J/MNRAS/517/632 WISDOM Proj XII ALMA CO(2-1) of clumps and clouds (Liu+, 2022)
WISDOM Project - XII. Clump properties and turbulence regulated by
clump-clump collisions in the dwarf galaxy NGC 404.
Liu L., Bureau M., Li G.-X., Davis T.A., Nguyen D.D., Liang F.-H., Choi W.,
Smith M.R., Iguchi S.
<Mon. Not. R. Astron. Soc. 517, 632-656 (2022)>
=2022MNRAS.517..632L 2022MNRAS.517..632L (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, dwarf ; Interferometry ; Spectroscopy ; Photometry ;
Millimetric/submm sources ; Radio lines ; Carbon monoxide ;
Molecular data ; Molecular clouds ; Positional data ;
Radial velocities ; Velocity dispersion
Keywords: galaxies: dwarf - galaxies: individual: NGC 404 - galaxies: ISM -
galaxies: nuclei - radio lines: ISM
Abstract:
We present a study of molecular structures (clumps and clouds) in the
dwarf galaxy NGC 404 using high-resolution (∼0.86 * 0.51 pc2)
Atacama Large Millimeter/sub-millimeter Array 12CO(2-1)
observations. We find two distinct regions in NGC 404: a
gravitationally stable central region (Toomre parameter Q = 3-30) and
a gravitationally unstable molecular ring (Q ≲ 1). The molecular
structures in the central region have a steeper size-linewidth
relation and larger virial parameters than those in the molecular
ring, suggesting gas is more turbulent in the former. In the molecular
ring, clumps exhibit a shallower mass-size relation and larger virial
parameters than clouds, implying density structures and dynamics are
regulated by different physical mechanisms at different spatial
scales. We construct an analytical model of clump-clump collisions to
explain the results in the molecular ring. We propose that clump-clump
collisions are driven by gravitational instabilities coupled with
galactic shear, which lead to a population of clumps whose
accumulation lengths (i.e. average separations) are approximately
equal to their tidal radii. Our model-predicted clump masses and sizes
(and mass-size relation) and turbulence energy injection rates (and
size-linewidth relation) match the observations in the molecular ring
very well, suggesting clump-clump collisions are the main mechanism
regulating clump properties and gas turbulence in that region. As
expected, our collision model does not apply to the central region,
where turbulence is likely driven by clump migration.
Description:
In this paper, we perform statistical analyses of the multiple-scale
molecular structures of the dwarf lenticular galaxy NGC 404,
exploiting high-spatial resolution ALMA 12CO(2-1) observations
around 230 GHz (see details on observations in Davis et al.
2020MNRAS.496.4061D 2020MNRAS.496.4061D and ALMA archive data
https://almascience.eso.org/aq/). The results are confronted with a
new simple analytical model of clump-clump collisions, and a good
explanation of the observational results in the molecular ring of NGC
404 is achieved (i.e section Introduction). The ALMA CO(2-1)
observations reveal a complex molecular gas morphology as shown in
intensity map figure 1 of the section 2.
As described in section 2.3, for structural decomposition we use the
dendrogram code astrodendro to identify molecular structures and a 3D
mask of bright emission is initially created using the code cpropstoo.
A hierarchy of molecular structures is then identified using the code
astrodendro and their properties are computed with cpropstoo.
Cpropstoo is chosen to correct the measured quantities for the finite
sensitivity of the observations, extrapolating sizes, linewidths, and
luminosities to their infinite signal-to-noise ratio (S/N)
equivalents. Cpropstoo also 'deconvolves' in two dimensions the
measured (and extrapolated) sizes, to account for the finite size of
the synthesized beam, thus roughly correcting for possible resolution
biases. The table1.dat lists positions, structure size radius,
linewidth, CO(2-1) luminosity, gaseous mass and stucture types. For a
detailed definition of each property and its uncertainty, refer to Liu
et al. (2021MNRAS.505.4048L 2021MNRAS.505.4048L, Cat. J/MNRAS/505/4048) (see also section
3 & 4 for clump-clump collision model).
Objects:
----------------------------------------------------------------------------
RA (2000) DE Designation(s)
----------------------------------------------------------------------------
01 09 27.02 +35 43 05.2 NGC 404 = 2MASX J01092707+3543046
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 90 3626 *Properties of the dendrogram-defined structures
of NGC 404
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Note on table1.dat: We refer to single centrally concentrated structures as
'clumps', and those objects with more complex structures as 'clouds'.
