Dominion Astrophysical Observatory

We present a three-dimensional model of the positions of 20 stars in the field of the Cepheid UMi (Polaris) – 18 main sequence stars (spectral types A0–G0 V), the K-giant HD 6319 (K2 III) and Polaris itself (F8 Ib) – which was created using the 3D calculator Desmos 3D, based on the calculated U, V and W components of the full velocity vector of the stars in the Galactic coordinate system. In this paper, stellar radial velocity estimates from Usenko et al. (2023) were used. Two versions of the U, V, and W components were calculated based on Gaia DR3 parallaxes and photometric parallaxes. The resulting 3D image showed that, in both scenarios, 15 main-sequence stars, a K-giant, and Polaris form a noticeable clamp, while three stars (HD 14718, HD 90162, and HD 11696) are located outside of it. HD 14718 and HD 90162 belong to the thick disk, while HD 11696 is a remnant of a possible open cluster in Polaris’s field. The K-giant HD 6319 is located inside the clamp and quite close to the Cepheid, and it is quite possible that this clamp is part of the main component of the probable open cluster Polaris, dissolved in the field of the Cepheid. Using a 3D calculator to construct a spatial image of stars may serve as a good tool for studying the structure and dynamics of open clusters in the future.

The sensitivity and field of view of the Canadian Hydrogen Intensity Mapping Experiment (CHIME) has enabled its fast radio burst (FRB) backend to detect thousands of FRBs. However, the low angular resolution of CHIME prevents it from localizing most FRBs to their host galaxies. Very long baseline interferometry (VLBI) can readily provide the subarcsecond resolution needed to localize many FRBs to their hosts. Thus, we developed TONE: an interferometric array of eight 6-m dishes to serve as a pathfinder for the CHIME/FRB Outriggers project, which will use wide field-of-view cylinders to determine the sky positions for a large sample of FRBs, revealing their positions within their host galaxies to subarcsecond precision. In the meantime, TONE’s [Formula: see text] [Formula: see text]km baseline with CHIME proves to be an excellent testbed for the development and characterization of single-pulse VLBI techniques at the time of discovery. This work describes the TONE instrument, its sensitivity, and its astrometric precision in single-pulse VLBI. We believe that our astrometric errors are dominated by uncertainties in the clock measurements which build up between successive Crab pulsar calibrations which happen every [Formula: see text] [Formula: see text]h; the wider fields-of-view and higher sensitivity of the Outriggers will provide opportunities for higher-cadence calibration. At present, CHIME-TONE localizations of the Crab pulsar yield systematic one-dimensional localization errors of [Formula: see text] [Formula: see text]asec — considerably better than the resolution achievable with seeing limited followup observations in the optical/near-infrared from the ground.

We present a comparison of the presence and properties of dust in two distinct phases of the Milky Way’s interstellar medium: the warm neutral medium (WNM) and the warm ionized medium (WIM). Using distant pulsars at high Galactic latitudes and vertical distance (∣b∣ > 40°, ) as probes, we measure their dispersion measures and the neutral hydrogen component of the warm neutral medium (WNMH I) using H i column density. Together with dust intensity along these same sightlines, we separate the respective dust contributions of each ISM phase in order to determine whether the ionized component contributes to the dust signal. We measure the temperature (T), spectral index (β), and dust opacity (τ/N H) in both phases. We find K, β (WNMH I) = 1.5 ± 0.4, and τ 353/N H (WNMH I) = (1.0 ± 0.1) × 10−26 cm2. Assuming that the temperature and spectral index are the same in both the WNMH I and WIM, and given our simple model that widely separated lines of sight can be fit together, we find evidence that there is a dust signal associated with the ionized gas and , which is about 3 times smaller than τ 353/N H (WNMH I). We are 80% confident that is at least 2 times smaller than τ 353/N H (WNMH I).

The Southern HII Region Discovery Survey is an Australia Telescope Compact Array 4-6 and 8-10 GHz radio continuum and radio recombination line survey of Milky Way HII regions (Wenger et al., 2021). This data archive contains all relevant intermediate data products from the final SHRDS data release (the Full Catalog). For each observed HII region and calibrator field, this archive contains (1) a 4 GHz bandwidth, full-Stokes, multi-scale, multi-frequency synthesis (MS-MFS) continuum FITS image, (2) up to sixteen 256 MHz bandwidth, full-Stokes, MS-MFS continuum FITS images covering the full 4 GHz bandwidth, (3) a Stokes I MS-MFS FITS image of each RRL transition, (4) a Stokes I multi-scale FITS data cube of each RRL transition, and (5) a FITS image containing the watershed segmentation region for each identified HII region at each observed frequency. The archive also includes the relevant residual images/cubes and primary beam images for all of these data products, as well as all of the images and cubes smoothed to a common angular resolution.

We propose to continue the PULSE@Parkes project in which high school students from Australia and around the World use the Parkes radio telescope in a remote observing model to observe and analyse pulsar data. The data from some PULSE@Parkes observations are used to support the FERMI Gamma ray mission, other observations supplement the P456 Pulsar Timing Array project and the remainder were chosen in order to make a detailed analysis of pulsar timing irregularities and intermittency.

