Relevant bibliographies by topics / Stellar initial mass function

Academic literature on the topic 'Stellar initial mass function'

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Published: 10 December 2022
Last updated: 29 January 2023

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Journal articles on the topic "Stellar initial mass function"

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Hopkins, Andrew. "Measuring the stellar initial mass function." Proceedings of the International Astronomical Union 15, S352 (June 2019): 98. http://dx.doi.org/10.1017/s1743921320001155.

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AbstractThe birth of stars and the formation of galaxies are cornerstones of modern astrophysics. While much is known about how galaxies globally and their stars individually form and evolve, one fundamental property that affects both remains elusive. This is problematic because this key property, the stellar initial mass function (IMF), is a key tracer of the physics of star formation that underpins almost all of the unknowns in galaxy and stellar evolution. It is perhaps the greatest source of systematic uncertainty in star and galaxy evolution. The past decade has seen a growing number and variety of methods for measuring or inferring the shape of the IMF, along with progressively more detailed simulations, paralleled by refinements in the way the concept of the IMF is applied or conceptualised on different physical scales. This range of approaches and evolving definitions of the quantity being measured has in turn led to conflicting conclusions regarding whether or not the IMF is universal. Here I summarise the growing wealth of approaches to our understanding of this fundamental property that defines so much of astrophysics, and highlight the importance of considering potential IMF variations, reinforcing the need for measurements to quantify their scope and uncertainties carefully. I present a new framework to aid the discussion of the IMF and promote clarity in the further development of this fundamental field.
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Larson, R. B. "Towards understanding the stellar initial mass function." Monthly Notices of the Royal Astronomical Society 256, no. 4 (June 15, 1992): 641–46. http://dx.doi.org/10.1093/mnras/256.4.641.

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Ferreras, Ignacio, Francesco La Barbera, and Alexandre Vazdekis. "Is the stellar initial mass function universal?" Astronomy & Geophysics 57, no. 2 (March 30, 2016): 2.32–2.36. http://dx.doi.org/10.1093/astrogeo/atw074.

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Chabrier, Gilles. "Galactic Stellar and Substellar Initial Mass Function." Publications of the Astronomical Society of the Pacific 115, no. 809 (July 2003): 763–95. http://dx.doi.org/10.1086/376392.

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Maschberger, T. "On the function describing the stellar initial mass function." Monthly Notices of the Royal Astronomical Society 429, no. 2 (December 20, 2012): 1725–33. http://dx.doi.org/10.1093/mnras/sts479.

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Schaerer, Daniel. "The massive star Initial Mass function." Symposium - International Astronomical Union 212 (2003): 642–51. http://dx.doi.org/10.1017/s007418090021303x.

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We review our current knowledge on the IMF in nearby environments, massive star forming regions, super star clusters, starbursts and alike objects from studies of integrated light, and discuss the various techniques used to constrain the IMF. In most cases, including UV-optical studies of stellar features and optical-IR analysis of nebular emission, the data is found to be compatible with a ‘universal’ Salpeter-like IMF with a high upper mass cut-off over a large metallicity range. In contrast, near-IR observations of nuclear starbursts and LIRG show indications of a lowerMupand/or a steeper IMF slope, for which no alternate explanation has yet been found. Also, dynamical mass measurements of seven super star clusters provide so far no simple picture of the IMF. Finally, we present recent results of a direct stellar probe of the upper end of the IMF in metal-rich H ii regions, showing no deficiency of massive stars at high metallicity, and determining a lower limit ofMup≳ 60 – 90 M⊙.
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Padoan, P., A. Nordlund, and B. J. T. Jones. "The universality of the stellar initial mass function." Monthly Notices of the Royal Astronomical Society 288, no. 1 (June 11, 1997): 145–52. http://dx.doi.org/10.1093/mnras/288.1.145.

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Nakamura, Fumitaka, and Masayuki Umemura. "The Stellar Initial Mass Function in Primordial Galaxies." Astrophysical Journal 569, no. 2 (April 20, 2002): 549–57. http://dx.doi.org/10.1086/339392.

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Larson, Richard B. "Some processes influencing the stellar initial mass function." Symposium - International Astronomical Union 147 (1991): 261–73. http://dx.doi.org/10.1017/s0074180900239600.

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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.
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Leitherer, Claus. "The Stellar Initial Mass Function in Starburst Galaxies." Symposium - International Astronomical Union 186 (1999): 243–50. http://dx.doi.org/10.1017/s0074180900112707.

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Starburst galaxies are currently forming massive stars at prodigious rates. I discuss the star-formation histories and the shape of the initial mass function, with particular emphasis on the high- and on the low-mass end. The classical Salpeter IMF is consistent with constraints from observations of the most massive stars, irrespective of environmental properties. The situation at the low-mass end is less clear: direct star counts in nearby giant H II regions show stars down to ~1 M⊙, whereas dynamical arguments in some starburst galaxies suggest a deficit of such stars.
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Dissertations / Theses on the topic "Stellar initial mass function"

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Nelson, Katy. "On the origin of the stellar initial mass function and multiple stellar systems." Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/65971/.

