Clouds and chemistry

Ultracool dwarf atmospheric properties from optical and infrared colors

Mark S. Marley, S. Seager, D. Saumon, Katharina Lodders, Andrew S. Ackerman, Richard S. Freedman, Xiaohui Fan

Research output: Contribution to journalArticle

213 Citations (Scopus)

Abstract

The optical and infrared colors of L and T dwarfs are sensitive to cloud sedimentation and chemical equilibrium processes in their atmospheres. The i′-z′ versus J-K color-color diagram provides a window into diverse atmospheric processes mainly because different chemical processes govern each color, and cloud opacity largely affects J-K but not i′-z′. Using theoretical atmosphere models that include for the first time a self-consistent treatment of cloud formation, we present an interpretation of the i′-z′ versus J-K color trends of known L and T dwarfs. We find that the i′-z′ color is extremely sensitive to chemical equilibrium assumptions; chemical equilibrium models accounting for cloud sedimentation predict redder i′-z′ colors - by up to 2 mag - than models that neglect sedimentation. We explore the previously known J-K color trends in which objects first become redder, then bluer with decreasing effective temperature. Only models that include sedimentation of condensates are able to reproduce these trends. We find that the exact track of a cooling brown dwarf in J-K (and i′-z′) is very sensitive to the details of clouds, in particular to the efficiency of sedimentation of condensates in its atmosphere. We also find that clouds still affect the strength of the J-, H-, and K-band fluxes of even the coolest T dwarfs. In addition, we predict the locus in the i′-z′ versus J-K color-color diagram of brown dwarfs cooler than yet discovered.

Original languageEnglish (US)
Pages (from-to)335-342
Number of pages8
JournalAstrophysical Journal
Volume568
Issue number1 I
DOIs
StatePublished - Mar 20 2002
Externally publishedYes

Fingerprint

chemistry
color
color-color diagram
chemical equilibrium
sedimentation
trends
atmospheres
condensates
condensate
loci
atmosphere
extremely high frequencies
opacity
coolers
diagram
cooling
chemical process
temperature
chemical
trend

Keywords

  • Stars: atmospheres
  • Stars: low-mass, brown dwarfs

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Marley, M. S., Seager, S., Saumon, D., Lodders, K., Ackerman, A. S., Freedman, R. S., & Fan, X. (2002). Clouds and chemistry: Ultracool dwarf atmospheric properties from optical and infrared colors. Astrophysical Journal, 568(1 I), 335-342. https://doi.org/10.1086/338800

Clouds and chemistry : Ultracool dwarf atmospheric properties from optical and infrared colors. / Marley, Mark S.; Seager, S.; Saumon, D.; Lodders, Katharina; Ackerman, Andrew S.; Freedman, Richard S.; Fan, Xiaohui.

In: Astrophysical Journal, Vol. 568, No. 1 I, 20.03.2002, p. 335-342.

Research output: Contribution to journalArticle

Marley, MS, Seager, S, Saumon, D, Lodders, K, Ackerman, AS, Freedman, RS & Fan, X 2002, 'Clouds and chemistry: Ultracool dwarf atmospheric properties from optical and infrared colors', Astrophysical Journal, vol. 568, no. 1 I, pp. 335-342. https://doi.org/10.1086/338800
Marley MS, Seager S, Saumon D, Lodders K, Ackerman AS, Freedman RS et al. Clouds and chemistry: Ultracool dwarf atmospheric properties from optical and infrared colors. Astrophysical Journal. 2002 Mar 20;568(1 I):335-342. https://doi.org/10.1086/338800
Marley, Mark S. ; Seager, S. ; Saumon, D. ; Lodders, Katharina ; Ackerman, Andrew S. ; Freedman, Richard S. ; Fan, Xiaohui. / Clouds and chemistry : Ultracool dwarf atmospheric properties from optical and infrared colors. In: Astrophysical Journal. 2002 ; Vol. 568, No. 1 I. pp. 335-342.
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