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 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 2015A&A...576A..78K, Smette et al., 2015A&A...576A..77S 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/* . 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 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)uantof.cl
(End) Sebastian Ramirez Alegria [UAUA Chile], Patricia Vannier [CDS] 16-Feb-2018