J/A+A/711/A157 B-FROST. MBM12 CO cubes and H2 map (Vorster+, 2026)
B-FROST: B-Fields and star formation across scales with TRAO.
CO abundances, dynamics and relative orientations in the translucent
high latitude cloud MBM12.
Vorster J.M., Montillaud J., Juvela M., Falgarone E., Oers J.,
Mannfors E., Alina D., Gu Q., Kang H., Lee C.W., Li S., Liu T.,
Pattle K., Pelkonen V.-M., Ristorcelli I., Zavagno A., Toth L.V.
<Astron. Astrophys. 711, A157 (2026)>
=2026A&A...711A.157V 2026A&A...711A.157V (SIMBAD/NED BibCode)
ADC_Keywords: Molecular clouds ; Carbon monoxide ; Radio lines
Keywords: methods: observational - ISM: abundances - ISM: clouds -
ISM: kinematics and dynamics - ISM: magnetic fields -
ISM: individual objects: MBM12
Abstract:
On average, in our Galaxy, the star formation efficiency (SFE) is of
the order of a few percent, which is lower than theoretical
predictions. Detailed observational studies of individual molecular
clouds may offer insight into the contributing factors to the low
galactic SFE.
We investigated the high-latitude molecular cloud MBM12 as part of the
B-fields and star formation across scales (B-FROST) survey with the
Taeduk Radio Astronomical Observatory (TRAO) to assess why star
formation activity in MBM12 is low.
We estimated N(H2) with Herschel dust emission and a dust opacity
kappamu derived from near-infrared extinction, 21cm HI column
densities, and far-infrared emission. With 12CO and 13CO (J=1-0)
line observations, covering an area of 2.5{deh}x3{deh} at 48"
resolution, we mapped the CO column density N(CO), CO-to-H2 factor
X(CO), and abundance [CO/H2]. We estimated the multi-scale virial
parameter alphavir and constructed mass-size scaling laws of hierarchical
structures with dendrograms. We computed the relative orientation
between column density structures and magnetic fields using Planck
observations of dust polarisation.
We identified four main regions based on velocities with H2 column
densities ranging from 2x1020-1.3x1022cm-2. The CO integrated
line intensity, W(CO), increases linearly with N(H2), providing an
average X(CO) factor close to the Galactic average. At a low N(H2),
X(CO) varies below XGal due to the fall-off of collisional
de-excitation in low-density gas, and above XGal due to the drop of CO
abundances in poorly shielded cloud edges. The hierarchical structures
follow a broken power law mass-size relation M=ARalpha. The values
of alphavir ranged from 3-60, with the smallest values at 0.1pc
scales. The mass-size relations for the structures with the lowest
alphavir have scaling factors, A, three times larger than those of
high alphavir structures, indicating external pressure one order of
magnitude larger than the former. We found a transition from parallel
to perpendicular relative orientations between column density
structures and the magnetic field at N(H2)=4.5x1021cm-2.
We provide the first integrated chemical, dynamical, and magnetic
field analysis of MBM12. Further investigation into the scale
dependence of the mass-size relation and virial parameter can
highlight the role of external pressure in regulating the
star-formation efficiency.
Description:
We present TRAO (Taeduk Radio Astronomical Observatory) 12CO and
13CO (J=1-0) spectral line data cubes of the high-latitude molecular
cloud MBM12, obtained as part of the B-FROST (B-Fields and staR
fOrmation across Scales with TRAO) survey. The cloud was mapped in
on-the-fly mode over a 2.5degx3deg field centred on
(l,b)=(159deg,-34deg) at 44arcsec angular resolution and 0.2km/s
spectral resolution. Orthogonal scanning directions were combined and
gridded with GILDAS CLASS. Antenna temperatures TA* were converted
to main beam temperature T_mb using beam efficiencies etaeff=0.51 at
115GHz (12CO) and etaeff=0.54 at 110GHz (13CO). The achieved
per-channel noise levels are sigma(12CO)=0.28K and
sigma(13CO)=0.13K.
We also provide the H2 column density map derived from Herschel
SPIRE photometry at 250um, 350um, and 500um from the Galactic Cold
Cores open time programme. Surface brightness maps were
colour-corrected, background-subtracted, convolved to 40arcsec
resolution, and fitted pixel-by-pixel with a modified blackbody using
MCMC sampling. The dust opacity kappa_1200 was calibrated against
K-band NIR extinction from iNICEST, with spatial variation accounted
for (mean kappa1200=(192±7)x10-3cm2/g). This map covers the
southern half of MBM12 only. A total CO column density map N(CO)
derived by LTE analysis of the 13CO spectral cube is also included.
Objects:
-------------------------------------------
RA (2000) DE Designation(s)
-------------------------------------------
02 56 49.99 +19 32 00.0 MBM12 = MBM 12
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 127 8 List of fits maps and datacubes
fits/* . 8 Individual fits maps and datacubes
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See also:
J/BaltA/11/219 : Vilnius photometry in MBM12 (Kazlauskas+, 2002)
J/BaltA/11/231 : Extinction in MBM12 (Straizys+, 2002)
Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1 A1 --- --- [G]
2- 10 F9.5 deg GLON Galactic longitude of center
11- 19 F9.5 deg GLAT Galactic latitude of center
21- 23 I3 --- Nx Number of pixels along X-axis
25- 27 I3 --- Ny Number of pixels along Y-axis
29- 31 I3 --- Nz ? Number of slcies for the datacubes
33- 38 I6 m/s bVRAD ? Lower value of VRAD interval for the datacubes
40- 44 I5 m/s BVRAD ? Upper value of VRAD interval for the datacubes
46- 48 I3 m/s dVRAD ? VRAD resolution for the datacubes
50- 55 I6 Kibyte size Size of FITS file
57- 69 A13 --- FileName Name of FITS file, in subdirectory fits
71-127 A57 --- Title Title of the FITS file
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Acknowledgements:
From Jakobus Vorster, jobvorster8(at)gmail.com
JMV and MJ acknowledge support from the Academy of Finland grant No
348342.
License: CC-BY-4.0
References:
Pineda et al., 2010ApJ...721..686P 2010ApJ...721..686P
Szucs et al., 2014MNRAS.445.4055S 2014MNRAS.445.4055S
HI4PI Collaboration, 2016A&A...594A.116H 2016A&A...594A.116H, Cat. J/A+A/594/A116
Jeong et al., 2019JKAS...52..227J 2019JKAS...52..227J
(End) Patricia Vannier [CDS] 22-May-2026