An analysis of the kinematics of NGC 6720 is performed on the commissioning data obtained with SITELLE, the Canada-France-Hawaii Telescope's new imaging Fourier transform spectrometer. In order to ...measure carefully the small broadening effect of a shell expansion on an unresolved emission line, we have determined a computationally robust implementation of the convolution of a Gaussian with a sinc instrumental line shape which avoids arithmetic overflows. This model can be used to measure line broadening of typically a few km s super( -1) even at low spectral resolution (R < 5000). We have also designed the corresponding set of Gaussian apodizing functions that are now used by ORBS, the SITELLE's reduction pipeline. We have implemented this model in ORCS, a fitting engine for SITELLE's data, and used it to derive the SII density map of the central part of the nebula. The study of the broadening of the NII lines shows that the main ring and the central lobe are two different shells with different expansion velocities. We have also derived deep and spatially resolved velocity maps of the halo in NII and Ha and found that the brightest bubbles are originating from two bipolar structures with a velocity difference of more than 35 km s super( -1) lying at the poles of a possibly unique halo shell expanding at a velocity of more than 15 km s super( -1).
Abstract
We present an overview of SITELLE, an Imaging Fourier Transform Spectrometer (iFTS) available at the 3.6-m Canada–France–Hawaii Telescope. SITELLE is a Michelson-type interferometer able to ...reconstruct the spectrum of every light source within its 11 arcmin field of view in filter-selected bands of the visible (350–900 nm). The spectral resolution can be adjusted up to R = 10 000 and the spatial resolution is seeing-limited and sampled at 0.32 arcsec pixel−1. We describe the design of the instrument as well as the data reduction and analysis process. To illustrate SITELLE’s capabilities, we present some of the data obtained during and since the 2015 August commissioning run. In particular, we demonstrate its ability to separate the components of the O ii λλ 3726,29 doublet in Orion and to reach R = 9500 around Hα; to detect diffuse emission at a level of 4 × 10−17 erg cm−2 s−1 arcsec−2; to obtain integrated spectra of stellar absorption lines in galaxies despite the well-known multiplex disadvantage of the iFTS and to detect emission-line galaxies at different redshifts.
Abstract We present new high-spectral-resolution observations ( R = λ /Δ λ = 7000) of the filamentary nebula surrounding NGC 1275, the central galaxy of the Perseus cluster. These observations have ...been obtained with SITELLE, an imaging Fourier transform spectrometer installed on the Canada–France–Hawai Telescope with a field of view of 11 ′ × 11 ′ , encapsulating the entire filamentary structure of ionized gas despite its large size of 80 kpc × 50 kpc. Here, we present renewed fluxes, velocities, and velocity dispersion maps that show in great detail the kinematics of the optical nebula at S ii λ 6716, S ii λ 6731, N ii λ 6584, H α (6563 Å), and N ii λ 6548. These maps reveal the existence of a bright flattened disk-shaped structure in the core extending to r ∼10 kpc and dominated by a chaotic velocity field. This structure is located in the wake of X-ray cavities and characterized by a high mean velocity dispersion of 134 km s −1 . The disk-shaped structure is surrounded by an extended array of filaments spread out to r ∼ 50 kpc that are 10 times fainter in flux, remarkably quiescent, and have a uniform mean velocity dispersion of 44 km s −1 . This stability is puzzling given that the cluster core exhibits several energetic phenomena. Based on these results, we argue that there are two mechanisms that form multiphase gas in clusters of galaxies: a first triggered in the wake of X-ray cavities leading to more turbulent multiphase gas and a second, distinct mechanism, that is gentle and leads to large-scale multiphase gas spreading throughout the core.
Abstract We present JWST observations of the Crab Nebula, the iconic remnant of the historical SN 1054. The observations include NIRCam and MIRI imaging mosaics plus MIRI/MRS spectra that probe two ...select locations within the ejecta filaments. We derive a high-resolution map of dust emission and show that the grains are concentrated in the innermost, high-density filaments. These dense filaments coincide with multiple synchrotron bays around the periphery of the Crab's pulsar wind nebula (PWN). We measure synchrotron spectral index changes in small-scale features within the PWN’s torus region, including the well-known knot and wisp structures. The index variations are consistent with Doppler boosting of emission from particles with a broken power-law distribution, providing the first direct evidence that the curvature in the particle injection spectrum is tied to the acceleration mechanism at the termination shock. We detect multiple nickel and iron lines in the ejecta filaments and use photoionization models to derive nickel-to-iron abundance ratios that are a factor of 3–8 higher than the solar ratio. We also find that the previously reported order-of-magnitude higher Ni/Fe values from optical data are consistent with the lower values from JWST when we reanalyze the optical emission using updated atomic data and account for local extinction from dust. We discuss the implications of our results for understanding the nature of the explosion that produced the Crab Nebula and conclude that the observational properties are most consistent with a low-mass Fe core-collapse supernova, even though an electron-capture explosion cannot be ruled out.
