J/A+A/692/A226 Cloud matching in M33. II. (Keilmann+, 2024)
Molecular cloud matching in CO and dust in M33.
II. Physical Properties of Giant Molecular Clouds.
Keilmann E., Kabanovic S., Schneider N., , Ossenkopf-Okada V., Stutzki J.,
Kobayashi M.I.N., Simon R., Buchbender C. Riechers D., Bigiel F.,
Tabatabaei F.
<Astron. Astrophys. 692, A226 (2024)>
=2024A&A...692A.226K 2024A&A...692A.226K (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, IR ; Interstellar medium ; Molecular clouds ;
Carbon monoxide
Keywords: dust, extinction - ISM: structure - Galaxy: general - galaxies: ISM -
Local Group - galaxies: star formation
Abstract:
Understanding the physical properties such as mass, size, and surface
mass density of giant molecular clouds or associations (GMCs/GMAs) in
galaxies is crucial for gaining deeper insights into the molecular
cloud and star formation (SF) processes. We determine these quantities
for the Local Group flocculent spiral galaxy M33 using Herschel dust
and archival 12CO(2-1) data from the IRAM 30m telescope, and compare
them to GMC/GMA properties of the Milky Way derived from CO literature
data. For M33, we apply the Dendrogram algorithm on a novel 2D
dust-derived NH2 map at an angular resolution of 18.2" and on the
12CO(2-1) data and employ an XCO factor map instead of a constant
value. Dust and CO-derived values are similar, with mean radii of
∼58pc for the dust and ∼68pc for CO, respectively. However, the
largest GMAs have a radius of around 150pc, similar to what was found
in the Milky Way and other galaxies, suggesting a physical process
that limits the size of GMAs. The less massive and smaller M33 galaxy
also hosts less massive and lower-density GMCs compared to the Milky
Way by an order of magnitude. Notably, the most massive (> a few
106M☉) GMC population observed in the Milky Way is mainly
missing in M33. The mean surface mass density of M33 is significantly
smaller than that of the Milky Way and this is attributed to higher
column densities of the largest GMCs in the Milky Way, despite similar
GMC areas. We find no systematic gradients in physical properties with
the galactocentric radius in M33. However, surface mass densities and
masses are higher near the center, implying increased SF activity. In
both galaxies, the central region contains ∼30% of the total molecular
mass. The index of the power-law spectrum of the GMC masses across the
entire disk of M33 is alpha=2.3±0.1 and alpha=1.9±0.1 for dust-
and CO-derived data, respectively. We conclude that GMC properties in
M33 and the Milky Way are largely similar, though M33 lacks high-mass
GMCs, for which there is no straightforward explanation. Additionally,
GMC properties are only weakly dependent on the galactic environment,
with stellar feedback playing a role that needs further investigation.
Description:
The total hydrogen column density map was derived using Herschel flux
maps in the wavelength range from 160 to 500 micron and has a spatial
resolution of 18.2 arcsec.
The molecular hydrogen column density map has been produced
subtracting the HI component. In contrast to Paper I (Keilmann et al.
2024A&A...688A.171K 2024A&A...688A.171K, Cat. J/A+A/688/A171), here the HI map has
short-spacing corrections.
The kappa0 map is the dust absorption coefficient of the dust
opacity model derived using HI data and the Herschel 250 micron map
(SPIRE). The Xco conversion factor map has been derived using the
molecular hydrogen column density map and the IRAM 30m CO map.
Objects:
-----------------------------------------
RA (2000) DE Designation(s)
-----------------------------------------
01 33 50.89 +30 39 36.6 M33 = NGC 598
-----------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 105 326 GMC properties derived from the Dendrogram
leaves in dust
table2.dat 138 199 GMC properties derived from the Dendrogram
leaves in CO
list.dat 159 4 List of fits maps
fits/* . 4 Individual fits maps
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See also:
J/A+A/688/A171 : Cloud matching in M33. I. (Keilmann+, 2024)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- ID Identification number
5- 26 F22.16 arcsec Xpos X position offset (G1)
28- 49 F22.16 arcsec Ypos Y position offset (G1)
51- 56 I6 pc2 Area Area
58- 60 I3 pc Rad Radius
62- 68 I7 Msun Mass Mass
70- 71 I2 cm-3 Dens Density
73- 75 I3 Msun/pc2 SMD Surface mass density
77- 95 F19.15 K/cm3 Pres Pressure
97-100 F4.2 --- Elong Elongation
102-105 F4.1 K Temp Temperature
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- ID Identification number
5- 26 F22.16 arcsec Xpos X position offset (G1)
28- 49 F22.16 arcsec Ypos Y position offset (G1)
51- 56 I6 pc2 Area Area
58- 60 I3 pc Rad Radius
62- 83 E22.17 cm-2/(K.km/s) XCO XCO conversion factor
85- 91 I7 Msun Mass Mass
93- 94 I2 cm-3 Dens Density
96- 98 I3 Msun/pc2 SND Surface mass density
100-119 F20.16 K/cm3 Pres Pressure
121-124 F4.2 --- Elong Elongation
126-129 F4.1 K Temp Temperature
131-138 F8.1 K.km/s/pc2 LCO CO luminosity
--------------------------------------------------------------------------------
Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 23 I4 --- Nx Number of pixels along X-axis
25- 28 I4 --- Ny Number of pixels along Y-axis
30- 50 A21 "datime" Obs.Date Observation date
52- 56 I5 Kibyte size Size of FITS file
58- 89 A32 --- FileName Name of FITS file, in subdirectory fits
91-159 A69 --- Title Title of the FITS file
--------------------------------------------------------------------------------
Global notes:
Note (G1): The offsets, x and y, are calculated regarding the center position of
M33 of RA(2000)=01:33:50.62 and Dec.(2000)=30:39:46.45.
--------------------------------------------------------------------------------
Acknowledgements:
Eduard Keilmann, keilmann(at)ph1.uni-koeln.de
References:
Keilmann et al. Paper I 2024A&A...688A.171K 2024A&A...688A.171K, Cat. J/A+A/688/A171
(End) Patricia Vannier CDS 13-Nov-2024