Subjects -> PHYSICS (Total: 857 journals)     - ELECTRICITY AND MAGNETISM (10 journals)    - MECHANICS (22 journals)    - NUCLEAR PHYSICS (53 journals)    - OPTICS (92 journals)    - PHYSICS (625 journals)    - SOUND (25 journals)    - THERMODYNAMICS (30 journals) PHYSICS (625 journals)                  1 2 3 4 | Last

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 Astronomy and Astrophysics ReviewJournal Prestige (SJR): 3.385 Citation Impact (citeScore): 5Number of Followers: 39      Hybrid journal (It can contain Open Access articles) ISSN (Print) 1432-0754 - ISSN (Online) 0935-4956 Published by Springer-Verlag  [2469 journals]
• Ram pressure stripping in high-density environments

Abstract: Abstract Galaxies living in rich environments are suffering different perturbations able to drastically affect their evolution. Among these, ram pressure stripping, i.e. the pressure exerted by the hot and dense intracluster medium (ICM) on galaxies moving at high velocity within the cluster gravitational potential well, is a key process able to remove their interstellar medium (ISM) and quench their activity of star formation. This review is aimed at describing this physical mechanism in different environments, from rich clusters of galaxies to loose and compact groups. We summarise the effects of this perturbing process on the baryonic components of galaxies, from the different gas phases (cold atomic and molecular, ionised, hot) to magnetic fields and cosmic rays, and describe their induced effects on the different stellar populations, with a particular attention to its role in the quenching episode generally observed in high-density environments. We also discuss on the possible fate of the stripped material once removed from the perturbed galaxies and mixed with the ICM, and we try to estimate its contribution to the pollution of the surrounding environment. Finally, combining the results of local and high-redshift observations with the prediction of tuned models and simulations, we try to quantify the importance of this process on the evolution of galaxies of different mass, from dwarfs to giants, in various environments and at different epochs.
PubDate: 2022-05-18

• Fast radio bursts at the dawn of the 2020s

Abstract: Abstract Since the discovery of the first fast radio burst (FRB) in 2007, and their confirmation as an abundant extragalactic population in 2013, the study of these sources has expanded at an incredible rate. In our 2019 review on the subject, we presented a growing, but still mysterious, population of FRBs—60 unique sources, 2 repeating FRBs, and only 1 identified host galaxy. However, in only a few short years, new observations and discoveries have given us a wealth of information about these sources. The total FRB population now stands at over 600 published sources, 24 repeaters, and 19 host galaxies. Higher time resolution data, sustained monitoring, and precision localisations have given us insight into repeaters, host galaxies, burst morphology, source activity, progenitor models, and the use of FRBs as cosmological probes. The recent detection of a bright FRB-like burst from the Galactic magnetar SGR 1935 + 2154 provides an important link between FRBs and magnetars. There also continue to be surprising discoveries, like periodic modulation of activity from repeaters and the localisation of one FRB source to a relatively nearby globular cluster associated with the M81 galaxy. In this review, we summarise the exciting observational results from the past few years. We also highlight their impact on our understanding of the FRB population and proposed progenitor models. We build on the introduction to FRBs in our earlier review, update our readers on recent results, and discuss interesting avenues for exploration as the field enters a new regime where hundreds to thousands of new FRBs will be discovered and reported each year.
PubDate: 2022-03-29
DOI: 10.1007/s00159-022-00139-w

• The growing threat of light pollution to ground-based observatories

Abstract: Abstract Human activity is rapidly increasing the negative impact of artificial skyglow at even the most remote professional observatory sites. Assessment of the actual impact requires an understanding of the propagation as a function of source spectral energy distribution. The higher blue content of light-emitting diodes being widely used as replacement for sodium discharge lamps has greater impact closer to the source, and less impact for more distant mountain-top sites. All-sky cameras with moderate angular resolution provide data and metrics sufficient to model and remove celestial contributions and provide measures of artificial light contribution. The natural skyglow is significantly affected by solar activity, which must be accounted for in determining secular trends in the artificial component. With the availability of the New World Atlas of the Artificial Sky Brightness, a direct comparison is made of the modeled artificial contribution to the sites with the largest aperture telescopes, noting the possible systematic errors in individual cases. Population growth of the nearest urban centers allows a prediction of the change in that brightness over a decade. All site protections are effected primarily by national or regional regulation. A collection of worldwide regulations shows that most are leveraged off environmental protection statutes, while in the U.S., they are largely based on land-use zones. Particular examples are presented in more detail for Flagstaff, Arizona, and the Island of Hawai’i. The latest rapidly growing threat is that of reflected sunlight from large constellations of satellites in low-earth orbit. A snapshot is provided of that rapidly changing situation. In all cases, astronomers must become very proactive in educating the public about the cultural value of visual or naked eye astronomy as well as the science and the need for access to a dark night sky for astronomical research.
PubDate: 2022-01-27
DOI: 10.1007/s00159-021-00138-3

