Ultra-deep large binocular camera u-band imaging of the goods-north field: Depth versus resolution

Teresa A. Ashcraft, Rogier A. Windhorst, Rolf A. Jansen, Seth H. Cohen, Andrea Grazian, Diego Paris, Adriano Fontana, Emanuele Giallongo, Roberto Speziali, Vincenzo Testa, Konstantina Boutsia, Robert W. O’connell, Michael J. Rutkowski, Russell E. Ryan, Claudia Scarlata, Benjamin Weiner

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


We present a study of the trade-off between depth and resolution using a large number of U-band imaging observations in the GOODS-North field from the Large Binocular Camera (LBC) on the Large Binocular Telescope (LBT). Having acquired over 30 hr of data (315 images with 5–6 minutes exposures), we generated multiple image mosaics, starting with the best atmospheric seeing images (FWHM<0 8), which constitute ∼10% of the total data set. For subsequent mosaics, we added in data with larger seeing values until the final, deepest mosaic included all images with FWHM<1 8 (∼94% of the total data set). From the mosaics, we made object catalogs to compare the optimal-resolution, yet shallower image to the lower-resolution but deeper image. We show that the number counts for both images are ∼90% complete to UAB<26 mag. Fainter than UAB∼27 mag, the object counts from the optimal-resolution image start to drop-off dramatically (90% between UAB=27 and 28 mag), while the deepest image with better surface-brightness sensitivity (mAB U < 32 mag arcsec−2) show a more gradual drop (10% between UAB≃27 and 28 mag). For the brightest galaxies within the GOODS-N field, structure and clumpy features within the galaxies are more prominent in the optimal-resolution image compared to the deeper mosaics. We conclude that for studies of brighter galaxies and features within them, the optimal-resolution image should be used. However, to fully explore and understand the faintest objects, the deeper imaging with lower resolution are also required. Finally, we find—for 220 brighter galaxies with UAB<23 mag—only marginal differences in total flux between the optimal-resolution and lower-resolution light-profiles to mAB U <32 mag arcsec−2. In only 10% of the cases are the total-flux differences larger than 0.5 mag. This helps constrain how much flux can be missed from galaxy outskirts, which is important for studies of the Extragalactic Background Light.

Original languageEnglish (US)
Article number064102
JournalPublications of the Astronomical Society of the Pacific
Issue number988
StatePublished - 2018

Bibliographical note

Funding Information:
We thank the anonymous referee for the helpful comments and suggestions. The LBT is an international collaboration among institutions in the United States, Italy, and Germany. LBT Corporation partners are The University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; The Ohio State University; and The Research Corporation, on behalf of The University of Notre Dame, University of Minnesota, and University of Virginia. R. A. Windhorst acknowledges support from NASA JWST grants NAG-12460 and NNX14AN10G. Facility: LBT(LBC).

Publisher Copyright:
© 2018. The Astronomical Society of the Pacific. All rights reserved.


  • Diffuse radiation
  • Galaxies: general
  • Galaxies: photometry
  • Methods: data analysis
  • Techniques: high angular resolution
  • Techniques: image processing


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