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I first perform a statistical analysis on a distribution of pre-stellar core masses. Each core is split into a small number of stars, and two stars are chosen using a prescription based on stellar masses to form a binary system. The rest of the stars are taken to be singles. From this sample of binaries and singles, I compute the stellar initial mass function, the binary frequency and mass ratio distribution as a function of primary mass. I then test if the observed binary frequencies and mass ratios are compatible with this self-similar mapping of cores into stars. I show that self-similar mapping can reproduce the observed binary frequencies and mass ratios well, so long as the efficiency is rather high (100%), and each core fragments into about 4 or 5 stars. Using the code Seren view, I then perform N-body simulations with core-clusters. I investigate the formation of multiple systems, and qualify the dependence of their parameters and longevity on certain initial conditions, including (i) the number of stars in a core-cluster, (ii) the variance of masses in those stars, (iii) the virial ratio and (iv) radial dependence of stellar density. I expand on those results by including (a) a prescription for the influence of disks during stellar ybys, (b) different initial spatial configurations of the stars (i.e. line and ring clusters) and (c) a background potential due to residual gas in the core-cluster. The full range of periods observed in the field cannot be explained by the distribution of periods of pure binaries alone, which is too narrow. However, the wide range can be explained either by combining the periods of pair-wise orbits of all multiple systems, i.e. the widest periods observed are in fact pair-wise orbits of higher-order multiples with unresolved companions, or by considering a distribution of pre-stellar cores that have a range of virial ratios.
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Catalán, Ruiz Sílvia. "Testing the initial-final mass relationship of white dwarfs." Doctoral thesis, Universitat Politècnica de Catalunya, 2008. http://hdl.handle.net/10803/6591.

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White dwarfs are the final remnants of low- and intermediate-mass stars. About 95% of main- sequence stars will end their evolutionary pathways as white dwarfs and, hence, the study of the white dwarf population provides details about the late stages of the life of the vast majority of stars.
Since white dwarfs are long-lived objects, they also constitute useful objects to study the structure and evolution of our Galaxy. For instance, the initial-final mass relationship, which connects the final mass of a white dwarf with the initial mass of its main-sequence progenitor, is of paramount importance for different aspects in modern astrophysics. This function is used for determining the ages of globular clusters and their distances, for studying the chemical evolution of galaxies, and also to understand the properties of the Galactic population of white dwarfs. Despite its relevance, this relationship is still relatively poorly constrained.
The main aim of this thesis is the study of the initial-final mass relationship. For such purpose we have used two different approaches. From an observational perspective, the statistical significance of the current initial final mass relationship can be improved by performing spectroscopic observations of white dwarfs for which some important parameters are available. Since this approach involves the use of theoretical stellar evolutionary tracks the resulting initial-final mass relationship is, in fact, semi-empirical. In this thesis we present a promising method which consists in using common proper motion pairs comprised of a white dwarf and a FGK star. It is sound to assume that the members of the system were born simultaneously and with the same chemical composition. Moreover, these stars are well separated and it can be considered that they have evolved as isolated stars, since mass exchange between them is unlikely. Thus, a careful analysis of the observational data of both members of each pair allows us to derive the initial and final masses of the white dwarf components, something which is totally impossible when white dwarfs are isolated. Considering the new data that we have obtained with this work and the observational data currently used to define the initial-final mass relationship we have carried out a revision of this relationship, giving some clues on its dependence on different parameters, especially on metallicity.
The second approach to improve the initial-final mass relationship involves an indirect measurement, which has been carried out by studying its influence on one of the powerful tools related to the white dwarf population, the white dwarf luminosity function. We have computed a series of luminosity functions using different theoretical initial-final mass relationships, and also, considering the semi-empirical relation derived in this thesis. We have compared these computations with the available observational data in order to evaluate the validity of each of these relations.
In order to increase the statistical significance of the white dwarf luminosity function and to improve the initial-final mass relationship it is necessary to extend the amount of accurate and reliable observational data. For this reason part of the thesis is devoted to the Alhambra Survey, which is a good example of the new deep surveys currently under development. These observational projects will detect thousands of new white dwarfs, some of them belonging to common proper motion pairs, which could be eventually used to extend our analysis. Thus, we have performed an exhaustive study to optimize the identification procedure of the white dwarf candidates which will be eventually detected by the Alhambra survey.
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Lee, Yueh-Ning. "Formation and fragmentation of stellar proto-clusters." Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCC152/document.

