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** THEORETICAL ISOCHRONES IN SEVERAL PHOTOMETRIC SYSTEMS **
** Second (isoc_photsys.01) release, Dec 2003 **
** (with the addition of isoc_2mass in July 2004) **
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The present database (isoc_photsys.01) contains the data files
mentioned in
"Theoretical isochrones in several photometric systems
II. The Sloan Digital Sky Survey UGRIZ system"
by L. Girardi, E.K. Grebel, M. Odenkirchen, C. Chiosi,
2004, to appear in Astronomy & Astrophysics.
together with links to the previous database (isoc_photsys.00):
"Theoretical isochrones in several photometric systems
I. Johnson-Cousins-Glass, HST/WFPC2, HST/NICMOS,
Washington, and ESO Imaging Survey filter sets"
by L. Girardi, G. Bertelli, A. Bressan, C. Chiosi,
M.A.T. Groenewegen, P. Marigo, B. Salasnich, and A. Weiss,
2002, Astronomy & Astrophysics, 391, 195.
and data files from a related paper:
¨Theoretical isochrones compared to 2MASS observations:
Open clusters at nearly solar metallicity¨, by
Ch. Bonatto, E. Bica, L. Girardi, 2004,
Astronomy & Astrophysics, 415, 571.
Please refer to these papers for a complete description of the
models. And, when referring to the models, please refer also
to the original source of evolutionary data, listed in
Table 1 there (see also
http://pleiadi.pd.astro.it/isoc_photsys.00.html#table ).
The present files correspond to the "official" release that
accompany the publication of the paper by A&A. They may
differ slightly from data informally distributed in
precedence.
The present files will not be changed, unless for the
correction of small typos that may still be present. Any
future extension will be _added_ into separate directories,
with different names.
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MAIN DIRECTORIES / PHOTOMETRIC SYSTEMS
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All data files are separated in directories according to
the photometric system under consideration:
isoc_ubvrijhk --> for Johnson-Cousins-Glass
isoc_wfpc2ab --> for HST/WFPC2, ABmag
isoc_wfpc2st --> for HST/WFPC2, STmag
isoc_wfpc2vega --> for HST/WFPC2, VEGAmag
isoc_nicmosab --> for HST/NICMOS, ABmag
isoc_nicmosst --> for HST/NICMOS, STmag
isoc_nicmosvega --> for HST/NICMOS, VEGAmag
isoc_washington --> for Washington
isoc_eis --> for EIS WFI + SOFI
isoc_emmi --> for EIS EMMI
isoc_sloan --> for SDSS, ABmag
isoc_2mass --> for 2MASS, VEGAmag
Herebelow, these directories will be generically referred to
as isoc_.
Each one of the isoc_ directories contain:
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TABLES OF BOLOMETRIC CORRECTIONS
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Bolometric corrections, computed according to Eq. 7, are
tabulated for all input spectra (Sect. 3) and filters.
The following files are available:
isoc_/bctab_m25.dat --> BCs for [M/H]=-2.5
isoc_/bctab_m20.dat --> BCs for [M/H]=-2.0
isoc_/bctab_m15.dat --> BCs for [M/H]=-1.5
isoc_/bctab_m10.dat --> BCs for [M/H]=-1.0
isoc_/bctab_m05.dat --> BCs for [M/H]=-0.5
isoc_/bctab_p00.dat --> BCs for [M/H]= 0.0
isoc_/bctab_p05.dat --> BCs for [M/H]=+0.5
where [M/H] is related to the initial metal mass fraction Z by
[M/H] = log10(Z/Zsun)
(This is just an aproximation, but is accurate enough for
most purposes).
Each one of these files contains N columns with:
Column (1) n --> sequential number for the spectra;
Column (2) Teff --> effective temperature (in K);
Column (3) logg --> logarithm of surface gravity (in cgs units);
Columns (4) to (N) --> bolometric correction BC for each filter.
Given BC for a filter, the corresponding stellar absolute
magnitude is
M_absolute = M_bolometric - BC
A bolometric correction of -999999 means that the input
spectra presents null flux (infinite magnitude) in that
filter pass-band. This occurs rarely, and just for very cool
stars in UV filters.
Inside a file, two main blocks of BCs are included:
- First, those derived from BDdusty1999 (Allard et al. 1999) +
ATLAS9 (Castelli et al. 1997) + blackbody, totalling ~600
spectra in a sequence of increasing Teff and logg;
- Second, those derived from the modified Fluks et al. (1994)
M-giant spectra (10 spectra), in a sequence of decreasing
Teff.
Blackbody and M-giant spectra have arbitrarily been given
logg=5.0 and logg=0.0, respectively.
These tables can be easily interpolated for any value of
logg and Teff. For constructing the following isochrones,
we adopt bi-linear interpolations in logg and log(Teff). Any
time we go out of the available range of logg, the nearest
extreme value for that Teff is used. In this way we avoid
risky extrapolations of BC values.