• A buyer’s guide to the Hubble constant

Abstract: Abstract Since the expansion of the universe was first established by Edwin Hubble and Georges Lemaître about a century ago, the Hubble constant $$H_0$$ which measures its rate has been of great interest to astronomers. Besides being interesting in its own right, few properties of the universe can be deduced without it. In the last decade, a significant gap has emerged between different methods of measuring it, some anchored in the nearby universe, others at cosmological distances. The SH0ES team has found $$H_0 = 73.2 \pm 1.3 \; \;\,\hbox {kms}^{-1} \,\hbox {Mpc}^{-1}$$ locally, whereas the value found for the early universe by the Planck Collaboration is $$H_0 = 67.4 \pm 0.5 \; \;\,\hbox {kms}^{-1} \,\hbox {Mpc}^{-1}$$ from measurements of the cosmic microwave background. Is this gap a sign that the well-established $${\varLambda} {\text{CDM}}$$ cosmological model is somehow incomplete' Or are there unknown systematics' And more practically, how should humble astronomers pick between competing claims if they need to assume a value for a certain purpose' In this article, we review results and what changes to the cosmological model could be needed to accommodate them all. For astronomers in a hurry, we provide a buyer’s guide to the results, and make recommendations.
PubDate: 2021-12-01
DOI: 10.1007/s00159-021-00137-4

• Radiation environment for future human exploration on the surface of Mars:
the current understanding based on MSL/RAD dose measurements

Abstract: Abstract Potential deleterious health effects to astronauts induced by space radiation is one of the most important long-term risks for human space missions, especially future planetary missions to Mars which require a return-trip duration of about 3 years with current propulsion technology. In preparation for future human exploration, the Radiation Assessment Detector (RAD) was designed to detect and analyze the most biologically hazardous energetic particle radiation on the Martian surface as part of the Mars Science Laboratory (MSL) mission. RAD has measured the deep space radiation field within the spacecraft during the cruise to Mars and the cosmic ray induced energetic particle radiation on Mars since Curiosity’s landing in August 2012. These first-ever surface radiation data have been continuously providing a unique and direct assessment of the radiation environment on Mars. We analyze the temporal variation of the Galactic Cosmic Ray (GCR) radiation and the observed Solar Energetic Particle (SEP) events measured by RAD from the launch of MSL until December 2020, i.e., from the pre-maximum of solar cycle 24 throughout its solar minimum until the initial year of Cycle 25. Over the long term, the Mars’s surface GCR radiation increased by about 50% due to the declining solar activity and the weakening heliospheric magnetic field. At different time scales in a shorter term, RAD also detected dynamic variations in the radiation field on Mars. We present and quantify the temporal changes of the radiation field which are mainly caused by: (a) heliospheric influences which include both temporary impacts by solar transients and the long-term solar cycle evolution, (b) atmospheric changes which include the Martian daily thermal tide and seasonal CO $$_2$$ cycle as well as the altitude change of the rover, (c) topographical changes along the rover path-way causing addition structural shielding and finally (d) solar particle events which occur sporadically and may significantly enhance the radiation within a short time period. Quantification of the variation allows the estimation of the accumulated radiation for a return trip to the surface of Mars under various conditions. The accumulated GCR dose equivalent, via a Hohmann transfer, is about $$0.65 \pm 0.24$$ sievert and $$1.59 \pm 0.12$$ sievert during solar maximum and minimum periods, respectively. The shielding of the GCR radiation by heliospheric magnetic fields during solar maximum periods is rather efficient in reducing the total GCR-induced radiation for a Mars mission, by more than 50%. However, further contributions by SEPs must also be taken into account. In the future, with advanced nuclear thrusters via a fast transfer, we estimate that the total GCR dose equivalent can be reduced to about 0.2 sievert and 0.5 sievert during solar maximum and minimum periods respectively. In addition, we also examined factors which may further reduce the radiation dose in space and on Mars and discuss the many uncertainties in the interpreting the biological effect based on the current measurement.
PubDate: 2021-09-21
DOI: 10.1007/s00159-021-00136-5

