Journal Article

Triggered star formation and evolution of T-Tauri stars in and around bright-rimmed clouds

Neelam Chauhan, A. K. Pandey, K. Ogura, D. K. Ojha, B. C. Bhatt, S. K. Ghosh and P. S. Rawat

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 396, issue 2, pages 964-983
Published in print June 2009 | ISSN: 0035-8711
Published online June 2009 | e-ISSN: 1365-2966 | DOI: https://dx.doi.org/10.1111/j.1365-2966.2009.14756.x
Triggered star formation and evolution of T-Tauri stars in and around bright-rimmed clouds

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The aim of this paper is to quantitatively testify the ‘small-scale sequential star formation’ hypothesis in and around bright-rimmed clouds (BRCs). As a continuation of the recent attempt by Ogura et al., we have carried out BVIc photometry of four more BRC aggregates along with deeper re-observations of two previously observed BRCs. Again, quantitative age gradients are found in almost all the BRCs studied in the present work. Archival Spitzer/Infrared Array Camera data also support this result. The global distribution of near-infrared excess stars in each H ii region studied here clearly shows evidence that a series of radiation-driven implosion processes proceeded in the past from near the central O star(s) towards the peripheries of the H ii region. We found that in general weak-line T-Tauri stars (WTTSs) are somewhat older than classical T-Tauri stars (CTTSs). Also the fraction of CTTSs among the T-Tauri stars (TTSs) associated with the BRCs is found to decrease with age. These facts are in accordance with the recent conclusion by Bertout, Siess & Cabrit that CTTSs evolve into WTTSs. It seems that in general the equivalent width of Hα emission in TTSs associated with the BRCs decreases with age. The mass function (MF) of the aggregates associated with the BRCs of the morphological type ‘A’ seems to follow that found in young open clusters, whereas ‘B/C’-type BRCs show significantly steeper MF.

Keywords: stars: evolution; stars: formation; stars: pre-main-sequence; H ii regions

Journal Article.  14871 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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