Contents:

1.Introduction
2.The model
3.Which version should I use?
4.Running the model
5.The output
6.Including "exotic" objects...
7.Download PINGAS

1-) INTRODUCTION:

The code PINGAS has been developed by Roberto Ortiz and Jacques Lepine to
predict star counts throughout the Galaxy, in several
photometric bands as a function of the direction (l,b) and the limiting
magnitude. A former version was first published by Ortiz & Lepine in
1995 (Astronomy & Astrophysics, 279, 90). Since then, the program has
had many modifications concerning the structure of the code as well
as the hypotheses assumed about the different populations that compose
the Galaxy. The present version does not intend to be an ultimate one,
because models can ever be improved, as new and better data become
available from infrared sky surveys. You are encouraged to make comments
and/or suggestions to the authors whenever you want. We apologize for
mistakes that might be eventually found in the code and the authors would
be grateful if you let them know about them. Keep in mind that
the program is being continuously updated. To be informed about the
last modifications you are invited to send an e-mail to Roberto Ortiz,
(ortiz@cce.ufes.br). Doing so, we will include you in our mailing list.

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2-) THE MODEL:

Below, we present a brief description about the hypotheses assumed
by this model.

The model assumes different stellar populations to compose the Galaxy:
a young disk, an intermediate disk, an old disk, a spheroid (that
represents both the bulge and the halo), a bar (inside the bulge), and
set of four spiral arms. Each component is constituted of a  "population"
i.e. a mixture of stars of different spectral types and luminosity
classes. The proportion of different types of stars in a given component
does not vary with position in space. As examples of different populations 
associated with different components, supergiants are present in the spiral
arms and in the bulge, O and B stars in the spiral arms only; the young
disk contains more early-type stars than the old disk; the intermediate
disk is used to represent the distribution of carbon stars; the population
of the spheroid, which represents both the bulge and the halo, is almost
the same as that of the old disk.

Conversely, the density of each type of star, specified by its spectral
type and luminosity (or special classification), at a given position in
the Galaxy, is distributed among the several components. The densities
corresponding to each component in the solar neighbourhood are specified
in the input table. The conventions for the classification of stars are as
follows:

I) For the spectral type:

O = 0
B = 1
A = 2
F = 3
G = 4
K = 5
M = 6
AGB, O-rich = 8
AGB, C-rich = 9

II) For the luminosity class:

3 = supergiants
2 = giants
1 = main sequence
0 = AGB stars

For the spectral sequence, sub-classes are represented at the first
decimal place. Ex.: A5 = 2.5, G2 = 4.2, M4.5 = 6.45, etc.

Each component is described by a different spatial distribution, based
on arguments that can be found in the literature. You are encouraged to
look at it if you are not familiar with the expressions listed below.
The young and the old disks are represented by a Kormendy disk
(Kormendy 1977, ApJ 217, 406), adopting n=1. The spheroidal component
is represented by the Hernquist distribution (Hernquist, 1990, ApJ 356,
359) that resembles de Vaucouleurs's expression but has the advantage
that it is easily integrable. The intermediate disk is adopted for the
carbon stars population only, and it does not have radial dependence,
since it has not been found in galactic structure studies (Guglielmo et
al. 1998, A&A 334, 609). The density of all disks drops exponentially
with |z|, the distance from the galactic plane.
As a last update, a bar has been included, according to the suggestion
of Kent et al. (1991, ApJ 378, 131) and fitted by Dwek et al. (1995,
ApJ 445, 716). A full description of the present model is being prepared
by the authors.

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3-) WHICH VERSION SHOULD I USE?

The model is available in four versions concerning the presentation of
the results (output). One should choose the more appropriate version for
each case. Of course, all versions produce the same results for
the same inputs of wavelength, sensitivity and direction. A summary is
given below:

i) pingas1.f
Predicts star counts (number/square degree) for B,V,R,I,J,H,K,L,[12],
and [25] IRAS bands. The output is a table showing counts for each
spectral type and luminosity class, discriminating each population.

ii) pingas2.f
Predicts star counts (number/square degree) for B,V,R,I,J,H,K,L,[12],
and [25] IRAS bands. The output is a two column table (colour, to be
chosen, and counts) that can eventually be used to make a histogram.
It does not discriminate counts by spectral type and is more adequate for
comparison with results obtained with plain surveys, especially in two-
colour.

iii) pingas3.f
The same as version I, but for I,J,H,K near-infrared plus ISOGAL bands.
Useful for comparison between DENIS, 2-MASS and ISOGAL surveys.

iv) pingas4.f
The same as version II, but for I,J,H,K and ISOGAL bands.

All models require the file galaxy.dat. Also, for pingas1 and pingas2
hess7.dat is needed while for pingas3 and pingas4 hess8.dat is
required. You have to copy those files too.

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4-) RUNNING THE MODEL:

The model is interactive. Modern workstations and PC's can run it in
a few seconds, so there's no need to submit jobs. The step of integration
dDRHO is taken as 10 parsecs but it can be changed for quicker run.
Remember: the greater dDRHO, the shorter the integration time, but on
the other hand, less accurate will be what you get. We suggest you to
keep the default value of 10 parsecs because it represents a good
compromise between CPU time and accuracy.