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Les étoiles sont des éléments fondamentaux de l'Univers. Elles émettent de l'énergie en forme de lumières et rendent les matériaux dans le ciel visible. Les étoiles se regroupent pour former les galaxies, en déterminant l'évolution et la dynamique de ce dernier. En même temps, l'étoile est le centre d'un système planétaire. Le disque de débris autour d'une jeune étoile se refroidi et forme un système de planète. Les caractéristiques de ce système, notamment la masse de l'étoile centrale, jouent un rôle important en ce qui concerne l'apparition de la vie. Cette thèse a pour objectif de comprendre comment la massed'une étoile est assemblée et déterminée, donnant une distribution de masse apparemmentuniverselle quel que soit l'environnement de leur formation..La thèse est constituée de deux chapitres introductifs sur la physique de formation stellaire et sur les méthodes numériques. Les trois chapitres suivants sont constitués des projets menés durant la thèse: la formation des proto-amas, l'effet de condition initiale dans le nuage moléculaire, et la formation des coeurs préstellaires par la fragmentation des filaments, suivis par les articles publiés dans les journaux scientifiques. Le dernier chapitre conclu la thèse et donne les perspectifs pour la future recherche
Stars are building blocks of the Universe. They emit energy in form of light and make the material in the night sky visible. They are the elementary constituents of galaxies, determining their evolution and dynamics. On the other hand, stars are the hosts o planetary systems. The debris disc around a new-born star eventually cools down and form planets. The characteristic of the planetary system, essentially the mass of the central star, plays a major role in the formation of living being on planets. The formation of stars often occur in a clusters manner, and one of the important issues constantly under debate is the distribution of the mass of newly-born stars. This thesis is aimed to understand the Initial Mass Function which seems to be universal among different environments.This manuscripts comprises two introductory chapters on the physics of star formation and the numerical methods, respectively. Three following chapters present the projets carried out during the thesis: formation of proto-clusters, effects of initial condition in the molecular cloud, and the formation of prestellar cores from filament fragmentation, all followed by published journal articles. The last chapter concludes the manuscript and discuss the perspectives
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Canameras, R., N. P. H. Nesvadba, R. Kneissl, M. Limousin, R. Gavazzi, D. Scott, H. Dole, et al. "Planck's dusty GEMS III. A massive lensing galaxy with a bottom-heavy stellar initial mass function at z=1.5." EDP SCIENCES S A, 2017. http://hdl.handle.net/10150/624365.

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We study the properties of the foreground galaxy of the Ruby, the brightest gravitationally lensed high-redshift galaxy on the sub-millimeter sky as probed by the Planck satellite, and part of our sample of Planck's dusty GEMS. The Ruby consists of an Einstein ring of 1.4" diameter at z = 3.005 observed with ALMA at 0.1" resolution, centered on a faint, red, massive lensing galaxy seen with HST/WFC3, which itself has an exceptionally high redshift, z = 1.525 +/- 0.001, as confirmed with VLT/X-shooter spectroscopy. Here we focus on the properties of the lens and the lensing model obtained with LENSTOOL. The rest-frame optical morphology of this system is strongly dominated by the lens, while the Ruby itself is highly obscured, and contributes less than 10% to the photometry out to the K band. The foreground galaxy has a lensing mass of (3.70 +/- 0.35) x 10(11) M-Theta Magnification factors are between 7 and 38 for individual clumps forming two image families along the Einstein ring. We present a decomposition of the foreground and background sources in the WFC3 images, and stellar population synthesis modeling with a range of star-formation histories for Chabrier and Salpeter initial mass functions (IMFs). Only the stellar mass range obtained with the latter agrees well with the lensing mass. This is consistent with the bottom-heavy IMFs of massive high-redshift galaxies expected from detailed studies of the stellar masses and mass profiles of their low-redshift descendants, and from models of turbulent gas fragmentation. This may be the first direct constraint on the IMF in a lens at z = 1.5, which is not a cluster central galaxy.
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Orsi, Maia. "Population synthesis models for IMF studies." Thesis, Liverpool John Moores University, 2014. http://researchonline.ljmu.ac.uk/4525/.

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Population synthesis models (PSMs) are fundamental tools to study the star formation history and IMF of unresolved stellar populations using spectral features. This work presents a new set of PSMs constructed using theoretical isochrones and two state-ofthe- art synthetic spectral libraries. The BT-Settl and Munari libraries were chosen for their ability to predict the observed values of Lick-type and IMF-sensitive indices in individual stars of the solar neighbourhood. The BT-Settl library was used to sample the cool main sequence stars and the Munari library for the rest of the evolutionary phases. The PSMs cover a range of metallicities with [Fe/H]= 0, -1.31 and -1.81 for scaled-solar and α-enhanced metal mixtures. The models were used to study the behaviour of the IMF indices defined in the literature and the results are in good agreement with what other PSMs have determined. The PSMs in this work predict a strong degeneracy between age, metallicity and IMF. I used the models to study which are the main evolutionary phases contributing to each IMF-sensitive index and found that most indices reach their final integrated values before the turn off. The post-main sequence stars contribute mainly to the continuum of these bands. Uncertainties in the the effective temperature of the isochrones can affect IMF estimates. The PSMs were applied to extragalactic globular clusters (GCs) and early-type galaxies (ETGs) using data from the literature. I determined the ages, metallicities and IMFs of these systems using index combinations in the optical and infrared. I explored how the morphology of the Horizontal Branch (HB) and dynamical evolution (which are key uncertainties in the modelling of GCs) can affect the IMF predictions. In a population with a Milky Way IMF, dynamical evolution can make the IMF indices mimic a bottom-light IMF. HB morphology has no impact on the IMF estimates at low [Fe/H]. In the IMF index-index diagrams for GCs, the results are significantly affected by the unknown sodium abundances of these systems. Using the PSMs in this work the best index combination to determine the IMF is CaH1 and TiO2. The ETGs and the [Fe/H]=0 GCs appear to have a bottom-heavy IMF with x ~ 3:0. These results are discussed in the work.
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Mor, Crespo Roger. "The star formation history and the stellar initial mass function of the Milky Way disc. The population synthesis Besançon Galaxy Model in the Gaia era." Doctoral thesis, Universitat de Barcelona, 2019. http://hdl.handle.net/10803/667482.

