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1

ISO proves that intergalactic space is dusty  

NASA Astrophysics Data System (ADS)

In the past, astronomers have considered intergalactic space to be extremely clean. Except in the vast concentrations of stars, gas and dust that make up the galaxies themselves, the Universe was supposed to be filled only by very thin traces of invisible gas. ISO's detection of dust means that the Universe is less transparent than astronomers have assumed. Their cosmic window-pane is slightly dirty and large-scale inferences based on the brightnesses of distant galaxies and quasars may be affected. Emissions from the intergalactic dust were picked up by the photometer ISOPHOT. A team of German, British, Spanish and Danish astronomers contributed this versatile set of detectors to ISO. The leader of the ISOPHOT team is Dietrich Lemke of the Max-Planck Institut fr Astronomie (MPIA) in Heidelberg, Germany. "ISOPHOT in ISO is the only instrument in existence capable of making this detection" Lemke says. "The intergalactic dust is so cold that we need a very cold telescope to detect it. The strongest emissions from the dust are at a wavelength of 0.1-0.2 millimetre, which cannot be well observed from the Earth. ISO provides telescope in space cooled by superfluid helium to within 2 degrees of absolute zero. ISOPHOT is the instrument on ISO that measures infrared intensities at the longest wavelengths, up to 0.2 millimetre." ISOPHOT's advantages made finding the intergalactic dust possible, but not easy. The observations pushed instrumental sensitivity to the limit, and emissions from cold dust clouds in the Milky Way Galaxy confused the picture. The signal of intergalactic dust emerged clearly only after extensive data analysis. Cold dust in a hot cluster Our home Galaxy, the Milky Way, belongs to a very small group of galaxies. Intergalactic dust may very well be present nearby, but it is likely to be sparse and scattered. A team of astronomers, from MPIA Heidelberg and Helsinki Observatory, hoped that the intergalactic dust might be easier to recognise in a large cluster of galaxies. They chose the Coma Cluster, which fills an area of the sky twice as wide as the Full Moon even though it is about 450 million light-years away. ISO scanned the Coma Cluster twice, along different cross-sections, measuring with ISOPHOT its emissions of long-wavelength infrared rays. The hunch of the German-Finnish team turned out to be correct. Emissions indicating the presence of intergalactic dust were much stronger towards the crowded centre of the cluster than at the edges. The results on the Coma Cluster obtained with ISO seem to contradict, at first sight, observations of the same cluster by another space observatory built in Europe. The German-US-UK Rosat satellite for X-ray astronomy has charted X-rays coming from very hot gas between the galaxies, and concentrated towards the centre of the Coma Cluster. The intergalactic gas detected by Rosat has a temperature of 80 million degrees, far hotter even than the core of the Sun. "The dust particles are at the very cold end of the temperature scale," says Kalevi Mattila of Helsinki Observatory. "ISOPHOT allows us to measure temperatures for them, in the range minus 220 to minus 250 degrees Celsius." How can cold dust at minus 250 degrees survive within a very hot gas? The gas is extremely tenuous, so it cannot simply warm the grains of dust like a hair-drier. Instead the hot gas subjects the dust to impacts by energetic atomic particles which knock atoms out of it, and so gradually erode the dust grains. Calculations suggest that the hot gas will destroy the cold dust in about 100 million years. Although that is very slow by human standards, it represents only one-hundredth of the age of the galaxies. Experts therefore have to consider where fresh supplies of intergalactic dust come from. Rosat astronomers found that the Coma Cluster is not spherical, which would be the shape expected in an isolated cluster. By X-rays, the cloud of hot intergalactic gas is seen to be egg-shaped. The same shape is apparent in the intergalactic dust cloud observed by IS

1997-11-01

2

Transonic Galactic Outflows and Their Influences to the Chemical Evolution of Galaxies and Intergalactic Space  

E-print Network

We have categorized possible transonic solutions of galactic outflows in the gravitational potential of DMH and SMBH using the isothermal, spherically symmetric and steady model. We conclude that the gravitational potential of SMBH generates a new transonic branch while Tsuchiya et al. (2013) concluded that the gravitational potential of DMH forms one transonic solution. Because these two transonic solutions have different mass fluxes and starting points, these solutions will make different influences to the star formation rate, the evolution of galaxies, and the chemical evolution of the intergalactic medium. Therefore, we conclude that the influence of galactic outflows to the intergalactic medium depends not only on the mass distribution but also on the selected transonic solution. In addition, we have estimated range of parameters (KDMH; KBH) for actual galaxies. Moreover, it may be possible to estimate the galactic mass distributions of DMH and SMBH applying the model to the observed profile of the outfl...

Igarashi, Asuka; Nitta, Shin-ya

2014-01-01

3

Scatter broadening of compact radio sources by the ionized intergalactic medium: Prospects for detection with Space VLBI and the SKA  

E-print Network

We investigate the feasibility of detecting and probing various components of the ionized intergalactic medium (IGM) and their turbulent properties at radio frequencies through observations of scatter broadening of compact sources. There is a strong case for conducting targeted observations to resolve scatter broadening (where the angular size scales as $\\sim \

Koay, J Y

2014-01-01

4

Intergalactic Star Formation  

E-print Network

Star formation in interacting systems may take place in various locations, from the dust--enshrouded core of Ultraluminous Infrared Galaxies to more unusual places such as the debris of colliding galaxies expelled into the intergalactic medium. Determining whether star-formation proceeds in the latter environment, far from the parent galaxies, in a similar way as in spiral disks has motivated the multi--wavelength study presented here. We collected VLA/HI, UV/GALEX, optical Halpha and MIR/Spitzer images of a few nearby interacting systems chosen for their prominent "intergalactic" star formation activity. Preliminary results on the spectacular collisional HI ring around NGC 5291 are presented.

Duc, P A; Braine, J; Brinks, E; Lisenfeld, U; Charmandaris, V; Duc, Pierre-Alain; Boquien, Meederic; Braine, Jonathan; Brinks, Elias; Lisenfeld, Ute; Charmandaris, Vassilis

2006-01-01

5

Intergalactic Star Formation  

E-print Network

Star formation in interacting systems may take place in various locations, from the dust--enshrouded core of Ultraluminous Infrared Galaxies to more unusual places such as the debris of colliding galaxies expelled into the intergalactic medium. Determining whether star-formation proceeds in the latter environment, far from the parent galaxies, in a similar way as in spiral disks has motivated the multi--wavelength study presented here. We collected VLA/HI, UV/GALEX, optical Halpha and MIR/Spitzer images of a few nearby interacting systems chosen for their prominent "intergalactic" star formation activity. Preliminary results on the spectacular collisional HI ring around NGC 5291 are presented.

Pierre-Alain Duc; Meederic Boquien; Jonathan Braine; Elias Brinks; Ute Lisenfeld; Vassilis Charmandaris

2006-10-13

6

Intergalactic Star Formation  

Microsoft Academic Search

Star formation in interacting systems may take place in various locations, from the dust--enshrouded core of Ultraluminous Infrared Galaxies to more unusual places such as the debris of colliding galaxies expelled into the intergalactic medium. Determining whether star-formation proceeds in the latter environment, far from the parent galaxies, in a similar way as in spiral disks has motivated the multi--wavelength

Pierre-Alain Duc; Meederic Boquien; Jonathan Braine; Elias Brinks; Ute Lisenfeld; Vassilis Charmandaris

2006-01-01

7

Intergalactic HI Clouds  

E-print Network

Neutral intergalactic clouds are so greatly out numbered by galaxies that their integral HI content is negligible in comparison to that contained in optically luminous galaxies. In fact, no HI cloud that is not associated with a galaxy or grouping of galaxies has yet been identified. This points to a causal relationship that relies on gravitational potentials that bind galaxies also being responsible for confining HI clouds to sufficient density that they can become self-shielding to the ionizing background radiation. Unconfined clouds of low density become ionized, but confined clouds find themselves vulnerable to instability and collapse, leading to star formation.

F. H. Briggs

2005-02-16

8

Telescope for Habitable Exoplanets and Interstellar/Intergalactic Astronomy  

E-print Network

THEIA Telescope for Habitable Exoplanets and Interstellar/Intergalactic Astronomy White Paper, Penn State, Princeton University, Space Telescope Science Institute, University of California University 1 #12;1. THEIA Overview Over the past 25 years, the Hubble Space Telescope has revolutionized our

9

Reionization of the Intergalactic Medium  

E-print Network

After recombination the cosmic gas was left in a cold and neutral state. However, as the first stars and black holes formed within early galactic systems, their UV and X-ray radiation induced a gradual phase transition of the intergalactic gas into the warm and ionized state we currently observe. This process is known as cosmic reionization. Understanding how the energy deposition connected with galaxy and star formation shaped the properties of the intergalactic gas is one of the primary goals of present-day cosmology. In addition, reionization back reacts on galaxy evolution, determining many of the properties of the high-redshift galaxy population that represent the current frontier of our discovery of the cosmos. In these two Lectures we provide a pedagogical overview of cosmic reionization and intergalactic medium and of some of the open questions in these fields.

Ferrara, Andrea

2014-01-01

10

The Physics and Early History of the Intergalactic Medium  

E-print Network

The intergalactic medium - the cosmic gas that fills the great spaces between the galaxies - is affected by processes ranging from quantum fluctuations in the very early universe to radiative emission from newly-formed stars. This gives the intergalactic medium a dual role as a powerful probe both of fundamental physics and of astrophysics. The heading of fundamental physics includes conditions in the very early universe and basic cosmological parameters. The astrophysics refers to chapters of the long cosmic history of stars and galaxies that are being revealed through the effects of stellar feedback on the cosmic gas. This review describes the physics of the intergalactic medium, focusing on recent theoretical and observational developments in understanding early cosmic history. In particular, radiation from the earliest generation of stars is thought to have transformed the universe, turning the surrounding atoms into free electrons and ions. Knowing exactly when and how the reionization process happened i...

Barkana, R; Barkana, Rennan; Loeb, Abraham

2006-01-01

11

The Search for Intergalactic Hydrogen Clouds in Voids  

Microsoft Academic Search

I present the results of a search for intergalactic hydrogen clouds in voids. Clouds are detected by their H I Lyalpha absorption lines in the Hubble Space Telescope spectra of low-redshift active galactic nuclei. The parameter with which the environments of clouds are characterized is the tidal field, for this places a lower limit on the cloud mass density that

Curtis V. Manning

2002-01-01

12

Ten More New Sightlines for the Study of Intergalactic Helium, and Hundreds of Far-Ultraviolet-Bright Quasars, from the Sloan Digital Sky Survey, Galaxy Evolution Explorer, and Hubble Space Telescope  

NASA Astrophysics Data System (ADS)

Absorption along quasar sightlines remains among the most sensitive direct measures of He II reionization in much of the intergalactic medium (IGM). Until recently, fewer than a half-dozen unobscured quasar sightlines suitable for the He II Gunn-Peterson test were known; although these handful demonstrated great promise, the small sample size limited confidence in cosmological inferences. We have recently added nine more such clean He II quasars, exploiting Sloan Digital Sky Survey (SDSS) quasar samples, broadband ultraviolet (UV) imaging from Galaxy Evolution Explorer (GALEX), and high-yield UV spectroscopic confirmations from Hubble Space Telescope (HST). Here we markedly expand this approach by cross-correlating SDSS DR7 and GALEX GR4+5 to catalog 428 SDSS and 165 other quasars with z > 2.78 having likely (~70%) GALEX detections, suggesting they are bright into the far-UV. Reconnaissance HST Cycle 16 Supplemental prism data for 29 of these new quasar-GALEX matches spectroscopically confirm 17 as indeed far-UV bright. At least 10 of these confirmations have clean sightlines all the way down to He II Ly?, substantially expanding the number of known clean He II quasars, and reaffirming the order of magnitude enhanced efficiency of our selection technique. Combined confirmations from this and our past programs yield more than 20 He II quasars, quintupling the sample. These provide substantial progress toward a sample of He II quasar sightlines large enough, and spanning a sufficient redshift range, to enable statistical IGM studies that may avoid individual object peculiarity and sightline variance. Our expanded catalog of hundreds of high-likelihood far-UV-bright QSOs additionally will be useful for understanding the extreme-UV properties of the quasars themselves. Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

Syphers, David; Anderson, Scott F.; Zheng, Wei; Haggard, Daryl; Meiksin, Avery; Schneider, Donald P.; York, Donald G.

