J/ApJ/733/113 IRAC observations of IC 1795 (Roccatagliata+, 2011)
Disk evolution in OB associations: deep Spitzer/IRAC observations of IC 1795. Roccatagliata V., Bouwman J., Henning T., Gennaro M., Feigelson E., Kim J.S., Sicilia-Aguilar A., Lawson W.A. <Astrophys. J., 733, 113 (2011)> =2011ApJ...733..113R
ADC_Keywords: YSOs ; Associations, stellar ; Photometry, infrared ; X-ray sources Keywords: ISM: individual objects (W3) - X-rays: stars - open clusters and associations: individual (W3 IC1795) - protoplanetary disks - stars: formation - stars: pre-main sequence Abstract: We present a deep Spitzer/Infrared Array Camera (IRAC) survey of the OB association IC 1795 carried out to investigate the evolution of protoplanetary disks in regions of massive star formation. Combining Spitzer/IRAC data with Chandra/Advanced CCD Imaging Spectrometer observations, we find 289 cluster members. An additional 340 sources with an infrared excess, but without X-ray counterpart, are classified as cluster member candidates. Both surveys are complete down to stellar masses of about 1M☉. We present pre-main-sequence isochrones computed for the first time in the Spitzer/IRAC colors. The age of the cluster, determined via the location of the Class III sources in the [3.6]-[4.5]/[3.6] color-magnitude diagram, is in the range of 3-5Myr. As theoretically expected, we do not find any systematic variation in the spatial distribution of disks within 0.6pc of either O-type star in the association. However, the disk fraction in IC 1795 does depend on the stellar mass: sources with masses >2M☉ have a disk fraction of ∼20%, while lower mass objects (2-0.8M☉) have a disk fraction of ∼50%. This implies that disks around massive stars have a shorter dissipation timescale. Description: IC 1795 was observed in 2007 September with all 4 IRAC channels centered at 3.6um, 4.5um, 5.8um, 8.0um, respectively. Our X-ray catalog was generated from a mosaic of Chandra observations consisting of the seven exposures of W3 presented by Feigelson & Townsley (2008ApJ...673..354F) and an additional exposure of IC 1795. This is a 50.0ks exposure obtained on 2007 December 4 centered on J022633.6+620035.9 with the 4-CCD ACIS Imaging Array. Out of 593 sources detected in Spitzer/IRAC ch1 and ch2 without an X-ray counterpart, we find 248 IRAC excess sources ([3.6]-[4.5]≥0.2); classified as cluster member candidates (tables 4 and 5). The final catalog of the IC 1795 cluster members is in Table 3 (and 2). File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 74 277 Spitzer/IRAC sources with Chandra counterparts table3.dat 128 277 Optical, near-infrared and IRAC/Spitzer fluxes of the IRAC/Spitzer sources with X-ray counterpart table4.dat 74 248 Cluster member candidates: designation and positions of IRAC sources with excess without X-ray counterpart table5.dat 128 248 Cluster member candidates: IRAC sources with excess without X-ray counterpart
See also: B/chandra : The Chandra Archive Log (CXC, 1999-2012) II/297 : AKARI/IRC mid-IR all-sky Survey (ISAS/JAXA, 2010) VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006) II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003) J/A+A/514/A2 : AKARI/HIP and AKARI/2MASS samples (Ita+, 2010) J/A+A/501/539 : RMS survey. 6cm observations of YSOs (Urquhart+, 2009) J/ApJ/660/1532 : Spitzer/IRAC-MIPS survey of NGC 2244 (Balog+, 2007) J/ApJ/654/338 : Spitzer photometry in W3 molecular cloud (Ruch+, 2007) J/AJ/129/393 : UBV photometry in W3 (Oey+, 2005) J/AJ/126/1423 : MSX 8.3um fluxes of star-forming regions (Kraemer+, 2003) J/A+AS/124/205 : W3 star-forming region 345 GHz survey (Helmich+ 1997) Byte-by-byte Description of file: table.dat
Bytes Format Units Label Explanations
1- 16 A16 --- ID Identification; IRAC- (HHMMSSss+DDMMSSs) 18 A1 --- f_ID Flag on source (1) 20- 28 F9.6 deg RAdeg Right Ascension in decimal degrees (J2000) 30- 33 F4.2 10-4deg e_RAdeg Error in RAdeg 35- 43 F9.6 deg DEdeg Declination in decimal degrees (J2000) 45- 48 F4.2 10-4deg e_DEdeg Error in DEdeg 50 A1 --- Exc [X~-] Infrared excess code (2) 52- 74 A23 --- Disk Disk classification (only for table 2)
Note (1): Flag as follows: a = Source position in IRAC/channel 2. b = Source position in IRAC/channel 3. c = The counterparts at different wavelengths were found using a different matching procedure. d = IRAC source with 2 X-ray counterparts ("X binary"). e = IRAC source with 3 X-ray counterparts. Note (2): IR excess code (in table2 only) as follows: X = [3.6]-[4.5]>0.2mag; - = [3.6]-[4.5]<0.1mag; ∼ = 0.1<[3.6]-[4.5]<0.2mag.
Byte-by-byte Description of file: table.dat
Bytes Format Units Label Explanations
1- 16 A16 --- ID Identification; IRAC- (HHMMSSss+DDMMSSs) 18- 23 F6.4 mJy FV ? V band flux density (3) 25- 31 F7.4 mJy FI ? I band flux density (3) 33- 41 F9.4 mJy FJ ? 2MASS J band flux density (4) 43- 50 F8.4 mJy FH ? 2MASS H band flux density (4) 52- 60 F9.4 mJy FK ? 2MASS Ks band flux density (4) 62- 70 F9.4 mJy F3.6 ? Spitzer/IRAC 3.6 micron band flux density 72- 77 F6.4 mJy e_F3.6 ? Uncertainty in F3.6 (5) 79- 87 F9.4 mJy F4.5 ? Spitzer/IRAC 4.5 micron band flux density 89- 94 F6.4 mJy e_F4.5 ? Uncertainty in F4.5 (5) 96-104 F9.4 mJy F5.8 ? Spitzer/IRAC 5.8 micron band flux density 106-111 F6.4 mJy e_F5.8 ? Uncertainty in F5.8 (5) 113-121 F9.4 mJy F8.0 ? Spitzer/IRAC 8.0 micron band flux density 123-128 F6.4 mJy e_F8.0 ? Uncertainty in F8.0 (5)
Note (3): In table 3, from Jose et al. (in prep). Note (4): From the 2MASS catalog (Skrutskie et al. 2006, Cat. VII/233), selecting only sources flagged 'AAA'. Note (5): The IRAC flux errors refer to the covariance matrix calculated from the "best-fit" of the PRF (Point Response Function) to the data and do not include calibration uncertainty (∼10% of the flux).
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 14-Nov-2012
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