Journal Article

The low-mass initial mass function in the young cluster NGC 6611

J. M. Oliveira, R. D. Jeffries and J. Th. Van Loon

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 392, issue 3, pages 1034-1050
Published in print January 2009 | ISSN: 0035-8711
Published online January 2009 | e-ISSN: 1365-2966 | DOI:
The low-mass initial mass function in the young cluster NGC 6611

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NGC 6611 is the massive young cluster (2–3 Myr) that ionizes the Eagle Nebula. We present very deep photometric observations of the central region of NGC 6611 obtained with the Hubble Space Telescope and the following filters: ACS/WFC F775W and F850LP and NIC2 F110W and F160W, loosely equivalent to ground-based IZJH filters. This survey reaches down to I∼ 26 mag. We construct the initial mass function (IMF) from ∼1.5 M well into the brown dwarf regime (down to ∼0.02 M). We have detected 30–35 brown dwarf candidates in this sample. The low-mass IMF is combined with a higher-mass IMF constructed from the ground-based catalogue from Oliveira et al. We compare the final IMF with those of well-studied star-forming regions: we find that the IMF of NGC 6611 more closely resembles that of the low-mass star-forming region in Taurus than that of the more massive Orion Nebula Cluster. We conclude that there seems to be no severe environmental effect in the IMF due to the proximity of the massive stars in NGC 6611.

Keywords: stars: late-type; stars: low-mass, brown dwarfs; stars: luminosity function, mass function; stars: pre-main-sequence; open cluster and associations: individual: NGC 6611

Journal Article.  13746 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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