J/ApJ/886/102 ALMA obs. of 70um dark high-mass clumps (ASHES) (Sanhueza+, 2019)
The ALMA Survey of 70um dark High-mass clumps in Early Stages (ASHES).
I. Pilot survey: clump fragmentation.
Sanhueza P., Contreras Y., Wu B., Jackson J.M., Guzman A.E., Zhang Q.,
Li S., Lu X., Silva A., Izumi N., Liu T., Miura R.E., Tatematsu K.,
Sakai T., Beuther H., Garay G., Ohashi S., Saito M., Nakamura F., Saigo K.,
Veena V.S., Nguyen-Luong Q., Tafoya D.
<Astrophys. J., 886, 102 (2019)>
=2019ApJ...886..102S 2019ApJ...886..102S
ADC_Keywords: Infrared sources; Star Forming Region; Velocity dispersion;
Photometry, millimetric/submm
Keywords: Infrared dark clouds; Dust continuum emission; Star-forming regions;
Massive stars; Star formation
Abstract:
The ALMA Survey of 70µm dark High-mass clumps in Early Stages
(ASHES) is designed to systematically characterize the earliest stages
and constrain theories of high-mass star formation. Twelve massive
(>500M☉), cold (≤15K), 3.6-70µm dark prestellar clump
candidates, embedded in infrared dark clouds, were carefully selected
in the pilot survey to be observed with the Atacama Large
Millimeter/submillimeter Array (ALMA). We have mosaicked each clump
(∼1arcmin2) in continuum and line emission with the 12m, 7m, and
Total Power (TP) arrays at 224GHz (1.34mm), resulting in ∼1.2"
resolution (∼4800au, at the average source distance). As the first
paper in the series, we concentrate on the continuum emission to
reveal clump fragmentation. We detect 294 cores, from which 84 (29%)
are categorized as protostellar based on outflow activity or "warm
core" line emission. The remaining 210 (71%) are considered prestellar
core candidates. The number of detected cores is independent of the
mass sensitivity range of the observations and, on average, more
massive clumps tend to form more cores. We find a large population of
low-mass (<1M☉) cores and no high-mass (>30M☉) prestellar
cores (maximum mass 11M☉). From the prestellar core mass
function, we derive a power-law index of 1.17±0.10, which is
slightly shallower than Salpeter. We used the minimum spanning tree
(MST) technique to characterize the separation between cores and their
spatial distribution, and to derive mass segregation ratios. While
there is a range of core masses and separations detected in the
sample, the mean separation and mass per clump are well explained by
thermal Jeans fragmentation and are inconsistent with turbulent Jeans
fragmentation. Core spatial distribution is well described by
hierarchical subclustering rather than centrally peaked clustering.
There is no conclusive evidence of mass segregation. We test several
theoretical conditions and conclude that overall, competitive
accretion and global hierarchical collapse scenarios are favored over
the turbulent core accretion scenario.
Description:
For the ALMA Survey of 70µm dark High-mass clumps in Early Stages
(ASHES) pilot survey, 11 infrared dark cloud (IRDC) clumps were
selected from the Millimetre Astronomy Legacy Team 90GHz Survey
(MALT90; Foster+ 2011, J/ApJS/197/25 and 2013PASA...30...38F 2013PASA...30...38F ;
Jackson+ 2013PASA...30...57J 2013PASA...30...57J). MALT90 was built on the ATLASGAL 870um
catalogs (Schuller+ 2009A&A...504..415S 2009A&A...504..415S and Contreras+ 2013,
J/A+A/549/A45), from which a sample of 3246 high-mass clumps was
selected for follow-up in 16 spectral lines. Only 18 sources satisfy
all the selection conditions, and 11 were observed in this pilot
survey. The 12th target in the ASHES pilot survey is G028.273-00.167,
which is in the first quadrant and was not covered in MALT90. This
IRDC satisfies all requirements and has been well studied in the past
by Sanhueza+ (2012, J/ApJ/756/60 ; 2013ApJ...773..123S 2013ApJ...773..123S and
2017ApJ...841...97S 2017ApJ...841...97S).
