J/A+A/545/A54 Danks 1, Danks 2, and RCW 79 variables (Chene+, 2012)
Massive open star clusters using the VVV survey.
I. Presentation of the data and description of the approach.
Chene A.-N., Borissova J., Clarke J.R.A., Bonatto C., Majaess D.J.,
Moni Bidin C., Sale S.E., Mauro F., Kurtev R., Baume G., Feinstein C.,
Ivanov V.D., Geisler D., Catelan M., Minniti D., Lucas P., De Grijs R.,
Kumar M.S.N.
<Astron. Astrophys., 545, A54-54 (2012)>
=2012A&A...545A..54C 2012A&A...545A..54C
ADC_Keywords: Surveys ; Clusters, open ; Photometry, infrared
Keywords: open clusters and associations: general - infrared: stars - surveys
Abstract:
The ESO Public Survey "VISTA Variables in the Via Lactea"' (VVV)
provides deep multi-epoch infrared observations for unprecedented 562
sq. degrees of the Galactic bulge, and adjacent regions of the disk.
The VVV observations will foster the construction of a sample of
Galactic star clusters with reliable and homogeneously derived
physical parameters (e.g., age, distance, and mass, etc.). In this
first paper in a series, the methodology employed to establish cluster
parameters for the envisioned database are elaborated upon by
analysing four known young open clusters: Danks1, Danks2, RCW79, and
DBS132. The analysis offers a first glimpse of the information that
can be gleaned from the VVV observations for clusters in the final
database. Wide-field, deep JHKs VVV observations, combined with new
infrared spectroscopy, are employed to constrain fundamental
parameters for a subset of clusters. Results are inferred from VVV
near-infrared photometry and numerous low resolution spectra
(typically more than 10 per cluster). The high quality of the spectra
and the deep wide-field VVV photometry enables us to precisely and
independently determine the characteristics of the clusters studied,
which we compare to previous determinations. An anomalous reddening
law in the direction of the Danks clusters is found, specifically
E(J-H)/E(H-Ks)=2.20±0.06, which exceeds published values for the
inner Galaxy. The G305 star forming complex, which includes the Danks
clusters, lies beyond the Sagittarius-Carina spiral arm and occupies
the Centaurus arm. Finally, the first deep infrared colour-magnitude
diagram of RCW79 is presented, which reveals a sizeable pre-main
sequence population. A list of candidate variable stars in G305 region
is reported. This study demonstrates the strength of the dataset and
methodology employed, and constitutes the first step of a broader
study which shall include reliable parameters for a sizeable number of
poorly characterised and/or newly discovered clusters.
Description:
We downloaded, from the VISTA Science Archive (VSA) website
(http://horus.roe.ac.uk/vsa/), the stacked images of the individual
2048x2048 pixel exposures containing the three clusters presented in
this paper. Danks 1 and Danks 2 both appear in VVV field d084,
whilst RCW 79 falls in VVV field d086. These fields were observed
twice in the ZYJHKs bands on 7 to 29 March 2010 (d084), and 18 March
to 4 April 2010 (d086), with the VIRCAM camera mounted on the VISTA 4m
telescope at Paranal Observatory .
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
13 12 27 -62 42.1 Danks 1 = Cl Danks 1
13 12 55 -62 40.9 Danks 2 = Cl Danks 2
13 39.9 -61 45 RCW 79 = RCW 79
13 12 18 -62 42.3 [DBS2003] 132 = [DBS2003] 132
----------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 107 53 Position, photometry and spectral parameters
table5.dat 43 89 List of variable candidates in Danks 1 and Danks 2
table6.dat 43 36 List of variable candidates in RCW 79
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See also:
J/MNRAS/398/221 : UBVIJHK photometry towards (l=305,b=0) (Baume+, 2009)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- Field [D1 D2 DBS2003 132] Field designation (1)
13- 14 A2 --- St [FS m] Status: field star (FS) or member (m)
16- 18 A3 --- --- [Obj ]
19- 20 I2 --- Obj ? Object ID number within the field (2)
22- 26 A5 --- D12 Davies et al. (2012MNRAS.419.1871D 2012MNRAS.419.1871D)
designation of the star (3)
28- 29 I2 h RAh Right ascension (J2000)
31- 32 I2 min RAm Right ascension (J2000)
34- 39 F6.3 s RAs Right ascension (J2000)
41 A1 --- DE- Declination sign (J2000)
42- 43 I2 deg DEd Declination (J2000)
45- 46 I2 arcmin DEm Declination (J2000)
48- 52 F5.2 arcsec DEs Declination (J2000)
54- 58 F5.2 mag Vmag ? Johnson V magnitude (from Baume et al.,
2009MNRAS.398..221B 2009MNRAS.398..221B, Cat. J/MNRAS/398/221)
60- 65 F6.3 mag Jmag ? Vista J magnitude
66- 70 F5.2 mag Hmag ? Vista H magnitude
72- 76 F5.2 mag Ksmag ? Vista Ks magnitude
78- 81 I4 km/s RV ? Radial velocity
83- 84 I2 km/s e_RV ? rms uncertainty on RV
86- 92 A7 --- SpType Spectral type determined from comparison with
template spectra and UBV photometry
94- 97 F4.2 mag AK ? Absorption in K band
99-102 F4.2 mag e_AK ? rms uncertainty on AK
104-107 F4.2 kpc Dist ? Distance
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Note (1): Field designations are:
D1 = Danks 1
D2 = Danks 2
DBS2003 132 = [DBS2003] 132
Note (2): Stars are ordered as a function of their (non-)membership.
Note (3): D1-NN or D2-NN, will be [DCT2012] DN-NN in Simbad
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Byte-by-byte Description of file: table5.dat table6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Name Star name (1)
12- 20 F9.5 deg RAdeg Right ascension (J2000)
22- 31 F10.6 deg DEdeg Declination (J2000)
33- 37 F5.2 mag <Ksmag> Mean Ks magnitude
39- 43 F5.2 [mag] log(e_<Ksmag>) Log of mean Ks magnitude error
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Note (1): D1-NNNN for Danks 1, D2-NNNN for Danks 2, RCW79-NNNN for RCW 79.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 03-Dec-2014