Apparent Motion of the Circumstellar Envelope of CQ Tau in Scattered Light

The study of spiral structures in protoplanetary disks is of great importance for understanding the processes in the disks, including planet formation. Bright spiral arms were detected in the disk of young star CQ Tau by Uyama et al. in the H and L bands. The spiral arms are located inside the gap in millimeter-sized dust, discovered earlier using Atacama Large Millimeter/submillimeter Array observations. To explain the gap, Ubeira Gabellini et al. proposed the existence of a planet with the semimajor axis of 20 au. We obtained multi-epoch observations of a spiral feature in the circumstellar envelope of CQ Tau in the I c band using a novel technique of differential speckle polarimetry. The observations covering a period from 2015 to 2021 allow us to estimate the pattern speed of the spiral: −0.°2 ± 1.°1 yr−1 (68% credible interval; positive value indicates counterclockwise rotation), assuming a face-on orientation of the disk. This speed is significantly smaller than expected for a companion-induced spiral, if the perturbing body has a semimajor axis of 20 au. We emphasize that the morphology of the spiral structure is likely to be strongly affected by shadows of a misaligned inner disk detected by Eisner et al.

Possible algal origin and life cycle of Ediacaran Doushantuo microfossils with dextral spiral structure

In Ediacaran shallow-water dolomites of the Doushantuo Formation (ca. 570 Ma) of southern China, scarce phosphatized microfossils consisting of clusters of coil-like spheroids called Spiralicellula bulbifera and co-occurring spherical forms with helically arranged holes named Helicoforamina wenganica are interpreted to belong to the same taxon because both have a similar relative abundance and both, uniquely in the assemblage, exhibit a consistent dextral spiral feature—the oldest known fossil examples of fixed asymmetry. Thus, we interpret them as different stages of sexual and asexual life cycles in which the spiral structure was maintained throughout most of the developmental phases. While they can be placed with the acritarchs, we suggest they are a chlorophycean green alga, and like many Ediacaran macrofossils, may represent an extinct clade. This is compatible with the shoal-water marine depositional environment in which they lived, as it would have favored photosynthetic organisms over others kinds of encysting non-metazoan protists. This setting militates against their interpretation as putative embryos which has been put forward for a variety of forms co-occurring in the microfossil assemblage. The multiple affinities of the strikingly diverse biota remain far from resolved, but algal origins warrant further consideration.

The Carina Spiral Feature — an investigation based on a complete magnitude-limited uvbyβ sample

This contribution reflects a detailed overall survey of the Carina Spiral Feature based on uvbyβ photometry of O- and B-type stars. New observations are combined with all data currently available, to collate a complete homogeneous magnitude-limited uvbyβ database. A uniform procedure is applied to obtain the photometry-derived stellar parameters. A homogeneous distance scale is established to the most prominent young structures in the field and the distribution of the visual extinction is analyzed.

Merger in M31’s Bulge & 3-D Accretion – A BVRI CCD Study at Kiso –

By contrast-enhancing and colour-excess analyses of BV RI CCD images of the central 12’.5 × 12’.5 region of M31 taken with the Kiso 105 cm Schmidt telescope, we found a “face-on” spiral feature of dark clouds, which are associated with Hα spirals. The feature can be understood as being due to accretion of gas clouds from companion galaxies and/or from a merger galaxy in the past 108–9 years.

The Galactic Magnetic Field from Pulsar Rotation Measures

Pulsar rotation measures have been used to investigate the structure of the local Galactic magnetic field. The Galactic field is found to be concentrated in the spiral arms and hence to be a spiral field. From the pulsars within 2kpc of the Sun, the field in the local spiral feature was modelled with Gaussian profiles in altitude and azimuth. In this model the field has a peak strength of 4.3 ± 0.2 μGauss directed towards Galactic longitude l = 73°±6°.