The Mopra Southern Galactic Plane CO Survey — Data Release 1 (original) (raw)

The Mopra Southern Galactic Plane CO Survey

Publications of the Astronomical Society of Australia, 2013

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 12CO, 13CO, and C18O J = 1–0 lines are being mapped over the l=305circtext−−345circ,b=pm0.5circl = 305^{\circ }\text{--} 345^{\circ }, b = \pm 0.5^{\circ }l=305circtext−−345circ,b=pm0.5circ 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=323circtext−−324circ,b=pm0.5circl = 323^{\circ } \text{--} 324^{\circ }, b = \pm 0.5^{\circ }l=323circtext−−324circ,b=pm0.5circ . We compare the data to the previous CO survey of this regio...

The Milky Way in molecular clouds: A new complete CO survey

The Astrophysical Journal, 2001

New large-scale CO surveys of the first 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 (1/8°) sample the entire Galactic plane over a strip 4°-10° wide in latitude, and beamwidth or 1/4° sample nearly all large local clouds at higher latitudes. 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 significant 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 largescale Galactic studies. A map of molecular column density predicted from complete and unbiased farinfrared 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 |b| < 32°. The close agreement of the observed and predicted maps implies that only ~2% of the total CO emission at |b| < 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 ~3 x 10 20 cm-2 at |b| = 5° to ~0.1 x 10 20 cm-2 at |b| = 30°; this drop is ~6 times steeper than would be expected from a plane parallel 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 CO-to-H 2 mass conversion factor X ≡ N H 2 /W CO. Out of the Galactic plane (|b| > 5°), X shows little systematic variation with latitude from a mean value of 1.8 ± 0.3 x 10 20 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.

The H 2 O Southern Galactic Plane Survey: NH 3 (1,1) and (2,2) catalogues

Monthly Notices of the Royal Astronomical Society, 2012

The H 2 O Southern Galactic Plane Survey (HOPS) has mapped a 100 degree strip of the Galactic plane (−70 • > l > 30 • , |b| < 0.5 • ) using the 22-m Mopra antenna at 12-mm wavelengths. Observations were conducted in on-the-fly mode using the Mopra spectrometer (MOPS), targeting water masers, thermal molecular emission and radio-recombination lines. Foremost among the thermal lines are the 23 GHz transitions of NH 3 J,K = (1,1) and (2,2), which trace the densest parts of molecular clouds (n > 10 4 cm −3 ). In this paper we present the NH 3 (1,1) and (2,2) data, which have a resolution of 2 arcmin and cover a velocity range of ±200 km s −1 . The median sensitivity of the NH 3 data-cubes is σ T mb = 0.20 ± 0.06 K. For the (1,1) transition this sensitivity equates to a 3.2 kpc distance limit for detecting a 20 K, 400 M ⊙ cloud at the 5σ level. Similar clouds of mass 5,000 M ⊙ would be detected as far as the Galactic centre, while 30,000 M ⊙ clouds would be seen across the Galaxy. We have developed an automatic emission finding procedure based on the ATNF DUCHAMP software and have used it to create a new catalogue of 669 dense molecular clouds. The catalogue is 100 percent complete at the 5σ detection limit (T mb = 1.0 K). A preliminary analysis of the ensemble cloud properties suggest that the near kinematic distances are favoured. The cloud positions are consistent with current models of the Galaxy containing a long bar. Combined with other Galactic plane surveys this new molecular-line dataset constitutes a key tool for examining Galactic structure and evolution. Data-cubes, spectra and catalogues are available to the community via the HOPS website.

CH 3 GHz Observations of Molecular Clouds along the Galactic Plane

The Astronomical Journal, 2005

Spectra in the CH 2 Π 1/2 , J=1/2, F=1-1 transition at 3335 MHz were obtained in three 5-point crosses centered on the Galactic plane at ℓ = 50 • , 100 • , and 110 • . The lines of sight traverse both Giant Molecular Clouds (GMCs) and local, smaller entities. This transition is a good tracer of low-density molecular gas and the line profiles are very similar to CO(1-0) data at nearly the same resolution. In addition, the CH 3335 MHz line can be used to calibrate the CO-H 2 conversion factor (X CO ) in low-density molecular gas. Although this technique underestimates X CO in GMCs, our results are within a factor of two of X CO values calibrated for GMCs by other techniques. The similarity of CH and CO line profiles, and that of X CO values derived from CH and more traditional techniques, implies that most of the molecular gas along the observed lines of sight is at relatively low densities (n ≤ 10 3 cm −3 ).

