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J/ApJ/786/113     Extinction law in the Cep OB3b young cluster    (Allen+, 2014)

An anomalous extinction law in the Cep OB3b young cluster: evidence for dust processing during gas dispersal. Allen T.S., Prchlik J.J., Megeath S.T., Gutermuth R.A., Pipher J.L., Naylor T., Jeffries R.D. <Astrophys. J., 786, 113 (2014)> =2014ApJ...786..113A (SIMBAD/NED BibCode)
ADC_Keywords: Associations, stellar ; Clusters, open ; Extinction ; Photometry, SDSS ; Photometry, infrared ; Spectral types Keywords: dust, extinction - ISM: clouds - open clusters and associations: individual: Cep OB3b Abstract: We determine the extinction law through Cep OB3b, a young cluster of 3000 stars undergoing gas dispersal. The extinction is measured toward 76 background K giants identified with MMT/Hectospec spectra. Color excess ratios were determined toward each of the giants using V and R photometry from the literature, g, r, i, and z photometry from the Sloan Digital Sky Survey and J, H, and Ks photometry from the Two Micron All Sky Survey. These color excess ratios were then used to construct the extinction law through the dusty material associated with Cep OB3b. The extinction law through Cep OB3b is intermediate between the RV=3.1 and RV=5 laws commonly used for the diffuse atomic interstellar medium and dense molecular clouds, respectively. The dependence of the extinction law on line-of-sight AV is investigated and we find the extinction law becomes shallower for regions with AV>2.5 mag. We speculate that the intermediate dust law results from dust processing during the dispersal of the molecular cloud by the cluster. Description: We use Johnson V and Cousins Rc (hereafter called VR) band photometry from the Isaac Newton Telescope (INT), compiled in the catalog of Littlefair et al. (2010, J/MNRAS/403/545). The R-band photometry was obtained using the Sloan r filter. It was calibrated against photometric standard stars measured in the Cousins Rc filter with an arbitrary zero point. Moderate resolution ((λ/Δλ)∼1000-2000, FWHM resolution of about 6 Å) optical spectra (covering 4000-9000 Å) were obtained for ∼1700 sources toward Cep OB3b using the multi-fiber spectrograph Hectospec on the MMT telescope. About 600 sources were selected for observation because they were determined to be possible cluster members (Allen et al. 2012, J/ApJ/750/125), based on indicators of youth, such as IR emission due to circumstellar dusty material and heightened X-ray activity. We use an extinction map from Allen et al. (2012, J/ApJ/750/125) to initially estimate the extinction toward each source. This map is derived using the 2MASS Point Source Catalog (Skrutskie et al. 2006AJ....131.1163S, Cat. VII/233) H and Ks band photometry of background stars. Objects: ----------------------------------------------------------- RA (ICRS) DE Designation(s) ----------------------------------------------------------- 22 55 00.0 +62 35 00 Cep OB3b = NAME Ass Cep OB 3b ----------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 149 76 Sources used to determine Extinction Law
See also: VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006) J/MNRAS/341/805 : UBVI CCD photometry of Cep OB3b (Pozzo+, 2003) J/MNRAS/403/545 : Young stars in Cepheus OB3b (Littlefair+, 2010) J/ApJ/750/125 : Spitzer imaging of Cepheus OB3b cluster (Allen+, 2012) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 2 I2 --- Index [1/76] Index number 4- 5 I2 h RAh Hour of Right Ascension (J2000) 7- 8 I2 min RAm Minute of Right Ascension (J2000) 10- 14 F5.2 s RAs Second of Right Ascension (J2000) 16- 17 I2 deg DEd Degree of the Declination (J2000) 19- 20 I2 arcmin DEm Arcminute of Declination (J2000) 22- 26 F5.2 arcsec DEs Arcsecond of Declination (J2000) 28- 32 F5.2 mag gmag SDSS g band magnitude 34- 37 F4.2 mag e_gmag Uncertainty in gmag 39- 43 F5.2 mag Vmag Literature V band magnitude 45- 48 F4.2 mag e_Vmag Uncertainty in Vmag 50- 54 F5.2 mag rmag SDSS r band magnitude 56- 59 F4.2 mag e_rmag Uncertainty in rmag 61- 65 F5.2 mag Rmag Literature R band magnitude 67- 70 F4.2 mag e_Rmag Uncertainty in Rmag 72- 76 F5.2 mag imag SDSS i band magnitude 78- 81 F4.2 mag e_imag Uncertainty in imag 83- 87 F5.2 mag zmag SDSS z band magnitude 89- 92 F4.2 mag e_zmag Uncertainty in zmag 94- 98 F5.2 mag Jmag 2MASS J band magnitude 100-103 F4.2 mag e_Jmag Uncertainty in Jmag 105-109 F5.2 mag Hmag 2MASS H band magnitude 111-114 F4.2 mag e_Hmag Uncertainty in Hmag 116-120 F5.2 mag Ksmag 2MASS Ks band magnitude 122-125 F4.2 mag e_Ksmag Uncertainty in Ksmag 127-130 F4.2 mag J-Ks The (J-Ks) color 132-135 F4.2 mag e_J-Ks Uncertainty in J-Ks 137-140 F4.2 mag AV The V band extinction 142-145 A4 --- SpType Spectral Type 147-149 F3.1 --- e_SpType Uncertainty in SpType
History: From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 21-Jun-2017
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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