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J/A+A/599/A37       YSO candidates in IRAS 20319+3958           (Djupvik+, 2017)

Globules and pillars in Cygnus X. II. Massive star formation in the globule IRAS 20319+3958. Djupvik A.A., Comeron F., Schneider N. <Astron. Astrophys. 599, A37 (2017)> =2017A&A...599A..37D (SIMBAD/NED BibCode)
ADC_Keywords: Infrared sources ; Globules ; YSOs ; Photometry, VRI ; Photometry, infrared ; Photometry, millimetric/submm Keywords: ISM: clouds - stars: formation - ISM: individual objects: IRAS 20319+3958 - ISM: individual objects: Cygnus X Abstract: Globules and pillars, impressively revealed by the Spitzer and Herschel satellites, for example, are pervasive features found in regions of massive star formation. Studying their embedded stellar populations can provide an excellent laboratory to test theories of triggered star formation and the features that it may imprint on the stellar aggregates resulting from it. We studied the globule IRAS 20319+3958 in Cygnus X by means of visible and near-infrared imaging and spectroscopy, complemented with mid-infrared Spitzer/IRAC imaging, in order to obtain a census of its stellar content and the nature of its embedded sources. Our observations show that the globule contains an embedded aggregate of about 30 very young (≲1Myr) stellar objects, for which we estimate a total mass of ∼90M. The most massive members are three systems containing early B-type stars. Two of them most likely produced very compact HII regions, one of them being still highly embedded and coinciding with a peak seen in emission lines characterising the photon dominated region (PDR). Two of these three systems are resolved binaries, and one of those contains a visible Herbig Be star. An approximate derivation of the mass function of the members of the aggregate gives hints of a slope at high masses shallower than the classical Salpeter slope, and a peak of the mass distribution at a mass higher than that at which the widely adopted log-normal initial mass function peaks. The emission distribution of H2 and Brackett gamma, tracing the PDR and the ionised gas phase, respectively, suggests that molecular gas is distributed as a shell around the embedded aggregate, filled with centrally-condensed ionised gas. Both, the morphology and the low excitation of the HII region, indicate that the sources of ionisation are the B stars of the embedded aggregate, rather than the external UV field caused by the O stars of Cygnus OB2. The youth of the embedded cluster, combined with the isolation of the globule, suggests that star formation in the globule was triggered by the passage of the ionisation front. Description: Table 3 contains positions and photometry in V, R, I, J, H, Ks, [3.6], [4.5], [5.8] and [8.0] of 144 YSO candidates around the globule IRAS 20319+3958. The VRI magnitudes and their errors are obtained with CAMELOT/IAC80 (Tenerife), the JHKs magnitudes and their errors are obtained with Omega2000/3.5m CAHA telescope (Calar Alto observatory), except for a few very bright and/or unresolved sources for which NOTCam/NOT (La Palma) is used. The IRAC/Spitzer magnitudes and errors are also given. The third last column gives a flag that shows either the YSO class or the YSO selection method. The naming used in the paper for the three brightest sources in the globule (A, B and C), of which two are binaries, are given in the second last column. The last column gives a photometry flag. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table3.dat 167 144 YSO candidates
See also: J/AJ/150/191 : IR photometry of YSOs in Cygnus-X DR15 (Rivera-Galvez+, 2015) Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 3 I3 --- ID [1/144] Identification number 5- 15 F11.7 deg RAdeg Right ascension (J2000) 17- 27 F11.7 deg DEdeg Declination (J2000) 29 A1 --- l_Vmag Upper limit flag on Vmag 30- 34 F5.2 mag Vmag ?=- CAMELOT/IAC80 V-band magnitude 37- 40 F4.2 mag e_Vmag ?=- Error in Vmag 42 A1 --- l_Rmag Upper limit flag on Rmag 43- 47 F5.2 mag Rmag ?=- CAMELOT/IAC80 R-band magnitude 50- 53 F4.2 mag e_Rmag ?=- Error in Rmag 55- 59 F5.2 mag Imag ?=- CAMELOT/IAC80 I-band magnitude 62- 65 F4.2 mag e_Imag ?=- Error in Imag 67 A1 --- l_Jmag Upper limit flag on Jmag 68- 72 F5.2 mag Jmag Omega2000/3.5m J-band magnitude 75- 78 F4.2 mag e_Jmag ?=- Error in Jmag 80- 84 F5.2 mag Hmag Omega2000/3.5m H-band magnitude 87- 90 F4.2 mag e_Hmag Error in Hmag 92- 96 F5.2 mag Ksmag Omega2000/3.5m Ks-band magnitude 99-102 F4.2 mag e_Ksmag Error in Ksmag 104 A1 --- l_[3.6] Upper limit flag on [3.6] 105-109 F5.2 mag [3.6] ?=- IRAC [3.6] magnitude 112-115 F4.2 mag e_[3.6] ?=- Error in [3.6] 117 A1 --- l_[4.5] Upper limit flag on [4.5] 118-122 F5.2 mag [4.5] ?=- IRAC [4.5] magnitude 125-128 F4.2 mag e_[4.5] ?=- Error in [4.5] 130 A1 --- l_[5.8] Upper limit flag on [5.8] 131-135 F5.2 mag [5.8] ?=- IRAC [5.8] magnitude 138-141 F4.2 mag e_[5.8] ?=- Error in [5.8] 143 A1 --- l_[8.0] Upper limit flag on [8.0] 144-148 F5.2 mag [8.0] ?=- IRAC [8.0] magnitude 151-154 F4.2 mag e_[8.0] ?=- Error in [8.0] 156 I1 --- fYSO [1/5] YSO type/selection criteria (1) 158-161 A4 --- Name Other name used in this paper 163-167 A5 --- fPhot [abcde ,] Photometric flag(s) (2)
Note (1): YSO class or selection criterion: 1 = Class I 2 = Class II 4 = Selection criterion is excess in Ks-[4.5] index 5 = Selection criterion is excess in H-Ks index Note (2): Photometry flags for one or more bands: a = Lower magnitude limit for VRI if mag errors n/a b = Lower magnitude limit for JHK if mag errors n/a c = NOTCam JHKs photometry used instead of Omega2000 JHKs d = IRAC fluxes saturated, upper magnitude limit if no mag error e = IRAC unresolved source
Acknowledgements: Anlaug Amanda Djupvik, amanda(at) References: Schneider et al., Paper I 2016A&A...591A..40S
(End) Patricia Vannier [CDS] 16-Dec-2016
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