Abstract Observations that span a broad range of wavelengths are used to examine asymmetries in the disk of the nearby late-type spiral galaxy NGC 247. The northern spiral arm is over-luminous at all wavelengths when compared with other parts of the galaxy at similar galactocentric radii, while the density of very luminous red stars in the void that is immediately south of this arm matches that in other parts of the disk at the same galactocentric radius. Two bubbles with spatial extents of many kiloparsecs are identified in the disk, and many of the young stars in the southern disk of NGC 247 are located in the walls of these structures. Dynamical age estimates of these bubbles coincide with the last large-scale star formation event in the nucleus, suggesting that there was large-scale star formation throughout the disk of NGC 247 a few hundred megayears in the past. Morphological similarities are seen with the classical lop-sided galaxy NGC 4027, and it is concluded that NGC 247 is a significantly lop-sided spiral galaxy. The void in the northern disk is then the area between the main body of the disk and the northern arm viewed in projection. The implications of a lop-sided morphology for NGC 247 in the context of interactions with its nearby starburst galaxy companion NGC 253 are discussed.

In 1957 the site for the Dominion Radio Astrophysical Observatory was chosen for its minimal radio frequency interference (RFI) from nearby human activities. The efficacy of the site has since been compromised by having a full staff of 40+ engineers, technologists, and scientists located directly adjacent to the telescopes. The site is visited daily by temporary workers, the general public, couriers, and contractors. Guided tours are offered 10AM–5PM every weekend from April through October, significantly increasing the number of visitors. The encroachment of humans on site brings RFI that is carried on their persons, such as cell phones, tablets, smart watches, and cameras. We built a device to detect cellular uplink activity as a means to demonstrating an affordable off-the-shelf solution for finding bad actors on site who have not powered off their cellular devices. We describe the cell-phone buster device, show the results from a brief survey of on-site cellular activity, and discuss plans to expand the capabilities to detect Wi-Fi, Bluetooth, and other RF emissions from personal electronic devices on site.

Abstract Spectra that cover wavelengths from 0.6 to 1.1 μm are used to examine the behavior of emission and absorption features in a contiguous 22 × 300 arcsec2 region centered on the nearby dwarf galaxy NGC 55. This area includes the two largest star-forming complexes in the galaxy, as well as other star-forming structures in the little-explored northwest part of the disk. Based on the relative strengths of various emission features measured over spatial scales of many tens of parsecs, it is concluded that the ionization states and sulphur abundances in most of the star-forming regions near the center of NGC 55 are similar. A large star-forming region is identified in the northwest part of the disk at a projected distance of ∼1 kpc from the center of the galaxy that has distinct ionization properties. In addition to tracing areas of present-day star formation, the spectra are also used to identify fossil star-forming regions by mapping the depth of the near-infrared Ca triplet. One such area is identified near the intersection of the major and minor axes. There is a corresponding concentration of bright red stars in archival [3.6] and [4.5] images that are part of a mass concentration that is structurally distinct from the surrounding disk. It is suggested that the area near the intersection of the major and minor axes in NGC 55 is a proto-nucleus. The spectra of bright unresolved sources that are blended stellar asterisms, compact H ii regions, and star clusters are also discussed. The spectra of some of the H ii regions contain Ca triplet absorption lines, signaling a concentration of stars in the resolution element that span many millions of years. Six of the unresolved sources have spectroscopic characteristics that are indicative of C stars embedded in intermediate-age clusters, and these are likely compact star clusters that are analogous to those in the Large Magellanic Cloud. The peculiar properties of NGC 55 have been well documented in the literature, and it is argued that these may indicate that NGC 55 is transforming into a dwarf lenticular galaxy.

ABSTRACT We present a Chandra and XMM–Newton study of the supernova remnant (SNR) CTB 37B, along with archival radio observations. In radio wavelengths, the SNR CTB 37B is an incomplete shell showing bright emission from the eastern side, while the X-ray morphology shows diffuse emission from regions surrounding the magnetar CXOU J171405.7–381031. We used archival H i absorption measurements to constrain the distance to the remnant and obtain D = 9.8 ± 1.5 kpc. The X-ray spectrum of the remnant is described by a thermal model in the 1–5 keV energy range, with a temperature of kT = 1.3 ± 0.1 keV. The abundances from the spectral fits are consistent with being solar or sub-solar. A small region of diffuse emission is seen to the southern side of the remnant, best fitted by a non-thermal spectrum with an unusually hard photon index of Γ = 1.3 ± 0.3. Assuming a distance of 9.8 kpc to the SNR, we infer a shock velocity of Vs = 915 ± 70 km s−1 and an explosion energy of E = (1.8 ± 0.6) × 1050 erg. The overall imaging and spectral properties of CTB 37B favour the interpretation of a young SNR (≲6200 yr old), propagating in a low-density medium under the assumption of a Sedov evolutionary phase.