scholarly journals III. Local Galactic Structure

1985 ◽  
Vol 19 (1) ◽  
pp. 407-409
Keyword(s):  
Milky Way ◽  
Gamma Ray ◽  
Galactic Structure ◽  
Solar Neighbourhood ◽  
The Sun ◽  
X Ray ◽  
The Galaxy

This section contains work dealing with the Milky Way characteristics in the solar neighbourhood and supported by observations with wavelengths shorter than 1 mm. Thus, results are collected from gamma-ray, X-ray, UV, optical and IR observations in the different subsections. These are (1) the volume closest to the sun, (2) more distant objects at low galactic latitudes, and (3) objects at high galactic latitudes. Overall properties of the Galaxy and evolutionary effects are presented in Section IV.

scholarly journals Multiwavelength Milky Way: An Educational Poster

1998 ◽  
Vol 179 ◽  
pp. 237-237 ◽  
Author(s):  
D. Leisawitz ◽  
S.W. Digel ◽  
S. Geitz
Keyword(s):  
Milky Way ◽  
Gamma Ray ◽  
Line Emission ◽  
Electromagnetic Spectrum ◽  
Data Sets ◽  
X Ray ◽  
Nasa Goddard Space ◽  
Broadband Emission ◽  
The Galaxy ◽  
Effective Use

The Astrophysics Data Facility at NASA Goddard Space Flight Center supports the processing, management, and dissemination of data obtained by past, current, and future NASA and international astrophysics missions, and promotes the effective use of those data by the astrophysics community, educators, and the public. Our Multiwavelength Milky Way poster was printed for broad distribution. It depicts the Galaxy at radio, infrared, optical, X-ray, and gamma-ray wavelengths. In particular, the poster contains images of the Galactic 21-cm and CO (J = 1 → 0) line emission, and IRAS 12, 60, and 100 μm, COBE/DIRBE 1.25, 2.2, and 3.5 μm, Digitized Sky Survey optical wavelength, ROSAT/PSPC 0.25, 0.75, and 1.5 keV X-ray, and CGRO/EGRET E > 100 MeV gamma ray broadband emission. All of the data sets are publicly available. Captions describe the Milky Way and what can be learned about the Galaxy from measurements made in each segment of the electromagnetic spectrum. The poster is intended to be an educational tool, one that will stimulate heightened awareness by laypersons of NASA's contribution to modern astronomy.Through an interface available on the World Wide Web at http://adf.gsfc.nasa.gov/adf/adf.html one may view the images that appear on the poster, read the poster captions, and locate the archived data and references.

scholarly journals LIGHT SUPERCONDUCTING STRINGS IN THE GALAXY

2007 ◽  
Vol 16 (12b) ◽  
pp. 2399-2405 ◽  
Author(s):  
FRANCESC FERRER ◽  
TANMAY VACHASPATI
Keyword(s):  
Magnetic Field ◽  
Spatial Distribution ◽  
Particle Physics ◽  
Milky Way ◽  
Gamma Ray ◽  
Galactic Center ◽  
Line Emission ◽  
Galactic Magnetic Field ◽  
The Galaxy ◽  
Intense Source

Observations of the Milky Way by the SPI/INTEGRAL satellite have confirmed the presence of a strong 511 keV gamma ray line emission from the bulge, which requires an intense source of positrons in the galactic center. These observations are hard to account for by conventional astrophysical scenarios, whereas other proposals, such as light DM, face stringent constraints from the diffuse gamma ray background. Here we suggest that light superconducting strings could be the source of the observed 511 keV emission. The associated particle physics, at the ~ 1 TeV scale, is within the reach of planned accelerator experiments, while the distinguishing spatial distribution, proportional to the galactic magnetic field, could be mapped by SPI or by future, more sensitive satellite missions.

Influence of supernovae, gamma-ray bursts, solar flares, and cosmic rays on the terrestrial environment

2008 ◽  
Author(s):  
Arnon Dar
Keyword(s):  
Solar Activity ◽  
Cosmic Rays ◽  
Gamma Ray ◽  
Cosmic Ray ◽  
Gamma Ray Bursts ◽  
The Sun ◽  
Terrestrial Environment ◽  
The Earth ◽  
The Galaxy ◽  
Threat To Life

