J/A+A/643/A60 Starless cores CH3OH and c-C3H2 maps (Spezzano+, 2020)
Distribution of methanol and cyclopropenylidene around starless cores.
Spezzano S., Caselli P., Pineda J.E., Bizzocchi L., Prudenzano D., Nagy Z.
<Astron. Astrophys. 643, A60 (2020)>
=2020A&A...643A..60S 2020A&A...643A..60S (SIMBAD/NED BibCode)
ADC_Keywords: Molecular clouds ; Radio lines
Keywords: astrochemistry - line: identification - ISM: molecules
Abstract:
The spatial distribution of molecules around starless cores is a
powerful tool for studying the physics and chemistry governing the
earliest stages of star formation.
Our aim is to study the chemical differentiation in starless cores to
determine the influence of large-scale effects on the spatial
distribution of molecules within the cores. Furthermore, we want to
put observational constraints on the mechanisms responsible in
starless cores for the desorption of methanol from the surface of dust
grains where it is efficiently produced.
We mapped methanol, CH3OH, and cyclopropenylidene, c-C3H2, with
the IRAM 30m telescope in the 3mm band towards six starless cores
embedded in different environments, and in different evolutionary
stages. Furthermore, we searched for correlations among physical
properties of the cores and the methanol distribution.
From our maps we can infer that the chemical segregation between
CH3OH and c-C3H2 is driven by uneven illumination from the
interstellar radiation field (ISRF). The side of the core that is more
illuminated has more C atoms in the gas-phase and the formation of
carbon-chain molecules like c-C3H2 is enhanced. Instead, on the side
that is less exposed to the ISRF the C atoms are mostly locked in
carbon monoxide, CO, the precursor of methanol.
We conclude that large-scale effects have a direct impact on the
chemical segregation that we can observe at core scale. However, the
non-thermal mechanisms responsible for the desorption of methanol in
starless cores do not show any dependency on the H2 column density
at the methanol peak.
Description:
The maps presented in this paper, shown in Figures 1 and A.1, were
observed using the Eight MIxer Receiver (EMIR) E090 instrument of the
IRAM 30m telescope (Pico Veleta) in on-the-fly mode with position
switching.
The large-scale maps presented in this paper were downloaded from the
ESA Herschel Science Archive. We computed the total column density of
H2, N(H2), and the dust temperature, Tdust, using the three Spectral
and Photometric Imaging Receiver (SPIRE) bands at 250um, 350um, and
500um, for which the pipeline reduction includes zero-level
corrections based on comparison with the Planck satellite data
(Griffin et al., 2010A&A...518L...3G 2010A&A...518L...3G)
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 62 6 Sources
list.dat 115 35 List of fits maps
fits/* . 35 Individual fits maps
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- Name Name
8- 10 A3 --- n_Name Note on Name (1)
13- 14 I2 h RAh Right Ascension (J2000)
16- 17 I2 min RAm Right Ascension (J2000)
19- 22 F4.1 s RAs Right Ascension (J2000)
24 A1 --- DE- Declination sign (J2000)
25- 26 I2 deg DEd Declination (J2000)
28- 29 I2 arcmin DEm Declination (J2000)
31- 34 F4.1 arcsec DEs Declination (J2000)
36- 38 F3.1 km/s VLSR LSR velocity
40- 42 I3 pc Dist Distance (2)
44- 47 F4.1 10+22cm-2 NH2 H2 column density (3)
49- 51 F3.1 km/s Vel1 Velocity range, lower value (4)
52 A1 --- --- [-]
53- 56 F4.1 km/s Vel2 Velocity range, upper value (4)
58- 59 I2 arcsec Size1 Map size 30m
60 A1 --- --- [x]
61- 62 I2 arcsec Size2 Map size 30m
--------------------------------------------------------------------------------
Note (1): starless (s) or pre-stellar (p), following the definition given in
Crapsi et al. (2005ApJ...619..379C 2005ApJ...619..379C).
Note (2): Distance reference:
B68: Alves & Franco (2007A&A...470..597A 2007A&A...470..597A)
L429, OphD and HMM-1: Ortiz-Leon et al. (2018ApJ...869L..33O 2018ApJ...869L..33O)
L694-2: Kawamura et al. (2001PASJ...53.1097K 2001PASJ...53.1097K)
L1521E: Galli et al. (2018ApJ...859...33G 2018ApJ...859...33G, Cat. J/ApJ/859/33)
Note (3): Value computed from Herschel/SPIRE observations towards the dust peak.
Note (4): Velocity ranges where the integrated emission has been computed.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 23 I4 --- Nx Number of pixels along X-axis
25- 28 I4 --- Ny Number of pixels along Y-axis
30- 34 I5 Kibyte size Size of FITS file
36- 70 A35 --- FileName Name of FITS file, in subdirectory fits
72-115 A44 --- Title Title of the FITS file
--------------------------------------------------------------------------------
Acknowledgements:
Silvia Spezzano, spezzano(at)mpe.mpg.de
(End) Patricia Vannier [CDS] 26-Sep-2020