• Ultra-light dark matter

Abstract: Abstract Ultra-light dark matter is a class of dark matter models (DM), where DM is composed by bosons with masses ranging from $$10^{-24}\, \mathrm {eV}< m < \mathrm {eV}$$ . These models have been receiving a lot of attention in the past few years given their interesting property of forming a Bose–Einstein condensate (BEC) or a superfluid on galactic scales. BEC and superfluidity are some of the most striking quantum mechanical phenomena that manifest on macroscopic scales, and upon condensation, the particles behave as a single coherent state, described by the wavefunction of the condensate. The idea is that condensation takes place inside galaxies while outside, on large scales, it recovers the successes of $$\varLambda$$ CDM. This wave nature of DM on galactic scales that arise upon condensation can address some of the curiosities of the behaviour of DM on small-scales. There are many models in the literature that describe a DM component that condenses in galaxies. In this review, we are going to describe those models, and classify them into three classes, according to the different non-linear evolution and structures they form in galaxies: the fuzzy dark matter (FDM), the self-interacting fuzzy dark matter (SIFDM), and the DM superfluid. Each of these classes comprises many models, each presenting a similar phenomenology in galaxies. They also include some microscopic models like the axions and axion-like particles. To understand and describe this phenomenology in galaxies, we are going to review the phenomena of BEC and superfluidity that arise in condensed matter physics, and apply this knowledge to DM. We describe how ULDM can potentially reconcile the cold DM picture with the small-scale behaviour. These models present a rich phenomenology that is manifest in different astrophysical consequences. We review here the astrophysical and cosmological tests used to constrain those models, together with new and future observations that promise to test these models in different regimes. For the case of the FDM class, the mass where this model has an interesting phenomenology on small-scales $$\sim 10^{-22}\, \mathrm {eV}$$ , is strongly challenged by current observations. The parameter space for the other two classes remains weakly constrained. We finalize by showing some predictions that are a consequence of the wave nature of this component, like the creation of vortices and interference patterns, that could represent a smoking gun in the search of these rich and interesting alternative class of DM models.
PubDate: 2021-09-09
DOI: 10.1007/s00159-021-00135-6

• Astrophotonics: astronomy and modern optics

Abstract: Abstract Much of the progress in astronomy has been driven by instrumental developments, from the first telescopes to fiber fed spectrographs. In this review, we describe the field of astrophotonics, a combination of photonics and astronomical instrumentation that is gaining importance in the development of current and future instrumentation. We begin with the science cases that have been identified as possibly benefiting from astrophotonic devices. We then discuss devices, methods and developments in the field along with the advantages they provide. We conclude by describing possible future perspectives in the field and their influence on astronomy.
PubDate: 2021-09-03
DOI: 10.1007/s00159-021-00134-7

• Modelling the chemical evolution of the Milky Way

Abstract: Abstract In this review, I will discuss the comparison between model results and observational data for the Milky Way, the predictive power of such models as well as their limits. Such a comparison, known as Galactic archaeology, allows us to impose constraints on stellar nucleosynthesis and timescales of formation of the various Galactic components (halo, bulge, thick disk and thin disk).
PubDate: 2021-08-27
DOI: 10.1007/s00159-021-00133-8

• Weighing stars from birth to death: mass determination methods across the
HRD

Abstract: Abstract The mass of a star is the most fundamental parameter for its structure, evolution, and final fate. It is particularly important for any kind of stellar archaeology and characterization of exoplanets. There exist a variety of methods in astronomy to estimate or determine it. In this review we present a significant number of such methods, beginning with the most direct and model-independent approach using detached eclipsing binaries. We then move to more indirect and model-dependent methods, such as the quite commonly used isochrone or stellar track fitting. The arrival of quantitative asteroseismology has opened a completely new approach to determine stellar masses and to complement and improve the accuracy of other methods. We include methods for different evolutionary stages, from the pre-main sequence to evolved (super)giants and final remnants. For all methods uncertainties and restrictions will be discussed. We provide lists of altogether more than 200 benchmark stars with relative mass accuracies between $$[0.3,2]\%$$ for the covered mass range of $$M\in [0.1,16]\,M_\odot$$ , $$75\%$$ of which are stars burning hydrogen in their core and the other $$25\%$$ covering all other evolved stages. We close with a recommendation how to combine various methods to arrive at a “mass-ladder” for stars.
PubDate: 2021-05-26
DOI: 10.1007/s00159-021-00132-9

