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Recent evidence of extremely metal-rich stars found in the Sombrero galaxy (M104) halo suggests that this galaxy has undergone a recent major merger with a relatively massive galaxy. In this paper, we present wide-field deep images of the M104 outskirts obtained with a 18-cm amateur telescope with the purpose of detecting any coherent tidal features from this possible major merger. Our new data, together with a model of the M104 inner halo and scattered light from stars around the field, allow us to trace for the first time the full path of the stream on both sides of the disc of the galaxy. We fully characterize the ring-like tidal structure and we confirm that this is the only observable coherent substructure in the inner halo region. This result is in agreement with the hypothesis that M104 was created by a wet major merger more than 3.5 Gyr ago that heated up the stellar population, blurring all old substructure. We generated a set of numerical models that reproduce the formation of the observed tidal structure. Our best-fitting model suggests the formation of this stream in the last 3 Gyr is independent of the wet major merger that created the M104 system. Therefore, the formation of the tidal stream can put a constraint on the time when the major merger occurred. © 2021 The Author(s)., DMD acknowledges financial support from the Talentia Senior Program (through the incentive ASE-136) from Secretaría General de Universidades, Investigación y Tecnología, de la Junta de Andalucía. DMD and JR acknowledge funding from the State Agency for Research of the Spanish MCIU through the Center of Excellence Severo Ochoa award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709). JR acknowledges support from the Spanish State Research Agency (AEI-MCINN) of the Spanish Ministry of Science and Innovation under the grant ‘The structure and evolution of galaxies and their central regions’ with reference PID2019-105602GB-I00/10.13039/501100011033 and financial support from the grants AYA2015-65973-C3-1-R and RTI2018-096228-B-C31 (MINECO/FEDER, UE). DMD also recognizes funds from the research project AYA 2007-65090. THELI made use of the following tools and data products: Source Extractor (Bertin & Arnouts 1996), Scamp (Bertin 2006), Swarp (Bertin et al. 2002), and the VizieR catalogue access tool, CDS, Strasbourg, France. Based on observations made with the William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group of Telescopes in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.

Previous work has shown that chronic nicotine administration causes adaptive changes in 5-HT

International audience; We have measured nonzero closure phases for about 29% of our sample of 56 nearby asymptotic giant branch (AGB) stars, using the three-telescope Infrared Optical Telescope Array (IOTA) interferometer at near-infrared wavelengths (H band) and with angular resolutions in the range 5-10 mas. These nonzero closure phases can only be generated by asymmetric brightness distributions of the target stars or their surroundings. We discuss how these results were obtained and how they might be interpreted in terms of structures on or near the target stars. We also report measured angular sizes and hypothesize that most Mira stars would show detectable asymmetry if observed with adequate angular resolution.

The UK Schmidt Telescope (UKST) of the Anglo-Australian Observatory completed a narrow-band H-alpha plus [NII] 6548, 6584A survey of the Southern Galactic Plane and Magellanic Clouds in late 2003. The survey, which was the last UKST wide-field photographic survey, and the only one undertaken in a narrow band, is now an on-line digital data product of the Wide-Field Astronomy Unit of the Royal Observatory Edinburgh (ROE). The survey utilised a high specification, monolithic H-alpha interference band-pass filter of exceptional quality. In conjunction with the fine grained Tech-Pan film as a detector it has produced a survey with a powerful combination of area coverage (4000 square degrees), resolution (~1 arcsecond) and sensitivity (

We have imaged the large-scale radio continuum structure in the Orion region with the Very Large Array at 330 MHz. Arcminute-resolution morphology of the extended emission in the H II regions M42 and M43 (NGC 1976 and NGC 1982) and in the NGC 1973-75-77 nebulosity to the north are presented. A low surface brightness thermal radio halo is detected in the H II region M42: comparison with an optical photograph indicates that the radio emission distinguishes optical emission structures from reflection nebulosities. In NGC 1977 we have discovered a compact, steep-spectrum radio source coincident with a bright optical rim.

Kodak Technical Pan (Tech Pan) emulsion on a film base has been in use at the UK Schmidt Telescope (UKST) since 1992. This material is extremely fine grained and its resolution is well matched to images produced by the UKST under good conditions. Tech Pan yields wide-angle photographs that are about 1 (stellar) magnitude fainter than equivalent IIIa-F plates but have considerably lower grain noise. A wide variety of new projects are under way which take advantage of this remarkable material. In this paper empirical results from experiments with Tech Pan from a number of sources are tied in with UKST experience to present an overview of the properties of the emulsion from an astronomical perspective. We compare Tech Pan's properties with those of equivalent IIIa-F emulsion, to which it seems superior in almost every respect. This overview and groundwork are currently missing from the published astronomical literature. The technical background and developments leading to adoption of this material at the UKST are presented.