Changes in the solar neighbourhood due to the motion of the sun in the Galaxy, solar evolution, and Galactic stellar evolution influence the terrestrial environment and expose life on the Earth to cosmic hazards. Such cosmic hazards include impact of near-Earth objects (NEOs), global climatic changes due to variations in solar activity and exposure of the Earth to very large fluxes of radiations and cosmic rays from Galactic supernova (SN) explosions and gamma-ray bursts (GRBs). Such cosmic hazards are of low probability, but their influence on the terrestrial environment and their catastrophic consequences, as evident from geological records, justify their detailed study, and the development of rational strategies, which may minimize their threat to life and to the survival of the human race on this planet. In this chapter I shall concentrate on threats to life from increased levels of radiation and cosmic ray (CR) flux that reach the atmosphere as a result of (1) changes in solar luminosity, (2) changes in the solar environment owing to the motion of the sun around the Galactic centre and in particular, owing to its passage through the spiral arms of the Galaxy, (3) the oscillatory displacement of the solar system perpendicular to the Galactic plane, (4) solar activity, (5) Galactic SN explosions, (6) GRBs, and (7) cosmic ray bursts (CRBs). The credibility of various cosmic threats will be tested by examining whether such events could have caused some of the major mass extinctions that took place on planet Earth and were documented relatively well in the geological records of the past 500 million years (Myr). A credible claim of a global threat to life from a change in global irradiation must first demonstrate that the anticipated change is larger than the periodical changes in irradiation caused by the motions of the Earth, to which terrestrial life has adjusted itself. Most of the energy of the sun is radiated in the visible range. The atmosphere is highly transparent to this visible light but is very opaque to almost all other bands of the electromagnetic spectrum except radio waves, whose production by the sun is rather small.

scholarly journals An unusual transient following the short GRB 071227

2019 ◽  
Vol 489 (1) ◽  
pp. 13-27
Author(s):  
R A J Eyles ◽  
P T O’Brien ◽  
K Wiersema ◽  
R L C Starling ◽  
B P Gompertz ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Thermal Emission ◽  
Chemical Properties ◽  
Major Axis ◽  
Optical Observations ◽  
X Ray ◽  
Very Large Telescope ◽  
The Galaxy ◽  
Simple Extrapolation ◽  
Emission Models

ABSTRACT We present X-ray and optical observations of the short duration gamma-ray burst GRB 071227 and its host at z = 0.381, obtained using Swift, Gemini South, and the Very Large Telescope. We identify a short-lived and moderately bright optical transient, with flux significantly in excess of that expected from a simple extrapolation of the X-ray spectrum at 0.2–0.3 d after burst. We fit the SED with afterglow models allowing for high extinction and thermal emission models that approximate a kilonova to assess the excess’ origins. While some kilonova contribution is plausible, it is not favoured due to the low temperature and high luminosity required, implying superluminal expansion and a large ejecta mass of ∼0.1 M$\odot$. We find, instead, that the transient is broadly consistent with power-law spectra with additional dust extinction of E(B − V) ∼ 0.4 mag, although a possibly thermal excess remains in the z band. We investigate the host, a spiral galaxy with an edge-on orientation, resolving its spectrum along its major axis to construct the galaxy rotation curve and analyse the star formation and chemical properties. The integrated host emission shows evidence for high extinction, consistent with the afterglow findings. The metallicity and extinction are consistent with previous studies of this host and indicate the galaxy is a typical, but dusty, late-type SGRB host.

scholarly journals High-Resolution B-Photometry of the Milky Way and Results on Galactic Structure

1990 ◽  
Vol 139 ◽  
pp. 205-206
Author(s):  
S. Kimeswenger ◽  
W. Schlosser ◽  
K. J. Seidensticker ◽  
B. Hoffmann ◽  
Th. Schmidt-Kaler
Keyword(s):  
High Resolution ◽  
Milky Way ◽  
Galactic Structure ◽  
Surface Photometry ◽  
High Resolution Data ◽  
V Band ◽  
The Galaxy ◽  
Global Parameters ◽  
Pioneer 10 ◽  
Resolution Data

During the last two decades, many attempts were made to determine the global parameters of the Galaxy and to compare the Galaxy to other galaxies (Schmidt-Kaler and Schlosser 1973; de Vaucouleurs and Pence 1978; Gilmore 1984; van der Kruit 1986). While most of these investigations are based on star counts, a detailed overall study by surface photometry, because of the lack of homogeneous high-resolution data, is rare. The last attempt by van der Kruit (1986), based on Pioneer 10 data, suffered from low resolution. The great number of individual structures at low and even intermediate latitudes could not be recognized. Our work (B-band, Hoffmann et al. 1989, this volume; V-band, Schlosser, Schmidt-Kaler, and Schneider 1989; U-Band and R-band photometry, in preparation) provides this homogeneous high-resolution data.

