An X-ray census of young stars in the Chamaeleon I North Cloud

Eric D. Feigelson, Warrick A. Lawson

Research output: Contribution to journalArticle

28 Citations (Scopus)

Abstract

Sensitive X-ray imaging surveys provide a new and effective tool to establish the census of pre-main-sequence (PMS) stars in nearby young stellar clusters. We report here a deep Chandra X-Ray Observatory observation of PMS stars in the Chamaeleon I North cloud, achieving a limiting luminosity of log Lt ≃ 27 ergs s-1 (0.5-8 keV band) in a 0.8 × 0.8 pc2 region. Of the 107 X-ray sources, 37 are associated with Galactic stars of which 27 are previously recognized cloud members. These include three PMS brown dwarfs; the protostellar brown dwarf ISO 192 has a particularly high level of magnetic activity. Follow-up optical photometry and spectroscopy establish that 9-10 of the Chandra sources are probably magnetically active background stars. Several previously proposed cloud members are also inferred to be interlopers because of the absence of X-ray emission at the level expected from the log Lt-K correlation. No new X-ray-discovered stars were confidently found despite the high sensitivity. From these findings, we argue that the sample of 27 PMS cloud members in the Chandra field is uncontaminated and complete down to K = 12 or M ≃ 0.1 M. The initial mass function (IMF) derived from our sample is deficient in 0.1-0.3 M stars compared with the IMF of the rich Orion Nebula cluster and other Galactic populations. We cannot discriminate whether this is due to different star formation processes, mass segregation, or dynamical ejection of lower mass stars.

Original languageEnglish (US)
Pages (from-to)267-283
Number of pages17
JournalAstrophysical Journal
Volume614
Issue number1 I
DOIs
StatePublished - Oct 10 2004

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census
stars
pre-main sequence stars
x rays
Orion nebula
M stars
ejection
erg
photometry
star formation
observatories
observatory
spectroscopy
luminosity
young
sensitivity

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Feigelson, Eric D. ; Lawson, Warrick A. / An X-ray census of young stars in the Chamaeleon I North Cloud. In: Astrophysical Journal. 2004 ; Vol. 614, No. 1 I. pp. 267-283.
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An X-ray census of young stars in the Chamaeleon I North Cloud. / Feigelson, Eric D.; Lawson, Warrick A.

In: Astrophysical Journal, Vol. 614, No. 1 I, 10.10.2004, p. 267-283.

Research output: Contribution to journalArticle

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