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AIMS: We develop a new theoretical framework to generate Besançon Galaxy Model Fast Approximate Simulations (BGM FASt) to address fundamental questions of the Galactic structure and evolution performing multi-parameter inference. The flexibility of BGM FASt allows the inference of fundamental parameters related to the stellar initial mass function (IMF), the star formation history (SFH), the density distribution, the kinematics and the chemo-dynamics, among others. BGM FASt allows the study of different Milky Way (MW) components. In this thesis we are focused in a first application of our strategy to simultaneously infer the IMF and the SFH of the MW disc. METHOD: BGM FASt is based on a reweighing scheme, that uses a specific pre-sampled simulation. We use BGM FASt together with an approximate Bayesian computation algorithm to obtain the posterior probability distribution function of the inferred parameters, by automatically comparing synthetic versus observed data. Our full strategy is codified to run on Apache Spark and Hadoop, suited to deal with large surveys. BGM FASt is implemented in the big data infrastructure known as Gaia Data Analytics Framework (GDAF) at the University of Barcelona. To evaluate the performance of BGM FASt we execute a set of validation tests comparing density, colour, mass and age distributions of BGM FASt versus BGM standard simulations. We present two scientific cases that compare synthetic versus Tycho-2 colour-magnitude diagrams. We obtain for the first time using BGM an IMF and SFH of the thin disc by exploring a 6-Dimensional parameter space. We use Gaia data-release 2 magnitudes, colours, and parallaxes for stars with G<12 to explore a parameter space with 15 dimensions. This includes simultaneously the IMF and, for the first time, a non-parametric SFH for the Galactic disc. RESULTS: The set of tests applied show a very good agreement between equivalent simulations performed with BGM FASt and standard BGM. It has resulted to be 10000 times faster. We demonstrate it is a very valuable tool to perform multi-parameter inference using large catalogues. The two scientific demonstration cases of our strategy applied to Tyhco-2 data gives us, for the first time using BGM, a full 6D posterior probability distribution function of the parameters involved in the IMF and the SFH of the thin disc component. Using Gaia DR2 we find an imprint of a star formation burst 2-3 Gyr ago in the Galactic thin disc domain. Our results show a decreasing trend followed by a Star Formation Rate (SFR) enhancement starting at about 5 Gyr ago and continuing until about 1 Gyr ago. This enhancement is detected with high statistical significance by discarding the null hypothesis of an exponential SFH. The timescale and the amount of stellar mass generated during this SFR enhancement event lead us to hypothesise that its origin, currently under investigation, is not intrinsic to the disc. When we adopt a non-parametric SFH the resulting IMF for the thin disc has an alpha3 of approximately 2 for masses M larger than 1.53 Msun and alpha2 approximately 1.3 for the mass range between 0.5 and 1.53Msun. CONCLUSIONS: BGM FASt has allowed us to increase our knowledge about the IMF and the SFH of the MW disc. Our results have shown that the evolution of the SFR with time is much more complex than a simple mathematical exponential decreasing shape. We have seen how the imposition of a mathematical shape for the SFH has a clear impact into the derivation of the IMF at high masses. The good performance of our whole strategy opens very promising perspectives, among them, the possibility to study whether the IMF variates with the time or not.
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Prichard, Laura Jane. "The evolution of early-type galaxies." Thesis, University of Oxford, 2018. http://ora.ox.ac.uk/objects/uuid:35fbf5c7-76de-4179-8e68-032ba8b5f3ee.

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Early-type galaxies (ETGs) are typically thought of as 'red and dead' with little to no star formation and old stellar populations. Their detailed kinematics measured locally suggest an interesting array of formation mechanisms and high-redshift observations are starting to reveal a two-phase evolutionary path for the most massive galaxies. In this thesis, I take a combined approach to studying the formation of ETGs. I look to distant quiescent galaxies in one of the densest regions of the early Universe and at the fossil record of a local galaxy to shed light on some of the unsolved mysteries of how ETGs evolved. Using the unique multiplexed instrument, the K-band Multi-Object Spectrograph (KMOS), the evolution of galaxies at both low and high redshift were studied as part of this thesis. I maximised the capabilities of this multi-integral field unit (IFU) near-infrared (NIR) instrument to study different aspects of ETG evolution. With 24 separate IFUs, many quiescent galaxies were efficiently observed in a massive high-redshift cluster as part of the KMOS Cluster Survey. Coupling KMOS spectroscopy with Hubble Space Telescope photometry, I studied the ages, kinematics, and structural properties of the galaxies. I then analysed the detailed properties of a massive local ETG with interesting kinematics, IC 1459. Coupling the NIR IFU data from KMOS with a large mosaic of optical data from the Multi-Unit Spectroscopic Explorer, I was able to study the spatially resolved kinematics, stellar populations, and initial mass function of the galaxy. The work presented in this thesis provides some interesting clues as to the formation of ETGs and possible diversity of their evolutionary paths.
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Burgess, Andrew. "Exploration de la fonction de faible masse initiale dans les amas jeunes et les r ´egions de formation stellaire." Phd thesis, Université de Grenoble, 2010. http://tel.archives-ouvertes.fr/tel-00576460.

