scholarly journals Determination of kinematic distances of pre-main-sequence stars in star-forming regions

2009 ◽  
Vol 5 (S266) ◽  
pp. 395-398
Author(s):  
Phillip A. B. Galli ◽  
Ramachrisna Teixeira ◽  
Christine Ducourant ◽  
Claude Bertout
Keyword(s):  
Main Sequence ◽  
Young Stars ◽  
Formation Mechanisms ◽  
Main Sequence Stars ◽  
Star Forming ◽  
Know How ◽  
Star Forming Regions ◽  
Moving Groups ◽  
Kinematic Properties

AbstractMany studies of star-forming regions have been carried out since the discovery of compact Hii regions in the late 1960s. The kinematic properties of young stars in the nearest regions with ongoing and recent star formation provide essential tests of their formation mechanisms. The detection of coeval moving groups allows determination of individual distances through the convergent-point method. As a result, the main physical properties of these stars and their early evolutionary stages can be determined if we know how distant they are.

scholarly journals Binary Frequency Among Pre-Main Sequence Stars in Taurus and Ophiuchus

1989 ◽  
Vol 8 ◽  
pp. 117-118
Author(s):  
M. Simon
Keyword(s):  
Binary Systems ◽  
Main Sequence ◽  
Young Stars ◽  
Main Sequence Stars ◽  
Star Forming ◽  
Lunar Occultation ◽  
Star Forming Regions ◽  
Powerful Means ◽  
Comparable Sample

AbstractThe lunar occultation technique applied in the IR offers a powerful means of identifying binaries among obscured young stars. Our program has revealed binaries with separations from 1 to 100 AU in the Taurus and Ophiuchus star forming regions to about K=9 mag. To date, 29 objects have been observed; 6 were discovered to be binaries. The observed binary frequency is about half that expected from the binary statistics of a comparable sample of field stars. The discrepancy is probably attributable to our insensitivity to binary systems with secondary mass much less than that of the primary.

scholarly journals Kinematic distances of pre-main-sequence stars in the Lupus star-forming region

2012 ◽  
Vol 8 (S289) ◽  
pp. 390-393
Author(s):  
P. A. B. Galli ◽  
R. Teixeira ◽  
C. Ducourant ◽  
C. Bertout
Keyword(s):  
Average Distance ◽  
Primary Objective ◽  
Physical Parameters ◽  
Main Sequence Stars ◽  
Nearby Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Group Members ◽  
Moving Groups ◽  
Kinematic Properties

AbstractTo reliably determine the main physical parameters (masses and ages) of young stars, we must know their distances. While the average distance to nearby star-forming regions (<300 pc) is often known, the distances to individual stars are usually unknown. Individual distances to members of young moving groups can be derived from their radial velocities and proper motions using the convergent-point strategy. We investigate the kinematic properties of the Lupus moving group with the primary objective of deriving individual distances to all group members.

The Multiplicity of Pre–Main‐Sequence Stars in Southern Star‐forming Regions

1997 ◽  
Vol 481 (1) ◽  
pp. 378-385 ◽  
Author(s):  
A. M. Ghez ◽  
D. W. McCarthy ◽  
J. L. Patience ◽  
T. L. Beck
Keyword(s):  
Main Sequence ◽  
Main Sequence Stars ◽  
Star Forming ◽  
Star Forming Regions

scholarly journals 3D mapping of young stars in the solar neighbourhood with Gaia DR2

2018 ◽  
Vol 620 ◽  
pp. A172 ◽  
Author(s):  
E. Zari ◽  
H. Hashemi ◽  
A. G. A. Brown ◽  
K. Jardine ◽  
P. T. de Zeeuw
Keyword(s):  
Main Sequence ◽  
Three Dimensional ◽  
Young Stars ◽  
Solar Neighbourhood ◽  
Mass Star ◽  
Early Type ◽  
Star Forming ◽  
Star Forming Regions ◽  
Density Maps ◽  
Early Type Stars

We study the three dimensional arrangement of young stars in the solar neighbourhood using the second release of the Gaia mission (Gaia DR2) and we provide a new, original view of the spatial configuration of the star-forming regions within 500 pc of the Sun. By smoothing the star distribution through a Gaussian filter, we construct three dimensional (3D) density maps for early-type stars (upper-main sequence, UMS) and pre-main sequence (PMS) sources. The PMS and the UMS samples are selected through a combination of photometric and astrometric criteria. A side product of the analysis is a 3D, G-band extinction map, which we use to correct our colour-magnitude diagram for extinction and reddening. Both density maps show three prominent structures, Scorpius-Centaurus, Orion, and Vela. The PMS map shows a plethora of lower-mass star-forming regions, such as Taurus, Perseus, Cepheus, Cassiopeia, and Lacerta, which are less visible in the UMS map due to the lack of large numbers of bright, early-type stars. We report the finding of a candidate new open cluster towards l, b ∼ 218.5° , − 2°, which could be related to the Orion star-forming complex. We estimate ages for the PMS sample and we study the distribution of PMS stars as a function of their age. We find that younger stars cluster in dense, compact clumps, and are surrounded by older sources, whose distribution is instead more diffuse. The youngest groups that we find are mainly located in Scorpius-Centaurus, Orion, Vela, and Taurus. Cepheus, Cassiopeia, and Lacerta are instead more evolved and less numerous. Finally, we find that the 3D density maps show no evidence for the existence of the ring-like structure which is usually referred to as the Gould Belt.

scholarly journals The VMC survey – XXXIV. Morphology of stellar populations in the Magellanic Clouds

