J/ApJ/761/37 CO observations in giant molecular clouds of M33 (Miura+, 2012)
Giant molecular cloud evolutions in the nearby spiral galaxy M33.
Miura R.E., Kohno K., Tosaki T., Espada D., Hwang N., Kuno N.,
Okumura S.K., Hirota A., Muraoka K., Onodera S., Minamidani T., Komugi S.,
Nakanishi K., Sawada T., Kaneko H., Kawabe R.
<Astrophys. J., 761, 37 (2012)>
=2012ApJ...761...37M 2012ApJ...761...37M
ADC_Keywords: Galaxies, nearby ; Molecular clouds ; Cross identifications ;
Associations, stellar ; Millimetric/submm sources
Keywords: galaxies: individual: M33; ISM: clouds; ISM: molecules;
submillimeter: ISM
Abstract:
We present a giant molecular cloud (GMC) catalog of M33 (NGC598),
containing 71 GMCs in total, based on wide-field and high-sensitivity
CO(J=3-2) observations with a spatial resolution of 100pc using the
ASTE 10m telescope. Employing archival optical data, we identify 75
young stellar groups (YSGs) from the excess of the surface stellar
density, and estimate their ages by comparing with stellar evolution
models. A spatial comparison among the GMCs, YSGs, and H II regions
enable us to classify GMCs into four categories: Type A, showing no
sign of massive star formation (SF); Type B, being associated only
with H II regions; Type C, with both H II regions and <10Myr old YSGs;
and Type D, with both H II regions and 10-30Myr YSGs. Out of 65 GMCs
(discarding those at the edges of the observed fields), 1 (1%), 13
(20%), 29 (45%), and 22 (34%) are Types A, B, C, and D, respectively.
We interpret these categories as stages in a GMC evolutionary
sequence. Assuming that the timescale for each evolutionary stage is
proportional to the number of GMCs, the lifetime of a GMC with a mass
>105M☉ is estimated to be 20-40Myr. In addition, we find that
the dense gas fraction as traced by the CO(J=3-2)/CO(J=1-0) ratio is
enhanced around SF regions. This confirms a scenario where dense gas
is preferentially formed around previously generated stars, and will
be the fuel for the next stellar generation. In this way, massive SF
gradually propagates in a GMC until gas is exhausted.
Description:
We chose eight regions covering the northern and southern spiral arms
as well as the galaxy center, where the CO(J=1-0) emission is
prominent. The CO(J=3-2) (rest frequency: 345.796GHz) mapping
observations were performed between 2011 June and November, using the
Atacama Submillimeter Telescope Experiment (ASTE) 10m dish. The
observed area covers in total about 80% of the CO(J=1-0) based
molecular gas mass in Tosaki et al. (2011PASJ...63.1171T 2011PASJ...63.1171T).
The CO(J=1-0) emission was observed in a 31'x36' area (corresponding
to 7.6kpcx8.8kpc) toward the disk of M33 using the NRO 45m telescope.
Among the 71 GMCs in our catalog, only one GMC (GMC-50) is a new
identification.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 106 71 Properties of the CO(J=3-2) emission components
(from erratum published in 2017, ApJ, 834, 97)
table3.dat 98 75 M33 young stellar group catalog
table4.dat 101 71 Properties of M33 GMCs and massive star formation
(from erratum published in 2017, ApJ, 834, 97)
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See also:
J/A+A/549/A17 : IRAM spectra toward M33 GMCs (Buchbender+, 2013)
J/A+A/548/A52 : Molecular cloud formation in M33 (Braine+, 2012)
J/A+A/542/A108 : Giant molecular clouds in M33 (Gratier+, 2012)
J/A+A/534/A96 : Spitzer photometry of YSC in M33 (Sharma+, 2011)
J/MNRAS/416/2 : Photodissociation regions in M33 (Heiner+, 2011)
J/A+A/522/A3 : M33 CO(2-1) and HI integrated intensity maps (Gratier+, 2010)
J/ApJ/720/1674 : CFHT M33 extended sources catalog (San Roman+, 2010)
J/ApJ/700/103 : Ages of star clusters in M33 (Park+, 2009)
J/ApJ/699/839 : Newly identified star clusters in M33. II. (San Roman+, 2009)
J/ApJ/661/830 : Giant molecular clouds of M33 (Rosolowsky+, 2007)
J/A+A/476/1161 : Spitzer photometry of M33 (Verley+, 2007)
J/A+A/472/785 : Radio continuum survey of M33 (Tabatabaei+, 2007)