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La détermination de l'extrémité inférieure de la fonction de masse initiale (FMI) prévoit de fortes contraintes sur les théories de la formation des étoiles. IC4665 est un amas d'´étoile jeune (30Myr) et il a situe 356pc de la Terre. L'extinction est Av~ 0.59 ± 0.15 mag. WIRCam Y, J, H et K observations ont été faites par le CFHT et a comprise 10 champs (de 1.1sq.deg totale) et deux zones de contrle de 20'x20' chacun. Diagrammes couleur/magnitude et couleur/couleur ont été utilisées pour comparer les candidats sélectionnées par les modèles BT-SETTL 30 et 50Myr. Les images CH4off et CH4on ont été obtenus avec CFHT/WIRCam plus 0.11 sq.deg. dans IC348. Naines-T ont ensuite été identifiés à partir de leur couleur de 1.69μm d'absorption du méthane et trois candidats nain-T ont été trouvée avec CH4on−CH4 >0.4 mag. Extinction a été estimée à Av~ 5 − 12 mag. Les comparaisons avec les naines-T modèles, et des diagrammes couleur/couleur et magnitude, rejeter 2 entre 3 candidats en raison de leur extrême z′ − J coleur. L'objet reste n'est pas considéré comme un nain avant l'amas en raison d'un argument de densité en nombre ou l'extinction forte Av~ 12 mag, ni d'être un champ de fond nain-T qui serait devrait être beaucoup plus faible. Les modèles et les schémas de donner cet objet un type T6 préliminaires spectrale. Avec un peu de la masse de Jupiter, ce jeune candidat nain-T est potentiellement parmi les plus jeunes, des objets de masse plus faible détectée dans une région de formation d'´étoiles `a ce jour. Sa fréquence est conforme à l'extrapolation du courant lognormal FMI estime `a au domaine de masse planétaire.
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Williams, R. P. "Low surface brightness galaxies and the galaxy stellar mass function." Thesis, Liverpool John Moores University, 2017. http://researchonline.ljmu.ac.uk/6652/.

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The galaxy stellar mass function (GSMF) has been well measured by the Galaxy And Mass Assembly (GAMA) survey down to a mass of $\mstar = 10^{8}\,\msun$. Below this mass the values produced so far can only be taken as lower limits on the distribution. One source of this incompleteness is failing to account for undetected low-surface-brightness galaxies (LSBGs) within the fields observed. These galaxies have been known about for some time, however, taking a true census of their population is difficult because of the biases associated with their detection in large surveys. The focus of this thesis is to improve the census of these objects and to try and apply those results to the low-mass end of the GSMF. First the SDSS data used to create the original GAMA catalogues is re-examined for low-surface brightness galaxies (LSBGs). To accomplish this SDSS DR7 imaging was used and a specialised detection algorithm created. This was based on masking sources detected with SDSS \textsc{photo}, combining the {\it gri} images with a weighting that maximises the signal-to-noise (SNR), and smoothing the images. These were then run through a detection algorithm which finds all pixels above a set threshold and groups them based on their proximity to one another. The list of detections is cleaned of contaminants such as diffraction spikes and the faint wings of masked objects. This produces a final list of 343 newly discovered LSBGs. Measuring their $g-i$ and $J-K$ colours shows that most are likely to be at redshifts less than 0.15. The photometry is carried out using a flexible auto aperture for each detection giving surface brightness measurements of $\mu_{r} > 23.7$\,mag arcsec$^{-2}$ and $r$-band magnitudes of $r_{AUTO} \gtrsim 20$\, mag. Through this method we show there are at least 343 new LSBGs within the GAMA fields, however none of these galaxies are bright enough to be within the GAMA main survey limit. It was noticed during the previous work that the detected LSBGs were all visible in VIKING $Z$-band data, and so it was decided to run a more traditional detection algorithm over these data to increase the number of LSBGs detected. This could then be used to create a new GSMF based on the deeper $Z$-band imaging. By using this imaging it will be possible to detect many more faint galaxies than previously and also increase the depth to which surface brightness can be effectively probed. The three GAMA equatorial regions have had mosaics created from the $Z$-band imaging which are searched using \textsc{Source Extractor} (\textsc{SExtractor}) and catalogues of detections are made. These are then compared to the original GAMA catalogues to remove duplicate detections and identify any possible new ones. Criteria are then applied to the source lists to remove any stars or objects which are either not galaxies or artefacts. This then leaves only likely galaxies in the catalogue to be used. The next stage is to create the GSMF based on the data collected, through applying corrections for the volume searched, and the spectroscopic completeness of the objects after they have been binned in $g-i$, $J-K$, and apparent magnitude. The GSMF created is compared to previous versions, namely that from \cite{Baldry+2012}, and a rise in the number density at masses of $\mstar \le 10^{8}\,\msun$ is shown. These can still only be thought of as lower limits however as improvement to the imaging can still be made in future surveys. With a full catalogue obtained using the VIKING Z-band it was decided to revisit the detection algorithm developed in Chapter 2. A pilot study was undertaken to both test the validity of the method, and the suitability of the VIKING images for further study. Whilst applying the detection algorithm to the data improved the ability to detect low surface brightness features within the images, no new galaxies were discovered over the pilot study area of $0.75$ deg$^{2}$. This method applied to the Z-band data, even over the full area, is unlikely to lead to large numbers of new LSBGs. This work has shown that there are still LSBGs in the field to be discovered. The result of finding new LSBGs has been to raise the measurement of the GSMF at low masses, further constraining the number of low mass galaxies in the Universe.
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Luhman, Kevin Lee 1971. "Low-mass star formation and the initial mass function in young clusters." Diss., The University of Arizona, 1998. http://hdl.handle.net/10150/288884.