2009-11-01

13

Gamma ray bursts, supernovae and metallicity in the intergalactic medium  

E-print Network

The mean iron abundance observed in the intergalactic medium (IGM) within galaxy clusters and without galaxy clusters is consistent with the mean amount of iron per unit volume in the Universe which has been produced by standard supernova (SN) explosions with a rate proportional to the cosmic star-formation rate. If most SNe took place inside galaxies, then the IGM could have been enriched with their metals by galactic winds and jets that swept most of the galactic gas with the SNe ejecta into the IGM. A significant fraction of the early SNe, however, could have taken place outside galaxies or within dwarf galaxies, which were later disrupted by tidal interactions, and/or mass loss through fast winds, SN ejecta and jets. Little is known about such intergalactic SNe at high red-shifts. They could have occurred primarily in highly obscured environments, avoiding detection. Supporting evidence for intergalactic SNe is provided by SNe associated with gamma ray bursts (GRBs) without a host galaxy and from the ratio of well localized GRBs with and without a host galaxy. A direct test of whether a significant contribution to the iron abundance in the IGM came from intergalactic SNe would require the measurement of their rate per comoving unit volume as function of red-shift. This may be feasible with IR telescopes, such as the Spitzer Space Telescope.

Shlomo Dado; Arnon Dar; A. De Rujula

2007-03-13

14

TEN MORE NEW SIGHTLINES FOR THE STUDY OF INTERGALACTIC HELIUM, AND HUNDREDS OF FAR-ULTRAVIOLET-BRIGHT QUASARS, FROM THE SLOAN DIGITAL SKY SURVEY, GALAXY EVOLUTION EXPLORER, AND HUBBLE SPACE TELESCOPE  

SciTech Connect

Absorption along quasar sightlines remains among the most sensitive direct measures of He II reionization in much of the intergalactic medium (IGM). Until recently, fewer than a half-dozen unobscured quasar sightlines suitable for the He II Gunn-Peterson test were known; although these handful demonstrated great promise, the small sample size limited confidence in cosmological inferences. We have recently added nine more such clean He II quasars, exploiting Sloan Digital Sky Survey (SDSS) quasar samples, broadband ultraviolet (UV) imaging from Galaxy Evolution Explorer (GALEX), and high-yield UV spectroscopic confirmations from Hubble Space Telescope (HST). Here we markedly expand this approach by cross-correlating SDSS DR7 and GALEX GR4+5 to catalog 428 SDSS and 165 other quasars with z > 2.78 having likely ({approx}70%) GALEX detections, suggesting they are bright into the far-UV. Reconnaissance HST Cycle 16 Supplemental prism data for 29 of these new quasar-GALEX matches spectroscopically confirm 17 as indeed far-UV bright. At least 10 of these confirmations have clean sightlines all the way down to He II Ly{alpha}, substantially expanding the number of known clean He II quasars, and reaffirming the order of magnitude enhanced efficiency of our selection technique. Combined confirmations from this and our past programs yield more than 20 He II quasars, quintupling the sample. These provide substantial progress toward a sample of He II quasar sightlines large enough, and spanning a sufficient redshift range, to enable statistical IGM studies that may avoid individual object peculiarity and sightline variance. Our expanded catalog of hundreds of high-likelihood far-UV-bright QSOs additionally will be useful for understanding the extreme-UV properties of the quasars themselves.

Syphers, David [Physics Department, University of Washington, Seattle, WA 98195 (United States); Anderson, Scott F.; Haggard, Daryl [Astronomy Department, University of Washington, Seattle, WA 98195 (United States); Zheng Wei [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Meiksin, Avery [Scottish Universities Physics Alliance (SUPA), Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ (United Kingdom); Schneider, Donald P. [Pennsylvania State University, Department of Physics and Astronomy, 525 Davey Lab, University Park, PA 16802 (United States); York, Donald G. [Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States)], E-mail: dsyphers@phys.washington.edu, E-mail: anderson@astro.washington.edu, E-mail: zheng@pha.jhu.edu

2009-11-01

15

The Clustering of Intergalactic Metals  

E-print Network

We measure the spatial clustering of metals in the intergalactic medium from z = 1.7 to 3.0, as traced by 643 CIV and 104 SiIV N >= 10^12 cm^-2 absorption systems in 19 high signal-to-noise (40-80) and high resolution (R = 45000) quasar spectra. The number densities and two-point correlation functions of both these species are largely constant with redshift, suggesting the bulk of metal ejection occurred at z >= 3. However, at z = M_s, and use numerical simulations to derive best-fit values of R_s ~ 2 comoving Mpc and M_s ~ 5x10^11 solar masses at z = 3. This does not exclude that metals could have been produced at higher redshifts in smaller, but equally rare, objects. At the level of detection of this survey, IGM enrichment is likely to be incomplete and inhomogeneous, with a filling factor ~ 10%.

Christophe Pichon; Evan Scannapieco; Bastien Aracil; Patrick Petitjean; Dominique Aubert; Jacqueline Bergeron; Stephane Colombi

2003-09-23

16

The Physics and Early History of the Intergalactic Medium  

E-print Network

The intergalactic medium - the cosmic gas that fills the great spaces between the galaxies - is affected by processes ranging from quantum fluctuations in the very early universe to radiative emission from newly-formed stars. This gives the intergalactic medium a dual role as a powerful probe both of fundamental physics and of astrophysics. The heading of fundamental physics includes conditions in the very early universe and basic cosmological parameters. The astrophysics refers to chapters of the long cosmic history of stars and galaxies that are being revealed through the effects of stellar feedback on the cosmic gas. This review describes the physics of the intergalactic medium, focusing on recent theoretical and observational developments in understanding early cosmic history. In particular, radiation from the earliest generation of stars is thought to have transformed the universe, turning the surrounding atoms into free electrons and ions. Knowing exactly when and how the reionization process happened is a primary goal of cosmologists, because this would tell us when the early stars and black holes formed and in what kinds of galaxies. Cosmic reionization is beginning to be understood with the help of theoretical models and computer simulations. A wide variety of instruments currently under design will probe the first sources of light during an epoch in cosmic history that has been largely unexplored so far. The new observations and the challenges for theoretical models and numerical simulations will motivate intense work in this field over the coming decade. (abridged)

Rennan Barkana; Abraham Loeb

2006-11-17

17

Polychromatic view of intergalactic star formation in NGC 5291  

NASA Astrophysics Data System (ADS)

Context: Star formation (SF) takes place in unusual places such as way out in the intergalactic medium out of material expelled from parent galaxies. Aims: Whether SF proceeds in this specific environment in a similar way than in galactic disks is the question we wish to answer. Particularly, we address the reliability of ultraviolet, H? and mid-infrared as tracers of SF in the intergalactic medium. Methods: We have carried out a multiwavelength analysis of the interacting system NGC 5291, which is remarkable for its extended HI ring hosting numerous intergalactic HII regions. We combined new ultraviolet (GALEX) observations with archival H?, 8 ?m (Spitzer Space Telescope) and HI (VLA B-array) images of the system. Results: We have found that the morphology of the star forming regions, as traced by the ultraviolet, H?, and 8 ?m emission is similar. The 8.0 ?m infrared emission, normalised to emission from dust at 4.5 ?m, which is known to be dominated by PAH bands, is comparable to the integrated emission of dwarf galaxies of the same metallicity and to the emission of individual HII regions in spirals. The 8.0 ?m in the intergalactic environment is therefore an estimator of the star formation rate which is as reliable in that extreme environment as it is for spirals. There is a clear excess of ultraviolet emission compared to individual HII regions in spirals, i.e. the [8.0]/[NUV] and [H?]/[NUV] SFR ratios are on average low although there are some large variations from one region to another, which cannot be explained by variations of the metallicity or the dust extinction along the HI structure. Comparing the observed SFR with a model of the evolution of [H?]/[NUV] with time favours young, quasi-instantaneous though already fading starbursts. The total star formation rate measured in the intergalactic medium (which accounts for 80% of the total) surrounding NGC 5291 is up to 1.3 M? yr-1 - a value typical for spirals - assuming the standard SFR calibrations are valid. The SFR drops by a factor of 2 to 4 in case the star formation is indeed quasi-instantaneous.

Boquien, M.; Duc, P.-A.; Braine, J.; Brinks, E.; Lisenfeld, U.; Charmandaris, V.

2007-05-01

18

INTERGALACTIC 'PIPELINE' FUNNELS MATTER BETWEEN COLLIDING GALAXIES  

NASA Technical Reports Server (NTRS)

This visible-light picture, taken by NASA's Hubble Space Telescope, reveals an intergalactic 'pipeline' of material flowing between two battered galaxies that bumped into each other about 100 million years ago. The pipeline [the dark string of matter] begins in NGC 1410 [the galaxy at left], crosses over 20,000 light-years of intergalactic space, and wraps around NGC 1409 [the companion galaxy at right] like a ribbon around a package. Although astronomers have taken many stunning pictures of galaxies slamming into each other, this image represents the clearest view of how some interacting galaxies dump material onto their companions. These results are being presented today at the 197th meeting of the American Astronomical Society in San Diego, CA. Astronomers used the Space Telescope Imaging Spectrograph to confirm that the pipeline is a continuous string of material linking both galaxies. Scientists believe that the tussle between these compact galaxies somehow created the pipeline, but they're not certain why NGC 1409 was the one to begin gravitationally siphoning material from its partner. And they don't know where the pipeline begins in NGC 1410. More perplexing to astronomers is that NGC 1409 is seemingly unaware that it is gobbling up a steady flow of material. A stream of matter funneling into the galaxy should have fueled a spate of star birth. But astronomers don't see it. They speculate that the gas flowing into NGC 1409 is too hot to gravitationally collapse and form stars. Astronomers also believe that the pipeline itself may contribute to the star-forming draught. The pipeline, a pencil-thin, 500 light-year-wide string of material, is moving a mere 0.02 solar masses of matter a year. Astronomers estimate that NGC 1409 has consumed only about a million solar masses of gas and dust, which is not enough material to spawn some of the star-forming regions seen in our Milky Way. The low amount means that there may not be enough material to ignite star birth in NGC 1409, either. The glancing blow between the galaxies was enough, however, to toss stars deep into space and ignite a rash of star birth in NGC 1410. The arms of NGC 1410, an active, gas-rich spiral galaxy classified as a Seyfert, are awash in blue, the signature color of star-forming regions. The bar of material bisecting the center of NGC 1409 also is a typical byproduct of galaxy collisions. Astronomers expect more fireworks to come. The galaxies are doomed to continue their game of 'bumper cars,' hitting each other and moving apart several times until finally merging in another 200 million years. The galaxies' centers are only 23,000 light-years apart, which is slightly less than Earth's distance from the center of the Milky Way. They are bound together by gravity, orbiting each other at 670,000 miles an hour (1 million kilometers an hour). The galaxies reside about 300 million light-years from Earth in the constellation Taurus. The Hubble picture was taken Oct. 25, 1999. Credits: NASA, William C. Keel (University of Alabama, Tuscaloosa)

2002-01-01

19

A population of very diffuse Lyman-? clouds as the origin of the He+ absorption signal in the intergalactic medium  

NASA Astrophysics Data System (ADS)

KNOWLEDGE of the physical state of the relatively uniform component of the intergalactic medium (the 'substrate') is critical to understanding the propagation of ionizing radiation and dynamical energy through intergalactic space, and for establishing the boundary conditions for the formation of the intergalactic gas clouds and galaxies that are assumed to have condensed from it. Uniformly distributed hydrogen, and, even more so, He+ will produce characteristic smooth absorption in the spectra of high-redshift quasars1-4, but at low spectral resolution it is difficult to distinguish such an absorption trough from the cumulative effect of absorption by the Lyman-? 'forest' of clouds. We report the detection of a population of weak 'forest' clouds with column density down to 2 x 1012 cm-2, and show that absorption in these clouds can account for a recent measurement1 of strong He+ absorption without necessarily having to invoke a diffuse intergalactic medium.

Songaila, A.; Hu, E. M.; Cowie, L. L.

1995-05-01

20

Intergalactic Hydrogen Clouds at Low Redshift: Connections to Voids and Dwarf Galaxies.  

National Technical Information Service (NTIS)

We provide new post-COSTAR data on one sightline (Mrk 421) and updated data from another (I Zw 1) from our Hubble Space Telescope (HST) survey of intergalactic Ly(alpha) clouds located along sightlines to four bright quasars passing through well-mapped ga...

