We predict the local disk star counts through a galactic code which adopts stellar models (evolutionary tracks up to the white dwarf phase) together with a star formation rate (SFR) and an initial mass function (IMF). Results are compared with the disk luminosity function and the local white dwarf (WD) density to obtain constraints on IMF and SFR. We take into account three different ages (7.5, 9, 12 Gyr) and several star formation histories. Our analysis for a 7.5 Gyr disk and a flat SFR shows that a simple power law IMF (Salpeter like) for M>0.6Msun reproduces both the above observational quantities and the WD luminosity function cut-off. This result doesn't hold for a disk age larger than ~ 9 Gyr. In general, an increase of the disk age determines too many faint WDs. Even a steeper IMF exponent in the WD progenitor mass range cannot lead to agreement with observations.
Local disk star counts: observational constraints on the stellar IMF
CIGNONI, MICHELE;PRADA MORONI, PIER GIORGIO;DEGL'INNOCENTI, SCILLA
2003-01-01
Abstract
We predict the local disk star counts through a galactic code which adopts stellar models (evolutionary tracks up to the white dwarf phase) together with a star formation rate (SFR) and an initial mass function (IMF). Results are compared with the disk luminosity function and the local white dwarf (WD) density to obtain constraints on IMF and SFR. We take into account three different ages (7.5, 9, 12 Gyr) and several star formation histories. Our analysis for a 7.5 Gyr disk and a flat SFR shows that a simple power law IMF (Salpeter like) for M>0.6Msun reproduces both the above observational quantities and the WD luminosity function cut-off. This result doesn't hold for a disk age larger than ~ 9 Gyr. In general, an increase of the disk age determines too many faint WDs. Even a steeper IMF exponent in the WD progenitor mass range cannot lead to agreement with observations.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