INTEGRAL results on the electron-positron annihilation radiation and X-ray & Gamma-ray diffuse emission of the Milky Way

2020 ◽  
Vol 90 ◽  
pp. 101548 ◽  
Author(s):  
Eugene Churazov ◽  
Laurent Bouchet ◽  
Pierre Jean ◽  
Elisabeth Jourdain ◽  
Jürgen Knödlseder ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Milky Way ◽  
Gamma Ray ◽  
Annihilation Radiation ◽  
Diffuse Emission ◽  
X Ray ◽  
Electron Positron Annihilation ◽  
Electron Positron

scholarly journals B. Models of the Galaxy

1985 ◽  
Vol 19 (1) ◽  
pp. 423-425
Keyword(s):  
Observational Data ◽  
Rotational Velocity ◽  
Galactic Structure ◽  
The Sun ◽  
Circular Velocity ◽  
The Galaxy

Reviews of implications of the recent observational data concerning the galactic structure were given by Bok (33.013.022) and Blitz et al. (33.155.115).The recent data of the rotational velocity in the Galaxy were discussed by Blitz (33.155.023) and Knapp (33.155.053). A method to derive the circular velocity at the sun was proposed by Lynden-Bell and Frenk (30.155.053).

scholarly journals Predicción probabilística de la existencia de estrellas Cefeidas en la galaxia

2019 ◽  
Vol 65 (1) ◽  
pp. 34
Author(s):  
A. Cabañas Hernández ◽  
D. L. Cárdenas ◽  
E. E. Damián de la Cruz ◽  
A. Fortiz Flores ◽  
L. E. Garduño Puga ◽  
...  
Keyword(s):  
Probability Density Function ◽  
Probability Density ◽  
Milky Way ◽  
Solar Neighborhood ◽  
The Sun ◽  
Concentration Zone ◽  
High Concentration ◽  
Normal Probability ◽  
The Galaxy ◽  
Probabilistic Study

Las estrellas Cefeidas han sido de gran relevancia para la determinación de distancias tanto en la Galaxia como a escala cosmológica. Debido a que, hasta el momento, la mayor parte de las Cefeidas cercanas observadas se encuentran en la vecindad solar, se juzga pertinente un estudio probabilístico sobre su distribución, no solo en la vecindad solar sino también en toda la Vía Láctea, pues deben estar jugando un papel importante para mantener la estructura de nuestra Galaxia. Partiendo de 187 Cefeidas observadas en la Vía Láctea, se presenta una función de densidad de probabilidad normal que sirvió para elaborar un modelo en tres dimensiones que permite encontrar la zona de más alta concentración de Cefeidas y de paso, con ella, predecir la existencia de Cefeidas en zonas ceranas a toda la Galaxia. Asmismo, se da a conocer una segunda distribución de probabilidad, normal también, pero en la vecindad del eje galáctico, a fin de elaborar otro modelo que permita predecir la existencia de estrellas Cefeidas dentro de la Vía Láctea y en la vecindad del sol.ABSTRACTThe Cepheid stars have been very relevant for the determination ofdistances both in the Galaxy and also at cosmological scale. Because, so far, most of the nearby observed Cepheids are in the solar neighborhood, a probabilistic study about their distribution in the solar neighborhood and in the whole Milky Way is pertinent, since they must be playing an important role for keeping the structure of our Galaxy. Starting from the in the Milky Way already 187 observed Cepheids, a normal probability density function for their distribution in the Galaxy is presented, which is used to carry out a model which allows to find the high concentration zone of Cepheids and, in turn, with it, to predict the existence of Cepheids in the neighborhood of the Galaxy. A second model has been done, in order to prognosticate the existence of Cepheids within the milky way and in the neigborhood of the sun.

scholarly journals On the density within the dark-matter core in our galaxy

2007 ◽  
pp. 19-23 ◽  
Author(s):  
S. Ninkovic
Keyword(s):  
Dark Matter ◽  
Rotation Curve ◽  
Milky Way ◽  
Solar Neighbourhood ◽  
Constant Density ◽  
The Sun ◽  
Exponential Law ◽  
Circular Velocity ◽  
Flat Rotation Curve

Assuming that the disc of our Galaxy, the Milky Way, obeys the classical exponential law, that it is maximal and the Sun is rather far from the maximum of its circular velocity, one finds that, most likely, the galactic corona (subsystem containing the dark matter) has a nearly constant density within its core which contains the position of the Sun. The approach applied in the present paper is local, i.e. quantities characterizing the solar neighbourhood are treated. The assumptions and the result could explain why the ratio of the moduli of the Oort constants is expected to exceed the value of 1.0 which corresponds to the locally flat rotation curve of the Milky Way.

Hard X-ray and gamma-ray flares on the Sun: Stereoscopic effects near the limb from observations on the 2001 Mars Odyssey spacecraft and near-Earth spacecraft

2005 ◽  
Vol 49 (11) ◽  
pp. 916-931 ◽  
Author(s):  
M. A. Livshits ◽  
V. A. Chernetskii ◽  
I. G. Mitrofanov ◽  
A. S. Kozyrev ◽  
M. L. Litvak ◽  
...  
Keyword(s):  
Gamma Ray ◽  
The Sun ◽  
X Ray ◽  
Mars Odyssey
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