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J/AJ/121/2124 {lambda} Ori pre-main-sequence stars photometry (Dolan+, 2001)
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The spatial distribution of the {lambda} Orionis pre-main-sequence population.
Dolan C.J., Mathieu R.D.
<Astron. J. 121, 2124 (2001)>
=2001AJ....121.2124D
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ADC_Keywords: Stars, pre-main sequence ; Photometry, VRI ; Photometry, CCD ;
Photometry, uvby, beta ; Equivalent widths ; Radial velocities
Keywords: stars: formation - stars: pre-main-sequence
Abstract:
The {lambda} Ori star-forming region presents a snapshot of a
moderate-mass giant molecular cloud 1-2Myr after cloud disruption by
OB stars, with the OB stars, the low-mass stellar population, remnant
molecular clouds, and the dispersed gas all still present. We have
used optical photometry and multiobject spectroscopy for lithium
absorption to identify 266 pre-main-sequence stars in 8deg^2^ of the
region. We also present new Stroemgren photometry for the massive
stars, from which we derive a distance of 450pc and a turnoff age of
6-7Myr. Using these parameters and pre-main-sequence evolutionary
models, we map the star formation history of the low-mass stars. We
find that low-mass star formation started throughout the region at
about the same time as the birth of the massive stars, and thereafter
the birth rate accelerated. Within the last 1-2Myr star formation
ceased in the center of the star-forming region, near the
concentration of OB stars, while it continues in dark clouds 20pc
away. We suggest that a supernova 1-2Myr ago destroyed the molecular
cloud core from which the OB stars formed, but it did not terminate
star formation in more distant reaches of the giant molecular cloud.
We find no secure evidence for triggered or sequential star formation
in the outer molecular clouds. The global star formation of the
{lambda} Ori region has generated the field initial mass function, but
local star formation in subregions shows large deviations from the
expected ratio of high- to low-mass stars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 72 72 Improved data for Paper I (Dolan & Mathieu,
1999, Cat. <J/AJ/118/2409>) stars
table2.dat 106 204 Pre-main-sequence stellar data
table4.dat 88 20 Massive star photometry
table5.dat 33 20 Massive star derived data
table7.dat 48 99 Follow-up data for DIL (Duerr, Imhoff & Lada,
1982ApJ...261..135D) stars
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See also :
J/AJ/118/2409: VRI photometry of {lambda} Ori PMS stars. I. (Dolan+, 1999)
I/252 : The USNO-A2.0 Catalogue (Monet+ 1998)
I/146 : Positions and Proper Motions - North (Roeser+, 1988)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- [DM99] [1/72] The {lambda} Ori running number
4- 19 A16 --- JName The {lambda} Ori designation
21- 22 I2 h RAh Right Ascension from USNO-A 2.0 catalog (J2000)
24- 25 I2 min RAm Right Ascension from USNO-A 2.0 catalog (J2000)
27- 32 F6.3 s RAs Right Ascension from USNO-A 2.0 catalog (J2000)
33 A1 --- DE- Declination sign (J2000)
34- 35 I2 deg DEd Declination from USNO-A 2.0 catalog (J2000)
37- 38 I2 arcmin DEm Declination from USNO-A 2.0 catalog (J2000)
40- 44 F5.2 arcsec DEs Declination from USNO-A 2.0 catalog (J2000)
46- 50 F5.2 mag Vmag The V band magnitude
52- 55 F4.2 mag V-R The (V-R) color
57- 60 F4.2 mag R-I The (R-I) color
62- 65 F4.2 [yr] LogAge Log of the Age (1)
67- 70 F4.2 solMass Mass Mass (1)
72 A1 --- f_[DM99] [b] Indicates star does not exist in the
USNO-A2.0 database. The coordinates (A1.0) and
magnitudes listed are from Paper I,
Dolan & Mathieu, 1999AJ....118.2409D.
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Note (1): Interpolated from the Palla & Stahler (1999ApJ...525..772P) stellar
evolution models.
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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- 3 I3 --- [DM99] [73/266] The {lambda} Ori running number
5- 20 A16 --- JName The {lambda} Ori designation
22- 23 I2 h RAh Right Ascension from USNO-A 2.0 catalog (J2000)
25- 26 I2 min RAm Right Ascension from USNO-A 2.0 catalog (J2000)
28- 33 F6.3 s RAs Right Ascension from USNO-A 2.0 catalog (J2000)
34 A1 --- DE- Declination sign (J2000)
35- 36 I2 deg DEd Declination from USNO-A 2.0 catalog (J2000)
38- 39 I2 arcmin DEm Declination from USNO-A 2.0 catalog (J2000)
41- 45 F5.2 arcsec DEs Declination from USNO-A 2.0 catalog (J2000)
47- 51 F5.2 mag Vmag The V band magnitude
53 A1 --- f_Vmag [c] Indicates photometry from the
lower-quality 1998 data
55- 58 F4.2 mag V-R The (V-R) color
60 A1 --- f_V-R [c] Indicates photometry from the
lower-quality 1998 data
62- 65 F4.2 mag R-I The (R-I) color
67 A1 --- f_R-I [c] Indicates photometry from the
lower-quality 1998 data
69- 72 F4.2 0.1nm EqWidLi ? Equivalent width of Li (1)
74 A1 --- f_EqWidLi [gh] Flag on EqWidLi (2)
76- 81 F6.2 0.1nm EqWidHa ? Equivalent width of H{alpha} (3)
83 A1 --- f_EqWidHa [d] Indicates star shows a strong
P Cygni profile
85- 90 F6.2 km/s RVel Stellar radial velocity
92 A1 --- f_RVel [fij] Flag on RVel (4)
94- 97 F4.2 [yr] LogAge Log of the Age (5)
99-102 F4.2 solMass Mass Mass (5)
104 A1 --- f_Mass [e] Indicates star is outside the age/mass grid
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Note (1): Positive values indicate absorption.
