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J/ApJ/722/1226    IR photometry in λ Orionis cluster   (Hernandez+, 2010)

Spitzer observations of the λ Orionis cluster. II. Disks around solar-type and low-mass stars. Hernandez J., Morales-Calderon M., Calvet N., Hartmann L., Muzerolle J., Gutermuth R., Luhman K.L., Stauffer J. <Astrophys. J., 722, 1226-1239 (2010)> =2010ApJ...722.1226H
ADC_Keywords: Photometry, infrared ; Radial velocities ; YSOs ; Clusters, open Keywords: infrared: stars - open clusters and associations: individual (λ Orionis Cluster) - protoplanetary disks - stars: formation - stars: pre-main sequence Abstract: We present IRAC/MIPS Spitzer Space Telescope observations of the solar-type and the low-mass stellar population of the young (∼5Myr) λ Orionis cluster. Combining optical and Two Micron All Sky Survey photometry, we identify 436 stars as probable members of the cluster. Given the distance (450pc) and the age of the cluster, our sample ranges in mass from 2M to objects below the substellar limit. With the addition of the Spitzer mid-infrared data, we have identified 49 stars bearing disks in the stellar cluster. Using spectral energy distribution slopes, we place objects in several classes: non-excess stars (diskless), stars with optically thick disks, stars with "evolved disks" (with smaller excesses than optically thick disk systems), and "transitional disk" candidates (in which the inner disk is partially or fully cleared). The disk fraction depends on the stellar mass, ranging from ∼6% for K-type stars (RC-J<2) to ∼27% for stars with spectral-type M5 or later (RC-J>4). We confirm the dependence of disk fraction on stellar mass in this age range found in other studies. Regarding clustering levels, the overall fraction of disks in the λ Orionis cluster is similar to those reported in other stellar groups with ages normally quoted as ∼5Myr. Description: We are using the Spitzer Space Telescope observations from Paper I (2009ApJ...707..705H), which include images from the Infrared Array Camera (IRAC) with its four photometric channels (3.6, 4.5, 5.8, and 8.0um) and from the 24um band of the Multiband Imaging Spectrometer for Spitzer (MIPS). The region with the complete IRAC data set has a size of ∼57.6'x54.6' centered at λ Orionis. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 98 205 Compiled membership information of the λ Orionis Cluster table2.dat 122 436 Photometric candidates of the λ Orionis Cluster table3.dat 115 41 Additional sources with infrared excesses
See also: II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003) J/A+A/536/A63 : Collinder 69 very low mass stars (Bayo+, 2011) J/A+A/530/A150 : XMM obervations of λ Ori cluster (Franciosini+, 2011) J/A+A/526/A21 : Collinder 69 X-ray sources (Barrado+, 2011) J/A+A/488/167 : Low-mass stars in σ Ori and λ Ori (Sacco+, 2008) J/MNRAS/385/2210 : Spectroscopy around lam Ori and sig Ori (Maxted+, 2008) J/A+A/492/277 : Analysis of Collinder 69 stars with VOSA (Bayo+, 2008) J/ApJ/664/481 : Photometry of Collinder 69 (Barrado y Navascues+ 2007) J/ApJ/610/1064 : Substellar population of lam Ori (Barrado y Navascues+, 2004) J/AJ/123/387 : VRI photometry of lam Ori star-forming region (Dolan+, 2002) J/AJ/121/2124 : λ Ori pre-main-sequence stars photometry (Dolan+, 2001) J/AJ/118/2409 : VRI photometry of λ Ori PMS stars (Dolan+, 1999) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 4 I4 --- ID [936/7971] Identification number 6- 13 F8.5 deg RAdeg Right Ascension in decimal degrees (J2000) 15- 22 F8.5 deg DEdeg Declination in decimal degrees (J2000) 24- 35 A12 -- Name Source name (LOriNNN, see ref. 2 or DMNN, see ref. 1) 37- 46 A10 --- SpType MK spectral type 48- 50 A3 --- r_SpType Reference(s) for SpType (1) 52- 56 F5.2 km/s RV1 ? Radial velocity 1 57 A1 --- --- [,] 58- 62 F5.2 km/s RV2 ? Radial velocity 2 63 A1 --- --- [,] 64- 68 F5.2 km/s RV3 ? Radial velocity 3 70- 74 A5 --- r_RV Reference(s) for radial velocities (1) 76- 78 A3 --- LiI Li I present? (Y according to r_LiI) 80- 82 A3 --- r_LiI Reference(s) for LiI (1) 84- 94 A11 --- Memb Membership details (G1) 96- 98 A3 --- Mm Membership flag (2)
Note (1): Reference as follows: 1 = Dolan & Mathieu (2001, Cat. J/AJ/121/2124; <[DM99] NNN> in Simbad); 2 = Barrado y Navascues et al. (2007, Cat. J/ApJ/664/481; <lOri-CFHT NNN> in Simbad); 3 = Maxted et al. (2008, Cat. J/MNRAS/385/2210; [MJO2008] JHHMMSS.s+DDMMSS> in Simbad); 4 = Sacco et al. (2008, Cat. J/A+A/488/167; <[SFR2008] LNN> in Simbad); 5 = Dolan & Mathieu (2001, Cat. J/AJ/121/2124); 6 = Barrado y Navascues et al. (2007, Cat. J/ApJ/664/481); 7 = Sacco et al. (2008, Cat. J/A+A/488/167). Note (2): Membership flag as follows: m1 = radial velocity members with LiI in absorption; m2 = radial velocity members with no LiI information; m3 = stars with LiI in absorption and radial velocity out of member range; m4 = both spectral type and photometric data in agreement with cluster sequence; m5 = photometric members; nm1 = non-members based on photometric analysis; nm2 = non-members based in spectroscopic analysis.