J/AJ/134/2168 : BVI photometry of M33 star clusters (Park+, 2007)
J/AJ/134/447 : Catalog of star cluster candidates in M 33 (Sarajedini+, 2007)
J/AJ/133/2393 : UBVRI phot. in 7 Local Group dwarfs galaxies (Massey+, 2007)
J/AJ/131/2478 : M31 and M33 UBVRI photometry (Massey+, 2006)
J/ApJS/149/343 : Giant molecular clouds in M33 (Engargiola+, 2003)
J/PASP/111/685 : HII regions of M33. II. (Hodge+, 1999)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Seq [1/71] GMC running sequence number in order
of decreasing peak intensity in spectrum;
<[MKT2012] NN> in Simbad
4 A1 --- f_Seq [a] a: GMC at the edge of the field of view
(the provided values are lower limits)
6 I1 h RAh Hour of right ascension (J2000) (1)
8- 9 I2 min RAm Minute of right ascension (J2000)
11- 14 F4.1 s RAs Second of right ascension (J2000)
16 A1 --- DE- Sign of declination (J2000) (1)
17- 18 I2 deg DEd Degree of declination (J2000) (1)
20- 21 I2 arcmin DEm Arcminute of declination (J2000) (1)
23- 26 F4.1 arcsec DEs Arcsecond of declination (J2000) (1)
28- 31 I4 km/s Vlsr [-260/-106] Observed LSR velocity of the
peak intensity
33- 36 F4.2 K Tmb [0.1/0.9] Peak intensity in Tmb (main beam
temperature)
38- 41 F4.1 km/s FWHM [1/17.3] FWHM line width
43- 46 F4.1 km/s e_FWHM [0.9/15] FWHM uncertainty
48- 50 I3 pc Amaj [42/189] Non-deconvolved major axis
52- 54 I3 pc Amin [33/102] Non-deconvolved minor axis
56- 58 I3 deg PA [5/180] Position angle (measured
counterclockwise from west to north)
60- 63 F4.1 10K.m/s.kpc2 L'CO [0.8/25.8] CO(J=3-2) luminosity
(in 104K.km/s.pc2 unit)
65- 68 F4.1 10K.m/s.kpc2 e_L'CO [0.4/27.5] L'CO uncertainty
70- 73 F4.1 10+5Msun Mvir [0.2/89]? Virial mass (2)
75- 78 F4.1 10+5Msun e_Mvir [0.1/80]? Mvir uncertainty
80 A1 --- l_R31 Limit flag on R31
81- 84 F4.2 --- R31 [0.1/0.9]? Averaged CO intensity ratio
(J=3-2/J=1-0) over the extent of the GMC
86- 89 F4.2 --- e_R31 [0.02/0.5]? R31 uncertainty
91- 93 I3 --- R07 ? Cross-identification with R07 (3)
94 A1 --- f_R07 [*] Blended sources in R07 (4)
96- 97 I2 --- R07a ? Cross-identification with a second
number of R07 (3)
99-106 A8 --- G11 Cross-identification with G11 number(s) (5)
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Note (1): Intensity-weighted peak position.
Note (2): Note that virial masses of 27 GMCs are not shown when the minor axis
of the GMC is smaller than the beam size.
Note (3): Cross identifications with Rosolowsky et al. 2007 (J/ApJ/661/830;
<M33GMC NNN> in Simbad)
Note (4): '*' indicates a single GMC in Rosolowsky et al.'s 2007 (J/ApJ/661/830)
appears to be composed of more than two GMCs in our catalog.
Note (5): Cross identifications with Gratier et al. 2012 (J/A+A/542/A108;
<[GBR2012] NNN> in Simbad)
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- YSG [1/75] Young Stellar Group running sequence
number in order of right ascension;
<[MKT2012] YSG NN> in Simbad
4- 5 I2 h RAh YSG central hour of right ascension (J2000)
7- 8 I2 min RAm Minute of right ascension (J2000)
10- 13 F4.1 s RAs Second of right ascension (J2000)
15 A1 --- DE- YSG central sign of declination (J2000)
16- 17 I2 deg DEd YSG central degree of declination (J2000)
19- 20 I2 arcmin DEm Arcminute of declination (J2000)
22- 25 F4.1 arcsec DEs Arcsecond of declination (J2000)
27 A1 --- l_Rcl Limit flag on Rcl
29- 32 F4.1 arcsec Rcl [7.2/22.4] Size of the stellar group rcl (1)
34- 36 I3 --- No [9/169] Number of O stars (more massive than
O9V-type stars)
38- 42 F5.2 mag Vmag [15.6/19.8] V magnitude of the brightest
member in the YSG (2)
44- 47 F4.2 mag E(B-V) [0.01/0.2] Applied reddening correction for
each YSG
49 A1 --- n_E(B-V) [a] E(B-V) from literature (3)
51- 52 I2 Myr Age0 [3/22] Lower estimated age of the YSG
54- 55 I2 Myr Age1 [5/50] Upper estimated age of the YSG
57- 98 A42 --- XID Cross-identification(s) (4)
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Note (1): Size of the stellar group, which approximately corresponds to the
boundary of n*=2 stars per area (see Section 3.2.2).
