scholarly journals IFS and IR Observations of Star Clusters in the Antennae

2002 ◽  
Vol 207 ◽  
pp. 378-382 ◽  
Author(s):  
Sabine Mengel ◽  
Matthew D. Lehnert ◽  
Niranjan Thatte ◽  
Reinhard Genzel
Keyword(s):  
Galaxy Evolution ◽  
Near Infrared ◽  
Narrow Band Imaging ◽  
Star Clusters ◽  
Young Star ◽  
High Resolution Spectroscopy ◽  
High Mass ◽  
Low Mass Stars ◽  
Integral Field Spectroscopy ◽  
Low Mass

Over the past decade, it has become clear that interaction induced formation of compact young star clusters is a ubiquitous pheonomenon, and the understanding of this process is thought to also shed light on galaxy evolution in general, because these young clusters are widely believed to be the progenitors of a part of the globular cluster systems seen in local elliptical galaxies. We have observed the prototypical merger NGC 4038/4039 using near-infrared broad- and narrow band imaging, integral field spectroscopy and medium and high resolution spectroscopy. We find that all of the bright star clusters are young (<20 Myrs), but the “overlap region” hosts the youngest clusters (∼5 Myrs), while the nuclear starbursts started ∼100 Myrs ago. Photometric and dynamical masses range from 105 to a few x106M⊙. However, mass-to-light ratios vary from cluster to cluster and suggest differences in the contribution of low-mass stars. While clusters with a deficiency in low-mass stars are likely to evaporate before they are a Hubble time old, those with a high mass-to-light-ratio could represent young globulars.

scholarly journals Multi-Wavelength High-Resolution Spectroscopy for Exoplanet Detection: Motivation, Instrumentation and First Results

Geosciences ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 289 ◽  
Author(s):  
Serena Benatti
Keyword(s):  
High Resolution ◽  
Near Infrared ◽  
Giant Planet ◽  
High Resolution Spectroscopy ◽  
M Dwarfs ◽  
Low Mass Stars ◽  
First Results ◽  
Multi Wavelength ◽  
Low Mass ◽  
Rocky Planets

Exoplanet research has shown an incessant growth since the first claim of a hot giant planet around a solar-like star in the mid-1990s. Today, the new facilities are working to spot the first habitable rocky planets around low-mass stars as a forerunner for the detection of the long-awaited Sun-Earth analog system. All the achievements in this field would not have been possible without the constant development of the technology and of new methods to detect more and more challenging planets. After the consolidation of a top-level instrumentation for high-resolution spectroscopy in the visible wavelength range, a huge effort is now dedicated to reaching the same precision and accuracy in the near-infrared. Actually, observations in this range present several advantages in the search for exoplanets around M dwarfs, known to be the most favorable targets to detect possible habitable planets. They are also characterized by intense stellar activity, which hampers planet detection, but its impact on the radial velocity modulation is mitigated in the infrared. Simultaneous observations in the visible and near-infrared ranges appear to be an even more powerful technique since they provide combined and complementary information, also useful for many other exoplanetary science cases.

scholarly journals Star Formation in NGC 4038/4039

2001 ◽  
Vol 205 ◽  
pp. 206-207
Author(s):  
Sabine Mengel ◽  
Niranjan Thatte ◽  
Matthew Lehnert ◽  
Reinhard Genzel
Keyword(s):  
Star Formation ◽  
Near Infrared ◽  
Spatial Scales ◽  
Star Clusters ◽  
Young Star ◽  
Bolometric Luminosity ◽  
Integral Field Spectroscopy ◽  
Show Evidence ◽  
Northwestern Region ◽  
Age Range

We performed near infrared integral field spectroscopy of several star clusters and the nuclei of the prototypical merger NGC 4038/39 (“The Antennae”). Near infrared (NIR) images covered both galaxies. The collision of the two gas-rich spiral galaxies has triggered a starburst obvious from a large number of young star clusters. ISO data suggest that the most active star formation occurs in the region where the two galaxy disks overlap. A significant fraction of the total bolometric luminosity of the system is produced there. Since this region is heavily extincted in the optical, the investigation was made in the NIR. Using Brγ emission and CO absorption features as age indicators, we derive the ages and mass estimates of the star clusters from a comparison with stellar synthesis models. Extinction is calculated from the Brγ/Hα ratio. The young, bright star clusters have ages ranging from 4-12 Myrs, while the nuclear starbursts are much older (50-80 Myrs). The overlap region hosts most of the youngest star clusters below ∼8 Myrs, while the northwestern region is dominated by star clusters in the age range between 8 and 12 Myrs. Several regions, including the northern nucleus, show evidence for sequential star formation on small spatial scales (< 100pc).

scholarly journals Ages of Galactic and Extragalactic Star Clusters of Various Abundances

