Original mass function

The original mass function , and initial mass function , English Initial Mass Function (IMF) , describes how in an emerging star population , the distribution of the star looks reasonably.

Original mass function (different versions,
see literature information)

The original mass function was first derived in 1955 by Edwin Salpeter for the sun's surroundings. He suggested the following relationship for stars between about 0.4 and 10 solar masses :

{\ displaystyle dN \ propto M ^ {- \ alpha} dM}

With

exponent ${\ displaystyle \ alpha = 2 {,} 35}$
dN: the number of stars with a mass between M and M + dM per unit volume.

In this saltpetre function , massive stars are significantly rarer than low-mass stars. If this connection were continued towards very small masses, then the entire stellar mass would be dominated by very low-mass stars. Today's determinations of the original mass function, however, indicate a flattening of this relationship below 0.5 solar masses.

Below 0.1 solar masses, the universality of the original mass function seems to collapse: in this range the IMF varies between different star formation regions . This difference is not the result of dynamic interactions that accelerate the lighter stars out of these regions.

The explanation of the original mass function is an important task for models of star formation , especially since the function seems to vary little between different star formation regions.

literature

Edwin E. Salpeter : The luminosity function and stellar evolution . In: Astrophysical Journal , 121, 1955, pp. 161-167, ISSN 0004-637X , bibcode : 1955ApJ ... 121..161S .
Glen Miller, John Scalo: The initial mass function and stellar birthrate in the solar neighborhood . In: The Astrophysical Journal Supplement Series. 41, 1979, pp. 513-547, ISSN 0067-0049 .
John Scalo: The initial mass function of massive stars in galaxies. Empirical evidence. In: CWH de Loore, AJ Willis, P. Laskarides (eds.): Luminous stars and associations in galaxies. Symposium, Porto-Heli, Greece, May 26-31, 1985. D. Reidel Publishing Co., Dordrecht et al. a. 1986, pp. 451-466 ( Proceedings of the 116th symposium of the International Astronomical Union. ISSN 1743-9213 ).
Pavel Kroupa : On the variation of the initial mass function . In: Monthly Notices of the Royal Astronomical Society , 322, 2, 2001, pp. 231-246, ISSN 0035-8711 , arxiv : astro-ph / 0102155 preprint.
Pavel Kroupa: The initial mass function of stars. Evidence for uniformity in variable systems . In: Science , 295, 2002, pp. 82-91, ISSN 0036-8075 , arxiv : astro-ph / 0201098 preprint.
Christophe Becker, Estelle Moraux, Gaspard Duchêne, Thomas Maschberger, Warrick Lawson: Reverse dynamical evolution of Eta Chamaeleontis . arxiv : 1303.0193v1 preprint.