Observatoire Du Mont Megantic Research Articles

Kinematics and mass modelling of M33: Hα observations

As part of a long-term project to revisit the kinematics and dynamics of the large disc galaxies of the Local Group, we present the first deep, wide-field (42' x 56') 3D-spectroscopic survey of the ionized gas disc of Messier 33. Fabry-Perot interferometry has been used to map its Ha distribution and kinematics at unprecedented angular resolution (<3'') and resolving power (12600), with the 1.6m telescope at the Observatoire du Mont Megantic. The ionized gas distribution follows a complex, large-scale spiral structure, unsurprisingly coincident with the already-known spiral structures of the neutral and molecular gas discs. The kinematical analysis of the velocity field shows that the rotation center of the Ha disc is distant from the photometric center by 170 pc (sky projected distance) and that the kinematical major-axis position angle and disc inclination are in excellent agreement with photometric values. The Ha rotation curve agrees very well with the HI rotation curves for 0 < R < 6.5 kpc, but the Ha velocities are 10-20 km/s higher for R > 6.5 kpc. The reason for this discrepancy is not well understood. The velocity dispersion profile is relatively flat around 16 km/s, which is at the low end of velocity dispersions of nearby star-forming galactic discs. A strong relation is also found between the Ha velocity dispersion and the Ha intensity. Mass models were obtained using the Ha rotation curve but, as expected, the dark matter halo's parameters are not very well constrained since the optical rotation curve only extends out to 8 kpc.

STAR FORMATION NEAR BERKELEY 59: EMBEDDED PROTOSTARS

A group of suspected protostars in a dark cloud northwest of the young (~2 Myr) cluster Berkeley 59 and two sources in a pillar south of the cluster have been studied in order to determine their evolutionary stages and ascertain whether their formation was triggered by Berkeley 59. Narrowband near-infrared observations from the Observatoire du Mont Megantic, 12CO (J = 3-2) and SCUBA-2 (450 and 850 μm) observations from the JCMT, 2MASS, and WISE images, and data extracted from the IPHAS survey catalog were used. Of 12 sources studied, two are Class I objects, while three others are flat/Class II, one of which is a T Tauri candidate. A weak CO outflow and two potential starless cores are present in the cloud, while the pillar possesses substructure at different velocities, with no outflows present. The CO spectra of both regions show peaks in the range v LSR = –15 to –17 km s–1, which agrees with the velocity adopted for Berkeley 59 (–15.7 km s–1), while spectral energy distribution models yield an average interstellar extinction AV and distance of 15 ± 2 mag and 830 ± 120 pc, respectively, for the cloud, and 6.9 mag and 912 pc for the pillar, indicating that the regions are in the same vicinity as Berkeley 59. The formation of the pillar source appears to have been triggered by Berkeley 59. It is unclear whether Berkeley 59 triggered the association's formation.

Multi‐ionic Kinematical Study of the HiiRegion Sharpless 2‐158

The Sh 2-158 gas complex kinematics is analyzed using four lines from three different ions (Hα, [O III] λ5007, and [S II] λλ6727, 6731) and the CO 1-0 line. The O++ and S+ data cubes were obtained using MOS FP at the CFHT, while the H+ data cube was obtained using FaNTOmM at the Observatoire du mont Megantic. More than 200,000 spectra (S/N ≥ 5) were obtained. Maps of the radial velocity fields, the velocity line width field, and the electronic density field are discussed. All ionic mean radial velocities are blueshifted with respect to the molecular cloud (VLSR = -55.16 ± 0.02 km s-1), more so as one goes from [S II] to Hα to [O III]. Two flows originating from the molecular cloud are identified. The encounter of the two flows, and possibly stellar winds, induces turbulence near the stars, causing larger line widths (≈10 km s-1) than elsewhere in the field. The mean [S II] line width is smaller than the mean [O III] line width, which is smaller than the mean Hα line width. Those differences between the ions are explained by the smaller [O III] Stromgren sphere compared to the Hα Stromgren sphere and the restriction of [S II] to a shell of gas near the molecular cloud. The most probable density value is 225 ± 25 cm-3. The observations are mostly in agreement with the Champagne model. A geometrical model is proposed for Sh 2-158.

