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Author(s): Karen J. Meech (corresponding author) [1]; Robert Weryk [1]; Marco Micheli [2, 3]; Jan T. Kleyna [1]; Olivier R. Hainaut [4]; Robert Jedicke [1]; Richard J. Wainscoat [1]; Kenneth [...]

We present a search for disturbed, candidate ram pressure stripping galaxies across more than 50 spectroscopically selected SDSS groups and clusters. 48 ram pressure candidates are visually identified in these systems using high-quality UNIONS imaging from the Canada-France-Hawaii Telescope, covering |${\sim }6200\, \mathrm{deg^2}$| and |${\sim }2800\, \mathrm{deg^2}$| in the u - and r -bands, respectively. Ram pressure candidates are found in groups and clusters spanning a wide range in halo mass and include ∼30 ram pressure candidates in the group regime (Mh < 1014). The observed frequency of ram pressure candidates shows substantial scatter with group/cluster mass, but on average is larger in clusters (⁠|$M_h \ge 10^{14}\, \mathrm{M_\odot }$|⁠) than groups (⁠|$M_h \lt 10^{14}\, \mathrm{M_\odot }$|⁠) by a factor of ∼2. We find that ram pressure candidates are most commonly low-mass galaxies and have enhanced star formation rates relative to star-forming field galaxies. The enhancement in star formation is largely independent of galaxy mass and strongest for galaxies in clusters. As a result of the large survey footprint and excellent image quality from UNIONS, we are able to identify disturbed galaxies, potentially affected by ram pressure stripping, across a wide range of host environment. [ABSTRACT FROM AUTHOR]

We present a nuclear transient event, PS1-13cbe, that was first discovered in the Pan-STARRS1 survey in 2013. The outburst occurred in the nucleus of the galaxy SDSS J222153.87+003054.2 at z  = 0.123 55, which was classified as a Seyfert 2 in a pre-outburst archival Sloan Digital Sky Survey (SDSS) spectrum. PS1-13cbe showed the appearance of strong broad H α and H β emission lines and a non-stellar continuum in a Magellan spectrum taken 57 d after the peak of the outburst that resembled the characteristics of a Seyfert 1. These broad lines were not present in the SDSS spectrum taken a decade earlier and faded away within 2 yr, as observed in several late-time MDM spectra. We argue that the dramatic appearance and disappearance of the broad lines and a factor of ∼8 increase in the optical continuum are most likely caused by variability in the pre-existing accretion disc than a tidal disruption event, supernova, or variable obscuration. The time-scale for the turn-on of the optical emission of ∼70 d observed in this transient is among the shortest observed in a 'changing-look' active galactic nucleus. [ABSTRACT FROM AUTHOR]

A large sample of white dwarfs is selected by both proper motion and colours from the Pan-STARRS 1 |$3\pi$| Steradian Survey Processing Version 2 to construct the white dwarf luminosity functions of the discs and halo in the solar neighbourhood. Four-parameter astrometric solutions were recomputed from the epoch data. The generalized maximum volume method is then used to calculate the density of the populations. After removal of crowded areas near the Galactic plane and centre, the final sky area used by this work is 7.833 sr, which is |$83{{\ \rm per\ cent}}$| of the |$3\pi$| sky and |$62{{\ \rm per\ cent}}$| of the whole sky. By dividing the sky using Voronoi tessellation, photometric and astrometric uncertainties are recomputed at each step of the integration to improve the accuracy of the maximum volume. Interstellar reddening is considered throughout the work. We find a disc-to-halo white dwarf ratio of about 100. [ABSTRACT FROM AUTHOR]