We present the preliminary results of our 5-configuration, 20-pointing mosaic with the Australia Telescope Compact Array of the neutral hydrogen in the nearby spiral galaxy NGC 6744. The bulk of the HI resides in a ‘ring’ underlying the outer optical disk, with 2 HI spiral arms extending further out to almost 1·5 optical radii. The velocity field is fairly regular, apart from evidence for streaming motions along the HI arms, and the influence of the companion IB(s)m galaxy NGC 6744A. We associate a cloud of HI at a heliocentric velocity of 846 km s−1 with another companion object, ESO 104–g44. Our attempts to construct a mass model for NGC 6744 suffer from poor resolution in the inner disk, and the uncertainty in the total HI flux of NGC 6744. We anticipate that HIPASS observations will be crucial in resolving the latter issue.

The appearance of Tech Pan film in sizes that were useful in large Schmidt telescopes immediately offered new opportunities and advantages to users of Schmidt telescopes. Among the advantages were a spatial resolution that was well matched to the image quality produced by the optics of the telescope under the best conditions. For the first time such images were well sampled on Schmidt telescopes. Tech Pan was initially formulated by Eastman Kodak as a 35 mm solar patrol film designed to have enhanced sensitivity around the 656·2 nm Hα line. It is this feature, combined with the excellent imaging characteristics, that we seek to exploit with the new UK Schmidt Telescope (UKST) Hα survey. This paper briefly reports some preliminary comparative tests of Tech Pan with the new Hα filter at UKST and suggests ways in which data from the new survey can be quickly exploited using advanced photographic techniques such as photographic amplification. This simple contact copying process rapidly reveals extended low surface brightness features that simple inspection cannot.

In a new survey of nearby galaxies from stacked photographic images, M87 shows a diffuse fan of stellar material which extends along the projected SE (major) axis out to about 100 kpc at a limiting (B) surface brightness of $28 \hbox{mag arcsec}^{-2}$. We suggest that disruption of a small spheroidal galaxy within a larger potential is the most likely explanation for the diffuse structure. Our simulations include a rigid primary potential with characteristics similar to those derived for M87 and a populated intruder. The orbit is required to pass close to the center of the potential to produce a fan which nearly aligns with the major axis and has a large opening angle, as seen in M87. The structure of the dark matter at large galactic radii is investigated by representing M87 with different potentials. The morphology and luminosity of the fan and the kinematics of debris in the center of the primary potential are analyzed and compared with substructure in M87. The short lifetimes (t_fan < 5 10^8 years) of the simulated diffuse fans indicate that several accretion events could be hidden in galaxies.

The few elliptical galaxies with detected HI almost all seem to have optical peculiarities as well, though these are often well hidden and require special image enhancement techniques to reveal them. In this paper we show several deep images of ellipticals with optical shells which are associated with HI, and suggest that mergers, or at least encounters with gas-rich galaxies, are responsible. We also show some disk galaxies with unusual faint extensions, some of them the kinds of interactions that may result in HI in ellipticals. These illustrations are drawn from an atlas of low surface brightness images of bright galaxies currently in preparation.

Simple photographic techniques are used to enhance and combine many images of (mostly) bright galaxies made from plates in the archive of the UK Schmidt Telescope in Edinburgh. The purpose of this project is to reveal extended faint features of these objects that are less than 0.5 % as bright as the night sky. Presented here are the preliminary results of what we intend to be a substantial atlas. The early results suggest that a remarkably large number of apparently normal galaxies reveal unexpected features when very deep images are produced.

The Carina Nebula (NGC 3372) is one of the largest and brightest nebulae in the sky, and we see it from a distance of 7500 light-years. It extends for some 260 light-years across the southern Milky Way and is clearly visible to the unaided eye, but is less famous than the much smaller and closer Orion Nebula. In part this is because NGC 3372 is in the far southern sky, while the Orion Nebula is on the celestial equator, framed by a memorable collection of stars and visible from all parts of the globe.