Note (2):
g = These stars have one EqWidLi above 0.2{AA} and one below.
h = EqWidLi measured from the combined light of both components.
Note (3): Positive values indicate emission.
Note (4):
f = Double-lined spectrum.
i = Two observations of a blended double-line spectrum. The first pair are
JD2451235.67 while the second pair are two days later (JD2451237.68).
j = The first pair are from a blended double-line spectrum (JD2451564.82).
A second spectrum about three weeks later (JD2451586.65) was not
resolvable as two spectra.
Note (5): Interpolated from the Palla & Stahler (1999ApJ...525..772P)
stellar evolution models.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- HD The HD (Cat. <III/135>) number
8- 13 I6 --- PPM ? The Positions & Proper Motions Catalog
(Cat. <I/146>) number
15- 16 A2 --- SpType Spectral type (1)
18 A1 --- f_SpType [b] Flag on SpType (2)
20- 24 F5.3 mag Vmag The V band magnitude
26- 30 F5.3 mag e_Vmag Uncertainty in Vmag
32- 37 F6.3 mag b-y The (b-y) Stroemgren color
39- 43 F5.3 mag e_b-y Uncertainty in (b-y)
45- 50 F6.3 mag m1 The m_1_ band magnitude
52- 56 F5.3 mag e_m1 Uncertainty in m1
58- 63 F6.3 mag c1 The c_1_ band magnitude
65- 69 F5.3 mag e_c1 Uncertainty in c1
71 I1 --- o_b-y Number of Stroemgren uvby observations
73- 77 F5.3 mag beta The {beta} band magnitude
79- 83 F5.3 mag e_beta Uncertainty in beta
85 I1 --- o_beta Number of beta observations
87 I1 --- r_HD Reference on HD
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Note (1): Spectral types are reported from the PPM catalog, except for
HD 245185 which is from the HD catalog.
Note (2): Terranegra et al. (1994, Cat. <J/A+AS/104/557>) find a photometric
spectral type of B9.5III-V for this Herbig Ae-Be star.
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- HD The HD (Cat. <III/135>) number
8- 11 F4.2 mag E(B-V) The E(B-V) reddening
13- 16 F4.2 [K] Teff Log of the effective temperature
18- 21 F4.2 [solLum] Lum Log of the luminosity in solar units
23- 26 F4.1 [solMass] Mass Log of the mass in solar units
28- 30 I3 pc Dist ? Distance
32- 35 I4 % e_Dist ? The parallax fractional error
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Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- DIL The Duerr, Imhoff & Lada (1982ApJ...261..135D)
survey number
4- 16 A13 --- USNO-A2.0 The USNO A2.0 identification
18 A1 --- f_USNO-A2.0 [abcde] Flag on USNO-A2.0 (1)
20- 21 I2 h RAh Right Ascension (J2000)
23- 24 I2 min RAm Right Ascension (J2000)
26- 31 F6.3 s RAs Right Ascension (J2000)
32 A1 --- DE- Declination sign (J2000)
33- 34 I2 deg DEd Declination (J2000)
36- 37 I2 arcmin DEm Declination (J2000)
39- 43 F5.2 arcsec DEs Declination (J2000)
45- 47 I3 --- [DM99] ? This paper's identification number
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Note (1):
a = DIL 27 appears to be part of a very close pair. We have indicated the
likely match, but the other is at 05:31:24.660 12:12:09.71.
b = DIL 42 is not marked on the DIL finding charts. We found the star in
Haro, Iriarte & Chavira (1953BOTT....1h...3H), but there are too few
stars visible in their finding chart to be absolutely sure this is the
right one.
c = DIL 49 and 50 have reversed names in the DIL catalog. DIL 49 should
be ``H 6-70'' while DIL 50 should be ``H 6-69''. Column 8 of the DIL
catalog should be reversed for these stars as well.
d = DIL 70 is unclearly marked on both the DIL and Manova
(1959SvA.....3..188M) finding charts.
We have indicated the likely match, but another possibility is at
05:41:29.597 09:07:11.21.
e = DIL 80 is unclearly marked on both the DIL and Manova finding charts.
We have indicated the likely match, but another possibility is at
05:43:57.008 09:16:25.65.
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History:
From electronic version of the journal
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(End) Greg Schwarz [AAS] , Patricia Bauer [CDS] 30-Aug-2001