J/A+A/623/A25 Photometric and astrometric study of NGC 6530 (Damiani+, 2019)
Wide-area photometric and astrometric (Gaia DR2) study of the young cluster
NGC 6530.
Damiani F., Prisinzano L., Micela G., Sciortino S.
<Astron. Astrophys. 623, A25 (2019)>
=2019A&A...623A..25D 2019A&A...623A..25D (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Stars, pre-main sequence ; X-ray sources ;
Parallaxes, trigonometric ; Proper motions
Keywords: open clusters and associations: individual: NGC 6530 -
stars: pre-main sequence - parallaxes - proper motions - X-rays: stars
Abstract:
NGC 6530 is a young cluster, with a complex morphology and
star-formation history. We present a statistical study of its global
properties, using a new, large list of candidate members down to
masses of 0.2-0.4M☉ and Gaia DR2 astrometry.
We consider a larger sky region compared to previous studies, to
investigate the entire cluster until its periphery, including any
diffuse population all around the main cluster. We study the
distribution of extinction and age across the different regions, and
obtain constraints on the star-formation history. We also study the
dynamics of cluster members.
Cluster membership was determined on the basis of literature X-ray
data, Hα emission, near-IR and UV excesses from the VPHAS+ and
UKIDSS photometric surveys and published near-IR catalogs, and Gaia
DR2 astrometry; moreover, we used a method for photometric selection
of M-type pre-main-sequence cluster members, which we recently
developed and used for other star-formation regions. The list of
candidates includes nearly 3700 stars, of which we estimate
approximately 2700 to be genuine NGC 6530 members.
Using Gaia parallaxes, the cluster distance is found to be 1325pc,
with errors of 0.5% (statistical) and 8.5% (systematic), in agreement
with previous determinations. The cluster morphology and boundaries
are established with great confidence, from the agreement between the
subsamples of members selected using different criteria. There is no
diffuse population of members around the cluster, but there are minor
condensations of true members in addition to the two main groups in
the cluster core and in the Hourglass nebula. Two such subgroups are
spatially associated with the stars 7 Sgr (F2II-III) and HD 164536
(O7.5V). There is a definite pattern of sequential star formation
across the cluster, within an age range from less than 0.5Myr to
∼5Myr. Extinction is spatially non-uniform, with part of the
population still embedded or obscured by thick dust. The precise Gaia
proper motion data indicate that the NGC 6530 parent cloud collided
with the Galactic plane around 4Myr ago, and we suggest that event as
the trigger of the bulk of star formation in NGC 6530. The internal
cluster dynamics is also partially resolved by the Gaia data,
indicating expansion of the main cluster population with respect to
its center.
Description:
New candidate members of NGC 6530, including normal M-type stars, NIR-
and UV-excess stars, H-alpha emission stars, and Gaia-selected
members.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 100 3675 M-type, NIR- and UV-excess, H-alpha-emission
and Gaia candidate members of NGC 6530
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See also:
II/341 : VPHAS+ DR2 survey (Drew+, 2016)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/A+AS/123/63 : NGC 6530 multiwavelength photometry (van den Ancker+ 1997)
J/AJ/120/333 : UBVRI and Hα in NGC 6530 (Sung+, 2000)
J/A+A/395/499 : XMM observations in M8 and NGC6530 (Rauw+, 2002)
J/ApJ/608/781 : NGC 6530 Chandra X-ray catalog (Damiani+, 2004)
J/A+A/430/941 : Star formation region NGC 6530 (Prisinzano+, 2005)
J/A+A/462/123 : VLT/Flames spectroscopic data of NGC 6530 (Prisinzano+, 2007)
J/AJ/134/1368 : Proper motions in NGC 2244 and NGC 6530 (Chen+, 2007)
J/ApJ/747/51 : Lagoon Nebula stars. I. Rotation periods (Henderson+, 2012)
J/A+A/546/A9 : Spectral classification of stars in NGC 6530 (Prisinzano+ 2012)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Seq [1/3675] Sequential star number
6- 14 F9.5 deg RAdeg Right ascension (J2000.0)
16- 24 F9.5 deg DEdeg Declination (J2000.0)
26- 43 A18 --- VPHAS VPHAS+ identifier (JHHMMSS.S+DDMMSS.s)
45- 49 F5.2 mag imag ? VPHAS+ i magnitude
51- 54 F4.2 mag r-i ? VPHAS+ r-i color index
56- 59 F4.2 mag r-Ha ? VPHAS+ r-Halpha color index
61- 64 F4.2 mag g-r ? VPHAS+ g-r color index
66- 70 F5.2 mag u-g ? VPHAS+ u-g color index
72- 76 F5.2 mag Jmag ? NIR J magnitude
78- 82 F5.2 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 --- Halphaem [Y] H-alpha-emission flag
94 A1 --- UVexc [Y] UV-excess flag
96 A1 --- Mstar [Y] M-star flag
98 A1 --- Xdet [Y] X-ray detection flag
100 A1 --- Gaiamemb [Y] Gaia member flag
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Acknowledgements:
Francesco Damiani, francesco.damiani(at)inaf.it
(End) Francesco Damiani [INAF-OAPA], Patricia Vannier [CDS] 03-Jan-2019