In astronomy, the Kennicutt–Schmidt Law (or simply Schmidt Law) is an empirical relation between the gas density and star formation rate (SFR) in a given region. The relation was first examined by Maarten Schmidt in a 1959 paper in which he proposed that the SFR surface density scales as some positive power
n
of the local gas surface density. i.e.
Σ
S
F
R
∝
(
Σ
g
a
s
)
n
.
In general the SFR surface density
(
Σ
S
F
R
)
is in units of solar masses per year per square parsec
(
M
⊙
yr
−
1
pc
−
2
)
and the gas surface density in grams per square parsec
(
g
pc
−
2
)
. Using an analysis of gaseous helium and young stars in the solar neighborhood, the local density of white dwarfs and their luminosity function, and the local helium density, Schmidt suggested a value of
n
≈
2
(and very likely between 1 and 3). All of the data used were gathered from the Milky Way, and specifically the solar-neighborhood.
More recently, Robert Kennicutt examined the connection between gas density and SFR for nearly 100 nearby galaxies to estimate a value of
n
=
1.4
±
0.15
.