This intriguing pair of interacting galaxies lies about 55 million light-years away in the direction of the constellation of Eridanus (The River). The larger galaxy is NGC 1532, and it is a dusty spiral system rather like the Milky Way, seen almost edge-on. It appears to be interacting with a smaller companion, NGC 1531. This latter is a largely gasless spiral. The interaction is mostly indicated by the anomalous burst of star formation in the nearest spiral arm in NGC 1532 and some curiously displaced emission nebulae that appear to be close to NGC 1531, which seems to be in the background. Less obvious here are large plumes and recently formed clusters of blue stars in the outer arms of NGC 1532. All these features are signatures of the immense tidal forces stirred up as galaxies collide.

In these pages, the reader can follow the engaging saga of astronomical exploration in the southern hemisphere, in a modern merger of aesthetics, science, and a story of human endeavor. This book is truly a celebration of southern skies. Jerry Bonnell, Editor - Astronomy Picture of the Day The southern sky became accessible to scientific scrutiny only a few centuries ago, after the first European explorers ventured south of the equator. Modern observing and imaging techniques have since revealed what seems like a new Universe, previously hidden below the horizon, a fresh astronomical bounty of beauty and knowledge uniquely different from the northern sky. The authors have crafted a book that brings this hidden Universe to all, regardless of location or latitude. Treasures of the Southern Sky celebrates the remarkable beauty and richness of the southern sky in words and with world-class imagery. In part, a photographic anthology of deep sky wonders south of the celestial equator, this book also celebrates the human story of southern astronomy with an engaging and detailed history of key contributors to southern sky exploration. The accompanying text provides the reader with intriguing facts and useful information about the featured objects. The volume is arranged by southern hemisphere season and brings to the printed page many of the most provocative and beautiful astronomical images of our time, many in print for the first time. The collection of imagery covers a full range of deep sky astronomical objects, including the familiar and iconic as well as those that are more obscure but no less intriguing. Masterful, state of the art professional and amateur astrophotography highlights the authors' carefully selected deep sky "treasures." DUST JACKET: The beauty and richness of the southern night sky is legendary. From southern latitudes the finest globular clusters in the sky are visible to the unaided eye, as are the nearest galaxies, the Magellanic Clouds. The brightest part of the Milky Way passes overhead during the southern winter and the nearest bright star as well as the legendary asterism known as the Southern Cross are both observable throughout the year. Despite these stunning highlights, the southern sky has received has received less attention than its northern counterparty, and fewer photographs exist of its lesser known, yet equally stunning and intriguing objects. This visual anthology features striking photographic portraits of the most celebrated to the more obscure southern astronomical objects. Carefully selected world-class images have been assembled using the latest digital methods, revealing these southern gems in ways never before seen. To provide a context, the pictures capture the sky in variety of scales, from the wide vistas seen through hobby telescopes to the tiny fields relayed in exquisitely rich detail by the powerful optics of the largest professional telescopes, including the Hubbel Space Telescope and ESO's telescopes. The beauty of the night sky is on display in vivid color and dazzling detail. The presentation is further enhanced by a detailed history of southern sky exploration and lucid text that describes the southern night-sky wonders in ways that are engaging and non-technical.

Reflected blue light from massive stars forms the shape of a horse’s head in the southern constellation of Scorpius, sometimes nicknamed the Blue Horsehead (IC 4592). It is seen here looking northwest, towards the lower right corner. The nebulosity is mostly faint, and covers about two square degrees of sky, about twice the area seen here, and a much greater area than the better-known Horsehead Nebula in Orion (p. 56). The smaller complex of blue and faint yellow reflection clouds in the upper left corner, in the horse’s neck, is known as IC 4601. Adjoining it near the left edge of the image is the faint red outline of the dark cloud Barnard 41, and this extends towards the center of the picture, joining with Barnard 40.

The Helix Nebula (NGC 7293) is the nearest planetary nebula to the Sun, at a distance of about 650 light-years. The remnant of a dying, Sun-sized star, the nebula is composed of a series of concentric, expanding, shell-like structures. They are the surface layers of the star, material ejected during different phases of the star’s death throes. The inner part of the nebula shows a series of cometary knots arranged like bicycle spokes, pointing away from the central hot star. Cometary knots are seen in other planetary nebulae, and they each are several times the size of our Solar System, much too big to be comets.

