A deep CO survey of molecular clouds in the southern Milky Way

Bronfman, L.; Álvarez, H.; Cohen, R. S.; Thaddeus, P.

doi:10.1086/191384

Cited by 97 publications

(119 citation statements)

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“…• 0 in Galactic latitude; Bronfman et al 1989). Emission from the GMC under study is between -33 and −2 km s −1 with a peak at −13.6 km s −1 .…”

Section: Gmc G3455+10mentioning

confidence: 98%

“…In this figure, Δlog(M/M ) is constant, at a value of ∼0.44. The CMD is well-fitted by a power law dN/dlog(M) ∝ M −α+1 , which can be expressed as dN/dM ∝ M −α , with the spectral mass index, α, equal to 1.7 ± 0.1 for (Bronfman et al 1989), over a map of their integrated emissions (color scale) and with contours of 1.2 mm continuum emission; middle and bottom images, CS(2-1) line profiles (their observing positions are indicated as black dots in the top image; Bronfman et al 1996). masses between ∼10 and 1.3 × 10 3 M .…”

Section: Physical Properties Of Clumpsmentioning

confidence: 99%

“…The GMC G345.5+1.0 was first observed as part of the Columbia University -Universidad de Chile 12 CO(1-0) Survey of the Southern Galaxy (Bronfman et al 1989). It is located approximately between 344.…”

Section: Gmc G3455+10mentioning

confidence: 99%

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Massive star formation in the GMC G345.5+1.0: spatial distribution of the dust emission

López¹,

Bronfman²,

Nyman³

et al. 2011

A&A

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Context. Massive condensations in giant molecular clouds (GMCs) are linked to the formation of high mass stars, which are the principal source of heavy elements and UV radiation, playing an important role in the evolution of galaxies. Aims. We attemp to make a complete census of massive-star formation within all of GMC G345.5+1.0. This cloud is located one degree above the Galactic plane and at 1.8 kpc from the Sun, thus there is little superposition of dust along the line-of-sight, minimizing confusion effects in identifying individual clumps. Methods. We observed the 1.2 mm continuum emission across the whole GMC using the Swedish-ESO Submillimetre Telescope (SEST) Imaging Bolometer Array (SIMBA) mounted on the SEST. Observations have a spatial resolution of 0.2 pc and cover 1.• 8 × 2.• 2 in the sky with a noise of 20 mJy beam −1 . Results. We identify 201 clumps with diameters between 0.2 and 0.6 pc, masses between 3.0 and 1.3 × 10 3 M , and densities between 5 × 10 3 and 4 × 10 5 cm −3 . The total mass of the clumps is 1.2 × 10 4 M , thus the efficiency in forming these clumps, estimated as the ratio of the total clump mass to the total GMC mass, is ∼0.02. The clump mass distribution for masses between 10 and 10 3 M is well-fitted by a power law dN/dM ∝ M −α , with a spectral mass index α of 1.7 ± 0.1. Given their mass distribution, clumps do not appear to be the direct progenitors of single stars. Comparing the 1.2 mm continuum emission with infrared images taken by the Midcourse Space Experiment (MSX) and by the Spitzer satellite, we find that at least ∼20% of the clumps are forming stars, and at most ∼80% are starless. Six massive-star forming regions (MSFRs) embedded in clumps and associated with IRAS point sources have mean densities of ∼10 5 cm −3 , luminosities >10 3 L , and spectral energy distributions that can be modeled with two dust components at different mean temperatures of 28 ± 5 and 200 ± 10 K.

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“…• 0 in Galactic latitude; Bronfman et al 1989). Emission from the GMC under study is between -33 and −2 km s −1 with a peak at −13.6 km s −1 .…”

Section: Gmc G3455+10mentioning

confidence: 98%

Section: Physical Properties Of Clumpsmentioning

confidence: 99%

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Massive star formation in the GMC G345.5+1.0: spatial distribution of the dust emission

López¹,

Bronfman²,

Nyman³

et al. 2011

A&A

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“…of the Galactic plane from l = 270 • -360 • , located in the southern hemisphere) was undertaken by Nyman et al (1987). This survey was, in turn, improved upon by Bronfman et al (1989), covering the region l = 300 • -348 • and b = ±2°, with an angular resolution of 9 arcmin using the same 1.2-m telescope as Nyman et al The results of these early CO surveys of the Milky Way are summarised in the review article by Combes (1991).…”

Section: A Brief History Of Southern Co Surveysmentioning

confidence: 99%

The Mopra Southern Galactic Plane CO Survey

Burton

Braiding

Glueck

et al. 2013

Publ. Astron. Soc. Aust.

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We present the first results from a new carbon monoxide (CO) survey of the southern Galactic plane being conducted with the Mopra radio telescope in Australia. The 12 CO, 13 CO, and C 18 O J = 1-0 lines are being mapped over the l = 305 • -345 • , b = ±0.5 • portion of the fourth quadrant of the Galaxy, at 35 arcsec spatial and 0.1 km s −1 spectral resolution. The survey is being undertaken with two principal science objectives: (i) to determine where and how molecular clouds are forming in the Galaxy and (ii) to probe the connection between molecular clouds and the 'missing' gas inferred from gamma-ray observations. We describe the motivation for the survey, the instrumentation and observing techniques being applied, and the data reduction and analysis methodology. In this paper, we present the data from the first degree surveyed, l = 323 • -324 • , b = ±0.5 • . We compare the data to the previous CO survey of this region and present metrics quantifying the performance being achieved; the rms sensitivity per 0.1 km s −1 velocity channel is ß1.5 K for 12 CO and ß0.7 K for the other lines. We also present some results from the region surveyed, including line fluxes, column densities, molecular masses, 12 CO/ 13 CO line ratios, and 12 CO optical depths. We also examine how these quantities vary as a function of distance from the Sun when averaged over the 1 square degree survey area. Approximately 2 × 10 6 M of molecular gas is found along the G323 sightline, with an average H 2 number density of n H 2 ∼ 1 cm −3 within the Solar circle. The CO data cubes will be made publicly available as they are published.