Turbulent outflows from [WC]-type nuclei of planetary nebulae

Using spectroscopic observations taken at the Observatoire de Haute-Provence (France) and the Observatoire du mont Megantic (Canada), we describe wind fluctuations in the [WC 8]-type central star of the planetary nebula NGC 40, HD 826, which was observed intensively during 22 nights. Moving features seen on the top of the Ciii λ 5696 and Civ $\lambda\lambda$5801/12 (+Ciii λ 5826) emission lines are interpreted as outflowing blobswhich are radially accelerated outwards in the Wolf-Rayet wind. The amplitudes of the variations range up to 25-30% of the adjacent continuum flux, over timescales of hours. The variabilities of both lines are quite well correlated, although they are somewhat weaker for the Civ complex. Subpeaks (or gaps) on the top of the Ciii line generally move towards the nearest line edge in a symmetric fashion in the blue and the red. Kinematic parameters of the blobs were derived and compared to those observed for massive and other low-mass Wolf-Rayet stars. Especially impressive are the significantly larger observed maximum radial acceleration values of the blobs, compared to those already reported for massive WC 5-9, or low-mass [WC 9] stars. This is attributed to the very small stellar radius of HD 826. In addition the β velocity field is found to possibly underestimate the true gradient within the stellar wind flow. On the whole, the wind of HD 826 is highly stochastically variable on a very short time-scale. This supports a turbulent origin.

THE MONTREAL NEAR-INFRARED CAMERA

ABSTRACT A near-infrard (10 microns-2.5 microns) camera in use at the Canada-France-Hawaii Telescope and at the Observatoire du Mont Megantic 1.6 m telescope is described. The camera is based on a NICMOS3 256X256 HgCdTe array detector. While it is used for broad-band imaging and polarimetry through the standard J, H, and K filters, a distinguishing feature of its design is the use of circular variable filters for spectral line imaging in regions of strong continuum emission. The control system was designed to minimize overhead and be simple to use and to maintain. The performance of the instrument is described and illustrated with images of the H2 emission from the Cepheus A star formation region and a K-band image of the environment of the quasar 3C 345.

Image restoration and photometric monitoring of the gravitational lens Q2237+0305

view Abstract Citations (24) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Image Restoration and Photometric Monitoring of the Gravitational Lens Q2237+0305 Houde, M. ; Racine, R. Abstract An image processing technique based on Lucy's algorithm [AJ, 79,745 (1974)] was developed and tested on CCD frames of Q 2237 + 0305 obtained at Observatoire du mont Megantic on 1990 July 27 in FWHM ~1.5" seeing and on 1990 October 16 (FWHM ~1.7"). Magnitudes were successfully obtained for the four components of this image which all lie within 1 arcsec of the lensing galaxy nucleus. Historical light curves (1986-1991) are constructed for the four images with the implementation of a "bootstrap" method. This also allows refinements to the estimates of differential extinction between the components and can detect microlensing events at the < 0.1 mag level. The results of our photometry agree well with the trends defined by other observations taken in superior seeing at the same epoch. Publication: The Astronomical Journal Pub Date: February 1994 DOI: 10.1086/116868 Bibcode: 1994AJ....107..466H Keywords: Astronomical Photography; Astronomical Photometry; Gravitational Lenses; Image Processing; Image Reconstruction; Algorithms; Charge Coupled Devices; Light Curve; Astronomy; GRAVITAIONAL LENSING; TECHNIQUES: IMAGE PROCESSING; QUASARS: INDIVIDUAL: Q2237; 0305 full text sources ADS | data products NED (5) SIMBAD (2)