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 4 I4 --- ID [30/7968] Identification number 6- 21 A16 --- 2MASS 2MASS identification number 23- 30 F8.5 deg RAdeg Right Ascension in decimal degrees (J2000) 32- 39 F8.5 deg DEdeg Declination in decimal degrees (J2000) 41- 45 F5.2 mag [3.6] Spitzer/IRAC 3.6 micron band magnitude 47- 50 F4.2 mag e_[3.6] Uncertainty in [3.6] 52- 56 F5.2 mag [4.5] Spitzer/IRAC 4.5 micron band magnitude 58- 61 F4.2 mag e_[4.5] Uncertainty in [4.5] 63- 68 F6.2 mag [5.8] ?=100 Spitzer/IRAC 5.8 micron band magnitude 70- 74 F5.2 mag e_[5.8] ?=99.99 Uncertainty in [5.8] 76- 81 F6.2 mag [8.0] ?=100 Spitzer/IRAC 8.0 micron band magnitude 83- 88 F6.2 mag e_[8.0] ?=100 Uncertainty in [8.0] 90- 94 F5.2 mJy F24 ? Spitzer/MIPS 24 micron flux density 96- 99 F4.2 mJy e_F24 ? Uncertainty in F24 101-108 A8 --- DType Disk type (1) 110-112 A3 --- f_DType Flag(s) on DType (2) 114-122 A9 --- Memb Membership details (G1)
Note (1): Disk type as follows: Thk = star with an optically thick disk; TD = transitional disk candidate; PTD = pre transitional disk candidate; EV = star with an evolved (flat) disk; diskless = star with no infrared excesses. Note (2): Flag as follows: 1 = stars with uncertain 24 micron excess. 2 = stars with uncertain 8 micron excess. 3 = stars without 24 micron counterpart. 4 = Faint stars with not reliable excesses at 5.8 micron and 8.0 micron. 5 = Star with moderate IR excess at 8.0 micron but the 24 micron flux is consistent with the photospheric fluxes. 6 = Classified as evolved disk star from the IRAC SED slope. 7 = The star λ Orionis may mask the detection at 24 micron.
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 4 I4 --- ID [241/7615] Identification number 6- 21 A16 --- 2MASS 2MASS identification (HHMMSSss+DDMMSSs) 23- 30 F8.5 deg RAdeg Right ascension in decimal degrees (J2000) 32- 39 F8.5 deg DEdeg Declination in decimal degrees (J2000) 41- 46 F6.3 mag [3.6] Spitzer/IRAC 3.6um band magnitude 48- 52 F5.3 mag e_[3.6] Uncertainty in [3.6] 54- 59 F6.3 mag [4.5] Spitzer/IRAC 4.5um band magnitude 61- 65 F5.3 mag e_[4.5] Uncertainty in [4.5] 67- 72 F6.3 mag [5.8] Spitzer/IRAC 5.8um band magnitude 74- 78 F5.3 mag e_[5.8] Uncertainty in [5.8] 80- 85 F6.3 mag [8.0] Spitzer/IRAC 8.0um band magnitude 87- 91 F5.3 mag e_[8.0] Uncertainty in [8.0] 93- 99 F7.2 mJy F24 Spitzer/MIPS 24um flux density 101-106 F6.2 mJy e_F24 F24 uncertainty 108-115 A8 --- Comm Comment (Galaxy or Stellar?)
Global notes: Note (G1): Membership reference as follows: 1a = stars with LiI in absorption from Dolan & Mathieu (2001, Cat. J/AJ/121/2124) and radial velocity in the members range 1b = stars with LiI in absorption from Dolan & Mathieu (2001, Cat. J/AJ/121/2124) and radial velocity out of the members range 2a = Flag Y from Barrado y Navascues et al. (2007, Cat. J/ApJ/664/481) 2b = Flag Y? from Barrado y Navascues et al. (2007, Cat. J/ApJ/664/481) 2c = Flag N? from Barrado y Navascues et al. (2007, Cat. J/ApJ/664/481) 2d = Flag N from Barrado y Navascues et al. (2007, Cat. J/ApJ/664/481) 3a = members from the radial velocity analysis of Maxted et al. (2008, Cat. J/MNRAS/385/2210) 3b = non-members from the radial velocity analysis of Maxted et al. (2008, Cat. J/MNRAS/385/2210) 4a = member from the LiI and radial velocity analysis of Sacco et al. (2008, Cat. J/A+A/488/167) 4b = non-member from the LiI and radial velocity analysis of Sacco et al. (2008, Cat. J/A+A/488/167)
History: From electronic version of the journal References: Hernandez et al. Paper I. 2009ApJ...707..705H
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 11-Jul-2012
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