J. M. Shull, J. T. Stocke, S. Penton

1996-01-01

21

Polychromatic View of Intergalactic Star Formation in NGC 5291  

E-print Network

Star formation (SF) takes place in unusual places such as way out in the intergalactic medium out of material expelled from parent galaxies. We wish to answer whether SF proceeds in this specific environment in a similar way than in galactic disks. We have carried out a multiwavelength analysis of the interacting system NGC 5291, which is remarkable for its extended HI ring hosting numerous intergalactic HII regions. We combined new ultraviolet (GALEX) observations with archival Halpha, 8 mu m (Spitzer Space Telescope) and HI (VLA B-array) images of the system. We have found that the morphology of the star forming regions, as traced by the ultraviolet, Halpha, and 8 mu m emission is similar. There is a clear excess of ultraviolet emission compared to individual HII regions in spirals, i.e. the [8.0]/[NUV] and [Halpha]/[NUV] SFR ratios are on average low although there are some large variations from one region to another, which cannot be explained by variations of the metallicity or the dust extinction along the HI structure. Comparing the observed SFR with a model of the evolution of [Halpha]/[NUV] with time favours young, quasi-instantaneous though already fading starbursts. The total star formation rate measured in the intergalactic medium (which accounts for 80% of the total) surrounding NGC 5291 is up to 1.3 Msun/yr, a value typical for spirals, assuming the standard SFR calibrations are valid. The SFR drops by a factor of 2 to 4 in case the star formation is indeed quasi-instantaneous. (abridged)

M. Boquien; P. -A. Duc; J. Braine; E. Brinks; U. Lisenfeld; V. Charmandaris

2007-03-01

22

Intergalactic star formation around NGC 5291  

Microsoft Academic Search

I will present a project aimed at characterizing systematically the intergalactic star formation taking place in gas expelled from galaxies into the IGM by tidal forces during close encounters. A part of the ejected gas collapses to form new stars and depending on dynamical conditions may even form new galaxies called \\

Médéric Boquien; Pierre-Alain Duc; Jonathan Braine; Elias Brinks; Vassilis Charmandaris; Ute Lisenfeld

2007-01-01

23

Star Formation in the Intergalactic Medium  

Microsoft Academic Search

Recent observations have shown that star formation may occur in the intergalactic medium outside any pre-existing stellar structure. Many of such giant HII complexes are progenitors of super star clusters or -- if they are very luminous -- dwarf galaxies, and are associated with tidal debris found in the vicinity of interacting systems. How star formation proceeds in this particular,

Ute Lisenfeld

2004-01-01

24

Massive stars and the intergalactic medium  

Microsoft Academic Search

We review the results of an X-ray (ASCA) survey of intergalactic medium metallicities in 33 groups and clusters of galaxies. The observed picture could be explained either by adopting top heavy IMF for galaxies observed at high environment overdensities or by metal-rich SN II driven winds.

Alexis Finoguenov; Monique Arnaud; Laurence P. David; Trevor J. Ponman

2000-01-01

25

Massive stars and the intergalactic medium  

Microsoft Academic Search

We review the results of an X-ray (ASCA) survey of intergalactic medium metallicities in 33 groups and clusters of galaxies. The observed picture could be explained either by adopting top heavy IMF for galaxies observed at high environment overdensities or by \\/metal-rich SN II driven winds.

A. Finoguenov; M. Arnaud; L. P. David; T. J. Ponman

2000-01-01

26

Polychromatic View of Intergalactic Star Formation in NGC 5291  

E-print Network

Star formation (SF) takes place in unusual places such as way out in the intergalactic medium out of material expelled from parent galaxies. We wish to answer whether SF proceeds in this specific environment in a similar way than in galactic disks. We have carried out a multiwavelength analysis of the interacting system NGC 5291, which is remarkable for its extended HI ring hosting numerous intergalactic HII regions. We combined new ultraviolet (GALEX) observations with archival Halpha, 8 mu m (Spitzer Space Telescope) and HI (VLA B-array) images of the system. We have found that the morphology of the star forming regions, as traced by the ultraviolet, Halpha, and 8 mu m emission is similar. There is a clear excess of ultraviolet emission compared to individual HII regions in spirals, i.e. the [8.0]/[NUV] and [Halpha]/[NUV] SFR ratios are on average low although there are some large variations from one region to another, which cannot be explained by variations of the metallicity or the dust extinction along t...

Boquien, M; Braine, J; Brinks, E; Lisenfeld, U; Charmandaris, V

2007-01-01

27

Cosmological Blastwaves and the Intergalactic Medium  

E-print Network

Winds from protogalactic starbursts and quasars can drive shocks that heat, ionize, and enrich the intergalactic medium. The Sedov-Taylor solution for point-like explosions adequately describes these blastwaves early in their development, but as the time since the explosion ($t - t_1$) approaches the age of the universe ($t$), cosmological effects begin to alter the blastwave's structure and growth rate. This paper presents an analytical solution for adiabatic blastwaves in an expanding universe, valid when the IGM is homogeneous and contains only a small fraction of the total mass density ($\\Omega_{\\rm IGM} << \\Omega_0$). Using this analytical solution, we examine the role protogalactic explosions might play in determining the state of intergalactic gas at $z \\sim 2 - 4$.

G. Mark Voit

1996-05-13

28

The thermal history of the intergalactic medium  

E-print Network

At redshifts z >~ 2, most of the baryons reside in the smooth intergalactic medium which is responsible for the low column density Lyman-alpha forest. This photoheated gas follows a tight temperature-density relation which introduces a cut-off in the distribution of widths of the Lyman-alpha absorption lines (b-parameters) as a function of column density. We have measured this cut-off in a sample of nine high resolution, high signal-to-noise quasar spectra, and determined the thermal evolution of the intergalactic medium in the redshift range 2.0-4.5. At redshift z ~ 3, the temperature at the mean density shows a peak and the gas becomes nearly isothermal. We interpret this as evidence for the reionization of HeII.

Joop Schaye; Tom Theuns; Michael Rauch; George Efstathiou; Wallace L. W. Sargent

1999-12-20

29

Galactic Corona or Local Group Intergalactic Medium?  

E-print Network

Cosmological hydrodynamic simulations predict that the low redshift universe comprises a web of warm-hot intergalactic gas and galaxies, with groups of galaxies and clusters forming at dense knots in these filaments. Our own Galaxy being no exception is also expected to be surrounded by the warm-hot intergalactic medium, filling the Local Group. Some theoretical models also predict the existence of a hot Galactic corona. With X-ray and FUV observations of extragalactic sources, we can probe the warm-hot gas through absorption lines of highly ionized elements. Indeed, Chandra, XMM and FUSE observations have detected z=0 absorption lines toward many sightlines. The debate that has emerged is over the interpretation of these observations: are the z=0 absorption systems from the halo of our Galaxy or from the extended Local Group environment? This has important implications for our understanding of the mass of the Local Group, the physical conditions in the intergalactic medium, the structure of the Galaxy and galaxy formation in general. We will present the current status of the debate and discuss our ongoing observing program aimed at understanding the z=0 absorption systems, with an emphasis on the high quality Chandra spectra of the Mrk 421 and Mrk 279 sightlines.

Rik J. Williams; Smita Mathur; Fabrizio Nicastro

2005-11-21

30

Intergalactic dust extinction in hydrodynamic cosmological simulations  

NASA Astrophysics Data System (ADS)

Recently Ménard et al. (hereafter MSFR) detected a subtle but systematic change in the mean colour of quasars as a function of their projected separation from foreground galaxies, extending to comoving separations of ˜10 h-1 Mpc, which they interpret as a signature of reddening by intergalactic dust. We present theoretical models of this remarkable observation, using smoothed particle hydrodynamic cosmological simulations of a (50 h-1 Mpc)3 volume. Our primary model uses a simulation with galactic winds and assumes that dust traces the intergalactic metals. The predicted galaxy-dust correlation function is similar in form to the galaxy-mass correlation function, and reproducing the MSFR data requires a dust-to-metal mass ratio of 0.24, about half the value in the Galactic interstellar medium (ISM). Roughly half of the reddening arises in dust that is more than 100 h-1 kpc from the nearest massive galaxy. We also examine a simulation with no galactic winds, which predicts a much smaller fraction of intergalactic metals (3 per cent versus 35 per cent) and therefore requires an unphysical dust-to-metal ratio of 2.18 to reproduce the MSFR data. In both models, the signal is dominated by sightlines with E(g-i) = 0.001-0.1. The no-wind simulation can be reconciled with the data if we also allow reddening to arise in galaxies up to several × 1010 M?. The wind model predicts a mean visual extinction of ? 0.0133 mag out to z= 0.5, with a sightline-to-sightline dispersion similar to the mean, which could be significant for future supernova cosmology studies. Reproducing the MSFR results in these simulations requires that a large fraction of ISM dust survive its expulsion from galaxies and its residence in the intergalactic medium. Future observational studies that provide higher precision and measure the dependence on galaxy type and environment will allow detailed tests for models of enriched galactic outflows and the survival of intergalactic dust.

Zu, Ying; Weinberg, David H.; Davé, Romeel; Fardal, Mark; Katz, Neal; Kereš, Dušan; Oppenheimer, Benjamin D.

2011-04-01

31

Intergalactic star formation around NGC 5291  

NASA Astrophysics Data System (ADS)

I will present a project aimed at characterizing systematically the intergalactic star formation taking place in gas expelled from galaxies into the IGM by tidal forces during close encounters. A part of the ejected gas collapses to form new stars and depending on dynamical conditions may even form new galaxies called "tidal dwarf galaxies". Those objects are chemically similar to star formation regions in spiral disks (roughly solar metallicity) but are dynamically similar to young dwarf galaxies. How star formation (star formation rate, initial mass function, age, extinction, dust properties, etc.) proceeds in such a particular environment, far away from the parent stellar disks, has yet not been studied in details. In order to get a better understanding of this mode of star formation, we performed a multi-wavelength study combining radio HI (VLA), mid-infrared (Spitzer), near-infrared and optical (ground based), and ultraviolet (Galex) data. We compared the properties of the intergalactic star forming regions (extinction, age, metallicity, dust properties) with those of several samples of dwarf galaxies and individual HII regions in different galaxies. Coupling those observations with spectra modelized using evolutive synthesis codes will allow us to determine precise measurements of the star formation rates and to obtain some constraints on the initial mass function.

Boquien, Médéric; Duc, Pierre-Alain; Braine, Jonathan; Brinks, Elias; Charmandaris, Vassilis; Lisenfeld, Ute

32

A NEW WAY OF DETECTING INTERGALACTIC BARYONS  

SciTech Connect

For each photon wave packet of extragalactic light, the dispersion by line-of-sight intergalactic plasma causes an increase in the envelope width and a chirp (drift) in the carrier frequency. It is shown that for continuous emission of many temporally overlapping wave packets with random epoch phases such as quasars in the radio band, this in turn leads to quasi-periodic variations in the intensity of the arriving light on timescales between the coherence time (defined as the reciprocal of the bandwidth of frequency selection, taken here as of order 0.01 GHz for radio observations) and the stretched envelope, with most of the fluctuation power on the latter scale which is typically in the millisecond range for intergalactic dispersion. Thus, by monitoring quasar light curves on such short scales, it should be possible to determine the line-of-sight plasma column along the many directions and distances to the various quasars, affording one a three-dimensional picture of the ionized baryons in the near universe.

Lieu, Richard; Duan Lingze [Department of Physics, University of Alabama, Huntsville, AL 35899 (United States)

2013-02-01

33

Effects of a hot intergalactic medium  

NASA Technical Reports Server (NTRS)

One effect a hot intergalactic medium (IGM) would have would be to produce an isotropic X-ray background through thermal bremsstrahlung. Such a background was modeled including both relativistic electron-ion and electron-electron emission; the observed X-ray measurements could be fit with a current temperature of 10.2 keV and Omega (IGM) of 0.27, assuming that the IGM was instantaneously heated at a redshift of 5 and cools by relativistic adiabatic expansion and Compton cooling. Such a hot IGM would also distort the cosmic microwave background spectrum by inverse Compton scattering off relativistic electrons. This distortion was modeled using the relativistic treatment. When including the recent data of Matsumoto et al., an undistorted radiation temperature of 2.86 K and an Omega (IGM) of 0.41 was found.

Taylor, Gregory B.; Wright, Edward L.

1989-01-01

34

The Warm-Hot Intergalactic Medium  

NASA Technical Reports Server (NTRS)

This grant is associated to a 5-year LTSA grant, on "Studying the Largest Reservoir of Baryons in the Universe: The Warm-Hot Intergalactic Medium". The first year of work within this program has been very rich, and has already produced several important results, as detailed in this paper. Table 2 of our original proposal justification, listed the planned year-by-year program, divided into two sub-fields: (A) the study of the z=0 (or Local Group WHIM) system, and (B) the study of the z greater than 0 (i.e- intervening WHIM) systems. For each of the two sub-fields we had planned to analyze, in the first year, a number of archival (Chandra, XMM and FUSE) and new (if observed) sightlines. Moreover, the plan for the z=0 system included the search for new interesting sightlines. We have accomplished all these tasks.

