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J/AJ/121/2124    λ Ori pre-main-sequence stars photometry  (Dolan+, 2001)

The spatial distribution of the λ Orionis pre-main-sequence population. Dolan C.J., Mathieu R.D. <Astron. J. 121, 2124 (2001)> =2001AJ....121.2124D
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 λ 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 8deg2 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 λ 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:
FileName Lrecl Records Explanations
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 35 20 Massive star derived data table7.dat 48 99 Follow-up data for DIL (Duerr, Imhoff & Lada, 1982ApJ...261..135D) stars
See also : J/AJ/118/2409: VRI photometry of λ 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
Bytes Format Units Label Explanations
1- 2 I2 --- [DM99] [1/72] The λ Ori running number 4- 19 A16 --- JName The λ 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.
Note (1): Interpolated from the Palla & Stahler (1999ApJ...525..772P) stellar evolution models.
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 3 I3 --- [DM99] [73/266] The λ Ori running number 5- 20 A16 --- JName The λ 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 Halpha (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
Note (1): Positive values indicate absorption. Note (2): g = These stars have one EqWidLi above 0.2Å 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.
Byte-by-byte Description of file: table4.dat
Bytes Format Units Label Explanations
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 m1 band magnitude 52- 56 F5.3 mag e_m1 Uncertainty in m1 58- 63 F6.3 mag c1 The c1 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 β 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
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.
Byte-by-byte Description of file: table5.dat
Bytes Format Units Label Explanations
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
Byte-by-byte Description of file: table7.dat
Bytes Format Units Label Explanations
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
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.
History: From electronic version of the journal
(End) Greg Schwarz [AAS] , Patricia Bauer [CDS] 30-Aug-2001
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