The impact of medium-width bands on the selection, and subsequent luminosity function measurements, of high-z galaxies
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2025
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| author | Adams, N. J. Austin, D. Harvey, T. Conselice, C. J. Trussler, J. A. A. Li, Q. Westcott, L. Ferreira, L. Rusakov, V. Goolsby, C. M. |
| author_facet | Adams, N. J. Austin, D. Harvey, T. Conselice, C. J. Trussler, J. A. A. Li, Q. Westcott, L. Ferreira, L. Rusakov, V. Goolsby, C. M. |
| contents | New, ultra-deep medium-width photometric coverage with JWST's NIRCam instrument provides the potential for much improved photo-z reliability at high redshifts. In this study, we conduct a systematic analysis of the JADES Origins Field, which contains 14 broad- and medium-width near-infrared bands, to assess the benefits of medium band photometry on high-z completeness and contamination rates. Using imaging reaching AB mag $29.8-30.35$ depth, we test how high-z selections differ when images are artificially degraded or bands are removed. In parallel, the same experiments are conducted on simulated catalogues from the JAGUAR semi-analytic model to examine if observations can be replicated. We find sample completeness is high ($80\%+$) and contamination low ($<4\%$) when in the $10σ+$ regime, even without the use of any medium-width bands. The addition of medium-width bands leads to increases in completeness ($\sim10\%$) but multiple bands are required to improve contamination rates due to the small redshift ranges over which they probe strong emission lines. Incidents of Balmer-Lyman degeneracy increase in the $5-7σ$ regime and this can be replicated in both simulated catalogues and degraded real data. We measure the faint-end of the UV LF at $8.5<z<13.5$, finding high number densities that agree with previous JWST observations. Overall, medium bands are effective at increasing completeness and reducing contamination, but investment in achieving comparable depths in the blue ($<1.5μ$m) as achieved in the red is also found to be key to fully reducing contamination from high-z samples. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2502_10282 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | The impact of medium-width bands on the selection, and subsequent luminosity function measurements, of high-z galaxies Adams, N. J. Austin, D. Harvey, T. Conselice, C. J. Trussler, J. A. A. Li, Q. Westcott, L. Ferreira, L. Rusakov, V. Goolsby, C. M. Astrophysics of Galaxies New, ultra-deep medium-width photometric coverage with JWST's NIRCam instrument provides the potential for much improved photo-z reliability at high redshifts. In this study, we conduct a systematic analysis of the JADES Origins Field, which contains 14 broad- and medium-width near-infrared bands, to assess the benefits of medium band photometry on high-z completeness and contamination rates. Using imaging reaching AB mag $29.8-30.35$ depth, we test how high-z selections differ when images are artificially degraded or bands are removed. In parallel, the same experiments are conducted on simulated catalogues from the JAGUAR semi-analytic model to examine if observations can be replicated. We find sample completeness is high ($80\%+$) and contamination low ($<4\%$) when in the $10σ+$ regime, even without the use of any medium-width bands. The addition of medium-width bands leads to increases in completeness ($\sim10\%$) but multiple bands are required to improve contamination rates due to the small redshift ranges over which they probe strong emission lines. Incidents of Balmer-Lyman degeneracy increase in the $5-7σ$ regime and this can be replicated in both simulated catalogues and degraded real data. We measure the faint-end of the UV LF at $8.5<z<13.5$, finding high number densities that agree with previous JWST observations. Overall, medium bands are effective at increasing completeness and reducing contamination, but investment in achieving comparable depths in the blue ($<1.5μ$m) as achieved in the red is also found to be key to fully reducing contamination from high-z samples. |
| title | The impact of medium-width bands on the selection, and subsequent luminosity function measurements, of high-z galaxies |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2502.10282 |