The 4MOST-Cosmology Redshift Survey: Target Selection of Bright Galaxies and Luminous Red Galaxies
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| Main Authors: | , , , , , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866914216217149440 |
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| author | Verdier, Aurelien Rocher, Antoine Bandi, Behnood Richard, Johan Roukema, Boudewijn Loveday, Jon Tempel, Elmo Bilicki, Maciej Kneib, Jean-Paul Guitton, Mathilde |
| author_facet | Verdier, Aurelien Rocher, Antoine Bandi, Behnood Richard, Johan Roukema, Boudewijn Loveday, Jon Tempel, Elmo Bilicki, Maciej Kneib, Jean-Paul Guitton, Mathilde |
| contents | The Cosmology Redshift Survey of the 4-metre Multi-Object Spectroscopic Telescope (4MOST-CRS) will provide redshift measurements of galaxies and quasars over 5700{\degsq} in the southern hemisphere. As targets for the 4MOST-CRS, we present a selection of an $r<19.25$ magnitude limited sample of Bright Galaxies (BG) and a colour selected sample of Luminous Red Galaxies (LRG) based on DESI Legacy Survey DR10.1 photometric data, in the redshift ranges $0.1<z<0.5$ and $0.4<z<1$, respectively. These samples are selected using the $g$, $r$, $z$, and $W1$ (from unWISE) photometric bands. For BGs, the star--galaxy separation is performed based on Gaia and Tycho-2 star catalogues. Following 4MOST requirements, the target densities of BGs and LRGs are 250{\mdegsq} and 400{\mdegsq}, respectively. We quantified the stellar contamination to be $<2-4\%$ for both galaxy samples using data from the first DESI data release. Using angular clustering, we show that both samples are robust against imaging systematics, confirming a low stellar contamination. Finally, we provide forecasts of the baryonic acoustic oscillation (BAO) and growth of structure ($σ_8$) measurements from the 4MOST-CRS alone and in combination with DESI. From the 4MOST-CRS, we expect 3\% and 25\% precision on BAO and $σ_8$ measurements, respectively. Combining 4MOST-CRS with DESI improves the constraints from DESI alone by 12$\%$ in the 0.4 < z < 0.8 redshift range, leading to the most stringent constraints on BAO measurements from spectroscopic galaxy clustering. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2508_07311 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | The 4MOST-Cosmology Redshift Survey: Target Selection of Bright Galaxies and Luminous Red Galaxies Verdier, Aurelien Rocher, Antoine Bandi, Behnood Richard, Johan Roukema, Boudewijn Loveday, Jon Tempel, Elmo Bilicki, Maciej Kneib, Jean-Paul Guitton, Mathilde Cosmology and Nongalactic Astrophysics Astrophysics of Galaxies The Cosmology Redshift Survey of the 4-metre Multi-Object Spectroscopic Telescope (4MOST-CRS) will provide redshift measurements of galaxies and quasars over 5700{\degsq} in the southern hemisphere. As targets for the 4MOST-CRS, we present a selection of an $r<19.25$ magnitude limited sample of Bright Galaxies (BG) and a colour selected sample of Luminous Red Galaxies (LRG) based on DESI Legacy Survey DR10.1 photometric data, in the redshift ranges $0.1<z<0.5$ and $0.4<z<1$, respectively. These samples are selected using the $g$, $r$, $z$, and $W1$ (from unWISE) photometric bands. For BGs, the star--galaxy separation is performed based on Gaia and Tycho-2 star catalogues. Following 4MOST requirements, the target densities of BGs and LRGs are 250{\mdegsq} and 400{\mdegsq}, respectively. We quantified the stellar contamination to be $<2-4\%$ for both galaxy samples using data from the first DESI data release. Using angular clustering, we show that both samples are robust against imaging systematics, confirming a low stellar contamination. Finally, we provide forecasts of the baryonic acoustic oscillation (BAO) and growth of structure ($σ_8$) measurements from the 4MOST-CRS alone and in combination with DESI. From the 4MOST-CRS, we expect 3\% and 25\% precision on BAO and $σ_8$ measurements, respectively. Combining 4MOST-CRS with DESI improves the constraints from DESI alone by 12$\%$ in the 0.4 < z < 0.8 redshift range, leading to the most stringent constraints on BAO measurements from spectroscopic galaxy clustering. |
| title | The 4MOST-Cosmology Redshift Survey: Target Selection of Bright Galaxies and Luminous Red Galaxies |
| topic | Cosmology and Nongalactic Astrophysics Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2508.07311 |