J/ApJ/748/14 ONC population data from WFI observations (Da Rio+, 2012)
The initial mass function of the Orion Nebula Cluster across the H-burning
limit.
Da Rio N., Robberto M., Hillenbrand L.A., Henning T., Stassun K.G.
<Astrophys. J., 748, 14 (2012)>
=2012ApJ...748...14D 2012ApJ...748...14D
ADC_Keywords: Stars, masses ; Stars, ages ; Effective temperatures ;
Extinction ; Clusters, open
Keywords: brown dwarfs - Hertzsprung-Russell and C-M diagrams -
open clusters and associations: individual (Orion) -
stars: formation - stars: luminosity function, mass function -
stars: pre-main sequence
Abstract:
We present a new census of the Orion Nebula Cluster over a large field
of view (≳30'x30'), significantly increasing the known population of
stellar and substellar cluster members with precisely determined
properties. We develop and exploit a technique to determine stellar
effective temperatures from optical colors, nearly doubling the
previously available number of objects with effective temperature
determinations in this benchmark cluster. Our technique utilizes
colors from deep photometry in the I band and in two medium-band
filters at λ∼753 and 770nm, which accurately measure the depth
of a molecular feature present in the spectra of cool stars. From
these colors we can derive effective temperatures with a precision
corresponding to better than one-half spectral subtype, and
importantly this precision is independent of the extinction to the
individual stars. Also, because this technique utilizes only
photometry redward of 750nm, the results are only mildly sensitive to
optical veiling produced by accretion. Completing our census with
previously available data, we place some 1750 sources in the
Hertzsprung-Russell diagram and assign masses and ages down to
0.02M☉. At faint luminosities, we detect a large population of
background sources which is easily separated in our photometry from
the bona fide cluster members. The resulting initial mass function of
the cluster has good completeness well into the substellar mass range,
and we find that it declines steeply with decreasing mass. This
suggests a deficiency of newly formed brown dwarfs in the cluster
compared to the Galactic disk population.
Description:
Observations were carried out with the Wide Field Imager (WFI), a
focal reducer-type camera mounted at the Cassegrain focus of the 2.2m
MPG/ESO telescope at La Silla. The FOV of the camera is ∼32'x33',
allowing us to cover the entire ONC with one pointing. We selected two
WFI medium-band filters which provide the best sampling of a deep
absorption band at λ∼7700Å and ∼7530Å. We also used a
broad I-band filter (∼8600Å) in order to evaluate the photospheric
reddening from dust extinction. The WFI imaging was carried out during
five nights of 2010 December.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 117 1743 Derived stellar parameters of the ONC population
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See also:
J/ApJS/207/10 : HST Treasury Program on the ONC (Robberto+, 2013)
J/ApJ/733/50 : MIR phot. monitoring of the ONC (Morales-Calderon+, 2011)
J/A+A/534/A10 : HST/NICMOS imaging in Orion Nebula Cluster (Andersen+, 2011)
J/ApJ/722/1092 : Optical photometry of the ONC. II. (Da Rio+, 2010)
J/A+A/515/A13 : Very low mass objects in ONC (Rodriguez-Ledesma+, 2010)
J/AJ/139/950 : JHKs photometry in ONC (Robberto+, 2010)
J/ApJS/183/261 : Optical photometry of the ONC (Da Rio+, 2009)
J/A+A/502/883 : I photometry of low mass ONC stars (Rodriguez-Ledesma+, 2009)
J/MNRAS/400/603 : New variables in ONC (Parihar+, 2009)
J/ApJ/677/401 : Xray properties of protostars in ONC (Prisinzano+, 2008)
J/ApJ/671/605 : NGC 2264 and ONC PMS stars in the infrared (Cieza+, 2007)
J/ApJ/660/1462 : Abundances of ONC X-ray PMS stars (Maggio+, 2007)
J/AJ/134/2272 : Visual binaries in the Orion Nebula Cluster (Reipurth+, 2007)
J/MNRAS/361/211 : JHK photometry of brown dwarfs in Orion (Lucas+, 2005)
J/AJ/121/1676 : ONC low-mass stars photometry (Rebull+, 2001)
J/ApJ/540/236 : KH photometry of Orion Nebula Cluster (Hillenbrand+, 2000)
J/A+A/337/403 : Low-mass stars evolutionary models (Baraffe+ 1998)
J/AJ/113/1733 : Orion Nebula Cluster population (Hillenbrand 1997)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Seq [1/1743] Source identification number
(<[DRH2012] NNNN> in Simbad)
6- 7 I2 h RAh Hour of Right Ascension (J2000)
9- 10 I2 min RAm Minute of Right Ascension (J2000)
12- 16 F5.2 s RAs Second of Right Ascension (J2000)
18 A1 --- DE- Sign of the Declination (J2000)
19- 20 I2 deg DEd Degree of Declination (J2000)
22- 23 I2 arcmin DEm Arcminute of Declination (J2000)
25- 28 F4.1 arcsec DEs Arcsecond of Declination (J2000)
30- 34 F5.3 [K] logT [3.42/4.26] Log of the effective temperature
36- 40 F5.3 [K] e_logT [0/0.17] Uncertainty in logT
42- 47 F6.3 [Lsun] logL [-4.14/2.74] Log of the bolometric luminosity
49- 53 F5.3 [Lsun] e_logL [0/1.69] Uncertainty in logL
55- 60 F6.3 mag Av [-2/13.1] The V band extinction
62- 67 F6.3 mag e_Av [0.005/11.25] Uncertainty in Av
69 A1 --- u_M1 [~] Approximate flag for M1
70- 74 F5.3 Msun M1 [0/1.4]? Mass using B98 models (1)
76- 80 F5.3 Msun e_M1 [0.001/0.4]? Uncertainty in M1
82 A1 --- l_logA1 Limit flag on logA1
83- 87 F5.3 [yr] logA1 [6/9]? Log age using B98 models (1)
89- 93 F5.3 [yr] e_logA1 [0/0.7]? Uncertainty in logA1
95- 99 F5.3 Msun M2 [0.02/3]? Mass using DM98 models (1)
101-105 F5.3 Msun e_M2 [0/0.46]? Uncertainty in M2
107-111 F5.3 [yr] logA2 [3.63/8.97]? Log age using DM98 models (1)
113-117 F5.3 [yr] e_logA2 [0.002/0.92]? Uncertainty in logA2
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Note (1):
B98 = Baraffe et al. 1998, Cat. J/A+A/337/403
DM98 = D'Antona & Mazzitelli, 1998ASPC..134..442D 1998ASPC..134..442D
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History:
From electronic version of the journal
References:
Da Rio et al. Paper I. 2009ApJS..183..261D 2009ApJS..183..261D Cat. J/ApJS/183/261
Da Rio et al. Paper II. 2010ApJ...722.1092D 2010ApJ...722.1092D Cat. J/ApJ/722/1092
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 08-Oct-2013