J/MNRAS/483/5135 M33 dust-selected molecular cloud catalogue (Williams+, 2019)
A high-resolution, dust-selected molecular cloud catalogue of M33, the
Triangulum Galaxy.
Williams T.G., Gear W.K., Smith M.W.L.
<Mon. Not. R. Astron. Soc., 483, 5135-5149 (2019)>
=2019MNRAS.483.5135W 2019MNRAS.483.5135W (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies ; Interstellar medium ; Millimetric/submm sources ;
Photometry, millimetric/submm
Keywords: galaxies: individual: M33 - galaxies: ISM - galaxies: structure -
submillimetre: galaxies - submillimetre: ISM
Abstract:
We present a catalogue of Giant Molecular Clouds (GMCs) in M33,
extracted from cold dust continuum emission. Our GMCs are identified
by computing dendrograms. We measure the spatial distribution of these
clouds, and characterize their dust properties. Combining these
measured properties with CO(J=2-1) and 21cm HI data, we calculate the
gas-to-dust ratio (GDR) of these clouds, and from this compute a total
cloud mass. In total, we find 165 GMCs with cloud masses in the range
of 104-107M☉. We find that radially,
log10(GDR)=-0.043(±0.038)R[kpc]+1.88(±0.15), a much lower GDR
than found in the Milky Way, and a correspondingly higher αCO
factor. The mass function of these clouds follows a slope proportional
to M-2.84, steeper than many previous studies of GMCs in local
galaxies, implying that M33 is poorer at forming massive clouds than
other nearby spirals. While we can rule out interstellar pressure as
the major contributing factor, we are unable to disentangle the
relative effects of metallicity and HI velocity dispersion. We find a
reasonably featureless number density profile with galactocentric
radius, and weak correlations between galactocentric radius and dust
temperature/mass. These clouds are reasonably consistent with Larson's
scaling relationships, and many of our sources are co-spatial with
earlier CO studies. Massive clouds are identified at large
galactocentric radius, unlike in these earlier studies, perhaps
indicating a population of CO-dark gas dominated clouds at these
larger distances.
Description:
Our first source of FIR/sub-mm data comes from the Herschel Space
Observatory. We make use of observations taken as part of the Herschel
M33 extended survey (HerM33es; Kramer et al. 2010A&A...518L..67K 2010A&A...518L..67K),
which mapped a 70arcmin2 region around M33. Data at 100 and 160µm
were taken with the Photoconductor Array Camera and Spectrometer
(PACS; Poglitsch et al. 2010A&A...518L...2P 2010A&A...518L...2P), with beam sizes of 7.7
and 12arcsec, respectively.
HerM33es simultaneously used the Spectral and Photometric Imaging
Receiver (SPIRE; Griffin et al. 2010A&A...518L...3G 2010A&A...518L...3G) aboard Herschel,
which mapped M33 at 250, 350, and 500µm with a resolution of 18,
25, and 36arcsec, respectively.
Archival SCUBA-2 observations of M33 at 450 and 850µm were taken
between 2012-07-01 and 2012-07-12, consisting of ∼7h of PONG1800
(which maps a roughly circular, 30arcmin field) observations of M33,
and ∼4h of smaller, CV DAISY (constant velocity, small field of view)
observations.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb1.dat 93 165 Leaf node parameters for the GMCs
tablec1.dat 63 165 Calculated dust and gas properties for the GMCs
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Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- ID [0/164] Giant Molecular Cloud identifier
5- 6 I2 h RAh Right ascension (J2000)
8- 9 I2 min RAm Right ascension (J2000)
11- 14 F4.1 s RAs Right ascension (J2000)
16 A1 --- DE- Declination sign (J2000)
17- 18 I2 deg DEd Declination (J2000)
20- 21 I2 arcmin DEm Declination (J2000)
23- 26 F4.1 arcsec DEs Declination (J2000)
28- 30 F3.1 kpc R Deprojected distance from the centre of M33
(01h33m50.9s +30°39'37"; Plucinsky et al.
2008ApJS..174..366P 2008ApJS..174..366P, Cat. J/ApJS/174/366)
32- 34 I3 pc FWHM FWHM of the cloud
36- 40 F5.2 Jy S100 Flux density at 100um
42- 45 F4.2 Jy e_S100 Error on S100 (G1)
47- 51 F5.2 Jy S160 Flux density at 160um
53- 56 F4.2 Jy e_S160 Error on S160 (G1)
58- 62 F5.2 Jy S250 Flux density at 250um
64- 67 F4.2 Jy e_S250 Error on S250 (G1)
69 A1 --- l_S450 Limit flag for 3σ limit on S450
70- 74 F5.3 Jy S450 Flux density at 450um
76- 80 F5.3 Jy e_S450 ? Error on S450 (G1)
82 A1 --- l_S850 Limit flag for 3σ limit on S850
83- 87 F5.3 Jy S850 Flux density at 850um
89- 93 F5.3 Jy e_S850 ? Error on S850 (G1)
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Byte-by-byte Description of file: tablec1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- ID [0/164] Giant Molecular Cloud identifier
5- 9 F5.2 K T Dust temperature (G1)
11- 14 F4.2 K e_T Error on T (G1)
16- 19 F4.2 [Msun] logMdust Dust mass (G1)
21- 24 F4.2 [Msun] e_logMdust Error on Mdust (G1)
26- 29 F4.2 [Lsun] logLTIR Total infrared luminosity (G1)
31- 34 F4.2 [Lsun] e_logLTIR Error on LTIR (G1)
36 A1 --- l_LCO Limit flag for 3σ limit on LCO
37- 44 E8.5 K.km/s LCO CO(J=2-1) luminosity
46- 52 E7.3 K.km/s e_LCO ?=- Error on LCO (G1)
54 A1 --- l_NHI Limit flag for 3σ limit on NHI
55- 58 F4.2 Msun/pc2 NHI HI surface density
60- 63 F4.2 Msun/pc2 e_NHI ?=- Error on NHI (G1)
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General Notes:
Note (G1): Errors given are 1σ errors.
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 03-Aug-2022