J/ApJ/764/114 BVRI photometry of stars in Orion A (Hsu+, 2013)
Evidence for environmental dependence of the upper stellar initial mass
function in Orion A.
Hsu W.-H., Hartmann L., Allen L., Hernandez J., Megeath S.T., Tobin J.J.,
Ingleby L.
<Astrophys. J., 764, 114 (2013)>
=2013ApJ...764..114H 2013ApJ...764..114H
ADC_Keywords: Photometry, UBVRI ; Photometry, infrared ; Radial velocities ;
Spectral types ; YSOs
Keywords: stars: formation; stars: luminosity function, mass function;
stars: pre-main sequence; surveys
Abstract:
We extend our previous study of the stellar population of L1641, the
lower-density star-forming region of the Orion A cloud south of the
dense Orion Nebula Cluster (ONC), with the goal of testing whether
there is a statistically significant deficiency of high-mass stars in
low-density regions. Previously, we compared the observed ratio of
low-mass stars to high-mass stars with theoretical models of the
stellar initial mass function (IMF) to infer a deficiency of the
highest-mass stars in L1641. We expand our population study to
identify the intermediate-mass (late B to G) L1641 members in an
attempt to make a more direct comparison with the mass function of the
nearby ONC. The spectral-type distribution and the K-band luminosity
function of L1641 are similar to those of the ONC, but problems of
incompleteness and contamination prevent us from making a detailed
test for differences. We limit our analysis to statistical tests of
the ratio of high-mass to low-mass stars, which indicate a probability
of only 3% that the ONC and the southern region of L1641 were drawn
from the same population, supporting the hypothesis that the
upper-mass end of the IMF is dependent on environmental density.
Description:
We obtained optical spectroscopy of selected objects with Ohio State
Multi-Object Spectrograph (OSMOS) on the MDM 2.4m. The observations
were taken in a spectral range of 3100-5950Å with a spectral
resolution of R∼1400.
We used OSMOS in photometric mode to obtain BVRIc band photometry in
the Johnson-Cousin system. The photometry observations were all done
on the night of 2012 January 1-2.
To better distinguish foreground F & G stars from members, we observed
20 of the F & G stars with MIKE, the Magellan Inamori Kyocera Echelle
on the Magellan Clay telescope on 2012 February 4 and 5.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 85 57 Intermediate-mass members of L1641
table2.dat 89 79 Non-members of L1641 observed with OSMOS
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See also:
I/322 : UCAC4 Catalogue (Zacharias+, 2012)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/A+A/564/A29 : Optical and near-infrared photometry in Orion A (Bouy+, 2014)
J/ApJS/208/28 : Hα survey in the ONC (Szegedi-Elek+, 2013)
J/ApJS/207/10 : HST Treasury Program on the ONC (Robberto+, 2013)
J/AJ/146/85 : Spectral types of optical stars in ONC (Hillenbrand+, 2013)
J/ApJ/755/154 : Mass accretion rates from HST in the ONC (Manara+, 2012)
J/ApJ/752/59 : Paper I: Low-mass population in L1641 (Hsu+, 2012)
J/AJ/144/192 : Spitzer survey of Orion A and B. I. YSO cat. (Megeath+, 2012)
J/AJ/144/31 : Spitzer+2MASS photometry of protostar cand. (Kryukova+, 2012)
J/AJ/142/60 : Palomar Transient Factory Orion Project (Van Eyken+, 2011)
J/ApJ/733/50 : MIR phot. monitoring of the ONC (Morales-Calderon+, 2011)
J/ApJ/722/1092 : Optical photometry of the ONC. II. (Da Rio+, 2010)
J/A+A/504/461 : YSOs in L1630N and L1641 (Fang+, 2009)
J/ApJS/184/18 : Spitzer survey of young stellar clusters (Gutermuth+, 2009)
J/AJ/121/1676 : ONC low-mass stars photometry (Rebull+, 2001)
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: table[12].dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Seq Running sequence number
4- 11 F8.5 deg RAdeg Right Ascension in decimal degrees (J2000)
13- 20 F8.5 deg DEdeg Declination in decimal degrees (J2000)
22- 26 F5.2 mag Bmag [4.5/16.7]? The Johnson B band magnitude
28- 32 F5.2 mag Vmag ? The Johnson V band magnitude
34- 38 F5.2 mag Rmag ? The Cousins R band magnitude
40- 44 F5.2 mag Imag [8.4/12.5]? The Cousins Ic band magnitude
46- 50 F5.2 mag Jmag 2MASS J band magnitude
52- 56 F5.2 mag Hmag 2MASS H band magnitude
58- 62 F5.2 mag Ksmag [3.2/10.4] 2MASS Ks band magnitude
64- 67 A4 --- SpT MK spectral type
69- 71 F3.1 --- e_SpT ? Uncertainty in SpType
73 A1 --- IRex [NY] IR excess? (1)
75- 79 F5.1 km/s RVel [-18.5/138]? Radial velocity from Magellan/MIKE
echelle data
81- 83 F3.1 0.1nm W(Li) [0/0.2]? Equivalent width of Li; in Angstroms
from Magellan/MIKE echelle data
85- 89 A5 --- n_Seq Note(s) on Seq (2)
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Note (1): Criteria for IR excess are defined in Gutermuth et al. (2009,
Cat. J/ApJS/184/18) and Megeath et al. (2012, Cat J/AJ/144/192).
Note (2): Note as follows:
d = Rejected based on radial velocity incompatible with the velocity
of the cloud.
e = Rejected based on lack of Lithium absorption.
f = Rejected based on large proper motion.
g = Rejected based on position on the color-magnitude diagram.
h = Herbig Ae star V380 Ori.
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History:
From electronic version of the journal
References:
Hsu et al. Paper I. 2012ApJ...752...59H 2012ApJ...752...59H Cat. J/ApJ/752/59
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 27-Oct-2014