J/A+A/630/A136 Starless core L1521E chemical structure (Nagy+, 2019)
The chemical structure of the very young starless core L1521E.
Nagy Z., Spezzano S., Caselli P., Vasyunin A., Tafalla M., Bizzocchi L.,
Prudenzano D., Redaelli E.
<Astron. Astrophys. 630, A136 (2019)>
=2019A&A...630A.136N 2019A&A...630A.136N (SIMBAD/NED BibCode)
ADC_Keywords: Molecular clouds ; Radio lines ; Interstellar medium
Keywords: ISM: molecules - radio lines: ISM - ISM: clouds
Abstract:
We have obtained ∼2.5x2.5 arcminute maps toward L1521E using the
IRAM-30m telescope in transitions of various species, including
C17O, CH3OH c-C3H2, CN, SO, H2CS, and CH3CCH. We derived
abundances for the observed species and compared them to those
obtained toward L1544. We estimated CO depletion factors using the
C17O IRAM-30m map, an N(H2) map derived from Herschel/ SPIRE data
and a 1.2 mm dust continuum emission map obtained with the IRAM-30m
telescope.
Similarly to L1544, c-C3H2 and CH3OH peak at different
positions. Most species peak toward the c-C3H2 peak: C2S, C3S,
HCS+, HC3N, H2CS, CH3CCH, C34S. C17O and SO peak close to
both the c-C3H2 and the CH3OH peaks. CN and N2H+ peak close
to the Herschel dust peak. We found evidence of CO depletion toward
L1521E. The lower limit of the CO depletion factor derived toward the
Herschel dust peak is 4.3±1.6, which is about a factor of three
lower than toward L1544. We derived abundances for several species
toward the dust peaks of L1521E and L1544. The abundances of most
sulfur-bearing molecules such as C2S, HCS+, C34S, C33S, and
HCS+ are higher toward L1521E than toward L1544 by factors of ∼2-20,
compared to the abundance of A-CH3OH. The abundance of methanol is
very similar toward the two cores.
Description:
Integrated emission maps of 66 molecular transitions towards the
starless core L1521E, presented in the paper in Figures 1, 2, and in
Table A.1.
The emission maps towards L1521E have been obtained using the IRAM 30m
telescope (Pico Veleta, Spain). Part of the observations were carried
out in June and August 2016 (PI: S. Spezzano), and additional
observations were done in 2018 January and April (PI: Z. Nagy). We
performed a 2.5'x2.5' on-the-fly (OTF) maps with position switching
centred on RA(J2000)=04:29:15.7 and Dec(J2000)=+26:14:5. The Fourier
transform spectrometer (FTS) was used as the backend with a spectral
resolution of 50kHz. The antenna moved along an orthogonal pattern of
linear paths separated by 8" intervals, corresponding to roughly one
third of the beam FWHM. The data processing was done using the GILDAS
software (Pety 2005) and CASA (McMullin et al. 2007). All the maps
have been gridded to a pixel size of 4" with the CLASS software in the
GILDAS package, this corresponds to 1/5-1/7 of the actual beam size,
depending on the frequency. The integrated intensities have been
calculated in the 5.5-8.0km/s velocity range.
Objects:
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RA (2000) DE Designation(s)
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04 29 13.6 +26 14 19 L1521E = [LM99] L1521E
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 123 74 *Molecules and transitions detected toward L1521E
list.dat 109 66 List of fits maps
fits/* . 66 Individual fits maps
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Note on tablea1.dat: The line parameters are measured toward the Herschel dust
peak using Gaussian fitting. Some of the detections toward L1544 are based on
the spectrum measured in the ∼80-106GHz frequency range toward the dust peak
of L1544 as part of ASAI (Lefloch et al. 2018MNRAS.477.4792L 2018MNRAS.477.4792L;
Vastel et al. 2018MNRAS.478.5514V 2018MNRAS.478.5514V).
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Mol Molecule
12 A1 --- n_Mol [*] Note on Mol (1)
14- 50 A37 --- Trans Transition
52- 59 F8.1 MHz Freq Frequency
61- 67 E7.2 s-1 Aij Transition probability
69- 72 F4.1 K Eup Upper state energy
74- 77 F4.2 K.km/s ITMBdV Measured integrated intensities of the line
79- 82 F4.2 K.km/s e_ITMBdV rms uncertainty on ITMBdV
84- 87 F4.2 km/s VLSR LSR velocity
89- 92 F4.2 km/s e_VLSR rms uncertainty on VLSR
94- 97 F4.2 km/s DV Velocity difference
99-102 F4.2 km/s e_DV ?=- rms uncertainty on DV
103 A1 --- n_DV [b] b for Fixed parameter in the fit
105-108 F4.2 K Tpeak Peak temperature
110-113 F4.2 K 3srms 3σ rms
115-119 E5.2 cm-3 Cdens ?=- Critical density
121-123 A3 --- Det [Yes -] Detected toward L1544 ? (2)
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Note (1): The transitions marked with an asterisk were used to calculate column
densities (Sect. 4.3) and for the principal component analysis (Sect. 4.2).
Note (2): The transitions which are marked with "-" were not covered in the
available dataset for L1544.
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 2 I2 h RAh Right Ascension of center (J2000)
4- 5 I2 min RAm Right Ascension of center (J2000)
7- 12 F6.3 s RAs Right Ascension of center (J2000)
14 A1 --- DE- Declination sign of center (J2000)
15- 16 I2 deg DEd Declination of center (J2000)
18- 19 I2 arcmin DEm Declination of center (J2000)
21- 25 F5.2 arcsec DEs Declination of center (J2000)
27- 28 I2 --- Nx Number of pixels along X-axis
30- 31 I2 --- Ny Number of pixels along Y-axis
33- 34 I2 Kibyte size Size of FITS file
36- 56 A21 --- FileName Name of FITS file, in subdirectory fits
57-109 A53 --- Title Title of the FITS file (1)
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Note (1): the quantum numbers and frequencies of the transitions are reported
in Table A.1 in the paper.
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Acknowledgements:
Zsofia Nagy, znagy(at)mpe.mpg.de
(End) Patricia Vannier [CDS] 12-Aug-2019