J/ApJ/757/141 Companion IR detection limits in young associations (Kraus+, 2012)
Multiple star formation to the bottom of the initial mass function.
Kraus A.L., Hillenbrand L.A.
<Astrophys. J., 757, 141 (2012)>
=2012ApJ...757..141K 2012ApJ...757..141K
ADC_Keywords: Stars, masses ; Stars, double and multiple ; Photometry, infrared
Keywords: binaries: visual; brown dwarfs; stars: low-mass;
stars: pre-main sequence
Abstract:
The frequency and properties of multiple star systems offer powerful
tests of star formation models. Multiplicity surveys over the past
decade have shown that binary properties vary strongly with mass, but
the functional forms and the interplay between frequency and semimajor
axis remain largely unconstrained. We present the results of a
large-scale survey of multiplicity at the bottom of the initial mass
function in several nearby young associations, encompassing 78 very
low mass members observed with Keck laser guide star adaptive optics.
Our survey confirms the overall trend observed in the field for
lower-mass binary systems to be less frequent and more compact,
including a null detection for any substellar binary systems with
separations wider than ∼7AU. Combined with a Bayesian re-analysis of
existing surveys, our results demonstrate that the binary frequency
and binary separations decline smoothly between masses of 0.5M☉
and 0.02M☉, though we cannot distinguish the functional form of
this decline due to a degeneracy between the total binary frequency
and the mean binary separation. We also show that the mass ratio
distribution becomes progressively more concentrated at q∼1 for
declining masses, though a small number of systems appear to have
unusually wide separations and low-mass ratios for their mass.
Finally, we compare our results to synthetic binary populations
generated by smoothed particle hydrodynamic simulations, noting the
similarities and discussing possible explanations for the differences.
Description:
Most of the data that we summarize were obtained in four observing
runs, totaling 10 nights, between 2005 December and 2007 March. One
source was observed during a time trade in 2006 December. Most of our
observations were obtained using laser guide star adaptive optics
(LGSAO) on the Keck-II telescope with NIRC2, a high spatial resolution
near-infrared camera.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 88 81 Observed sample
table2.dat 50 92 Observations
table3.dat 78 66 Candidate companions to young stars and brown dwarfs
table4.dat 109 97 Companion detection limits
table7.dat 159 512 Companion detection limits from previous surveys
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See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/MNRAS/431/3222 : UKIDSS GCS Upper Sco members (Lodieu, 2013)
J/MNRAS/418/1231 : New brown dwarfs in upper Sco (Dawson+, 2011)
J/ApJS/196/4 : New young star candidates in Taurus-Auriga (Rebull+, 2011)
J/ApJ/731/8 : Multiple star formation in Taurus-Auriga (Kraus+, 2011)
J/AJ/139/1338 : UV-selected stars in Tau and Upper Sco (Findeisen+, 2010)
J/ApJ/704/531 : The coevality of young binary systems (Kraus+, 2009)
J/ApJ/703/1511 : Wide binaries in Taurus and Upper Sco (Kraus+, 2009)
J/ApJ/688/377 : Low-mass objects in Upper Scorpius. II. (Slesnick+, 2008)
J/ApJ/662/413 : 2MASS survey of multiplicity in 3 associations (Kraus+, 2007)
J/MNRAS/374/372 : ZYJHK photometry in Upper Sco (Lodieu+, 2007)
J/MNRAS/373/95 : ZYJHK survey of Upper Sco association (Lodieu+, 2006)
J/ApJ/651/L49 : Upper Sco OB association IRAC observations (Carpenter+, 2006)
J/ApJ/647/1180 : Infrared photometry of Taurus SFR (Luhman+, 2006)
J/ApJ/645/676 : Spatial distribution of brown dwarfs in Taurus (Luhman+, 2006)
J/A+A/446/485 : New very low-mass members in Taurus (Guieu+, 2006)
J/AJ/132/2665 : QUEST2 BRI photometry of Taurus-Auriga PMS (Slesnick+, 2006)
J/AJ/131/3016 : Low-mass objects in Upper Scorpius (Slesnick+, 2006)
J/A+A/416/555 : Brown Dwarfs in ChaI Dark Cloud (Lopez-Marti+ 2004)
J/ApJ/602/816 : Chamaeleon I star-forming region census (Luhman, 2004)
J/AJ/126/1526 : IR photometry of ultracool dwarfs (Bouy+, 2003)
J/AJ/124/404 : USco OB association Lithium survey. II. (Preibisch, 2002)
J/A+A/356/541 : T Tauri stars in the Sco-Cen OB association (Koehler+, 2000)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 A9 --- Region Region identifier (Taurus or Upper Sco)
11- 34 A24 --- Name Target identifier
36- 37 I2 h RAh Hour of right ascension (J2000)
39- 40 I2 min RAm Minute of right ascension (J2000)
42- 46 F5.2 s RAs Second of right ascension (J2000) (1)
48 A1 --- DE- Sign of declination (J2000)
49- 50 I2 deg DEd Degree of declination (J2000)
52- 53 I2 arcmin DEm Arcminute of declination (J2000)
55- 58 F4.1 arcsec DEs Arcsecond of declination (J2000)
60- 64 A5 --- SpT MK spectral type
66- 70 F5.3 Msun Mass [0.01/0.6]? Mass
72- 76 F5.2 mag Kmag [7.6/14.5] 2MASS K-band magnitude
78- 81 F4.1 mag Rmag [10/19] USNO-B1 R-band magnitude (RTT)
83- 86 F4.1 arcsec dTT [0/54]?=0 USNO-B1 distance to each star's
tip-tilt (dTT)
88 I1 --- Ref [1/3]? Reference (2)
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Note (1): The right ascension for SCH J16095307-19481704 has been corrected
at CDS ("16 09 53.07" vs "16 09 63.07" given in the paper).