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TABLES OF ISOCHRONES
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For each photometric system, the following isochrone files
are available:
------------------------------------------------------------------
FILENAME COMPOSITION REFERENCE
---------extended-set---------------------------------------------
isoc_/isoc_z0.dat [Z=0.0, Y=0.230] Ma01
isoc_/isoc_z0004.dat [Z=0.0001, Y=0.230] Gi01+Gi96
isoc_/isoc_z0004.dat [Z=0.0004, Y=0.230] Gi00+Be94
isoc_/isoc_z001.dat [Z=0.001, Y=0.230] Gi00
isoc_/isoc_z004.dat [Z=0.004, Y=0.240] Gi00+Be94
isoc_/isoc_z008.dat [Z=0.008, Y=0.250] Gi00+Be94
isoc_/isoc_z019.dat [Z=0.019, Y=0.273] Gi00+Be94
isoc_/isoc_z030.dat [Z=0.030, Y=0.300] Gi00
---------classic--------------------------------------------------
isoc_/isoc_z019nov.dat [Z=0.019, Y=0.273] Gi00
---------solar-scaled-vs.alpha-enhanced---------------------------
isoc_/isoc_z008s.dat [Z=0.008, Y=0.250] Sa00
isoc_/isoc_z019s.dat [Z=0.019, Y=0.273] Sa00
isoc_/isoc_z040s.dat [Z=0.040, Y=0.320] Sa00
isoc_/isoc_z040s.dat [Z=0.070, Y=0.390] Sa00
isoc_/isoc_z008a.dat [Z=0.008, Y=0.250] Sa00
isoc_/isoc_z019a.dat [Z=0.019, Y=0.273] Sa00
isoc_/isoc_z040a.dat [Z=0.040, Y=0.320] Sa00
isoc_/isoc_z040a.dat [Z=0.070, Y=0.390] Sa00
---------detailed-TPAGB-------------------------------------------
isoc_/isoc_z004m.dat [Z=0.004, Y=0.240] MG01
isoc_/isoc_z008m.dat [Z=0.008, Y=0.250] MG01
isoc_/isoc_z019m.dat [Z=0.019, Y=0.273] MG01
------------------------------------------------------------------
The above table is an over-simplified version of paper's Table 1,
where all basic details and references are found. The user is
strongly urged to look at that table (also available at
http://pleiadi.pd.astro.it/isoc_photsys.00.html#table )
to find the basic differences between isochrone files.
Moreover, the user is _strongly_ encouraged to refer to the
original papers, listed in the last column above. Those are the
places where the real important information is found: the
prescriptions for the several physical processes envolved in
the calculations.
Each file contains a complete series of isochrones with
log(age/yr) values at equally spaced intervals of
Delta(log age)=0.05 (i.e., two consecutive isochrones
differ by only 12 percent in their ages.)
Each one of these files contains
HEADER LINE: with the exact age and metallicity value of
the isochrone;
followed by N columns with:
Column (1) log(age/yr) --> logarithm of the age (in yr);
Column (2) M_ini --> initial mass of the star (in solar units);
Column (3) M_act --> actual mass of the star, i.e., the mass
obtained considering the previous history of mass-loss;
Column (4) logL/Lo --> logarithm of surface luminosity (in solar
units), log(L/Lsun);
Column (5) logTef --> logarithm of effective temperature (in K),
log(Teff/K);
Column (6) logG --> logarithm of surface gravity (in cgs units);
Column (7) Mbol --> absolute bolometric magnitude;
Columns (8) to (N-1) --> absolute magnitude in each pass-band;
Column (N) FLUM --> indefinite integral of the Salpeter IMF by
number (see Gi00 for more details);
From the above quantities, stellar colours can be easily
derived.
We remark that the initial mass M_ini (and not M_act) is the
useful quantity for population synthesis calculations,
since together with the initial mass function it determines the
relative number of stars in different sections of the isochrones.
Also the quantity FLUM can be used for this purpose.
