1 / 18

The low-mass part of the IMF From solar neighborhood to galactic implications

The low-mass part of the IMF From solar neighborhood to galactic implications. Mass-magnitude relations The Luminosity Function  The Mass Function The Substellar regime The galactic implication : M/L ratio. Gilles CHABRIER C.R.A.L., ENS-Lyon. Mass-Magnitude relationships.

keenan
Download Presentation

The low-mass part of the IMF From solar neighborhood to galactic implications

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The low-mass part of the IMFFrom solar neighborhood to galactic implications Mass-magnitude relations The Luminosity Function  The Mass Function The Substellar regime The galactic implication : M/L ratio GillesCHABRIER C.R.A.L., ENS-Lyon

  2. Mass-Magnitude relationships Mmagnitude ; mmass dN/dm = (dN/dM)(dm/dM)-1 MFLFm-M Constraints from M-dwarf binaries: m-MV, m-MK, m-MJ, m-MH down to 0.1 Msun(Delfosse et al. ‘00; Segransan et al. ‘03)

  3. The Galactic Disk Luminosity Function • Hipparcos data (MV<11) + nearby (< 5pc) sample (Dahn et al. ‘86) • Hipparcos + revised nearby sample (< 5 to 14 pc) (Reid et al. ‘02)  V complete to MV=16 • Local sample in IR bands (Henry & McCarthy ‘90)  Kcomplete to MK=10 Metallicity dispersion :[M/H] = 0 ± 0.2 Age dispersion :0.8  m  0.15 on MS for 5108 1010yr 

  4. Chabrier, review PASP 2003, 115, 763

  5. Chabrier, ApJ 2003, 586, L133

  6. The Brown Dwarf Domain The first stars • BDs discovered down to a few Mjup • Need probability distributions for : - age: P(t) = (D)-1t b(t´)dt´ (SFR) - mass: P(m) = m p(m´)dm´ (IMF) - spatial dist’n: P(r)= r r´2n(r´)dr´ (Chabrier ‘02, ‘03)

  7. The Mass-to-Light ratio Death of the stars : the supernovae • Dynamical arguments (TF relation) + CDM hierarchical simulations of spiral discs  M/L ≈ 1/2  Salpeter ~ 70% galactic mass in objects m<1 Msun • Metal fraction (O-yield) better reproduced if massive stars IMF between Salpeter and Scalo (Portinari, Sommer-Larsen, Tantalo, ‘03)

  8. CONCLUSIONS IMF reasonably well determined from 1Msun to a few Mjup Consistent with star+BD counts and galactic M/L ratio Determination of galactic baryonic (stars + BDs) budget consistent with: power-law for m>1 Msun (≈ <MJeans>) + lognormal for m<1 Msun Theoretical fundation :star formation triggered by dissipation of large scale turbulence + further frag’n (Padoan & Nordlund) Hint for increasing characteristic mass w/ increasing z (decreasing Z)

  9. Chabrier,PASP ‘03

More Related