASH pointings only, covering 1.35 deg2).
- <version> = version, e.g. "v1.0"
- <type> = product type, either "drz-sci" (drizzled, calibrated mosaic image) or "drz-wht" (weight map corresponding to the drz-sci image).
The "combined" mosaic products are also available as smaller tile files from a grid of the observed field. Portions of this grid are empty, and only the 150 tiles containing data are provided here. These tile files have the following naming convention:
- <tile> = [tile_x].[tile_y], e.g. "01.05". Each tile covers approximately 6.9x6.9 arcmin2 of the sky.
Other fields are the same as described above. Only <pointings>="combined" products are available as tiles.
Data file types:
|drz-sci.fits||drizzled, calibrated 3D-DASH mosaic of the COSMOS field|
weight-map corresponding to the 3D-DASH mosaic
The team has provided a Python Notebook for extracting image cutouts (available on Deepnote and GitHub) and an interactive image explorer that includes both 3D-DASH and other surveys. The cutout Notebook and the image explorer are linked here for convenience but are not owned or maintained by MAST; questions about software should be directed to the authors of Mowla et al. 2022.
The tile files (both drz-sci.fits and drz-wht.fits) of the "combined" mosaic are available in the MAST Portal (web-based, cross-mission search interface) and Astroquery (Python package to search for and download files from Python scripts you write). In contrast, the large single mosaic files are available only via direct download links in the table below. Set the Provenance Name filter to 3D-DASH in the Portal Advanced Search to find all or individual tiles. Each observation in the Portal contains a single tile. Both the drz-sci and drz-wht products of each tile are selected as minimum recommended products. The tiles can be retrieved programmatically by using the astroquery.mast module. See a code example below for retrieving and downloading all tiles.
from astroquery.mast import Observations all_obs = Observations.query_criteria(provenance_name="3d-dash") data_products = Observations.get_product_list(all_obs) Observations.download_products(data_products)
For those who want to download all tile files, we also provide a bulk download script in the table below.
Imaging mosaic products from the "combined" 3D-DASH mosaic (including DASH pointings combined with ancillary archival data) are available as small tile files or large single files as follows:
|Download Links||File Count
(drz-sci.fits + drz-wht.fits)
|3D-DASH combined mosaic tiles (bulk download script, 20GB)||300||Run the shell script in your terminal. The script uses curl, which is likely already installed on your machine (and if not, is freely available as open source software). The total storage space required is approximately 20 GB.|
|3D-DASH combined mosaic single image (22 GB)
3D-DASH combined mosaic single weight map (22 GB)
|2||Two direct download links. The total storage space required is approximately 50 GB.|
Imaging mosaic products from the "dash" mosaic (including DASH pointings only) are available as large single files as follows:
|Download links||File Count
(drz-sci.fits + drz-wht.fits)
|3D-DASH dash-only mosaic single image (19 GB)
3D-DASH dash-only mosaic single weight map (19 GB)
|2||Two direct download links. Total storage space required is approximately 40 GB.|