J/A+A/677/A26 (sub)stellar members of NGC 2244 spectra (Almendros-Abad+, 2023)
Spectroscopic substellar initial mass function of NGC 2244.
Almendros-Abad V., Muzic K., Bouy H., Bayo A., Scholz A., Pena Ramirez K.,
Moitinho A., Kubiak K., Schoedel R., Barac R., Brcic P., Ascenso J.,
Jayawardhana R.
<Astron. Astrophys. 677, A26 (2023)>
=2023A&A...677A..26A 2023A&A...677A..26A (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Stars, pre-main sequence ; Spectra, infrared
Keywords: stars: pre-main sequence - brown dwarfs - stars: luminosity function -
mass function - open clusters and associations: individual: NGC 2244
Abstract:
The dominant formation channel of brown dwarfs (BDs) is not well
constrained yet and a promising way to discriminate between scenarios
consists of testing environment-dependent efficiency in forming BDs.
So far, the outcome of star formation, studied through the initial
mass function, has been found to be very similar in all clusters that
have been studied.
We aim to characterize the low-mass (sub)stellar population of the
central portion (2.4pc2) of the ∼2Myr old cluster NGC 2244
using near-infrared spectroscopy. By studying this cluster,
characterized by a low stellar density and numerous OB stars, we aim
to explore the effect that OB stars may have on the production of BDs.
We obtained near-infrared HK spectroscopy of 85 faint candidate
members of NGC 2244. We derived the spectral type and extinction by
comparison with spectral templates. We evaluated cluster membership
using three gravity-sensitive spectral indices based on the shape of
the H-band. Furthermore, we evaluated the infrared excess from Spitzer
of all the candidate members of the cluster. Finally, we estimated the
mass of all the candidate members of the cluster and derived the
initial mass function, star-to-BD number ratio and disk fraction.
The initial mass function is well represented by a power law (dN/dM
∝ M-alpha) below 0.4M☉, with a slope alpha=0.7-1.1
depending on the fitted mass range. We calculated a star-to-BD number
ratio of 2.2-2.8. We find the low-mass population of NGC 2244 to be
consistent with nearby star- forming regions, although it is at the
high end of BD production. We find BDs in NGC 2244 to be, on average,
closer to OB stars than to low-mass stars, which could potentially be
the first piece evidence that OB stars affect the formation of BDs. We
find a disk fraction of all the members with a spectral type later
than K0 of 39±9% which is lower than typical values found in
nearby star-forming regions of similar ages.
Description:
KMOS/VLT spectra and parameters of 34 candidate members of NGC 2244.
The data provided are the reduced, wavelength-calibrated, telluric
corrected HK bands 1-d spectra. The spectra are given in fits format
and are not corrected for extinction. We also provide the full list of
candidate members used in this work.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 69 42 Properties of the observed KMOS objects with
late SpType spectroscopic shape
tabled1.dat 63 137 Membership analysis of all the members
and candidate members
list.dat 53 34 List of KMOS fits spectra
fits/* . 34 Individual fits spectra
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See also:
J/ApJ/836/34 : 24um excesses in clusters + membership of NGC2244 (Meng+, 2017)
J/ApJ/881/79 : Flamingos-2 near-infrared photometry in NGC2244 (Muzic+, 2019)
J/A+A/668/A19 : Stellar population of Rosette Nebula and NGC2244 (Muzic+, 2022)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- ID Source ID ([MSP2019] NGC2244 NNN
in Simbad for members in M22)
5- 12 F8.5 deg RAdeg Right ascension (J2000)
14- 20 F7.5 deg DEdeg Declination (J2000)
22- 25 A4 --- SpType Spectral type
27- 30 F4.1 mag AV Visual extinction
32- 35 A4 --- SpTind Derived spectral type
37- 40 I4 K Teff Effective temperature
42- 46 F5.3 Msun Mass ?=- Mass
48- 52 F5.3 Msun E_Mass ? Mass error (lower value)
54- 58 F5.3 Msun e_Mass ? Mass error (upper value)
60 A1 --- Low-g [YN?] Low surface gravity ?
62- 64 A3 --- n_Low-g Note on Low-g (1)
67 A1 --- Excess [Y-N] Infrared excess ?
69 A1 --- Member [YN?] Member ?
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Note (1): Notes as follows:
a = Low surface gravity key defined in Sect. 3.1.4 based on three
gravity-sensitive spectral indices
b = Spectra where a low S/N does not allow a confident derivation of
gravity-sensitive spectral indices, they are classified as
possible members
c = Classified as member in Muzic et al.
(2022A&A...668A..19M 2022A&A...668A..19M, Cat. J/A+A/668/A19)
d = Classified as member in Meng et al.
(2017ApJ...836...34M 2017ApJ...836...34M, Cat. J/ApJ/836/34)
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Byte-by-byte Description of file: tabled1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- ID Source ID ([MSP2019] NGC2244 NNN
in Simbad for members in M22)
5- 6 I2 h RAh Right ascension (J2000)
8- 9 I2 min RAm Right ascension (J2000)
11- 16 F6.3 s RAs Right ascension (J2000)
18 A1 --- DE- Declination sign (J2000)
19- 20 I2 deg DEd Declination (J2000)
22- 23 I2 arcmin DEm Declination (J2000)
25- 30 F6.3 arcsec DEs Declination (J2000)
32- 36 A5 --- SpType Spectral type, templates
38- 42 F5.2 mag Av Visual extinction, templates
44- 47 I4 K Teff ?=- Effective temperature
49 A1 --- KMOS [YN-] Observed with KMOS
51 A1 --- KMOS-grav [YN-?] KMOS gravity-sensitive
spectral indices key
53 A1 --- VIMOS [YN-] Observed with VIMOS
55 A1 --- VIMOS-Ha [YN-] VIMOS Hα emission consistent
with accretion
57 A1 --- M17 [YN-] Membership in Meng et al.
(2017ApJ...836...34M 2017ApJ...836...34M, Cat. J/ApJ/836/34)
59 A1 --- M22 [YN-] Membership in Muzic et al.
(2022A&A...668A..19M 2022A&A...668A..19M, Cat. J/A+A/668/A19)
61 A1 --- Excess [YN-] Infrared excess
63 A1 --- Member [YN-?] Membership to NGC 2244
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Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- ID Source ID
5- 6 I2 h RAh Right ascension (J2000)
8- 9 I2 min RAm Right ascension (J2000)
11- 16 F6.3 s RAs Right ascension (J2000)
18 A1 --- DE- Declinatino sign (J2000
19- 20 I2 deg DEd Declination (J2000)
22- 23 I2 arcmin DEm Declination (J2000)
25- 30 F6.3 arcsec DEs Declination (J2000)
32- 35 A4 --- SpType Spectral type, templates
37- 39 F3.1 mag Av Visual extinction, templates
41 A1 --- Member Membership to NGC 2244
43- 53 A11 --- FileName Name of the spectrum fits file
in subdirectory fits
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Acknowledgements:
Victor Almendros-Abad, valmendros(at)sim.ul.pt
History:
29-Aug-2023: on-line version
02-Nov-2023: table2 added from electronic version
(End) Patricia Vannier [CDS] 12-Jun-2023