scholarly journals The spatial evolution of young massive clusters

2019 ◽  
Vol 622 ◽  
pp. A184 ◽  
Author(s):  
Anne S. M. Buckner ◽  
Zeinab Khorrami ◽  
Pouria Khalaj ◽  
Stuart L. Lumsden ◽  
Isabelle Joncour ◽  
...  
Keyword(s):  
Spatial Clustering ◽  
Massive Stars ◽  
Quantitative Measure ◽  
Stellar Structure ◽  
Ob Stars ◽  
Star Forming ◽  
Star Forming Regions ◽  
Carina Nebula ◽  
Degree Of Association ◽  
Massive Clusters

Context. There are a number of methods that identify stellar sub-structure in star forming regions, but these do not quantify the degree of association of individual stars – something which is required if we are to better understand the mechanisms and physical processes that dictate structure. Aims. We present the new novel statistical clustering tool “INDICATE” which assesses and quantifies the degree of spatial clustering of each object in a dataset, discuss its applications as a tracer of morphological stellar features in star forming regions, and to look for these features in the Carina Nebula (NGC 3372). Methods. We employ a nearest neighbour approach to quantitatively compare the spatial distribution in the local neighbourhood of an object with that expected in an evenly spaced uniform (i.e. definitively non-clustered) field. Each object is assigned a clustering index (“I”) value, which is a quantitative measure of its clustering tendency. We have calibrated our tool against random distributions to aid interpretation and identification of significant I values. Results. Using INDICATE we successfully recover known stellar structure of the Carina Nebula, including the young Trumpler 14-16, Treasure Chest and Bochum 11 clusters. Four sub-clusters contain no, or very few, stars with a degree of association above random which suggests these sub-clusters may be fluctuations in the field rather than real clusters. In addition we find: (1) Stars in the NW and SE regions have significantly different clustering tendencies, which is reflective of differences in the apparent star formation activity in these regions. Further study is required to ascertain the physical origin of the difference; (2) The different clustering properties between the NW and SE regions are also seen for OB stars and are even more pronounced; (3) There are no signatures of classical mass segregation present in the SE region – massive stars here are not spatially concentrated together above random; (4) Stellar concentrations are more frequent around massive stars than typical for the general population, particularly in the Tr14 cluster; (5) There is a relation between the concentration of OB stars and the concentration of (lower mass) stars around OB stars in the centrally concentrated Tr14 and Tr15, but no such relation exists in Tr16. We conclude this is due to the highly sub-structured nature of Tr16. Conclusions. INDICATE is a powerful new tool employing a novel approach to quantify the clustering tendencies of individual objects in a dataset within a user-defined parameter space. As such it can be used in a wide array of data analysis applications. In this paper we have discussed and demonstrated its application to trace morphological features of young massive clusters.

scholarly journals Effect of Feedback of Massive Stars in the Fragmentation, Distribution, and Kinematics of the Gas in Two Star-forming Regions in the Carina Nebula

2020 ◽  
Vol 891 (2) ◽  
pp. 113
Author(s):  
David Rebolledo ◽  
Andrés E. Guzmán ◽  
Yanett Contreras ◽  
Guido Garay ◽  
S.-N. X. Medina ◽  
...  
Keyword(s):  
Massive Stars ◽  
Star Forming ◽  
Star Forming Regions ◽  
Carina Nebula

MASGOMAS project: building a bona-fide catalog of massive star cluster candidates

2016 ◽  
Vol 12 (S329) ◽  
pp. 406-406
Author(s):  
Artemio Herrero ◽  
Klaus Rübke ◽  
Sebastián Ramírez Alegría ◽  
Miriam Garcia ◽  
Antonio Marín-Franch
Keyword(s):  
Massive Star ◽  
Massive Stars ◽  
Star Cluster ◽  
Ob Stars ◽  
Star Forming ◽  
Bona Fide ◽  
Massive Clusters

