J/A+A/687/A163 ALMA-IMF XI. Hot core candidates sample (Bonfand+, 2024)
ALMA-IMF XI. The sample of hot core candidates: A rich population of young
high-mass protostars unveiled by the emission of methyl formate.
Bonfand M., Csengeri T., Bontemps S., Brouillet N., Motte F., Louvet F.,
Ginsburg A., Cunningham N., Galvan-Madrid R., Herpin F., Wyrowski F.,
Valeille-manet M., Stutz A.M., Di Francesco J., Gusdorf A.,
Fernandez-lopez M., Lefloch B., Liu H.-L., Sanhueza P.,
Alvarez-Gutierrez R.H., Olguin F., Nony T., Lopez-Sepulcre A., Dell'Ova P.,
Pouteau Y., Jeff D., Chen H.-R.V., Armante M., Towner A., Bronfman L.,
Kessler N.
<Astron. Astrophys. 687, A163 (2024)>
=2024A&A...687A.163B 2024A&A...687A.163B (SIMBAD/NED BibCode)
ADC_Keywords: Star Forming Region ; Infrared sources ; Interstellar medium ;
Morphology
Keywords: astrochemistry - catalogs - stars: formation - stars: massive -
ISM: molecules - submillimeter: ISM
Abstract:
The star formation process leads to an increased chemical complexity
in the interstellar medium. Sites associated with highmass
star and cluster formation exhibit a so-called hot core phase,
characterized by high temperatures and column densities of complex
organic molecules.
We aim to systematically search for and identify a sample of hot cores
toward the 15 Galactic protoclusters of the ALMA-IMF
Large Program and investigate their statistical properties.
We built a comprehensive census of hot core candidates toward the
ALMA-IMF protoclusters based on the detection of two CH3OCHO
emission lines at 216.1GHz. We used the source extraction algorithm
GExt2D to identify peaks of methyl formate (CH3OCHO) emission, a
complex species commonly observed toward sites of star formation.We
performed a cross-matching with the catalog of thermal dust continuum
sources from the ALMA-IMF 1.3mm continuum data to infer their physical
properties.
We built a catalog of 76 hot core candidates with masses ranging from
∼0.2M☉ to ∼80M☉, of which 56 are new detections. A large
majority of these objects, identified from methyl formate emission,
are compact and rather circular, with deconvolved full width at half
maximum (FWHM) sizes of ∼2300 au on average. The central sources of
two target fields show more extended, but still rather circular,
methyl formate emission with deconvolved FWHM sizes of ∼6700au and
13400au. About 30% of our sample of methyl formate sources have core
masses above 8M☉ and range in size from ∼1000au to 13400au,
which is in line with measurements of archetypical hot cores. The
origin of the CH3OCHO emission toward the lower-mass cores may be
explained as a mixture of contributions from shocks or may correspond
to objects in a more evolved state (i.e., beyond the hot core stage).
We find that the fraction of hot core candidates increases with the
core mass, suggesting that the brightest dust cores are all in the hot
core phase.
Our results suggest that most of these compact methyl formate sources
are readily explained by simple symmetric models, while collective
effects from radiative heating and shocks from compact protoclusters
are needed to explain the observed extended CH3OCHO emission. The
large fraction of hot core candidates toward the most massive cores
suggests that they rapidly enter the hot core phase and that feedback
effects from the forming protostar(s) impact their environment on
short timescales.
