J/A+A/697/A190 ALMA-ATOMS survey. Weak hot core candidates (Li+, 2025)
The ALMA-ATOMS survey:
A sample of weak hot core candidates identified through line stacking.
Li Z.-Y., Liu X., Liu T., Qin S.-L., Goldsmith P.F., Garcia P., Peng Y.,
Chen L., Jiao Y., Kou Z., Li C., Zou J., Tang M., Li S., Liu M., Garay G.,
Xu F., Jiao W., Luo Q.-Y., Zhang S., Gu Q.-L., Mai X., Zhang Y.-K., Weng J.,
Won Lee C., Sanhueza P., Dib S., Das S.R., Tang X., Bronfman L., Gorai P.,
Tatematsu K., Liu H.-L., Yang D., Zhang Z., Shen X.
<Astron. Astrophys. 697, A190 (2025)>
=2025A&A...697A.190L 2025A&A...697A.190L (SIMBAD/NED BibCode)
ADC_Keywords: Millimetric/submm sources ; Spectroscopy ; Molecular data
Keywords: ISM: clouds - ISM: lines and bands - ISM: molecules - galaxies: ISM
Abstract:
Hot cores represent critical astrophysical environments for high-mass
star formation, distinguished by their rich spectra of organic
molecular emission lines. Nevertheless, comprehensive statistical
analyses of extensive hot core samples remain relatively scarce in
current astronomical research.
We aim to utilize high-angular-resolution molecular line data from the
Atacama Large Millimeter and Submillimeter Array (ALMA) to identify
hot cores, with a particular focus on weak-emission candidates, and to
provide one of the largest samples of hot core candidates to date.
We propose to use spectral stacking and imaging techniques of complex
organic molecules (COMs) in the ALMA-ATOMS survey, including line
identification and weights, segmentation of line datacubes,
resampling, stacking and normalization, moment 0 maps, and data
analysis, to search for hot core candidates. The molecules involved
include CH3OH, CH3OCHO, C2H5CN, C2H5OH, CH3OCH3,
CH3-COCH3_, and CH3CHO. We classify cores with dense emission of
CH3OH and at least one molecule from the other six molecules as hot
core candidates.
In addition to the existing sample of 60 strong hot cores from the
ALMA-ATOMS survey, we have detected 40 new weak candidates through
stacking. All hot core candidates display compact emission from at
least one of the other six COM species. For the strong sample, the
stacking method provides molecular column density estimates that are
consistent with previous fitting results. For the newly identified
weak candidates, all species except CH3CHO show compact emission in
the stacked image, which cannot be fully resolved spatially. These
weak candidates exhibit column densities of COMs that are
approximately one order of magnitude lower than the ones of the strong
sample. The entire hot core sample, including the weak candidates,
reveals tight correlations between the compact emission of CH3OH and
other COM species, suggesting they may share a similar chemical
environment for COMs, with CH3OH potentially acting as a precursor
for other COMs. Among the 100 hot cores in total, 43 exhibit extended
CH3CHO emission spatially correlated with SiO and H13CO+,
suggesting that CH3CHO may form in widely distributed shock
regions.
The molecular line stacking technique is used to identify hot core
candidates in this work, leading to the identification of 40 new hot
core candidates. Compared to spectral line fitting methods, it is
faster and more convenient, and enables weaker hot cores to be
detected with greater sensitivity.
Description:
Based on the spectral line samples of seven molecules - CH3OH,
CH3OCHO, C2H5CN, C2H5OH, CH3OCH3, CH3CHO, and
CH3COCH3 - identified in the hot core region of G9.62+0.19, we
employed a molecular spectral line stacking technique to search for
hot core candidates in the ATOMS Band 3 data. As a result, the sample
of hot core candidates was successfully expanded to 100 sources. The
stacked spectra of these 100 candidates, along with annotations of the
potential molecular identifications, are presented in Table B.1.
