The Disk Population of the Chamaeleon I Star-forming Region

By K. Luhman, L. Allen, P. R. Allen, R. Gutermuth, L. Hartmann, Eric Mamajek, S. T. Megeath, P. Myers, G. Fazio. 2008

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We present a census of circumstellar disks in the Chamaeleon I star-forming region. Using the Infrared Array Camera and the Multiband Imaging Photometer on board the Spitzer Space Telescope, we have obtained images of Chamaeleon I at 3.6, 4.5, 5.8, 8.0, and 24 μm. To search for new disk-bearing members of the cluster, we have performed spectroscopy on objects that have red colors in these data. Through this work, we have discovered four new members of Chamaeleon I with spectral types of M4, M6, M7.5, and L0. The first three objects are highly embedded (AJ ∼ 5) and reside near known protostars, indicating that they may be among the youngest low-mass sources in the cluster (τ < 1 Myr ). The L0 source is the coolest known member of Chamaeleon I. Its luminosity implies a mass of 0.004-0.01 M☉, making it the least massive brown dwarf for which a circumstellar disk has been reliably detected. To characterize the disk population in Chamaeleon I, we have classified the infrared spectral energy distributions of the 203 known members that are encompassed by the Spitzer images. Through these classifications, we find that the disk fraction in Chamaeleon I is roughly constant at ~50% from 0.01 to 0.3 M☉. These data are similar to the disk fraction of IC 348, which is a denser cluster at the same age as Chamaeleon I. However, the disk fraction at M≳ 1 M☉ is significantly higher in Chamaeleon I than in IC 348 (65% vs. 20%), indicating longer disk lifetimes in Chamaeleon I for this mass range. Thus, low-density star-forming regions like Chamaeleon I may offer more time for planet formation around solar-type stars than denser clusters.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/e44565efe505db4f5b449e05d97a8b407fdeee9c

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Citations in the corpus

A STEEPER THAN LINEAR DISK MASS–STELLAR MASS SCALING RELATION (2016, methodology): “In this way we excluded all ClassIII objects (Luhman et al. 2008).”
THE DISK POPULATION OF THE UPPER SCORPIUS ASSOCIATION (2012, background): “Mid-IR variability of this size is more likely to occur in stars with disks (Luhman et al. 2008, 2010).”
X-Shooter study of accretion in Chamaeleon I (2015, background): “The difference in age between the Lupus and Chamaeleon I regions is probably smaller than 1–2 Myr, if there is any difference at all (e.g., Luhman et al. 2008; Alcalá et al. 2014).”
AN INFRARED/X-RAY SURVEY FOR NEW MEMBERS OF THE TAURUS STAR-FORMING REGION (2009, methodology): “If we estimate the mass of 2M 0437+2331 based on its luminosity as done by Luhman et al. (2008) for the coolest member of Chamaeleon I, then we arrive at a value of 4-7 MJup for an assumed age range of 1-3 Myr.”
Timescale of mass accretion in pre-main-sequence stars (2009, unknown): “…is available in the electronic form. fIRAC (Table 2): Taurus – 62% (Hartmann et al. 2005), NGC 2068/71 – 70% (Flaherty & Muzerolle 2008), Cha I – 52%÷ 64% (Luhman et al. 2008), IC 348 – 47% (Lada et al. 2006), σ Ori – 35% (Hernández et al. 2007), Trumpler 37 – 47% (Sicilia-Aguilar et al. 2006),…”
CRYSTALLINE SILICATES AND DUST PROCESSING IN THE PROTOPLANETARY DISKS OF THE TAURUS YOUNG CLUSTER (2007, background): “The median magnitude difference between the spectra at a wavelength of 8 μm is 0.24 mag, and variation at this wavelength and on this scale is seen in only 1–2% of Class II objects in the similar Cha I cloud (see e.g., Luhman et al. 2008).”
The Formation and Early Evolution of Low-Mass Stars and Brown Dwarfs (2012, background): “Surveys of these regions have discovered a few hundred members that are likely to be brown dwarfs (>M6) with spectral types as late as early L (Lodieu et al. 2008, Luhman et al. 2009b, 2008, Weights et al. 2009, Zapatero Osorio et al. 2000).”
BANYAN. XI. The BANYAN Σ Multivariate Bayesian Algorithm to Identify Members of Young Associations with 150 pc (2018, background): “Chamaeleontis (EPSC; Mamajek et al. 2000; Feigelson et al. 2003; Murphy et al. 2013) is a young (3–5 Myr) and relatively distant (100–120 pc) association that is part of the Chamaeleon molecular cloud complex (Luhman et al. 2008).”
PHOTOEVAPORATION OF CIRCUMSTELLAR DISKS BY FAR-ULTRAVIOLET, EXTREME-ULTRAVIOLET AND X-RAY RADIATION FROM THE CENTRAL STAR (2008, background): “There appears to be a peak in disk fraction as a function of stellar type (a surrogate for stellar mass) in some clusters (Lada et al. 2006; Luhman et al. 2008; S. Strom 2007, private communication), as well as an increased incidence of debris disks with increasing stellar mass (Trilling et al.…”
THE DISK POPULATION OF THE TAURUS STAR-FORMING REGION (2009, methodology): “Several stars below the boundaries in Figure 19 have been previously recognized as possible transitional systems, consisting of CS Cha, T35, C7-1, CHXR 22E, CHXR 71, and CHXR 76 (Takami et al. 2003; Damjanov et al. 2007; Espaillat et al. 2007a; Luhman et al. 2008a; Kim et al. 2009).”
Stellar, brown dwarf and multiple star properties from a radiation hydrodynamical simulation of star cluster formation (2011, background): “…minimum mass is also greater than the estimated masses of some objects observed in star-forming regions (Zapatero Osorio et al. 2000, 2002; Kirkpatrick et al. 2001, 2006; Lodieu et al. 2008; Luhman et al. 2008, 2009b; Bihain et al. 2009; Burgess et al. 2009; Weights et al. 2009; Quanz et al. 2010).”
YOUNG L DWARFS IDENTIFIED IN THE FIELD: A PRELIMINARY LOW-GRAVITY, OPTICAL SPECTRAL SEQUENCE FROM L0 TO L5 (2008, background): “That said, optical spectroscopy has revealed several candidate members of σ Orionis, Lupus, Chamaeleon I, and Chamaeleon II to have early-L spectral types (Barrado y Navascués et al. 2001; Jayawardhana & Ivanov 2006; Luhman et al. 2008; Luhman & Muench 2008).”
Star and Protoplanetary Disk Properties in Orion's Suburbs (2009, methodology): “21 we also show the disk frequencies for IC 348 as found by Lada et al. (2006) and Chamaeleon I as found by Luhman et al. (2008).”