J/A+A/712/A125 L1506C NIKA2 maps at 1.15mm and 2mm and A(J) map (Zhu+, 2026)
Tracing grain growth in the forming prestellar core L1506C with 3D modeling of
Herschel, IRAM, and CFHT observations.
Zhu E., Ristorcelli I., Demyk K., Juvela M., Ysard N., Paradis D.,
Roussel H., Kiviaho W.
<Astron. Astrophys. 712, A125 (2026)>
=2026A&A...712A.125Z 2026A&A...712A.125Z (SIMBAD/NED BibCode)
ADC_Keywords: Interstellar medium ; Molecular clouds ; Extinction ;
Photometry, millimetric/submm ; Photometry, infrared
Keywords: radiative transfer - stars: formation - ISM: clouds -
dust, extinction - infrared: ISM - submillimeter: ISM
Abstract:
In the early phases of star formation, dense and cold structures such
as filaments and prestellar cores are commonly probed and studied via
observations of thermal dust emission. The inferred core properties
from these observations are critically dependent on the adopted dust
model, which must be characterized carefully. However, analysis of
dust properties in individual prestellar cores is often limited by the
wavelength range and spatial resolution of the observations.
Our target in this work, L1506C, is part of the filament L1506 in the
Taurus molecular cloud (D∼140pc). Previous studies using dust and
gas tracers suggest that it is a prestellar core in the making and
have revealed signatures of dust evolution. Our goal was to bring
further constraints on both the cloud structures and dust properties.
To do so, we used observations of dust emission covering, for the
first time, a broad wavelength range, from the far-infrared (FIR) to
millimeter range, as well as 3D radiative transfer modeling while also
taking into account constraints from extinction data.
We used both Herschel FIR observations and complementary millimeter
wavelength observations with NIKA2 at the IRAM 30m telescope. Analysis
of the spectral energy distributions over the whole spectral range was
first performed with modified black body (MBB) fits. The data were
then analyzed with 3D modeling using the radiative transfer code SOC
and the latest THEMIS 2 dust models. As additional constraints we used
extinction observations from WIRCam at CFHT and from Spitzer.
The MBB modeling over the wavelength range of 160um to 2mm revealed
that L1506C is fragmented into two low density cores with
nH2<5x104cm-3, independently of the assumed dust opacity, with
masses smaller than their Jeans masses. The dust color temperature (T)
drops from 16K in the filament to 11K in the cores, and the spectral
index β increases from 1.4 to 1.9, showing a clear T-β
anticorrelation and a change in grain properties. To model the source
with 3D radiative transfer modeling, grains more evolved than the
diffuse interstellar medium (ISM) are required in the densest part.
Using grains with sizes up to 0.7um, 50% porosity, and 50% ice
content, we were able to reproduce the observed millimeter emission
within a 10% residual in the central core region and the near-infrared
scattering (coreshine) within 1σ. Extinction data strongly
constrain the dust properties, but the best results we obtained still
overestimate the extinction by a factor of more than 2.5 with the
current THEMIS 2 dust model. The model NH2 has a maximum value of
1.3x1022cm-2, 1.7 times larger than the one calculated with MBB
modeling, and the model central dust temperature is down to 8K. Good
fits to the observations were obtained for the transition between
diffuse and evolved grains at low density, within the range
1500≥nH≥4500cm-3. When adopting a model with a transition
threshold of nH=3000cm-3, evolved grains account for 50% of the
dust content along the line of sight, where AV∼4 on the observed
extinction map.
Grain growth can already happen at a very early stage of star
formation, even before the onset of gravitational collapse. It is
difficult to precisely constrain the cloud properties with 3D
radiative transfer modeling when only using dust emission observations
because some of the parameters are degenerate. Observations of
near-infrared extinction and scattering and independent measurements
from molecular line data are crucial complements to these data,
providing independent constraints and breaking degeneracies in the
analysis.
Description:
We provide the processed NIKA2 maps of L1506C at 1.15mm and 2mm with
scanam_nika. The A(J) map derived from WIRCam observations is also
provided.
Objects:
---------------------------------------------
RA (2000) DE Designation(s)
---------------------------------------------
04 18 50.00 +25 19 14.9 L1506C = LDN 1506C
---------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 113 3 List of fits images
fits/* . 3 Individual fits images
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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- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 22 I3 --- Nx Number of pixels along X-axis
24- 26 I3 --- Ny Number of pixels along Y-axis
28- 32 I5 Kibyte size Size of FITS file
34- 71 A38 --- FileName Name of FITS file, in subdirectory fits
73-113 A41 --- Title Title of the FITS file
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Acknowledgements:
Enyi Zhu, enyi.zhu(at)utoulouse.fr
License: CC-BY-4.0
(End) Patricia Vannier [CDS] 17-Jul-2026