Clouds and Chemistry: Ultracool Dwarf Atmospheric Properties from Optical and Infrared Colors

By M. Marley, Sara Seager, D. Saumon, K. Lodders, A. Ackerman, R. Freedman, Xiaohui Fan. 2001

282 citations recorded by the source corpus.

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.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/501c23fac06b08b5a645771403371504510919e2

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Citations in the corpus

New spectral types L and T (2005, methodology): “Burgasser et al. (2002b), elaborating on an idea suggested by Ackerman & Marley (2001), have used the Marley et al. (2002) models to propose a possible A nn u.”
LARGE-AMPLITUDE VARIATIONS OF AN L/T TRANSITION BROWN DWARF: MULTI-WAVELENGTH OBSERVATIONS OF PATCHY, HIGH-CONTRAST CLOUD FEATURES (2012, background): “At these cool temperatures, an understanding of atmospheric condensates— which affect luminosities, radii, cooling histories, and spectral morphologies—is essential to deriving correct physical properties for both cool BDs and giant planets (e.g. Marley et al. 2002; Burrows et al. 2011).”
A Unified Theory for the Atmospheres of the Hot and Very Hot Jupiters: Two Classes of Irradiated Atmospheres (2007, background): “It was significantly revised to model the atmospheres of brown dwarfs (Marley et al. 1996; Burrows et al. 1997; Marley et al. 2002) and irradiated giant planets (Marley & McKay 1999, for Uranus).”
From thermal dissociation to condensation in the atmospheres of ultra hot Jupiters: WASP-121b in context (2018, unknown): “The code was first developed for Titan’s atmosphere (McKay et al. 1989) and since then has been extensively used for the study of giant planets (Marley et al. 1996), brown dwarfs (Marley et al. 2002; Burrows et al. 1997), and hot Jupiters (Fortney et al. 2005, 2008; Showman et al. 2009).”
PLANETARY POPULATION SYNTHESIS COUPLED WITH ATMOSPHERIC ESCAPE: A STATISTICAL VIEW OF EVAPORATION (2014, background): “Since then, it has been extensively modified and adapted for studies on giant planets (Marley & McKay 1999), brown dwarfs (Marley et al. 1996, 2002; Burrows et al. 1997), and hot Jupiters (e.g., Fortney et al. 2005, 2008; Showman et al. 2009).”
HST hot-Jupiter transmission spectral survey: evidence for aerosols and lack of TiO in the atmosphere of WASP-12b (2013, background): “Solar system observations and brown dwarf models indicate condensate scale heights which are ∼1/3 that of the local gas scale height (Carlson et al. 1994; Marley et al. 2002), a possibility for hot-Jupiter atmospheres as well (Fortney 2005).”
MASSES, RADII, AND CLOUD PROPERTIES OF THE HR 8799 PLANETS (2012, methodology): “Stephens et al. (2009) fit the model spectra of Marley et al. (2002) to the 1–15 μm spectra of L and T dwarfs and found that L dwarf cloud clearing (as characterized by large fsed) occurs at Teff ∼ 1300 K for log g = 5.0 and at ∼1100 K for log g = 4.5, although the sample size was admittedly small…”
3D mixing in hot Jupiters atmospheres. I. Application to the day/night cold trap in HD 209458b (2013, background): “The code was first developed for Titan’s atmosphere (McKay et al. 1989) and since then has been extensively used for the study of giant planets (Marley et al. 1996), brown dwarfs (Marley et al. 2002; Burrows et al. 1997), and hot Jupiters (e.g., Fortney et al. 2005, 2008; Showman et al. 2009).”
The Spectra of T Dwarfs. II. Red Optical Data (2003, background): “…(Tsuji, Ohnaka, & Aoki 1996; Tsuji et al. 1999; Allard et al. 1996, 2001; Burrows et al. 1997; Ackerman & Marley 2001; Tsuji 2002; however, see Marley et al. 2002; Burrows et al. 2002a), although low-level near-infrared photometric (Enoch, Brown, & Burgasser 2003) and spectroscopic (Nakajima…”
COLORS AND KINEMATICS OF L DWARFS FROM THE SLOAN DIGITAL SKY SURVEY (2010, background): “This behavior is likely due to the decrease in KS-band flux due to increasingly strong absorption in water and methane bands (Marley et al. 2002; Knapp et al. 2004).”
THE HAWAII INFRARED PARALLAX PROGRAM. I. ULTRACOOL BINARIES AND THE L/T TRANSITION, (2012, background): “…have reproduced the general properties of the spectra, colors, and magnitudes of late-L to mid-T dwarfs based on prescriptions for the clouds (Marley et al. 2002; Tsuji 2002; Burrows et al. 2006), and parameterized models can be successfully fitted to broad-wavelength observations of…”
QUANTITATIVELY ASSESSING THE ROLE OF CLOUDS IN THE TRANSMISSION SPECTRUM OF GJ 1214b (2013, methodology): “Many modeling groups apply the general assumptions of equilibrium chemistry that we apply here (e.g. Tsuji et al. 1996; Allard et al. 2001; Marley et al. 2002; Burrows et al. 2006; Cushing et al. 2008; Visscher et al. 2010), though these models differ in the details of their approaches.”
Dust in brown dwarfs - III. Formation and structure of quasi-static cloud layers (2004, unknown): “Static model atmosphere calculations for brown dwarfs with frequency-dependent radiative transfer and mixing-length theory (e.g. Allard et al. 2001; Burrows et al. 2002; Marley et al. 2002; Tsuji 2002) have, therefore, mainly used ad hoc assumptions for the treatment of the dust component so far.”
THE DISCOVERY OF Y DWARFS USING DATA FROM THE WIDE-FIELD INFRARED SURVEY EXPLORER (WISE) (2011, methodology): “A detailed description of the basic models can be found in Marley et al. (2002), Saumon & Marley (2008), Cushing et al. (2008), and Stephens et al. (2009).”
EXOPLANET ALBEDO SPECTRA AND COLORS AS A FUNCTION OF PLANET PHASE, SEPARATION, AND METALLICITY (2010, methodology): “The spectra of both brown dwarfs and our solar system’s giant planets can only be reproduced when chemistry calculations incorporate this process (Fegley & Lodders 1994; Marley et al. 2002; Burrows et al. 2002).”
A TEMPERATURE AND ABUNDANCE RETRIEVAL METHOD FOR EXOPLANET ATMOSPHERES (2009, background): “6 One reason the approach of indirectly including stellar irradiation is valid is that the visible and infrared opacities are largely decoupled (Marley et al. 2002).”
Planetary Radii across Five Orders of Magnitude in Mass and Stellar Insolation: Application to Transits (2006, unknown): “…study of giant planet thermal structure by Marley & McKay (1999) and has also been employed to study the atmospheres of the hot Jupiters (Marley 1998; Fortney et al. 2005, 2006) as well as brown dwarfs (Marley et al. 1996; Burrows et al. 1997; Marley et al. 2002), albeit without incident radiation.”