1983 ◽  
Vol 6 ◽  
pp. 109-117 ◽  
Author(s):  
R.D. Cannon
Keyword(s):  
Star Clusters ◽  
Magellanic Clouds ◽  
Open Clusters ◽  
Simultaneous Solution ◽  
Low Mass Stars ◽  
Cluster Systems ◽  
Distant Cluster ◽  
Low Mass

In this review I shall concentrate mainly on globular star clusters in our Galaxy since these are the objects for which most work has been done recently, both observationally and theoretically. However, I shall also discuss briefly the oldest open clusters and clusters in the Magellanic Clouds. Little can be said about more distant cluster systems, since the only observations available are of integrated colours or spectra and these seem to be rather unreliable indicators of age. It is perhaps worth pointing out that the title may be slightly misleading; the problem is not so much to determine the ages of clusters of known abundances, as to obtain the best simultaneous solution for both age and composition, since some of the most important abundances (notably helium and oxygen) are virtually unobservable in little-evolved low mass stars.

scholarly journals Observations of low mass stars in clusters: Some constraints and puzzles for stellar evolution theory

1984 ◽  
Vol 105 ◽  
pp. 123-138
Author(s):  
R.D. Cannon
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
Star Clusters ◽  
Variable Stars ◽  
Open Clusters ◽  
Low Mass Stars ◽  
Theory Of Evolution ◽  
Theoretical Predictions ◽  
Low Mass ◽  
Red Giant

This review will attempt to do two things: (i) discuss some of the data which are available for testing the theory of evolution of low mass stars, and (ii) point out some problem areas where observations and theory do not seem to agree very well. This is of course too vast a field of research to be covered in one brief review, so I shall concentrate on one particular aspect, namely the study of star clusters and especially their colour-magnitude (CM) diagrams. Star clusters provide large samples of stars at the same distance and with the same age, and the CM diagram gives the easiest way of comparing theoretical predictions with observations, although crucial evidence is also provided by spectroscopic abundance analyses and studies of variable stars. Since this is primarily a review of observational data it is natural to divide it into two parts: (i) galactic globular clusters, and (ii) old and intermediate-age open clusters. Some additional evidence comes from Local Group galaxies, especially now that CM diagrams which reach the old main sequence are becoming available. For each class of cluster I shall consider successive stages of evolution from the main sequence, up the hydrogen-burning red giant branch, and through the helium-burning giant phase.

scholarly journals A LARGE-SCALE OPTICAL-NEAR-INFRARED SURVEY FOR BROWN DWARFS AND VERY LOW MASS STARS IN THE ORION OB1 ASSOCIATION

2008 ◽  
Vol 136 (1) ◽  
pp. 51-66 ◽  
Author(s):  
Juan José Downes ◽  
César Briceño ◽  
Jesús Hernández ◽  
Nuria Calvet ◽  
Lee Hartmann ◽  
...  
Keyword(s):  
Large Scale ◽  
Near Infrared ◽  
Brown Dwarfs ◽  
Low Mass Stars ◽  
Low Mass ◽  
Infrared Survey

scholarly journals Constraining star formation timescales with molecular gas and young star clusters

2019 ◽  
Vol 15 (S352) ◽  
pp. 350-352
Author(s):  
Kathryn Grasha ◽  
Daniela Calzetti
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Star Clusters ◽  
Young Star ◽  
Molecular Gas ◽  
Gas Reservoirs ◽  
Multi Wavelength ◽  
Predictive Theory ◽  
Young Star Clusters ◽  
Co Observations

AbstractStar formation provides insight into the physical processes that govern the transformation of gas into stars. A key missing piece in a predictive theory of star formation is the link between scales of individual stars and star clusters up to entire galaxies. LEGUS is now providing the information to test the overall organization and spatial evolution of star formation. We present our latest findings of using star clusters from LEGUS combined with ALMA CO observations to investigate the transition from molecular gas to star formation in local galaxies. This work paves the way for future JWST observations of the embedded phase of star formation, the last missing ingredient to connect young star clusters and their relation with gas reservoirs. Multi-wavelength studies of local galaxies and their stellar and gas components will help shed light on early phases of galaxy evolution and properties of the ISM at high-z.

scholarly journals What Causes the Low Binary Frequency in the Orion Nebula Cluster?

