J/ApJ/821/125 SMA obs. of giant molecular clouds in NGC 300 (Faesi+, 2016)
Resolving giant molecular clouds in NGC 300: a first look with the
submillimeter array.
Faesi C.M., Lada C.J., Forbrich J.
<Astrophys. J., 821, 125-125 (2016)>
=2016ApJ...821..125F 2016ApJ...821..125F (SIMBAD/NED BibCode)
ADC_Keywords: Molecular clouds ; Radio lines ; Millimetric/submm sources
Keywords: galaxies: NGC 300; galaxies: ISM; ISM: clouds; ISM: molecules;
radio lines: galaxies; techniques: interferometric
Abstract:
We present the first high angular resolution study of giant molecular
clouds (GMCs) in the nearby spiral galaxy NGC 300, based on
observations from the Submillimeter Array (SMA). We target eleven
500pc sized regions of active star formation within the galaxy in the
12CO(J=2-1) line at 40pc spatial and 1km/s spectral resolution and
identify 45 individual GMCs. We characterize the physical properties
of these GMCs, and find that they are similar to GMCs in the disks of
the Milky Way and other nearby spiral galaxies. For example, the GMC
mass spectrum in our sample has a slope of 1.80±0.07. Twelve clouds
are spatially resolved by our observations, of which ten have virial
mass estimates that agree to within a factor of two with mass
estimates derived directly from 12CO integrated intensity,
suggesting that the majority of these GMCs are bound. The resolved
clouds show consistency with Larson's fundamental relations between
size, linewidth, and mass observed in the Milky Way. We find that the
linewidth scales with the size as ΔV∝R0.52±0.20, and
the median surface density in the subsample is 54M☉/pc2. We
detect 13CO in four GMCs and find a mean 12CO/13CO flux ratio of
6.2. Our interferometric observations recover between 30% and 100% of
the integrated intensity from the APEX single dish 12CO observations
of Faesi et al. (2014, J/ApJ/789/81), suggesting the presence of
low-mass GMCs and/or diffuse gas below our sensitivity limit. The
fraction of APEX emission recovered increases with the SMA total
intensity, as well as with the star formation rate.
Description:
SMA observations of NGC 300 have been obtained during SMA observing
semesters 2011B, 2013A, 2013B, and 2014A. Our 11 targets (see table 1
and figure 1), which represent several of the brightest CO(2-1) single
dish detections from the APEX-observed H II region sample of Faesi et
al. (2014, J/ApJ/789/81), were successfully observed with 13 SMA
tracks over 13 nights between 2011 December and 2014 November, with
one source observed per track.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 71 13 SMA observations
table3.dat 104 45 NGC 300 giant molecular cloud (GMC) properties
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See also:
J/ApJ/798/58 : HELGA VI. GMC associations in M31 (Kirk+, 2015)
J/ApJ/789/81 : Multiwavelength data of HII regions in NGC 300 (Faesi+, 2014)
J/ApJ/772/107 : Giant molecular clouds in nearby gal. (Donovan Meyer+, 2013)
J/A+A/542/A108 : Giant molecular clouds in M33 (Gratier+, 2012)
J/ApJ/699/1092 : Giant molecular clouds (SRBY) (Heyer+, 2009)
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/661/830 : Giant molecular clouds of M33 (Rosolowsky+, 2007)
J/AJ/128/1167 : ARAUCARIA project : NGC 300 Cepheids. II (Gieren+, 2004)
J/ApJS/149/343 : Giant molecular clouds in M33 (Engargiola+, 2003)
J/ApJ/551/852 : FCRAO CO survey of the outer Galaxy (Heyer+, 2001)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 11 A11 "Y/M/D" Date Date of observation
13- 18 A6 --- --- [DCL88-]
19- 22 A4 --- [DCL88] Name of the HII region targeted
24- 36 A13 --- Array Array configuration ("compact" or
"compact-north")
38 A1 --- Na [5-8] Number of antennas
40- 43 F4.1 m Dmin [16.4] Minimum baseline
45- 49 F5.1 m Dmax [68/140] Maximum baseline
51- 54 F4.2 --- [0.06/0.3] Track-averaged zenith opacity
at 225GHz
56- 60 F5.1 min Time [171/312] On-source time of observation
62- 71 A10 --- PID Project code
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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- 3 A3 --- --- [DCL]
4- 7 A4 --- [DCL88] Name of the HII region
8 A1 --- --- [-]
9 I1 --- ID Cloud identifier within the DCL region
11- 12 I2 h RAh [0] Hour of Right Ascension (J2000) (1)
14- 15 I2 min RAm [54/55] Minute of Right Ascension (J2000)
17- 21 F5.2 s RAs Second of Right Ascension (J2000)
23 A1 --- DE- [-] Sign of Declination (J2000) (1)
24- 25 I2 deg DEd [37] Degree of Declination (J2000) (1)
27- 28 I2 arcmin DEm [38/43] Arcminute of Declination (J2000)
30- 33 F4.1 arcsec DEs Arcsecond of Declination (J2000)
35- 39 F5.1 km/s v0 [88/181] Best-fit velocity centroid
41- 44 F4.1 arcsec amaj [3/11] FWHM major axis length (2)
46- 48 F3.1 arcsec bmin [1/6] FWHM minor axis length (2)
50- 52 I3 deg PA [-78/82] Position angle (3)
54- 57 F4.1 pc R [8/43]? Physical size
59- 62 F4.1 pc e_R [1/15]? Uncertainty in R (4)
64- 66 F3.1 km/s DelV [1.8/8.3] FWHM linewidth
68- 70 F3.1 km/s e_DelV [0.6/6] Uncertainty in DelV (4)
72- 75 F4.1 10+4Msun Mlum [0.5/75] Luminous mass
77- 80 F4.1 10+4Msun e_Mlum [0.7/10] Uncertainty in Mlum (4)
82- 85 F4.1 10+4Msun Mvir [1/41]? Virial mass
87- 90 F4.1 10+4Msun e_Mvir [2/24]? Uncertainty in Mvir (4)
92- 97 E6.2 K.km/s.pc2 LCO [601/90600] Total CO(2-1) luminosity
99-104 E6.2 K.km/s.pc2 e_LCO [794/11500] Uncertainty in LCO (4)
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Note (1): Of center, intensity-weighted.
Note (2): Prior to deconvolution from the synthesized beam.
Note (3): Measured counterclockwise from the northern declination axis,
computed prior to deconvolution.
Note (4): Computed by CPROPS's bootstrap method
(Rosolowsky & Leroy 2006PASP..118..590R 2006PASP..118..590R); see section 3.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 28-Jul-2016