TY - JOUR
T1 - Probing the Heights and Depths of Y Dwarf Atmospheres
T2 - A Retrieval Analysis of the JWST Spectral Energy Distribution of WISE J035934.06$-$540154.6
AU - Kothari, Harshil
AU - Cushing, Michael C.
AU - Burningham, Ben
AU - Beiler, Samuel A.
AU - Kirkpatrick, J. Davy
AU - Schneider, Adam C.
AU - Mukherjee, Sagnick
AU - Marley, Mark S.
N1 - © 2024. The Author(s). Published by the American Astronomical Society. This article is licensed under a Creative Commons Attribution 4.0 International License, To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/
PY - 2024/8/12
Y1 - 2024/8/12
N2 - We present an atmospheric retrieval analysis of the Y0 brown dwarf WISE J035934.06−540154.6 using the low-resolution 0.96-12 μm James Webb Space Telescope (JWST) spectrum presented in Beiler et al. We obtain volume number mixing ratios of the major gas-phase absorbers (H
2O, CH
4, CO, CO
2, PH
3, and H
2S) that are three to five times more precise than previous work that used Hubble Space Telescope (HST) spectra. We also find an order-of-magnitude improvement in the precision of the retrieved thermal profile, a direct result of the broad wavelength coverage of the JWST data. We used the retrieved thermal profile and surface gravity to generate a grid of chemical forward models with varying metallicity, (C/O)
atm, and strengths of vertical mixing as encapsulated by the eddy diffusion coefficient K
zz. Comparison of the retrieved abundances with this grid of models suggests that the deep atmosphere of WISE 0359−54 shows signs of vigorous vertical mixing with K
zz = 10
9 [cm
2 s
−1]. To test the sensitivity of these results to our five-knot spline thermal profile model, we performed a second retrieval using the Madhusudhan & Seager thermal profile model. While the results of the two retrievals generally agree well, we do find differences between the retrieved values of mass and volume number mixing ratio of H
2S with fractional differences of the median values of −0.64 and −0.10, respectively. In addition, the five-knot thermal profile is consistently warmer at pressure between 1 and 70 bar. Nevertheless, our results underscore the power that the broad-wavelength infrared spectra obtainable with the JWST have to characterize the atmospheres of cool brown dwarfs.
AB - We present an atmospheric retrieval analysis of the Y0 brown dwarf WISE J035934.06−540154.6 using the low-resolution 0.96-12 μm James Webb Space Telescope (JWST) spectrum presented in Beiler et al. We obtain volume number mixing ratios of the major gas-phase absorbers (H
2O, CH
4, CO, CO
2, PH
3, and H
2S) that are three to five times more precise than previous work that used Hubble Space Telescope (HST) spectra. We also find an order-of-magnitude improvement in the precision of the retrieved thermal profile, a direct result of the broad wavelength coverage of the JWST data. We used the retrieved thermal profile and surface gravity to generate a grid of chemical forward models with varying metallicity, (C/O)
atm, and strengths of vertical mixing as encapsulated by the eddy diffusion coefficient K
zz. Comparison of the retrieved abundances with this grid of models suggests that the deep atmosphere of WISE 0359−54 shows signs of vigorous vertical mixing with K
zz = 10
9 [cm
2 s
−1]. To test the sensitivity of these results to our five-knot spline thermal profile model, we performed a second retrieval using the Madhusudhan & Seager thermal profile model. While the results of the two retrievals generally agree well, we do find differences between the retrieved values of mass and volume number mixing ratio of H
2S with fractional differences of the median values of −0.64 and −0.10, respectively. In addition, the five-knot thermal profile is consistently warmer at pressure between 1 and 70 bar. Nevertheless, our results underscore the power that the broad-wavelength infrared spectra obtainable with the JWST have to characterize the atmospheres of cool brown dwarfs.
KW - astro-ph.SR
KW - astro-ph.EP
UR - http://www.scopus.com/inward/record.url?scp=85201292735&partnerID=8YFLogxK
U2 - 10.3847/1538-4357/ad583b
DO - 10.3847/1538-4357/ad583b
M3 - Article
SN - 0004-637X
VL - 971
JO - The Astrophysical Journal
JF - The Astrophysical Journal
IS - 2
M1 - 121
ER -