Mission Overview
The HST Legacy Archival Uniform Reduction of Local Group Imaging (LAURELIN)
Primary Investigator: Meredith Durbin
HLSP Authors: Meredith Durbin, Alessandro Savino, Dan Weisz, Yumi Choi
Released: 2025-09-03
Updated: 2025-09-03
Primary Reference(s): Durbin et al. 2025
DOI: 10.17909/b8yw-wv58
Citations: See ADS Statistics
Source Data:
Overview
The HST Legacy Archival Uniform REduction of Local Group ImagiNg (LAURELIN) provides homogeneously reduced resolved stellar photometry catalogs for 36 ultra-faint dwarf galaxies (UFDs) within 400 kpc observed with HST ACS/WFC. Catalogs were produced with DOLPHOT (Dolphin 2000, 2016) and are described in detail in Durbin et al. (2025).
Data Products
The LAURELIN files have the following naming convention:
hlsp_laurelin_hst_acs-wfc_<target>_<filter>_v1_<product-type>.fits
where:
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<target> = Name of photometric subregion the mosaic covers, in the format "<galaxy>-<number>"
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<filter> = Name of the filter used, one of "f606w" or "f814w"
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<product-type> = The product type of the file, one of "drc" or "cat" as described below.
Data file types:
| _drc.fits |
Drizzled mosaics used as astrometric references. |
| _cat.fits |
Full-stack 2-band photometry tables, including both full-stack and exposure-level measurements. |
Image Mosaic Files
The mosaic files have the following naming convention:
hlsp_laurelin_hst_acs-wfc_<target>_<filter>_v1_drc.fits
where:
- <target> = Name of photometric subregion the mosaic covers, in the format "<galaxy>-<number>"
- <filter> = Name of the filter used, one of "f606w" or "f814w"
Catalog Files
The catalog files have the following naming convention:
hlsp_laurelin_hst_acs-wfc_<target>_f606w-f814w_v1_cat.fits
where:
- <target> = Name of photometric subregion the mosaic covers, in the format "<galaxy>-<number>"
The catalog files herein contain binary fits tables of photometry for the LAURELIN archival project, as described in Durbin et al. (2025). The measurements were made using the DOLPHOT (Dolphin 2000, Dolphin 2016) PSF photometry package, performed on CTE-corrected *flc files.
The naming conventions and column names for the photometry files are summarized below, as well as in the headers of the FITS files themselves and in Appendix A of Durbin et al. (2025). The columns include:
- RA - ICRS Right Ascension of the source in decimal degrees
- DEC - ICRS Declination of the source in decimal degrees
- X - X value of the pixel position on the reference drizzled image
- Y - Y value of the pixel position on the reference drizzled image
- OBJTYPE - Object type (1=bright star, 2=faint)
These are followed by 10 columns for each filter, described in detail in the DOLPHOT documentation.
- <Filter>_COUNT - Total source counts, combined over all images in <Filter>
- <Filter>_SKY - Total sky level, combined over all images in <Filter>
- <Filter>_VEGA - Vega magnitude, combined over all images in <Filter>
- <Filter>_ERR - Uncertainty on magnitude, combined over all images in <Filter>
- <Filter>_CHI - Chi of the PSF fit, combined over all images in <Filter>
- <Filter>_SNR - Signal-to-noise ratio of the PSF fit, combined over all images in <Filter>
- <Filter>_SHARP - Sharpness of the PSF fit, combined over all images in <Filter>
- <Filter>_ROUND - Roundness of the PSF fit, combined over all images in <Filter>
- <Filter>_CROWD - Crowding of the PSF fit (magnitude subtracted due to neighboring stars), combined over all images in <Filter>
- <Filter>_FLAG - Quality flag of the PSF fit, combined over all images in <Filter> (< 4 recommended)
These are then followed by the GST flag for each filter.
- <Filter>_GST_FLAG - Does the source pass the GST ("good star") criteria of Durbin et al. (2025)? (0: no, 1: yes)
The rest of the columns are the per-exposure measurements:
- <Image>_COUNT - Source counts in <Image>
- <Image>_SKY - Sky level around source in <Image>
- <Image>_VEGA - Vega magnitude of the PSF fit in <Image>
- <Image>_ERR - Uncertainty on magnitude of the PSF fit in <Image>
- <Image>_CHI - $\chi$ of the PSF fit in <Image>
- <Image>_SNR - Signal-to-noise ratio of the PSF fit in <Image>
- <Image>_SHARP - Sharpness of the PSF fit in <Image>
- <Image>_ROUND - Roundness of the PSF fit in <Image>
- <Image>_CROWD - Crowding of the PSF fit in <Image>
- <Image>_FLAG - Quality flag of the PSF fit in <Image>
Null values are indicated by 99.999 in the VEGA columns, and 9.999 in ERR.
Data Access
MAST Portal and Astroquery
The LAURELIN data products are available in the MAST Search Portal (web-based, cross-mission search interface) and Astroquery (Python package to search for and download files from Python scripts you write).
- In the MAST Search Portal, set the Provenance Name filter to "LAURELIN" in an Advanced Search to find these data. The user guide for how to search and download products using the MAST Portal is available here.
- For Astroquery, the following example code demonstrates how to search for and download these products. This code assumes that you want to download all products from this HLSP, so you may want to consider narrowing down your search for large HLSPs (> 10 GB) or those with many individual files (> 10k). You can find more astroquery.mast tutorials here.
from astroquery.mast import Observations
# Search for all LAURELIN products
all_obs = Observations.query_criteria(provenance_name="laurelin")
data_products = Observations.get_product_list(all_obs)
# Print the number of data products that would be downloaded
print(len(data_products))
# Download data
Observations.download_products(data_products)
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A web-based interface for cross-mission searches of data at MAST or the Virtual Observatory.
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Search for and download data products for this HLSP programmatically in Python.
Citations
Please remember to cite the appropriate paper(s) below and the DOI 10.17909/b8yw-wv58 if you use these data in a published work.
Note: These HLSP data products are licensed for use under CC BY 4.0.