• Compact steep-spectrum and peaked-spectrum radio sources

Abstract: Abstract Compact steep-spectrum (CSS) and peaked-spectrum (PS) radio sources are compact, powerful radio sources. The multi-frequency observational properties and current theories are reviewed with emphasis on developments since the earlier review of O’Dea (PASP 110:493–532, https://doi.org/10.1086/316162, 1998). There are three main hypotheses for the nature of PS and CSS sources. (1) The PS sources might be very young radio galaxies which will evolve into CSS sources on their way to becoming large radio galaxies. (2) The PS and CSS sources might be compact, because they are confined (and enhanced in radio power) by interaction with dense gas in their environments. (3) Alternately, the PS sources might be transient or intermittent sources. Each of these hypotheses may apply to individual objects. The relative number in each population will have significant implications for the radio galaxy paradigm. Proper motion studies over long time baselines have helped determine hotspot speeds for over three dozen sources and establish that these are young objects. Multi-frequency polarization observations have demonstrated that many CSS/PS sources are embedded in a dense interstellar medium and vigorously interacting with it. The detection of emission line gas aligned with the radio source, and blue-shifted Hi absorption, and [OIII] emission lines indicates that AGN feedback is present in these objects—possibly driven by the radio source. Also, CSS/PS sources with evidence of episodic AGN over a large range of time-scales have been discussed. The review closes with a discussion of open questions and prospects for the future.
PubDate: 2021-03-30
DOI: 10.1007/s00159-021-00131-w

• Star formation and nuclear activity in luminous infrared galaxies: an

Abstract: Abstract Nearby galaxies offer unique laboratories allowing multi-wavelength spatially resolved studies of the interstellar medium, star formation and nuclear activity across a broad range of physical conditions. In particular, detailed studies of individual local luminous infrared galaxies (LIRGs) are crucial for gaining a better understanding of these processes and for developing and testing models that are used to explain statistical studies of large populations of such galaxies at high redshift for which it is currently impossible to reach a sufficient physical resolution. Here, we provide an overview of the impact of spatially resolved infrared, sub-millimetre and radio observations in the study of the interstellar medium, star formation and active galactic nuclei as well as their interplay in local LIRGs. We also present an overview of the modelling of their spectral energy distributions using state-of-the-art radiative transfer codes. These contribute necessary and powerful ‘workhorse’ tools for the study of LIRGs (and their more luminous counterparts) at higher redshifts which are unresolved in observations. We describe how spatially-resolved time-domain observations have recently opened a new window to study the nuclear activity in LIRGs. We describe in detail the observational characteristics of Arp 299 which is one of the best studied local LIRGs and exemplifies the power of the combination of time-domain and high-resolution observations at infrared to radio wavelengths together with radiative transfer modelling used to explain the spectral energy distributions of its different components. We summarise the previous achievements obtained using high-spatial resolution observations and provide an outlook into what we can expect to achieve with future facilities.
PubDate: 2021-01-13
DOI: 10.1007/s00159-020-00128-x

• Magnetic fields of M dwarfs

Abstract: Abstract Magnetic fields play a fundamental role for interior and atmospheric properties of M dwarfs and greatly influence terrestrial planets orbiting in the habitable zones of these low-mass stars. Determination of the strength and topology of magnetic fields, both on stellar surfaces and throughout the extended stellar magnetospheres, is a key ingredient for advancing stellar and planetary science. Here, modern methods of magnetic field measurements applied to M-dwarf stars are reviewed, with an emphasis on direct diagnostics based on interpretation of the Zeeman effect signatures in high-resolution intensity and polarisation spectra. Results of the mean field strength measurements derived from Zeeman broadening analyses as well as information on the global magnetic geometries inferred by applying tomographic mapping methods to spectropolarimetric observations are summarised and critically evaluated. The emerging understanding of the complex, multi-scale nature of M-dwarf magnetic fields is discussed in the context of theoretical models of hydromagnetic dynamos and stellar interior structure altered by magnetic fields.
PubDate: 2020-12-12
DOI: 10.1007/s00159-020-00130-3

