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J/A+A/614/A116      Masgomas-6 near-IR spectra          (Ramirez Alegria+, 2018)

Identifying two groups of massive stars aligned in the l∼38° Galactic direction. Ramirez Alegria S., Herrero A., Rubke K., Marin-Franch A., Garcia M., Borissova J. <Astron. Astrophys. 614, A116 (2018)> =2018A&A...614A.116R (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Infrared sources ; Spectra, infrared Keywords: infrared: stars - open clusters and associations: general - stars: early-type - stars: massive - stars: Wolf-Rayet - supergiants Abstract: Recent near-infrared data have contributed to unveiling massive and obscured stellar populations in both new and previously known clusters in our Galaxy. These discoveries have lead us to view the Milky Way as an active star-forming machine. We look for young massive cluster candidates as over-densities of OB-type stars. The first search, focused on the Galactic direction l=38, resulted in the detection of two objects with a remarkable population of OB-type star candidates. With a modified version of the friends-of-friends algorithm AUTOPOP and using 2MASS and UKIDSS-GPS near-infrared (J, H, and K) photometry for one of our cluster candidates (Masgomas-6) we selected 30 stars for multi-object and long-slit H and K band spectroscopy. With the spectral classification and the near-infrared photometric data, we derive individual distance, extinction, and radial velocity. Of the 30 spectroscopically observed stars, 20 are classified as massive stars, including OB-types (dwarfs, giants and supergiants), two red supergiants, two Wolf-Rayets (WR122-11 and the new WR122-16), and one transitional object (the LBV candidate IRAS 18576+0341). The individual distances and radial velocities do not agree with a single cluster, indicating that we are observing two populations of massive stars in the same line of sight: Masgomas-6a and Masgomas-6b. The first group of massive stars, located at 3.9kpc, contains both Wolf-Rayets and most of the OB-dwarfs; the second group, located at 9.6kpc, hosts the LBV candidate and an evolved population of supergiants. We are able to identify massive stars at two Galactic arms, but we cannot clearly identify whether these massive stars form clusters or associations. Description: LIRIS individual spectra (multi-object and long-slit) used for the analysis of Masgomas-6. Spectra are normalized using IRAF continuum task and wavelength calibrated using LIRIS Ar and Xe lamps. Telluric correction was completed using MOLECTFIT (Kausch et al., 2015A&A...576A..78K, Smette et al., 2015A&A...576A..77S). File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table3.dat 135 30 Spectroscopically observed stars list.dat 84 30 List of fits spectra fits/* 0 30 Individual fits spectra
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 2 A2 --- Type Massive (MS) or Field (FS) stars 4- 5 I02 --- Seq Sequential number 7- 18 I12 --- UKIDSS Identification number from the UKIDSS GPS catalogue 20- 27 F8.4 deg RAdeg Right ascension (J2000) 29- 37 F9.5 deg DEdeg Declination (J2000) 39- 44 F6.3 mag Jmag J magnitude 46- 50 F5.3 mag e_Jmag rms uncertainty on Jmag 52- 57 F6.3 mag Hmag H magnitude 59- 63 F5.3 mag e_Hmag rms uncertainty on Hmag 65- 70 F6.3 mag Kmag Ks magnitude 72- 76 F5.3 mag e_Kmag rms uncertainty on Ksmag 78- 87 A10 --- SpType Spectral type 89- 92 F4.2 mag AK ?=- Estimated extinction 93 A1 --- --- [+] 94- 97 F4.2 mag E_AK ? Error on AK (upper value) 98 A1 --- --- [-] 99-102 F4.2 mag e_AK ? Error on AK (lower value) 104-108 F5.2 kpc Dist ? Distance 109 A1 --- --- [+] 110-113 F4.2 kpc E_Dist ? Error on Dist (upper value) 114 A1 --- --- [-] 115-118 F4.2 kpc e_Dist ? Error on Dist (lower value) 119 A1 --- n_Dist [a] Note on Dist (1) 121-123 I3 km/s RV ? Radial velocity 125-127 I3 km/s e_RV ? rms uncertainty on RV 129-131 I3 --- SNRH Signal-to-noise ratio measured for the H-band spectrum 132 A1 --- --- [-] 133-135 I3 --- SNRK ? Signal-to-noise ratio measured for the K-band spectrum
Note (1): a: Distance estimated by Ueta et al. (2001ApJ...548.1020U).
Byte-by-byte Description of file: list.dat
Bytes Format Units Label Explanations
1- 9 F9.5 deg RAdeg Right Ascension of center (J2000) 10- 18 F9.5 deg DEdeg Declination of center (J2000) 20- 21 I02 --- Seq Object identification used in article 23- 26 I4 --- Nx Number of points 28- 34 F7.1 0.1nm blambda Lower value of wavelength interval 36- 42 F7.1 0.1nm Blambda Upper value of wavelength interval 44- 50 F7.5 0.1nm dlambda Spectral resolution 52- 53 I2 Kibyte size Size of FITS file 55- 65 A11 --- FileName Name of FITS file, in subdirectory fits 67- 84 A18 --- Title Title of the FITS file
Acknowledgements: Sebastian Ramirez Alegria, sebastian.ramirez(at)
(End) Sebastian Ramirez Alegria [UAUA Chile], Patricia Vannier [CDS] 16-Feb-2018
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