We present a new catalogue of faint southern galaxy clusters identified from examination of high-contrast film derivatives of a set of 55 prime focus AAT photographic plates taken in one or both of two pass-bands (J≡bⱼand F≡rF).⁠. Visual scans of these films have been compared with machine measurements of the original plates and the results demonstrate that the films offer ready access to the positions (but not photometry) of large numbers of faint objects to limiting magnitudes of bⱼ≃24.4±0.3 and rF≃22.9±0.2. Our cluster candidates are chosen according to their contrast, σc₁, above the fluctuations in the field counts as determined locally on the same film. A total of 112 candidate clusters are tabulated down to a contrast level of σc₁ = 2.0 (at which point marginal effects become apparent). Cross-correlations with published catalogues (and spectroscopic measurements) confirm that the bulk of these clusters are more distant than those found by Abell and co-workers. By applying our search criteria to simulated fields containing clusters of known richnesses, and with fluctuations in the field counts matching those seen in the data, we determine our cluster list should be complete above a limit σc₁ = 3.25. Given recent estimates of the volume density of clusters of various richnesses, our simulations predict the observed number of F clusters seen above the σc₁ = 3.25 limit, but predict too few J clusters. To test for the origin of this excess of blue clusters we have measured redshifts for 95 faint galaxies in 29 of the 44 clusters with σc₁>4.0 using a variety of telescopes and instruments. A spectroscopically complete subsample in 16 fields allows us to determine the absolute space density. The spectroscopy confirms the reality of the clusters with σc₁>4.0 and shows a redshift range for the F sample similar to that expected without luminosity or cluster evolution; the J sample extends to higher redshifts than expected. A detailed study of the highest redshift clusters suggests the abundance of high-redshift J clusters arises either from projections from foreground spiral-rich groups or via recent star formation within the distant cluster environments. In support of the latter hypothesis, we demonstrate how bursts of star formation in a subset of cluster galaxies would transform the J contrast leaving the F contrast largely unaffected – in agreement with the basic trend observed. We discuss the implications of our results for further searches for high-z clusters. Only with the advent of wide-field infrared imaging, or X-ray selected samples, might galaxy-dependent selection effects associated with variations in stellar populations at a given epoch be overcome.

An overview is presented of a number of astrometry and astrophysics programs based on radio sources from the Parkes 2.7 GHz catalogues. The programs cover the optical identification and spectroscopy of flat-spectrum Parkes sources and the determination of their milliarc-second radio structures and positions. Work is also in progress to tie together the radio and Hipparcos positional reference frames. A parallel program of radio and optical astrometry of southern radio stars is also under way.

New observations, including both narrow-band imaging and long-slit spectroscopy, of the optical filaments in Centaurus A are presented. The line-emitting filaments which compose part of the well-known optical-jet are complex and highly structured at the limit of ground-based resolution. Variations in the surface brightness, line intensity ratios and the velocity field occur on spatial scales ∼ 100 pc. No evidence of [O III] λ5007 emission associated with either the inner jet or a possible counter jet are found. The emission line spectra of the filaments are very similar in character to those of the spatially extended nebulosities in more distant radio galaxies and radio quasars.

Les echos de lumiere entourant la supernova 1987A ont ete photographies au foyer principal du Telescope Anglo-Australien 3.9 m. La nebulosite brillante et un grand nombre d'etoiles faibles dans le champ ont ete extraits des images par soustraction photographique. L'image resultante revele que les 2 arcs connus anterieurement sont des cercles complets. L'anneau interieur est trouve concentrique autour de la supernova et l'anneau exterieur est trouve excentrique. Les implications de ce resultat sont discutees.

We present a list of bright (< 17 mag) southern QSOs and bright (< 11 mag) stars that may be suitable for theHubble Space Telescopelink between theHipparcosastrometric reference frame and the VLBI extragalactic frame. The QSOs have been selected from various lists of radio objects and identifications. The stars have been selected from the Strasbourg (CDS) data base and from the Preliminary Second Cape Photographic Catalogue, and supplemented with stars measured from the SERC IIIa-J Schmidt survey. The list of QSOs and stars have been included in theHipparcosandHSTschedule of observations.

Since its invention, photography has been recognized as both an art and a science, linked by the technology through which its images are captured and then preserved. It is natural that aspects of these three components, in varying degrees, would be evident in photographic images. The extent to which art, science, or technology dominates the photographic expression is in the hands and the imaginative eye and mind of the practitioner. The importance of the motives in photography is as relevant in the digital age as it was for Daguerre and Fox Talbot, both of whom made some of the first photographs of scientific subjects.

Among the first ways of studying extraterrestrial cosmic rays was to fly blocks or sheets of photographic emulsions at high altitudes in balloons or aircraft. The highly penetrating cosmic rays interact with the atomic nuclei of the emulsions producing protons, electrons, and mesons. In the emulsion they leave latent image tracks that can be made visible by development. Tracks from nuclear particles can also be rendered visible in a Wilson cloud chamber or a liquid-hydrogen bubble chamber or spark chamber, often attached to a particle accelerator such as cyclotrons and synchrotrons. These chambers were once commonly used as detectors associated with so-called “atom smashers.”

