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J/ApJ/540/236       KH photometry of Orion Nebula Cluster   (Hillenbrand+, 2000)

Constraints on the stellar/substellar mass function in the inner Orion Nebula Cluster. Hillenbrand L.A., Carpenter J.M. <Astrophys. J. 540, 236 (2000)> =2000ApJ...540..236H
ADC_Keywords: Clusters, open ; Photometry, infrared Keywords: circumstellar matter - open clusters and associations: individual (Orion Nebula Cluster) - stars: luminosity function, mass function - stars: pre-main-sequence Abstract: We present the results of a 0.5"-0.9" FWHM imaging survey at K (2.2µm) and H (1.6µm) covering ∼ 5.1'x5.1' centered on θ1C Ori, the most massive star in the Orion Nebula Cluster (ONC). At the age and distance of this cluster, and in the absence of extinction, the hydrogen-burning limit (0.08M) occurs at K∼13.5mag, while an object of mass 0.02M has K∼16.2mag. Our photometry is complete for source detection at the 7σ level to K∼17.5mag and thus is sensitive to objects as low-mass as 0.02M seen through visual extinction values as high as 10mag. We use the observed magnitudes, colors, and star counts to constrain the shape of the inner ONC stellar mass function across the hydrogen-burning limit. After determining the stellar age and near-infrared excess properties of the optically visible stars in this same inner ONC region, we present a new technique that incorporates these distributions when extracting the mass function from the observed density of stars in the K-(H-K) diagram. We find that our data are inconsistent with a mass function that rises across the stellar/substellar boundary. Instead, we find that the most likely form of the inner ONC mass function is one that rises to a peak around 0.15M, and then declines across the hydrogen-burning limit with slope N(log M)∝M0.57. We emphasize that our conclusions apply to the inner 0.71pc x 0.71pc of the ONC only; they may not apply to the ONC as a whole where some evidence for general mass segregation has been found. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 92 777 Keck/NIRC photometry and astrometry for the inner ONC
See also: Byte-by-byte Description of file: table1.dat Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 3 I3 --- [HC2000] Orion Nebula Cluster Identification number (1) 6 I1 h RAh Right Ascension (J2000) (2) 8- 9 I2 min RAm Right Ascension (J2000) (2) 11- 15 F5.2 s RAs Right Ascension (J2000) (2) 17 A1 --- DE- Declination (J2000) (2) 18 I1 deg DEd Declination (J2000) (2) 20- 21 I2 arcmin DEm Declination (J2000) (2) 23- 26 F4.1 arcsec DEs Declination (J2000) (2) 28 A1 --- l_Kmag Limit on Kmag 29- 34 F6.3 mag Kmag ? The 2.2µm magnitude from Keck/NIRC 37 A1 --- l_Hmag Limit on Hmag 38- 43 F6.3 mag Hmag ? The 1.6µm magnitude from Keck/NIRC 45- 50 F6.3 mag e_Kmag ? IRAF/PHOT errors in Kmag; intended for relative comparison only 52- 57 F6.3 mag e_Hmag ? IRAF/PHOT errors in Hmag; intended for relative comparison only 59- 69 A11 --- OptID Optical identification (3) 71- 90 A20 --- AltID Alternative IR identification (4)
Note (1): Object 187 is missing as this source is no longer believed real. Note (2): Coordinates referenced to the ACT catalog; note that this astrometry is offset by +1.5" in right ascension and -0.3" in declination from that reported in Hillenbrand (1997, Cat. J/AJ/113/1733>) Note (3): Identification numbers as listed in Hillenbrand (1997, Cat. J/AJ/113/1733), NNNNa ([H97b] NNNNa in Simbad) or from O'Dell & Wong (1996, Cat. J/AJ/111/846>), OW-NNN-NNN ([OW94] NNN-NNN in Simbad) Note (4): Identification numbers: MS-NN: TCC NNN in Simbad, McCaughrean & Stauffer (1994AJ....108.1382M) LBLS-a: LBLS a in Simbad, Lonsdale et al. (1982AJ.....87.1819L) IRcN: [RLK73] IRc N in Simbad, Downes et al. (1981ApJ...244..869D) and Rieke, Low, & Kleinmann (1973ApJ...186L...7R)
History: From ApJ electronic version
(End) Greg Schwartz [AAS], Patricia Bauer [CDS] 05-Dec-2000
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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