Note (2): We have used the photometric optical data set from the UBVI
ground-based survey of local star-forming galaxies with the Kitt Peak
National Observatory 4m telescope presented in Massey et al. 2006
(J/AJ/131/2478) - see section 2.3 - to create the V-(B-V) color-magnitude
diagram (i.e., Vmag-(B-V)0 diagram) for the disk of M33.
Note (3): 'a' indicates E(B-V) from Chandar et al. (1999ApJ...517..668C 1999ApJ...517..668C),
Park & Lee 2007 (J/AJ/134/2168),
Gonzalez Delgado & Perez (2000MNRAS.317...64G 2000MNRAS.317...64G), and
Churchwell & Goss (1999ApJ...514..188C 1999ApJ...514..188C).
Note (4): Cross identifications with other catalogs:
SM-n = Sarajedini & Mancone (2007, Cat. J/AJ/134/447;
<[SM2007] NNN> in Simbad).
PL-n = Park & Lee (2007, Cat. Cat. J/AJ/134/2168;
<[PL2007] NNN> in Simbad).
SSA-n = San Roman et al. (2010, Cat. J/ApJ/720/1674;
<[SSA2010] NNNN> in Simbad).
NGC-n = giant HII regions.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Seq [1/71] GMC identification number
4 A1 --- Type GMC classification (6)
6 A1 --- q_Type [ab] Good (a) or bad (b) Type (7)
8- 21 A14 --- YSG Young stellar groups (YSGs) number(s)
associated with the GMCs
23- 29 E7.3 10-7W LHa Hα luminosity in erg/s,
as measured over the extent of a GMC
31- 37 E7.3 10-7W L24um 24um luminosity in erg/s,
as measured over the extent of a GMC
39- 42 F4.2 mag AHa [0.01/2.3] Hα attenuation (8)
44- 50 E7.3 Msun/yr SFR [/0.05] Star formation rate (9)
52-101 A50 --- HII Name of the associated HII regions (10)
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Note (6): GMC classifications as follows:
A = no signature of massive star formation;
B = associated with HII region(s);
C = associated with HII region(s) and less than 10Myr old stellar group(s);
D = associated with HII region(s) and 10-30Myr old stellar group(s).
Note (7): Flag as follows:
a = The selected GMCs with more accurate classification. See details in the
text in Section 3.4.
b = GMCs at the edge of the fields of view. The values just provide lower
limits.
Note (8): The Hα attenuation is calculated as
AHα=2.5log[1+0.038L(24um)/L(Hα)] (Calzetti et al. 2005,
J/ApJ/633/871; Prescott et al. 2007ApJ...668..182P 2007ApJ...668..182P).
Note (9): Star formation rate (SFR), derived from L(24um) and L(Hα)
using the relation between the extinction-corrected Hα line
emission and the SFR in Calzetti et al. (2007ApJ...666..870C 2007ApJ...666..870C).
Note (10): Name of the associated HII regions (the names within parenthesis
indicate a counterpart of HII regions in the 24um catalog
(Onodera et al. 2010ApJ...722L.127O 2010ApJ...722L.127O):
B-n = Boulesteix et al. (1974A&A....37...33B 1974A&A....37...33B; in Simbad);
C-n = Courtes et al. (1987A&A...174...28C 1987A&A...174...28C; in Simbad);
H-n = Hodge et al. (1999, Cat. J/PASP/111/685; in Simbad);
V-n = Verley et al. (2007, Cat. J/A+A/476/1161; <[VHC2007b] HII NN> in Simbad).
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History:
From electronic version of the journal
* 14-Sep-2014: Insert into VizieR
* 19-Jan-2017: Tables 2 and 4 corrected from erratum published in
2017, ApJ, 834, 97
(End) Emmanuelle Perret [CDS] 06-Aug-2014