A discussion on infared astronomy - A far infrared sky survey

1969 ◽  
Vol 264 (1150) ◽  
pp. 267-271 ◽  
Keyword(s):  
Milky Way ◽  
Angular Resolution ◽  
Thermal Emission ◽  
Far Infrared ◽  
The Moon ◽  
Sky Survey ◽  
Upper Limits ◽  
Celestial Sphere ◽  
Thick Source ◽  
Thin Source

A balloon-borne instrument for making far infrared sky surveys with 2° angular resolution is described. In two initial flights at a wavelength of 320 μm approximately half of the celestial sphere including most of the northern milky way was surveyed. The thermal emission of the moon was alone detected. The upper limit to the flux from other sources was 3 x 10-12 W cm-2 in the 300 to 360 μm band, or approximately 2 x 10-23 W cm-2 Hz-1. A blackbody (optically thick) source 2° or greater in diameter yielding this flux would have a temperature of 10 °K. A warmer, small or optically thin source providing this much radiation in the Rayleigh-Jeans tail of the Plank distribution would have a temperature averaged over the 2° beam of 0.6 °K. These observations can be used to set upper limits to the opacity and temperature of interstellar grains.

scholarly journals Interplanetary Scintillation with the Murchison Widefield Array V: An all-sky survey of compact sources using a modern low-frequency radio telescope

2019 ◽  
Vol 36 ◽  
Author(s):  
J. S. Morgan ◽  
J.-P. Macquart ◽  
R. Chhetri ◽  
R. D. Ekers ◽  
S. J. Tingay ◽  
...  
Keyword(s):  
Angular Resolution ◽  
Low Frequency ◽  
Radio Sources ◽  
Interplanetary Scintillation ◽  
Complementary Information ◽  
Imaging Arrays ◽  
Sky Survey ◽  
Murchison Widefield Array ◽  
Celestial Sphere ◽  
Compact Sources

AbstractWe describe the parameters of a low-frequency all-sky survey of compact radio sources using Interplanetary Scintillation, undertaken with the Murchison Widefield Array. While this survey gives important complementary information to low-resolution survey, providing information on the sub-arsecond structure of every source, a survey of this kind has not been attempted in the era of low-frequency imaging arrays such as the Murchison Widefield Array and LOw Frequency Array. Here we set out the capabilities of such a survey, describing the limitations imposed by the heliocentric observing geometry and by the instrument itself. We demonstrate the potential for Interplanetary Scintillation measurements at any point on the celestial sphere and we show that at 160 MHz, reasonable results can be obtained within 30° of the ecliptic (2π str: half the sky). We also suggest some observational strategies and describe the first such survey, the Murchison Widefield Array Phase I Interplanetary Scintillation survey. Finally we analyse the potential of the recently upgraded Murchison Widefield Array and discuss the potential of the Square Kilometre Array-low to use Interplanetary Scintillation to probe sub-mJy flux density levels at sub-arcsecond angular resolution.

scholarly journals A Search in the Infrared to Microwave for Astroengineering Activity

1985 ◽  
Vol 112 ◽  
pp. 315-319
Author(s):  
V. I. Slysh
Keyword(s):  
Power Plants ◽  
Thermal Emission ◽  
Far Infrared ◽  
Circumstellar Dust ◽  
Microwave Background ◽  
Giant Stars ◽  
Sky Survey ◽  
Red Giant ◽  
Many Sources ◽  
Microwave Sources

Huge space power plants (Dyson Spheres) utilizing most of a star's energy should be detectable as infrared or microwave sources. A recent far infrared all-sky survey has revealed many sources with a spectrum peaking on this region which is characteristic of the thermal emission of the hypothetical Dyson spheres. The possibility of confusing them with thick circumstellar dust shells around evolved red giant stars is discussed. Microwave detection of cool extended Dyson Spheres by all-sky surveys searching for microwave background fluctuations is also considered.

