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 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.

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.

Synergies between Massive Stars and Metal-poor Dwarf Irregular Galaxies

2018 ◽  
Vol 14 (S344) ◽  
pp. 178-181
Author(s):  
Miriam Garcia ◽  
Artemio Herrero ◽  
Francisco Najarro ◽  
Norberto Castro ◽  
Inés Camacho
Keyword(s):  
Massive Stars ◽  
Mass Function ◽  
Initial Mass Function ◽  
Star Formation History ◽  
Ob Stars ◽  
Irregular Galaxies ◽  
Formation History ◽  
Population Iii Stars ◽  
Dwarf Irregular Galaxies ◽  
Cosmic History

AbstractThe community of massive stars is working intensively on Local Group dwarf irregular galaxies (dIrr). They are a reservoir of metal-poor massive stars that serve to understand the physics of their higher redshift siblings and population III stars, interpret the farthest, most energetic SNe and GRBs, and compute feedback through Cosmic History. Along the way, we became interested in the recent star-formation history and initial mass-function of the host dIrr’s, their chemical evolution, and gas and dust content. Our team is working to unveil and characterize with spectroscopy the OB-stars in IC 1613, Sextans A and SagDIG, that form a sequence of decreasing metal content. We showcase some results to stimulate synergies between both communities.

scholarly journals Some processes influencing the stellar initial mass function

1991 ◽  
Vol 147 ◽  
pp. 261-273
Author(s):  
Richard B. Larson
Keyword(s):  
Mass Spectrum ◽  
Power Law ◽  
Massive Stars ◽  
Mass Function ◽  
Stellar Mass ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Current Evidence ◽  
Solar Mass ◽  
Stellar Initial Mass Function

Current evidence suggests that the stellar initial mass function has the same basic form everywhere, and that its fundamental features are (1) the existence of a characteristic stellar mass of order one solar mass, and (2) the existence of an apparently universal power-law form for the mass spectrum of the more massive stars. The characteristic stellar mass may be determined in part by the typical mass scale for the fragmentation of star forming clouds, which is predicted to be of the order of one solar mass. The power-law extension of the mass spectrum toward higher masses may result from the continuing accretional growth of some stars to much larger masses; the fact that the most massive stars appear to form preferentially in cluster cores suggests that such continuing accretion may be particularly important at the centers of clusters. Numerical simulations suggest that forming systems of stars may tend to develop a hierarchical structure, possibly self-similar in nature. If most stars form in such hierarchically structured systems, and if the mass of the most massive star that forms in each subcluster increases as a power of the mass of the subcluster, then a mass spectrum of power-law form is predicted. Some possible physical effects that could lead to such a relation are briefly discussed, and some observational tests of the ideas discussed here are proposed.

scholarly journals Dissecting 30 Doradus: Optical and Near Infrared Star Formation History of the starburst cluster NGC2070 from the Hubble Tarantula Treasury Project

2015 ◽  
Vol 12 (S316) ◽  
pp. 77-83
Author(s):  
Michele Cignoni ◽  
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
Near Infrared ◽  
Mass Function ◽  
Large Magellanic Cloud ◽  
Initial Mass Function ◽  
Star Formation History ◽  
Formation History ◽  
History Of ◽  
30 Doradus

AbstractI will present new results on the star formation history of 30 Doradus in the Large Magellanic Cloud based on the panchromatic imaging survey Hubble Tarantula Treasury Project (HTTP). Here the focus is on the starburst cluster NGC2070. The star formation history is derived by comparing the deepest ever optical and NIR color-magnitude diagrams (CMDs) with state-of-the-art synthetic CMDs generated with the latest PARSEC models, which include all stellar phases from pre-main sequence to post-main sequence. For the first time in this region we are able to measure the star formation using intermediate and low mass stars simultaneously. Our results suggest that NGC2070 experienced a prolonged activity. I will discuss the detailed star formation history, initial mass function and reddening distribution.

scholarly journals On the Star-formation History in the LMC: Observations of the Interstellar C18O/C17O Ratio

1999 ◽  
Vol 190 ◽  
pp. 275-276
Author(s):  
Arto Heikkilä ◽  
Lars E.B. Johansson ◽  
Hans Olofsson
Keyword(s):  
Star Formation ◽  
Massive Stars ◽  
Density Ratio ◽  
Abundance Ratio ◽  
Initial Mass Function ◽  
Star Formation History ◽  
Intermediate Mass ◽  
Stellar Nucleosynthesis ◽  
Intermediate Mass Stars ◽  
Formation History

The re-cycling of gas between stars and the interstellar medium (ISM) leads to a gradual metal-enrichment of a galaxy. Accordingly, information on the chemical evolution of a galaxy, e.g., its star-formation history (SFH), is contained in the chemical composition of the ISM. In this context, the abundance ratio of the rare oxygen isotopes, 18O/17O (usually taken as the C18O/C17O column density ratio), appears to be a particularly promising probe of the SFH. According to present understanding of stellar nucleosynthesis, 17O is mainly produced in intermediate-mass stars (say a few to ten M⊙) while 18O is synthesised in massive stars (say >10M⊙) (e.g., Prantzos et al. 1996). Thus, the 18O/17O abundance ratio possibly reflects the relative number of massive stars compared to intermediate-mass stars, and thereby (qualitatively) constrains the SFH in terms of the average star-formation rate (SFR) and the initial mass-function (IMF). However, it should be remembered that the stellar nucleosynthesis of 17,18O is not yet fully understood, leaving room for other interpretations of the 18O/17O ratio.

scholarly journals Star formation history of the solar neighbourhood as told by Gaia

2020 ◽  
Vol 501 (1) ◽  
pp. 302-328
Author(s):  
Jairo A Alzate ◽  
Gustavo Bruzual ◽  
Daniel J Díaz-González
Keyword(s):  
Star Formation ◽  
Binary Stars ◽  
Mass Function ◽  
Initial Mass Function ◽  
Star Formation History ◽  
Solar Neighbourhood ◽  
Data Set ◽  
Formation History ◽  
Solar Metallicity ◽  
History Of

ABSTRACT The Gaia data release 2 (DR2) catalogue is the best source of stellar astrometric and photometric data available today. The history of the Milky Way galaxy is written in stone in this data set. Parallaxes and photometry tell us where the stars are today, when were they formed, and with what chemical content, that is, their star formation history (SFH). We develop a Bayesian hierarchical model suited to reconstruct the SFH of a resolved stellar population. We study the stars brighter than $G\, =\, 15$ within 100 pc of the Sun in Gaia DR2 and derive an SFH of the solar neighbourhood in agreement with previous determinations and improving upon them because we detect chemical enrichment. Our results show a maximum of star formation activity about 10 Gyr ago, producing large numbers of stars with slightly below solar metallicity (Z  =  0.014), followed by a decrease in star formation up to a minimum level occurring around 8 Gyr ago. After a quiet period, star formation rises to a maximum at about 5 Gyr ago, forming stars of solar metallicity (Z  =  0.017). Finally, star formation has been decreasing until the present, forming stars of Z  =  0.03 at a residual level. We test the effects introduced in the inferred SFH by ignoring the presence of unresolved binary stars in the sample, reducing the apparent limiting magnitude, and modifying the stellar initial mass function.

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