J/MNRAS/392/1034 IZJHKL' photometry of NGC 6611 (Oliveira+, 2009)
The low-mass initial mass function in the young cluster NGC 6611.
Oliveira J.M., Jeffries R.D., van Loon J.T.
<Mon. Not. R. Astron. Soc., 392, 1034-1050 (2009)>
=2009MNRAS.392.1034O 2009MNRAS.392.1034O
ADC_Keywords: Clusters, open ; Stars, pre-main sequence ; Photometry, HST ;
Photometry, infrared ; Stars, masses
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
Abstract:
NGC 6611 is the massive young cluster (2-3Myr) 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∼26mag. We construct the initial mass function (IMF) from
∼1.5M☉ well into the brown dwarf regime (down to ∼0.02M☉).
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.
Description:
The Hubble Space Telescope images of the core of NGC 6611 described
here were obtained as part of the cycle 14 programme number 10533
(P.I. J.M. Oliveira). Optical images were obtained with the Wide Field
Channel (WFC) of the Advanced Camera for Surveys A single ACS/WFC
field was observed through the F775W and F850LP filters (roughly
corresponding to ground-based I and Z).
Near-infrared images were obtained with the Near-Infrared Camera and
Multi-Object Spectrometer (NICMOS) on board HST. The filters used are
F110W and F160W. These correspond loosely to ground-based J and H
filters, but the reader should note that the F110W is much broader
than any other commonly used J-band filters (0.8-1.4um).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 121 290 NGC 6611 cluster candidates selected from the
HST photometric catalog
table2.dat 113 150 *NGC 6611 cluster candidates selected from the
photometric catalogue of Oliveira et al.
(2005MNRAS.358L..21O 2005MNRAS.358L..21O)
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Note on table2.dat: E(B-V)=0.70 is the extinction assumed for all PMS
candidates.
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See also:
J/AJ/106/1906 : NGC 6611: A Cluster Caught in the Act (Hillenbrand+ 1993)
J/A+AS/121/223 : Multiphotometry of NGC 6611 (de Winter+ 1997)
J/A+AS/134/525 : NGC 6611 compiled catalog (Belikov+ 1999)
J/A+AS/144/195 : UBVRI polarimetric observations in NGC 6611 (Orsatti+, 2000)
J/A+A/395/823 : CCD Δa-photometry of 5 open clusters (Paunzen+, 2002)
J/A+A/437/467 : VLT-FLAMES survey of massive stars (Evans+, 2005)
J/A+A/457/265 : VLT-FLAMES Survey of Massive Stars (Dufton+, 2006)
J/AJ/132/1783 : UBVRI polarimetry of 25 stars in NGC 6611 (Orsatti+, 2006)
J/A+A/462/245 : BVI photometry in NGC 6611 (Guarcello+, 2007)
J/A+A/496/453 : Photometry of candidate members of NGC6611 (Guarcello+, 2009)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 2 I2 h RAh Right ascension (J2000) (G1)
4- 5 I2 min RAm Right ascension (J2000) (G1)
7- 11 F5.2 s RAs Right ascension (J2000) (G1)
13 A1 --- DE- Declination sign (J2000) (G1)
14- 15 I2 deg DEd Declination (J2000) (G1)
17- 18 I2 arcmin DEm Declination (J2000) (G1)
20- 24 F5.2 arcsec DEs Declination (J2000) (G1)
26- 31 F6.3 mag Imag I magnitude
33- 37 F5.3 mag e_Imag rms uncertainty on Imag
39- 44 F6.3 mag Zmag Z magnitude
46- 50 F5.3 mag e_Zmag rms uncertainty on Zmag
52- 57 F6.3 mag Jmag J magnitude
59- 63 F5.3 mag e_Jmag rms uncertainty on Jmag
65- 70 F6.3 mag Hmag H magnitude
72- 76 F5.3 mag e_Hmag rms uncertainty on Hmag
78- 82 F5.2 mag E(B-V) ? Extinction determined using the 2Myr isochrone
84- 87 F4.2 mag e_E(B-V) ? rms uncertainty on E(B-V)
89- 93 F5.2 mag E(B-V)3 ? Extinction determined using the 3Myr isochrone
95- 98 F4.2 mag e_E(B-V)3 ? rms uncertainty on E(B-V)3
100-109 A10 --- Member Status (member or non member)
111-115 F5.3 solMass M2Myr ? Mass of PMS object assuming an age of 2Myr
117-121 F5.3 solMass M3Myr ? Mass of PMS object assuming an age of 3Myr
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 2 I2 h RAh 2MASS Right ascension (J2000) (G1)
4- 5 I2 min RAm 2MASS Right ascension (J2000) (G1)
7- 11 F5.2 s RAs 2MASS Right ascension (J2000) (G1)
13 A1 --- DE- 2MASS Declination sign (J2000) (G1)
14- 15 I2 deg DEd 2MASS Declination (J2000) (G1)
17- 18 I2 arcmin DEm 2MASS Declination (J2000) (G1)
20- 24 F5.2 arcsec DEs 2MASS Declination (J2000) (G1)
26- 31 F6.3 mag Imag I magnitude
33- 37 F5.3 mag e_Imag rms uncertainty on Imag
39- 43 F5.3 mag I-Z I-Z colour index
45- 49 F5.3 mag e_I-Z rms uncertainty on I-Z
51- 56 F6.3 mag Jmag J magnitude
58- 62 F5.3 mag e_Jmag rms uncertainty on Jmag
64- 69 F6.3 mag Hmag H magnitude
71- 75 F5.3 mag e_Hmag rms uncertainty on Hmag
77- 82 F6.3 mag Kmag K magnitude
84- 88 F5.3 mag e_Kmag rms uncertainty on Kmag
90- 95 F6.3 mag L'mag ? L' magnitude (centered at 3.77µm)
97-101 F5.3 mag e_L'mag ? rms uncertainty on L'mag
103-107 F5.3 solMass M2Myr ? Mass of PMS object assuming an age of 2Myr
109-113 F5.3 solMass M3Myr ? Mass of PMS object assuming an age of 3Myr
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Global notes:
Note (G1): Objects identified as [OJV2009] JHHMMSS.ss+DDMMSS.ss in Simbad
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History:
* 16-Sep-2009: From electronic version of the journal
* 07-Jul-2010: Declinations corrected in table1, from author
(End) Patricia Vannier [CDS] 13-Aug-2009