A wide-latitude CO survey of molecular clouds in the northern Milky Way

Dame, T. M.; Thaddeus, P.

doi:10.1086/163573

Cited by 170 publications

(131 citation statements)

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“…Preliminary observations by Cohen & Thaddeus (1977) were expanded to a beamwidth-sampled survey of the plane by ; roughly the same area has recently been mapped in the CO (J \ 2È1) line with the same angular resolution and grid spacing by Sakamoto et al (1997). The Ðrst large-scale superbeam survey, with 1¡ angular resolution, was conducted in the Ðrst quadrant by Dame & Thaddeus (1985), and a subsequent survey at 0¡ .5 resolution was included in the composite survey of Dame et al (1987). The very sensitive observations included in the present composite map were begun in 1991 as a series of narrow, Nyquist-sampled strips perpendicular to the Galactic plane (survey 7) ; Dame & Thaddeus (1994) used this surveyÈwith the highest sensitivity per unit solid angle of any in the composite map (see col.…”

Section: First Quadrantmentioning

confidence: 99%

“…The 21 cm component corresponding to the clouds at [12 km s~1 was identiÐed with the Local spiral arm by Lindblad (1974) ; the other component, LindbladÏs feature A, was modeled by Lindblad et al (1973) and Grape (1975) as an expanding shell of cold gas surrounding the Sun and data with lower sensitivity and angular resolution is shown in Fig. 4 of Dame & Thaddeus (1985).…”

Section: Arge-scale Structurementioning

confidence: 99%

“…Because some molecular clouds as far away as 2È3 kpc can be seen as dark nebulae (Huang, Dame, & Thaddeus 1983 ;Dame & Thaddeus 1985), the integration range of the CO map in Figure 6b varies with longitude in order to include emission with near kinematic distances less than 2.5 kpc. While this procedure eliminates emission from clouds deep in the inner Galaxy, a thin ridge of emission near b \ 0¡ remains, owing to clouds near the solar circle on the far side of the Galaxy.…”

Section: Fig 7è(a)mentioning

confidence: 99%

See 2 more Smart Citations

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

Dame

Hartmann

Thaddeus

2001

ApJ

Self Cite

2,120

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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Section: First Quadrantmentioning

confidence: 99%

Section: Arge-scale Structurementioning

confidence: 99%

Section: Fig 7è(a)mentioning

confidence: 99%

See 1 more Smart Citation

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

Dame

Hartmann

Thaddeus

2001

ApJ

Self Cite

2,120

178

2,713

View full text Add to dashboard Cite

show abstract

“…Extensive surveys of the CO and 13 CO (J=1-0 at λ = 2.6 mm and J=2-1 at λ = 1.3 mm) emissions in the Galaxy have been used to determine the overall distribution of star-forming H 2 gas and its properties (Scoville & Solomon 1975;Sanders et al 1985;Dame & Thaddeus 1985;Scoville et al 1987;Clemens et al 1988;Matsunaga et al 2001;Dame et al 2001;Jackson et al 2006). CO emission is ubiquitous at all Galactic longitudes in the inner Galaxy (|l| < 90 • ) and within 1 • latitude of the Galactic plane.…”

