The Effect of Star Formation History on the Inferred Stellar Initial Mass Function

2006 ◽  
Vol 636 (1) ◽  
pp. 149-157 ◽  
Author(s):  
Bruce G. Elmegreen ◽  
John Scalo
Keyword(s):  
Star Formation ◽  
Mass Function ◽  
Initial Mass Function ◽  
Star Formation History ◽  
Initial Mass ◽  
Formation History ◽  
Stellar Initial Mass Function

scholarly journals The stellar initial mass function of the solar neighbourhood revealed by Gaia

2019 ◽  
Vol 489 (2) ◽  
pp. 2377-2394 ◽  
Author(s):  
A Sollima
Keyword(s):  
Star Formation ◽  
Mass Function ◽  
Initial Mass Function ◽  
Star Formation History ◽  
Solar Neighbourhood ◽  
Initial Mass ◽  
Galactic Disc ◽  
Formation History ◽  
Stellar Initial Mass Function ◽  
Metallicity Distribution

Abstract I use a sample of more than 120 000 stars in the solar neighbourhood, with parallaxes, magnitudes and colours estimated with unprecedented accuracy by the second data release of the Gaia mission, to derive the initial mass function of the Galactic disc. A full-forward technique is used to take into account, for the population of unresolved binaries, the metallicity distribution and the star formation history, including their variation across the Galactic disc, as well as all the observational effects. The shape of the initial mass function is well represented by a segmented power law with two breaks at characteristic masses. It has a maximum at M ∼ 0.15 M⊙ with significant flattening (possibly a depletion) at lower masses and a slope of α = −1.34 ± 0.07 in the range 0.25 < M/M⊙ < 1. Above 1 M⊙, the initial mass function shows an abrupt decline with a slope ranging from α = −2.68 ± 0.09 to α = −2.41 ± 0.11, depending on the adopted resolution of the star formation history.

scholarly journals Comment on “An excess of massive stars in the local 30 Doradus starburst”

Science ◽  
2018 ◽  
Vol 361 (6400) ◽  
pp. eaat6506 ◽  
Author(s):  
Will M. Farr ◽  
Ilya Mandel
Keyword(s):  
Star Formation ◽  
Power Law ◽  
Ad Hoc ◽  
Massive Stars ◽  
Mass Function ◽  
Initial Mass Function ◽  
Star Formation History ◽  
Formation History ◽  
Power Law Exponent ◽  
Stellar Initial Mass Function

Schneider et al. (Reports, 5 January 2018, p. 69) used an ad hoc statistical method in their calculation of the stellar initial mass function. Adopting an improved approach, we reanalyze their data and determine a power-law exponent of 2.05−0.13+0.14. Alternative assumptions regarding dataset completeness and the star formation history model can shift the inferred exponent to 2.11−0.17+0.19 and 2.15−0.13+0.13, respectively.

scholarly journals PROBING THE STAR FORMATION HISTORY AND INITIAL MASS FUNCTION OF THEz∼ 2.5 LENSED GALAXY SMM J163554.2+661225 WITHHERSCHEL

2011 ◽  
Vol 742 (2) ◽  
pp. 108 ◽  
Author(s):  
Keely D. Finkelstein ◽  
Casey Papovich ◽  
Steven L. Finkelstein ◽  
Christopher N. A. Willmer ◽  
Jane R. Rigby ◽  
...  
Keyword(s):  
Star Formation ◽  
Mass Function ◽  
Initial Mass Function ◽  
Star Formation History ◽  
Initial Mass ◽  
Formation History

scholarly journals The Star Formation History and IMF in the LMC and SMC from Deep HST Imaging

1999 ◽  
Vol 190 ◽  
pp. 351-353
Author(s):  
J. Holtzman ◽  
J. R. Mould ◽  
J. S. Gallagher
Keyword(s):  
Star Formation ◽  
Mass Function ◽  
Initial Mass Function ◽  
Solar Neighborhood ◽  
Star Formation History ◽  
Initial Mass ◽  
Luminosity Functions ◽  
Formation History

We present deep photometry to V ~ 27.5 obtained with the HST in several fields in the LMC and the SMC. We derive luminosity functions for the faintest stars which are consistent with an initial mass function similar to that of the solar neighborhood, although moderate variations are not excluded. We discuss implications of these observations for the star formation history in these regions of the LMC and SMC.