Description:
We have investigated the spatial distribution of methyl formate
emission toward 15 massive protoclusters targeted by the ALMA-IMF
Large Program. Methyl formate is a complex species commonly detected
in star-forming regions, and we used it to search for hot core
candidates in our dataset. We computed and analyzed moment 0 maps,
combining two strong transitions of methyl formate at 216.2GHz with
Eup/k=109K. We used a source-extraction algorithm to extract and
characterize the cores that have methyl formate emission. We
cross-matched our catalog of methyl formate sources with that of the
compact continuum cores of the ALMA-IMF dataset in order to derive and
compare their physical properties and constrain their nature.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 130 78 Catalog of the sources extracted from the moment 0
maps of methyl formate using the GExt2D algorithm
tablec1.dat 143 76 Properties of the continuum cores associated with
the methyl formate sources toward
the 15 ALMA-IMF protoclusters
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See also:
J/A+A/662/A9 : 15 dense molecular cloud regions ALMA images (Ginsburg+, 2022)
J/A+A/664/A26 : W43-MM2+MM3 ministarburst ALMA data (Pouteau+, 2022)
J/A+A/674/A75 : W43-MM1 and W43-MM2+MM3 ALMA datacubes (Nony+, 2023)
J/A+A/687/A217 : 15 massive protoclusters point-process mapping
(Dell'Ova+, 2024)
J/A+A/690/A33 : Core mass function in high-mass star formation (Louvet+, 2024)
J/A+A/694/A24 : ALMA-IMF XVI (Motte+, 2025)
Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Cluster Cluster name
10- 11 I2 --- ID ?=- Source Id within the cluster
14- 27 A14 --- Name Name of the source
29- 30 I2 --- OName ? Previously identified toward W43-MM1 in
Paper IV (Brouillet et al.,
2022A&A...665A.140B 2022A&A...665A.140B) Id number
31 A1 --- n_Name [*] Note (1)
33- 34 I2 h RAh Peak right ascension (J2000) (2)
36- 37 I2 min RAm Peak right ascension (J2000) (2)
39- 43 F5.2 s RAs Peak right ascension (J2000) (2)
45 A1 --- DE- Peak declination sign (J2000) (2)
46- 47 I2 deg DEd Peak declination (J2000) (2)
49- 50 I2 arcmin DEm Peak declination (J2000) (2)
52- 55 F4.1 arcsec DEs Peak declination (J2000) (2)
57- 63 F7.1 mJy/beam.km/s SpeakMF ?=- Peak intensity (2)
65- 69 F5.1 --- S/N ?=- Signal-to-noise ratio (2)
71- 74 F4.2 arcsec thetamaj ?=- Major axis (2)
75 A1 --- --- [x]
76- 79 F4.2 arcsec thetamin ?=- Minor axis (2)
81- 86 F6.1 deg PA []?=- Position angle (2)
89- 92 F4.2 arcsec thetamajd ?=- Deconvolved major axis (3)
93 A1 --- --- [x]
94- 97 F4.2 arcsec thetamind ?=- Deconvolved minor axis (3)
99-103 F5.1 deg PAd []?=- Deconvolved position angle
105-111 F7.1 au FWHMMFd ?=- Mean deconvolved FWHM source size of
the methyl formate emission is computed
at the distance of each protocluster (4)
113-117 F5.1 km/s VLSR ?=- Rest velocity of the source (5)
119-121 F3.1 km/s e_VLSR ?=- Rest velocity of the source error
123-124 I2 % Channels ?=- Percentage of the total number of
channels per spw that contain emission
above the 3σ noise level
(Sect. 3.3)
126-130 A5 --- Class Tentative classification (6)
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Note (1): In the cases of G328.25, G328-shock1, and G328-shock2, the asterisk
indicates the peak positions of the methyl formate emission initially
extracted by GExt2D, which correspond to accretion shocks (see Fig. 4, as well
as Csengeri et al., 2018A&A...617A..89C 2018A&A...617A..89C).
Note (2): The peak position, peak intensity, signal-to-noise ratio, major and
minor axes as well as position angle of the 2D Gaussian, are derived using
GExt2D, except for the brightest source of G327.29, G328.25 and W51-E, where
the peak position of the methyl formate emission is set as the position of the
brightest compact continuum core.
Note (3): The major and minor axes and position angle deconvolved from the line
cube beam size as explained in Appendix E.
Note (4): When the deconvolved source size falls below the minimum size set for
each protocluster (see Sect. 5.3), then the deconvolved major and minor axes,
as well as the position angle values are left blank, and the mean deconvolved
source size of the methyl formate emission (FWHMMFd) is set to half the
synthesized beam size of the line cube.
Note (5): The rest velocity of the source is derived from the fits to the three
CH3OCHO lines that are not contaminated by DCO+ and the uncertainty
represents the standard deviation.
Note (6): methyl formate sources tentatively classified as hot cores (HC) based
on their mass >8M☉. The sources with their lowest estimated mass
<8M☉ are marked with a star (HC*).