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“…In conjunction with radio continuum, infrared, and optical observations of H II regions, OB associations, and other Population I objects, they have demonstrated that virtually all star formation occurs in molecular clouds, and highresolution CO observations of dense cloud cores and molecular outÑows have contributed greatly to our under- Dame et al 1987 ;(2) Bitran et al 1997 ;(3) Ungerechts et al 2000 ;(8) Huang & Thaddeus 1986 ;(9) Heithausen et al 1993 ; present work (778 additional scans in Polaris, 1738 in Camelopardalis) ; (10) S. T. Megeath, T. M. Dame, & P. Thaddeus, 2001, in preparation ; (11) Stacy & Thaddeus 1991 ;(12) Lang et al 2000 ;(13) Oliver et al 1996 ;(14) B. A.Wilson 2001b, in preparation ;(15) May et al, 1993 ;(16) J. May, D. C. Murphy, M. Sahu, H. Alvarez, & L. Bronfman, 2001, in preparation ;(17) Grabelsky et al 1987 ;(18) Boulanger et al 1998 ;(19) Nyman, Bronfman, & Thaddeus 1989 ;(20) Bronfman et al 1989 ;(21) de Geus, Bronfman, & Thaddeus 1990. standing of how stars form. Since GMCs preferentially form in the arms of spiral galaxies (e.g., Loinard et al 1999 ;Aalto et al 1999), and it is possible to resolve the kinematic distance ambiguity for many of those in the inner Milky Way by appeal to the associated Population I, CO surveys have helped to reÐne our knowledge of the spiral structure of our system (e.g., Dame et al 1986 ;Grabelsky et al 1988).…”

Section: Introductionmentioning

confidence: 99%

The Milky Way in Molecular Clouds: A New Complete CO Survey

Dame

Hartmann

Thaddeus

2001

ApJ

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178

2,713

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New large-scale CO surveys of the Ðrst and second Galactic quadrants and the nearby molecular cloud complexes in Orion and Taurus, obtained with the CfA 1.2 m telescope, have been combined with 31 other surveys obtained over the past two decades with that instrument and a similar telescope on Cerro Tololo in Chile, to produce a new composite CO survey of the entire Milky Way. The survey consists of 488,000 spectra that Nyquist or beamwidth sample the entire Galactic plane over a (1 8 ¡) strip 4¡È10¡ wide in latitude, and beamwidth or sample nearly all large local clouds at higher lati-1 4 ¡ tudes. Compared with the previous composite CO survey of Dame et al. (1987), the new survey has 16 times more spectra, up to 3.4 times higher angular resolution, and up to 10 times higher sensitivity per unit solid angle. Each of the component surveys was integrated individually using clipping or moment masking to produce composite spatial and longitude-velocity maps of the Galaxy that display nearly all of the statistically signiÐcant emission in each survey but little noise.The composite maps provide detailed information on individual molecular clouds, suggest relationships between clouds and regions widely separated on the sky, and clearly display the main structural features of the molecular Galaxy. In addition, since the gas, dust, and Population I objects associated with molecular clouds contribute to the Galactic emission in every major wavelength band, the precise kinematic information provided by the present survey will form the foundation for many large-scale Galactic studies.A map of molecular column density predicted from complete and unbiased far-infrared and 21 cm surveys of the Galaxy was used both to determine the completeness of the present survey and to extrapolate it to the entire sky at o b o \ 32¡. The close agreement of the observed and predicted maps implies that only D2% of the total CO emission at o b o \ 32¡ lies outside our current sampling, mainly in the regions of Chamaeleon and the Gum Nebula. Taking into account this small amount of unobserved emission, the mean molecular column density decreases from D3 ] 1020 cm~2 at o b o \ 5¡ to D0.1 ] 1020 cm~2 at o b o \ 30¡ ; this drop is D6 times steeper than would be expected from a planeparallel layer, but is consistent with recent measurements of the mean molecular column density at higher latitudes.The ratio of the predicted molecular column density map to the observed CO intensity map provides a calibration of the mass conversion factor Out of the Galactic plane, X shows little systematic variation with latitude from a mean value of (1.8^0.3) ] 1020 cm~2 K~1 km~1 s. Given the large sky area and large quantity of CO data analyzed, we conclude that this is the most reliable measurement to date of the mean X value in the solar neighborhood.

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A deep CO survey of molecular clouds in the southern Milky Way

Cited by 97 publications

References 0 publications

Massive star formation in the GMC G345.5+1.0: spatial distribution of the dust emission

Massive star formation in the GMC G345.5+1.0: spatial distribution of the dust emission

The Mopra Southern Galactic Plane CO Survey

The Milky Way in Molecular Clouds: A New Complete CO Survey

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