2019 ◽  
Vol 490 (1) ◽  
pp. 1076-1093 ◽  
Author(s):  
Dalal El Youssoufi ◽  
Maria-Rosa L Cioni ◽  
Cameron P M Bell ◽  
Stefano Rubele ◽  
Kenji Bekki ◽  
...  
Keyword(s):  
Main Sequence ◽  
Near Infrared ◽  
Stellar Populations ◽  
Magellanic Clouds ◽  
Main Sequence Stars ◽  
Spiral Arms ◽  
Star Forming ◽  
Star Forming Regions ◽  
Tidal Interactions ◽  
Using Data

ABSTRACT The Magellanic Clouds are nearby dwarf irregular galaxies whose morphologies show different properties when traced by different stellar populations, making them an important laboratory for studying galaxy morphologies. We study the morphology of the Magellanic Clouds using data from the Visible and Infrared Survey Telescope for Astronomy survey of the Magellanic Clouds system. We used about 10 and 2.5 million sources across an area of ∼105 and ∼42 deg2 towards the Large and Small Magellanic Cloud (LMC and SMC), respectively. We estimated median ages of stellar populations occupying different regions of the near-infrared (J − Ks, Ks) colour–magnitude diagram. Morphological maps were produced and detailed features in the central regions were characterized for the first time with bins corresponding to a spatial resolution of 0.13 kpc (LMC) and 0.16 kpc (SMC). In the LMC, we find that main-sequence stars show coherent structures that grow with age and trace the multiple spiral arms of the galaxy, star-forming regions become dimmer as we progress in age, while supergiant stars are centrally concentrated. Intermediate-age stars, despite tracing a regular and symmetrical morphology, show central clumps and hints of spiral arms. In the SMC, young main-sequence stars depict a broken bar. Intermediate-age populations show signatures of elongation towards the Magellanic Bridge that can be attributed to the LMC–SMC interaction ∼200 Myr ago. They also show irregular central features suggesting that the inner SMC has also been influenced by tidal interactions.

Clustering of Pre–Main‐Sequence Stars in the Orion, Ophiuchus, Chamaeleon, Vela, and Lupus Star‐forming Regions

1998 ◽  
Vol 497 (2) ◽  
pp. 721-735 ◽  
Author(s):  
Yasushi Nakajima ◽  
Kengo Tachihara ◽  
Tomoyuki Hanawa ◽  
Makoto Nakano
Keyword(s):  
Main Sequence ◽  
Main Sequence Stars ◽  
Star Forming ◽  
Star Forming Regions

scholarly journals T Tauri Disk Lifetime in the Lupus Association

2015 ◽  
Vol 10 (S314) ◽  
pp. 191-192
Author(s):  
P. A. B. Galli ◽  
C. Bertout ◽  
R. Teixeira ◽  
C. Ducourant
Keyword(s):  
Main Sequence ◽  
T Tauri Stars ◽  
Young Stars ◽  
Main Sequence Stars ◽  
Disk Model ◽  
Star Forming ◽  
T Tauri

AbstractIn a recent study, we derived individual distances for a sample of pre-main sequence stars that define the comoving association of young stars in the Lupus star-forming region. Here, we use these new distances to investigate the mass and age distributions of Lupus T Tauri stars and derive the average disk lifetime in the Lupus association based on an empirical disk model.

scholarly journals On the mass segregation of cores and stars

2019 ◽  
Vol 490 (1) ◽  
pp. 350-358
Author(s):  
Hayley L Alcock ◽  
Richard J Parker
Keyword(s):  
Main Sequence ◽  
Dynamical Evolution ◽  
Initial Mass Function ◽  
Fragmentation Model ◽  
Main Sequence Stars ◽  
Apparent Contradiction ◽  
Star Forming ◽  
Star Forming Regions ◽  
Mass Segregation ◽  
Massive Cores

ABSTRACT Observations of pre- and proto-stellar cores in young star-forming regions show them to be mass segregated, i.e. the most massive cores are centrally concentrated, whereas pre-main-sequence stars in the same star-forming regions (and older regions) are not. We test whether this apparent contradiction can be explained by the massive cores fragmenting into stars of much lower mass, thereby washing out any signature of mass segregation in pre-main-sequence stars. Whilst our fragmentation model can reproduce the stellar initial mass function, we find that the resultant distribution of pre-main sequence stars is mass segregated to an even higher degree than that of the cores, because massive cores still produce massive stars if the number of fragments is reasonably low (between one and five). We therefore suggest that the reason cores are observed to be mass segregated and stars are not is likely due to dynamical evolution of the stars, which can move significant distances in star-forming regions after their formation.

Stellar Kinematics in Star-Forming Regions

1984 ◽  
Vol 88 ◽  
pp. 263-264
Author(s):  
Robert D. Mathieu ◽  
David W. Latham ◽  
Lee Hartmann
Keyword(s):  
Radial Velocity ◽  
Measurement Errors ◽  
Main Sequence ◽  
Stellar Kinematics ◽  
Late Type ◽  
Stellar Rotation ◽  
Main Sequence Stars ◽  
Central Wavelength ◽  
Star Forming ◽  
Star Forming Regions

High-precision radial-velocity studies of three young, star-forming regions - λ Orionis, NGC 2264 and Taurus-Auriga - are under way; study of the Orion cluster (with L. Marschall, in conjunction with the Yale proper-motion study) is beginning this winter. Single-order (~50 A, central wavelength 5200A) echelle spectra have been obtained for late-type pre-main sequence stars. Due to the spectral peculiarities and stellar rotation associated with pre-main sequence stars, our radial-velocity precisions are often somewhat poorer than those obtained for late-type dwarfs or giants. Measurement errors of 0.7-1.5 km/sec are typical, although some stars do not permit any radial velocity measurement at all. We summarize preliminary findings for each region:

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