Hayes, Jeffrey (Technical Monitor)

2005-01-01

35

Constraints on dark matter from intergalactic radiation  

NASA Technical Reports Server (NTRS)

Several of the dark matter candidates that have been proposed are believed to be unstable to decay, which would contribute photons to the radiation field between galaxies. The main candidates of this type are light neutrinos and axions, primordial mini-black holes, and a nonzero 'vacuum' energy. All of these can be constrained in nature by observational data on the extragalactic background light and the microwave background radiation. Black holes and the vacuum can be ruled out as significant contributors to the 'missing mass'. Light axions are also unlikely candidates; however, those with extremely small rest energies (the so-called 'invisible' axions) remain feasible. Light neutrinos, like those proposed by Sciama, are marginally viable. In general, we believe that the intergalactic radiation field is an important way of constraining all types of dark matter.

Overduin, J. M.; Wesson, P. S.

1992-01-01

36

Intergalactic medium metal enrichment through dust sputtering  

NASA Astrophysics Data System (ADS)

We study the motion of dust grains into the intergalactic medium (IGM) around redshift z= 3, to test the hypothesis that grains can efficiently pollute the gas with metals through sputtering. We use the results available in the literature for radiation-driven dust ejection from galaxies as initial conditions and follow the motion onwards. Via this mechanism, grains are ejected into the IGM with velocities >100 km s-1 as they move supersonically, grains can be efficiently eroded by non-thermal sputtering. However, Coulomb and collisional drag forces effectively reduce the charged grain velocity. Up-to-date sputtering yields for graphite and silicate (olivine) grains have been derived using the code TRANSPORT OF IONS IN MATTER (TRIM), for which we provide analytic fits. After training our method on a homogeneous density case, we analyse the grain motion and sputtering in the IGM density field as derived from a ? cold dark matter (CDM) cosmological simulation at z= 3.27. We found that only large (a>~ 0.1?m) grains can travel up to considerable distances (few ×100 kpc physical) before being stopped. Resulting metallicities show a well-defined trend with overdensity ?. The maximum metallicities are reached for 10 < ? < 100[corresponding to systems, in quasi-stellar object (QSO) absorption spectra, with 14.5 < log N(HI) < 16]. However the distribution of sputtered metals is very inhomogeneous, with only a small fraction of the IGM volume polluted by dust sputtering (filling factors of 18 per cent for Si and 6 per cent for C). For the adopted size distribution, grains are never completely destroyed; nevertheless, the extinction and gas photoelectric heating effects resulting from this population of intergalactic grains are well below current detection limits.

Bianchi, Simone; Ferrara, Andrea

2005-04-01

37

Athena and the Missing Baryons in a Warm-Hot Intergalactic Medium  

NASA Astrophysics Data System (ADS)

Baryons are missing at all astronomical scales in the Universe, from galaxies to the large scales of structure formation and the Universe as a whole. Hydro-dynamical simulations for the formation of structures, tend to reconcile the different 'missing-baryon' problems and predict that most of the baryonic matter of the Universe is hiding in a hot and tenuous gaseous phase (dubbed the 'Warm-Hot Intergalactic Medium, or WHIM), surrounding virialized structures and more at large in the low-redshift inter-galactic space. The only way to secure the detection of this important and highly elusive baryonic component of the Universe, to constrain its physical, chemical and dynamical states, and so to measure its cosmological mass density, is by observing the intergalactic medium with instruments characterized by large collecting areas at the energies at which these baryons are supposed to shine, the soft X-ray band, and spectral resolution sufficient to resolve the weak emission and absorption lines produced by the hot light metals (mainly C, O, Ne) in the WHIM. The X-IFU of Athena, with its 2 m2 effective area at 1 keV and its superb 2.5 eV spectral resolution, will be a powerful WHIM machine. Here I will first summarize the current state of the art and will then focus on the large impulse that Athena will provide for such a rich and still relatively unexplored field of research.

Nicastro, Fabrizio; Kaastra, Jelle; Finoguenov, Alexis

38

The intergalactic medium in the cosmic web  

NASA Astrophysics Data System (ADS)

We request funding to perform a dedicated survey and analysis of theHST archive of COS-G130M quasar spectra to construct anabsorption-line catalog tuned to study the environment {i.e. large-scalestructure, LSS} of the intergalactic medium {IGM}. Specifically, wewill characterize the HI Lyman series absorption at z<0.1 andassociate metals for all absorbers along 100 quasar sightlinespenetrating the SDSS footprint. Using standard line-profile fittingtechniques, we will recover HI column densities and Dopplerparameters. These will be publicly released in a database thatincludes spectral masks identifying spurious spectral features,regions biased by previously known systems, etc. This catalog will beanalyzed in conjunction with the suite of LSS catalogs generated fromthe SDSS footprint {e.g. clusters, groups}, with emphasis on newalgorithms designed to identify and characterize galaxy voids.Through this analysis, we will test the predictions from ourcosmological paradigm that the IGM traces a so-called cosmic web ofLSS.

Tejos, Nicolas

2014-10-01

39

Star Formation in the Intergalactic Medium  

NASA Astrophysics Data System (ADS)

Recent observations have shown that star formation may occur in the intergalactic medium outside any pre-existing stellar structure. Many of such giant HII complexes are progenitors of super star clusters or -- if they are very luminous -- dwarf galaxies, and are associated with tidal debris found in the vicinity of interacting systems. How star formation proceeds in this particular, though simple environment, is so far unknown. We propose to image with GALEX two interacting systems showing tidal tails solely made of ejected gaseous material, in which we have already detected the formation of star-forming tidal dwarf galaxies. Both systems (NGC 5291 and NGC 4694/VCC 2062) lie in the outskirts of clusters of galaxies. Their UV fluxes will complement our multi-wavelength data set on these objects; they will be used to (1) study the recent star formation history and in particular infer the onset of the starburst actvity in the tidal tails (2) determine the UV SFR which we will compare with that derived in the optical and infrared, thus giving hints on the extinction law (3) estimate the star formation efficiency and compare it with that measured in grand design spirals and in classical dwarf galaxies.

Lisenfeld, Ute

40

The intergalactic medium in the cosmic web  

E-print Network

The intergalactic medium (IGM) accounts for ~90% of baryons at all epochs and yet its three dimensional distribution in the cosmic web remains mostly unknown. This is so because the only feasible way to observe the bulk of the IGM is through intervening absorption line systems in the spectra of bright background sources, which limits its characterization to being one-dimensional. Still, an averaged three dimensional picture can be obtained by combining and cross-matching multiple one-dimensional IGM information with three-dimensional galaxy surveys. Here, we present our recent and current efforts to map and characterize the IGM in the cosmic web using galaxies as tracers of the underlying mass distribution. In particular, we summarize our results on: (i) IGM around star-forming and non-star-forming galaxies; (ii) IGM within and around galaxy voids; and (iii) IGM in intercluster filaments. With these datasets, we can directly test the modern paradigm of structure formation and evolution of baryonic matter in t...

Tejos, Nicolas

2014-01-01

41

DIOS: the diffuse intergalactic oxygen surveyor: status and prospects  

NASA Astrophysics Data System (ADS)

DIOS (Diffuse Intergalactic Oxygen Surveyor) is a small scientific satellite with a main aim for the search of warm-hot intergalactic medium using redshifted OVII and OVIII lines. The instrument will consist of a 4-stage X-ray telescope and an array of TES microcalorimeters with 256 pixels, cooled with mechanical coolers. Hardware development of DIOS and the expected results are described. Survey observations over about 5° x 5° area will reveal new filamentary structures. DIOS will be proposed to the 3rd mission in JAXA's small satellite series in 2011, aiming for launch around 2016 if it will be selected.

Ohashi, T.; Ishisaki, Y.; Ezoe, Y.; Sasaki, S.; Kawahara, H.; Mitsuda, K.; Yamasaki, N. Y.; Takei, Y.; Ishida, M.; Tawara, Y.; Sakurai, I.; Furuzawa, A.; Suto, Y.; Yoshikawa, K.; Kawai, N.; Fujimoto, R.; Tsuru, T. G.; Matsushita, K.; Kitayama, T.

2010-07-01

42

Intergalactic Helium Absorption toward High-Redshift Quasars  

NASA Astrophysics Data System (ADS)

The recent Hubble Space Telescope (HST) observations of the zq = 3.286 quasar Q0302 -003 (Jakobsen et al. 1994) and the zq = 3.185 quasar Q1935 - 67 by Tytler (1995) show absorption edges at the redshifted wavelength of He II 304 Å. A key goal is to distinguish between contributions from discrete Ly? forest clouds and a smoothly distributed intergalactic medium (IGM). We model the contributions from each of these sources of He II absorption, including the distribution of line Doppler widths and column densities, the "He II proximity effect" from the quasar, and a self-consistent derivation of the He II opacity of the universe as a function of the spectrum of ionizing sources, with the assumption that both the clouds and the IGM are photoionized. The He II edge can be fully accounted for by He II line blanketing for reasonable distributions of line widths and column densities in the Lyman alpha forest, provided that the ionizing sources have spectral index ?s > 1.5, and any He II proximity effect is neglected. Even with some contribution from a diffuse IGM, it is difficult to account for the edge observed by Jakobsen et al. (1994) with a "hard" source spectrum (?s < 1.3). The proximity effect modifies the relative contributions of the clouds and IGM to ?He II near the quasar (z ? zq) and markedly increases the amount of He II absorption required. This implies, for example, that to account for the He 11 edge with line blanketing alone, the minimum spectral index ?s must be increased from 1.5 to 1.9. We demonstrate the need for higher resolution observations that characterize the change in transmission as z ? zq and resolve line-free gaps in the continuum. We set limits on the density of the diffuse IGM and suggest that the IGM and Lyman alpha clouds are likely to be a significant repository for dark baryons.

Giroux, Mark L.; Fardal, Mark A.; Shull, J. Michael

1995-10-01

43

Soft X-Ray Absorption by High-Redshift Intergalactic Helium.  

PubMed

The Lyalpha absorption from intergalactic, once-ionized helium (He ii) has been measured with the Hubble Space Telescope in four quasars over the last few years in the redshift range 2.4intergalactic medium (IGM) can be completely optically thick to Lyalpha photons when only a small fraction of the helium remains as He ii. In addition, finding quasars in which the He ii Lyalpha absorption can be observed becomes increasingly difficult at higher redshift owing to the large abundance of hydrogen Lyman limit systems. It is pointed out here that He ii in the IGM should also cause detectable continuum absorption in the soft X-rays. The spectrum of a high-redshift source seen behind the IGM when most of the helium was He ii should recover from the He ii Lyman continuum absorption at an observed energy of approximately 0.1 keV. Galactic absorption will generally be stronger, but not by a large factor; the intergalactic He ii absorption can be detected as an excess over the expected Galactic absorption from the 21 cm H i column density. In principle, this method allows a direct determination of the fraction of helium that was singly ionized as a function of redshift if the measurement is done on a large sample of high-redshift sources over a range of redshifts. PMID:10587481

Miralda-Escudé

2000-01-01

44

Intergalactic HeII absorption towards QSO 1157+3143  

Microsoft Academic Search

We report the discovery of a further line of sight allowing detection of He II Lyalpha absorption by the intergalactic medium. A HST\\/STIS survey of 32 bright z ˜ 3 quasars selected from the Hamburg Quasar Surveys yielded one detection toward QSO 1157+3143 (z ˜ 3, B ~= 17). A 10 orbit follow-up spectrum reveals a UV spectrum significantly suppressed

D. Reimers; C. Fechner; H.-J. Hagen; P. Jakobsen; D. Tytler; D. Kirkman

2005-01-01

45

Polychromatic view of intergalactic star formation in NGC 5291  

Microsoft Academic Search

Context: Star formation (SF) takes place in unusual places such as way out in the intergalactic medium out of material expelled from parent galaxies. Aims: Whether SF proceeds in this specific environment in a similar way than in galactic disks is the question we wish to answer. Particularly, we address the reliability of ultraviolet, Halpha and mid-infrared as tracers of

Mederic Boquien; P.-A. Duc; Jonathan Braine; Elias Brinks; Ute Lisenfeld; V. Charmandaris