Observations of the 12 IRDCs were carried out with ALMA on different
days during Cycle 3 (Project ID: 2015.1.01539.S; PI: Sanhueza) and a
resubmission for Cycle 4 (Project ID: 2016.1.01246.S; PI: Sanhueza).
The data sets consist of observations in band 6 (∼224GHz; 1.34mm) with
the main 12m array, the Atacama Compact 7m Array (ACA; Morita Array),
and the total power (TP).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 91 12 Physical properties of the prestellar,
high-mass clump candidates
table3.dat 67 301 Core parameters obtained from dendrograms
table4.dat 50 301 Calculated properties for the whole core sample
table5.dat 65 12 Overall properties per clump of
the embedded ALMA cores
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See also:
J/A+A/291/943 : Protostellar cores (Ossenkopf+, 1994)
J/A+A/430/137 : Close visual companions in Scorpius OB2 (Kouwenhoven+, 2005)
J/ApJ/641/389 : Millimetric observations of IRDC cores (Rathborne+, 2006)
J/ApJ/639/227 : MSX IRDC candidate catalog (Simon+, 2006)
J/ApJ/651/L125 : H2O masers associated with IR dark cloud cores (Wang+, 2006)
J/A+A/462/L17 : Dense cores in interstellar molecular clouds (Alves+, 2007)
J/A+A/505/405 : A catalogue of Spitzer dark clouds (Peretto+, 2009)
J/ApJS/197/25 : MALT90 pilot survey (Foster+, 2011)
J/A+A/530/A118 : G29.96-0.02 and G35.20-1.74 1mm and 3mm maps (Pillai+, 2011)
J/MNRAS/424/1925 : Spectrocopic Binarity of O and B type stars (Chini+, 2012)
J/ApJ/756/60 : A 3mm line survey in 37 IR dark clouds (Sanhueza+, 2012)
J/A+A/544/A146 : ATLASGAL cold high-mass clumps with NH3 (Wienen+, 2012)
J/A+A/549/A45 : ATLASGAL Compact Source Catalog: 330<l<21 (Contreras+, 2013)
J/ApJ/777/157 : 90GHz obs. of high-mass star-forming regions (Hoq+, 2013)
J/ApJS/209/2 : The BGPS. X. Dense molecular gas (Shirley+, 2013)
J/MNRAS/443/1555 : ATLASGAL massive star forming clump sample (Urquhart+, 2014)
J/ApJ/780/85 : Molecular line study of IR dark clouds (Vasyunina+, 2014)
J/A+A/565/A75 : ATLASGAL: dust condensations in Gal. plane (Csengeri+, 2014)
J/A+A/568/A41 : ATLASGAL Compact Source Catalog: 280<l<60 (Urquhart+, 2014)
J/A+A/577/A30 : SDC335.579-0.292 6, 8, 23 and 25GHz images (Avison+, 2015)
J/A+A/581/A119 : Starless gas clump IRDC 18310-4 images (Beuther+, 2015)
J/ApJ/815/130 : High-mass molecular clumps from MALT90 (Guzman+, 2015)
J/MNRAS/450/1926 : Infall motions in massive star-forming regions (He+, 2015)
J/A+A/584/A91 : Cat. of dense cores in Aquila from Herschel (Konyves+, 2015)
J/MNRAS/451/3089 : Young clumps embedded in IRDC (Traficante+, 2015)
J/A+A/579/A91 : ATLASGAL Galaxy massive cold dust clumps (Wienen+, 2015)
J/MNRAS/456/2041 : Fragmentation in filamentary mol. clouds (Contreras+ 2016)
J/A+A/592/A21 : Are infrared dark clouds really quiescent? (Feng+, 2016)
J/MNRAS/461/2288 : Infall motions in massive star-forming regions (He+, 2016)
J/other/PASA/33.30 : MALT90 Catalogue (Rathborne+, 2016)
J/ApJS/227/25 : 6 & 1.3cm deep VLA obs. toward high-mass SFRs (Rosero+, 2016)
J/ApJ/824/29 : ATLASGAL clumps with IRAS & MALT90 data (Stephens+, 2016)
J/A+A/599/A139 : ATLASGAL massive clumps dust characterization (Koenig+, 2017)
J/A+A/600/L10 : Massive cluster progenitors from ATLASGAL (Csengeri+, 2017)
