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J/ApJ/526/788  Survey of infall motions toward starless cores (Lee+, 1999)

A survey of infall motions toward starless cores. I. CS (2-1) and N2H+ (1-0) observations Lee C.W., Myers P.C., Tafalla M. <Astrophys. J. 526, 788 (1999)> =1999ApJ...526..788L
ADC_Keywords: Interstellar medium ; Radio sources ; Molecular clouds Keywords: ISM: globules - ISM: kinematics and dynamics - ISM: molecules - stars: formation Abstract: We present the first results of a survey of 220 starless cores selected primarily by their optical obscuration and observed in CS (2-1), N2H+ (1-0), and C18O (1-0) using the Northeast Radio Observatory Corporation (NEROC) Haystack 37 m telescope. We have detected 163 out of 196 sources observed in CS, 72 out of 142 in N2H+, and 30 out of 30 in C18O. In total, 69 sources were detected in both CS and N2H+. The isolated component of the N2H+ (1-0) spectrum (F1F = 0,1-1,2) usually shows a weak symmetric profile that is optically thin. In contrast, a significant fraction of the CS spectra show non-Gaussian shapes, which we interpret as arising from a combination of self-absorption due to lower excitation gas in the core front and kinematics in the core. The distribution of the normalized velocity difference (δVCS) between the CS and N2H+ peaks appears significantly skewed to the blue (VCS < 0), as was found in a similar study of dense cores with embedded young stellar objects (YSOs). The incidence of sources with blue asymmetry tends to increase as the total optical depth or the integrated intensity of the N2H+ line increases. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 78 151 Starless Cores Observed in CS, N2H+, and C18O table2.dat 116 69 Parameters of starless cores observed in both CS and N2H+
See also: J/A+A/288/601 : Dense molecular cores (Zinchenko+ 1994) J/A+AS/111/95 : Studies of dense molecular cores (Zinchenko+, 1995) J/A+AS/118/191 : Multitransition CS-study towards H2O masers (Juvela, 1996) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 10 A10 --- Name Source name 12 A1 --- f_RAh [cd] Indicates source position obtained elsewhere (1) 15- 16 I2 h RAh Right Ascension (B1950) from Lee+ (1999ApJS..123..233L) 18- 19 I2 min RAm Right Ascension (B1950) from Lee+ (1999) 21- 24 F4.1 s RAs Right Ascension (B1950) from Lee+ (1999) 27 A1 --- DE- Declination (B1950) from Lee+ (1999) 28- 29 I2 deg DEd Declination (B1950) from Lee+ (1999) 31- 32 I2 arcmin DEm Declination (B1950) from Lee+ (1999) 34- 35 I2 arcsec DEs Declination (B1950) from Lee+ (1999) 37- 41 F5.2 km/s VCS ? Velocity of CS 43- 44 A2 --- f_VCS [ND] Indicates object was not detected in CS 46- 49 F4.2 km/s e_VCS ? Error in VCS 51- 55 F5.2 km/s VN2H ? Velocity of N2H 57- 58 A2 --- f_VN2H [ND] Indicates object was not detected in N2H+ 60- 64 F5.3 km/s e_VN2H ? Error in VN2H 65- 69 F5.2 km/s VC18O ? Velocity of C18O 75- 78 F4.2 km/s e_VC18O ? Error in VC18O
Note (1): c = Source position from Benson & Myers (1989ApJS...71...89B) d = Source position from the FCRAO map (C. W. Lee, P. C. Myers, & M. Tafalla, in preparation)
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 10 A10 --- Name Source name 12 A1 --- f_RAh [fg] Indicates source position obtained elsewhere (1) 14- 15 I2 h RAh Right Ascension (B1950) from Lee+ (1999ApJS..123..233L) 17- 18 I2 min RAm Right Ascension (B1950) from Lee+ (1999) 20- 23 F4.1 s RAs Right Ascension (B1950) from Lee+ (1999) 25 A1 --- DE- Declination (B1950) from Lee+ (1999) 26- 27 I2 deg DEd Declination (B1950) from Lee+ (1999) 29- 30 I2 arcmin DEm Declination (B1950) from Lee+ (1999) 32- 33 I2 arcsec DEs Declination (B1950) from Lee+ (1999) 36- 40 F5.2 km/s VCS ? Velocity of CS 43- 46 F4.2 km/s e_VCS ? 1σ error in VCS 49- 53 F5.2 km/s VN2H ? Velocity of N2H 56- 59 F4.2 km/s e_VN2H ? 1σ error in VN2H 62- 66 F5.2 km/s VC18O ? Velocity of C18O 69- 72 F4.2 km/s e_VC18O ? 1σ error in VC18O 75- 79 F5.2 km/s FWHM ? FWHM of N2H 82- 85 F4.2 km/s e_FWHM ? 1σ error in FWHM 89- 92 F4.1 km/s Tau ? Optical depth of N2H 96- 99 F4.1 km/s e_Tau ? 1σ error in Tau 101 A1 --- f_Tau [e] Indicates values are difficult to ensure because S/N < 5 103-107 F5.2 km/s DCS ? Normalized velocity difference of CS (2) 110-113 F4.2 km/s e_DCS ? 1σ error in DCS 115 A1 --- n_DCS [h] Note on DCS (3)
Note (1): f = Source position from Benson & Myers (1989ApJS...71...89B) g = Source position from the FCRAO map (C. W. Lee, P. C. Myers, & M. Tafalla, in preparation) Note (2): The normalized velocity difference, VCS, is defined as VCS = (VCS - VN2H+)/FWHMN2H+^_ Note (3): These two sources (L1544 and L429-1) have an intensity ratio of the blue to the red peak in CS spectra close to 1.0 within error. The CS peak velocities for these two were obtained by the Gaussian fit after masking a fainter peak between two components, although the difference between two is less than 1σ. We do not use these CS optical depth values in our statistics.
History: From ApJ electronic edition
(End) Greg Schwarz [AAS] 16-Mar-2000
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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