M. Normandeau

Bio: M. Normandeau is an academic researcher from University of Calgary. The author has contributed to research in topics: Perseus Arm & Star formation. The author has an hindex of 3, co-authored 3 publications receiving 193 citations.

A galactic chimney in the Perseus arm of the Milky Way

Abstract: Galaxies are surrounded by large haloes of hot gas which must be replenished as the gas cools. This has led to the concept of galactic 'chimneys'--cavities in the interstellar medium, created by multiple supernova explosions, that can act as conduits for the efficient transport of hot gas from a galaxy's disk to its halo. Here we present a high-resolution map of atomic hydrogen in the Perseus arm of our galaxy, which shows clear evidence for the existence of such a chimney. This chimney appears to have been formed by the energetic winds from a cluster of young massive stars, and may currently have reached the stage of bowing out into the halo.

The Dominion Radio Astrophysical Observatory Galactic Plane Survey Pilot Project: The W3/W4/W5/HB 3 Region

Abstract: The Dominion Radio Astrophysical Observatory, in collaboration with other sites, recently began a Galactic plane survey. The data from the pilot project for this survey are presented here. They cover the W3/W4/W5/HB 3 Galactic complex in the Perseus arm. Ten fields were observed to produce mosaic images of this region at two continuum frequencies, 408 and 1420 MHz, as well as in the 21 cm spectral line of atomic hydrogen at 127 velocities covering +55.5 to -153.9 km s-1. At 1420 MHz (continuum and spectral line), an area of approximately 8° × 6° (l × b) is imaged with a resolution of 100 × 114 (east-west by north-south) whereas, at 408 MHz, the coverage was 14° × 10° (l × b) with a resolution of 35 × 40 (east-west by north-south). The spectral-line data cube constitutes the highest resolution atomic hydrogen study of the entire complex to date. A wealth of large-scale filaments, arcs, bubbles, and shells is revealed.

A massive cometary cloud associated with IC 1805

Abstract: High-resolution, wide field imaging of 12CO, 21 cm line and continuum, and IRAS far-infrared emissions from the outer Galaxy have identified a massive cometary molecular cloud associated with IC 1805. The dense cloud is remnant molecular material within a large 102 pc cavity evacuated by the stellar winds and UV radiation field of the cluster O stars. A 37 pc long molecular tail points directly away from the sources of ionizing radiation and is likely due to the effective shielding of radiation by the dense gas and associated dust within the cometary head region. Maps of C18O J = 1-0 and CS J = 2-1 emissions are presented that constrain the column and mean volume densities within the cometary head region to 1022 cm-2 and 104 cm-3, respectively. A 1155 L☉ point source embedded within the dense gas of the cometary head region provides evidence for ongoing star formation that may have been triggered by shocks driven by the ionization front.

Young Massive Star Clusters

Abstract: Young massive clusters are dense aggregates of young stars that form the fundamental building blocks of galaxies. Several examples exist in the Milky Way Galaxy and the Local Group, but they are particularly abundant in starburst and interacting galaxies. The few young massive clusters that are close enough to resolve are of prime interest for studying the stellar mass function and the ecological interplay between stellar evolution and stellar dynamics. The distant unresolved clusters may be effectively used to study the star-cluster mass function, and they provide excellent constraints on the formation mechanisms of young cluster populations. Young massive clusters are expected to be the nurseries for many unusual objects, including a wide range of exotic stars and binaries. So far only a few such objects have been found in young massive clusters, although their older cousins, the globular clusters, are unusually rich in stellar exotica. In this review we focus on star clusters younger than $\sim100$ Myr, more than a few current crossing times old, and more massive than $\sim10^4$ \Msun, irrespective of cluster size or environment. We describe the global properties of the currently known young massive star clusters in the Local Group and beyond, and discuss the state of the art in observations and dynamical modeling of these systems. In order to make this review readable by observers, theorists, and computational astrophysicists, we also review the cross-disciplinary terminology.

The Canadian Galactic Plane Survey

Abstract: The Canadian Galactic Plane Survey (CGPS) is a project to combine radio, millimeter, and infrared surveys of the Galactic plane to provide arcminute-scale images of all major components of the interstellar medium over a large portion of the Galactic disk. We describe in detail the observations for the low-frequency component of the CGPS, the radio surveys carried out at the Dominion Radio Astrophysical Observatory (DRAO), and summarize the properties of the merged database of surveys that comprises the CGPS. The DRAO Synthesis Telescope surveys have imaged a 73° section of the Galactic plane, using ~85% of the telescope time between 1995 April and 2000 June. The observations provide simultaneous radio continuum images at two frequencies, 408 and 1420 MHz, and spectral-line images of the λ = 21 cm transition of neutral atomic hydrogen. In the radio continuum at 1420 MHz, dual-polarization receivers provide images in all four Stokes parameters. The surveys cover the region 742 < l < 1473, with latitude extent -36 < b < +56 at 1420 MHz and -67 < b < +87 at 408 MHz. By integration of data from single-antenna observations, the survey images provide complete information on all scales of emission structures down to the resolution limit, which is just below 1' × 1' csc δ at 1420 MHz and 34 × 34 csc δ at 408 MHz. The continuum images have a dynamic range of several thousand, yielding essentially noise-limited images with an rms of ~0.3 mJy beam-1 at 1420 MHz and ~3 mJy beam-1 at 408 MHz. The spectral-line data are noise limited with rms brightness temperature ΔTB ~ 3 K in a 0.82 km s-1 channel. The complete CGPS data set, including the DRAO surveys and data at similar resolution in 12CO (1–0) and in infrared emission from dust, all imaged to an identical Galactic coordinate grid and map projection, are being made publicly available through the Canadian Astronomy Data Centre.

