J/ApJ/857/19 ALMA view of GMCs in NGC 300 (Faesi+, 2018)
The ALMA view of GMCs in NGC 300: physical properties and scaling relations at
10pc resolution.
Faesi C.M., Lada C.J., Forbrich J.
<Astrophys. J., 857, 19 (2018)>
=2018ApJ...857...19F 2018ApJ...857...19F
ADC_Keywords: H II regions; Molecular clouds; Carbon monoxide
Keywords: galaxies: individual (NGC 300); galaxies: ISM; ISM: clouds;
ISM: molecules; radio lines: galaxies; techniques: interferometric
Abstract:
We have conducted a 12CO(2-1) survey of several molecular gas
complexes in the vicinity of HII regions within the spiral galaxy
NGC300 using the Atacama Large Millimeter Array (ALMA). Our
observations attain a resolution of 10pc and 1km/s, sufficient to
fully resolve giant molecular clouds (GMCs) and the highest obtained
to date beyond the Local Group. We use the CPROPS algorithm to
identify and characterize 250 GMCs across the observed regions. GMCs
in NGC300 appear qualitatively and quantitatively similar to those in
the Milky Way disk: they show an identical scaling relationship
between size R and linewidth ΔV (ΔV∝R0.48±0.05),
appear to be mostly in virial equilibrium, and are consistent with
having a constant surface density of about 60M☉/pc2. The GMC
mass spectrum is similar to those in the inner disks of spiral
galaxies (including the Milky Way). Our results suggest that global
galactic properties such as total stellar mass, morphology, and
average metallicity may not play a major role in setting GMC
properties, at least within the disks of galaxies on the star-forming
main sequence. Instead, GMC properties may be more strongly influenced
by local environmental factors such as the midplane disk pressure. In
particular, in the inner disk of NGC 300, we find this pressure to be
similar to that in the local Milky Way but markedly lower than that in
the disk of M51, where GMCs are characterized by systematically higher
surface densities and a higher coefficient for the size-linewidth
relation.
Description:
We obtained ALMA Cycle 2 observations (project code 2013.1.00586.S;
PI: C. Lada) in the 12CO(2-1) line at 230.538GHz toward 48 positions
in NGC 300 representing all 42 CO detections plus six selected CO
nondetections from the Atacama Pathfinder EXperiment (APEX) survey of
Faesi+, 2014, J/ApJ/789/81. The observed pointing centers were
originally drawn from the HII region catalog of Deharveng+
(1988A&AS...73..407D 1988A&AS...73..407D), with refinements made to better center on CO
peaks for the subsample of 10 regions detected with the SMA (Faesi+
2016, J/ApJ/821/125).
Figure 1 shows the observed regions on a 250um Herschel/SPIRE image
obtained by our team (PI: J. Forbrich).
All targets were observed with the ALMA 12m array during Cycle 2 on
2014 December 9, 12, and 15. Each of the 48 regions was observed for
two sets of five 6s scans each night, adding up to a total on-source
time of 3.03 minutes per target.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 52 48 NGC 300 regions observed
table7.dat 131 299 Giant molecular cloud (GMC) catalog
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See also:
VIII/39 : Composite CO Survey of the Milky Way (Dame+ 1987)
VII/237 : HYPERLEDA. I. Catalog of galaxies (Paturel+, 2003)
J/ApJS/63/821 : Inner Galaxy Molecular clouds & cloud cores (Scoville+, 1987)
J/ApJ/428/693 : Rosette Nebula and Maddalena Cloud structures (Williams+ 1994)
J/ApJ/551/852 : FCRAO CO survey of the outer Galaxy (Heyer+, 2001)
J/ApJS/149/343 : Giant molecular clouds in M33 (Engargiola+, 2003)
J/AJ/128/1167 : ARAUCARIA project : NGC 300 Cepheids. II (Gieren+, 2004)
J/ApJ/654/240 : Giant molecular clouds in M31 (Rosolowsky+, 2007)
J/ApJ/661/830 : Giant molecular clouds of M33 (Rosolowsky+, 2007)
J/ApJ/686/948 : CO in extragalactic giant molecular clouds (Bolatto+, 2008)
J/ApJS/178/56 : CO observations of LMC Giant Molecular clouds (Fukui+, 2008)
J/ApJ/699/1092 : Giant molecular clouds (SRBY) (Heyer+, 2009)
J/A+A/505/405 : A catalogue of Spitzer dark clouds (Peretto+, 2009)