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I have used optical and near-infrared spectroscopy and imaging to measure spectral types and luminosities for young (τ < 10 Myr), embedded (Aᵥ = 0-50), low-mass (0.1-1 M(⊙)) stars in three nearby (d < 300 pc) clusters: L1495E, IC 348, and ρ Ophiuchi. In conjunction with theoretical evolutionary tracks, I have derived the star formation history and initial mass function for each stellar population. A large number of brown dwarf candidates have been identified in the photometry, several of which are confirmed through spectroscopy. Finally, I have measured the frequency and survival times of circumstellar disks and investigated the photometric and spectroscopic properties of protostars. In § 2, I apply observational tests to the available sets of evolutionary models for low-mass stars, concluding that the calculations of D'Antona & Mazzitelli are preferred for the range of masses and ages considered here. In § 3 and § 4, I examine in detail the spectroscopic characteristics and substellar nature of two brown dwarf candidates. The study then expands to include the populations within the clusters L1495E (§ 5), IC 348 (§ 6), and ρ Ophiuchi (§ 7). In § 8, I briefly discuss the past, present, and future of scientific research related to this thesis.
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Books on the topic "Stellar initial mass function"

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Herstmonceux Conference (38th 1998 Cambridge, England). The stellar initial mass function: 38th Herstmonceux Conference : proceedings of the meeting held at Institute of Astronomy and Royal Greenwich Observatory, Cambridge, UK, 14-18 July, 1998. San Francisco, Calif: Astronomical Society of the Pacific, 1998.

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Corbelli, Edvige, Francesco Palla, and Hans Zinnecker, eds. The Initial Mass Function 50 Years Later. Dordrecht: Springer Netherlands, 2005. http://dx.doi.org/10.1007/978-1-4020-3407-7.

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Hill, Robert James. The initial mass function for massive stars in the Magellanic Clouds. Toronto: Dept. of Astronomy, University of Toronto, 1991.

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Marie, Treyer, Wyder Ted K, Neill James D, Seibert Mark, Lee Janice C, and Astronomical Society of the Pacific, eds. UP2010: Have observations revealed a variable upper end of the initial mass function? : proceedings of a conference held at Sedona, Arizona, USA, 20-25 June 2010. San Francisco, Calif: Astronomical Society of the Pacific, 2011.

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Scalo, John M. The stellar initial mass function. Gordon and Breach Science Publishers, 1986.

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Gilmore, Gerry. The Stellar Initial Mass Function: 38th Herstmonceux Conference: Proceedings of the Meeting Held at Institute of Astronomy and Royal Greenwich Observa ... Society of the Pacific Conference Series). Astronomical Society of the Pacific, 1998.

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Palla, Francesco, Hans Zinnecker, and Edvige Corbelli. Initial Mass Function 50 Years Later. Springer, 2005.

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Palla, Francesco, Hans Zinnecker, and Edvige Corbelli. The Initial Mass Function 50 Years Later. Springer, 2014.

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Hill, Robert. The initial mass function for massive stars in the magellanic clouds. 1991.

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(Editor), Edvige Corbelli, Francesco Palla (Editor), and Hans Zinnecker (Editor), eds. The Initial Mass Function 50 Years Later (Astrophysics and Space Science Library). Springer, 2005.

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Book chapters on the topic "Stellar initial mass function"

1

Klessen, Ralf S., and Simon C. O. Glover. "Models of the Stellar Initial Mass Function." In Lessons from the Local Group, 137–46. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-10614-4_11.

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Martín, Eduardo L. "Does the “STELLAR” IMF Extend to Planetary Masses?" In The Initial Mass Function 50 Years Later, 137–40. Dordrecht: Springer Netherlands, 2005. http://dx.doi.org/10.1007/978-1-4020-3407-7_23.

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Leitherer, Claus. "The Stellar Initial Mass Function in Starburst Galaxies." In Galaxy Interactions at Low and High Redshift, 243–50. Dordrecht: Springer Netherlands, 1999. http://dx.doi.org/10.1007/978-94-011-4665-4_58.

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Larson, Richard B. "Some Processes Influencing the Stellar Initial Mass Function." In Fragmentation of Molecular Clouds and Star Formation, 261–73. Dordrecht: Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-011-3384-5_29.