Note (2): The properties of our sample members are summarized in our previous
compilation, Kraus & Hillenbrand (2007, J/ApJ/662/413). References for
sources observed in previous multiplicity surveys as follows:
1 = Kraus et al. 2006ApJ...649..306K 2006ApJ...649..306K
2 = Konopacky et al. 2007ApJ...663..394K 2007ApJ...663..394K
3 = Kraus et al. 2005ApJ...633..452K 2005ApJ...633..452K
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 24 A24 --- Name Target identifier
26 A1 --- f_Name [a] a: Observation also includes
2M04554801+3028050 in the same field
28- 31 I4 d Epoch Julian date; JD-2450000
33 A1 --- Mode Observation mode
35- 37 I3 s Tint [30/850] Integration time
39- 44 A6 mas FWHM Typical point-spread function (PSF) FWHM
46- 50 A5 % FElon Fractional elongation
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- Region Region identifier (Tau or USco)
6- 29 A24 --- Name Target identifier (3)
31- 34 A4 --- Comp Companion identification (1)
36 A1 --- r_Comp Previously identified as candidate
companion reference (2)
38- 41 I4 d Epoch Julian Date; JD-2450000
43- 44 I2 --- N [1/34] Number of measures
46- 49 I4 mas Sep [48/8878] Companion separation
51- 52 I2 mas e_Sep [1/25] Sep uncertainty
54- 60 F7.3 deg PA [0.2/351] Companion position angle
62- 66 F5.3 deg e_PA [0.002/1.7] PA uncertainty
68- 72 F5.3 mag DK' [0/8] The ΔK' flux ratio
74- 78 F5.3 mag e_DK' [0.003/0.2] DK' uncertainty
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Note (1): We label a companion as "B" if it falls in the range of parameter
space where background stars are statistically unlikely to have been
found (K<14, ρ<3", Section 4.2), and otherwise label them as "c#"
to reflect that they are unconfirmed candidate companions. For wide
pairs, we refer to a specific component as "A" or "B," and then refer
to the newly identified (closer) companion to that component as "b" or
"c1" following the same rules.
Note (2): Reference as follows:
g = Ghez et al. (1993AJ....106.2005G 1993AJ....106.2005G),
l = Luhman (2004, Cat. J/ApJ/602/816),
k = Kraus et al. (2005ApJ...633..452K 2005ApJ...633..452K),
m = Kraus et al. (2006ApJ...649..306K 2006ApJ...649..306K),
n = Konopacky et al. (2007ApJ...663..394K 2007ApJ...663..394K),
o = Kraus & Hillenbrand (2007, Cat. J/ApJ/662/413),
p = Kraus et al. (2011, Cat. J/ApJ/731/8).