Therefore, we treat dendrogram-defined leaves as clumps, and both branches
and trunks as clouds, because by definition leaves cannot contain any
substructure, while both branches and trunks must harbour multiple
substructures. Here, 'substructure' is understood to be emission within a
contour (in a 3D data cube) of δmin = 1.5σrms that has a
minimum area of one synthesized beam. the subscript 'c' will denote both
clumps and clouds while the subscripts 'clump' and 'cloud' will refer to
only clumps and only clouds, respectively.
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See also:
J/MNRAS/505/4048 : WISDOM Project IX study of GMCs in NGC 4429 (Liu+, 2021)
J/MNRAS/431/1752 : ATLASGAL 6.7GHz methanol masers (Urquhart+, 2013)
J/ApJ/921/130 : Local analogs to high-redshift galaxies. I.
(Motino Flores+, 2021)
J/ApJ/901/L8 : Molecular gas properties of 70 PHANGS-ALMA galaxies
(Sun+, 2020)
J/ApJ/897/89 : 1482 Gaussian clumps in the Central Molecular Zone
(Li+, 2020)
J/ApJ/876/141 : ALMA obs. of giant molecular clouds in Hen 2-10
(Imara+, 2019)
J/ApJ/860/172 : Cloud-scale molecular gas properties in 15 galaxies
(Sun+, 2018)
J/ApJ/835/278 : Molecular clouds in the dwarf galaxy NGC6822 (Schruba+,2017)
J/ApJ/834/57 : Milky Way molecular clouds from 12CO
(Miville-Deschenes+, 2017)
J/ApJ/821/125 : SMA obs. of giant molecular clouds in NGC 300 (Faesi+, 2016)
J/ApJ/803/16 : Giant molecular clouds in NGC4526 based on 12CO
(Utomo+, 2015)
J/ApJ/784/3 : The PAWS catalogs of GMCs and islands in M51 (Colombo+,2014)
J/ApJ/772/107 : Giant molecular clouds in nearby galaxies
(Donovan Meyer+, 2013)
J/ApJ/723/492 : Physical properties of GRS molecular clouds
(Roman-Duval+, 2010)
J/A+A/645/A97 : ALMA cube and GMC catalog of J1023+1952 (Querejeta+, 2021)
J/A+A/585/A117 : N131 bubble CO integrated intensity maps (Zhang+, 2016)
J/ApJS/197/16 : CO observations of LMC molecular clouds (MAGMA).
(Wong+, 2011)
J/AJ/157/241 : HI clouds in LITTLE THINGS dwarf irregular galaxies
(Hunter+, 2019)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- ID Identifier structure raw number (ID)
6- 7 I2 h RAh Right Ascension (J2000)
9- 10 I2 min RAm Right Ascension (J2000)
12- 15 F4.1 s RAs Right Ascension (J2000)
17 A1 --- DE- Declination sign (J2000)
18- 19 I2 deg DEd Declination (J2000)
21- 22 I2 arcmin DEm Declination (J2000)
24- 27 F4.1 arcsec DEs [] Declination (J2000)
29- 34 F6.1 km/s VLSR The Local Standard of Rest LSR
velocity (VLSR)
36- 40 F5.2 pc Rc The structure size radius (Rc) (1)
42- 46 F5.2 pc e_Rc Mean uncertainty of Rc (δRc)
(5)
48- 52 F5.2 km/s sigma The one-dimensional observed
linewidth velocity dispersion
(σobs,loc)
54- 58 F5.2 km/s e_sigma Mean uncertainty of sigma
(δσobs,loc) (5)
60- 65 F6.2 10+4K.km/s.pc2 LCO(2-1) The CO(2-1) luminosity LCO(2-1)
(L_CO (2-1)_)
67- 71 F5.2 10+4K.km/s.pc2 e_LCO(2-1) Mean uncertainty of LCO(2-1)
(δL_CO (2-1)_) (5)
73- 77 F5.2 10+5Msun Mc The gaseous mass (Mc) (2)
79- 83 F5.2 10+5Msun e_Mc Mean uncertainty of Mc (δMc)
(5)
85- 88 F4.1 pc Rg Deprojected galactocentric distance
(Rgal) (3)
90 A1 --- Type Structure codes (Structure) (4)
--------------------------------------------------------------------------------
Note (1): Measurements of Rc assume parameter value η equal to 1.91.