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Klessen, Ralf, Katharina Jappsen, Richard Larson, Yuexing Li, and Mordecai-Mark Mac Low. "The Stellar Mass Spectrum from Non-Isothermal Gravoturbulent Fragmentation." In The Initial Mass Function 50 Years Later, 363–70. Dordrecht: Springer Netherlands, 2005. http://dx.doi.org/10.1007/978-1-4020-3407-7_69.

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Weidner, Carsten, and Pavel Kroupa. "Evidence for a Fundamental Stellar Upper Mass Limit from Clustered Star Formation." In The Initial Mass Function 50 Years Later, 191–92. Dordrecht: Springer Netherlands, 2005. http://dx.doi.org/10.1007/978-1-4020-3407-7_36.

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Kroupa, Pavel, Carsten Weidner, Jan Pflamm-Altenburg, Ingo Thies, Jörg Dabringhausen, Michael Marks, and Thomas Maschberger. "The Stellar and Sub-Stellar Initial Mass Function of Simple and Composite Populations." In Planets, Stars and Stellar Systems, 115–242. Dordrecht: Springer Netherlands, 2013. http://dx.doi.org/10.1007/978-94-007-5612-0_4.

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Recchi, Simone, Francesco Calura, and Pavel Kroupa. "The [α/Fe] Ratios in Dwarf Galaxies: Evidence for a Non-universal Stellar Initial Mass Function?" In Astrophysics and Space Science Proceedings, 151–54. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-22018-0_16.

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Carigi, Leticia. "Initial Mass Function." In Encyclopedia of Astrobiology, 1–2. Berlin, Heidelberg: Springer Berlin Heidelberg, 2014. http://dx.doi.org/10.1007/978-3-642-27833-4_790-6.

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Carigi, Leticia. "Initial Mass Function." In Encyclopedia of Astrobiology, 1197–98. Berlin, Heidelberg: Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-662-44185-5_790.

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Conference papers on the topic "Stellar initial mass function"

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Moore, Toby J. T., Giuliana Giobbi, Amedeo Tornambe, Gabriella Raimondo, Marco Limongi, L. A. Antonelli, Nicola Menci, and Enzo Brocato. "Origins of the Stellar Initial Mass Function." In PROBING STELLAR POPULATIONS OUT TO THE DISTANT UNIVERSE: CEFALU 2008, Proceedings of the International Conference. AIP, 2009. http://dx.doi.org/10.1063/1.3141529.

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Dobbie, Paul D., Richard Baxter, Klaus Werner, and T. Rauch. "New white dwarfs for the stellar initial mass-final mass relation." In 17TH EUROPEAN WHITE DWARF WORKSHOP. AIP, 2010. http://dx.doi.org/10.1063/1.3527831.

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FERRARA, A. "FIRST STARS AND THEIR INITIAL MASS FUNCTION." In Proceedings of the XXI Symposium on Relativistic Astrophysics. WORLD SCIENTIFIC, 2003. http://dx.doi.org/10.1142/9789812704009_0005.

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Richer, Harvey B., and Gregory G. Fahlman. "The initial mass function: Now and then." In The seventh astrophysical conference: Star formation, near and far. AIP, 1997. http://dx.doi.org/10.1063/1.52802.

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Johnson, Jennifer A., and Thomas Masseron. "Abundance Ratios in Carbon‐Enhanced Metal‐Poor Stars and the Intermediate‐Mass Star Initial Mass Function." In FIRST STARS III: First Stars II Conference. American Institute of Physics, 2008. http://dx.doi.org/10.1063/1.2905540.

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Caballero, José A., and Eric Stempels. "Stars and brown dwarfs, spatial distribution, multiplicity, X-rays, discs, and the complete mass function of the σ Orionis cluster." In COOL STARS, STELLAR SYSTEMS AND THE SUN: Proceedings of the 15th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun. AIP, 2009. http://dx.doi.org/10.1063/1.3099266.

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Heap, Sara R. "Observations of the extragalactic initial mass function and modes of star formation." In The seventh astrophysical conference: Star formation, near and far. AIP, 1997. http://dx.doi.org/10.1063/1.52810.

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Boudreault, S., C. A. L. Bailer-Jones, and Eric Stempels. "A Constraint on brown dwarf formation via ejection: radial variation of the stellar and substellar mass function of the young open cluster IC 2391." In COOL STARS, STELLAR SYSTEMS AND THE SUN: Proceedings of the 15th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun. AIP, 2009. http://dx.doi.org/10.1063/1.3099264.

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Shustov, B. M. "ON THE UNIVERSAL BASIC DISTRIBUTION DESCRIBING THE INITIAL MASS FUNCTION OF VARIOUS ASTRONOMICAL OBJECTS." In 48-th International student's conferences "Physics of Space". Ural University Press, 2020. http://dx.doi.org/10.15826/b978-5-7996-2935-9.06.

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Suda, Takuma, Yutaka Komiya, Shimako Yamada, Yutaka Katsuta, Wako Aoki, Pilar Gil-Pons, Carolyn L. Doherty, Simon W. Campbell, Peter R. Wood, and Masayuki Y. Fujimoto. "Transition of the initial mass function in the galaxy based on binary population synthesis." In FIRST STARS IV – FROM HAYASHI TO THE FUTURE –. AIP, 2012. http://dx.doi.org/10.1063/1.4754407.

