The detectability of bars at high redshift: a case study using Euclid-like mock observations of TNG50 simulated galaxies
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arXiv
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| Format: | Preprint |
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2026
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| _version_ | 1866918354118246400 |
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| author | Gonçalves, Gustavo F. Machado, Rubens E. G. Valença, Raquel R. Athanassoula, E. Menéndez-Delmestre, Karín Bueno-Dalpiaz, Thiago |
| author_facet | Gonçalves, Gustavo F. Machado, Rubens E. G. Valença, Raquel R. Athanassoula, E. Menéndez-Delmestre, Karín Bueno-Dalpiaz, Thiago |
| contents | Modern surveys such as Euclid report a decline in the fraction of barred galaxies from the local Universe to $z \sim 1$, whereas the TNG50 simulation predicts higher bar fractions, in tension with observations. This discrepancy may be due to observational biases in bar detectability when comparing simulations with observations. We present a proof-of-concept study quantifying how Euclid-like observational conditions affect bar detectability in TNG50. We analysed the entire galaxy sample at $z = 0.5$ and highlight one borderline case with a bar length of 2.1 kpc and bar strength $A_2 = 0.4$. Synthetic images were produced with Monte Carlo radiative transfer and realistic post-processing, and analysed with ellipse fitting and Fourier decomposition, as well as the recently constructed Zoobot analysis. Results were compared to idealised, noise-free stellar mass maps. In the illustrative case the bar is clearly detected in the mass map and remains visible in the Euclid VIS $I_{\rm E}$ filter, where Zoobot also classifies it as barred, but becomes undetectable in $Y_{\rm E}$ and in the VIS-NISP RGB composite, with all methods failing outside VIS. Extending to the full $z = 0.5$ sample, Zoobot recovers only 31/141 galaxies, while $A_2$ and ellipse fitting perform better (80/141 and 67/141) but still miss many short or weak bars. When non-detections are counted as unbarred, the bar fraction of 44 percent falls to $12\!-\!33$ percent depending on the method. These results demonstrate the strong impact of observational effects on bar detectability and motivate bar-fraction estimates which incorporate realistic instrumental conditions across redshift in cosmological simulations. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2601_16335 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | The detectability of bars at high redshift: a case study using Euclid-like mock observations of TNG50 simulated galaxies Gonçalves, Gustavo F. Machado, Rubens E. G. Valença, Raquel R. Athanassoula, E. Menéndez-Delmestre, Karín Bueno-Dalpiaz, Thiago Astrophysics of Galaxies Modern surveys such as Euclid report a decline in the fraction of barred galaxies from the local Universe to $z \sim 1$, whereas the TNG50 simulation predicts higher bar fractions, in tension with observations. This discrepancy may be due to observational biases in bar detectability when comparing simulations with observations. We present a proof-of-concept study quantifying how Euclid-like observational conditions affect bar detectability in TNG50. We analysed the entire galaxy sample at $z = 0.5$ and highlight one borderline case with a bar length of 2.1 kpc and bar strength $A_2 = 0.4$. Synthetic images were produced with Monte Carlo radiative transfer and realistic post-processing, and analysed with ellipse fitting and Fourier decomposition, as well as the recently constructed Zoobot analysis. Results were compared to idealised, noise-free stellar mass maps. In the illustrative case the bar is clearly detected in the mass map and remains visible in the Euclid VIS $I_{\rm E}$ filter, where Zoobot also classifies it as barred, but becomes undetectable in $Y_{\rm E}$ and in the VIS-NISP RGB composite, with all methods failing outside VIS. Extending to the full $z = 0.5$ sample, Zoobot recovers only 31/141 galaxies, while $A_2$ and ellipse fitting perform better (80/141 and 67/141) but still miss many short or weak bars. When non-detections are counted as unbarred, the bar fraction of 44 percent falls to $12\!-\!33$ percent depending on the method. These results demonstrate the strong impact of observational effects on bar detectability and motivate bar-fraction estimates which incorporate realistic instrumental conditions across redshift in cosmological simulations. |
| title | The detectability of bars at high redshift: a case study using Euclid-like mock observations of TNG50 simulated galaxies |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2601.16335 |