Note (3): name corrected at CDS:
SCH J0359099+2009362 (was originally SCH J0359099+2009363)
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Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 A9 --- Region Region identifier (Taurus or Upper Sco)
11- 34 A24 --- Name Target identifier
36- 39 F4.2 mag DK40 ? The ΔK' flux ratio at 40mas separation
41- 44 F4.2 mag DK45 ? The ΔK' flux ratio at 45mas separation
46- 49 F4.2 mag DK50 ? The ΔK' flux ratio at 50mas separation
51- 54 F4.2 mag DK60 ? The ΔK' flux ratio at 60mas separation
56- 59 F4.2 mag DK80 ? The ΔK' flux ratio at 80mas separation
61- 64 F4.2 mag DK100 ? The ΔK' flux ratio at 100mas separation
66- 69 F4.2 mag DK120 ? The ΔK' flux ratio at 120mas separation
71- 74 F4.2 mag DK150 ? The ΔK' flux ratio at 150mas separation
76- 79 F4.2 mag DK200 ? The ΔK' flux ratio at 200mas separation
81- 84 F4.2 mag DK300 ? The ΔK' flux ratio at 300mas separation
86- 89 F4.2 mag DK400 The ΔK' flux ratio at 400mas separation
91- 94 F4.2 mag DK500 The ΔK' flux ratio at 500mas separation
96- 99 F4.2 mag DK750 The ΔK' flux ratio at 750mas separation
101-104 F4.2 mag DK1000 The ΔK' flux ratio at 1arcsec separation
106-109 F4.2 mag DK2000 The ΔK' flux ratio at 2arcsec separation
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Byte-by-byte Description of file: table7.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 A9 --- Region Region identifier (Cha-I, Taurus or Upper Sco)
11- 37 A27 --- Name Target identifier
39- 40 I2 h RAh Hour of Right Ascension (J2000)
42- 43 I2 min RAm Minute of Right Ascension (J2000)
45- 49 F5.2 s RAs Second of Right Ascension (J2000)
51 A1 --- DE- Sign of the Declination (J2000)
52- 53 I2 deg DEd Degree of Declination (J2000)
55- 56 I2 arcmin DEm Arcminute of Declination (J2000)
58- 62 F5.2 arcsec DEs Arcsecond of Declination (J2000)
64- 68 F5.3 Msun Mass [0.01/0.5] Primary star's mass
70- 73 F4.2 --- q0.5 ? Mass ratio at log(ρ)=0.5 (1)
75- 78 F4.2 --- q0.6 ? Mass ratio at log(ρ)=0.6 (1)
80- 83 F4.2 --- q0.7 ? Mass ratio at log(ρ)=0.7 (1)
85- 88 F4.2 --- q0.8 ? Mass ratio at log(ρ)=0.8 (1)
90- 93 F4.2 --- q0.9 ? Mass ratio at log(ρ)=0.9 (1)
95- 98 F4.2 --- q1.0 ? Mass ratio at log(ρ)=1.0 (1)
100-103 F4.2 --- q1.1 ? Mass ratio at log(ρ)=1.1 (1)
105-108 F4.2 --- q1.2 ? Mass ratio at log(ρ)=1.2 (1)
110-113 F4.2 --- q1.3 ? Mass ratio at log(ρ)=1.3 (1)
115-118 F4.2 --- q1.4 ? Mass ratio at log(ρ)=1.4 (1)
120-123 F4.2 --- q1.6 ? Mass ratio at log(ρ)=1.6 (1)
125-128 F4.2 --- q1.8 ? Mass ratio at log(ρ)=1.8 (1)
130-133 F4.2 --- q2.1 ? Mass ratio at log(ρ)=2.1 (1)
135-138 F4.2 --- q2.4 ? Mass ratio at log(ρ)=2.4 (1)
140-143 F4.2 --- q2.7 ? Mass ratio at log(ρ)=2.7 (1)
145-148 F4.2 --- q3.0 ? Mass ratio at log(ρ)=3.0 (1)
150-154 F5.2 --- q3.6 ? Mass ratio at log(ρ)=3.6 (1)
156-159 A4 --- Ref Reference(s) (2)
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Note (1): The mass ratio is defined as Msec/Mpri, and the distance
ρ is in AU.
Note (2): The properties of most targets, including the spectral types used
to estimate their masses, are summarized in our previous compilation,
Kraus & Hillenbrand (2007, Cat. J/ApJ/662/413). Properties for the
Upper Sco members discovered by Lodieu et al. (2008MNRAS.383.1385L 2008MNRAS.383.1385L)
are listed in that work.
References for past high-resolution imaging observations as follows:
1 = Lafreniere et al. 2008ApJ...683..844L 2008ApJ...683..844L
2 = this work;
3 = Kraus & Hillenbrand 2007, Cat. J/ApJ/662/413
4 = Kraus & Hillenbrand 2009, Cat. J/ApJ/703/1511
5 = Ghez et al. 1993AJ....106.2005G 1993AJ....106.2005G
6 = Biller et al. 2011ApJ...730...39B 2011ApJ...730...39B
7 = Kraus et al. 2006ApJ...649..306K 2006ApJ...649..306K
8 = Konopacky et al. 2007ApJ...663..394K 2007ApJ...663..394K
9 = Sartoretti et al. 1998A&A...334..592S 1998A&A...334..592S
10 = Simon et al. 1995ApJ...443..625S 1995ApJ...443..625S
11 = Duchene et al. 2007A&A...476..229D 2007A&A...476..229D
12 = Kohler et al. 2000, Cat. J/A+A/356/541
13 = Kraus et al. 2005ApJ...633..452K 2005ApJ...633..452K
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 16-Jun-2014