Luminosity and Mass Function of the Galactic open cluster NGC 2422

Luminosity and Mass Function of the Galactic open cluster NGC 2422

Authors:
L. Prisinzano (1),
G. Micela (2),
S. Sciortino (2),
F. Favata (3) ((1) Universita’ di Palermo, Italy (2) INAF – OAPA, Italy, (3) ESA, ESTEC, The Netherlands)

Comments: 12 pages, 8 ps figures, in press in Astronomy and Astrophysics

We present UBVRI photometry of the open cluster NGC 2422 (age $sim 10^8$ yr)
down to a limiting magnitude $Vsimeq19$. These data are used to derive the
Luminosity and Mass Functions and to study the cluster spatial distribution. By
considering the color-magnitude diagram data and adopting a representative
cluster main sequence, we obtained a list of candidate cluster members based on
a photometric criterion. Using a reference field region and an iterative
procedure, a correction for contaminating field stars has been derived in order
to obtain the Luminosity and the Mass Functions in the $M=0.4-3.5 M_odot$
range. By fitting the spatial distribution, we infer that a non-negligible
number of cluster stars lies outside our investigated region. We have estimated
a correction to the Mass Function of the cluster in order to take into account
the “missing” cluster stars. The Present Day Mass Function of
gc2422 can be
represented by a power-law of index $alpha = 3.07 pm0.08 $ (rms) — the
Salpeter Mass Function in this notation has index $alpha = 2.35$ — in the
mass range $ 0.9 leq M/M_odotleq 2.5 $. The index $alpha$ and the total
mass of the cluster are very similar to those of the Pleiades.

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