2007-01-01

46

21 Centimeter Tomography of the Intergalactic Medium at High Redshift  

Microsoft Academic Search

We investigate the 21 cm signature that may arise from the intergalactic medium (IGM) prior to the epoch of full reionization (z > 5). In scenarios in which the IGM is reionized by discrete sources of photoionizing radiation, the neutral gas that has not yet been engulfed by an H II region may easily be preheated to temperatures well above

Piero Madau; Avery Meiksin; Martin J. Rees

1997-01-01

47

Quasar Absorbers and the InterGalactic Medium  

E-print Network

Quasar Absorbers and the InterGalactic Medium Simon C. Reynolds 8 March 2007 1 Introduction When we measure the spectra of quasars, we see many absorption lines super- imposed on the quasars' own emission spectra. These absorption features trace the intervening gas along our line of sight (LOS) to any quasar

Tittley, Eric

48

Turbulence Effect of the Intergalactic Medium  

NASA Astrophysics Data System (ADS)

The turbulence in the intergalactic medium (IGM) and its impact on the clustering of baryonic matter are investigated with the cosmological hydrodynamic simulation in the ?CDM framework. The observational tools that may be used to verify the possibility of the turbulence in the IGM are also discussed. A brief review of modern cosmology is given in chapter 1, mainly focusing on the dynamical equation of the scale factor -- Friedmann equation, and the theory background of the structure formation. Then the method of cosmological numerical simulation is introduced, as well as the cosmological hydrodynamic code WIGEON. After a short review of the turbulence in classic fluid mechanics, the IGM turbulence on large scales is investigated with simulations in chapter 2. The vorticity in the IGM velocity field significantly increases with time, as it can be effectively generated by shocks and complex structures. The vorticity field shows highly non-Gaussian and intermittent features. Its power spectrum is then used to measure the development of turbulence. The relation between the power spectra of vorticity and velocity indicates that the cosmic baryonic and velocity fields are in the state of fully developed turbulence within the scale range of 0.2h^{-1}˜ 3.0h^{-1} Mpc at z?0. The dynamical effect of the IGM turbulence on the baryon clustering is studied in chapter 3. The random motion of the turbulent fluid yields non-thermal turbulent pressure, which would enlarge the Jeans length, and hence delay and partly prevent the IGM from falling into the gravitational well of dark matter halos. Consequently, the baryon fraction f_{b} will deviate from its cosmic mean f_{b}^{cosmic}, and become highly nonuniform on the scales from a few hundred kpc to several Mpc, varying from as low as 1% to a few times of f_{b}^{cosmic}. The turbulence pressure in the IGM is weakly scale-dependent, and comparable to the gravitational energy density of the halos with masses of approximate 10^{11}h^{-1} M_{?}. f_{b} decreases from 0.8f_{b}^{cosmic} in the halos with masses of approximate 10^{12}h^{-1} M_{?} to 0.3f_{b}^{cosmic} in the halos with masses of approximate 10^{11}h^{-1} M_{?}, and shows further decrease when the halo mass is under 10^{11}h^{-1} M_{?}. The trend is similar to the observations, although the simulated f_{b} in halos is higher than the observed value by a factor of 2˜4. The turbulence of the IGM should be an important dynamical factor leading to the remarkable missing of the baryonic matter in the halos with masses of less than 10^{12}h^{-1} M_{?}. The IGM turbulence may introduce uncertainties to the kinetic Sunyaev-Zel'dovich (kSZ) effect and the Lyman alpha forest, and in turn could be constrained by future observations, which are discussed in chapter 4. The kSZ effect is sensitive to the curl component of the motions of the IGM. The structure functions of 2D simulated kSZ maps show strong intermittence, and the intermittent exponents follow a law similar to the She-Leveque scaling of fully developed turbulence. On the other hand, the intermittence is weak in the maps of thermal Sunyaev-Zel'dovich (tSZ) effect. Nevertheless, the superposition of the kSZ and tSZ effects still contains significant intermittence. The turbulent behavior of the IGM may be revealed by the observation of the SZ effect on angular scales equal to or less than 0.5'. The main results in this thesis are summarized in chapter 5, where future works are also discussed.

Zhu, W. S.

2013-07-01

49

Intergalactic Helium Absorption toward High-Redshift Quasars  

NASA Technical Reports Server (NTRS)

The recent Hubble Space Telescope (HST) observations of the z(q) = 3.286 quasar Q0302-003 (Jakobsen et at. 1994) and the z(q) = 3.185 quasar Q1935-67 by Tytler (1995) show absorption edges at the redshifted wavelength of He II 304 A. A key goal is to distinguish between contributions from discrete Ly-alpha forest clouds and a smoothly distributed intergalactic medium (IGM). We model the contributions from each of these sources of He II absorption, including the distribution of line Doppler widths and column densities, the 'He II proximity effect' from the quasar, and a self-consistent derivation of the He II opacity of the universe as a function of the spectrum of ionizing sources, with the assumption that both the clouds and the IGM are photoionized. The He II edge can be fully accounted for by He II line blanketing for reasonable distributions of line widths and column densities in the Ly-alpha forest, provided that the ionizing sources have spectral index alpha(s) greater than 1.5, and any He II proximity effect is neglected. Even with some contribution from a diffuse IGM, it is difficult to account for the edge observed by Jakobsen et al. (1994) with a 'hard' source spectrum (alpha(s) less than 1.3). The proximity effect modifies the relative contributions of the clouds and IGM to tau(He II) near the quasar (z approx. less than z(q)) and markedly increases the amount of He II absorption required. This implies, for example, that to account for the He II edge with line blanketing alone, the minimum spectral index alpha(s) must be increased from 1.5 to 1.9. We demonstrate the need for higher resolution observations that characterize the change in transmission as z approaches z(q) and resolve line-free gaps in the continuum. We set limits on the density of the diffuse IGM and suggest that the IGM and Ly-alpha clouds are likely to be a significant repository for dark baryons.

Giroux, Mark L.; Fardal, Mark A.; Shull, J. Michael

1995-01-01

50

THEIA: Telescope for Habitable Exoplanets and Interstellar/Intergalactic Astronomy  

NASA Astrophysics Data System (ADS)

By combining a 4 meter class optical/UV telescope with an occultor, we can build a mission capable of not only detecting and characterizing extrasolar planets but carrying out a broad program of astrophysics. I will present highlights from the science program of our mission concept study. The The THEIA telescope has several key instruments: an optical/UV coronagraph, a wide field camera operating in the optical and UV and a UV spectrograph that will probe the interstellar and intergalactic medium.

Spergel, David N.

2009-01-01

51

An updated analytic model for attenuation by the intergalactic medium  

NASA Astrophysics Data System (ADS)

We present an updated version of the so-called Madau model for attenuation of the radiation from distant objects by intergalactic neutral hydrogen. First, we derive the distribution function of intergalactic absorbers from the latest observational statistics of the Ly? forest, Lyman-limit systems and damped Ly? systems. The distribution function reproduces the observed redshift evolution of the Ly? depression and the mean-free path of the Lyman continuum excellently and simultaneously. We then derive a set of analytic functions describing the mean intergalactic attenuation curve for objects at z > 0.5. The new model predicts less (or more) Ly? attenuation for z ? 3-5 (z > 6) sources through the usual broad-band filters relative to the original Madau model. This may cause a systematic difference in the photometric redshift estimates, which is, however, still small: about 0.05. Finally, we find a more than 0.5 mag overestimation of Lyman-continuum attenuation in the original Madau model at z > 3, which causes a significant overcorrection against direct observations of the Lyman continuum of galaxies.

Inoue, Akio K.; Shimizu, Ikkoh; Iwata, Ikuru; Tanaka, Masayuki

2014-08-01

52

Compression of a gas cloud by pressure of the intergalactic medium  

SciTech Connect

It is shown that the evolution of an interstellar gas cloud that enters the space between galaxies depends strongly on the pressure of the hot intergalactic medium. If the difference between the pressure P/sub 0/ of the cloud and the ambient hot gas P/sub ext/ is large (P/sub ext//P/sub 0/ approx. 10), then in a wide range of masses and temperatures the cloud will be compressed without limit by the external pressure, being subsequently transformed into a star. For a moderate difference in the pressure (P/sub ext//P/sub 0/ approx. 3) the values of the parameters for which the clouds preserve their individuality are found as functions of the power of the heating source.

Sotnikova, N.Ya.

1987-01-01

53

FUSE and STIS Observations of the Warm-hot Intergalactic Medium toward PG 1259+593  

NASA Astrophysics Data System (ADS)

We use Far Ultraviolet Spectroscopic Explorer (FUSE) and Space Telescope Imaging Spectrograph (STIS) spectra to study intergalactic absorption toward the quasar PG 1259+593 (zem=0.478), with a particular emphasis on the warm-hot intergalactic medium (WHIM). The combined FUSE and STIS spectrum of PG 1259+593 covers the full wavelength range between 905 and 1730 Å at a spectral resolution of ~25 km s-1 for the FUSE bandpass (?<=1180 Å) and ~7 km s-1 for the STIS range (?>1150 Å). The signal-to-noise ratios (S/N) per resolution element are ~10-30 (FUSE) and ~7-17 (STIS). We identify 135 intergalactic absorption lines with equivalent widths >=10 mÅ, tracing 78 absorption components in 72 Ly?/Ly? absorption-line systems. Metal-line absorption by species such as C III, C IV, O III, O IV, O VI, and Si III is clearly detected in four systems and is possibly seen in four additional cases. We study the distribution and physical properties of the WHIM as sampled by O VI and intrinsically broad Ly? lines. The number of intervening O VI absorbers for equivalent widths W?>=24 mÅ is 3-6 over an unobscured redshift path of ?z~0.368. This implies a number density of O VI systems, dNOIV/dz, of ~8-16 above this equivalent width limit along this sight line. A seventh intervening O VI absorber is possibly detected with Wr(OVI)~15 mÅ. The range of dNOIV/dz=8-16 for W?>=24 mÅ is consistent with estimates from other sight lines, supporting the idea that intervening intergalactic O VI absorbers contain an substantial fraction of the baryonic mass in the low-redshift universe. We identify a number of broad Ly? absorbers with large Doppler parameters (b~40-200 km s-1) and low column densities [N(HI)<1014 cm-2]. For pure thermal broadening, these widths correspond to temperatures of ~1×105-3×106 K. While these broad absorbers could be caused by blends of multiple, unresolved lines, continuum undulations, or by kinematic flows and Hubble broadening, we consider the possibility that some of these features are single-component, thermally broadened Ly? lines. These systems could represent WHIM absorbers that are too weak, too metal-poor, and/or too hot to be detected in O VI. If so, their widths and their frequency in the PG 1259+593 spectrum imply that these absorbers trace an even larger fraction of the baryons in the low-redshift universe than the O VI absorbing systems. A thermal Doppler broadening explanation for one of these broad features is supported by the probable detection of O VI near the velocity of a broad Ly? and Ly? absorber with an O VI line width ~4 times smaller than for H I. ID="FN1"> 1Based partly on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

Richter, Philipp; Savage, Blair D.; Tripp, Todd M.; Sembach, Kenneth R.

2004-07-01

54

The Temperature Structure of the Warm-Hot Intergalactic Medium  

E-print Network

We study the temperature structure of the intergalactic medium (IGM) using a large cosmological N-body/SPH simulation. We employ a two-temperature model for the thermal evolution of the ionized gas, in which the relaxation process between electrons and ions is explicitly included. In the diffuse, hot IGM, the relaxation time is comparable to the age of the Universe and hence the electron temperature in post-shock regions remains significantly smaller than the ion temperature. We show that, at the present epoch, a large fraction of the warm/hot intergalactic medium (WHIM) has a well-developed two temperature structure, with typical temperature differences of order a factor of a few. Consequently, the fraction of metals in various ionization states such as OVI, OVII, and OVIII, as well as their line emissivities, can differ locally by more than an order of magnitude from those computed with a single temperature model. It is thus necessary to follow the evolution of the electron temperature explicitly to determine absorption and emission by the WHIM. Although equipartition is nearly achieved in the denser intracluster medium (ICM), we find an appreciable systematic deviation between the gas-mass weighted electron temperature and the mean temperature even at half the virial radii of clusters. There is thus a reservoir of warm (Te < 1keV) gas in and around massive clusters. Our results imply that relaxation processes need to be considered in describing and interpreting observational data from existing X-ray telescopes as well as from future missions designed to detect the WHIM, such as the Diffuse Intergalactic Oxygen Surveyor and the Missing Baryon Explorer.

