J/MNRAS/481/3902 New Galactic clusters in the VVVX disc area (Borissova+, 2018)
New Galactic star clusters discovered in the disc area of the VVVX survey.
Borissova J., Ivanov V.D., Lucas P.W., Kurtev R., Alonso-Garcia J.,
Ramirez Alegria S., Minniti D., Froebrich D., Hempel M., Medina N.,
Chene A.-N., Kuhn M.A.
<Mon. Not. R. Astron. Soc., 481, 3902-3920 (2018)>
=2018MNRAS.481.3902B 2018MNRAS.481.3902B (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Infrared ; Photometry ; Positional data
Keywords: Galaxy: open clusters and associations: general - Galaxy: disk -
Infrared: stars
Abstract:
The 'VISTA Variables in the Via Lactea eXtended (VVVX)' ESO Public
Survey is a near-infrared photometric sky survey that covers nearly
1700deg2 towards the Galactic disc and bulge. It is well-suited to
search for new open clusters, hidden behind dust and gas. The pipeline
processed and calibrated KS-band tile images of 40 per cent of the
disc area covered by VVVX was visually inspected for stellar
overdensities. Then, we identified cluster candidates by examination
of the composite JHKS colour images. The colour-magnitude diagrams of
the cluster candidates are constructed. Whenever possible the Gaia DR2
parameters are used to calculate the mean proper motions, radial
velocities, reddening and distances. We report the discovery of 120
new infrared clusters and stellar groups. Approximately half of them
(47 per cent) are faint, compact, highly reddened, and they seem to be
associated with other indicators of recent star formation, such as
nearby Young Stellar Objects, Masers, HII regions or bubbles. The
preliminary distance determinations allow us to trace the clusters up
to 4.5kpc, but most of the cluster candidates are centred at 2.2kpc.
The mean proper motions of the clusters show that in general they
follow the disc motion of the Galaxy.
Description:
The VVV and VVVX data were obtained with the 4.1-m ESO VISTA telescope
(Visual and Infrared Survey Telescope for Astronomy; Emerson,
McPherson & Sutherland 2006Msngr.126...41E 2006Msngr.126...41E) located at Cerro Paranal,
Chile, with the 16-detector VIRCAM (VISTA Infrared CAMera; Dalton et
al. 2006SPIE.6269E..0XD). It has an ∼1x1.5deg2 field of view and
works in the 0.9-2.5µm wavelength range and a pixel scale of
0.34arcsec/pixel. The data are reduced with the VISTA Data Flow System
(VDFS; Emerson et al. 2004SPIE.5493..401E 2004SPIE.5493..401E; Irwin et al.
2004SPIE.5493..411I 2004SPIE.5493..411I) at the Cambridge Astronomical Survey Unit (CASU).
Processed images and photometric catalogues are available from the ESO
Science Archive3 and from the VISTA Science Archive4 (VSA; Cross et
al. 2012A&A...548A.119C 2012A&A...548A.119C). A single VIRCAM image, called paw, contains
large gaps; six paws taken in a spatial offset pattern must be
combined to fill them in, obtaining a contiguous image, called tile.
The VVVX paws and tiles are aligned along l and b. The total exposure
time of the tiles are: 8s in KS (for a single epoch), 24s in H and
60 in J band. The tiles overlap by a few arcmin in Galactic latitude
and longitude - just like with the VVV - to ensure homogeneous
coverage, spatial continuity and overall photometric and astrometric
consistency.
We have also collected K-band spectra of 3 and 2 stars for VVVX CL010
and CL011, respectively, using the IR spectrograph and imaging camera
SofI in long-slit mode, mounted on the ESO New Technology Telescope
(NTT). Some parameters of these stars are measured in the Gaia DR2
catalogue and are tabulated in Table 1.
We identified 120 new candidate star clusters or stellar groups,
listed in Table A1. In Table B1 are tabulated the candidate star
clusters with reliable Gaia DR2 parameters.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 144 5 Parameters of stars with spectra
tablea1.dat 121 120 VVVX cluster candidates: catalogue
tableb1.dat 115 61 VVVX cluster candidates: parameters
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 20 A20 --- Name Star name ([BIL2018] CLNNN ObjN)
22- 30 F9.5 deg RAdeg Right ascension (J2000)
32- 40 F9.5 deg DEdeg Declination (J2000)
42- 47 F6.4 mas plx Parallax
49- 53 F5.3 mas e_plx Error on plx
55- 61 F7.3 mas/yr pmRA Proper motion in right ascension
63- 67 F5.3 mas/yr e_pmRA Error on pmRA
69- 74 F6.3 mas/yr pmDE Proper motion in declination
76- 80 F5.3 mas/yr e_pmDE Error on pmDE
82- 86 F5.2 mag Gmag Gaia DR2 G-band magnitude
88- 92 F5.3 mag e_Gmag Error on Gmag
94-100 F7.2 K Teff Effective temperature
102-103 A2 --- SpType Spectral type
105-109 F5.2 mag Jmag Magnitude on the J-band
111-114 F4.2 mag e_Jmag Error on Jmag
116-119 F4.2 mag Hmag Magnitude on the H-band
121-124 F4.2 mag e_Hmag Error on Hmag
126-129 F4.2 mag Ksmag Magnitude on the Ks-band
131-134 F4.2 mag e_Ksmag Error on Ksmag
136-139 F4.2 mag E(J-K) Mean reddening
141-144 F4.2 kpc Dist Distance
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Name of the VVVX cluster candidate
(VVVX CLNNN)
12- 21 F10.6 deg RAdeg Right ascension (J2000) (1)
23- 32 F10.6 deg DEdeg Declination (J2000) (1)
34- 36 I3 arcsec Rad Eye-ball measured apparent cluster radius
38- 42 A5 --- VVVXtile Name of the corresponding VVVX tile
44-121 A78 --- Comments Comments about the nature of the object
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Note (1): Equatorial coordinates of the centre determined by eye
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Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Name of the VVVX cluster candidate
(VVVX CLNNN)
12- 21 F10.6 deg RAdeg Right ascension (J2000)
23- 32 F10.6 deg DEdeg Declination (J2000)
34- 40 F7.4 mas/yr pmRA ? Proper motion in right ascension
µ_α*cosδ
42- 47 F6.4 mas/yr e_pmRA ? Error on pmRA
49- 55 F7.4 mas/yr pmDE ? Proper motion in declination
57- 62 F6.4 mas/yr e_pmDE ? Error on pmDE
64- 69 F6.4 mas plx ? Parallax
71- 76 F6.4 mas e_plx ? Error on parallax
78- 81 I4 kpc Dist ? Distance
83- 86 I4 kpc Distp5 ? 5th percentile of Dist
88- 91 I4 kpc Distp95 ? 95th percentile of Dist
93- 99 F7.2 km/s RV ? Radial velocity
101-105 F5.2 km/s e_RV ? Error on RV
107-110 F4.2 mag BP-RP ? Gaia DR2 BP-RP color
112-115 F4.2 mag e_BP-RP ? Error on BP-RP
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 13-Jun-2022