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 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 2006AJ....131.1163S, Cat. VII/233) H and Ks band
photometry of background stars.
Objects:
-----------------------------------------------------------
RA (ICRS) DE Designation(s)
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22 55 00.0 +62 35 00 Cep OB3b = NAME Ass Cep OB 3b
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 149 76 Sources used to determine Extinction Law
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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
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Bytes Format Units Label Explanations
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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
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 21-Jun-2017