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 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:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 92 777 Keck/NIRC photometry and astrometry for the inner ONC
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See also:
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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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)
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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 1994AJ....108.1382M)
LBLS-a: LBLS a in Simbad, Lonsdale et al. (1982AJ.....87.1819L 1982AJ.....87.1819L)
IRcN: [RLK73] IRc N in Simbad, Downes et al. (1981ApJ...244..869D 1981ApJ...244..869D)
and Rieke, Low, & Kleinmann (1973ApJ...186L...7R 1973ApJ...186L...7R)
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History:
From ApJ electronic version
(End) Greg Schwartz [AAS], Patricia Bauer [CDS] 05-Dec-2000