J/A+A/657/A129 13 young brown dwarfs SINFONI spectra (Almendros-Abad+, 2022)
Youth analysis of near infrared spectra of young low-mass stars and
brown dwarfs.
Almendros-Abad V., Muzic K., Moitinho A., Krone-Martins A., Kubiak K.
<Astron. Astrophys. 657, A129 (2022)>
=2022A&A...657A.129A 2022A&A...657A.129A (SIMBAD/NED BibCode)
ADC_Keywords: Stars, pre-main sequence ; Stars, late-type ; Spectra, infrared ;
Spectroscopy
Keywords: stars: pre-main sequence - stars: formation -
techniques: spectroscopic - stars: low-mass
Abstract:
Studies of the low-mass population statistics in young clusters are
the foundation for our understanding of the formation of low-mass
stars and brown dwarfs. Robust low-mass populations can be obtained
through near-infrared spectroscopy, which provides confirmation of the
cool and young nature of member candidates. However, the spectroscopic
analysis of these objects is often not performed in a uniform manner,
and the assessment of youth generally relies on the visual inspection
of youth features whose behavior is not well understood.
We aim at building a method that efficiently identifies young low-mass
stars and brown dwarfs from low-resolution near-infrared spectra, by
studying gravity-sensitive features and their evolution with age.
We built a dataset composed of all publicly available (∼2800)
near-infrared spectra of dwarfs with spectral types between M0 and L3.
First, we investigate methods for the derivation of the spectral type
and extinction using comparison to spectral templates, and various
spectral indices. Then, we examine gravity-sensitive spectral indices
and apply machine learning methods, in order to efficiently separate
young (≲10Myr) objects from the field.
Using a set of six spectral indices for spectral typing, including two
newly defined ones (TLI-J and TLI-K), we are able to achieve a
precision below 1 spectral subtype across the entire spectral type
range. We define a new gravity-sensitive spectral index (TLI-g) that
consistently separates young from field objects, showing a performance
superior to other indices from the literature. Even better separation
between the two classes can be achieved through machine learning
methods which use the entire NIR spectra as an input. Moreover, we
show that the H- and K-bands alone are enough for this purpose.
Finally, we evaluate the relative importance of different spectral
regions for gravity classification as returned by the machine learning
models. We find that the H-band broad-band shape is the most relevant
feature, followed by the FeH absorption bands at 1.2um and 1.24um and
the KI doublet at 1.24.
Description:
The data provided are the reduced, flux- and wavelength-calibrated,
telluric corrected JHK bands 1-d spectra of 13 young objects presented
in this work. The spectra were observed with SINFONI/VLT and contain
JHK bands. The spectra are given in fits format and are not corrected
for extinction.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
list.dat 118 13 List of SINFONI spectra
fits/* . 13 Individual fits spectra
--------------------------------------------------------------------------------
Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 22 A22 --- Name Source name
24- 25 I2 h RAh Right ascension (J2000)
27- 28 I2 min RAm Right ascension (J2000)
30- 31 I2 s RAs Right ascension (J2000)
33 A1 --- DE- Declination sign (J2000)
34- 35 I2 deg DEd Declination (J2000)
37- 38 I2 arcmin DEm Declination (J2000)
40- 41 I2 arcsec DEs Declination (J2000)
43- 48 F6.3 mag Jmag J magnitude
50- 55 F6.3 mag Hmag H magnitude
57- 62 F6.3 mag Kmag K magnitude
64- 70 A7 --- Region Region: Taurus, Rho oph, Cha-I, UpSco, Field
72- 74 A3 --- SpT-lit Spectral type, literature (1)
76- 79 A4 --- SpT-ind Spectral type, indices (2)
81- 84 A4 --- SpT-temp Spectral type, templates (3)
86- 89 A4 --- Av-temp Extinction, templates (3)
91- 94 I4 Kibyte size Size of FITS file
96-118 A23 --- FileName Name of JHK spectrum in subdirectory fits
--------------------------------------------------------------------------------
Note (1): Spectral type of the sources from Luhman et al. (2009ApJ...703..399L 2009ApJ...703..399L),
Luhman et al. (2003ApJ...590..348L 2003ApJ...590..348L),
Alves de Oliveira et al. (2012A&A...539A.151A 2012A&A...539A.151A),
Luhman et al. (2008ApJ...684..654L 2008ApJ...684..654L, Cat. J/ApJ/684/654),
Luhman (2007ApJS..173..104L 2007ApJS..173..104L, cat. J/ApJS/173/104),
Muzic et al. (2015ApJ...810..159M 2015ApJ...810..159M),
Pena-Ramirez et al. (2016A&A...586A.157P 2016A&A...586A.157P),
Allers et al. (2013ApJ...772...79A 2013ApJ...772...79A).
Note (2): The column refer to the results obtained using spectral indices, as
explained in Section 3.2.
Note (3): The columns refer to the results obtained by comparison with spectral
templates, as explained in Section 3.1.
--------------------------------------------------------------------------------
Acknowledgements:
Victor Almendros-Abad, valmendros(at)sim.ul.pt
(End) Victor Almendros-Abad [CENTRA], Patricia Vannier [CDS] 22-Oct-2021