J/A+A/615/A148 Pre-main sequence stars in Scorpius OB1 (Damiani, 2018)
The low-mass pre-main sequence population of Scorpius OB1.
Damiani F.
<Astron. Astrophys. 615, A148 (2018)>
=2018A&A...615A.148D 2018A&A...615A.148D (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Stars, pre-main sequence ; X-ray sources
Keywords: open clusters and associations: individual: Sco OB1 -
open clusters and associations: individual: NGC6231 -
open clusters and associations: individual: Trumpler 24 -
stars: pre-main sequence - X-rays: stars
Abstract:
The low-mass members of OB associations, expected to be a major
component of their total population, are in most cases poorly studied
because of the difficulty of selecting these faint stars in crowded
sky regions. Our knowledge of many OB associations relies on only a
relatively small number of massive members.
We study here the Sco OB1 association, with the aim of a better
characterization of its properties, such as global size and shape,
member clusters and their morphology, age and formation history, and
total mass.
We use deep optical and near-infrared (NIR) photometry from the VPHAS+
and VVV surveys, over a wide area (2.6°x2.6°), complemented by
Spitzer infrared (IR) data, and Chandra and XMM-Newton X-ray data. A
new technique is developed to find clusters of pre-main sequence
M-type stars using suitable color-color diagrams, complementing
existing selection techniques using narrow-band Hα photometry or
NIR and ultraviolet (UV) excesses, and X-ray data.
We find a large population of approximately 4000 candidate low-mass
Sco OB1 members whose spatial properties correlate well with those of
Hα-emission, NIR-excess, UV-excess, and X-ray detected members,
and unresolved X-ray emission. The low-mass population is spread among
several interconnected subgroups: they coincide with the HII regions
G345.45+1.50 and IC4628, and the rich clusters NGC 6231 and
Trumpler 24, with an additional subcluster intermediate between these
two. The total mass of Sco OB1 is estimated to be ∼8500M☉.
Indication of a sequence of star-formation events is found, from South
(NGC 6231) to North (G345.45+1.50). We suggest that the diluted
appearance of Trumpler 24 indicates that the cluster is now dissolving
into the field, and that tidal stripping by NGC 6231 nearby
contributes to the process.
Description:
New candidate members of Sco OB1, including normal M-type stars, NIR-
and uv-excess stars, and H-alpha emission stars. Also tabulated are
previously unpublished lists of X-ray sources from Chandra/ACIS-I and
XMM-Newton/EPIC observations covering a small fraction of the entire
Sco OB1 association.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb1.dat 108 384 Chandra ACIS-I X-ray sources in G345.45+1.50
tableb2.dat 110 195 XMM-Newton EPIC X-ray sources in Trumpler 24
tableb3.dat 94 12041 Optical/NIR photometry for M stars and stars
with UV/IR/Hα excess
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See also:
II/341 : VPHAS+ DR2 survey (Drew+, 2016)
Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Xray [1/384] X-ray source number
5- 20 A16 --- CXOU Chandra source standard Identifier
(JHHMMSS.s+DDMMSS)
22- 30 F9.5 deg RAdeg Right ascension (J2000.0)
32- 40 F9.5 deg DEdeg Declination (J2000.0)
42- 45 F4.2 arcsec PosErr Position error
47- 51 F5.3 ct/ks CRate X-ray count rate
53- 57 F5.3 ct/ks e_CRate Error on X-ray count rate
59- 76 A18 --- VPHAS ? VPHAS+ (Cat. II/341) identifier
(JHHMMSS.s+DDMMSS.s)
78- 82 F5.2 mag rmag ? VPHAS+ r magnitude
84- 87 F4.2 mag g-r ? VPHAS+ g-r color
89- 92 F4.2 mag r-i ? VPHAS+ r-i color
94- 98 F5.2 mag Jmag ? NIR J magnitude
100-103 F4.2 mag J-H ? NIR J-H color
105-108 F4.2 mag H-K ? NIR H-K color
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Byte-by-byte Description of file: tableb2.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Xray [385/579] X-ray source number
5- 20 A16 --- XMMU XMM source standard Identifier
(JHHMMSS.s+DDMMSS)
22- 30 F9.5 deg RAdeg Right ascension (J2000.0)
32- 40 F9.5 deg DEdeg Declination (J2000.0)
42- 45 F4.2 arcsec PosErr Position error
47- 52 F6.3 ct/ks CRate X-ray count rate
54- 58 F5.3 ct/ks e_CRate Error on X-ray count rate
60- 77 A18 --- VPHAS ? VPHAS+ (Cat. II/341) identifier
(JHHMMSS.s+DDMMSS.s)
79- 83 F5.2 mag rmag ? VPHAS+ r magnitude
85- 88 F4.2 mag g-r ? VPHAS+ g-r color index
90- 93 F4.2 mag r-i ? VPHAS+ r-i color index
95- 99 F5.2 mag Jmag ? NIR J magnitude
101-105 F5.2 mag J-H ? NIR J-H color index
107-110 F4.2 mag H-K ? NIR H-K color index
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Byte-by-byte Description of file: tableb3.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- Seq [1/12041] Sequential star number
7- 15 F9.5 deg RAdeg Right ascension (J2000.0)
17- 25 F9.5 deg DEdeg Declination (J2000.0)
27- 44 A18 --- VPHAS VPHAS+ identifier (JHHMMSS.s+DDMMSS.s)
46- 50 F5.2 mag rmag ? VPHAS+ r magnitude
52- 55 F4.2 mag r-i ? VPHAS+ r-i color
57- 60 F4.2 mag r-Ha ? VPHAS+ r-Halpha color
62- 65 F4.2 mag g-r ? VPHAS+ g-r color index
67- 71 F5.2 mag u-g ? VPHAS+ u-g color index
73- 77 F5.2 mag Jmag ? NIR J magnitude
79- 82 F4.2 mag J-H ? NIR J-H color index
84- 88 F5.2 mag H-K ? NIR H-K color index
90 A1 --- IRexc [Y] IR-excess flag
92 A1 --- Haem [Y] H-alpha-emission flag
94 A1 --- UVexc [Y] UV-excess flag
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Acknowledgements:
Francesco Damiani, damiani(at)astropa.inaf.it
(End) Francesco Damiani [INAF-OAPA], Patricia Vannier [CDS] 22-Aug-2018