2005/08/31 by D. Gouliermis, Dimitrios A. Gouliermis, W. Brandner +1
Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Flattening #Galaxies: Formation, Evolution, Phenomena #Galaxy #Initial mass function #Large Magellanic Cloud #Photometry (optics) #Physics #Population #Star formation #Stars #Stellar mass #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/500500
published as Astrophys.J.641:838-851,2006 · 16 pages in ApJ Journal format, 7 figures, Submitted to ApJ. The size of the postscript files of the images has been reduced because of disk space limitations
arxiv created 2005/08/31 · openalex publication_date 2006/04/14 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We present V - and I -equivalent HST WFPC2 stellar photometry of an area in the Large Magellanic Cloud (LMC), located to the west of the bar of the galaxy, which accounts for the general background field of its inner disk. The WFPC2 observations reach magnitudes as faint as V = 25 mag, and the large sample of more than 80,000 stars allows us to determine in detail the present-day mass function (PDMF) of the detected main-sequence stars, which is identical to the initial mass function (IMF) for masses M ≲ 1 M ☉ . The low-mass main-sequence mass function of the LMC field is found not to have a uniform slope throughout the observed mass range; i.e., the slope does not follow a single power law . This slope changes at about 1 M ☉ to become more shallow for stars with smaller masses down to the lowest observed mass of ~0.7 M ☉ , giving clear indications of flattening for even smaller masses . We verified statistically that for stars with M ≲ 1 M ☉ the IMF has a slope Γ around -2, with an indicative slope Γ ≃ -1.4 for 0.7 ≲ M / M ☉ ≲ 0.9, while for more massive stars the main-sequence mass function becomes much steeper with Γ ≃ -5. The main-sequence luminosity function (LF) of the observed field is in very good agreement with the Galactic LF as it was previously found. Taking into account several assumptions concerning evolutionary effects, which should have changed through time the stellar content of the observed field, we reconstruct qualitatively its IMF for the whole observed mass range (0.7 ≲ M / M ☉ ≲ 2.3), and we find that the number of observed evolved stars is not large enough to have affected significantly the form of the IMF, which thus is found almost identical to the observed PDMF.