scholarly journals The Radio-FIR Correlation in the Milky Way

2010 ◽  
Vol 27 (3) ◽  
pp. 340-346 ◽  
Author(s):  
J. Zhang ◽  
A. Hopkins ◽  
P. J. Barnes ◽  
M. Cagnes ◽  
Y. Yonekura ◽  
...  
Keyword(s):  
Star Formation ◽  
Milky Way ◽  
Thermal Emission ◽  
Flux Ratio ◽  
Far Infrared ◽  
Large Magellanic Cloud ◽  
Galactic Latitude ◽  
Radio Flux ◽  
Star Forming ◽  
Star Forming Regions

AbstractWe investigate the scale on which the correlation arises between the 843 MHz radio and the 60 μm far-infrared (FIR) emission from star forming regions in the Milky way. The correlation, which exists on the smallest scales investigated (down to ≈ 4 pc), becomes noticeably tight on fields of size 30′, corresponding to physical scales of ≈ 20–50 pc. The FIR to radio flux ratio on this scale is consi stent with the radio emission being dominated by thermal emission. We also investigate the location dependence of qmean, a parameter measuring the mean FIR to radio flux ratio, of a sample of star forming regions. We show that qmean displays a modest dependence on galactic latitude. If this is interpreted as a dependence on the intensity of star formation activity, the result is consistent with studies of the Large Magellanic Cloud (LMC) and other near by galaxies that show elevated values for q in regions of enhanced star formation.

scholarly journals CONSTRAINTS ON THE SHAPE OF THE MILKY WAY DARK MATTER HALO FROM JEANS EQUATIONS APPLIED TO SLOAN DIGITAL SKY SURVEY DATA

2012 ◽  
Vol 758 (1) ◽  
pp. L23 ◽  
Author(s):  
Sarah R. Loebman ◽  
Željko Ivezić ◽  
Thomas R. Quinn ◽  
Fabio Governato ◽  
Alyson M. Brooks ◽  
...  
Keyword(s):  
Dark Matter ◽  
Survey Data ◽  
Milky Way ◽  
Sloan Digital Sky Survey ◽  
Dark Matter Halo ◽  
Sky Survey

Calibration and Validation of Infrared Sounders with Moon and Mercury

2021 ◽  
Author(s):  
Martin Burgdorf ◽  
Stefan A. Buehler ◽  
Viju John ◽  
Thomas Müller ◽  
Marc Prange
Keyword(s):  
Large Time ◽  
Angular Resolution ◽  
The Moon ◽  
Photometric Calibration ◽  
The Earth ◽  
Spread Function ◽  
Spectral Channels ◽  
Better Than ◽  
Full Disk

<p>Serendipitous observations of airless bodies of the inner solar system provide a unique means to the calibration of instruments on meteorological research satellites, because the physical properties of their surfaces change very little, even on large time scales. We investigated how certain instrumental effects can be characterised with observations of the Moon and Mercury. For this we identified and analysed intrusions of the Moon in the deep space views of HIRS/2, /3, and /4 (High-resolution Infrared Sounder) on various satellites in polar orbits and as well some images obtained with SEVIRI (Spinning Enhanced Visible Infra-Red Imager) on MSG-3 and -4 (Meteosat Second Generation), which had Mercury standing close to the Earth in the rectangular field of view.</p><p>A full-disk, infrared Moon model was developed that describes how the lunar flux density depends on phase angle and wavelength. It is particularly helpful for inter-calibration, checks of the photometric consistency of the sounding channels, and the calculation of an upper limit on the non-linearity of the shortwave channels of HIRS. In addition, we used the Moon to determine the co-registration of the different spectral channels.</p><p>Studies of the channel alignment are also presented for SEVIRI, an infrared sounder with an angular resolution about a hundred times better than HIRS. As we wanted to check the image quality of this instrument with a quasi-point source as well, we replaced here the Moon with Mercury. We found the typical smearing of the point spread function in the scan direction and occasionally a nearby ghost image, which is three to four times fainter than the main image of the planet. Both effects cause additional uncertainties of the photometric calibration.  </p>