2004 ◽  
Vol 191 ◽  
pp. 104-108
Author(s):  
R. Köhler
Keyword(s):  
Statistical Significance ◽  
Formation Rate ◽  
High Mass ◽  
Cluster Center ◽  
Orion Nebula ◽  
Low Mass Stars ◽  
Cluster Radius ◽  
Companion Star ◽  
Binary Formation ◽  
Low Mass

AbstractWe report on the results of a binary survey in the outer parts of the Orion Nebula Cluster, 0.7 to 2 pc from the cluster center. The results should help to decide if the binary formation rate was lower in Orion than in Taurus-Auriga, or if many binaries formed initially, but were destroyed in close stellar encounters. We find that the binary frequency of low-mass stars does not depend on the distance to the cluster center. The companion star frequency of intermediate- to high-mass stars shows a trend to decrease with cluster radius, but the statistical significance of this trend is rather weak.

scholarly journals Young and intermediate-age massive star clusters

2010 ◽  
Vol 368 (1913) ◽  
pp. 867-887 ◽  
Author(s):  
Søren S. Larsen
Keyword(s):  
Star Formation ◽  
Star Clusters ◽  
Mass Function ◽  
Starburst Galaxies ◽  
Open Clusters ◽  
High Mass ◽  
Current Evidence ◽  
Power Law Distribution ◽  
Low Mass ◽  
Massive Clusters

An overview of our current understanding of the formation and evolution of star clusters is given, with the main emphasis on high-mass clusters. Clusters form deeply embedded within dense clouds of molecular gas. Left-over gas is cleared within a few million years and, depending on the efficiency of star formation, the clusters may disperse almost immediately or remain gravitationally bound. Current evidence suggests that a small percentage of star formation occurs in clusters that remain bound, although it is not yet clear whether this fraction is truly universal. Internal two-body relaxation and external shocks will lead to further, gradual dissolution on time scales of up to a few hundred million years for low-mass open clusters in the Milky Way, while the most massive clusters (>10 5  M ⊙ ) have lifetimes comparable to or exceeding the age of the Universe. The low-mass end of the initial cluster mass function is well approximated by a power-law distribution, , but there is mounting evidence that quiescent spiral discs form relatively few clusters with masses M >2×10 5  M ⊙ . In starburst galaxies and old globular cluster systems, this limit appears to be higher, at least several ×10 6  M ⊙ . The difference is likely related to the higher gas densities and pressures in starburst galaxies, which allow denser, more massive giant molecular clouds to form. Low-mass clusters may thus trace star formation quite universally, while the more long-lived, massive clusters appear to form preferentially in the context of violent star formation.

Magnetic fields of T Tauri stars and inner accretion discs

2018 ◽  
Vol 14 (A30) ◽  
pp. 121-121
Author(s):  
Jean-Francois Donati
Keyword(s):  
Magnetic Fields ◽  
Large Scale ◽  
Near Infrared ◽  
High Sensitivity ◽  
T Tauri Stars ◽  
Accretion Discs ◽  
High Resolution Spectroscopy ◽  
T Tauri ◽  
Low Mass ◽  
The Impact

AbstractMagnetic fields play a key role in the early life of stars and their planets, as they form from collapsing dense cores that progressively flatten into large-scale accretion discs and eventually settle as young suns orbited by planetary systems. Pre-main-sequence phases, in which central protostars feed from surrounding planet-forming accretion discs, are especially crucial for understanding how worlds like our Solar System are born.Magnetic fields of low-mass T Tauri stars (TTSs) are detected through high-resolution spectroscopy and spectropolarimetry (e.g., Johns Krull 2007), whereas their large-scale topologies can be inferred from time series of Zeeman signatures using tomographic techniques inspired from medical imaging (Donati & Landstreet 2009). Large-scale fields of TTSs are found to depend on the internal structure of the newborn star, allowing quantitative models of how TTSs magnetically interact with their inner accretion discs, and the impact of this interaction on the subsequent stellar evolution (e.g., Romanova et al. 2002, Zanni & Ferreira 2013).With its high sensitivity to magnetic fields, SPIRou, the new near-infrared spectropolarimeter installed in 2018 at CFHT (Donati et al. 2018), should yield new advances in the field, especially for young embedded class-I protostars, thereby bridging the gap with radio observations.

scholarly journals Fragmentation and dynamics in Massive Dense Cores in Cygnus-X

2010 ◽  
Vol 6 (S270) ◽  
pp. 53-56 ◽  
Author(s):  
T. Csengeri ◽  
S. Bontemps ◽  
N. Schneider ◽  
F. Motte
Keyword(s):  
Angular Resolution ◽  
High Density ◽  
High Mass ◽  
High Angular Resolution ◽  
Low Mass Stars ◽  
Dense Cores ◽  
Evolutionary Scenario ◽  
Low Mass ◽  
Molecular Tracers ◽  
Resolution Study

AbstractA systematic, high angular-resolution study of IR-quiet Massive Dense Cores (MDCs) of Cygnus-X in continuum and high-density molecular tracers is presented. The results are compared with the quasi-static and the dynamical evolutionary scenario. We find that the fragmentation properties are not compatible with the quasi-static, monolithic collapse scenario, nor are they entirely compatible with the formation of a cluster of mostly low-mass stars. The kinematics of MDCs shows individual velocity components appearing as coherent flows, which indicate important dynamical processes at the scale of the mass reservoir around high-mass protostars.

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