Tables B.2, B.3, and B.4 list the spectral parameters of the seven
molecules across the 100 hot core candidate sources.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tableb1.dat 85 249 Identified transitions from stacked spectra of
100 hot cores
tableb2.dat 109 100 Line parameters of CH3OH
tableb3.dat 167 100 Physical parameters of CH3OCHO, C2H5CN and
C2H5OH
tableb4.dat 151 100 Physical parameters of CH3OCH3, CH3CHO and
CH3COCH3
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Byte-by-byte Description of file: tableb1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 21 A21 --- Species Name of molecular species
23- 49 A27 --- Trans Quantum number of molecular transitions
51- 60 F10.3 MHz Freq Rest frequency
corresponding to the molecular transition
62- 70 F9.5 K Elow Lower energy level temperature
corresponding to the transition
72- 80 F9.5 K Eup Upper energy level temperature
corresponding to the transition
82- 85 A4 --- database [CDMS JPL] A molecular spectral database for
obtaining information on molecular transitions
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Byte-by-byte Description of file: tableb2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- ID [1/100] Line number corresponding
to each line
5- 17 A13 --- Source Name of source
19 A1 --- n_Source [N] N for hot core candidates newly
identified in this work
21- 22 I2 h RAh Right ascension (J2000)
24- 25 I2 min RAm Right ascension (J2000)
27- 31 F5.2 s RAs Right ascension (J2000)
33 A1 --- DE- Declination sign (J2000)
34- 35 I2 deg DEd Declination (J2000)
37- 38 I2 arcmin DEm Declination (J2000)
40- 44 F5.2 arcsec DEs Declination (J2000)
46- 50 F5.2 kpc Dist Distance from the source to the sun
52- 55 F4.2 arcsec theta Source size
57- 60 F4.2 arcsec e_theta Error of source size
62- 64 I3 deg PA Position angle
66- 67 I2 deg e_PA Error of position angle
69- 74 F6.2 K.km/s Ip(CH3OH) Peak intensity of the moment 0
map of CH_3OH emission
76- 80 F5.2 K.km/s e_Ip(CH3OH) Error value of the peak intensity
of the moment 0 map of CH3OH
emission
82- 89 F8.2 K.km/s/arcsec2 I(CH3OH) Integrated intensity of the moment 0
map of CH3OH emission
91- 96 F6.2 K.km/s/arcsec2 e_I(CH3OH) Error value of the integrated
intensity of the moment 0 map of
CH_3OH emission
98-103 F6.1 10-16cm-2 N(CH3OH) Column density obtained by molecular
fitting moment 0 map
105-109 F5.1 10-16cm-2 e_N(CH3OH) Error value of the column density
obtained by molecular fitting
moment 0 map
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Byte-by-byte Description of file: tableb3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- ID [1/100] Line number corresponding
to each line
5- 17 A13 --- Source Name of source
19 A1 --- n_Source [N] N for hot core candidates newly
identified in this work
21- 27 F7.2 K.km/s Ip(CH3OCHO) ? Peak intensity of the moment 0 map
of CH3OCHO emission
29- 34 F6.2 K.km/s e_Ip(CH3OCHO) ? Error value of the peak intensity
of the moment 0 map of
CH3OCHO emission
36- 43 F8.2 K.km/s/arcsec2 I(CH3OCHO) ? Integrated intensity of the moment
0 map of CH3OCHO emission
45- 51 F7.2 K.km/s/arcsec2 e_I(CH3OCHO) ? Error value of the integrated
intensity of the moment 0 map of
CH_3OCHO emission
53- 60 F8.2 10-15cm-2 N(CH3OCHO) ? Column density obtained by
molecular fitting moment 0 map
62- 67 F6.2 10-15cm-2 e_N(CH3OCHO) ? Error value of the column density
obtained by molecular fitting
moment 0 map
69- 75 F7.2 K.km/s Ip(C2H5CN) ? Peak intensity of the moment 0 map
of C2H5CN emission
77- 81 F5.2 K.km/s e_Ip(C2H5CN) ? Error value of the peak intensity
