J/A+A/534/A9 Synthetic spectra of galactic globular clusters (Sbordone+, 2011)
Photometric signatures of multiple stellar populations in Galactic globular
clusters.
Sbordone L., Salaris M., Weiss A., Cassisi S.
<Astron. Astrophys. 534, A9 (2011)>
=2011A&A...534A...9S 2011A&A...534A...9S
ADC_Keywords: Models, evolutionary ; Spectroscopy ; Clusters, globular
Keywords: stars: abundances - Hertzsprung-Russell and C-M diagrams - evolution -
globular clusters: general
Abstract:
We calculated synthetic spectra for typical chemical element mixtures
(i.e., a standard alpha-enhanced distribution, and distributions
displaying CN and ONa anticorrelations) found in the various
subpopulations harboured by individual Galactic globular clusters.
From the spectra we determined bolometric corrections to the standard
Johnson-Cousins and Stroemgren filters and finally predicted colours.
These bolometric corrections and colour-transformations, coupled to
our theoretical isochrones with the appropriate chemical composition,
provided us with a complete and self-consistent set of theoretical
predictions for the effect of abundance variations on the observed
cluster colour-magnitude diagrams.
Description:
We considered a reference isochrone from the BaSTI database
(http://www.oa-terqmo.inaf.it/BASI) (Pietrinferni et al.
2006ApJ...642..797P 2006ApJ...642..797P), with the following characteristics: an age of
12Gyr, helium mass fraction Y=0.246 and metal mass fraction Z=0.001,
which results in an iron abundance of [Fe/H]=-1.62 for the
alpha-enhanced metal mixture of the BaSTI models ([alpha/Fe]∼0.4).
Such an isochrone is representative for the first generation
population in a typical Galactic GC.
Three metal mixtures are considered.
The alpha-enhanced mixture employed in the BaSTI database
(Pietrinferni et al. 2006ApJ...642..797P 2006ApJ...642..797P), which corresponds to
typical first-generation subpopulations in Galactic GCs, is labelled
as 'reference'.
The first mixture representative of second-generation stars is
labelled 'CNONa1', and displays - compared to the reference
alpha-enhanced mixture - enhancements of N and Na by 1.8dex and 0.8dex
by mass, respectively, together with depletions of C and O by 0.6dex
and 0.8dex, respectively. This is the same metal distribution already
used in the calculations by Salaris et al. (2006ApJ...645.1131S 2006ApJ...645.1131S) and
Pietrinferni et al. (2009ApJ...697..275P 2009ApJ...697..275P).
An alternative composition for second-generation stars is labelled
'CNONa2'; it is the same as the CNONa1 mixture but for the enhancement
of N that in this case is equal to 1.44dex by mass. The important
difference between CNONa1 and CNONa2 'second-generation' mixtures is
that in the first case, at fixed Fe abundance, the C+N+O mass fraction
is enhanced by a factor of 2 compared to the reference composition,
whereas the CNONa2 mixture has the same CNO content (in both number
and mass fractions) as the reference composition, within 0.5%.
**************************************************************************
* *
* The synthetic fluxes (FITS files) will be available later *
* *
**************************************************************************
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 101 99 Abundances for all elements in the considered
mixtures
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Z Atomic number
4- 5 A2 --- El Element
7- 16 E10.5 --- fMass Reference fractional mass for Y=0.246
(Z=9.9937e-04)
18- 23 F6.3 --- [El] Reference abundance of element
(logN(El)-logN(H)+12)) for Y=0.246
25- 34 E10.5 --- fMass1 Fractional mass for CNONa1, Y=0.246
(Z=1.8343e-03)
36- 41 F6.3 --- [El]1 Abundance of element (logN(El)-logN(H)+12)
for CNONa1, Y=0.246
43- 49 F7.4 --- [El]1-[El] Difference between this mixture [El] and
reference mixture [El] for CNONa1, Y=0.246
51- 60 E10.5 --- fMass2 Fractional mass for CNONa1, Y=0.400
(Z=1.4597e-03)
62- 67 F6.3 --- [El]2 Abundance of element (logN(El)-logN(H)+12)
for CNONaI, Y=0.400
69- 75 F7.4 --- [El]2-[El] Difference between this mixture [El] and
reference mixture [El] for CNONa1, Y=0.400
77- 86 E10.5 --- fMass3 Fractional mass for CNONa2, Y=0.246
(Z=9.9937e-04)
88- 93 F6.3 --- [El]3 Abundance of element (logN(El)-logN(H)+12)
for CNONa2, Y=0.246
95-101 F7.4 --- [El]3-[El] Difference between this mixture [El] and
reference mixture [El] for CNONa2, Y=0.246
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 19-Sep-2011