J/AJ/154/140 : MALT90 kinematic dist. to molecular clumps (Whitaker+, 2017)
J/A+A/617/A89 : G328.2551-0.5321 ALMA images (Csengeri+, 2018)
J/A+A/615/A94 : ALMA massive protocluster gas clumps maps (Fontani+, 2018)
J/ApJS/237/27 : Radio Ammonia Mid-plane Survey pilot survey (Hogge+, 2018)
J/ApJ/867/94 : ALMA 1.3mm continuum flux data of C1-S core (Kong+, 2018)
J/ApJ/862/105 : Core mass function across Gal. env. II. (Liu+, 2018)
J/ApJS/243/13 : Massive star-forming clump from MALT90 (Li+, 2019)
J/A+A/622/A99 : Starless MDCs of NGC6334 molecular spectra (Louvet+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- AGAL IRDC clump designation (GLLL.lll+BB.bbb) (1)
17- 18 I2 h RAh Hour of right ascension (J2000) (2)
20- 21 I2 min RAm Minute of right ascension (J2000)
23- 27 F5.2 s RAs Second of right ascension (J2000)
29 A1 --- DE- Sign of declination (J2000) (2)
30- 31 I2 deg DEd Degree of declination (J2000) (2)
33- 34 I2 arcmin DEm Arcminute of declination (J2000)
36- 39 F4.1 arcsec DEs Arcsecond of declination (J2000)
41- 45 F5.1 km/s Vlsr [-87.8/80] LSR velocity of the gas
47- 50 F4.2 km/s sigma [0.56/3.04] Velocity dispersion (3)
52- 54 F3.1 kpc Dist [2.9/5.4] Distance used for clump selection
56- 59 F4.1 K Tdust [10.3/15] Dust temperature used for clump
selection
61- 64 I4 Msun Mset [580/5200] Mass used for clump selection
66- 68 A3 --- Ref Reference (4)
70- 73 F4.2 pc Rcl-pc [0.36/0.74] Clump radius in pc (5)
75- 76 I2 arcsec Rcl [19/37] Clump radius in arcsec (5)
78- 81 I4 Msun Mcl [520/3120] Clump mass (6)
83- 86 F4.2 g/cm2 Sigcl [0.1/1.1] Clump surface density
(Σcl=Mcl/πRcl2)
88- 91 F4.1 10+4cm-3 Vol [0.9/13] Volume density (7)
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Note (1): By replacing G in the IRDC name for AGAL, the name of the source has
the same nomenclature as in the ATLASGAL catalog
(Schuller+ 2009A&A...504..415S 2009A&A...504..415S).
Note (2): Phase center for ALMA mosaics. Due to the positioning of the mosaic,
the phase center and the ATLASGAL catalog coordinates are slightly
different in few arcsecs.
Note (3): Velocity dispersion was obtained using NH2D JKa,Kb=11,1-10,1_
emission for G028.273-00.167, HNC J=1-0 emission for G337.541-00.082
and G340.222-00.167, and N2H+ J=1-0 emission for the remaining
nine clumps. All three molecular tracers have critical densities
>105cm-3 (Sanhueza+ 2012, J/ApJ/756/60).
Note (4): Flag as follows:
a = Clump properties for G028.273-00.167, also known as G028.23-00.19,
were derived by Sanhueza+ (2012, J/ApJ/756/60 and 2013ApJ...773..123S 2013ApJ...773..123S).
b = Clump properties for G010.991-00.082 and G014.492-00.139 were
calculated using the column densities from Guzman+ (2015, J/ApJ/815/130)
and the distances derived according to Whitaker+ (2017, J/AJ/154/140).
c = Clump properties were derived and presented in a series of works by
the MALT90 team: Guzman+ (2015, J/ApJ/815/130 ; temperatures),
Rathborne+ (2016, J/other/PASA/33.30 ; Vlsr),
Contreras+ (2017MNRAS.466..340C 2017MNRAS.466..340C ; masses),
and Whitaker+ (2017, J/AJ/154/140 ; distances).
d = Due to multiple velocities along the line of sight, and based on the
C18O emission, the masses of G331.372-00.116 and G332.969-00.029
could be lower by ∼25% and ∼50%, respectively.
