J/MNRAS/516/4164 +150 OB stars in Sextans A (Lorenzo+, 2022)
A new reference catalogue for the very metal-poor Universe:
+150 OB stars in Sextans A.
Lorenzo M., Garcia M., Najarro F., Herrero A., Cervino M., Castro N.
<Mon. Not. R. Astron. Soc., 516, 4164-4179 (2022)>
=2022MNRAS.516.4164L 2022MNRAS.516.4164L (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Stars, OB ; Spectral types ;
Photometry ; Optical ; Ultraviolet
Keywords: stars: early-type - stars: massive - stars: Population III -
galaxies: individual: Sextans A - galaxies: stellar content
Abstract:
Local Group (LG) very metal-poor massive stars are the best proxy for
the First Stars of the Universe and fundamental to modelling the
evolution of early galaxies. These stars may follow new evolutionary
pathways restricted to very low metallicities, such as chemically
homogeneous evolution (CHE). However, given the great distance leap
needed to reach very metal-poor galaxies of the LG and vicinity, no
comprehensive spectroscopic studies have been carried out at
metallicities lower than the Small Magellanic Cloud (SMC;
Z=1/5Z☉) until now. After five observing campaigns at the 10.4-m
Gran Telescopio Canarias, we have assembled a low-resolution (R∼1000)
spectroscopic collection of more than 150 OB stars in the 1/10Z☉
galaxy Sextans A, increasing by an order of magnitude the number of
massive stars known in this galaxy. The catalogue includes 38 BA-type
supergiants, four red supergiants, and the first candidate
1/10Z☉ binary systems, CHE sources and systems hosting stripped
stars. The sample massive stars mainly overlap the higher
concentrations of neutral gas of Sextans A. However, we find some
sources in low HI column-density regions. The colour-magnitude diagram
of the galaxy presents large dispersion, which suggests uneven,
internal extinction in Sextans A. This is the largest catalogue of
OB-type stars ever produced at sub-SMC metallicities. This sample
constitutes a fundamental first step to unveiling the evolutionary
pathways and fates of very metal-poor massive stars, analyzing the
dependence of radiation-driven winds with metallicity, and studying
binary systems in an environment analogue to the early Universe.
Description:
Identification numbers, coordinates and photometry of the stars
observed in this work. We also include the derived spectral
classification, radial velocities, signal-to-noise ratio of the final
spectrum and additional information in the column Notes.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 144 125 Blue type stars (from O to F types) confirmed by
spectroscopy in this work
(s001 to s125)
table2.dat 118 41 Blue type stars for which a spectral subtype
could not be assigned (s126 to s166)
table3.dat 130 8 Late type stars observed in this work
(s167 to s174)
table4.dat 98 18 List of blue outliers in the CMD of Sextans A
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See also:
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
J/AJ/133/2393 : UBVRI phot. in seven Local Group dwarfs galaxies (Massey+ 2007)
J/AJ/143/74 : HST photometry in 6 dwarf galaxies (Bianchi+, 2012)
Byte-by-byte Description of file: table1.dat table2.dat table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- ID Identification code in this work (sNNN)
6- 24 A19 --- OName Identification code in alternative
photometric catalogues
26 A1 --- n_OName [MBSH] Note on OName (1)
28- 29 I2 h RAh Right ascension (J2000.0)
31- 32 I2 min RAm Right ascension (J2000.0)
34- 38 F5.2 s RAs Right ascension (J2000.0)
40 A1 --- DE- Declination sign (J2000.0)
41- 42 I2 deg DEd Declination (J2000.0)
44- 45 I2 arcmin DEm Declination (J2000.0)
47- 51 F5.2 arcsec DEs Declination (J2000.0)
53- 67 A15 --- SpType Spectral type
69- 74 F6.3 mag Vmag ?=- Visual magnitude
76- 81 F6.3 mag B-V ?=- Colour B-V
83- 88 F6.3 mag Q ?=- Free reddening pseudo-colour Q
(Q = (U-B)-0.72*(B-V)) (not in table3.dat)
90- 92 I3 km/s RV Radial velocity derived in this work
94- 96 I3 km/s e_RV Uncertainty in the derived radial velocity
98 A1 --- n_RV [*] Note on RV (2)
100-102 I3 --- SNR ? Signal-to-noise ratio per element of
resolution calculated in a region free of
spectral lines around 4800Å
(not in table3.dat)
104-144 A41 --- Notes Additional information (3)
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Note (1): In this column we indicate which photometric catalogue was used for
the identification numbers (OName), coordinates (RA*, DE*) and photometry
(Vmag, B-V, Q) as follows:
M = Massey et al. (2007AJ....133.2393M 2007AJ....133.2393M, Cat. J/AJ/133/2393)
B = Bianchi et al. (2012AJ....143...74B 2012AJ....143...74B, Cat. J/AJ/143/74)
S = 2MASS catalogue (Skrutskie et al., 2006AJ....131.1163S 2006AJ....131.1163S, Cat. VII/233
H = Holtzman, Afonso & Dolphin (2006ApJS..166..534H 2006ApJS..166..534H)
Note (2): * indicates when RV was determined manually.
Note (3): References are:
Garcia2019 = Garcia et al. (2019MNRAS.484..422G 2019MNRAS.484..422G)
Camacho2016 = Camacho et al. (2016A&A...585A..82C 2016A&A...585A..82C)
Britavskiy2019 = Britavskiy et al. (2019A&A...631A..95B 2019A&A...631A..95B)
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- ID Identification code in this work (sNNN)
6- 18 A13 --- SpType Spectra type
20- 25 F6.3 mag Vmag V magnitude from Massey et al.
(2007AJ....133.2393M 2007AJ....133.2393M, Cat. J/AJ/133/2393)
27- 32 F6.3 mag B-V B-V colour from Massey et al.
(2007AJ....133.2393M 2007AJ....133.2393M, Cat. J/AJ/133/2393)
34- 40 A7 --- UVdet [Yes No info] UV detection flag
42- 46 F5.2 mag F170W ?=- F170W magnitude from Bianchi et al.
(2012AJ....143...74B 2012AJ....143...74B, Cat. J/AJ/143/74)
48- 52 F5.2 mag F170W-F225W ?=- F170W-F225W colour frm Bianchi et al.
(2012AJ....143...74B 2012AJ....143...74B, Cat. J/AJ/143/74)
54- 56 A3 --- UVout [Yes No -] flag the objects that are
outliers in the UV CMD
58- 61 F4.2 [Lsun] logL Derived luminosity (this work)
63- 66 F4.2 [Lsun] logLC ?=- Calibrated luminosity for the
corresponding spectral type
68- 70 A3 --- Binary [Yes No] Whether or not the source presents
signatures of multiplicity in its spectra
72- 74 A3 --- Broad [Yes No ?] Whether or not the source line
profiles are broader than models with
vsini>300km/s
76- 98 A23 --- Type Suggested type
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Acknowledgements:
Marta Lorenzo, mlorenzo(at)cab.inta-csic.es
(End) Patricia Vannier [CDS] 28-Jul-2023