THOR

Terry Hubble Observations of Roman (THOR) is a Data Reduction Pipeline (DRP) for parallel HST Wide-field Camera 3 (WFC3) and Advanced Camera for Surveys (ACS) images taken as part of program GO-17776 (Terry et al.), a Precursor Survey of the Roman Galactic Bulge Time Domain Survey (GBTDS) Fields.

HAMRR

Hubble Advanced Mining Routine for Roman (HAMRR; pronounced "Hammer") is a subroutine which performs a cone search on the HST catalog and returns a list of stars with measured photometry, astrometry, color-magnitude diagrams luminosity functions, image cutouts, and more.

Installation

Installing THOR/HAMRR is straightforward. From a terminal, type:

git clone https://github.com/skterry/THOR.git
cd THOR
pip install -e .

$\color{red}{\text{IMPORTANT: running the pip install will download ~3.6 GB of data to your machine.}}$

The pipeline is fully self-contained: every file THOR/HAMRR needs to run — the PSF models, the geometric-distortion correction (GDC) reference files, the test images, and the survey catalog — either already exists in the repo or is downloaded automatically during pip install -e .. There are no additional manual download steps.

This install command performs the full setup:

1. Compiles the Fortran sources in src/thor/ (hst1pass.F, thor_go_gaia.F, and thor_go_nogaia.F). Most Fortran compilers are supported (gfortran, ifort/ifx, flang, ...); however you can force a specific one with make FC=<compiler> in src/thor/, or by setting FC before installing.

2. Downloads the reference files that hst1pass/thor_go use for PSF fitting and distortion correction. These are the standard STScI library products for WFC3/UVIS and ACS/WFC in F606W and F814W:

   a. PSF models (STDPSF_*.fits) live in src/thor/PSFs/.

   b. Geometric-distortion correction files (STDGDC_*.fits) are downloaded to src/thor/GDCs/.

3. Downloads two large data files (~1 GB each) into data/. These are:

   a. A sample of images (from field HD_138) to test the THOR data reduction. data/field_HD138/

   b. The full catalog of sources detected in the HST bulge survey. data/thor_hst_wfc3_acs_bulge_v0.2_cat.fits.zip note: this is a shared-risk catalog and has not been peer-reviewed or published (as of June 2026).

Running THOR

Reducing the HST bulge survey data with THOR requires two steps:

1. Reduce the ACS and WFC3 images:

   source reduce_acs.src
   source reduce_wfc3.src

2. Collate the reduced data:

   source collate_thor.src

These scripts can be run from inside the directory example/thor_HD138/*.XYM/ to learn the reduction process. If you have downloaded external images from the survey and wish to reduce them with THOR, you will need to modify all *.src scripts.

Running HAMRR

Using HAMRR to query the HST bulge survey catalog(s) is relatively straightforward:

python path/to/hamrr.py

HAMRR can be run in two modes:

1. Interactive-mode via command line interface (CLI). This mode runs if there is no param file present (see below).

2. Parameter-file mode: If the file named params.in exists in the directory where hamrr.py is run, the code will read all pre-defined arguments given in the param file.

Required arguments for hamrr.py:

• catalog_path: Path to THOR-generated catalog (e.g. /data/hlsp_thor_hst_wfc3_acs_bulge_early-release_v1.0_cat.fits.zip)
• ra: Right Ascension sky coordinate (Decimal degrees, HMS/DMS, or Colon-separated)
• dec: Declination sky coordinate (Decimal degrees, HMS/DMS, or Colon-separated)
• radius_arcsec: Search radius (arcseconds)

Optional arguments for hamrr.py:

• save_results: Save the result table to a file? (yes/no) default: no
• save_format: File format for saved table (fits/ecsv/votable) default: none
• plot_cmd: Save the V-I, I color-magnitude diagram (CMD)? (yes/no) default: no
• plot_lf: Save a luminosity function (LF)? (yes/no) default: no
• lf_band: Passband for LF (F606W/F814W) default: F814W
• lf_normalise: Normalize the LF by sky area? (yes/no) default: none
• image_cut: Save cutout images centered on queried ra, dec? (yes/no) default: no
• imagecut_size: Pixel size for the cutout (pix). default: pixel size cutout will match cone search size from radius_arcsec argument above
• output_dir: Output directory name. default: output/

If you use data from the early-release catalog in data/hlsp_thor_hst_wfc3_acs_bulge_early-release_v1.0_cat.fits.zip please cite the following work:

@article{terry2026hst,
        title={An HST Wide-field Survey of the Galactic Bulge: Overview, Strategy, and First Results},
        author={Terry, Sean K and Anderson, Jay and Beichman, Charles A and Bennett, David P and Bhattacharya, Aparna and Beaulieu, Jean-Philippe and Gaudi, B Scott and Green, Joel and Huston, Macy J and Lu, Jessica R and others},
        journal={The Astrophysical Journal Letters},
        volume={1003},
        number={1},
        pages={L1},
        year={2026},
        publisher={The American Astronomical Society}
        }

If you use data from the full (shared-risk) catalog in data/thor_hst_wfc3_acs_bulge_v0.2_cat.fits.zip please cite the following work:

@article{terry2026thor,
        title={THOR and HAMRR},
        author={Terry, Sean K and Anderson, Jay},
        journal={Research Notes of the AAS},
        volume={10},
        number={6},
        pages={167},
        year={2026},
        publisher={The American Astronomical Society}
        }