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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
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:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 53 2054 Sources detected in the NICMOS camera 3 mosaics
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
Bytes Format Units Label Explanations
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
Note (1): * for objects located in a NICMOS field that could not be astrometrically calibrated to previous surveys
Acknowledgements: Morten Andersen, manderse(at)
(End) Patricia Vannier [CDS] 25-Oct-2011
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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