Naoki Yoshida; Steven Furlanetto; Lars Hernquist

2004-10-21

55

FIREBALL: The Faint Intergalactic medium Redshifted Emission Balloon --Overview and 1st Science Flight Results  

E-print Network

FIREBALL: The Faint Intergalactic medium Redshifted Emission Balloon -- Overview and 1st Science Emission Balloon) is a balloon-borne 1m telescope coupled to an ultraviolet fiber-fed spectrograph the Faint Intergalactic-medium Redshifted Emission Balloon (FIREBALL), designed to discover and map faint

Martin, Chris

56

Intergalactic Extinction of High Energy Gamma-Rays  

NASA Technical Reports Server (NTRS)

We discuss the determination of the intergalactic pair-production absorption coefficient as derived by Stecker and De Jager by making use of a new empirically based calculation of the spectral energy distribution of the intergalactic infrared radiation field as given by Malkan and Stecker. We show that the results of the Malkan and Stecker calculation agree well with recent data on the infrared background. We then show that Whipple observations of the flaring gamma-ray spectrum of Mrk 421 hint at extragalactic absorption and that the HEGRA observations of the flaring spectrum of Mrk 501 appear to strongly indicate extragalactic absorption. We also discuss the determination of the y-ray opacity at higher redshifts, following the treatment of Salamon and Stecker. We give a predicted spectrum, with absorption included for PKS 2155-304. This XBL lies at a redshift of 0.12, the highest redshift source yet observed at an energy above 0.3 TeV. This source should have its spectrum steepened by approx. 1 in its spectral index between approx. 0.3 and approx. 3 TeV and should show an absorption cutoff above approx. 6 TeV.

Stecker, F. W.

1998-01-01

57

Constraints on the Intergalactic Transport of Cosmic Rays  

E-print Network

Motivated by recent experimental proposals to search for extragalactic cosmic rays (including anti-matter from distant galaxies), we study particle propagation through the intergalactic medium (IGM). We first use estimates of the magnetic field strength between galaxies to constrain the mean free path for diffusion of particles through the IGM. We then develop a simple analytic model to describe the diffusion of cosmic rays. Given the current age of galaxies, our results indicate that, in reasonable models, a completely negligible number of particles can enter our Galaxy from distances greater than $\\sim 100$ Mpc for relatively low energies ($E$ $< 10^6$ GeV/n). We also find that particle destruction in galaxies along the diffusion path produces an exponential suppression of the possible flux of extragalactic cosmic rays. Finally, we use gamma ray constraints to argue that the distance to any hypothetical domains of anti-matter must be roughly comparable to the horizon scale.

Fred C. Adams; Katherine Freese; Gregory Laughlin; Gregory Tarl{é}; Nathan Schwadron

1997-10-10

58

X-ray constraints on the intergalactic medium  

NASA Technical Reports Server (NTRS)

We use ROSAT Position Sensitive Proportional Counter (PSPC) spectra of z approximately equal 3 quasars to constrain the density and temperature of the intergalactic medium (IGM). Strong low-energy cutoffs in PSPC spectra of high-redshift quasars are common. However, the absence of absorption toward some high-redshift quasars can be used to put limits on the possible cosmological density, Omega(sub G), of a hot diffuse intergalactic medium (IGM), via an X-ray Gunn-Peterson test using edge and line opacity in the soft X-rays. The K-edges of oxygen, neon, and carbon and the L-edge of iron produce most of the absorption which is spread out by the redshift of the source. We assume an isotropic, isothermal, nonevolving model of the IGM and calculate the optical depth of this absorption. We find that this test can constrain an enriched IGM at temperatures near 10(exp 5) - 10(exp 6) K, intermediate between the hot IGM ruled out by COBE, and the cold IGM ruled out by the traditional Ly alpha Gunn -Peterson test. Photoionization if the IGM by the ultraviolet and X-ray background has a large effect. We give results for three z approximately equal 3 quasars and discuss how the various trade-offs among temperature, abundance, and backgroud radiation strength affect the limits on Omega (sub G). In addition to the high-redshift case, we discuss techniques for constraining the IGM using X-ray spectra of low-redhift quasars (z approximately equal 0.1 - 0.3). Currently available X-ray spectral data have insufficient energy resolution to constrain the IGM umambiguously, and so expected detection limits for future high-resolution spectrometers are presented. We find that with a large effective area (approximately 2000 sq cm), it is possible to substantially constrain or detect the IGM at the densities which are typically predicted.

Aldcroft, Thomas; Elvis, Martin; Mcdowell, Jonathan; Fiore, Fabrizio

1994-01-01

59

Abundant molecular gas in the intergalactic medium of Stephan's Quintet  

NASA Astrophysics Data System (ADS)

Stephan's Quintet (SQ) is a system consisting of at least four interacting galaxies which is well known for its complex dynamical and star formation history. It possesses a rich intergalactic medium (IGM), where hydrogen clouds, both atomic and molecular, associated with two starbursts (refered to as SQ A and B) have been found. In order to study the extent, origin and fate of the intergalactic molecular gas and its relation to the formation of stars outside galaxies and Tidal Dwarf Galaxies (TDGs), we mapped with the IRAM 30 m antenna the carbon monoxide (CO) towards several regions of the IGM in SQ. In both SQ A and B, we detected unusually large amounts of molecular gas (3.1 x 109 Msun and 7 x 108 Msun, respectively). In contrast, no significant CO detection was achieved towards HII regions south of the pair NGC 7318a/b despite their high H? luminosities. The molecular gas is very extended in both SQ A and SQ B, over areas of between 15 and 25 kpc. The CO clouds seem to have otherwise different properties and may be of a different nature. The integrated CO line of SQ A is in particular much wider than in SQ B. Its CO spectrum shows emission at two velocities (6000 and 6700 km s-1) that are coincident with two HI lines. The strongest emission at 6000 km s-1 is however spatially offset from the HI emission and situated on a ridge south-east of the starburst region. In SQ B the CO emission coincides with that of tracers of star formation (H? , 15 mu m and radio continuum). The CO peak lies slightly offset from the HI peak towards a steep HI gradient. This is indicating that the molecular gas is forming in-situ, possibly in a region of compressed HI, with subsequent star formation. The star forming region at SQ B is the object in SQ that most resembles a TDG.

Lisenfeld, U.; Braine, J.; Duc, P.-A.; Leon, S.; Charmandaris, V.; Brinks, E.

2002-11-01

60

Quasar spectroscopy in UV and X-ray- probing the intergalactic medium using helium and oxygen  

E-print Network

We employ ultraviolet (UV) and X-ray quasar spectroscopy to study the physical state of the Intergalactic Medium (IGM). First, we quantify the possibility of measuring the temperature of moderately over-dense regions of ...

Gong, Donglai, 1977-

2004-01-01

61

Electromagnetic Zero Point Field as Active Energy Source in the Intergalactic Medium  

E-print Network

For over twenty years the possibility that the electromagnetic zero point field (ZPF) may actively accelerate electromagnetically interacting particles in regions of extremely low particle density (as those extant in intergalactic space (IGS) with n energies. The recent finding by the AGASA collaboration (Phys. Rev. Lett., 81, 1163, 1998) that the CR energy spectrum does not display any signs of the Greisen-Zatsepin-Kuzmin cut-off (that should be present if these CR particles were indeed generated in localized ultrahigh energies CR sources, as e.g., quasars and other highly active galactic nuclei), may indicate the need for an acceleration mechanism that is distributed throughout IGS as is the case with the ZPF. Other unexplained phenomena that receive an explanation from this mechanism are the generation of X-ray and gamma-ray backgrounds and the existence of Cosmic Voids. However recently, a statistical mechanics kind of challenge to the classical (not the quantum) version of the zero-point acceleration mechanism has been posed (de la Pena and Cetto, The Quantum Dice, 1996). Here we briefly examine the consequences of this challenge and a prospective resolution.

Alfonso Rueda; Hiroki Sunahata; Bernhard Haisch

1999-06-16

62

Prospect on intergalactic magnetic field measurements with gamma-ray instruments  

NASA Astrophysics Data System (ADS)

Observing high-energy gamma-rays from Active Galactic Nuclei (AGN) offers a unique potential to probe extremely tiny values of the intergalactic magnetic field (IGMF), a long standing question of astrophysics, astroparticle physics and cosmology. Very high energy (VHE) photons from blazars propagating along the line of sight interact with the extragalactic background light (EBL) and produce e + e - pairs. Through inverse-Compton interaction, mainly on the cosmic microwave background (CMB), these pairs generate secondary GeV-TeV components accompanying the primary VHE signal. Such secondary components would be detected in the gamma-ray range as delayed ``pair echos'' for very weak IGMF (B < 10-16 G), while they should result in a spatially extended gamma-ray emission around the source for higher IGMF values (B > 10-16 G). Coordinated observations with space (i.e. Fermi) and ground-based gamma-ray instruments, such as the present Cherenkov experiments H.E.S.S., MAGIC and VERITAS, the future Cherenkov Telescope Array (CTA) Observatory, and the wide-field detectors such as HAWC and LHAASO, should allow to analyze and finally detect such echos, extended emission or pair halos, and to further characterize the IGMF.

Sol, Hélène; Zech, Andreas; Boisson, Catherine; Krawczynski, Henric; Fallon, Lisa; de Gouveia Dal Pino, Elisabete; Hinton, Jim; Inoue, Susumu; Neronov, Andrii; White, Richard

2013-07-01

63

The photoheating of the intergalactic medium in synthesis models of the UV background  

E-print Network

We compare cosmological hydrodynamical simulations combined with the homogeneous metagalactic UV background (UVB) of Haardt & Madau (2012) (HM2012) to observations of the Lyman-alpha forest that are sensitive to the thermal and ionization state of the intergalactic medium (IGM). The transition from optically thick to thin photoheating predicted by the simple one-zone, radiative transfer model implemented by HM2012 predicts a thermal history that is in remarkably good agreement with the observed rise of the IGM temperature at z~3 if we account for the expected evolution of the volume filling factor of HeIII. Our simulations indicate that there may be, however, some tension between the observed peak in the temperature evolution and the rather slow evolution of the HeII opacities suggested by recent Hubble Space Telescope/COS measurements. The HM2012 UVB also underpredicts the metagalactic hydrogen photoionization rate required by our simulations to match the observed opacity of the forest at z>4 and z<2.

Puchwein, Ewald; Haehnelt, Martin G; Madau, Piero; Becker, George D

2014-01-01

64

Equilibration processes in the Warm-Hot Intergalactic Medium  

E-print Network

The Warm-Hot Intergalactic Medium (WHIM) is thought to contribute about 40-50 % to the baryonic budget at the present evolution stage of the universe. The observed large scale structure is likely to be due to gravitational growth of density fluctuations in the post-inflation era. The evolving cosmic web is governed by non-linear gravitational growth of the initially weak density fluctuations in the dark energy dominated cosmology. Non-linear structure formation, accretion and merging processes, star forming and AGN activity produce gas shocks in the WHIM. Shock waves are converting a fraction of the gravitation power to thermal and non-thermal emission of baryonic/leptonic matter. They provide the most likely way to power the luminous matter in the WHIM. The plasma shocks in the WHIM are expected to be collisionless. Collisionless shocks produce a highly non-equilibrium state with anisotropic temperatures and a large differences in ion and electron temperatures. We discuss the ion and electron heating by the collisionless shocks and then review the plasma processes responsible for the Coulomb equilibration and collisional ionisation equilibrium of oxygen ions in the WHIM. MHD-turbulence produced by the strong collisionless shocks could provide a sizeable non-thermal contribution to the observed Doppler parameter of the UV line spectra of the WHIM.

A. M. Bykov; F. B. S. Paerels; V. Petrosian

2008-01-07

65

Ly? Heating of Inhomogeneous High-redshift Intergalactic Medium  

NASA Astrophysics Data System (ADS)

The intergalactic medium (IGM) prior to the epoch of reionization consists mostly of neutral hydrogen gas. Lyman-? (Ly?) photons produced by early stars resonantly scatter off hydrogen atoms, causing energy exchange between the radiation field and the gas. This interaction results in moderate heating of the gas due to the recoil of the atoms upon scattering, which is of great interest for future studies of the pre-reionization IGM in the H I 21 cm line. We investigate the effect of this Ly? heating in the IGM with linear density, temperature, and velocity perturbations. Perturbations smaller than the diffusion length of photons could be damped due to heat conduction by Ly? photons. The scale at which damping occurs and the strength of this effect depend on various properties of the gas, the flux of Ly? photons, and the way in which photon frequencies are redistributed upon scattering. To find the relevant length scale and the extent to which Ly? heating affects perturbations, we calculate the gas heating rates by numerically solving linearized Boltzmann equations in which scattering is treated by the Fokker-Planck approximation. We find that (1) perturbations add a small correction to the gas heating rate, and (2) the damping of temperature perturbations occurs at scales with comoving wavenumber k >~ 104 Mpc-1, which are much smaller than the Jeans scale and thus unlikely to substantially affect the observed 21 cm signal.