We present a panoramic map of the entire Milky Way halo north of δ ~ -30× (~30 000 deg²), constructed by applying the matched-filter technique to the Pan-STARRS1 3π Survey data set. Using single-epoch photometry reaching to g~22, we are sensitive to stellar substructures with heliocentric distances between 3.5 and ~35 kpc. We recover almost all previously reported streams in this volume and demonstrate that several of these are significantly more extended than earlier data sets have indicated. In addition, we also report five new candidate stellar streams. One of these features appears significantly broader and more luminous than the others and is likely the remnant of a dwarf galaxy. The other four streams are consistent with a globular cluster origin, and three of these are rather short in projection (≲10), suggesting that streams like Ophiuchus may not be that rare. Finally, a significant number of more marginal substructures are also revealed by our analysis; many of these features can also be discerned in matched-filter maps produced by other authors from SDSS data, and hence they are very likely to be genuine. However, the extant 3π data is currently too shallow to determine their properties or produce convincing colour-magnitude diagrams. The global view of the Milky Way provided by Pan-STARRS1 provides further evidence for the important role of both globular cluster disruption and dwarf galaxy accretion in building the Milky Way's stellar halo. [ABSTRACT FROM AUTHOR]

We present the fiducial sequences of a sample of Galactic star clusters in the five bands of the Pan-STARRS1 (PS1) photometric system (gP1, rP1, iP1, zP1, and yP1). These empirical sequences – which include the red giant and sub-giant branches, the main sequence, and the horizontal branch – were defined from deep colour–magnitude diagrams reaching below the oldest main-sequence turn-offs of 13 globular and 3 old open clusters covering a wide range of metallicities ( − 2.4 ≲ [Fe/H] ≲ +0.4). We find excellent agreement for the nine clusters in common with previous studies in similar photometric systems when transformed to the PS1 system. Because the photometric and spectroscopic properties of these stellar populations are accurately known, the fiducials provide a solid basis for the interpretation of observations in the PS1 system, as well as valuable constraints to improve the empirical colour–Teff relations. [ABSTRACT FROM PUBLISHER]

We report the discovery of two new dwarf galaxies, Lacerta I/Andromeda XXXI (Lac I/And XXXI) and Cassiopeia III/Andromeda XXXII (Cas III/And XXXII), in stacked Pan-STARRS1 rP1- and iP1-band imaging data. Both are luminous systems (MV ~ -12) located at projected distances of 20°.3 and 10°.5 from M31. Lac I and Cas III are likely satellites of the Andromeda galaxy with heliocentric distances of 756+44 -28 kpc and 772+61 -56 kpc, respectively, and corresponding M31-centric distances of 275 ± 7 kpc and 144+6 -4 kpc. The brightest of recent Local Group member discoveries, these two new dwarf galaxies owe their late discovery to their large sizes (rh = 4.2+0.4 -0.5 arcmin or 912+124 -93 pc for Lac I; rh = 6.5+1.2 -1.0 arcmin or 1456 ± 267 pc for Cas III) and consequently low surface brightness (μ0 ~ 26.0 mag arcsec-2), as well as to the lack of a systematic survey of regions at large radii from M31, close to the Galactic plane. This latter limitation is now alleviated by the 3π Pan-STARRS1 survey, which could lead to the discovery of other distant Andromeda satellite dwarf galaxies. [ABSTRACT FROM AUTHOR]

The activities of the Commission have continued to focus on controlling unwanted light and radio emissions at observatory sites, monitoring of conditions at observatory sites, and education and outreach. Commission members have been active in securing new legislation in several locations to further the protection of observatory sites as well as in the international regulation of the use of the radio spectrum and the protection of radio astronomical observations. [ABSTRACT FROM PUBLISHER]

The view of the night sky from most of the populated regions of Earth is now seriously compromised by light pollution. An entire generation of citizens is now growing up without ever having the opportunity to gaze upon the magnificent night sky from a dark location. Much of modern astronomy involves study of faint objects, often with brightnesses similar to or fainter than the night sky. Astronomers are therefore extremely vulnerable to increases in sky brightness from light pollution. Despite their remote locations, the dark night skies over the major optical observatories are increasingly threatened by growth of artificial light at night. [ABSTRACT FROM PUBLISHER]

