J/A+A/601/A146 M33 molecular clouds and young stellar clusters (Corbelli+, 2017)
From molecules to young stellar clusters: the star formation cycle across the
disk of M33.
Corbelli E., Braine J., Bandiera R., Brouillet N., Combes F., Druard C.,
Gratier P., Mata J., Schuster K., Xilouris M., Palla F.
<Astron. Astrophys. 601, A146 (2017)>
=2017A&A...601A.146C 2017A&A...601A.146C (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Molecular clouds ; Interstellar medium ;
Carbon monoxide
Keywords: galaxies: individual: M33 - galaxies: star formation -
galaxies: ISM - infrared: ISM - ISM: molecules
Abstract:
We study the association between giant molecular clouds (GMCs) and
young stellar cluster candidates (YSCCs) to shed light on the time
evolution of local star formation episodes in the nearby galaxy
M33.
The CO (J=2-1) IRAM all-disk survey was used to identify and
classify 566 GMCs with masses between 2x104 and 2x106M☉
across the whole star-forming disk of M33. In the same area, there
are 630 YSCCs that we identified using Spitzer-24um data. Some YSCCs
are embedded star-forming sites, while the majority have GALEX-UV and
Hα counterparts with estimated cluster masses and ages.
The GMC classes correspond to different cloud evolutionary stages:
inactive clouds are 32% of the total and classified clouds with
embedded and exposed star formation are 16% and 52% of the total,
respectively. Across the regular southern spiral arm, inactive clouds
are preferentially located in the inner part of the arm, possibly
suggesting a triggering of star formation as the cloud crosses the
arm. The spatial correlation between YSCCs and GMCs is extremely
strong, with a typical separation of 17pc. This is less than half the
CO (2-1) beam size and illustrates the remarkable physical link
between the two populations. GMCs and YSCCs follow the HI filaments,
except in the outermost regions, where the survey finds fewer GMCs
than YSCCs, which is most likely due to undetected clouds with low CO
luminosity. The distribution of the non-embedded YSCC ages peaks
around 5Myr, with only a few being as old as 8-10Myr. These age
estimates together with the number of GMCs in the various evolutionary
stages lead us to conclude that 14Myr is the typical lifetime of a
GMC in M33 prior to cloud dispersal. The inactive and embedded
phases are short, lasting about 4 and 2Myr, respectively. This
underlines that embedded YSCCs rapidly break out from the clouds and
become partially visible in Hα or UV long before cloud
dispersal.
Description:
Table 5 :
Physical parameters for the 566 molecular clouds identified through
the IRAM 30m CO J=2-1 survey of the star forming disk of M33. For each
cloud the cloud type and the following properties are listed:
celestial coordinates, galactocentric radius, cloud deconvolved
effective radius and its uncertainty, CO(2-1) line velocity dispersion
from CPROPS and its uncertainty, line velocity dispersion from a
Gaussian fit, CO luminous mass and its uncertainty, and virial mass
from a Gaussian fit. In the last column the identification number of
the young stellar cluster candidates associated with the molecular
cloud are listed. Notes: We identify up to four young stellar cluster
candidates (YSCCs) associated with each molecular cloud and we list
them according to the identification number of Sharma et al. (2011,
Cat. J/A+A/545/A96) given also in Table 6.
Table 6 :
Physical parameters for the 630 young stellar cluster candidates
identified via their mid-infrared emission in the star forming disk of
M33. For each YSCC we list the type of source, the identified number
of the molecular clouds associated with it (if any) and the
corresponding cloud classes. In addition, for each YSCC we give the
celestial coordinates, the bolometric, total infrared, FUV and Halpha
luminosities, the estimated mass and age, the visual extinction, the
galactocentric radius, the source size, and its flux at 24µm.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table5.dat 91 566 Molecular clouds in M33: properties, classes
table6.dat 91 630 Young stellar cluster candidates in M33:
properties and classes
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See also:
J/A+A/534/A96 : Spitzer photometry of YSC in M33 (Sharma+, 2011)
Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- NCO [1/566] Molecular cloud number
5 A1 --- Type Cloud type (G1)
7- 14 F8.5 deg RAdeg Right ascension (J2000.0)
16- 23 F8.5 deg DEdeg Declination (J2000.0)
25- 27 F3.1 kpc R Galactocentric radius for cloud location
29- 31 I3 pc re Cloud deconvolved effective radius
33- 34 I2 pc e_re Cloud radius uncertainty
36- 39 F4.1 km/s sigmaC CO(2-1) velocity dispersion from CROPS
41- 43 F3.1 km/s e_sigmaC CROPS velocity dispersion uncertainty
45- 48 F4.1 km/s sigmaG ? CO(2-1) velocity dispersion from Gaussian fit
50- 57 E8.2 Msun MH2 Cloud luminous mass, including helium
59- 66 E8.2 Msun e_MH2 Luminous mass uncertainty
68- 75 E8.2 Msun MH2vir ? Cloud virial mass
77- 79 I3 --- NYSCC1 ? Identification number of associated YSCC,
in table6.dat
81- 83 I3 --- NYSCC2 ? Identification number of associated YSCC,
in table6.dat
85- 87 I3 --- NYSCC3 ? Identification number of associated YSCC,
in table6.dat
89- 91 I3 --- NYSCC4 ? Identification number of associated YSCC,
in table6.dat
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- NYSCC YSCC identification number (1)
5- 6 A2 --- Type YSCC type (2)
8- 10 I3 --- NCO1 ? ID number of associated molecular cloud
in table5.dat
12 A1 --- Type1 Cloud type (G1)
14- 16 I3 --- NCO2 ? ID number of associated molecular cloud
in table5.dat
18 A1 --- Type2 Cloud type (G1)
20- 28 F9.6 deg RAdeg Right ascension (J2000.0)
30- 38 F9.6 deg DEdeg Declination (J2000.0)
40- 44 F5.2 [10-7W] lg(Lbol) Log10 of bolometric luminosity
46- 50 F5.2 [10-7W] lg(LTIR) Log10 of total infrared luminosity
52- 56 F5.2 [10-7W] lg(LFUV) Log10 of far-UV luminosity
58- 62 F5.2 [10-7W] lg(LHa) Log10 of Halpha luminosity
64- 66 F3.1 [Msun] lg(M*) Log10 of YSCC mass
68- 70 F3.1 [yr] lg(Age) Log10 of YSCC age
72- 74 F3.1 --- Av Visual extinction
76- 78 F3.1 kpc R Galactocentric radius at YSCC location
80- 83 F4.1 arcsec Size YSCC size (radius) at 24 micron
85- 91 F7.2 mJy F24um Flux at 24um
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Note (1): The young stellar cluster candidate (YSCC) identification number is
the sequential number according to the 24micron source catalogue of
Sharma et al. (2011, Cat. J/A+A/534/A96).
We identify up to 2 molecular clouds likely associated withe the YSCC,
their ID number and properties are listed in Table 5
Note (2): The YSCC types have been defined as follows:
b = associated with clouds, no optical counterpart
c1 = associated with clouds: coincident Halpha and mid-infrared peaks
c2 = associated with clouds: coincident Halpha, mid-infrared and UV peaks
c3 = not associated with clouds but optically detected
d = ambiguous
e = not associated with clouds, mostly mid-infrared peaks only
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Global notes:
Note (G1): Molecular cloud types have been defined as follows:
A = inactive
B = embedded star formation
C = exposed star formation
D = ambiguous
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Acknowledgements:
Edvige Corbelli, edvige(at)arcetri.astro.it
(End) Edvige Corbelli [Arcetri], Patricia Vannier [CDS] 12-Apr-2017