Time-lapse photography is the use of photography to compress elapsed time in a still or moving image. In motion media, the playback time will be shorter than the recording time. Timelapse photography allows processes or phenomena that take place over a period of time to be evaluated at a more convenient pace or in a manner where the subtle changes that occur during the event are more easily observed.

In many branches of science, an image can be the primary source of data and the results of an experiment. The integrity of the imaging data may thus be central to a new result or discovery. However, it must also be recognized that no image is totally objective. The making of a picture for science requires an imaging opportunity, the selection of imaging tools, the processing of the data, and the analysis or interpretation of the resultant picture itself. The imaging scientist must choose the moment, the method, the medium, and much else when making an image. At each phase of the input process, subjective choices are inevitable. For this reason, accurate recordkeeping and the preservation of records and original materials has always been an important part of scientific photography.

Taking pictures at night may be considered to be both more limited and more challenging than daytime photography because there is relatively less light available. However, nighttime and twilight photography provides many opportunities for unusual, creative, and scientifically interesting imaging. The technical challenges that the night photographer faces are numerous. Night time photography requires the measuring of exposures at low light levels, managing very long exposure times, and sometimes the inclusion of the light source(s) itself in the image, as well as the mixed lighting and the changing lighting levels during an exposure. It is also useful to have some prior knowledge of how the light and color will change in the twilight and the brightness of moonlight. Sometimes additional extra equipment is required, but often nothing more than a cable release, tripod, and electronic flash or flashlight are necessary

The word “false” in this application means unreal or artificial; it does not necessarily mean fraudulent. False-color images can be made in many ways but in general they are the combined display of two or three monochrome images (information channels) taken of the same subject at diff erent wavelengths or showing variations of some kind. These images may be made in radiation that we cannot see (UV or IR), or cannot photograph in any conventional way (acoustic, gamma ray, radio etc.).

Scientific photography may be described as many things by diff erent people and consequently this section has tried to tease out the many threads that make up its rich tapestry.

Interactions between galaxies are common and are an important factor in determining their physical properties such as position along the Hubble sequence and star-formation rate. There are many possible galaxy interaction mechanisms, including merging, ram-pressure stripping, gas compression, gravitational interaction and cluster tides. The relative importance of these mechanisms is often not clear, as their strength depends on poorly known parameters such as the density, extent and nature of the massive dark halos that surround galaxies. A nearby example of a galaxy interaction where the mechanism is controversial is that between our own Galaxy and two of its neighbours -- the Large and Small Magellanic Clouds. Here we present the first results of a new HI survey which provides a spectacular view of this interaction. In addition to the previously known Magellanic Stream, which trails 100 degrees behind the Clouds, the new data reveal a counter-stream which lies in the opposite direction and leads the motion of the Clouds. This result supports the gravitational model in which leading and trailing streams are tidally torn from the body of the Magellanic Clouds.

We have placed limits on the cosmological significance of gas-rich low surface-brightness (LSB) galaxies as a proportion of the total population of gas-rich galaxies by carrying out a very deep survey (HIDEEP) for neutral hydrogen (HI) with the Parkes multibeam system. Such a survey avoids the surface-brightness selection effects that limit the usefulness of optical surveys for finding LSB galaxies. To complement the HIDEEP survey we have digitally stacked eight 1-hour R-band Tech Pan films from the UK Schmidt Telescope covering 36 square degrees of the survey area to reach a very deep isophotal limit of 26.5 R mag/sq. arcsec. At this level, we find that all of the 129 HI sources within this area have optical counterparts and that 107 of them can be identified with individual galaxies. We have used the properties of the galaxies identified as the optical counterparts of the HI sources to estimate the significance of LSB galaxies (defined to be those at least 1.5 magnitudes dimmer in effective surface-brightness than the peak in the observed distribution seen in optical surveys). We calculate the contribution of LSB galaxies to the total number, neutral hydrogen density, luminosity density, baryonic mass density, dynamical mass density and cross-sectional area of gas-rich galaxies. We do not find any `Crouching Giant' LSB galaxies such as Malin 1, nor do we find a population of extremely low surface-brightness galaxies not previously found by optical surveys. Such objects must either be rare, gas-poor or outside the survey detection limits., 13 pages, 14 figures. Accepted for publication in MNRAS