MASGOMAS (MAssive Stars in Galactic Obscured MAssive clusterS) is a project aiming at discovering OB stars in Galactic, dust enshrouded, star-forming massive clusters (Marín-Franch et al. 2009, A&A 502, 559). The project has gone through different phases of increasing automatization, that have allowed us to discover massive clusters like MASGOMAS-1 (Ramírez Alegría et al. 2012, A&A 541, A75) (with M≈20,000 M⊙).

scholarly journals New massive members of Cygnus OB2

2018 ◽  
Vol 612 ◽  
pp. A50 ◽  
Author(s):  
S. R. Berlanas ◽  
A. Herrero ◽  
F. Comerón ◽  
A. Pasquali ◽  
C. Bertelli Motta ◽  
...  
Keyword(s):  
Massive Stars ◽  
Spectral Classification ◽  
Homogeneous Population ◽  
B Stars ◽  
Ob Stars ◽  
Star Forming ◽  
Star Forming Regions ◽  
Close Distance ◽  
Galactic Longitude

Context. The Cygnus complex is one of the most powerful star forming regions at a close distance from the Sun (~1.4 kpc). Its richest OB association Cygnus OB2 is known to harbor many tens of O-type stars and hundreds of B-type stars, providing a large homogeneous population of OB stars that can be analyzed. Many studies of its massive population have been developed in the last decades, although the total number of OB stars is still incomplete. Aim. Our aim is to increase the sample of O and B members of Cygnus OB2 and its surroundings by spectroscopically classifying 61 candidates as possible OB-type members of Cygnus OB2, using new intermediate resolution spectroscopy. Methods. We have obtained intermediate resolution (R ~ 5000) spectra for all of the OB-type candidates between 2013 and 2017. We thus performed a spectral classification of the sample using HeI-II and metal lines rates, as well as the Marxist Ghost Buster (MGB) software for O-type stars and the IACOB standards catalog for B-type stars. Results. From the whole sample of 61 candidates, we have classified 42 stars as new massive OB-type stars, earlier than B3, in Cygnus OB2 and surroundings, including 11 O-type stars. The other candidates are discarded as they display later spectral types inconsistent with membership in the association. We have also obtained visual extinctions for all the new confirmed massive OB members, placing them in a Hertzsprung-Russell Diagram using calibrations for Teff and luminosity. Finally, we have studied the age and extinction distribution of our sample within the region. Conclusions. We have obtained new blue intermediate-resolution spectra suitable for spectral classification of 61 OB candidates in Cygnus OB2 and surroundings. The confirmation of 42 new OB massive stars (earlier than B3) in the region allows us to increase the young massive population known in the field. We have also confirmed the correlation between age and Galactic longitude previously found in the region. We conclude that many O and early B stars at B > 16 mag are still undiscovered in Cygnus.

scholarly journals The Circumstellar Environment of Embedded Massive Stars

2002 ◽  
Vol 12 ◽  
pp. 143-145 ◽  
Author(s):  
Lee G. Mundy ◽  
Friedrich Wyrowski ◽  
Sarah Watt
Keyword(s):  
Massive Star ◽  
Massive Stars ◽  
Low Mass Stars ◽  
Submillimeter Wavelength ◽  
Star Forming ◽  
Star Forming Regions ◽  
Low Mass ◽  
Circumstellar Environments ◽  
Near Future

Millimeter and submillimeter wavelength images of massive star-forming regions are uncovering the natal material distribution and revealing the complexities of their circumstellar environments on size scales from parsecs to 100’s of AU. Progress in these areas has been slower than for low-mass stars because massive stars are more distant, and because they are gregarious siblings with different evolutionary stages that can co-exist even within a core. Nevertheless, observational goals for the near future include the characterization of an early evolutionary sequence for massive stars, determination if the accretion process and formation sequence for massive stars is similar to that of low-mass stars, and understanding of the role of triggering events in massive star formation.

scholarly journals Massive Stars at High Redshifts

2007 ◽  
Vol 3 (S250) ◽  
pp. 415-428
Author(s):  
Max Pettini
Keyword(s):  
Massive Stars ◽  
High Redshift ◽  
Mass Function ◽  
Initial Mass Function ◽  
Stellar Spectra ◽  
Star Forming ◽  
Star Forming Regions ◽  
Look Ahead ◽  
Low Metallicity ◽  
High Redshift Universe