Oklop?i?, Antonija; Hirata, Christopher M.

2013-12-01

66

Exploring the intergalactic magnetic field by means of Faraday tomography  

NASA Astrophysics Data System (ADS)

Unveiling the intergalactic magnetic field (IGMF) in filaments of galaxies is a very important and challenging subject in modern astronomy. In order to probe the IGMF from rotation measures (RMs) of extragalactic radio sources, we need to separate RMs due to other origins such as the source, intervening galaxies, and our Galaxy. In this paper, we discuss observational strategies for the separation by means of Faraday tomography (Faraday RM synthesis). We consider an observation of a single radio source such as a radio galaxy or a quasar viewed through the Galaxy and the cosmic web. We then compare the observation with another observation of a neighboring source with a small angular separation. Our simulations with simple models of the sources suggest that it would be not easy to detect the RM due to an IGMF of order ˜ 1 rad m-2, an expected value for the IGMF through a single filament. Contrary to this, we find that an RM of at least ˜ 10 rad m-2 could be detected with the Square Kilometre Array or its pathfinders/precursors, if we achieve selection of ideal sources. These results would be improved if we incorporated decomposition techniques such as RMCLEAN and QU-fitting. We discuss the feasibility of the strategies for cases with complex Galactic emissions as well as with effects of observational noise and radio frequency interferences.

Akahori, Takuya; Kumazaki, Kohei; Takahashi, Keitaro; Ryu, Dongsu

2014-06-01

67

Exploring the intergalactic medium with VLT/UVES  

E-print Network

The remarkable efficiency of the UVES spectrograph at the VLT has made it possible to push high-resolution, high-S/N ground observations of the Ly-a forest down to z~1.5, gaining new insight into the physical conditions of the intergalactic medium and its evolution over more than 90% of the cosmic time. The universal expansion, the UV ionizing background and the gravitational condensation of structures are the driving factors shaping the number density and the column density distribution of the absorbers. A (limited) contribution of UV photons produced by galaxies is found to be important to reproduce the observed evolutionary pattern at very high and low redshift. The Lyman forest contains most of the baryons, at least at z>1.5, and acts as a reservoir for galaxy formation. The typical Doppler parameter at a fixed column density is measured to slightly increase with decreasing redshift, but the inferred temperature at the mean density is increasing with redshift. The signatures of HeII reionization and feedback from the formation of galactic structures have possibly been detected in the Lyman forest.

S. Cristiani; S. Bianchi; S. D'Odorico; T. -S. Kim

2001-12-12

68

Intergalactic HeII absorption towards QSO 1157+3143  

E-print Network

We report the discovery of a further line of sight allowing detection of HeII Ly alpha absorption by the intergalactic medium. A HST/STIS survey of 32 bright z ~ 3 quasars selected from the Hamburg Quasar Surveys yielded one detection toward QSO 1157+3143 (z ~ 3, B ~ 17). A 10 orbit follow-up spectrum reveals a UV spectrum significantly supressed by two intervening Lyman limit systems at z=2.77 and 2.94, but with the continuum flux recovering sufficiently shortward of ~ 1700 A to allow study of the HeII absorption spectrum in the redshift range 2.75 < z < 2.97. The absorption is characterized by alternating voids and dense filament structures seen in both HeII and HI. Attempts to model the HeII opacity in terms of HI Ly alpha forest absorption are not successful in the voids, suggesting that HeII reionization is not complete between z=2.77 and 2.97 or that an optically thin Lyman limit system with z ~ 0.3 is responsible for the additional opacity.

D. Reimers; C. Fechner; H. -J. Hagen; P. Jakobsen; D. Tytler; D. Kirkman

2005-07-07

69

Fluctuations of the intergalactic ionization field at redshift z ~ 2  

E-print Network

(Abridged) Aims. To probe the spectral energy distribution (SED) of the ionizing background radiation at z ~ 2 and to specify the sources contributing to the intergalactic radiation field. Methods. The spectrum of a bright quasar HS1103+6416 (zem = 2.19) contains five successive metal-line absorption systems at zabs = 1.1923, 1.7193, 1.8873, 1.8916, and 1.9410. The systems are optically thin and reveal multiple lines of different metal ions with the ionization potentials lying in the extreme ultraviolet (EUV) range (1 Ryd to 0.2 keV). For each system, the EUV SED of the underlying ionization field is reconstructed by means of a special technique developed for solving the inverse problem in spectroscopy. For the zabs = 1.8916 system, the analysis also involves the HeI resonance lines of the Lyman series and the HeI 504 A continuum, which are seen for the first time in any cosmic object except the Sun. Results. From one system to another, the SED of the ionizing continuum changes significantly, indicating that ...

Agafonova, I I; Reimers, D; Hagen, H -J; Tytler, D

2013-01-01

70

Intergalactic HeII absorption towards QSO 1157+3143  

E-print Network

We report the discovery of a further line of sight allowing detection of HeII Ly alpha absorption by the intergalactic medium. A HST/STIS survey of 32 bright z ~ 3 quasars selected from the Hamburg Quasar Surveys yielded one detection toward QSO 1157+3143 (z ~ 3, B ~ 17). A 10 orbit follow-up spectrum reveals a UV spectrum significantly supressed by two intervening Lyman limit systems at z=2.77 and 2.94, but with the continuum flux recovering sufficiently shortward of ~ 1700 A to allow study of the HeII absorption spectrum in the redshift range 2.75 < z < 2.97. The absorption is characterized by alternating voids and dense filament structures seen in both HeII and HI. Attempts to model the HeII opacity in terms of HI Ly alpha forest absorption are not successful in the voids, suggesting that HeII reionization is not complete between z=2.77 and 2.97 or that an optically thin Lyman limit system with z ~ 0.3 is responsible for the additional opacity.

Reimers, D; Hagen, H J; Jakobsen, P; Tytler, D; Kirkman, D

2005-01-01

71

Heating of Intergalactic Gas and Cluster Scaling Relations  

E-print Network

X-ray observations of galaxy groups and clusters are inconsistent with the predictions of the simplest hierarchical clustering models, wherein non-baryonic and baryonic components are assembled together under the sole influence of gravity. These departures are in the sense that the intergalactic medium is hotter and more extended than expected, and become increasingly strong for less massive systems. I model these effects by constructing baseline sequences of hydrostatic polytropic models normalized to observations of high-temperature clusters and numerical simulations, and then transforming them by adding proscribed amounts of heat per particle at the cluster center. I present sequences with a universal value of this heating parameter that simultaneously reproduce recently published observed (gas and total gravitational) mass-temperature and entropy-temperature relations. The required amount of energy injection is consistent with constraints on the number of supernovae needed to account for observed intracluster silicon abundances, provided that energy injection is centrally concentrated. I argue that most of the heating occurred during or after the assembly of the cluster, and not exclusively in pre-collapse proto-cluster fragments.

Michael Loewenstein

1999-10-14

72

FARADAY ROTATION MEASURE DUE TO THE INTERGALACTIC MAGNETIC FIELD  

SciTech Connect

Studying the nature and origin of the intergalactic magnetic field (IGMF) is an outstanding problem of cosmology. Measuring Faraday rotation would be a promising method to explore the IGMF in the large-scale structure (LSS) of the universe. We investigated the Faraday rotation measure (RM) due to the IGMF in filaments of galaxies using simulations for cosmological structure formation. We employed a model IGMF based on turbulence dynamo in the LSS of the universe, it has an average strength of (B) {approx} 10 nG and a coherence length of several x 100 h {sup -1} kpc in filaments. With the coherence length smaller than the path length, the inducement of RM would be a random walk process, and we found that the density peak along the line of sight dominantly contributes to the resultant RM. The root mean square of RM through filaments at the present universe was predicted to be {approx}1 rad m{sup -2}. In addition, we predicted that the probability distribution function of |RM| through filaments follows the lognormal distribution, and the power spectrum of RM in the local universe peaks at a scale of {approx}1 h {sup -1} Mpc. Our prediction of RM could be tested with future instruments.

Akahori, Takuya [Research Institute of Basic Science, Chungnam National University, Daejeon (Korea, Republic of); Ryu, Dongsu, E-mail: akataku@canopus.cnu.ac.k, E-mail: ryu@canopus.cnu.ac.k [Department of Astronomy and Space Science, Chungnam National University, Daejeon (Korea, Republic of)

2010-11-01

73

Simulating the interaction of galaxies and the intergalactic medium  

NASA Astrophysics Data System (ADS)

The co-evolution of galaxies and the intergalactic medium as a function of environment is studied using hydrodynamic simulations of the ?CDM cosmogony. It is demonstrated with non-radiative calculations that, in the absence of non-gravitational mechanisms, dark matter haloes accrete a near-universal fraction (˜ 0.9?_{b}/&Omega_;{m}) of baryons. The absence of a mass or redshift dependence of this fraction augurs well for parameter tests that use X-ray clusters as cosmological probes. Moreover, this result indicates that non-gravitational processes must efficiently regulate the formation of stars in dark matter haloes if the halo mass function is to be reconciled with the observed galaxy luminosity function. Simulations featuring stellar evolution and non-gravitational feedback mechanisms (photo-heating by the ultraviolet background, and thermal and kinetic supernovae feedback) are used to follow the evolution of star formation, and the thermo- and chemo-dynamical evolution of baryons. The observed star formation history of the Universe is reproduced, except at low redshift where it is overestimated by a factor of a few, possibly indicating the need for feedback from active galactic nuclei to quench cooling flows around massive galaxies. The simulations more accurately reproduce the observed abundance of galaxies with late-type morphologies than has been reported elsewhere. The unique initial conditions of these simulations, based on the Millennium Simulation, allow an unprecedented study of the role of large-scale environment to be conducted. The cosmic star formation rate density is found to vary by an order of magnitude across the extremes of environment expected in the local Universe. The mass fraction of baryons in the observationally elusive warm-hot intergalactic medium (WHIM), and the volume filling factor that this gas occupies, is also shown to vary by a factor of a few across such environments. This variation is attributed to differences in the halo mass functions of the environments. Finally, we compare the X-ray properties of haloes from the simulations with the predictions of the tet{White_and_Frenk_91} analytic galaxy formation model, and demonstrate that deviations from the analytic prediction arise from the assumptions i) that haloes retain their cosmic share of baryons, and ii) their gas follows an isothermal density profile. The simulations indicate that a significant fraction of gas is ejected from low mass haloes by galactic superwinds, leading to a significant increase in their cooling time profiles and an associated drop in their soft X-ray luminosities, relative to the analytic model. Simulated X-ray luminosities remain greater than present observational upper limits, but it is argued that the observations provide only weak constraints and may suffer from a systematic bias, such that the mass of the halo hosting a given galaxy is overestimated. This bias also follows from the assumption that haloes exhibit isothermal density profiles.

Carin, Robert A.

2008-11-01

74

Multifrequency survey of the intergalactic cloud in the M96 group  

NASA Technical Reports Server (NTRS)

The intergalactic cloud of neutral hydrogen in the M96 group are examined for signs of emission over a wide range of frequencies, from radio waves to X rays. Past or present stellar activity in the gas might have been expected to produce detectable visual infrared, CO, OH, or radio recombination-line emission. None was detected. The limits are used to study physical conditions in the intergalactic gas. In particular, B and V band limits on starlight and IRAS limits on the presence of dust strongly constrain the presence of stars or stellar by-products. However, given the uncertainties about physical conditions in the intergalactic environment, it is difficult to rule out entirely the presence of stellar-processed materials. Results of neutral hydrogen mapping from a large-scale survey of the intergalactic cloud and surrounding region are also presented. These observations confirm that the gas is confined to a large ringlike structure. The simplest interpretation remains that the intergalactic gas in Leo is primordial.

Schneider, Stephen E.; Skrutskie, M. F.; Hacking, Perry B.; Young, Judith S.; Dickman, Robert L.