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INTEGRATED MAGNITUDES OF SINGLE-BURST STELLAR POPULATIONS
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For each isochrone file, there's also a file containing the
integrated absolute magnitudes of the corresponding single-burst
stellar populations (SSP). The available files are:
------------------------------------------------------------------
FILENAME COMPOSITION REFERENCE
---------extended-set---------------------------------------------
isoc_/sspmag_z0.dat [Z=0.0, Y=0.230] Ma01
isoc_/sspmag_z0004.dat [Z=0.0001, Y=0.230] Gi01+Gi96
isoc_/sspmag_z0004.dat [Z=0.0004, Y=0.230] Gi00+Be94
isoc_/sspmag_z001.dat [Z=0.001, Y=0.230] Gi00
isoc_/sspmag_z004.dat [Z=0.004, Y=0.240] Gi00+Be94
isoc_/sspmag_z008.dat [Z=0.008, Y=0.250] Gi00+Be94
isoc_/sspmag_z019.dat [Z=0.019, Y=0.273] Gi00+Be94
isoc_/sspmag_z030.dat [Z=0.030, Y=0.300] Gi00
---------classic--------------------------------------------------
isoc_/sspmag_019nov.dat [Z=0.019, Y=0.273] Gi00
---------solar-scaled-vs.alpha-enhanced---------------------------
isoc_/sspmag_z008s.dat [Z=0.008, Y=0.250] Sa00
isoc_/sspmag_z019s.dat [Z=0.019, Y=0.273] Sa00
isoc_/sspmag_z040s.dat [Z=0.040, Y=0.320] Sa00
isoc_/sspmag_z040s.dat [Z=0.070, Y=0.390] Sa00
isoc_/sspmag_z008a.dat [Z=0.008, Y=0.250] Sa00
isoc_/sspmag_z019a.dat [Z=0.019, Y=0.273] Sa00
isoc_/sspmag_z040a.dat [Z=0.040, Y=0.320] Sa00
isoc_/sspmag_z040a.dat [Z=0.070, Y=0.390] Sa00
---------detiailed-TPAGB-------------------------------------------
isoc_/sspmag_z004m.dat [Z=0.004, Y=0.240] MG01
isoc_/sspmag_z008m.dat [Z=0.008, Y=0.250] MG01
isoc_/sspmag_z019m.dat [Z=0.019, Y=0.273] MG01
------------------------------------------------------------------
Again, a look at the complete Table 1 (available at
http://pleiadi.pd.astro.it/isoc_photsys.00.html#table )
is necessary for a better description of the different sources
of data.
Each one of these files contains N columns with:
Column (1) Z --> mass fraction of metals Z;
Column (2) Age --> age in yr;
Column (3) Mbol --> integrated absolute bolometric magnitude;
Columns (4) to (N) --> integrated absolute magnitude in each
pass-band;
Integrated magnitudes are computed assuming
- The Kroupa (2001) initial mass function (IMF) in its
corrected version (his eq. 6); it has a nearly-Salpeter slope
(alpha=2.30 instead of 2.35) for all masses higher than
1 Msun.
- A total SSP initial mass equal to 1.0 Msun; in other words,
the magnitudes are given per unit Msun of a SSP.
This means that, for a SSP of initial mass M_T (in Msun), its
integrated magnitude is given by the number in the table plus
the quantity -2.5*log10(M_T) .
Anyway, the user should keep in mind that the absolute value
of this integrated magnitude depends heavily on the assumed
IMF. This because, for any typical IMF, a substantial fraction
of the initial mass goes into light stars (lighter than say
1 Msun), whose contribution to the integrated light is
generally negligible (except for very large ages). The same
comment applies to any mass-to-light ratio eventually derived
from our tables.
In the case of Kroupa's IMF, the fraction of stars heavier than
1 Msun is equal to Fh_KroupaIMF=0.387. If one wants to adopt a
different IMF for the stars with M < 1 Msun, this fraction can
be used to roughly estimate the new integrated magnitudes per
unit initial mass: they are given by adding the quantity
-2.5*log10[Fh_newIMF/Fh_KroupaIMF]
to the numbers in our tables.
On the other hand, integrated colours depend just little on the
details of the IMF.
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REFERENCES
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A more complete list can be found in the papers.
Allard F., Hauschildt P.H., Alexander D.R., Tamanai A., Ferguson
J.W., 2000a, in proceed. of "From giant planets to cool
stars", ASP Conf. Series v. 212, (eds.) C.A. Griffith &
M.S. Marley, p. 127 (at
ftp://ftp.ens-Lyon.fr/pub/users/CRAL/fallard/BCdusty1999 )
Bertelli G., Bressan A., Chiosi C., Fagotto F., Nasi E., 1994,
A&AS 106, 275 (Be94)
Castelli F., Gratton R.G., Kurucz R.L., 1997, A&A 318, 841
(NOVER models at http://cfaku5.harvard.edu/grids.html )
Fluks M.A, Plez B., The P.S., et al., 1994, A&AS 105, 311
Girardi L., Bressan A., Chiosi C., Bertelli G., Nasi E., 1996,
A&AS 117, 113 (Gi96)
Girardi L., Bressan A., Bertelli G., Chiosi C., 2000, A&AS 141, 371
(Gi00)
Girardi L., 2001, unpublished tracks (Gi01)
Kroupa P., 2001, MNRAS 322, 231
Marigo P., Girardi L., Chiosi C., Wood P.R., 2001, A&A 371, 152
(Ma01)
Marigo P., Girardi L., 2001, A&A 377, 132 (MG01)
Salasnich B., Girardi L., Weiss A., Chiosi C., 2000, A&A 361, 1023
(Sa00)