Note (5): Rcl was derived from Gaussian fitting to the dust continuum emission
from ATLASGAL.
Note (6): Mcl scaled from column Mass using the integrated flux derived in
the Gaussian fitting.
Note (7): The volume density was calculated assuming a spherical clump of
radius Rcl and using the molecular weight per hydrogen molecule
(µH2) of 2.8.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 -- AGAL IRDC Clump Name
17- 22 A6 -- Core ALMA Core Name (ALMANN within Clump or
EdgeN: see Note G1)
24- 25 I2 h RAh [15/18] Hour of Right Ascension (J2000)
27- 28 I2 min RAm [0/51] Minute of Right Ascension (J2000)
30- 34 F5.2 s RAs Second of Right Ascension (J2000)
36 A1 --- DE- [-] Sign of the Declination (J2000)
37- 38 I2 deg DEd [4/54] Degree of Declination (J2000)
40- 41 I2 arcmin DEm [8/48] Arcminute of Declination (J2000)
43- 46 F4.1 arcsec DEs Arcsecond of Declination (J2000)
48- 52 F5.2 mJy/beam F224GHz [0.2/14.8] Peak Flux;
primary beam corrected
54- 58 F5.2 mJy S224GHz [0.2/52.8] Integrated Flux;
primary beam corrected
60- 63 F4.2 arcsec Rad [0.27/2.46] Radius in arcsec
65 I1 -- Cl [0/3]? Core Classification (1)
67 I1 -- Edge [0/1] Core at edge of images are not used
for analysis (G1)
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Note (1): Core classification ranges from 0 to 3 as follows:
0 = prestellar candidate;
1 = only molecular outflow emission is detected;
2 = only warm core line emission is detected;
3 = both protostellar indicators are detected.
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Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 -- AGAL IRDC Clump Name
17- 22 A6 -- Core ALMA Core Name
24- 28 F5.2 Msun Mass [0.12/30.4] Core Mass
30- 33 I4 AU Radius [900/9670] Core calculated radius in au
35- 38 F4.1 10+6cm-3 nH2 [0.2/26.2] Core Volume Density
40- 43 F4.2 g/cm2 Sigma [0.08/4.78] Core Surface Density
45- 48 F4.2 10+23cm-2 NH2pk [0.12/9.52] Peak Column Density
50 I1 -- Edge Core at edge of images are not used
for analysis (G1)
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Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- AGAL IRDC Clump Name
17- 21 F5.3 Msun Sens [0.03/0.2] 1σ mass sensitivity
23- 24 I2 --- Nc [13/39] Number of cores
26- 29 F4.2 Msun b_Mass [0.1/1.5] Minimum core mass
31- 34 F4.1 Msun B_Mass [2.7/30.4] Maximum core mass
36- 39 F4.2 Msun Mass [0.87/5] Mean mass
41- 44 I4 au Rad [1810/4810] Mean radius
46- 48 F3.1 10+6cm-3 nH2 [0.6/9] Mean number density (n(H2))
50- 53 F4.2 g/cm2 Sig [0.18/1.7] Mean surface density (Σ)
55- 59 F5.2 10+22cm-2 NH2pk [2.1/16.4] Mean peak column density
(Npeak(H2))
61- 62 I2 --- Npre Number of prestellar cores
63 A1 --- --- [/]
64- 65 I2 --- Npro Number of protostellar cores
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Global notes:
Note (G1): Cores indicated with 0 are used in the analysis in Table 5
(and Section 5), while cores indicated with 1 (7 cores) are not used
because they locate near the edge of the images (properties are still
given here for completeness).
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History:
From electronic version of the journal
References:
Li et al. Paper II. 2020ApJ...903..119L 2020ApJ...903..119L
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 13-Apr-2021