THE INITIAL MASS FUNCTION AND YOUNG BROWN DWARF CANDIDATES IN NGC 2264. IV. THE INITIAL MASS FUNCTION AND STAR FORMATION HISTORY

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.

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

Symposium - International Astronomical Union ◽

10.1017/s0074180900118200 ◽

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.

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

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320001647 ◽

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.

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

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa120 ◽

2020 ◽

Vol 492 (4) ◽

pp. 5003-5010 ◽

Cited By ~ 1

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.

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

Proceedings of the International Astronomical Union ◽

10.1017/s174392131600870x ◽

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.

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Star formation history of the solar neighbourhood as told by Gaia

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3576 ◽

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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