A New Σ-D Relation and Its Application to the Galactic Supernova Remnant Distribution

Abstract: Technological advances in radio telescopes and X-ray instruments over the last 20 years have greatly increased the number of known supernova remnants (SNRs) and have led to a better determination of their properties. In particular, more SNRs now have reasonably determined distances. However, many of these distances were determined kinematically using old rotation curves (based on R☉ = 10 kpc and V☉ = 250 km s-1). A more modern rotation curve (based on R☉ = 8.5 kpc and V☉ = 220 km s-1) is used to verify or recalculate the distances to these remnants. We use a sample of 36 shell SNRs (37 including Cassiopeia A) with known distances to derive a new radio surface brightness-to-diameter (Σ-D) relation. The slopes derived here (β = -2.64 including Cas A, β = -2.38 without Cas A) are significantly flatter than those derived in previous studies. An independent test of the accuracy of the Σ-D relation was performed by using the extragalactic SNRs in the Large and Small Magellanic Clouds. The limitations of the Σ-D relation and the assumptions necessary for its use are discussed. A revised Galactic distribution of SNRs is presented based on the revised distances as well as those calculated from this Σ-D relation. A scaling method is employed to compensate for observational selection effects by computing scale factors based on individual telescope survey sensitivities, angular resolutions, and sky coverage. The radial distribution of the surface density of shell SNRs, corrected for selection effects, is presented and compared with previous works.

A New $\Sigma-D$ Relation and Its Application to the Galactic Supernova Remnant Distribution

Abstract: Technological advances in radio telescopes and X-ray instruments over the last 20 years have greatly increased the number of known supernova remnants (SNRs) and led to a better determination of their properties. In particular, more SNRs now have reasonably determined distances. However, many of these distances were determined kinematically using old rotation curves (based on $R_{\sun} = 10$ kpc and $V_{\sun} = 250$ km/s). A more modern rotation curve (based on $R_{\sun} = 8.5$ kpc and $V_{\sun} = 220$ km/s) is used to verify or recalculate the distances to these remnants. We use a sample of 36 shell SNRs (37 including Cas A) with known distances to derive a new radio surface brightness-to-diameter ($\Sigma-D$) relation. The slopes derived here ($\beta = -2.64$ including Cas A, $\beta = -2.38$ without Cas A) are significantly flatter than those derived in previous studies. An independent test of the accuracy of the $\Sigma-D$ relation was performed by using the extragalactic SNRs in the Large and Small Magellanic Clouds. The limitations of the $\Sigma-D$ relation and the assumptions necessary for its use are discussed. A revised Galactic distribution of SNRs is presented based on the revised distances as well as those calculated from this $\Sigma-D$ relation. A scaling method is employed to compensate for observational selection effects by computing scale factors based on individual telescope survey sensitivities, angular resolutions and sky coverage. The radial distribution of the surface density of shell SNRs, corrected for selection effects, is presented and compared to previous works.

The Five College Radio Astronomy Observatory CO Survey of the Outer Galaxy

Abstract: Images from the FCRAO CO Survey of the Outer Galaxy and a description of the calibration and processing of the data are presented. The survey is comprised of 1,696,80012CO J = 1-0 spectra sampled every 50'' between Galactic longitudes 10249 and 14154 and latitudes -303 and 541. The VLSR ranges from -153 to +40 km s-1 sampled every 0.81 km s-1 with a velocity resolution of 0.98 km s-1. The survey provides the highest spatial dynamic range imaging of the molecular interstellar medium ever obtained. We describe the observing procedure and characterize the random and systematic noise of the survey. The images reveal a wide diversity of spatial structure within the molecular interstellar medium. We identify several voids with angular extents of 2°-5° in diameter that may result from the cumulative interactions of ultraviolet radiation fields and stellar winds from newborn massive stars with ambient interstellar gas. It is demonstrated that a significant fraction of the integrated intensity summed over the survey field originates from regions with low peak antenna temperature and low column density assuming a conversion between integrated CO emission and molecular hydrogen column density. Assuming kinematic distances to the observed emission, we derive the radial profile of mass surface density and the variations of the z midplane and scale height of the molecular gas distribution with galactocentric radius.