The activities of the Commission have continued to focus on controlling unwanted light and radio emissions at observatory sites, monitoring of conditions at observatory sites, and education and outreach. Commission members have been active in securing new legislation in several locations to further the protection of observatory sites. [ABSTRACT FROM PUBLISHER]

We present the discovery of a new dwarf galaxy, Perseus I/Andromeda XXXIII, found in the vicinity of Andromeda (M31) in stacked imaging data from the Pan-STARRS1 3π survey. Located 27fdg9 away from M31, Perseus I has a heliocentric distance of 785 ± 65 kpc, compatible with it being a satellite of M31 at $374^{+14}_{-10}{\rm \,kpc}$ from its host. The properties of Perseus I are typical for a reasonably bright dwarf galaxy (MV = –10.3 ± 0.7), with an exponential half-light radius of rh = 1.7 ± 0.4 arcmin or $r_h = 400^{+105}_{-85}{\rm \,pc}$ at this distance, and a moderate ellipticity ($\epsilon = 0.43^{+0.15}_{-0.17}$). The late discovery of Perseus I is due to its fairly low surface brightness ($\mu _0=25.7^{+1.0}_{-0.9}$ mag arcsec–2), and to the previous lack of deep, high quality photometric data in this region. If confirmed to be a companion of M31, the location of Perseus I, far east from its host, could place interesting constraints on the bulk motion of the satellite system of M31., Astronomy

Division XII consists of Commissions that formerly were organized under the Executive Committee, that concern astronomers across a wide range of scientific sub-disciplines and provide interactions with scientists in a wider community, including governmental organizations, outside the IAU. [ABSTRACT FROM PUBLISHER]

We report the discovery of a wide (∼1400 AU projected separation), common proper motion companion to the nearby M dwarf LHS 2803 (PSO J207.0300-13.7422). This object was discovered during our census of the local T dwarf population using Pan-STARRS1 and Two Micron All Sky Survey data. Using the Infrared Telescope Facility/SpeX near-infrared spectroscopy, we classify the secondary to be spectral type T5.5. University of Hawaii 2.2 m/SuperNova Integral Field Spectrograph optical spectroscopy indicates that the primary has a spectral type of M4.5, with approximately solar metallicity and no measurable Hα emission. We use this lack of activity to set a lower age limit for the system of 3.5 Gyr. Using a comparison with chance alignments of brown dwarfs and nearby stars, we conclude that the two objects are unlikely to be a chance association. The primary's photometric distance of 21 pc and its proper motion implies thin disk kinematics. Based on these kinematics and its metallicity, we set an upper age limit for the system of 10 Gyr. Evolutionary model calculations suggest that the secondary has a mass of 72±47MJup, temperature of 1120 ± 80 K, and log g = 5.4 ± 0.1 dex. Model atmosphere fitting to the near-IR spectrum gives similar physical parameters of 1100 K and log g = 5.0. [ABSTRACT FROM AUTHOR]

Brief meetings were held to confirm the elections of the incoming Division President, Francoise Genova and Vice President, Ray Norris along with the Organizing Committee which will consist of the incoming Presidents of the 7 Commissions (5,6,14,41,46,50 and 55) plus additional nominated members. The incoming Organizing Committee will thus consist of: [ABSTRACT FROM PUBLISHER]

A response by Christian B. Luginbuhl, Constance E. Walker and Richard J. Wainscoat to a letter to the editor regarding their article "Lighting and Astronomy" in the December 2009 issue is presented.

Brief meetings were held to confirm the elections of the incoming Division President, Francoise Genova and Vice President, Ray Norris along with the Organizing Committee which will consist of the incoming Presidents of the 7 Commissions (5,6,14,41,46,50 and 55) plus additional nominated members. The incoming Organizing Committee will thus consist of: [ABSTRACT FROM PUBLISHER]