• Cluster–galaxy weak lensing

Abstract: Abstract Weak gravitational lensing of background galaxies provides a direct probe of the projected matter distribution in and around galaxy clusters. Here, we present a self-contained pedagogical review of cluster–galaxy weak lensing, covering a range of topics relevant to its cosmological and astrophysical applications. We begin by reviewing the theoretical foundations of gravitational lensing from first principles, with a special attention to the basics and advanced techniques of weak gravitational lensing. We summarize and discuss key findings from recent cluster–galaxy weak-lensing studies on both observational and theoretical grounds, with a focus on cluster mass profiles, the concentration–mass relation, the splashback radius, and implications from extensive mass-calibration efforts for cluster cosmology.
PubDate: 2020-11-16
DOI: 10.1007/s00159-020-00129-w

• Precise radio astrometry and new developments for the next generation of
instruments

Abstract: Abstract We present a technique-led review of the progression of precise radio astrometry, from the first demonstrations, half a century ago, until to date and into the future. We cover the developments that have been fundamental to allow high accuracy and precision astrometry to be regularly achieved. We review the opportunities provided by the next generation of instruments coming online, which are primarily: SKA, ngVLA, and pathfinders, along with EHT and other (sub)mm-wavelength arrays, Space-VLBI, Geodetic arrays, and optical astrometry from GAIA. From the historical development, we predict the future potential astrometric performance, and, therefore, the instrumental requirements that must be provided to deliver these. The next generation of methods will allow ultra-precise astrometry to be performed at a much wider range of frequencies (hundreds of MHz to hundreds of GHz). One of the key potentials is that astrometry will become generally applicable, and, therefore, unbiased large surveys can be performed. The next-generation methods are fundamental in allowing this. We review the small but growing number of major astrometric surveys in the radio, to highlight the scientific impact that such projects can provide. Based on these perspectives, the future of radio astrometry is bright. We foresee a revolution coming from: ultra-high-precision radio astrometry, large surveys of many objects, improved sky coverage, and at new frequency bands other than those available today. These will enable the addressing of a host of innovative open scientific questions in astrophysics.
PubDate: 2020-09-29
DOI: 10.1007/s00159-020-00126-z

• Multiple populations in massive star clusters under the magnifying glass
of photometry: theory and tools

Abstract: Abstract The existence of star-to-star light-element abundance variations in massive Galactic and extragalactic star clusters has fairly recently superseded the traditional paradigm of individual clusters hosting stars with the same age, and uniform chemical composition. Several scenarios have been put forward to explain the origin of this multiple stellar population phenomenon, but so far all have failed to reproduce the whole range of key observations. Complementary to high-resolution spectroscopy, which has first revealed and characterized chemically the presence of multiple populations in Galactic globular clusters, photometry has been instrumental in investigating this phenomenon in much larger samples of stars—adding a number of crucial observational constraints and correlations with global cluster properties—and in the discovery and characterization of multiple populations also in Magellanic Clouds’ intermediate-age clusters. The purpose of this review is to present the theoretical underpinning and application of the photometric techniques devised to identify and study multiple populations in resolved star clusters. These methods have played and continue to play a crucial role in advancing our knowledge of the cluster multiple population phenomenon, and promise to extend the scope of these investigations to resolved clusters even beyond the Local Group, with the launch of the James Webb Space Telescope.
PubDate: 2020-07-07
DOI: 10.1007/s00159-020-00127-y

• Nuclear star clusters

Abstract: Abstract We review the current knowledge about nuclear star clusters (NSCs), the spectacularly dense and massive assemblies of stars found at the centers of most galaxies. Recent observational and theoretical works suggest that many NSC properties, including their masses, densities, and stellar populations, vary with the properties of their host galaxies. Understanding the formation, growth, and ultimate fate of NSCs, therefore, is crucial for a complete picture of galaxy evolution. Throughout the review, we attempt to combine and distill the available evidence into a coherent picture of NSC evolution. Combined, this evidence points to a clear transition mass in galaxies of $$\sim 10^9\,M_\odot$$ where the characteristics of nuclear star clusters change. We argue that at lower masses, NSCs are formed primarily from globular clusters that inspiral into the center of the galaxy, while at higher masses, star formation within the nucleus forms the bulk of the NSC. We also discuss the co-existence of NSCs and central black holes, and how their growth may be linked. The extreme densities of NSCs and their interaction with massive black holes lead to a wide range of unique phenomena including tidal disruption and gravitational-wave events. Finally, we review the evidence that many NSCs end up in the halos of massive galaxies stripped of the stars that surrounded them, thus providing valuable tracers of the galaxies’ accretion histories.
PubDate: 2020-07-06
DOI: 10.1007/s00159-020-00125-0

