scholarly journals Hα and FUV luminosities from a stochastically formed stellar population

2011 ◽  
Vol 7 (S284) ◽  
pp. 53-55
Author(s):  
Nidia Lugo Lopez L. ◽  
Gladis Magris C. ◽  
Antonio Parravano
Keyword(s):  
Power Law ◽  
Surface Brightness ◽  
Stellar Population ◽  
Mass Function ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Low Surface Brightness ◽  
Low Surface Brightness Galaxies

AbstractIt has been observed that the ratio of Hα to FUV luminosity (LHα/LFUV) is lower in low surface brightness galaxies. This behaviour has been attributed to systematic variations of the upper mass end and/or the slope of the Initial Mass Function (IMF) Meurer et al. (2009) and Lee et al. (2009)). However these hypotheses do not explain the observed scatter in luminosity ratio (LHα/LFUV). We present a model for the total LHα and LFUV luminosity arising from a randomly populated IMF following the Salpeter power law and the clustering law of Oey & Clarke (2007).

scholarly journals The stellar population and initial mass function of NGC 1399 with MUSE

2018 ◽  
Vol 479 (2) ◽  
pp. 2443-2456 ◽  
Author(s):  
Sam P Vaughan ◽  
Roger L Davies ◽  
Simon Zieleniewski ◽  
Ryan C W Houghton
Keyword(s):  
Stellar Population ◽  
Mass Function ◽  
Initial Mass Function ◽  
Initial Mass

scholarly journals New indications on the Galactic bulge IMF by microlensing surveys

2007 ◽  
Vol 3 (S245) ◽  
pp. 367-368
Author(s):  
L. Mancini ◽  
S. Calchi Novati
Keyword(s):  
Mass Spectrum ◽  
Stellar Population ◽  
Mass Function ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Galactic Bulge

AbstractBasing on recent microlensing observations, we analyse the mass spectrum of the Galactic bulge stellar population and study the slope of the initial mass function.

scholarly journals The influence of star clusters on galactic disks: new insights in star-formation in galaxies

2008 ◽  
Vol 4 (S254) ◽  
pp. 209-220
Author(s):  
Pavel Kroupa
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Stellar Population ◽  
Dwarf Galaxy ◽  
Star Clusters ◽  
Mass Function ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Disk Galaxies ◽  
Galactic Disks

AbstractStars form in embedded star clusters which play a key role in determining the properties of a galaxy's stellar population. A large fraction of newly born massive stars are shot out from dynamically unstable embedded-cluster cores spreading them to large distances before they explode. Embedded clusters blow out their gas once the feedback energy from the new stellar population overcomes its binding energy, leading to cluster expansion and in many cases dissolution into the galaxy. Galactic disks may be thickened by such processes, and some thick disks may be the result of an early epoch of vigorous star-formation. Binary stellar systems are disrupted in clusters leading to a lower fraction of binaries in the field, while long-lived clusters harden degenerate-stellar binaries such that the SNIa rate may increase by orders of magnitude in those galaxies that were able to form long-lived clusters. The stellar initial mass function of the whole galaxy must be computed by adding the IMFs in the individual clusters. The resulting integrated galactic initial mass function (IGIMF) is top-light for SFRs < 10 M⊙/yr, and its slope and, more importantly, its upper stellar mass limit depend on the star-formation rate (SFR), explaining naturally the mass–metallicity relation of galaxies. Based on the IGIMF theory, the re-calibrated Hα-luminosity–SFR relation implies dwarf irregular galaxies to have the same gas-depletion time-scale as major disk galaxies, implying a major change of our concept of dwarf-galaxy evolution. A galaxy transforms about 0.3 per cent of its neutral gas mass every 10 Myr into stars. The IGIMF-theory also naturally leads to the observed radial Hα cutoff in disk galaxies without a radial star-formation cutoff. It emerges that the thorough understanding of the physics and distribution of star clusters may be leading to a major paradigm shift in our understanding of galaxy evolution.

scholarly journals System initial mass function of the 25 Ori group from planetary-mass objects to intermediate/high-mass stars

2019 ◽  
Vol 486 (2) ◽  
pp. 1718-1740 ◽  
Author(s):  
Genaro Suárez ◽  
Juan José Downes ◽  
Carlos Román-Zúñiga ◽  
Miguel Cerviño ◽  
César Briceño ◽  
...  
Keyword(s):  
Power Law ◽  
Near Infrared ◽  
Mass Range ◽  
Mass Function ◽  
Initial Mass Function ◽  
High Mass ◽  
Initial Mass ◽  
Formation Mechanisms ◽  
Stellar Association ◽  
Planetary Mass

Abstract The stellar initial mass function (IMF) is an essential input for many astrophysical studies but only in a few cases has it been determined over the whole cluster mass range, limiting the conclusions about its nature. The 25 Orionis group (25 Ori) is an excellent laboratory for investigating the IMF across the entire mass range of the population, from planetary-mass objects to intermediate/high-mass stars. We combine new deep optical photometry with optical and near-infrared data from the literature to select 1687 member candidates covering a 1.1° radius area in 25 Ori. With this sample we derived the 25 Ori system IMF from 0.012 to 13.1 M⊙. This system IMF is well described by a two-segment power law with Γ = −0.74 ± 0.04 for m &lt; 0.4 M⊙ and Γ = 1.50 ± 0.11 for m ≥ 0.4 M⊙. It is also well described over the whole mass range by a tapered power-law function with Γ = 1.10 ± 0.09, mp = 0.31 ± 0.03 and β = 2.11 ± 0.09. The best lognormal representation of the system IMF has mc = 0.31 ± 0.04 and σ = 0.46 ± 0.05 for m &lt; 1 M⊙. This system IMF does not present significant variations with the radii. We compared the resultant system IMF as well as the brown dwarf/star ratio of 0.16 ± 0.03 that we estimated for 25 Ori with that of other stellar regions with diverse conditions and found no significant discrepancies. These results support the idea that general star-formation mechanisms are probably not strongly dependent on environmental conditions. We found that the substellar and stellar objects in 25 Ori do not have any preferential spatial distributions and confirmed that 25 Ori is a gravitationally unbound stellar association.

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