J/ApJ/894/L14 ALMA obs. of massive clouds in the CMZ (Lu+, 2020)
ALMA observations of massive clouds in the Central Molecular Zone: Jeans
fragmentation and cluster formation.
Lu X., Cheng Y., Ginsburg A., Longmore S.N., Kruijssen J.M.D.,
Battersby C., Zhang Q., Walker D.L.
<Astrophys. J., 894, L14-14 (2020)>
=2020ApJ...894L..14L 2020ApJ...894L..14L (SIMBAD/NED BibCode)
ADC_Keywords: Galactic center; Star Forming Region; Molecular clouds;
Millimetric/submm sources
Keywords: Galactic center; Star formation; Molecular clouds
Abstract:
We report Atacama Large Millimeter/submillimeter Array (ALMA) Band 6
continuum observations of 2000au resolution toward four massive
molecular clouds in the Central Molecular Zone of the Galaxy. To study
gas fragmentation, we use the dendrogram method to identify cores as
traced by the dust continuum emission. The four clouds exhibit
different fragmentation states at the observed resolution despite
having similar masses at the cloud scale (∼1-5pc). Assuming a constant
dust temperature of 20K, we construct core mass functions of the
clouds and find a slightly top-heavy shape as compared to the
canonical initial mass function, but we note several significant
uncertainties that may affect this result. The characteristic spatial
separation between the cores as identified by the minimum spanning
tree method, ∼104au, and the characteristic core mass, 1-7M☉,
are consistent with predictions of thermal Jeans fragmentation. The
three clouds showing fragmentation may be forming OB associations
(stellar mass ∼103M☉). None of the four clouds under
investigation seem to be currently able to form massive star clusters
like the Arches and the Quintuplet (≳104M☉), but they may
form such clusters by further gas accretion onto the cores.
Description:
Our Atacama Large Millimeter/submillimeter Array (ALMA) observations
targeted selected regions in four Central Molecular Zone (CMZ)
star-forming clouds: the 20km/s cloud, the 50km/s cloud, Sgr B1-off
(also known as Dust Ridge clouds e/f), and Sgr C.
The data were taken in the C43-5 and C43-3 configurations (project
code: 2016.1.00243.S), and were calibrated separately and then imaged
together. The correlators were set to cover frequencies between
217-221GHz and 231-235GHz.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb1.dat 65 834 The full core catalog in the three clouds
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See also:
J/A+A/291/943 : Protostellar cores (Ossenkopf+, 1994)
J/ApJ/789/115 : The Quintuplet cluster astrometry & photometry (Stolte+, 2014)
J/ApJ/853/171 : mm point sources in the extended Sgr B2 cloud (Ginsburg+, 2018)
J/AJ/156/18 : Binary companions of evolved stars (Price-Whelan+, 2018)
J/ApJ/862/105 : Core mass function across Gal. env. II. IR clumps (Liu+, 2018)
J/ApJS/244/35 : VLA observations of the Central Molecular Zone (Lu+, 2019)
J/ApJ/886/102 : ALMA obs. of 70um dark high-mass clumps (Sanhueza+, 2019)
J/A+A/635/A2 : NGC6334 ALMA 87.6GHz continuum emission map (Sadaghiani+, 2020)
Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Cloud Cloud (1)
10- 12 I3 --- Seq [1/471] Core number within Cloud
14- 15 I2 h RAh [17] Hour of Right Ascension (J2000)
17- 18 I2 min RAm [44/46] Minute of Right Ascension (J2000)
20- 24 F5.2 s RAs Second of Right Ascension (J2000)
26 A1 --- DE- [-] Sign of the Declination (J2000)
27- 28 I2 deg DEd [28/29] Degree of Declination (J2000)
30- 31 I2 arcmin DEm Arcminute of Declination (J2000)
33- 37 F5.2 arcsec DEs Arcsecond of Declination (J2000)
39- 42 I4 au Rad [1028/8158] Radius
44- 49 F6.2 mJy Flux [0.19/202] Flux
51- 56 F6.2 Msun Mass [0.29/304] Core mass
58- 65 E8.2 cm-3 n [2.8e+06/2.8e+08] Number density
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Note (1): The Central Molecular Zone (CMZ) cloud names (Table 1;
Lu+ 2019ApJ...872..171L 2019ApJ...872..171L and 2019, J/ApJS/244/35) as follows:
c20kms = 20 km/s cloud (471 occurrences);
sgrb1off = Sgr B1-off (also known as Dust Ridge clouds e/f; 89 occurrences);
sgrc = Sgr C cloud (274 occurrences).
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 21-Sep-2021