scholarly journals Quantifying tidal stream disruption in a simulated Milky Way

2017 ◽  
Vol 470 (1) ◽  
pp. 522-538 ◽  
Author(s):  
Emily Sandford ◽  
Andreas H. W. Küpper ◽  
Kathryn V. Johnston ◽  
Jürg Diemand
Keyword(s):  
Dark Matter ◽  
Milky Way ◽  
Galactic Halo ◽  
Mass Range ◽  
Galactic Centre ◽  
High Dimensions ◽  
Density Profiles ◽  
Upper Limits ◽  
Tidal Stream ◽  
Tidal Streams

Abstract Simulations of tidal streams show that close encounters with dark matter subhaloes induce density gaps and distortions in on-sky path along the streams. Accordingly, observing disrupted streams in the Galactic halo would substantiate the hypothesis that dark matter substructure exists there, while in contrast, observing collimated streams with smoothly varying density profiles would place strong upper limits on the number density and mass spectrum of subhaloes. Here, we examine several measures of stellar stream ‘disruption' and their power to distinguish between halo potentials with and without substructure and with different global shapes. We create and evolve a population of 1280 streams on a range of orbits in the Via Lactea II simulation of a Milky Way-like halo, replete with a full mass range of Λcold dark matter subhaloes, and compare it to two control stream populations evolved in smooth spherical and smooth triaxial potentials, respectively. We find that the number of gaps observed in a stellar stream is a poor indicator of the halo potential, but that (i) the thinness of the stream on-sky, (ii) the symmetry of the leading and trailing tails and (iii) the deviation of the tails from a low-order polynomial path on-sky (‘path regularity') distinguish between the three potentials more effectively. We furthermore find that globular cluster streams on low-eccentricity orbits far from the galactic centre (apocentric radius ∼30–80 kpc) are most powerful in distinguishing between the three potentials. If they exist, such streams will shortly be discoverable and mapped in high dimensions with near-future photometric and spectroscopic surveys.

scholarly journals The Milky Way Revealed by Variable Stars. I. Sample Selection of RR Lyrae Stars and Evidence for Merger History

2022 ◽  
Vol 258 (1) ◽  
pp. 20
Author(s):  
Iminhaji Ablimit ◽  
Gang Zhao ◽  
Uy. Teklimakan ◽  
Jian-Rong Shi ◽  
Kunduz Abdusalam
Keyword(s):  
Milky Way ◽  
Sample Selection ◽  
Variable Stars ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Sky Survey ◽  
Spectroscopic Information ◽  
History Of ◽  
Dual Origin ◽  
Lyrae Stars

Abstract In order to study the Milky Way, RR Lyrae (RRL) variable stars identified by Gaia, ASAS-SN, and ZTF sky survey projects have been analyzed as tracers in this work. Photometric and spectroscopic information of 3417 RRLs including proper motions, radial velocity, and metallcity are obtained from observational data of Gaia, LAMOST, GALAH, APOGEE, and RAVE. Precise distances of RRLs with typical uncertainties less than 3% are derived by using a recent comprehensive period–luminosity–metallicity relation. Our results from kinematical and chemical analysis provide important clues for the assembly history of the Milky Way, especially for the Gaia–Sausage ancient merger. The kinematical and chemical trends found in this work are consistent with those of recent simulations that indicated that the Gaia–Sausage merger had a dual origin in the Galactic thick disk and halo. As recent similar works have found, the halo RRL sample in this work contains a subset of radially biased orbits besides a more isotropic component. This higher orbital anisotropy component amounts to β ≃ 0.8, and it contributes between 42% and 83% of the halo RRLs at 4 < R( kpc) < 20.

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