J/A+A/633/A155 M8, G333.6-0.2 and NGC6357 young stars (Ramirez-Tannus+, 2020)
The young stellar content of the giant HII regions M8, G333.6-0.2, and
NGC6357 with VLT/KMOS.
Ramirez-Tannus M.C., Poorta J., Bik A., Kaper L., de Koter A., De Ridder J.,
Beuther H., Brandner W., Davies B., Gennaro M., Guo D., Henning T., Linz H.,
Naylor T., Pasquali A., Ramirez-Agudelo O.H., Sana H.
<Astron. Astrophys. 633, A155 (2020)>
=2020A&A...633A.155R 2020A&A...633A.155R (SIMBAD/NED BibCode)
ADC_Keywords: H II regions ; YSOs ; Spectra, infrared
Keywords: HII regions - stars: pre-main sequence - stars: formation -
X-rays: stars - infrared: stars
Abstract:
The identification and characterisation of populations of young
massive stars in (giant) HII regions provides important
constraints on i) the formation process of massive stars and their
early feedback on the environment, and ii) the initial conditions for
population synthesis models predicting the evolution of ensembles of
stars.
We identify and characterise the stellar populations of the following
young giant HII regions: M8, G333.6-0.2, and NGC6357.
We have acquired H- and K-band spectra of around 200 stars using The
K-band Multi Object Spectrograph (KMOS) on the ESO Very Large
Telescope. The targets for M8 and NGC6357 were selected from the
Massive Young Star-Forming Complex Study in Infrared and X-ray
(MYStIX), which combines X-ray observations with near-infrared and
mid-infrared data. For G333.6-0.2, the sample selection is based on
the near-infrared colours combined with X-ray data. We introduce an
automatic spectral classification method in order to obtain
temperatures and luminosities for the observed stars. We analysed the
stellar populations using their photometric, astrometric, and
spectroscopic properties and compared the position of the stars in the
Hertzprung-Russell diagram with stellar evolution models to constrain
their ages and mass ranges.
We confirm the presence of candidate ionising sources in the three
regions and report new ones, including the first spectroscopically
identified O stars in G333.6-0.2. In M8 and NGC6357, two populations
are identified: (i) OB main-sequence stars (M>5M☉) and (ii)
pre-main sequence stars (M~=0.5-5M☉). The ages of the clusters
are ∼1-3Myr, <3Myr, and 0.5-3Myr for M8, G333.6-0.2, and NGC6357,
respectively. We show that MYStIX selected targets have >90%
probability of being members of the HII region, whereas a selection
based on near infrared (NIR) colours leads to a membership probability
of only 70%.
Description:
We observed three HII regions with different mass ranges and
physical sizes: G333.6-0.2, M8, and NGC6357.
The observations presented here were obtained between April and August
2015 using the K-band Multi Object Spectrograph (KMOS) mounted at the
ESO Very Large Telescope (VLT).
KMOS consists of 24 deployable integral field units (IFUs) and three
spectrographs (Sharples et al., 2013Msngr.151...21S 2013Msngr.151...21S). The IFUs are
divided into three groups and the light is redirected into one of
three spectrographs, each spectrograph disperses the light of eight
IFUs. We divided the Hii regions in several fields and for each field
we took a long (300s) and a short (30s) exposure in order to cover the
faint (13<K<11mag) and bright (K<11mag) targets, respectively. For
each exposure we applied a 9-point dither pattern both for the H- and
the K-band grating.
The photometric data were taken from the MYStIX catalogue (Feigelson
et al., 2013, Cat. J/ApJS/209/26; King et al., 2013, Cat.
J/ApJS/209/28; Kuhn et al., 2013, Cat. 9) which includes the JHK-band
magnitudes from the United Kingdom Infra-red Telescope (UKIRT) wide
field camera (Lawrence et al., 2007MNRAS.379.1599L 2007MNRAS.379.1599L, Cat. II/314, Lucas
et al., 2008MNRAS.391..136L 2008MNRAS.391..136L, Cat. II/316) or from the 2MASS point
source catalogue (Skrutskie et al. 2006AJ....131.1163S 2006AJ....131.1163S, Cat. VII/233),
plus the four Spitzer IRAC bands (GLIMPSE; Benjamin et al.
2003PASP..115..953B 2003PASP..115..953B, Cat. II/293).
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
16 22 11 -50 05.6 G333.6-0.2 = SNR G333.6-00.2
18 03 37 -24 23.2 M8 = NAME Lagoon Nebula
17 26 30 -34 12 NGC6357 = CTB 40
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
g333.dat 184 39 G333.6-0.2 properties of the KMOS targets
m8.dat 173 81 M8 properties of the KMOS targets
ngc6357.dat 178 123 NGC6357 properties of the KMOS targets
sp/* . 243 Individual normalized spectra
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Byte-by-byte Description of file:*.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Name Source name in KMOS catalogue
9- 27 A19 --- X-ray Source X-ray ID (CXOU J), HHMMSS.ss+DDMMSS.sA
29- 41 A13 --- kSptype K-band spectral type
43 A1 --- r_kSptype [abe] Source of the spectral classification (1)
45- 46 I2 h RAh Right ascension (J2000)
48- 49 I2 min RAm Right ascension (J2000)
51- 56 F6.3 s RAs Right ascension (J2000)
58 A1 --- DE- Declination sign (J2000)
59- 60 I2 deg DEd Declination (J2000)
62- 63 I2 arcmin DEm Declination (J2000)
65- 69 F5.2 arcsec DEs Declination (J2000)
71- 76 F6.3 mag Jmag ?=- J-band magnitude
78- 82 F5.3 mag e_Jmag ?=- J-band magnitude error
84- 89 F6.3 mag Hmag H-band magnitude
91- 95 F5.3 mag e_Hmag H-band magnitude error
97-102 F6.3 mag Kmag K-band magnitude
104-108 F5.3 mag e_Kmag K-band magnitude error
110-115 F6.3 mag [3.6] ?=- 3.6um magnitude
117-121 F5.3 mag e_[3.6] ?=- 3.6um magnitude error
123-128 F6.3 mag [4.5] ?=- 4.5um magnitude
130-134 F5.3 mag e_[4.5] ?=- 4.5um magnitude error
136-141 F6.3 mag [5.8] ?=- 5.8um magnitude
143-147 F5.3 mag e_[5.8] ?=- 5.8um magnitude error
149-154 F6.3 mag [8.0] ?=- 8.0um magnitude
156-160 F5.3 mag e_[8.0] ?=- 8.0um magnitude error
161-184 A24 --- FileName Name of the spectrum file in subdirectory sp
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Note (1): Source of the spectral classification as follows:
b = both methods agree
e = classification by eye
a = automatic classification
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Byte-by-byte Description of file: sp/*
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Bytes Format Units Label Explanations
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1- 24 E24.19 um lambda Wavelength
25- 49 E25.19 --- NFlux Normalized flux
51- 74 E24.19 --- e_NFlux ? Error on normalized flux
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Acknowledgements:
Maria Claudia Ramirez-Tannus, ramirez(at)mpia.de
(End) Patricia Vannier [CDS] 13-Jan-2020