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Reports on the topic "Stellar initial mass function"

1

Yaron, Zvi, Abigail Elizur, Martin Schreibman, and Yonathan Zohar. Advancing Puberty in the Black Carp (Mylopharyngodon piceus) and the Striped Bass (Morone saxatilis). United States Department of Agriculture, January 2000. http://dx.doi.org/10.32747/2000.7695841.bard.

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Both the genes and cDNA sequences encoding the b-subunits of black carp LH and FSH were isolated, cloned and sequenced. Sequence analysis of the bcFSHb and LHb5'flanking regions revealed that the promoter region of both genes contains canonical TATA sequences, 30 bp and 17 bp upstream of the transcription start site of FSHb and LHb genes, respectively. In addition, they include several sequences of cis-acting motifs, required for inducible and tissue-specific transcriptional regulation: the gonadotropin-specific element (GSE), GnRH responsive element (GRE), half sites of estrogen and androgen response elements, cAMP response element, and AP1. Several methods have been employed by the Israeli team to purify the recombinant b subunits (EtOH precipitation, gel filtration and lentil lectin). While the final objective to produce pure recombinantGtH subunits has not yet been achieved, we have covered much ground towards this goal. The black carp ovary showed a gradual increase in both mass and oocyte diameter. First postvitellogenic oocytes were found in 5 yr old fish. At this age, the testes already contained spermatozoa. The circulating LH levels increased from 0.5 ng/ml in 4 yr old fish to >5ng/ml in 5 yr old fish. In vivo challenge experiments in black carp showed the initial LH response of the pituitary to GnRH in 4 yr old fish. The response was further augmented in 5 yr old fish. The increase in estradiol level in response to gonadotropic stimulation was first noted in 4 yr old fish but this response was much stronger in the following year. In vivo experiments on the FSHb and LHb mRNA levels in response to GnRH were carried out on common carp as a model for synchronom spawning cyprinids. These experiments showed the prevalence of FSHP in maturing fish while LHP mRNA was prevalent in mature fish, especially in females. The gonadal fat-pad was found to originate from the retroperitoneal mesoderm and not from the genital ridge, thus differing from that reported in certain amphibians This tissue possibly serves as the major source of sex steroids in the immature black carp. However, such a function is taken over by the developing gonads in 4 yr old fish. In the striped bass, we described the ontogeny of the neuro-endocrine parameters along the brain-pituitary-gonadal axis during the first four years of life, throughout gonadal development and the onset of puberty. We also described the responsiveness of the reproductive axis to long-term hormonal manipulations at various stages of gonadal development. Most males reached complete sexual maturity during the first year of life. Puberty was initiated during the third year of life in most females, but this first reproductive cycle did not lead to the acquisition of full sexual maturity. This finding indicates that more than one reproductive cycle may be required before adulthood is reached. Out of the three native GnRHs present in striped bass, only sbGnRH and cGnRH II increased concomitantly with the progress of gonadal development and the onset of puberty. This finding, together with data on GtH synthesis and release, suggests that while sbGnRH and cGnRH II may be involved in the regulation of puberty in striped bass, these neuropeptides are not limiting factors to the onset of puberty. Plasma LH levels remained low in all fish, suggesting that LH plays only a minor role in early gonadal development. This hypothesis was further supported by the finding that experimentally elevated plasma LH levels did not result in the induction of complete ovarian and testicular development. The acquisition of complete puberty in 4 yr old females was associated with a rise in the mRNA levels of all GtH subunit genes, including a 218-fold increase in the mRNA levels of bFSH. mRNA levels of the a and PLH subunits increased only 11- and 8-fold, respectively. Although data on plasma FSH levels are unavailable, the dramatic increase in bFSH mRNA suggests a pivotal role for this hormone in regulating the onset and completion of puberty in striped bass. The hormonal regulation of the onset of puberty and of GtH synthesis and release was studied by chronic administration of testosterone (T) and/or an analog of gonadotropin-releasing hormone (G). Sustained administration of T+G increased the mRNA levels of the PLH subunit to the values characteristic of sexually mature fish, and also increased the plasma levels of LH. However, these changes did not result in the acceleration of sexual maturation. The mRNA levels of the bFSH subunit were slightly stimulated, but remained about 1/10 of the values characteristic of sexually mature fish. It is concluded that the stimulation of FSH gene expression and release does not lead to the acceleration of sexual maturity, and that the failure to sufficiently stimulate the bFSH subunit gene expression may underlie the inability of the treatments to advance sexual maturity. Consequently, FSH is suggested to be the key hormone to the initiation and completion of puberty in striped bass. Future efforts to induce precocious puberty in striped bass should focus on understanding the regulation of FSH synthesis and release and on developing technologies to induce these processes. Definite formulation of hormonal manipulation to advance puberty in the striped bass and the black carp seems to be premature at this stage. However, the project has already yielded a great number of experimental tools of DNA technology, slow-release systems and endocrine information on the process of puberty. These systems and certain protocols have been already utilized successfully to advance maturation in other fish (e.g. grey mullet) and will form a base for further study on fish puberty.
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