Properties of low-mass objects in NGC 2024

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Abstract

We have obtained deep JHK imaging of the central region of the NGC 2024 embedded cluster, allowing three-color measurements of 151 sources. We show that contamination by background sources is small, and we reject a small number of sources that are probably foreground. We use a Monte Carlo isochrone fitting technique to estimate the luminosities and masses of the low-mass members of the embedded cluster. We find that the IMF between ∼0.04 and ∼0.5 M can be fitted within the errors with a power law of slope -1.2 in linear mass units (or -0.2 in logarithmic units). There is no indication of a turnover of the IMF at the bottom of the main sequence; it appears to continue down to ∼0.04 Mg with no significant deviation (within our moderately large errors) from the power law. This estimate of the IMF includes only the primary members of binary (or multiple) systems. Of a subset of 35 sources, 24 (69%) appear to have infrared excesses indicating possible circumstellar disks, supporting arguments that disk formation is not inhibited in high-density clusters.

Original languageEnglish (US)
Pages (from-to)294-303
Number of pages10
JournalAstrophysical Journal
Volume473
Issue number1 PART I
DOIs
StatePublished - 1996

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IMF
power law
turnover
estimates
set theory
indication
contamination
luminosity
slopes
deviation
color

Keywords

  • H II regions
  • ISM: Individual (NGC 2024)
  • Open clusters and associations: Individual (NGC 2024)
  • Stars: Low-mass, brown dwarfs
  • Stars: Luminosity function, mass function

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Properties of low-mass objects in NGC 2024. / Comerón, F.; Rieke, George H.; Rieke, Marcia J.

In: Astrophysical Journal, Vol. 473, No. 1 PART I, 1996, p. 294-303.

Research output: Contribution to journalArticle

Comerón, F. ; Rieke, George H. ; Rieke, Marcia J. / Properties of low-mass objects in NGC 2024. In: Astrophysical Journal. 1996 ; Vol. 473, No. 1 PART I. pp. 294-303.
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AU - Rieke, George H.

AU - Rieke, Marcia J

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AB - We have obtained deep JHK imaging of the central region of the NGC 2024 embedded cluster, allowing three-color measurements of 151 sources. We show that contamination by background sources is small, and we reject a small number of sources that are probably foreground. We use a Monte Carlo isochrone fitting technique to estimate the luminosities and masses of the low-mass members of the embedded cluster. We find that the IMF between ∼0.04 and ∼0.5 M⊙ can be fitted within the errors with a power law of slope -1.2 in linear mass units (or -0.2 in logarithmic units). There is no indication of a turnover of the IMF at the bottom of the main sequence; it appears to continue down to ∼0.04 Mg with no significant deviation (within our moderately large errors) from the power law. This estimate of the IMF includes only the primary members of binary (or multiple) systems. Of a subset of 35 sources, 24 (69%) appear to have infrared excesses indicating possible circumstellar disks, supporting arguments that disk formation is not inhibited in high-density clusters.

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KW - Open clusters and associations: Individual (NGC 2024)

KW - Stars: Low-mass, brown dwarfs

KW - Stars: Luminosity function, mass function

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