Spitzer Observations of IC 348: The Disk Population at 2-3 Million Years

By C. Lada, August Muench, K. Luhman, L. Allen, L. Hartmann, T. Megeath, P.Myers, G. Fazio, K. Wood, J. Muzerolle and 3 more. 2005

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We present near- and mid-infrared photometry obtained with the Spitzer Space Telescope of ∼300 known members of the IC 348 cluster. We merge this photometry with existing ground-based optical and near-infrared photometry in order to construct optical-infrared spectral energy distributions (SEDs) for all the cluster members and present a complete atlas of these SEDs. We employ these observations to investigate both the frequency and nature of the circumstellar disk population in the cluster. The Spitzer observations span a wavelength range between 3.6 and 24 μm, corresponding to disk radii of ∼0.1-5 AU from the central star. The observations are sufficiently sensitive to enable the first detailed measurement of the disk frequency for very low mass stars at the peak of the stellar initial mass function. Using measurements of infrared excess between 3.6 and 8.0 μm, we find the total frequency of disk-bearing stars in the cluster to be 50% ± 6%. However, only 30% ± 4% of the member stars are surrounded by optically thick, primordial disks, while the remaining disk-bearing stars are surrounded by what appear to be optically thin, anemic disks. Both these values are below previous estimates for this cluster. The disk fraction appears to be a function of spectral type and stellar mass. The fraction of stars with optically thick disks ranges from 11% ± 8% for stars earlier than K6 to 47% ± 12% for K6-M2 stars to 28% ± 5% for M2-M6 stars. The disk longevity and thus conditions for planet formation appear to be most favorable for the K6-M2 stars, which are objects of comparable mass to the Sun for the age of this cluster. The optically thick disks around later type (>M4) stars appear to be less flared than the disks around earlier type stars. This may indicate a greater degree of dust settling and a more advanced evolutionary state for the late M disk population. Finally, we find that the presence of an optically thick dust disk is correlated with gaseous accretion, as measured by the strength of Hα emission. A large fraction of stars classified as classical T Tauri stars possess robust, optically thick disks, and very few such stars are found to be diskless. The majority (64%) of stars classified as weak-lined T Tauri stars are found to be diskless. However, a significant fraction (12%) of these stars are found to be surrounded by thick, primordial disks. These results suggest that it is more likely for dust disks to persist in the absence of active gaseous accretion than for active accretion to persist in the absence of dusty disks.