The Southern Galactic Plane Survey: H i Observations and Analysis

The Astrophysical Journal Supplement Series, 2005

We describe the H i component of the Southern Galactic Plane Survey (SGPS). The SGPS is a large-scale project to image at arcminute resolution the H i spectral line and 21 cm continuum emission in parts of the plane of the Milky Way. The survey covers Galactic longitudes 253 • ≤ l ≤ 358 • and latitudes |b| ≤ 1. • 5 (SGPS I), plus a first quadrant extension covering 5 • ≤ l ≤ 20 • and |b| ≤ 1. • 5 (SGPS II). The survey combines data from the Australia Telescope Compact Array and the Parkes Radio Telescope for sensitivity to angular scales ranging from 2 arcminutes to several degrees. The combined data cover 325 deg 2 and have an rms sensitivity of 1.6 K. Here we describe the H i observations and data reduction in detail, and present examples from the final data products. The complete dataset is publicly available through the Australia Telescope National Facility's H i Surveys archive. This dataset provides an unprecedented view of the neutral component of interstellar hydrogen in the inner Milky Way.

“Missing Link” Clouds in the Southern Galactic Plane Survey

The Astrophysical Journal, 2005

We present an automated routine to search for HI self-absorption features within the Southern Galactic Plane Survey (SGPS). The data were taken with the Australia Telescope Compact Array (ATCA) and the Parkes Radio Telescope and encompass 3 • × 105 • of sky in the Galactic plane. We apply our routine to this entire region and derive spin temperatures and column densities for 70 of the larger HISA complexes, finding spin temperatures ranging from 6-41 K with HI number densities of a few cm −3. These 'missing link' clouds fill in the spin temperature and density gaps between dense molecular clouds and diffuse atomic clouds. We compare the HI emission with 12 CO emission and find that ∼60% of detected HI self-absorption is correlated in space and in velocity with a

The Southern Galactic Plane Survey: The Test Region

The Astrophysical Journal, 2001

The Southern Galactic Plane Survey (SGPS) is a project to image the H i line emission and 1.4 GHz continuum in the fourth quadrant of the Milky Way at high resolution using the Australia Telescope Compact Array (ATCA) and the Parkes Radio Telescope. In this paper we describe the survey details and goals, present λ21-cm continuum data, and discuss H i absorption and emission characteristics of the SGPS Test Region (325. • 5 ≤ l ≤ 333. • 5; −0. • 5 ≤ b ≤ +3. • 5). We explore the effects of massive stars on the interstellar medium (ISM) through a study of H i shells and the H i environments of H ii regions and supernova remnants. We find an H i shell surrounding the H ii region RCW 94 which indicates that the region is embedded in a molecular cloud. We give lower limits for the kinematic distances to SNRs G327.4+0.4 and G330.2+1.0 of 4.3 kpc and 4.9 kpc, respectively. We find evidence of interaction with the surrounding H i for both of these remnants. We also present images of a possible new SNR G328.6-0.0. Additionally, we have discovered two small H i shells with no counterparts in continuum emission.

COMAP Early Science. VI. A First Look at the COMAP Galactic Plane Survey

The Astrophysical Journal

We present early results from the CO Mapping Array Project (COMAP) Galactic Plane Survey conducted between 2019 June and 2021 April, spanning 20° < ℓ < 40° in Galactic longitude and ∣b∣ < 1.°5 in Galactic latitude with an angular resolution of 4.′5. We present initial results from the first part of the survey, including the diffuse emission and spectral energy distributions of H ii regions and supernova remnants (SNRs). Using low- and high-frequency surveys to constrain free–free and thermal dust emission contributions, we find evidence of excess flux density at 30 GHz in six regions, which we interpret as anomalous microwave emission. Furthermore we model ultracompact H ii contributions using data from the 5 GHz CORNISH catalog and reject these as the cause of the 30 GHz excess. Six known SNRs are detected at 30 GHz, and we measure spectral indices consistent with the literature or show evidence of steepening. The flux density of the SNR W44 at 30 GHz is consistent with a ...

The AMANOGAWA-2SB Galactic Plane Survey I. Data on the Galactic Equator

Publications of the Astronomical Society of Japan, 2010

Using a waveguide-type sideband-separating receiver (2SB receiver) on the Tokyo-NRO 60-cm telescope (renamed the AMANOGAWA telescope), we carried out simultaneous observations in the 12 CO(J = 2−1) and 13 CO(J = 2−1) lines over the Galactic plane l = 10 • − 245 • along b = 0 • with a 3. ′ 75 grid. Using the 12 CO(J = 1 − 0) data of Dame et al. (2001), who used a beam size almost the same as ours, we show 12 CO(J = 2 − 1)/ 12 CO(J = 1 − 0) and 13 CO(J = 2 − 1)/ 12 CO(J = 2 − 1) intensity ratios on the l − v map and the intensity correlations among the 12 CO(J = 2 − 1), 13 CO(J = 2 − 1), and 12 CO(J = 1 − 0) lines. As a result, a linear correlation between 12 CO(J = 1 − 0) and 12 CO(J = 2 − 1) and a curve correlation between 12 CO(J = 2 − 1) and 13 CO(J = 2 − 1), as produced by most of the data, are found. We investigate these correlations with simple radiative transfer equations to ascertain a number of restrictions on the physical quantities of molecular gas on a galactic scale.