Abstract
We have carried out optical observations of the northeastern part of the supernova remnant IC 443 using the Canada–France–Hawaii Telescope imaging spectrograph SITELLE. The observations ...consist of three multispectral cubes covering an 11′ × 11′ area allowing the investigation of both the spatial and spectral variation of nine emission lines: O ii λλ3726 + 3729, O iii λλ4959, 5007, H β, H α, N ii λλ6548, 6583, and S ii λλ6716, 6731. Extinction measurement from the H α/ H β shows significant variation across the observed region with E(B − V) = 0.8–1.1. Electron density measurements using S ii lines indicate densities ranging from 100 up to 2500 cm−3. Models computed with the shock modelling code mappings are presented and compared with the observations. A combination of complete shock model and truncated ones is required in order to explain the observed spectrum. The shock velocities found in IC 443 are between 20 and 150 km s−1, with 75 km s−1 being the most prominent velocity. The pre-shock number density varies from 20 to 60 cm−3. A single set of abundances close to solar values combined with varying shock parameters (shock velocity, pre-shock density, and shock age) is sufficient to explain the great variation of line intensities observed in IC 443. Despite the relatively modest spectral resolution of the data (R ∼ 1500 at H α), we clearly separate the red and blue velocity components of the expanding nebula, which show significant morphological differences.
A hyperspectral view of Cassiopeia A Alarie, Alexandre; Bilodeau, Antoine; Drissen, Laurent
Monthly notices of the Royal Astronomical Society,
07/2014, Letnik:
441, Številka:
4
Journal Article
Recenzirano
Odprti dostop
We used the imaging Fourier transform spectrometer Spectromètre Imageur de l'Observatoire du Mont-Mégantic (SpIOMM) to obtain hyperspectral cubes of the young supernova remnant Cassiopeia A (Cas A). ...The cubes contain over 5000 spatially resolved spectra covering the spectral range 6480–7050 Å. We first investigate the slow-moving N-rich quasi-stationary flocculi by measuring their radial velocity as well as the N ii λ6583/Hα ratio. No correlation between their radial velocity and N ii λ6583/Hα ratio with their location has been found. We used multi-epoch observations from the Hubble Space Telescope to create a proper motion map, showing the displacement of several filaments over the most part of Cas A. Combining data from SpIOMM and Hubble, we re-evaluate the distance to Cas A and obtained 3.33 ± 0.10 kpc, which is in good agreement with previous estimates. Finally, we obtain a three-dimensional spatial view of the S ii λλ6716, 6731 emissions showing their location, expansion velocity and the S ii doublet line ratio for multiple locations in the remnant. The velocity asymmetry reported by previous analyses is clearly visible. Also, the S ii doublet ratio (with a mean value of 0.5 ± 0.2) indicates a very high and variable electronic density throughout the remnant.
Abstract
We have developed a new numerical algorithm to study the joint evolution of galaxies and the intergalactic medium (IGM) in a cosmological context, with the specific goal of studying the ...deposition and dispersion of metals in the IGM. This algorithm combines a standard gasdynamical algorithm to simulate the evolution of the IGM, a semi-analytical model to describe the evolution of galaxies, and prescriptions for galaxy formation, accretion, mergers, and tidal disruption. The main goal in designing this algorithm was performance. In its current version, the algorithm can simulate the evolution of cosmological volumes containing thousands of galaxies in a few days, using between 12 and 32 processors. This algorithm is particularly suited for parameter surveys (both numerical parameters and physical parameters) since a large number of simulations can be completed in a fairly short amount of time. Furthermore, the algorithm provides a platform for the development and testing of new treatments of subgrid physics, which could then be implemented into other algorithms. In this paper, we describe the algorithm and present, for illustration, two simulations of the evolution of a (20 Mpc)
3
cosmological volume containing ∼1200 galaxies at
z
= 0.
Abstract
We present a detailed description of the wavelength, astrometric and photometric calibration plan for SITELLE, the imaging Fourier transform spectrometer attached to the Canada–France–Hawaii ...telescope, based on observations of a red (647–685 nm) data cube of the central region (11 arcmin × 11 arcmin) of M 31. The first application, presented in this paper is a radial-velocity catalogue (with uncertainties of ∼2–6 km s−1) of nearly 800 emission-line point-like sources, including ∼450 new discoveries. Most of the sources are likely planetary nebulae, although we also detect five novae (having erupted in the first eight months of 2016) and one new supernova remnant candidate.
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