Mission Overview

Lyman Continuum Galaxy Candidates in COSMOS ("LCGCOSMOS")


Primary Investigator: Jeff Cooke

HLSP Authors: Laura J. Prichard, Marc Rafelski, Ben Sunnquist, Mitchell Revalski

Released: 2021-10-14

Updated: 2021-10-14

Primary Reference(s): Prichard et al. 2021

DOI: 10.17909/t9-pe8e-s980

Citations: See ADS Statistics

Read Me

Source Data:

Comparison of old versus new HST image reductions.
COSMOS-ACS/F814W image cutout (Koekemoer et al. 2007) with survey footprints relevant to this work with new LCG candidates overlaid. Two deep WFC3/F336W (purple) and three parallel ACS/F435W (light blue) pointings with names and orbit depths are shown. The CANDELS-ACS/F606W (light green; Grogin et al. 2011; Koekemoer et al. 2011) and ZFOURGE survey (yellow; Straatman et al. 2016) footprints are also shown. The LCG candidates are split into three categories: spectroscopic candidates/Group A (red stars and ZFOURGE IDs), and photometric candidates, both Group B (blue circles) and C (dark blue diamonds, lowest priority candidates). See Prichard et al. 2021 for more details on the LCG candidate group categorization.


Deep Hubble Space Telescope rest-frame UV Wide Field Camera 3 (WFC3)/F336W and Advanced Camera for Surveys (ACS)/F435W imaging (GO 15100, PI Cooke, 30 orbits) are used for the detection of Lyman Continuum Galaxy (LCG) candidates in the COSMOS field ("LCGCOSMOS"). LCGs are individual sources that emit ionizing flux below the Lyman break (< 912 Angstroms) and can be used to constrain cosmic reionization parameters.

The team made several improvements to the standard Space Telescope Science Institute (STScI) WFC3/UVIS reduction pipeline, to clean and calibrate the images beyond what was previously available from MAST. The team also developed and applied additional, novel calibrations to the charge transfer efficiency (CTE)-corrected single-exposure calibrated images (called FLCs). Some of these improvements have been added to the standard WFC3/UVIS MAST pipeline, while others are additional calibration improvements (available on GitHub). See Prichard et al. 2021 for more details.

This High Level Science Product contains the final reduced and aligned WFC3/F336W images (with the new calibrations) and ACS/F435W images. The mosaics are mapped onto a larger reference image and aligned to COSMOS coordinates. The images have pixel scales 0.03", pixels aligned north, and all pointings for each filter combined into a single image for each band. The pointings span ~40 arcmin2 total and have an average depth of ~29 mag at 5σ. The point spread functions (PSF) for each pointing are also provided.

Data Products

All of the image files have this naming convention:



  • <ins> = Instrument used, either "acs" or "wfc3".
  • <filter> = Filter used, either "f336w" or "f435w".
  • <datatype> = Product extension, see table below for possible values.

The PSF files have this naming convention:



  • <ins> = Instrument used, either "acs" or "wfc3".
  • <field> = The pointing (or "field"), either "f1", "f1a", "f1b", or "f2". See the Figure for the location and orientation of each pointing.
  • <filter> = Filter used, either "f336w" or "f435w".

Data file types:

_sci.fits Science images.
_wht.fits Weight images.

Root-mean squared error images (1/sqrt(wht)), correlated noise is not included.

_exp.fits Exposure time maps.
_ctx.fits Context images.

Point spread function (PSF) images normalized to 1.

Data Access

Filter Instrument Image Files PSF Files
F336W WFC3

| drc-ctx.fits | drc-exp.fits | drc-rms.fitsdrc-sci.fitsdrc-wht.fits |

| Field 1 | Field 2 |

| drc-ctx.fits | drc-exp.fits | drc-rms.fitsdrc-sci.fitsdrc-wht.fits |

Field 1A | Field 1B | Field 2 |



Please remember to cite the appropriate paper(s) below and the DOI if you use these data in a published work. 

Note: These HLSP data products are licensed for use under CC BY 4.0.