20.500.12556/RUL-176455 Quantifying spectroscopic flux variations between JWST NIRISS and NIRSpec: slit losses in emission line measurements of z ∼ 1–3 galaxies We analyse James Webb Space Telescope (JWST) Near Infrared Imager and Slitless Spectrograph (NIRISS) and Near Infrared Spectrograph (NIRSpec) spectroscopic observations in the Abell 2744 galaxy cluster field. From approximately 120 candidates, we identify 12 objects with at least two prominent emission lines among [O II]⁠$\lambda$3727, H$\beta\lambda$4861, [O III]$\lambda$4959, [O III]$\lambda$5007 and H$\alpha\lambda$6563 that are spectroscopically confirmed by both instruments. Our key findings reveal systematic differences between the two spectrographs based on source morphology and shutter aperture placement. Compact objects show comparable or higher integrated flux in NIRSpec relative to NIRISS (within 1$\sigma$ uncertainties), while extended sources consistently display higher flux in NIRISS measurements. This pattern reflects NIRSpec’s optimal coverage for compact objects while potentially undersampling extended sources. Quantitative analysis demonstrates that NIRSpec recovers at least 63 per cent of NIRISS-measured flux when the slit covers >15 percent of the source or when $R_e$ < 1kpc. For lower coverage or larger effective radii, the recovered flux varies from 24 per cent to 63 per cent. When studying the H$\alpha\lambda$6563/[O III]$\lambda$5007 emission line ratio, we observe that measurements from these different spectrographs can vary by up to ~0.3 dex, with significant implications for metallicity and star formation rate characterizations for individual galaxies. These results highlight the importance of considering instrumental effects when combining multi-instrument spectroscopic data and demonstrate that source morphology critically influences flux recovery between slit-based and slitless spectroscopic modes in JWST observations. galaxies spectroscopy galaksije spektroskopija true false true Angleški jezik Slovenski jezik Članek v reviji 2025-12-01 14:43:32 2025-12-01 14:43:33 2025-12-21 04:08:40 0000-00-00 00:00:00 2025 0 0 Str. 1915-1925 iss. 2 Vol. 544 Dec. 2025 0000-00-00 Zaloznikova Objavljeno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 524.8 1365-2966 10.1093/mnras/staf1837 259428611 staf1837.pdf staf1837.pdf 1 5E0F3C16D1B998D08EBD03DDD5415EE1 2b70b543fb5ae27c5b9d6e98f60d9fe534fc3b6c8c52ce364c52f2b6267947a0 71fae350-cebb-11f0-9328-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=222789 https://academic.oup.com/mnras/article/544/2/1915/8300808 0 7f4390d0-cebb-11f0-9328-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=222790 Fakulteta za matematiko in fiziko 0 0 0