J/MNRAS/507/5106 NGC 6822 massive young stellar objects (Kinson+, 2021)
Massive young stellar objects in the Local Group irregular galaxy NGC 6822
identified using machine learning.
Kinson D.A., Oliveira J.M., Van Loon J.T.
<Mon. Not. R. Astron. Soc., 507, 5106-5131 (2021)>
=2021MNRAS.507.5106K 2021MNRAS.507.5106K (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; YSOs ; Photometry, millimetric/submm ;
Photometry, infrared
Keywords: methods: statistical - stars: formation - stars: protostars -
galaxies: individual (NGC 6822) - Local Group -
galaxies: stellar content
Abstract:
We present a supervised machine learning methodology to classify
stellar populations in the Local Group dwarf-irregular galaxy
NGC 6822. Near-IR colours (J-H, H-K, and J-K), K-band magnitudes and
far-IR surface brightness (at 70 and 160um) measured from Spitzer
and Herschel images are the features used to train a Probabilistic
Random Forest (PRF) classifier. Point-sources are classified into
eight target classes: young stellar objects (YSOs), oxygen- and
carbon-rich asymptotic giant branch stars, red giant branch and red
supergiant stars, active galactic nuclei, massive main-sequence stars,
and Galactic foreground stars. The PRF identifies sources with an
accuracy of ∼90 per cent across all target classes rising to ∼96 per
cent for YSOs. We confirm the nature of 125 out of 277 literature YSO
candidates with sufficient feature information, and identify 199 new
YSOs and candidates. Whilst these are mostly located in known
star-forming regions, we have also identified new star formation
sites. These YSOs have mass estimates between ∼15 and 50M☉,
representing the most massive YSO population in NGC 6822. Another 82
out of 277 literature candidates are definitively classified as
non-YSOs by the PRF analysis. We characterize the star formation
environment by comparing the spatial distribution of YSOs to those of
gas and dust using archival images. We also explore the potential of
using (unsupervised) t-distributed stochastic neighbour embedding maps
for the identification of the same stellar population classified by
the PRF.
Description:
Near infrared properties, confidence level and previous identifications
of YSOs identified in the galaxy NGC6822.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 184 1578 Positions, measurements, and their uncertainties
(where available) as well as source
classification from the training set
table3.dat 111 324 Catalogue of YSOs and YSO candidates in NGC 6822
classified using the PRF analysis
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See also:
J/ApJ/892/91 : UKIRT NIR and Spitzer MIR phot. in NGC 6822 (Hirschauer+, 2020)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- LARID Identification number
7- 18 F12.8 deg RAdeg Right ascension (J2000)
20- 31 F12.8 deg DEdeg Declination (J2000)
33- 43 F11.8 mag Kmag ? K magnitude
45- 54 F10.8 mag e_Kmag ? rms uncertainty on Kmag
56- 79 F24.16 MJy/sr mu70um ?=0 Surface brightness at 70um
81-104 F24.16 MJy/sr mu160um ?=0 Surface brightness at 160um
106-118 F13.9 mag J-H ? J-H colour index
120-130 F11.9 mag e_J-H ? rms uncertainty on J-H
132-143 F12.8 mag H-K ? H-K colour index
145-155 F11.9 mag e_H-K ? rms uncertainty on H-K
157-168 F12.8 mag J-K ? J-K colour index
170-180 F11.9 mag e_J-K ? rms uncertainty on J-K
182 I1 --- Type [0/8] Type (1)
184 A1 --- TSExt [*] * for TS Extention
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Note (1): Type as follows:
0 = YSO, from Spitzer-IRS spectra method
1 = OAGB, from VIS/NIR spectra, narrowband indices method
2 = CAGB, from VIS/NIR spectra, narrowband indices method
3 = AGN, from various methods
4 = FG, from Gaia proper motions method
5 = RGB, from Spitzer-IRS spectra method
6 = RSG, from Optical and Spitzer-IRS spectra method
8 = MMS, from Gaia proper motions method
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 10 F10.6 deg RAdeg Right Ascension (J2000)
12- 21 F10.6 deg DEdeg Declination (J2000)
23- 31 F9.6 mag Jmag ? J magnitude
33- 43 F11.9 mag e_Jmag ? J magnitude error
45- 53 F9.6 mag Hmag ? H magnitude
55- 65 F11.9 mag e_Hmag ? H magnitude error
67- 75 F9.6 mag Kmag ? K magnitude
77- 87 F11.9 mag e_Kmag ? K magnitude error
89-103 A15 --- YSO? YSO, YSO Candidate or TS Extention
105-111 A7 --- PrevID [J19/H20 ] Previous name J19/H20 (1)
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Note (1): YSO previously identified in Jones et al. (2019MNRAS.490..832J 2019MNRAS.490..832J, J19)
or Hirschauer et al. (2020ApJ...892...91H 2020ApJ...892...91H, Cat. J/ApJ/892/91, H20).
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Acknowledgements:
David Kinson, d.a.kinson(at)keele.ac.uk
(End) Patricia Vannier [CDS] 12-Nov-2022