J/A+A/534/A10 HST/NICMOS III imaging in Orion Nebula Cluster (Andersen+, 2011)
The low-mass initial mass function in the Orion nebula cluster based on
HST/NICMOS III imaging.
Andersen M., Meyer M.R., Robberto M., Bergeron L.E., Reid N.
<Astron. Astrophys. 534, A10 (2011)>
=2011A&A...534A..10A 2011A&A...534A..10A
ADC_Keywords: Clusters, open ; Stars, pre-main sequence ; Photometry, HST
Keywords: brown dwarfs - stars: formation - stars: pre-main sequence -
stars: luminosity function, mass function - stars: low-mass
Abstract:
We present deep HST/NICMOS Camera 3 F110W and F160W imaging of a
26'x33', corresponding to 3.1x3.8pc2, non-contiguous field towards
the Orion Nebula Cluster (ONC). The main aim is to determine the ratio
of low-mass stars to brown dwarfs for the cluster as a function of
radius out to a radial distance of 1.5pc. The sensitivity of the data
outside the nebulous central region is F160W≤21.0mag, significantly
deeper than previous studies of the region over a comparable area. We
create an extinction limited sample and determine the ratio of
low-mass stars (0.08-1M☉) to brown dwarfs (0.02-0.08M☉
and 0.03-0.08M☉) for the cluster as a whole and for several
annuli. The ratio found for the cluster within a radius of 1.5pc is
R02=N(0.08-1M☉)/N(0.02-0.08M☉)=1.7±0.2, and
R03=N(0.08-1M☉)/N(0.03-0.08M☉)=2.4±0.2, after
correcting for field stars. The ratio for the central 0.3x0.3pc2
region down to 0.03M☉ was previously found to be
R03=3.3+0.8-0.7, suggesting the low-mass content of the cluster
is mass segregated. We discuss the implications of a gradient in the
ratio of stars to brown dwarfs in the ONC in the context of previous
measurements of the cluster and for other nearby star forming regions.
We further discuss the current evidence for variations in the low-mass
IMF and primordial mass segregation.
Description:
Photometry for sources in the HST/NICMOS survey and their location.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 53 2054 Sources detected in the NICMOS camera 3 mosaics
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See also:
J/AJ/120/1426 : Chandra sources in ONC + BN-KL (Garmire+, 2000)
J/AJ/121/1676 : ONC low-mass stars photometry (Rebull+, 2001)
J/ApJ/660/704 : Optical and X-ray variability of ONC PMS (Stassun+, 2007)
J/ApJ/660/1462 : Abundances of ONC X-ray PMS stars (Maggio+, 2007)
J/ApJ/671/605 : NGC 2264 and ONC PMS stars in the infrared (Cieza+, 2007)
J/ApJ/677/401 : X-ray properties of protostars in ONC (Prisinzano+, 2008)
J/ApJS/183/261 : Optical photometry of the ONC (Da Rio+, 2009)
J/MNRAS/400/603 : New variables in ONC (Parihar+, 2009)
J/A+A/502/883 : ONC very low mass stars I phot. (Rodriguez-Ledesma+, 2009)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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2- 5 I4 --- Seq [0/2053] Sequential number
6 A1 --- n_Seq [*] no astrometric calibration (1)
8- 15 F8.5 deg RAdeg Right ascension in decimal degrees (J2000)
18- 25 F8.5 deg DEdeg Declination in decimal degrees (J2000)
28- 32 F5.2 mag F110W ?=99 HST/NICMOS F110W magnitude (VEGA system)
35- 39 F5.2 mag e_F110W ?=99 F110W error
42- 46 F5.2 mag F160W HST/NICMOS F160W magnitude (VEGA system)
49- 53 F5.2 mag e_F160W F160W error
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Note (1): * for objects located in a NICMOS field that could not be
astrometrically calibrated to previous surveys
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Acknowledgements:
Morten Andersen, manderse(at)rssd.esa.int
(End) Patricia Vannier [CDS] 25-Oct-2011