of the moment 0 map of
C2H5CN emission
83- 90 F8.2 K.km/s/arcsec2 I(C2H5CN) ? Integrated intensity of the moment
0 map of C2H5CN emission
92- 98 F7.2 K.km/s/arcsec2 e_I(C2H5CN) ? Error value of the integrated
intensity of the moment 0 map of
C2H5CN emission
100-106 F7.2 10-15cm-2 N(C2H5CN) ? Column density obtained by
molecular fitting moment 0 map
108-112 F5.2 10-15cm-2 e_N(C2H5CN) ? Error value of the column density
obtained by molecular fitting
moment 0 map
114-120 F7.2 K.km/s Ip(C2H5OH) ? Peak intensity of the moment 0 map
of C2H5OH emission
122-126 F5.2 K.km/s e_Ip(C2H5OH) ? Error value of the peak intensity
of the moment 0 map of
C2H5OH emission
128-135 F8.2 K.km/s/arcsec2 I(C2H5OH) ? Integrated intensity of the moment
0 map of C2H5OH emission
137-142 F6.2 K.km/s/arcsec2 e_I(C2H5OH) ? Error value of the integrated
intensity of the moment 0 map of
C2H5OH emission
144-149 A6 10-15cm-2 N(C2H5OH) ? Column density obtained by
molecular fitting moment 0 map
151-167 A17 10-15cm-2 e_N(C2H5OH) ? Error value of the column density
obtained by molecular fitting
moment 0 map
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Byte-by-byte Description of file: tableb4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- ID [1/100] Line number corresponding
to each line
5- 17 A13 --- Source Name of source
19 A1 --- n_Source [N] N for hot core candidates newly
identified in this work
21- 27 F7.2 K.km/s Ip(CH3OCH3) ? Peak intensity of the moment 0
map of CH3OCH3 emission
29- 33 F5.2 K.km/s e_Ip(CH3OCH3) ? Error value of the peak intensity
of the moment 0 map of
CH3OCH3 emission
35- 42 F8.2 K.km/s/arcsec2 I(CH3OCH3) ? Integrated intensity of the
moment 0 map of CH3OCH3
emission
44- 50 F7.2 K.km/s/arcsec2 e_I(CH3OCH3) ? Error value of the integrated
intensity of the moment 0 map of
CH3OCH3 emission
52- 58 F7.2 10-15cm-2 N(CH3OCH3) ? Column density obtained by
molecular fitting moment 0 map
60- 65 F6.2 10-15cm-2 e_N(CH3OCH3) ? Error value of the column density
obtained by molecular fitting
moment 0 map
67- 73 F7.2 K.km/s Ip(CH3CHO) ? Peak intensity of the moment 0
map of CH3CHO emission
75- 79 F5.2 K.km/s e_Ip(CH3CHO) ? Error value of the peak intensity
of the moment 0 map of
CH_3CHO emission
81- 88 F8.2 K.km/s/arcsec2 I(CH3CHO) ? Integrated intensity of the
moment 0 map of CH3CHO emission
90- 95 F6.2 K.km/s/arcsec2 e_I(CH3CHO) ? Error value of the integrated
intensity of the moment 0 map of
CH3CHO emission
97-103 F7.2 10-15cm-2 N(CH3CHO) ? Column density obtained by
molecular fitting moment 0 map
105-109 F5.2 10-15cm-2 e_N(CH3CHO) ? Error value of the column density
obtained by molecular fitting
moment 0 map
111-116 F6.2 K.km/s Ip(CH3COCH3) ? Peak intensity of the moment 0
map of CH3COCH3 emission
118-122 F5.2 K.km/s e_Ip(CH3COCH3) ? Error value of the peak
intensity of the moment 0 map of
CH3COCH3 emission
124-130 F7.2 K.km/s/arcsec2 I(CH3COCH3) ? Integrated intensity of the
moment 0 map of CH3COCH3
emission
132-137 F6.2 K.km/s/arcsec2 e_I(CH3COCH3) ? Error value of the integrated
intensity of the moment 0 map of
CH3COCH3 emission
139-144 F6.1 10-15cm-2 N(CH3COCH3) ? Column density obtained by
molecular fitting moment 0 map
146-151 F6.2 10-15cm-2 e_N(CH3COCH3) ? Error value of the column density
obtained by molecular fitting
moment 0 map
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Acknowledgements:
Zi-Yang Li, ziyangli(at)shao.ac.cn
Referneces:
Qin et al., 2022MNRAS.511.3463Q 2022MNRAS.511.3463Q
Chen et al., 2025A&A...694A.166C 2025A&A...694A.166C
(End) Patricia Vannier [CDS] 17-Apr-2025