Subfields: Astronomy and Astrophysics

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Clustered and Triggered Star Formation in W5: Observations with Spitzer (2008, background): “Stellar sources not classified as either Class I or Class II by their IRAC or near-IR colors may still have red colors ([5.8] − [24] >1.5) and thus be candidate “cold disk” or “transition disk” objects—in other words: Class II objects with significant clearing of their inner disk region (see for exa”
RESOLVED IMAGES OF LARGE CAVITIES IN PROTOPLANETARY TRANSITION DISKS (2011, background): “…or “homologouslydepleted” - have relatively faint infrared excesses and often low accretion rates, but do not (yet) exhibit any compelling observational evidence for a dust-depleted cavity (Lada et al. 2006; Najita et al. 2007; Cieza et al. 2008, 2010; Currie et al. 2009; Currie & Kenyon 2009).”
WFCAM, Spitzer/IRAC and SCUBA observations of the massive star-forming region DR21/W75 - I. The collimated molecular jets (2006, methodology): “More recently, Lada et al. (2006) have applied this classification scheme to Spitzer photometry of YSOs in the low-mass star forming region IC 348.”
On the diversity and statistical properties of protostellar discs (2018, background): “For example, in IC348 Lada et al. (2006) find that ≈ 20% are discless while, on the other hand, 12% of WTTS are found to have thick, primordial discs.”
WIDE-FIELD INFRARED SURVEY EXPLORER OBSERVATIONS OF THE EVOLUTION OF MASSIVE STAR-FORMING REGIONS (2012, background): “With their weak infrared excesses above the photosphere, they often resemble “anemic” disks (Lada et al. 2006) with excess at all infrared wavelengths but at a level below that of optically thick T Tauri stars or Herbig AeBe star accretion disks.”
A SPITZER SURVEY OF YOUNG STELLAR CLUSTERS WITHIN ONE KILOPARSEC OF THE SUN: CLUSTER CORE EXTRACTION AND BASIC STRUCTURAL ANALYSIS (2009, methodology): “Disk evolution might be a significant effect in IC 348 for example, reducing disk flaring as dust has time to settle to the mid-plane in the majority of disks (Lada et al. 2006).”
A Spitzer Space Telescope Study of Disks in the Young σ Orionis Cluster (2007, methodology): “IRAC SED Slope Lada et al. (2006) showed the utility of characterizing excess infrared emission using the IRAC SED slope determined from the 3:6½ 8:0½ color, where ¼ d log kFkð Þ/d log kð Þ.”
ALMA OBSERVATIONS OF CIRCUMSTELLAR DISKS IN THE UPPER SCORPIUS OB ASSOCIATION (2016, background): “…dust disks surrounding an exposed stellar photosphere (e.g. Gutermuth et al. 2004; Hartmann et al. 2005; Megeath et al. 2005; Carpenter et al. 2006; Lada et al. 2006; Sicilia-Aguilar et al. 2006; Balog et al. 2007; Barrado y Navascués et al. 2007; Cieza & Baliber 2007; Dahm & Hillenbrand 2007;…”
Dust filtration at gap edges: Implications for the spectral energy distributions of discs with embedded planets (2006, background): “As more data comes in from Spitzer, the number of disc systems showing evidence for inner holes is increasing (Lada et al. 2006; Muzerolle et al. 2006).”
FORMATION AND EVOLUTION OF PLANETARY SYSTEMS: PROPERTIES OF DEBRIS DUST AROUND SOLAR-TYPE STARS (2008, background): “…et al. 2006; Cieza et al. 2007), about half of solar mass stars at age of 1-3 Myr remain surrounded by primordial disks whether traced by emission at 3-8µm (Haisch, Lada, & Lada 2001; Hernández et al. 2007), 10µm (Mamajek et al. 2004), or 24µm (e.g. Lada et al. 2006; Damjanov et al. 2007).”
Accretion dynamics and disk evolution in NGC 2264: a study based on the Corot photometric observations (2010, methodology): “We used theαIRAC index, which represents the slope of the spectral energy distribution between 3.6µm and 8µm, to classify the inner disk structure of the observed systems, following thecriteria proposed by Lada et al. (2006).”
Interpreting Spectral Energy Distributions from Young Stellar Objects. I. A Grid of 200,000 YSO Model SEDs (2006, methodology): “Both definitions have been used in the literature (e.g. Myers et al. 1987 and Kenyon & Hartmann 1995 use α[λ1 &λ2], while Haisch et al. 2001, Lada et al. 2006, and Jørgensen et al. 2006 use α[λ1 →λ2]), and in some cases it is not explicitely stated which choice has been made.”
Star and Protoplanetary Disk Properties in Orion's Suburbs (2009, methodology): “Following Lada et al. (2006), we divide the sample in six spectral type bins.”
Spitzer Observations of NGC 1333: A Study of Structure and Evolution in a Nearby Embedded Cluster (2007, methodology): “There are now several methods in the literature to identify and classify YSOs with such photometry (cf. Allen et al. 2004; Megeath et al. 2004; Lada et al. 2006).”
THE DISTANCE TO NGC 2264 (2009, methodology): “Following Lada et al. (2006), we used an IRAC [3.6 - 8] color cut to identify classical T Tauri stars in our sample; when these CTTSs are excluded from our sample, the best fit distance to NGC 2264 increases to ∼950 pc.”
The Formation and Early Evolution of Low-Mass Stars and Brown Dwarfs (2012, background): “…of spectral type, which acts as a proxy for stellar mass. Figure 8 shows some of the best available disk fractions in terms of number statistics and completeness at low masses, which apply to Taurus, Chamaeleon I, and IC 348 (Lada et al. 2006, Luhman et al. 2005a, 2008, 2010, Muench et al. 2007).”