J/MNRAS/375/1220 BVI photometry of young stars in 10 clusters (Mayne+, 2007)
Empirical isochrones and relative ages for young stars, and the
radiative-convective gap.
Mayne N.J., Naylor T., Littlefair S.P., Saunders E.S., Jeffries R.D.
<Mon. Not. R. Astron. Soc., 375, 1220-1240 (2007)>
=2007MNRAS.375.1220M 2007MNRAS.375.1220M
ADC_Keywords: Stars, pre-main sequence ; Photometry, UBVRI ; Clusters, open
Keywords: techniques: photometric - catalogues - stars: evolution -
stars: formation - Hertzsprung-Russell (HR) diagram -
stars: pre-main-sequence
Abstract:
We have selected pre-main-sequence (PMS) stars in 12 groups of
notional ages ranging from 1 to 35Myr, using heterogeneous membership
criteria. Using these members we have constructed empirical isochrones
in V, V-I colour-magnitude diagrams. This allows us to identify clearly
the gap between the radiative main sequence and the convective PMS
(the RC gap). We follow the evolution of this gap with age and show
that it can be a useful age indicator for groups less than =15 Myr
old. We also observe a reduction in absolute spreads about the
sequences with age. Finally, the empirical isochrones allow us to
place the groups in order of age, independently of theory. The
youngest groups can be collated into three sets of similar ages. The
youngest set is the ONC, NGC 6530 and IC 5146 (nominally 1Myr); next
Cep OB3b, NGC 2362, Ori and NGC 2264 (nominally 3Myr); and finally
Ori and IC 348 (nominally 45Myr). This suggests Cep OB3b is younger
than previously thought, and IC 348 older. For IC 348 the stellar
rotation rate distribution and fraction of stars with discs imply a
younger age than we derive. We suggest this is because of the absence
of O-stars in this cluster, whose winds and/or ionizing radiation may
be an important factor in the removal of discs in other clusters.
Description:
We present photometry in V, V-I and in some cases B-V for a range of
star forming regions. NGC2547, NGC7160, NGC2264, Cepheus OB3b, Sigma
Orionis, IC348 and h and chi Per.
A full description of the data can be found at:
http://www.astro.ex.ac.uk/people/timn/Catalogues
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
ngc2547.dat 136 141 NGC 2547 photometric catalog (tables 4-5)
ngc7160.dat 136 31512 NGC 7160 photometric catalog (tables 6-7)
ngc2264.dat 136 62276 NGC 2264 photometric catalog (tables 8-12)
cepob3b.dat 136 36534 Cepheus OB3b photometric catalog (tables 13-18)
sigori.dat 136 90390 sigma Ori photometric catalog (tables 19-21)
ic348.dat 136 7507 IC 348 photometric catalog (tables 22-27)
persei.dat 136 56482 h and chi Per photometric catalog (tables 28-29)
samples.dat 149 29 Samples of membership criteria
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Byte-by-byte Description of file: n*.dat c*.dat sigori.dat i*.dat p*.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Cluster Cluster name
11 I1 --- Cat [0/1]? 0 for Full photometric catalog
1 for All stars in FOV catalog
13- 26 A14 --- Sample Sample member code(s), in samples.dat
28- 33 F6.2 --- Field Field number.CCD number if available NNN.NN (1)
34- 38 I5 --- MNLSJ Star designation number from MNLSJ (2007)
40- 41 I2 h RAh Right ascension (J2000.0) (1)
43- 44 I2 min RAm Right ascension (J2000.0) (1)
46- 51 F6.3 s RAs Right ascension (J2000.0) (1)
53 A1 --- DE- Declination sign (J2000.0) (1)
54- 55 I2 deg DEd Declination (J2000.0) (1)
57- 58 I2 arcmin DEm Declination (J2000.0) (1)
60- 64 F5.2 arcsec DEs [0/60] Declination (J2000.0) (1)
66- 73 F8.3 pix Xpos X position
75- 82 F8.3 pix Ypos Y position
84- 89 F6.3 mag Vmag ?=99.999 Johnson V magnitude
91- 96 F6.3 mag e_Vmag ?=99.999 rms uncertainty on Vmag
98- 99 A2 --- q_Vmag Quality flag on Vmag (2)
101-107 F7.3 mag V-Ic ?=99.999 Cousins V-I colour index
109-114 F6.3 mag e_V-Ic ?=99.999 rms uncertainty on V-Ic
116-117 A2 --- q_V-Ic Quality flag on V-Ic (2)
119-125 F7.3 mag B-V ?=99.999 Johnson B-V colour index (3)
128-133 F6.3 mag e_B-V ?=99.999 rms uncertainty on B-V (3)
135-136 A2 --- q_B-V Quality flag on B-Vmag (2) (3)
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Note (1) : in ngc2264.dat, data from sample No. 26 (proper motion members):
- field number:
1.00 denotes a star from Walker (1956ApJS....2..365W 1956ApJS....2..365W)
2.00 denotes a star from Vasilevskis et al. (1965AJ.....70..797V 1965AJ.....70..797V)
- Positions are from 2MASS (Cat. II/246) via matching of ID's
through WEBDA. (http://www.univie.ac.at/webda)
- There are no Xpos and Ypos (set to 0.000).
Note (2): Quality flags are:
O = O.K.
N = Non-stellar
H = Aperture photometry used
E = Too close to CCD edge
B = Background fit failed
I = Ill-determined background
P = Position fit failed
S = Saturated
E = Too close to edge
F = Flagged pixel
R = Uncalibrated region
A = Absent input data
M = Negative (minus) counts
V = Variable
C = Large relative transparency correction (cloudy)
Note (3): For CepOB3b, B-V colour index unavailable.
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Byte-by-byte Description of file: samples.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Code Sample number
4- 24 A21 --- Type Type of data
25-149 A125 --- Ref References
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Acknowledgements:
Nathan Mayne, N.J.Mayne(at)exeter.ac.uk
(End) Patricia Vannier [CDS] 12-Apr-2007