A large scale CO survey of the Galactic center
region

Bitran, M.; Álvarez, H.; Bronfman, L.; May, J.; Thaddeus, P.

doi:10.1051/aas:1997214

Cited by 82 publications

(118 citation statements)

References 13 publications

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“…It has been observed previously by several authors (Bitran et al 1997;Fukui et al 2006;Sawada et al 2001;Lee & Lee 2003;Riquelme et al 2010b); its main velocity component is at 98 km s −1 (from the HCO + data from Riquelme et al 2010b), and a large velocity width in all the species is observed in this and previous works, which indicates that this source indeed belongs to the GC region. …”

Section: Single Temperature Regime In the Loop Regionsupporting

confidence: 83%

Kinetic temperatures toward X1/X2 orbit interceptions regions and giant molecular loops in the Galactic center region

Riquelme

Amo-Baladrón

Martı́n-Pintado

et al. 2012

A&A

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Context. It is well known that the kinetic temperatures, T kin , of the molecular clouds in the Galactic center region are higher than in typical disk clouds. However, the T kin of the molecular complexes found at higher latitudes towards the giant molecular loops in the central region of the Galaxy is so far unknown. The gas of these high-latitude molecular clouds (hereafter referred to as "halo clouds") is located in a region where the gas in the disk may interact with the gas in the halo in the Galactic center region. Aims. To derive T kin in the molecular clouds at high latitude and understand the physical process responsible for the heating of the molecular gas both in the central molecular zone (the concentration of molecular gas in the inner ∼500 pc) and in the giant molecular loops. Methods. We measured the metastable inversion transitions of NH 3 from (J, K) = (1, 1) to (6, 6) toward six positions selected throughout the Galactic central disk and halo. We used rotational diagrams and large velocity gradient (LVG) modeling to estimate the kinetic temperatures toward all the sources. We also observed other molecules like SiO, HNCO, CS, C 34 S, C 18 O, and 13 CO, to derive the densities and to trace different physical processes (shocks, photodissociation, dense gas) expected to dominate the heating of the molecular gas. Results. We derive for the first time T kin of the high-latitude clouds interacting with the disk in the Galactic center region. We find high rotational temperatures in all the observed positions. We derive two kinetic temperature components (∼150 K and ∼40 K) for the positions in the central molecular zone, and only the warm kinetic temperature component for the clouds toward the giant molecular loops. The fractional abundances derived from the different molecules suggest that shocks provide the main heating mechanism throughout the Galactic center, also at high latitudes.

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Section: Single Temperature Regime In the Loop Regionsupporting

confidence: 83%

Kinetic temperatures toward X1/X2 orbit interceptions regions and giant molecular loops in the Galactic center region

Riquelme

Amo-Baladrón

Martı́n-Pintado

et al. 2012

A&A

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“…The nature of these so-called wide line clouds has been discussed by Stacy et al (1988) and Kumar & Ri †ert (1997) ; the one at l \ 3¡, also known as Bania Clump 2, was discussed by Stark & Bania (1986). The southern telescope has mapped the Galactic center in both CO (Bitran et al 1997) and C18O (Dahmen et al 1997) ; other large-scale CO, 13CO, C18O, and CO (J \ 2È1) surveys of the Galactic center region are listed in Table 1 of Bitran et al (1997).…”

Section: Galactic Centermentioning

confidence: 99%

“…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.…”

Section: Introductionmentioning

confidence: 96%

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

Dame

Hartmann

Thaddeus

2001

ApJ

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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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“…These results can be combined with CO data to provide insight into conditions A&A 523, A45 (2010) References. 1) Burton & Liszt (1983); 2) Jaffe et al (1996); 3) Nakagawa et al (1995); 4) Bania (1986); 5) Bitran et al (1997); 6) Fukui et al (2006); 7) Oka et al (1996); 8) Sawada et al (2001); 9) Oka et al (2007); 10) Bally et al (1987); 11) Dahmen et al (1997); 12) Morris et al (1983); 13) Martín-Pintado et al 199714) Boyce & Cohen (1994); 15) Zylka et al (1992); 16) Fukui et al (1977); 17) Jackson et al (1996); 18) Lee (1996). Notes.…”

Section: Introductionunclassified

“…Large-scale surveys have been made in 12 C 16 O and its isotopomers in the J = 1 → 0, as well as in J = 2 → 1 spectral lines (e.g. Bitran et al 1997;Dahmen et al 1998;Oka et al 2001). Up to now, there are few complete maps in species that are less abundant than CO (e.g.…”

Section: Introductionmentioning

confidence: 99%

A survey of the Galactic center region in HCO⁺, H¹³CO⁺, and SiO

Riquelme

Bronfman

Mauersberger

et al. 2010

A&A

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Aims. A large-scale survey of the Galactic center region in the 3 mm rotational transitions of SiO, HCO + and H 13 CO + (beamsize ∼3. 6) was conducted to provide an estimate of cloud conditions, heating mechanisms, chemistry, and other properties. Methods. Using the NANTEN 4 m telescope from Nagoya University, a region between −5. • 75 < l < 5.• 6 and −0.• 68 < b < 1.• 3 was mapped in the J = 1 → 0 lines of HCO + and H 13 CO + and in the J = 2 → 1 line of SiO with a spacing of 3. 75 (HCO + ) and 1. 875 (SiO and H 13 CO + ). Results. Velocity channel maps, longitude-velocity maps, and latitude-velocity maps are presented. We identify 51 molecular clouds; 33 of them belong to the Galactic center and 18 to disk gas. We derive an average of the luminosity ratio of SiO(J = 2 → 1)/CO(J = 1 → 0) in clouds belonging to the Galactic center of 4.9 × 10 −3 and for disk clouds of 3.4 × 10 −3 . The luminosity ratio of HCO + (J = 1 → 0)/CO(J = 1 → 0) in the Galactic center is 3.5 × 10 −2 , and for disk clouds it is 1.5 × 10 −2 . We can distinguish clearly between regions where the SiO or HCO + dominate.

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A large scale CO survey of the Galactic center region

Cited by 82 publications

References 13 publications

Kinetic temperatures toward X1/X2 orbit interceptions regions and giant molecular loops in the Galactic center region

Kinetic temperatures toward X1/X2 orbit interceptions regions and giant molecular loops in the Galactic center region

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

A survey of the Galactic center region in HCO⁺, H¹³CO⁺, and SiO

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A large scale CO survey of the Galactic center region

Cited by 82 publications

References 13 publications

Kinetic temperatures toward X1/X2 orbit interceptions regions and giant molecular loops in the Galactic center region

Kinetic temperatures toward X1/X2 orbit interceptions regions and giant molecular loops in the Galactic center region

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

A survey of the Galactic center region in HCO+, H13CO+, and SiO

Contact Info

Product

Resources

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A survey of the Galactic center region in HCO⁺, H¹³CO⁺, and SiO