Wide Area VISTA Extragalactic Survey (WAVES): Selection of targets for the Wide survey using decision-tree classification
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| Formato: | Preprint |
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2025
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| _version_ | 1866911207014793216 |
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| author | Kaur, G. Bilicki, M. Bellstedt, S. Tempel, E. Hellwing, W. A. Baldry, I. Bandi, B. Barsanti, S. Driver, S. Guerra-Varas, N. Holwerda, B. Lagos, C. Loveday, J. Robotham, A. |
| author_facet | Kaur, G. Bilicki, M. Bellstedt, S. Tempel, E. Hellwing, W. A. Baldry, I. Bandi, B. Barsanti, S. Driver, S. Guerra-Varas, N. Holwerda, B. Lagos, C. Loveday, J. Robotham, A. |
| contents | The Wide-Area VISTA Extragalactic Survey (WAVES) on the 4-metre Multi-Object Spectroscopic Telescope (4MOST) includes two flux-limited subsurveys with very high (95\%) completeness requirements: Wide over $\sim\!1200$ deg$^2$ and Deep over $\sim\!65$ deg$^2$. Both are $Z$-band selected, respectively as $Z<21.1$ and $Z<21.25$ mag, and additionally redshift-limited, while the true redshifts are not known a priori but will be only measured by 4MOST. Here, we present a classification-based method to select the targets for WAVES-Wide. Rather than estimating individual redshifts for the input photometric objects, we assign probabilities of them being below $z=0.2$, the redshift limit of the subsurvey. This is done with the supervised machine learning approach of eXtreme Gradient Boosting (XGB), trained on a comprehensive spectroscopic sample overlapping with WAVES fields. Our feature space is composed of nine VST+VISTA magnitudes from $u$ to $K_s$ and all the possible colors, but most relevant for the classification are the $g$-band and the $u-g$, $g-r$ and $J-K_s$ colors. We check the performance of our classifier both for the fiducial WAVES-Wide limits, as well as for a range of neighboring redshift and magnitude thresholds, consistently finding purity and completeness at the level of 94-95\%. We note, however, that this performance deteriorates for sources close to the selection limits, due to deficiencies of the current spectroscopic training sample and the decreasing signal-to-noise of the photometry. We apply the classifier trained on the full spectroscopic sample to 14 million photometric galaxies from the WAVES input catalog, which have all 9 bands measured. Our work demonstrates that a machine-learning classifier could be used to select a flux- and redshift-limited sample from deep photometric data. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2510_11132 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Wide Area VISTA Extragalactic Survey (WAVES): Selection of targets for the Wide survey using decision-tree classification Kaur, G. Bilicki, M. Bellstedt, S. Tempel, E. Hellwing, W. A. Baldry, I. Bandi, B. Barsanti, S. Driver, S. Guerra-Varas, N. Holwerda, B. Lagos, C. Loveday, J. Robotham, A. Cosmology and Nongalactic Astrophysics Astrophysics of Galaxies Instrumentation and Methods for Astrophysics The Wide-Area VISTA Extragalactic Survey (WAVES) on the 4-metre Multi-Object Spectroscopic Telescope (4MOST) includes two flux-limited subsurveys with very high (95\%) completeness requirements: Wide over $\sim\!1200$ deg$^2$ and Deep over $\sim\!65$ deg$^2$. Both are $Z$-band selected, respectively as $Z<21.1$ and $Z<21.25$ mag, and additionally redshift-limited, while the true redshifts are not known a priori but will be only measured by 4MOST. Here, we present a classification-based method to select the targets for WAVES-Wide. Rather than estimating individual redshifts for the input photometric objects, we assign probabilities of them being below $z=0.2$, the redshift limit of the subsurvey. This is done with the supervised machine learning approach of eXtreme Gradient Boosting (XGB), trained on a comprehensive spectroscopic sample overlapping with WAVES fields. Our feature space is composed of nine VST+VISTA magnitudes from $u$ to $K_s$ and all the possible colors, but most relevant for the classification are the $g$-band and the $u-g$, $g-r$ and $J-K_s$ colors. We check the performance of our classifier both for the fiducial WAVES-Wide limits, as well as for a range of neighboring redshift and magnitude thresholds, consistently finding purity and completeness at the level of 94-95\%. We note, however, that this performance deteriorates for sources close to the selection limits, due to deficiencies of the current spectroscopic training sample and the decreasing signal-to-noise of the photometry. We apply the classifier trained on the full spectroscopic sample to 14 million photometric galaxies from the WAVES input catalog, which have all 9 bands measured. Our work demonstrates that a machine-learning classifier could be used to select a flux- and redshift-limited sample from deep photometric data. |
| title | Wide Area VISTA Extragalactic Survey (WAVES): Selection of targets for the Wide survey using decision-tree classification |
| topic | Cosmology and Nongalactic Astrophysics Astrophysics of Galaxies Instrumentation and Methods for Astrophysics |
| url | https://arxiv.org/abs/2510.11132 |