Stellar Cartography

The JWST/NIRISS Deep Spectroscopic Survey for Young Brown Dwarfs and Free-Floating Planets

By Keith Cowing
Status Report
astro-ph.EP
August 26, 2024
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The JWST/NIRISS Deep Spectroscopic Survey for Young Brown Dwarfs and Free-Floating Planets
Example of the background subtraction process applied to the calibrated slope image cutouts between Stage 2 and Stage 3 of the JWST Science Calibration Pipeline. Top panel: Cutout for one source showing the dispersion of the spectrum (central rows). Rows above and below the spectral trail have a purple hue indicative of the background, which increases in strength towards longer wavelengths. Bottom panel: Following background subtraction, the cutout now only shows significant flux from the source. The color scale is the same for both panels. Data inside the shaded regions are ignored when analyzing the 1D spectrum in the following analysis. White pixels are “NaN” values that do not affect the spectral extraction. — astro-ph.EP

The discovery and characterization of free-floating planetary-mass objects (FFPMOs) is fundamental to our understanding of star and planet formation.

Here we report results from an extremely deep spectroscopic survey of the young star cluster NGC1333 using NIRISS WFSS on the James Webb Space Telescope. The survey is photometrically complete to K~21, and includes useful spectra for objects as faint as K~20.5.

The observations cover 19 known brown dwarfs, for most of which we confirm spectral types using NIRISS spectra. We discover six new candidates with L-dwarf spectral types that are plausible planetary-mass members of NGC1333, with estimated masses between 5-15 MJup. One, at ~5 MJup, shows clear infrared excess emission and is a good candidate to be the lowest mass object known to have a disk.

We do not find any objects later than mid-L spectral type (M < ~4 MJup). The paucity of Jupiter-mass objects, despite the survey’s unprecedented sensitivity, suggests that our observations reach the lowest mass objects formed like stars in NGC1333.

Our findings put the fraction of FFPMOs in NGC1333 at ~10% of the number of cluster members, significantly more than expected from the typical log-normal stellar mass function. We also search for wide binaries in our images and report a young brown dwarf with a planetary-mass companion.

Color-composite of the two NIRISS WFSS images of NGC1333 observed in this spectroscopic survey. To create the composite, we used the F150W image for the blue channel and the F200W image for the green and red channels. For the red/green channels, the highest/lowest values were cropped. The narrow gaps between the images in the mosaic were interpolated. — astro-ph.EP

Adam B. Langeveld, Aleks Scholz, Koraljka Mužić, Ray Jayawardhana, Daniel Capela, Loïc Albert, René Doyon, Laura Flagg, Matthew de Furio, Doug Johnstone, David Lafrèniere, Michael Meyer

Comments: Accepted for publication in AJ. 26 pages, 15 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2408.12639 [astro-ph.EP] (or arXiv:2408.12639v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2408.12639
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Related DOI:
https://doi.org/10.3847/1538-3881/ad6f0c
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Submission history
From: Adam Langeveld
[v1] Thu, 22 Aug 2024 18:00:00 UTC (37,108 KB)
https://arxiv.org/abs/2408.12639

Astrobiology

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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