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Byte-by-byte Description of file: tablec1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Cluster Cluster name (1)
10- 21 A12 --- Name ID of the methyl formate sources
22 A1 --- n_Name [*] Note on Name (1)
24- 25 I2 h RAh ? Right ascension (J2000) (2)
27- 28 I2 min RAm ? Right ascension (J2000) (2)
30- 34 F5.2 s RAs ? Right ascension (J2000) (2)
36 A1 --- DE- Declination sign (J2000) (2)
37- 38 I2 deg DEd ? Declination (J2000) (2)
40- 41 I2 arcmin DEm ? Declination (J2000) (2)
43- 47 F5.2 arcsec DEs ? Declination (J2000) (2)
49- 52 F4.2 arcsec d ?=- Angular offset between the peak position
of the methyl formate source and its
associated compact continuum core
54- 58 F5.1 mJy/beam S1.3mmpk Peak intensity at 1.3mm from the unsmoothed
core catalog (Dell'Ova et al., 2024,
Cat. J/A+A/687/A217) (3)
60- 64 F5.1 mJy/beam e_S1.3mmpk Peak intensity at 1.3mm from the unsmoothed
core catalog error
66- 71 F6.1 mJy S1.3mmint Integrated intensity at 1.3mm from the
unsmoothed core catalog (Dell'Ova et al.,
2024, Cat. J/A+A/687/A217)
73- 77 F5.1 mJy e_S1.3mmint Integrated intensity at 1.3mm from the
unsmoothed core catalog error
79- 82 F4.2 arcsec thetamaj ?=- Major axis of the compact continuum core
from the unsmoothed core catalog (Dell'Ova
et al., 2024, Cat. J/A+A/687/A217) (4)
83 A1 --- --- [x]
84- 87 F4.2 arcsec thetamin ?=- Minor axis of the compact continuum core
from the unsmoothed core catalog (Dell'Ova
et al., 2024, Cat. J/A+A/687/A217) (4)
89- 93 F5.1 deg PA []?=- Position angle of the compact
continuum core from the unsmoothed core
catalog (Dell'Ova et al., 2024,
Cat. J/A+A/687/A217) (4)
95-100 F6.1 au FWHMMFd Deconvolved mean size (FWHM) of the
continuum cores
102-107 F6.1 mJy S3mmint 3mm integrated intensity from the unsmoothed
core catalog (Dell'Ova et al., 2024,
Cat. J/A+A/687/A217)
109-113 F5.2 mJy e_S3mmint 3mm integrated intensity from the unsmoothed
core catalog (XII) error
115-118 F4.2 --- tau ?=- Opacity computed at Td=100K (5)
120-124 F5.1 Msun Mass1 ?=- Mass range, lower value (6)
125 A1 --- --- [-]
126-129 F4.1 Msun Mass2 ?=- Mass range, upper value (6)
131-134 F4.1 Msun Mcore ?=- Core mass used to plot Figs. 13, 16 and
18, computed at Td=100K for all methyl
formate sources (5)
136-139 F4.1 --- alpha Spectral index (see Sect. 5.2)
141-143 I3 % fracff Fraction of the fluxes measured at 1.3mm
that is due to free-free emission and that
are subtracted to the fluxes given in
S1.3mmpeak and S1.3mmint to obtain the mass
estimates given in Mass1-Mass2 and Mcore
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Note (1): The sources marked with a * in the first column are not associated
with any compact continuum core.
Note (2): Position of the associated compact continuum core from the
getsf-unsmoothed catalog presented in Dell'Ova et al., 2024A&A...687A.217D 2024A&A...687A.217D,,
Cat. J/A+A/687/A217).
Note (3): For the sources that are not associated with compact continuum cores,
peak intensities have been measured in the 1.3mm continuum maps
(see Sect. 5.1).
Note (4): These values are deconvolved from the continuum map beam size.
Note (5): except for the six most extreme sources for which we used 300K;
see Sect. 5.4.
Note (6): Core mass range computed with Td ranging from 50K to 150K (except for
the six most extreme sources for which we used 200-400K; see Sect. 5.4).
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History:
From electronic version of the journal
References:
Motte et al., Paper I 2022A&A...662A...8M 2022A&A...662A...8M
Ginsburg et al., Paper II 2022A&A...662A...9G 2022A&A...662A...9G, Cat. J/A+A/662/A9
Pouteau et al., Paper III 2022A&A...664A..26P 2022A&A...664A..26P, Cat. J/A+A/664/A26
Brouillet et al., Paper IV 2022A&A...665A.140B 2022A&A...665A.140B
Nony et al., Paper V 2023A&A...674A..75N 2023A&A...674A..75N, Cat. J/A+A/674/A75
Pouteau et al., Paper VI 2023A&A...674A..76P 2023A&A...674A..76P
Cunningham et al., Paper VII 2023A&A...678A.194C 2023A&A...678A.194C
Diaz-Gonzalez et al., Paper VIII 2023ApJS..269...55D 2023ApJS..269...55D
Towner et al., Paper IX 2024ApJ...960...48T 2024ApJ...960...48T
Armante et al., Paper X 2024A&A...686A.122A 2024A&A...686A.122A
Bonfand et al., Paper XI 2024A&A...687A.163B 2024A&A...687A.163B
Dell'Ova et al., Paper XII 2024A&A...687A.217D 2024A&A...687A.217D, Cat. J/A+A/687/A217
Alvarez-Gutierrez et al., Paper XIII 2024A&A...689A..74A 2024A&A...689A..74A
Galvan-Madrid et al., Paper XIV 2024ApJS..274...15G 2024ApJS..274...15G
Louvet et al., Paper XV 2024A&A...690A..33L 2024A&A...690A..33L, Cat. J/A+A/690/A33
Motte et al., Paper XVI 2025A&A...694A..24M 2025A&A...694A..24M, Cat. J/A+A/694/A24
(End) Patricia Vannier [CDS] 24-Jan-2025