Note (2): Measurements of Mc assume a CO(2-1)/CO(1-0) line ratio of 0.78 in
temperature units and a standard Galactic CO-to-H2 conversion factor
XCO = 2*1020cm-2 (K.km/s) including the mass contribution from
helium (i.e refer to Mgas in Liu et al. 2021MNRAS.505.4048L 2021MNRAS.505.4048L,
Cat. J/MNRAS/505/4048).
Note (3): Measurements of Rgal adopt a fixed position angle PA = 1° and
inclination angle i = 9.3°.
Note (4): Structure codes are as follows:
B = Branch type structure, 1642 cases in our sample
T = Trunk type structure, 50 cases in our sample
L = Leaf type structure, 1934 cases in our sample, which have
deconvolved diameters larger than or equal to the synthesized
beam in two dimensions and deconvolved velocity widths at least
half of one velocity channel (i.e Donovan Meyer et al.
2013ApJ...772..107D 2013ApJ...772..107D, Cat. J/ApJ/772/107).
More, the figure 2 in section 2.3 Structural decomposition, shows
the resolved leaves (blue ellipses) and and trunks (coloured
contours) of NGC404 overlaid on the zeroth-moment map created with
the cpropstoo-generated mask.
Note (5): The uncertainties of the measured properties are estimated via a
bootstrapping technique. More, the uncertainty of the adopted
distance D to NGC 404 was not propagated through these tabulated
uncertainties because an error on the distance to NGC404 translates
to a systematic (rather than random) scaling of some of the measured
quantities (no effect on the others) (i.e Rc ∝ D,
LCO(2-1) ∝ D2, Mc ∝ D2 and
Rgal ∝ D).
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History:
From electronic version of the journal
References:
Onishi et al. Paper I 2017MNRAS.468.4663O 2017MNRAS.468.4663O
Davis et al. Paper II 2017MNRAS.468.4675D 2017MNRAS.468.4675D
Davis et al. Paper III 2018MNRAS.473.3818D 2018MNRAS.473.3818D
Smith et al. Paper IV 2019MNRAS.485.4359S 2019MNRAS.485.4359S
North et al. Paper V 2019MNRAS.490..319N 2019MNRAS.490..319N
Smith et al. Paper VI 2021MNRAS.500.1933S 2021MNRAS.500.1933S
Smith et al. Paper VII 2021MNRAS.503.5984S 2021MNRAS.503.5984S
North et al. Paper VIII 2021MNRAS.503.5179N 2021MNRAS.503.5179N
Liu et al. Paper IX 2021MNRAS.505.4048L 2021MNRAS.505.4048L, Cat. J/MNRAS/505/4048
Davis et al. Paper X 2022MNRAS.512.1522D 2022MNRAS.512.1522D
Lu et al. Paper XI 2022MNRAS.514.5035L 2022MNRAS.514.5035L
Liu et al. Paper XII 2022MNRAS.517..632L 2022MNRAS.517..632L
Lelli et al. Paper XIII 2022MNRAS.516.4066L 2022MNRAS.516.4066L
Ruffa et al. Paper XIV 2023MNRAS.522.6170R 2023MNRAS.522.6170R
Choi et al. Paper XV 2023MNRAS.522.4078C 2023MNRAS.522.4078C
Elford et al. Paper XVI 2024MNRAS.528..319E 2024MNRAS.528..319E
Williams et al. Paper XVII 2023MNRAS.525.4270W 2023MNRAS.525.4270W
Liang et al. Paper XVIII 2024MNRAS.527.9343L 2024MNRAS.527.9343L
Zhang et al. Paper XIX 2024MNRAS.530.3240Z 2024MNRAS.530.3240Z
Lu et al. Paper XX 2024MNRAS.531.3888L 2024MNRAS.531.3888L
Choi et al. Paper XXI 2024MNRAS.531.4045C 2024MNRAS.531.4045C
Zhang et al. Paper XXII 2025MNRAS.537..520Z 2025MNRAS.537..520Z
Lu et al. Paper XXIII 2025MNRAS.540...71L 2025MNRAS.540...71L
Liu et al. Paper XXIV 2025MNRAS.541.3081L 2025MNRAS.541.3081L
Zhang et al. Paper XXV 2025MNRAS.541.2540Z 2025MNRAS.541.2540Z
Dominiak et al. Paper XXVI 2025MNRAS.542.2039D 2025MNRAS.542.2039D
(End) Luc Trabelsi [CDS] 15-Sep-2025