Section: Observed Properties Of Molecular Gasmentioning

confidence: 99%

Evolution of star formation and gas

Scoville¹

2013

Secular Evolution of Galaxies

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In these lectures I review observations of star-forming molecular clouds in our Galaxy and nearby galaxies to develop a physical intuition for understanding star formation in the local and high-redshift Universe. A lot of this material is drawn from early work in the field since much of the work was done two decades ago and this background is not generally available in the present literature. I also attempt to synthesise our welldeveloped understanding of star formation in low-redshift galaxies with constraints from theory and observations at high redshift to develop an intuitive model for the evolution of galaxy mass and luminosity functions in the early Universe.The overall goal of this contribution is to provide students with background helpful for analysis of far-infrared (FIR) observations from Herschel and millimetre/submillimetre (mm/submm) imaging with ALMA (the Atacama Large Millimetre/submillimetre Array).These two instruments will revolutionise our understanding of the interstellar medium (ISM) and associated star formation and galaxy evolution, both locally and in the distant Universe. To facilitate interpreting the FIR spectra of Galactic star-forming regions and high-redshift sources, I develop a model for the dust heating and radiative transfer in order to elucidate the observed infrared (IR) emissions. I do this because I am not aware of a similar coherent discussion in the literature. Star-forming molecular cloudsHere, I provide an overview of the observations and physics of star-forming molecular clouds in the Galaxy and nearby normal galaxies. The motivation is to develop the intuitive background for analysis of observations at high 1 arXiv:1210.6990v2 [astro-ph.CO] 1 Nov 2012

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“…11 of Kraemer et al 2010), and the infrared dark cloud IRDC G79.3+0.3 (hereafter the IRDC) towards the southern and western borders (Redman et al 2003). The local arm is seen tangentially in this direction (Dame & Thaddeus 1985;Rygl et al 2012), which makes it difficult to determine distances and to identify mutual associations among targets associated with the Cyg X region. An update of the information currently available and a brief discussion of the distance is presented below, in Sect.…”

Section: Introductionmentioning

confidence: 99%

Ammonia observations in the LBV nebula G79.29+0.46

Rizzo

Palau

Jiménez-Esteban

et al. 2014

A&A

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Context. The surroundings of luminous blue variable (LBV) stars are excellent laboratories to study the effects of their high UV radiation, powerful winds, and strong ejection events onto the surrounding gas and dust. Aims. We aim at determining the physical parameters of the dense gas near G79.29+0.46, an LBV-candidate located at the centre of two concentric infrared rings, which may interact with the infrared dark cloud (IRDC) G79.3+0.3. Methods. The Effelsberg 100 m telescope was used to observe the NH 3 (1, 1) and (2, 2) emission in a field of view of 7 × 7 including the infrared rings and a part of the IRDC. In addition, we observed particular positions in the NH 3 (3,3) transition toward the strongest region of the IRDC, which is also closest to the ring nebula. Results. We report here the first coherent ring-like structure of dense NH 3 gas associated with an evolved massive star. It is well traced in both ammonia lines, surrounding an already known infrared ring nebula; its column density is two orders of magnitude lower than the IRDC. The NH 3 emission in the IRDC is characterized by a low and uniform rotational temperature (T rot ∼10 K) and moderately high opacities in the (1, 1) line. The rest of the observed field is spotted by warm or hot zones (T rot >30 K) and characterized by optically thin emission of the (1, 1) line. The NH 3 abundances are about 10 −8 in the IRDC, and 10 −10 -10 −9 elsewhere. The warm temperatures and low abundances of NH 3 in the ring suggest that the gas is being heated and photo-dissociated by the intense UV field of the LBV star. An outstanding region is found to the south-west (SW) of the LBV star within the IRDC. The NH 3 (3, 3) emission at the centre of the SW region reveals two velocity components tracing gas at temperatures >30 K. Of particular interest is the northern edge of the SW region, which coincides with the border of the ring nebula and a region of strong 6 cm continuum emission; here, the opacity of the (1, 1) line and the NH 3 abundance do not decrease as expected in a typical clump of an isolated cold dark cloud. This strongly suggests some kind of interaction between the ring nebula (powered by the LBV star) and the IRDC. We finally discuss the possibility of NH 3 evaporation from the dust grain mantles due to the already known presence of low-velocity shocks in the area. Conclusions. The detection of the NH 3 associated with this LBV ring nebula, as well as the special characteristics of the northern border of the SW region, confirm that the surroundings of G79.29+0.46 constitute an exemplary scenario, which merits to be studied in detail by other molecular tracers and higher angular resolutions.

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A wide-latitude CO survey of molecular clouds in the northern Milky Way

Cited by 170 publications

References 0 publications

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

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

Evolution of star formation and gas

Ammonia observations in the LBV nebula G79.29+0.46

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