J/ApJ/903/111 HCN, HNC, H13CN & HC3N of Galactic Center map. II. (Tanaka+, 2020)
HCN J=4-3, HNC J=1-0, H13CN J=1-0, and HC3N J=10-9 maps of Galactic Center
region.
II. Physical properties of dense-gas clumps and probability of star formation.
Tanaka K., Nagai M., Kamegai K., Iino T., Sakai T.
<Astrophys. J., 903, 111 (2020)>
=2020ApJ...903..111T 2020ApJ...903..111T
ADC_Keywords: Galactic center; Molecular clouds; Star Forming Region;
Photometry, millimetric/submm
Keywords: Star formation ; Galactic center ; Molecular clouds
Abstract:
We report a statistical analysis exploring the origin of the overall
low star formation efficiency (SFE) of the Galactic central molecular
zone (CMZ) and the SFE diversity among the CMZ clouds using a
wide-field HCN J=4-3 map, whose optically thin critical density
(∼107/cm3) is the highest among the tracers ever used in CMZ
surveys. Logistic regression is performed to empirically formulate
star formation probability of 195 HCN clumps, 13 of which contain star
formation signatures. The explanatory parameters in the best-fit model
are reduced into the virial parameter αvir without significant
contribution from other parameters, whereas the performance of the
model without αvir is no better than that using randomly
generated data. The threshold αvir is 6, which translates into
a volume density (nH2) of 104.6/cm3 with the
nH2-αvir correlation. The scarcity of the low-αvir
clumps, whose fraction to all HCN clumps is 0.1, can be considered as
one of the immediate causes of the suppressed SFE. No correlation
between the clump size or mass and star formation probability is
found, implying that HCN J= 4-3 does not immediately trace the mass of
star-forming gas above a threshold density. Meanwhile, star-forming
and non-star-forming clouds are degenerate in the physical parameters
of the CS J=1-0 clouds, highlighting the efficacy of the HCN J=4-3
line to probe star-forming regions in the CMZ. The timescale of the
high-αvir to low-αvir transition is ≲2Myr, which is
consistent with the tidal compression and X1/X2 orbit transition
models but possibly does not fit the cloud-cloud collision picture.
Description:
The HCN J=4-3 data were obtained in 2010-2013 utilizing the CATS345
receiver installed on the Atacama Submillimeter Telescope Experiment
(ASTE) 10m telescope. The H13CN J=1-0, HNC J=1-0, and HC3N J=10-9
data were simultaneously taken with the BEARS receiver array of the
Nobeyama Radio Observatory (NRO) 45m telescope in 2010.
We also use the results of the excitation analysis in Paper I
(Tanaka+, 2018ApJS..236...40T 2018ApJS..236...40T).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 104 195 HCN clumps
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See also:
VIII/96 : 6-GHz methanol multibeam maser catalogue (Caswell+, 2010-12)
VII/114 : Massachusetts-Stony Brook Galactic Plane CO Survey (Clemens+ 1986)
J/ApJ/428/693 : Rosette Nebula and Maddalena Cloud structures (Williams+ 1994)
J/A+A/432/369 : Leiden Atomic and Molecular Database (LAMDA) (Schoeier+, 2005)
J/A+A/455/971 : Organic molecules in Galactic center (Requena-Torres+, 2006)
J/ApJS/182/131 : Molecular clouds and clumps in the GRS (Rathborne+, 2009)
J/ApJ/702/178 : YSOs in the central 400pc of the Galaxy (Yusef-Zadeh+, 2009)
J/ApJ/723/492 : Physical properties GRS molecular clouds (Roman-Duval+, 2010)
J/MNRAS/416/1764 : H2O Southern Galactic Plane Survey (HOPS) (Walsh+, 2011)
J/A+A/563/A68 : CH3OH and H2O Galactic center masers (Chambers+, 2014)
J/MNRAS/443/1555 : ATLASGAL mass star forming clumps sample (Urquhart+, 2014)
J/MNRAS/453/4264 : JCMT Plane Survey: l=30° field (Moore+, 2015)
J/A+A/586/A50 : Central Molecular Zone H2CO temperature maps (Ginsburg+, 2016)
J/ApJ/872/121 : Molecular cloud cores in the GC 50km/s cloud (Uehara+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Clump [1/195] Clump ID
5- 11 F7.3 deg GLON [0/360] Galactic Longitude
13- 18 F6.3 deg GLAT [-0.26/0.08] Galactic Latitude
20- 23 I4 km/s VLSR [-174/136] LSR Velocity
25- 28 F4.2 pc MajAxis [0.04/2.09]? Semi Major Axis Length
30- 33 F4.2 pc MinAxis [0.03/1.33]? Semi Minor Axis Length
35- 37 I3 deg PA [0/359]? Position Angle
39- 42 F4.1 km/s Delv [2.9/51.7]? Velocity FWHM
44- 48 F5.1 K.km/s IHCN43 [1.4/244] HCN 4-3 Integrated Intensity
50- 56 F7.2 K.km/s IH13CN [0.37/65.9]? H13CN 1-0 Integrated Intensity
58- 63 F6.2 K.km/s IHNC [0.09/33.6]? HNC 1-0 Integrated Intensity
65- 70 F6.2 K.km/s IHC3N [0.04/51.5]? HC3N 10-9 Integrated Intensity
72- 74 F3.1 [Msun] Mass [0.6/4.1]? Clump Mass
76- 78 F3.1 [-] alpVT [0.2/3.4]? Virial Parameter
80- 82 F3.1 [/cm3] nH2 [3.6/4.7]? Hydrogen Volume Density
84- 86 F3.1 [K] Tkin [1.8/2.5]? Gas Kinetic Temperature
88- 90 A3 --- SF Star Formation flags (1)
92-104 A13 --- Note Additional note(s)
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Note (1): Flags as follows:
g = extended green object (5 occurrences)
w = water maser (6 occurrences)
m = class-II methanol maser (1 occurrence)
H = cluster-forming region (1 occurrence)
mw = class-II methanol maser and water maser (3 occurrences)
mgw = extended green object, class-II methanol maser and water maser
(1 occurrence)
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History:
From electronic version of the journal
References:
Tanaka et al. Paper I : 2018ApJS..236...40T 2018ApJS..236...40T
(End) Prepared by [AAS], Coralie Fix [CDS], 07-Feb-2022