AbstractThe five years that have passed since the last IAU Symposium devoted to massive stars have seen a veritable explosion of data on the high redshift universe. The tools developed to study massive stars in nearby galaxies are finding increasing application to the analysis of the spectra of star-forming regions at redshifts as high as z = 7. In this brief review, I consider three topics of relevance to this symposium: the determination of the metallicities of galaxies at high redshifts from consideration of their ultraviolet stellar spectra; constraints on the initial mass function of massive stars in galaxies at z = 2 − 3; and new clues to the nucleosynthesis of carbon and nitrogen in massive stars of low metallicity. The review concludes with a look ahead at some of the questions that may occupy us for the next five years (at least!).

scholarly journals OB stars towards NGC 6357 and NGC 6334

2017 ◽  
Vol 12 (S330) ◽  
pp. 341-342
Author(s):  
Delphine Russeil
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Stellar Population ◽  
Proper Motions ◽  
Massive Star Formation ◽  
Ob Stars ◽  
Stellar Cluster ◽  
Star Forming ◽  
Star Forming Regions ◽  
Ngc 6334

AbstractThe star forming regions NGC6334 and NGC6357 are amid the most active star-forming complexes of our Galaxy where massive star formation is occuring. Both complexes gather several HII regions but they exhibit different aspects: NGC6334 is characterised by a dense molecular ridge where recent massive star formation is obvious while NGC6357 is dominated by the action of the stellar cluster Pismis 24 which have shaped a large cavity. To understand and compare the formation of massive stars in these two regions requires to precise the distance and characterise the proper motions of the O to B3 stellar population in these regions.

scholarly journals Multiplicity and clustering in Taurus star forming region

2018 ◽  
Vol 620 ◽  
pp. A27 ◽  
Author(s):  
Isabelle Joncour ◽  
Gaspard Duchêne ◽  
Estelle Moraux ◽  
Frédérique Motte
Keyword(s):  
Star Formation ◽  
Nearest Neighbor ◽  
Spatial Clustering ◽  
Mean Value ◽  
K Nearest Neighbor ◽  
Star Forming ◽  
Star Forming Regions ◽  
Wide Pairs ◽  
A Chain ◽  
The One

Context. Multiplicity and clustering of young pre-main sequence stars appear as critical clues to understand and constrain the star formation process. Taurus is the archetypical example of the most quiescent star forming regions that may still retain primeval signatures of star formation. Aims. This work identifies local overdense stellar structures as a critical scale between wide pairs and loose groups in Taurus. Methods. Using the density-based spatial clustering of applications with noise (dbscan) algorithm, and setting its free parameters based on the one-point correlation function and the k-nearest neighbor statistics, we have extracted reliably overdense structures from the sky-projected spatial distribution of stars. Results. Nearly half of the entire stellar population in Taurus is found to be concentrated in 20 very dense, tiny and prolate regions called NESTs (for Nested Elementary STructures). They are regularly spaced (≈2 pc) and mainly oriented along the principal gas filaments axes. Each NEST contains between four and 23 stars. Inside NESTs, the surface density of stars may be as high as 2500 pc−2 and the mean value is 340 pc−2. Nearly half (11) of these NESTs contain about 75% of the class 0 and I objects. The balance between Class I, II, and, III fraction within the NESTs suggests that they may be ordered as an evolutionary temporal scheme, some of them getting infertile with time, while other still giving birth to young stars. We have inferred that only 20% of stars in Taurus do not belong to any kind of stellar groups (either multiple system, ultra wide pairs or NESTs). The mass-size relation for stellar NESTs is very close to the Bonnor–Ebert expectation. The range in mass is about the same as that of dense molecular cores. The distribution in size is bimodal peaking at 12.5 and 50 kAU and the distribution of the number of YSOs in NESTs as a function of size exhibits two regimes. Conclusions. We propose that the NESTs in their two size regimes represent the spatial imprints of stellar distribution at birth as they may have emerged within few millions years from their natal cloud either from a single core or from a chain of cores. We have identified them as the preferred sites of star formation in Taurus. These NESTs are the regions of highest stellar density and intermediate spatial scale structures between ultra-wide pairs and loose groups.