Below you'll find a simulation of each version:

I- pingas1

When you run the model, it will ask you:

------------------------------------------------
 BAND? (B,V,R,I,J,H,K,L,12,25)
------------------------------------------------

Choose the band you want to predict the counts (uppercase) and press
ENTER. Then you will get:

------------------------------------------------
 Longitude (0 < l < 360), latitude (-90 < b < +90)
------------------------------------------------

Enter the longitude and latitude of the direction you are interested,
in (decimal) degrees, separated by a comma or a space. If the direction
chosen is one of the galactic poles the longitude is irrelevant,
but you have to enter a value, whatever it is.
The next question will be:

------------------------------------------------
 Inicial lim. mag., final lim.mag., step
------------------------------------------------

For example, if you are interested in counts up to magnitude 9.0,
enter: 9.0 9.0 0.0. This will make the program compute all stars
brighter than 9th magnitude.

You can also run the program once, like a loop, for different limiting
magnitudes, instead of running it several times. Suppose you are
interested in knowing counts up to 9th, 10th, 11th and 12th magnitudes
for a specific band and direction. In this case you should answer:
9.0 12.0 1.0. This can be useful to make log(N) x limit. mag. diagrams.

Next question will be:

-------------------------------------------------
 The model permits you to include a particular dark
  cloud, at a distance to be chosen.
 Do you want to include it ?(Y/N)
-------------------------------------------------

The model already takes into account interestellar extinction, but you
can include some additional extinction at a certain distance if you
want, like a simulation of a particular dark cloud, for example.
If you don't want it, answer N, otherwise answer Y and the
program will ask you:

-------------------------------------------------
 Distance to the cloud (in pc), visual extinction
-------------------------------------------------

For Orion A you should answer 400. 10., for example. In this case you
would have chosen the distance of 400 parsecs and visual extinction of 10
visual magnitudes. Beware that even if you choose an INFRARED
band to be computed (the first question you got when you ran the
program) the extinction of a particular dark cloud has to be given
for the VISUAL band. Internally the program will convert it to the value
corresponding to the band you have required.

The last question is:

--------------------------------------------------
 Do you want a short (S) or a detailed (D) report?
--------------------------------------------------

The S letter will give you as output the input parameters and the total
counts, while D will provide you a full list of counts, ordered by
spectral type and luminosity class.

II- pingas2

When executing, the program will show you the photometric bands
available. You have to choose two bands, because the output will be
given in counts as a function of the colour. Look at the table shown
in the screen and enter the numbers corresponding to the bands that you
are interested in, separated by a comma or a space. For example,
enter 7,8 for K-L colour.

After having entered the colour, the program will ask you which band is
going to be limited in magnitude. Of course, it is one of the two bands
you chose in the previous question. That band will be used for the
calculus of the volume where stars are counted. The other band will
be used simply to compose the colour, as you would get if performing a
survey.

Next, the program will ask you the range of magnitudes to be considered.
For example, if you are interested in the number of stars between 12th
and 13th magnitudes, in the band defined in the last question then type
12, 13 and then ENTER. If you want to know the number of stars up to 13th
magnitude then enter something like 0.,13. to obtain the number of
stars between 0 and 13th magnitude. In this case, is important that,
the first number has to be small but not necessarily null. Choosing
-10,13 or +2,13 would not change the results significantly, because the
number of bright stars is generally negligible when compared with the
upper limiting magnitude.

Next, you will be asked about the direction to be considered. Enter
longitude and longitude, separated by a comma or space.

Finally the program will ask you whether you want to include an extra
dark cloud. See item I for details.
III- pingas3 & pingas4

For pingas3 the procedure is the same as for pingas1 but the
bands available are different. The same correspondence is valid for
pingas2 and pingas4.

----------------------------------------------------------

5-) THE OUTPUT

The output is written in a file named sortie.#, where # is the version
of the program that you have used. The values are given in number of
sources by square degree or its logarithm log(N), when specified. When
running the model for a set of limiting magnitudes the program gives
also A, which is differential count, taken as the difference
N(m)-N(m-dm), where dm is the increment in magnitude that you entered.
In the same file you will find also the parameters read from the file
galaxy.dat as well as the values that you have entered.

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6-) INCLUDING "EXOTIC" OBJECTS ...

The code permits you to include other objects of your choice, such as
planetary nebulae, HII regions, pulsars, etc. You don't need to change
the source code, just include the objects that you want in the file
"hess#". You will need to enter a name, a code for spectral
type and luminosity class, the density, the half-dispersion in magnitude
and the absolute magnitude in the various bands. Remember that the
codes for spectral type and luminosity will define the space
distribution, so these values have to be compatible with the real
distribution of the objects in the Galaxy. You might also delete
objects that you are not interested but the total counts of course
will be underestimated.

R.O.
Vitoria, 06/02/2003

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