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J/AJ/132/1851       Arecibo obs. of formaldehyde in L1551    (Araya+, 2006)

Arecibo observations of formaldehyde in L1551. Araya E., Hofner P., Olmi L., Kurtz S., Linz H. <Astron. J., 132, 1851-1858 (2006)> =2006AJ....132.1851A
ADC_Keywords: Molecular clouds ; Spectroscopy ; Models Keywords: ISM: individual (L1551) - ISM: molecules - radio lines: ISM - stars: formation Abstract: We report observations of the formaldehyde (H2CO) 6cm (4.8GHz) line toward L1551. The observations were conducted with the Arecibo Telescope (beam FWHP∼1') to verify the tentative detection of H2CO thermal emission reported by Duncan and collaborators in 1987MNRAS.224..721D. The H2CO emission lines were expected to be present with a signal-to-noise ratio of ≳10 in our spectra. However, we did not detect H2CO emission; i.e., our data rule out their tentative detection. The absence of H2CO emission is also confirmed by the fact that the H2CO line profiles at the two positions of expected emission are well fitted by a single absorption component (accounting for the hyperfine structure of the line) in one of the positions and by a single absorption line plus a red-wing absorption component in the second position. The Orion BN/KL region remains the only H2CO 6cm thermal emitter known. Our observations also demonstrate that the H2CO 6cm absorption line traces not only the quiescent molecular cloud but also the kinematics associated with the star formation process in L1551-IRS5. Description: The observations were conducted from 2004 December 13 to 19 with the 305m Arecibo Radio Telescope. Objects: ------------------------------------------------------- RA (2000) DE Designation(s) ------------------------------------------------------- 04 31 30.0 +18 12 20 L1551 = LDN 1551 ------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 60 64 Model Results
See also: J/A+A/318/879 : IR photometry of L1551/IRS5 (Men'shchikov+ 1997) J/A+A/420/945 : L1551 ISOCAM observations (Galfalk+, 2004) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 2 I2 arcmin oRA Offset along Right Ascension (1) 4- 5 I2 arcmin oDE Offset along Declination (1) 7- 10 F4.2 K Tex0 Excitation temperature lower limit 12- 15 F4.2 K Tex1 Excitation temperature upper limit 17- 20 F4.2 --- tau0 Optical depth lower limit 22- 25 F4.2 --- tau1 Optical depth upper limit 27- 30 F4.2 km/s DelV0 Line width lower limit 32- 35 F4.2 km/s DelV1 Line width upper limit 37- 40 F4.2 km/s VLSR0 The F=2-2 hyperfine component LSR velocity, lower limit 42- 45 F4.2 km/s VLSR1 The F=2-2 hyperfine component LSR velocity, upper limit 47- 52 F6.2 --- chi2 χ2 value (2) 54- 58 F5.2 --- Dchi2 ? Different χ2 value for DelV and VLSR ranges (3) 60 A1 --- Wing [c] Presence of wings (4)
Note (1): Reference position is 04:31:21.8+18:05:54 (J2000). Note (2): When χ2 values of less than 23.5 were obtained, we explored the convergence of the parameters at fixed χ2 levels, i.e., χ2=4.72, 7.78, 9.70, 13.3, 16.3, and 23.5 levels, which correspond to confidence levels of 68.3%, 90.0%, 95.4%, 99.0%, 99.73%, and 99.99% for a four-degrees-of-freedom χ2 fitting (Press et al., 1999, Numerical Recipes in C (2nd ed.; Cambridge: Cambridge Univ. Press) ). When convergence better than the χ2=23.5 value was not achieved, then arbitrary χ2 levels were used. Note (3): In some cases the DelV and VLSR parameters converge within given χ2 value, whereas the tau and Tex parameters show multiple solutions for the same χ2 contour level. For those cases we report DelV and VLSR ranges for a different χ2 contour level than the one used to obtain the tau and Tex ranges. Note (4): Presence of wings precluded a reliable fit of the complete line profile. See lower panels of Figure 6 as example.
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 23-Jul-2008
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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