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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[24].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[35].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).
Nomenclature notes: These objects are <[RBH2011] IRAC JHHMMSSss+DDMMSSs> in Simbad. History: From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 14-Nov-2012
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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