• Observations of galactic and extragalactic novae

Abstract: Abstract The recent GAIA DR2 measurements of distances to galactic novae have allowed to re-analyse some properties of nova populations in the Milky Way and in external galaxies on new and more solid empirical bases. In some cases, we have been able to confirm results previously obtained, such as the concept of nova populations into two classes of objects, that is disk and bulge novae and their link with the Tololo spectroscopic classification in Fe II and He/N novae. The recent and robust estimates of nova rates in the Magellanic Clouds galaxies provided by the OGLE team have confirmed the dependence of the normalized nova rate (i.e., the nova rate per unit of luminosity of the host galaxy) with the colors and/or class of luminosity of the parent galaxies. The nova rates in the Milky Way and in external galaxies have been collected from literature and critically discussed. They are the necessary ingredient to asses the contribution of novae to the nucleosynthesis of the respective host galaxies, particularly to explain the origin of the overabundance of lithium observed in young stellar populations. A direct comparison between distances obtained via GAIA DR2 and maximum magnitude vs. rate of decline (MMRD) relationship points out that the MMRD can provide distances with an uncertainty better than 30%. Multiwavelength observations of novae along the whole electromagnetic spectrum, from radio to gamma rays, have revealed that novae undergo a complex evolution characterized by several emission phases and a non-spherical geometry for the nova ejecta.
PubDate: 2020-07-02
DOI: 10.1007/s00159-020-0124-6

• Cool outflows in galaxies and their implications

Abstract: Abstract Neutral-atomic and molecular outflows are a common occurrence in galaxies, near and far. They operate over the full extent of their galaxy hosts, from the innermost regions of galactic nuclei to the outermost reaches of galaxy halos. They carry a substantial amount of material that would otherwise have been used to form new stars. These cool outflows may have a profound impact on the evolution of their host galaxies and environments. This article provides an overview of the basic physics of cool outflows, a comprehensive assessment of the observational techniques and diagnostic tools used to characterize them, a detailed description of the best-studied cases, and a more general discussion of the statistical properties of these outflows in the local and distant universe. The remaining outstanding issues that have not yet been resolved are summarized at the end of the review to inspire new research directions.
PubDate: 2020-04-03
DOI: 10.1007/s00159-019-0121-9

• Molecular jets from low-mass young protostellar objects

Abstract: Abstract Molecular jets are seen coming from the youngest protostars in the early phase of low-mass star formation. They are detected in CO, SiO, and SO at (sub)millimeter wavelengths down to the innermost regions, where their associated protostars and accretion disks are deeply embedded and where they are launched and collimated. They are not only the fossil records of accretion history of the protostars but also are expected to play an important role in facilitating the accretion process. Studying their physical properties (e.g., mass-loss rate, velocity, rotation, radius, wiggle, molecular content, shock formation, periodical variation, magnetic field, etc) allows us to probe not only the jet launching and collimation, but also the disk accretion and evolution, and potentially binary formation and planetary formation in the disks. Here, the recent exciting results obtained with high-spatial and high-velocity resolution observations of molecular jets in comparison to those obtained in the optical jets in the later phase of star formation are reviewed. Future observations of molecular jets with a large sample at high spatial and velocity resolution with ALMA are expected to lead to a breakthrough in our understanding of jets from young stars.
PubDate: 2020-03-31
DOI: 10.1007/s00159-020-0123-7

• What is a globular cluster' An observational perspective

Abstract: Abstract Globular clusters are large and dense agglomerate of stars. At variance with smaller clusters of stars, they exhibit signs of some chemical evolution. At least for this reason, they are intermediate between open clusters and massive objects such as nuclear clusters or compact galaxies. While some facts are well established, the increasing amount of observational data are revealing a complexity that has so far defied the attempts to interpret the whole data set in a simple scenario. We review this topic focusing on the main observational features of clusters in the Milky Way and its satellites. We find that most of the observational facts related to the chemical evolution in globular clusters are described as being primarily a function of the initial mass of the clusters, tuned by further dependence on the metallicity—that mainly affects specific aspects of the nucleosynthesis processes involved—and on the environment, that likely determines the possibility of independent chemical evolution of the fragments or satellites, where the clusters form. We review the impact of multiple populations on different regions of the colour–magnitude diagram and underline the constraints related to the observed abundances of lithium, to the cluster dynamics, and to the frequency of binaries in stars of different chemical composition. We then re-consider the issues related to the mass budget and the relation between globular cluster and field stars. Any successful model of globular cluster formation should explain these facts.
PubDate: 2019-11-04
DOI: 10.1007/s00159-019-0119-3

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