scholarly journals Ultraviolet spectra of extreme nearby star-forming regions: Evidence for an overabundance of very massive stars

2021 ◽  
Vol 503 (4) ◽  
pp. 6112-6135
Author(s):  
Peter Senchyna ◽  
Daniel P Stark ◽  
Stéphane Charlot ◽  
Jacopo Chevallard ◽  
Gustavo Bruzual ◽  
...  
Keyword(s):  
Stellar Wind ◽  
Massive Stars ◽  
Stellar Populations ◽  
Population Synthesis ◽  
Nearby Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
High Incidence ◽  
Stellar Population Synthesis ◽  
Stellar Masses

ABSTRACT As deep spectroscopic campaigns extend to higher redshifts and lower stellar masses, the interpretation of galaxy spectra depends increasingly upon models for very young stellar populations. Here we present new HST/COS ultraviolet spectroscopy of seven nearby (<120 Mpc) star-forming regions hosting very young stellar populations (∼4–20 Myr) with optical Wolf–Rayet stellar wind signatures, ideal laboratories in which to benchmark these stellar models. We detect nebular C iii] in all seven, but at equivalent widths uniformly <10 Å. This suggests that even for very young stellar populations, the highest equivalent width C iii] emission at ≥15 Å is reserved for inefficiently cooled gas at metallicities at or below that of the SMC. The spectra also reveal strong C iv P-Cygni profiles and broad He ii emission formed in the winds of massive stars, including some of the most prominent He ii stellar wind lines ever detected in integrated spectra. We find that the latest stellar population synthesis prescriptions with improved treatment of massive stars nearly reproduce the entire range of stellar He ii wind strengths observed here. However, we find that these models cannot simultaneously match the strongest wind features alongside the optical nebular line constraints. This discrepancy can be naturally explained by an overabundance of very massive stars produced by a high incidence of binary mass transfer and mergers occurring on short ≲10 Myr time-scales, suggesting these processes may be crucial for understanding systems dominated by young stars both nearby and in the early Universe.

scholarly journals The formation of young massive clusters triggered by cloud–cloud collisions in the Antennae galaxies NGC 4038/NGC 4039

2020 ◽  
Author(s):  
Kisetsu Tsuge ◽  
Yasuo Fukui ◽  
Kengo Tachihara ◽  
Hidetoshi Sano ◽  
Kazuki Tokuda ◽  
...  
Keyword(s):  
Formation Mechanism ◽  
Cluster Formation ◽  
Large Magellanic Cloud ◽  
Star Forming ◽  
Star Forming Regions ◽  
Region I ◽  
Major Merger ◽  
Super Star Clusters ◽  
Massive Clusters ◽  
Key Parameter

Abstract The formation mechanism of super star clusters (SSCs), present-day analogs of the ancient globulars, still remains elusive. The major merger that is the Antennae galaxies is forming SSCs and is one of the primary targets to test the cluster formation mechanism. We reanalyzed the archival ALMA CO data of the Antennae and found three typical observational signatures of a cloud–cloud collision toward SSC B1 and other SSCs in the overlap region: (i) two velocity components with ∼100 km s−1 velocity separation, (ii) bridge features connecting the two components, and (iii) a complementary spatial distribution between them, lending support to collisions of the two components as a cluster formation mechanism. We present a scenario that two clouds with 100 km s−1 velocity separation collided, and SSCs having ∼106–107 M⊙ were formed rapidly during that time scale. We compared the present results with the recent studies of star-forming regions in the Milky Way and the Large Magellanic Cloud, where the SSCs having ∼104–105 M⊙ are located. As a result, we found that there is a positive correlation between the compressed gas pressure generated by collisions and the total stellar mass of an SSC, suggesting that the pressure may be a key parameter in SSC formation.

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