J/A+A/640/A74 SOLIS. VIII. L1157-B1 spectra (Spezzano+, 2020)
Seeds of Life in Space (SOLIS).
VIII. SiO isotopic fractionation and a new insight in the shocks of L1157-B1.
Spezzano S., Codella C., Podio L., Ceccarelli C., Caselli P., Neri R.,
Lopez-Sepulcre A.
<Astron. Astrophys. 640, A74 (2020)>
=2020A&A...640A..74S 2020A&A...640A..74S (SIMBAD/NED BibCode)
ADC_Keywords: Radio lines ; Spectra, radio
Keywords: ISM: clouds - ISM: molecules - ISM: jets and outflows
Abstract:
Contrary to what is expected from models of Galactic chemical
evolution (GCE), the isotopic fractionation of silicon (Si) in the
Galaxy has been recently found to be constant. This finding calls for
new observations, also at cores scales, to re-evaluate the
fractionation of Si.
L1157-B1 is one of the outflow shocked regions along the blue-shifted
outflow driven by the Class 0 protostar L1157-mm, and is an ideal
laboratory to study the material ejected from the grains in very short
timescales, i.e. its chemical composition is representative of the
composition of the grains.
We imaged 28SiO, 29SiO and 30SiO J = 2-1 emission towards
L1157-B1 and B0 with the NOrthern Extended Millimeter Array (NOEMA)
interferometer as part of the Seeds of Life in Space (SOLIS) large
project. We present here a study of the isotopic fractionation of SiO
towards L1157-B1. Furthermore, we use the high spectral resolution
observations on the main isotopologue, 28SiO, to study the jet
impact on the dense gas. We present here also single-dish observations
obtained with the IRAM 30m telescope and Herschel-HIFI. We carried out
a non-LTE analysis using a Large Velocity Gradient (LVG) code to model
the single-dish observations.
From our observations we can show that (i) the (2-1) transition of the
main isotopologue is optically thick in L1157-B1 even at high
velocities, and (ii) the [29SiO/30SiO] ratio is constant across
the source, and consistent with the solar value of 1.5.
We report the first isotopic fractionation maps of SiO in a shocked
region and show the absence of a mass dependent fractionation in
29Si and 30Si across L1157-B1. A high-velocity bullet in 28SiO
has been identified, showing the signature of a jet impacting on the
dense gas. With the dataset presented in this paper, both
interferometric and single-dish, we were able to study in great detail
the gas shocked at the B1a position and its surrounding gas.
Description:
The single-dish observations of the 28SiO, 29SiO, and 30SiO
lines from J=2-1 to J=8-7 (see Table 1 for the frequencies) have been
obtained using the IRAM 30-m antenna in the context of the ASAI Large
Program. Observations have been done in Wobbler Mode at the position
of the B1 shock, namely at RA(2000)=20:39:10.02, DE(2000)=+68:01:10.5.
The SiO, 29SiO, and 30SiO J=12-11 transitions were observed with
Herschel-HIFI on 2010 October 27 and 2009 August 1, during the
unbiased spectral survey CHESS (e.g. Ceccarelli et al. 2010) with the
HIFI bands 1a, at the same position used for the IRAM 30-m
observations.
The 28SiO, 29SiO and 30SiO J=2-1 lines were observed with NOEMA
using the Polyfix correlator, with a total spectral band of 8GHz, and
a spectral resolution of 2.0MHz (7.3km/s). The main isotopologue has
been observed also at high spectral resolution (62.5kHz, 0.22km/s),
here smoothed to 0.5km/s (28SiO_HR.lmv-clean).
Objects:
----------------------------------------------------
RA (2000) DE Designation(s)
----------------------------------------------------
20 39 11 +68 01.3 L1157-B1 = [DE95] LDN 1157 B1
----------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 110 4 List of fits datacubes
listsp.dat 44 15 List of spectra
fits/* . 4 Individual fits datacubes
sp/* . 15 Individual spectra
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See also:
J/A+A/605/A57 : SOLIS. I. OMC2-FIR4 HC3N and HC5N images (Fontani+, 2017)
J/A+A/605/L3 : SOLIS. II. L1157-B1 NH2CHO image (Codella+, 2017)
J/A+A/640/A75 : SOLIS. X. NGC 1333 IRAS 4A images (De Simone+, 2020)
Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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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- 32 I3 --- Nz Number of pixels along Z-axis
34- 42 F9.1 m/s bVRAD Lower value of VRAD interval
44- 49 I6 m/s BVRAD Upper value of VRAD interval
51- 58 F8.3 m/s dVRAD VRAD resolution
60- 65 I6 Kibyte size Size of FITS file
67- 84 A18 --- FileName Name of FITS file, in subdirectory fits
86-110 A25 --- Title Title of the FITS file
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Byte-by-byte Description of file: listsp.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- FileName Name of the spectrum file in subdirectoy sp
18- 44 A27 --- Title Title of the file
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Byte-by-byte Description of file: sp/*
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Bytes Format Units Label Explanations
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3- 15 F13.9 km/s Vlsr LSR velocity
19- 29 E11.5 K Tmb Mean brightness temperature
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Acknowledgements:
Silvia Spezzano, spezzano(at)mpe.mpg.de
References:
Fontani et al., Paper I 2017A&A...605A..57F 2017A&A...605A..57F, Cat. J/A+A/605/A57
Codella et al., Paper II 2017A&A...605L...3C 2017A&A...605L...3C, Cat. J/A+A/605/L3
Ceccarelli et al., 2017ApJ...850..176C 2017ApJ...850..176C
Punanova et al., Paper III 2018ApJ...855..112P 2018ApJ...855..112P
Favre et al., Paper IV 2018ApJ...859..136F 2018ApJ...859..136F
Codella et al., Paper V 2020A&A...635A..17C 2020A&A...635A..17C
Favre et al., Paper VII 2020A&A...635A.189F 2020A&A...635A.189F
Feng et al., Paper IX 2020ApJ...896...37F 2020ApJ...896...37F
De Simone et al., Paper X 2020A&A...640A..74D 2020A&A...640A..74D, Cat. J/A+A/640/A74
(End) Patricia Vannier [CDS] 10-Jun-2020