J/A+A/696/A171 Core Corona Australis 151 spectra (Redaelli+, 2025)
Hunting pre-stellar cores with APEX: Corona Australis 151,
the densest pre-stellar core or the youngest protostar?
Redaelli E., Spezzano S., Caselli P., Harju J., Arzoumanian D., Sipilae O.,
Belloche A., Wyrowski F., Pineda J.E.
<Astron. Astrophys. 696, A171 (2025)>
=2025A&A...696A.171R 2025A&A...696A.171R (SIMBAD/NED BibCode)
ADC_Keywords: Interstellar medium ; Molecular clouds ; Radio lines ;
Spectra, radio
Keywords: stars: formation - ISM: clouds - ISM: molecules - radio lines: ISM -
ISM: individual objects: Corona Australis 151
Abstract:
Pre-stellar cores are the birthplaces of Sun-like stars and represent
the initial conditions for the assembly of protoplanetary systems. Due
to their short lifespans, they are rare. As part of recent efforts to
increase the number of such sources identified in the solar
neighbourhood, we have selected a sample of 40 starless cores from the
publicly available core catalogues of the Herschel Gould Belt survey.
In this work, we focus on a source that stands out for its high
central density: Corona Australis 151.
We used molecular lines that trace dense gas (n≳106cm-3) to
confirm the exceptionally high density of this object, study its
physical structure, and understand its evolutionary stage.
We detected the N2H+ 3-2 and 5-4 transitions and the N2D+ 3-2,
4-3, and 6-5 lines with the Atacama Pathfinder EXperiment (APEX)
telescope. We used the Herschel continuum data to infer a spherically
symmetric model of the core's density and temperature. This was used
as input to perform a non-local-thermodynamic-equilibrium radiative
transfer to fit the five observed lines.
Our analysis confirms that this core is characterised by very high
densities (a few x107cm-3 at the centre) and cold temperatures
(8-12K). We inferred a high deuteration level of N2D+/N2H+=0.50,
indicative of an advanced evolutionary stage. In the large bandwidth
covered by the APEX data, we detected several other deuterated
species, including CHD2OH, D2CO, and ND3. We also detected
multiple sulphurated species that present broader lines with signs of
high-velocity wings.
High-angular resolution observations will be necessary to unveil the
evolutionary stage of Cra 151. The detection of a compact emission at
70um does not exclude that the source is a first hydrostatic core or
in a very early stage of the protostellar phase. The observation of
high-velocity wings and the fact that the linewidths of N2H+ and
N2D+ become larger with increasing frequency can be interpreted as
either an indication of supersonic infall motions developing in the
central parts of a very evolved pre-stellar core or the signature of
outflows from a very low luminosity object.
Description:
We present a detailed study of the molecular emission towards the core
Corona Australis 151, which belongs to a sample of dense cores
extracted from Herschel continuum observations. In particular, we have
focussed on the rotational lines of N2H+ 3-2 and 5-4, and N2D+
3-2, 4-3, and 6-5. All have been detected above the 3sigma level.
These lines have high critical densities, and hence support the very
high density detected at the core's centre via the continuum emission.
We modelled the lines using a MCMC approach coupled with
non-local-thermodynamic-equilibrium radiative transfer. Our results
suggests that at the centre the cores is denser than a few
x107cm-3, and that the deuteration of N2H+ is high (∼50%). We
also reported the serendipitous detection of more than 30 other lines
in the data frequency coverage, including several deuterated and
multiply- deuterated species.
Spectra of all the lines detected at the centre of the target, core
Corona Australis 151. The data were collected with the Atacama
Pathfinder EXperiment (APEX) single-dish telescope. We used the
receivers SEPIA345, nFLASH230, and nFLASH460 to cover the frequencies
of the main lines of interest (from ∼230 to ∼460GHz). We used the the
FFTS backend, providing a spectral resolution of 64kHz. The data were
collected in several sessions during 2022. The data were reduced to
the main beam temperature scale using the GILDAS/CLASS software.
Objects:
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RA (2000) DE Designation(s)
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19 10 29.17 -37 08 27.0 core Corona Australis 151
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 65 37 List of spectra
sp1/* . 5 Individual spectra (file[12345].dat)
sp2/* . 32 Individual spectra (file[6789].dat file??.dat
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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- 14 A14 --- FileName File name
16- 65 A50 --- Title Title of the file
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Byte-by-byte Description of file: sp1/*
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Bytes Format Units Label Explanations
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1- 17 E17.10 km/s Vlsr Doppler velocity of the channel
19- 29 E11.5 K TMB Intensity of the spectrum in the channel,
in main-beam temperature scale
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Byte-by-byte Description of file: sp2/*
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Bytes Format Units Label Explanations
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1- 17 E17.10 km/s Vlsr Doppler velocity of the channel
19- 29 E11.5 K TMB Intensity of the spectrum in the channel,
in main-beam temperature scale
32- 41 E10.5 K TMBfit1 ? Intensity of the Gaussian fit to the spectrum
44- 53 E10.5 K TMBfit2 ? Intensity of the Gaussian fit to the spectrum
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Acknowledgements:
Elena Redaelli, elena.redaelli(at)eso.org
(End) Elena Redaelli [ESO, Germany], Patricia Vannier [CDS] 26-Mar-2025