J/PASP/122/1397 : Spitzer Survey of Stellar Structure in Gal. (Sheth+, 2010)
J/ApJS/197/16 : CO obs. of LMC molecular clouds (MAGMA). (Wong+, 2011)
J/A+A/542/A108 : Giant molecular clouds in M33 (Gratier+, 2012)
J/ApJ/772/107 : Giant molecular clouds in nearby gal. (Donovan Meyer+, 2013)
J/ApJ/784/3 : The PAWS catalogs of GMCs and islands in M51 (Colombo+, 2014)
J/ApJ/789/81 : Multiwavelength survey of HII reg. in NGC300 (Faesi+, 2014)
J/ApJS/212/2 : GMCs in 4th Galactic quadrant (Garcia+, 2014)
J/ApJ/803/16 : GMCs in NGC4526 based on 12CO (Utomo+, 2015)
J/ApJ/821/125 : SMA obs. of giant molecular clouds in NGC 300 (Faesi+, 2016)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- --- [dcl]
4- 7 A4 --- [DCL88] Name of the HII region
9- 10 I2 h RAh Hour of right ascension (J2000)
12- 13 I2 min RAm Minute of right ascension (J2000)
15- 19 F5.2 s RAs Second of right ascension (J2000)
21 A1 --- DE- Sign of declination (J2000)
22- 23 I2 deg DEd Degree of declination (J2000)
25- 26 I2 arcmin DEm Arcminute of declination (J2000)
28- 31 F4.1 arcsec DEs Arcsecond of declination (J2000)
33 A1 --- l_ICO Limit flag on ICO
35- 39 F5.3 K ICO [0.01/1.2]? CO integrated intensity ICO (1)
41- 45 F5.1 km/s v0 [84.6/198.1]? Velocity centroid (1)
47 A1 --- f_v0 [b] Flag on v0 (2)
49- 52 F4.1 km/s FWHM [4/24.1]? Spectral Gaussian fit FWHM (1)
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Note (1): From the APEX single-dish observations of Faesi+ (2014, J/ApJ/789/81).
Note (2):
b = v0 for CO nondetections is instead the expected velocity at that position
based on the HI moment 1 map of Puche+ (1990AJ....100.1468P 1990AJ....100.1468P).
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Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- --- [DCL]
4- 7 A4 --- [DCL88] Name of the HII region
8 A1 --- --- [-]
9- 11 A3 --- ID Cloud identifier within HII region (1)
13- 14 I2 h RAh [0] Hour of Right Ascension (J2000) (2)
16- 17 I2 min RAm [54/55] Minute of Right Ascension (J2000) (2)
19- 23 F5.2 s RAs Second of Right Ascension (J2000) (2)
25 A1 --- DE- [-] Sign of the Declination (J2000) (2)
26- 27 I2 deg DEd [37] Degree of Declination (J2000) (2)
29- 30 I2 arcmin DEm [36/44] Arcminute of Declination (J2000) (2)
32- 35 F4.1 arcsec DEs Arcsecond of Declination (J2000) (2)
37- 41 F5.1 km/s v0 [79.2/200.3] Central velocity (3)
43- 47 F5.2 --- a/b [1/53]? Deconvolved aspect ratio
49- 53 F5.1 deg PA [-90/89.6]? Deconvolved position angle
55- 58 F4.1 pc R [2.4/63.4]? Extrapolated & deconvolved size
60- 62 F3.1 pc e_R [0.6/6.1]? Uncertainty in R (4)
64- 67 F4.1 km/s DelV [1/10.6] Extrapolated & deconvolved FWHM
linewidth
69- 71 F3.1 km/s e_DelV [0.3/3.3] Uncertainty in DelV (4)
73- 78 F6.1 10+3Msun Mlum [1.4/1020] Luminous mass (5)
80- 83 F4.1 10+3Msun e_Mlum [0.8/41] Uncertainty in Mlum (4)
85- 90 F6.1 10+3Msun Mvir [0.9/1180]? Virial mass
92- 96 F5.1 10+3Msun e_Mvir [1.1/142]? Uncertainty in Mvir (4)
98-102 F5.1 K.km/s.pc2 LCO [1.5/885] CO(2-1) luminosity
104-107 F4.1 K.km/s.pc2 e_LCO [0.8/36] Uncertainty in LCO (4)
109-113 F5.3 K Tmax [0.5/9.8] Peak CO(2-1) brightness temperature
115-118 F4.1 --- S/N [4.5/48.1] Peak signal-to-noise
120-131 A12 --- Note Additional note(s) (6)
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Note (1): Assigned number preceded by "A" to signify this ALMA study;
GMCs are <[FLF2018] DCLNNNA-ANN> in Simbad.
Note (2): As measured by the intensity-weighted first moment along
this direction.
Note (3): As measured by the intensity-weighted first moment along
the velocity axis.
Note (4): Calculated in CPROPS using 1000 bootstrap iterations.
Note (5): Calculated from CO luminosity and a metallicity-dependent X-factor.
Note (6):
F = final sample;
R = resolved sample;
O = outside primary beam by more than 10% beam FWHM;
DCLXX-Y = this cloud is a duplicate of cloud DCLXX-Y, and is not considered
independently in the analysis.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 14-Feb-2019