Recovering the star formation history of galaxies through spectral fitting: Current challenges

2019 ◽  
Vol 15 (S359) ◽  
pp. 386-390
Author(s):  
Lucimara P. Martins
Keyword(s):  
Star Formation ◽  
Mass Function ◽  
Initial Mass Function ◽  
Star Formation History ◽  
Stellar Spectra ◽  
Spectral Fitting ◽  
Formation History ◽  
History Of ◽  
Nearby Galaxies ◽  
Extract Information

AbstractWith the exception of some nearby galaxies, we cannot resolve stars individually. To recover the galaxies star formation history (SFH), the challenge is to extract information from their integrated spectrum. A widely used tool is the full spectral fitting technique. This consists of combining simple stellar populations (SSPs) of different ages and metallicities to match the integrated spectrum. This technique works well for optical spectra, for metallicities near solar and chemical histories not much different from our Galaxy. For everything else there is room for improvement. With telescopes being able to explore further and further away, and beyond the optical, the improvement of this type of tool is crucial. SSPs use as ingredients isochrones, an initial mass function, and a library of stellar spectra. My focus are the stellar libraries, key ingredient for SSPs. Here I talk about the latest developments of stellar libraries, how they influence the SSPs and how to improve them.

scholarly journals Evidence of spectral evolution on the white dwarf sample from the Gaia mission

2020 ◽  
Vol 492 (4) ◽  
pp. 5003-5010 ◽  
Author(s):  
G Ourique ◽  
S O Kepler ◽  
A D Romero ◽  
T S Klippel ◽  
D Koester
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Mass Function ◽  
Initial Mass Function ◽  
Star Formation History ◽  
Initial Mass ◽  
Spectral Evolution ◽  
Formation History ◽  
Magnitude Diagram ◽  
Double Population

ABSTRACT Since the Gaia data release 2, several works have been published describing a bifurcation in the observed white dwarf colour−magnitude diagram for ${G_{\mathrm{BP}}}{}-{G_{\mathrm{RP}}}{} \gt 0$. Some possible explanations in the literature include the existence of a double population with different initial mass functions or two distinct populations, one formed by hydrogen-envelope and one formed by helium-envelope white dwarfs. We propose instead spectral evolution to explain the bifurcation. From a population synthesis approach, we find that spectral evolution occurs for effective temperatures below ${\simeq }11\, 000\, \mathrm{K}$ and masses mainly between $0.64\, \mathrm{M}_\odot$ and $0.74\, \mathrm{M}_\odot$, which correspond to around 16 per cent of all DA white dwarfs. We also find that the Gaia white dwarf colour–magnitude diagram indicates a star formation history that decreases abruptly for objects younger than $1.4\, \mathrm{Gyr}$ and a top-heavy initial mass function for the white dwarf progenitors.

scholarly journals Impact of metallicity and star formation rate on the time-dependent, galaxy-wide stellar initial mass function

2018 ◽  
Vol 620 ◽  
pp. A39 ◽  
Author(s):  
T. Jeřábková ◽  
A. Hasani Zonoozi ◽  
P. Kroupa ◽  
G. Beccari ◽  
Z. Yan ◽  
...  
Keyword(s):  
Star Formation ◽  
Dwarf Galaxies ◽  
Mass Function ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Probability Density Distribution ◽  
Star Forming ◽  
The Galaxy ◽  
Stellar Initial Mass Function ◽  
Stellar Masses

The stellar initial mass function (IMF) is commonly assumed to be an invariant probability density distribution function of initial stellar masses. These initial stellar masses are generally represented by the canonical IMF, which is defined as the result of one star formation event in an embedded cluster. As a consequence, the galaxy-wide IMF (gwIMF) should also be invariant and of the same form as the canonical IMF; gwIMF is defined as the sum of the IMFs of all star-forming regions in which embedded clusters form and spawn the galactic field population of the galaxy. Recent observational and theoretical results challenge the hypothesis that the gwIMF is invariant. In order to study the possible reasons for this variation, it is useful to relate the observed IMF to the gwIMF. Starting with the IMF determined in resolved star clusters, we apply the IGIMF-theory to calculate a comprehensive grid of gwIMF models for metallicities, [Fe/H] ∈ (−3, 1), and galaxy-wide star formation rates (SFRs), SFR ∈ (10−5, 105) M⊙ yr−1. For a galaxy with metallicity [Fe/H] < 0 and SFR > 1 M⊙ yr−1, which is a common condition in the early Universe, we find that the gwIMF is both bottom light (relatively fewer low-mass stars) and top heavy (more massive stars), when compared to the canonical IMF. For a SFR < 1 M⊙ yr−1 the gwIMF becomes top light regardless of the metallicity. For metallicities [Fe/H] > 0 the gwIMF can become bottom heavy regardless of the SFR. The IGIMF models predict that massive elliptical galaxies should have formed with a gwIMF that is top heavy within the first few hundred Myr of the life of the galaxy and that it evolves into a bottom heavy gwIMF in the metal-enriched galactic centre. Using the gwIMF grids, we study the SFR−Hα relation and its dependency on metallicity and the SFR. We also study the correction factors to the Kennicutt SFRK − Hα relation and provide new fitting functions. Late-type dwarf galaxies show significantly higher SFRs with respect to Kennicutt SFRs, while star-forming massive galaxies have significantly lower SFRs than hitherto thought. This has implications for gas-consumption timescales and for the main sequence of galaxies. We explicitly discuss Leo P and ultra-faint dwarf galaxies.

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