1989-01-01

75

Intergalactic globular clusters and the faint end of the galaxy number counts in A1656 (Coma)  

E-print Network

The existence of an intergalactic globular cluster population in the Coma cluster of galaxies has been tested using surface-brightness fluctuations. The main result is that the intergalactic globular cluster surface density ($N_{\\rm IGC}$) does not correlate with the distance to the center of Coma and hence with the environment. Furthermore, comparing these results with different Coma mass-distribution model predictions, it is suggested that $N_{\\rm IGC}$ must in fact be zero all over Coma. On the other hand, the results for $N_{\\rm IGC}$ and the faint end of the galaxy number counts (beyond $m_R=23.5$) are connected. So $N_{\\rm IGC}=0$ settles the slope of this function, which turns out to be $\\gamma=0.36\\pm0.01$ down to $m_R=26.5$. The fact that $N_{\\rm IGC}=0$ all over Coma suggests that globular clusters were formed only, or almost only, from protogalactic clouds. None, or perhaps very few, could have formed in isolated regions. It also seems inappropriate to advocate a relationship between intergalactic globular clusters and dark matter distributions, although it is true that the relationship could still exist but not be strong enough to have been detected. Finally, since our conclusion is that intergalactic globular clusters do not exist in Coma, accretion of intergalactic globular clusters might not be significant in galaxy formation and evolutionary processes in the Coma galaxies.

A. Marin-Franch; A. Aparicio

2002-11-26

76

TEMPORAL SMEARING OF TRANSIENT RADIO SOURCES BY THE INTERGALACTIC MEDIUM  

SciTech Connect

The temporal smearing of impulsive radio events at cosmological redshifts probes the properties of the ionized intergalactic medium (IGM). We relate the degree of temporal smearing and the profile of a scattered source to the evolution of a turbulent structure in the IGM as a function of redshift. We estimate the degree of scattering expected by analyzing the contributions to the scattering measure of the various components of baryonic matter embedded in the IGM, including the diffuse IGM, intervening galaxies, and intracluster gas. These estimates predict that the amount of temporal smearing expected at 300 MHz is typically as low as ?1 ms and suggests that these bursts may be detectable with low-frequency widefield arrays. A generalization of the dispersion-measure-scattering-measure relation observed for Galactic scattering to the densities and turbulent conditions relevant to the IGM suggests that scattering measures on the order of 10{sup –6} kpc m{sup –20/3} would be expected at z ? 1. This scattering is sufficiently low enough that its effects would not, for most lines of sight, be manifested in existing observations of the scatter broadening in images of extragalactic compact sources. The redshift dependence on the temporal smearing discriminates between scattering that occurs in the host galaxy of the burst and the IGM, with ?{sub host}?(1 + z){sup –3} if the scattering probes length scales below the inner scale of the turbulence or ?{sub host}?(1 + z){sup –17/5} if the turbulence follows a Kolmogorov spectrum. This differs strongly from the expected IGM scaling ?{sub IGM} ? z {sup 2} for z ?< 1 and (1 + z){sup 0.2–0.5} for z ?> 1.

Macquart, Jean-Pierre; Koay, Jun Yi, E-mail: J.Macquart@curtin.edu.au [ICRAR/Curtin University, Curtin Institute of Radio Astronomy, Perth WA 6845 (Australia)

2013-10-20

77

Metallicity of the intergalactic medium using pixel statistics: III. Silicon  

E-print Network

(Modified) We study the abundance of silicon in the intergalactic medium by analyzing the statistics of SiIV, CIV, and HI pixel optical depths in a sample of 19 high-quality quasar absorption spectra spanning redshifts z ~ 2 - 4, which we compare to realistic spectra drawn from a hydrodynamical simulation. We find that silicon is highly overabundant relative to carbon and that the scatter in Si/C is much smaller than that in C/H, implying a common origin for Si and C. The inferred [Si/C] depends upon the shape of the UV background (UVB) (harder backgrounds leading to higher [Si/C]), ranging from [Si/C] ~ 1.5 for a quasar-only UVB, to [Si/C] ~ 0.25 for a UVB including both galaxies and an artificial softening. For our fiducial UVB, which includes both quasars and galaxies, we find [Si/C]=0.77 +/- 0.05, with a possible systematic error of ~ 0.1 dex. There is no evidence for evolution in [Si/C] and the data are inconsistent with previous claims of a sharp change in the SiIV/CIV ratio (or the UVB) at z ~ 3. Comparisons with low-metallicity halo stars and nucleosynthetic yields suggest that either our fiducial UVB is too hard or that supermassive Pop III stars might have to be included. The inferred [Si/C] corresponds to a contribution to the cosmic Si abundance of [Si/H] = -2.0, a significant fraction of all Si production expected by z ~ 3.

Anthony Aguirre; Joop Schaye; Tae-Sun Kim; Tom Theuns; Michael Rauch; Wallace L. W. Sargent

2003-10-22

78

THEIA: Telescope for Habitable Exoplanets and Interstellar/Intergalactic Astronomy  

NASA Astrophysics Data System (ADS)

By combining an occultor with a 4-meter optical/ultraviolet telescope, THEIA (Telescope for Habiatable Earths and Interstellar/Intergalactic Astronomy) will conduct an observational program that address many of the most exciting questions in astrophysics. The telescope is an on-axis telescope with a MgF-coated primary and a LiF-coated secondary. This hybrid approach allows reasonable through-put in the UV without the need to coat a large piimary with LiF. The coronagraph/occultor system is also a hybrid that aims to reduce the requirements on each approach. The telescope feeds a rich instrument complement. The eXtrasolar Planet Characterizer (XPC) baseline instruments are three narrow-field cameras for the UV (0.25-4.0 microns), blue (0.4-0.7 microns) and red (0.7-1.0 microns) with filters, and an integral field spectrograph (IFS) operating in the red. A wide-field high-resolution camera (Star Formation Camera) operating with a blue (190--517nm) and a red (517--1075nm) channel will conduct a comprehensive and systematic study of the astrophysical processes and environments relevant for the births and life cycles of stars and their planetary systems. A UV high-resolution spectrograph (UVS) with R=30,000-100,000 in the far-UV (1000-1700 A) and near-UV (1700-3000 A) will strengthen the foundations of observational cosmology by examining the cosmic web (IGM), its interactions with galaxies, and its enrichment with the products of stellar and galactic evolution. This mission has two basic opseration modes. While the occultor is moving from target star to target star, the telescope carries out an exciting program of general astrophysics. While the occultor is on target, it will characterize the key properties of a detected planet and deeply image adjacent fields in parallel mode.

Spergel, David N.; Kasdin, J.; Belikov, R.; Atcheson, P.; Beasley, M.; Calzetti, D.; Cameron, B.; Copi, C.; Desch, S.; Dressler, A.; Ebbets, D.; Egerman, R.; Fullerton, A.; Gallagher, J.; Green, J.; Guyon, O.; Heap, S.; Jansen, R.; Jenkins, E.; Kasting, J.; Keski-Kuha, R.; Kuchner, M.; Lee, R.; Lindler, D.; Linfield, R.; Lisman, D.; Lyon, R.; Malhotra, S.; Mathews, G.; McCaughrean, M.; Mentzel, J.; Mountain, M.; NIkzad, S.; O'Connell, R.; Oey, S.; Padgett, D.; Parvin, B.; Procashka, J.; Reeve, W.; Reid, I. N.; Rhoads, J.; Roberge, A.; Saif, B.; Scowen, P.; Seager, S.; Seigmund, O.; Sembach, K.; Shaklan, S.; Shull, M.; Soummer, R.

2009-01-01

79

Studying the Warm Hot Intergalactic Medium with Gamma-Ray Bursts  

NASA Astrophysics Data System (ADS)

We assess the possibility of detecting and characterizing the physical state of the missing baryons at low redshift by analyzing the X-ray absorption spectra of the gamma-ray burst (GRB) afterglows, measured by a microcalorimeter-based detector with 3 eV resolution and 1000 cm2 effective area and capable of fast repointing, similar to that on board of the recently proposed X-ray satellites EDGE and XENIA. For this purpose we have analyzed mock absorption spectra extracted from different hydrodynamical simulations used to model the properties of the warm hot intergalactic medium (WHIM). These models predict the correct abundance of O VI absorption lines observed in UV and satisfy current X-ray constraints. According to these models space missions such as EDGE and XENIA should be able to detect ~60 WHIM absorbers per year through the O VII line. About 45% of these have at least two more detectable lines in addition to O VII that can be used to determine the density and the temperature of the gas. Systematic errors in the estimates of the gas density and temperature can be corrected for in a robust, largely model-independent fashion. The analysis of the GRB absorption spectra collected in three years would also allow to measure the cosmic mass density of the WHIM with ~15% accuracy, although this estimate depends on the WHIM model. Our results suggest that GRBs represent a valid, if not preferable, alternative to active galactic nuclei to study the WHIM in absorption. The analysis of the absorption spectra nicely complements the study of the WHIM in emission that the spectrometer proposed for EDGE and XENIA would be able to carry out thanks to its high sensitivity and large field of view.

Branchini, E.; Ursino, E.; Corsi, A.; Martizzi, D.; Amati, L.; den Herder, J. W.; Galeazzi, M.; Gendre, B.; Kaastra, J.; Moscardini, L.; Nicastro, F.; Ohashi, T.; Paerels, F.; Piro, L.; Roncarelli, M.; Takei, Y.; Viel, M.

2009-05-01

80

Tracing the Cosmic Metal Evolution in the Low-redshift Intergalactic Medium  

NASA Astrophysics Data System (ADS)

Using the Cosmic Origins Spectrograph aboard the Hubble Space Telescope, we measured the abundances of six ions (C III, C IV, Si III, Si IV, N V, and O VI) in the low-redshift (z <= 0.4) intergalactic medium (IGM). Both C IV and Si IV have increased in abundance by a factor of ~10 from z ? 5.5 to the present. We derive ion mass densities, ?ion ? ?ion?cr, with ?ion expressed relative to the closure density. Our models of mass-abundance ratios, (Si III/Si IV) = 0.67+0.35-0.19, (C III/C IV) = 0.70+0.43-0.20, and (? C \\scriptsize{III} + ? C \\scriptsize{IV}) / (? _Si \\scriptsize{III} + ? _Si \\scriptsize{IV}) = 4.9+2.2-1.1, are consistent with the photoionization parameter log U = -1.5 ± 0.4, hydrogen photoionization rate ?H = (8 ± 2) × 10-14 s-1 at z < 0.4, and specific intensity I 0 = (3 ± 1) × 10-23 erg cm-2 s-1 Hz-1 sr-1 at the Lyman limit. Consistent ionization corrections for C and Si are scaled to an ionizing photon flux ?0 = 104 cm-2 s-1, baryon overdensity ? b ? 200 ± 50, and "alpha-enhancement" (Si/C enhanced to three times its solar ratio). We compare these metal abundances to the expected IGM enrichment and abundances in higher photoionized states of carbon (C V) and silicon (Si V, Si VI, and Si VII). Our ionization modeling infers IGM metal densities of (5.4 ± 0.5) × 105 M ? Mpc-3 in the photoionized Ly? forest traced by the C and Si ions and (9.1 ± 0.6) × 105 M ? Mpc-3 in hotter gas traced by O VI. Combining both phases, the heavy elements in the IGM have mass density ? Z = (1.5 ± 0.8) × 106 M ? Mpc-3 or ? Z ? 10-5. This represents 10% ± 5% of the metals produced by (6 ± 2) × 108 M ? Mpc-3 of integrated star formation with yield ym = 0.025 ± 0.010. The missing metals at low redshift may reside within galaxies and in undetected ionized gas in galactic halos and circumgalactic medium. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA Contract NAS5-26555.

Shull, J. Michael; Danforth, Charles W.; Tilton, Evan M.

2014-11-01

81

Redshifted intergalactic {sup 3}He{sup +} 8.7 GHz hyperfine absorption  

SciTech Connect

Motivated by recent interest in redshifted 21 cm emission of intergalactic hydrogen, we investigate the 8.7 GHz {sup 2}S{sub 1/2} F=0-1 hyperfine transition of {sup 3}He{sup +}. While the primordial abundance of {sup 3}He relative to hydrogen is 10{sup -5}, the hyperfine spontaneous decay rate is 680 times larger. Furthermore, the antenna temperature is much lower at the frequencies relevant for the {sup 3}He{sup +} transition compared to that of z>6 21 cm emission. We find that the spin temperature of this 8.7 GHz line in the intergalactic medium is approximately the cosmic microwave background temperature, such that this transition is best observed in absorption against high-redshift, radio-bright quasars. We show that intergalactic 8.7 GHz absorption is a promising, unsaturated observable of the ionization history of intergalactic helium (for which He II{yields}He III reionization is believed to complete at z{approx}3) and of the primordial {sup 3}He abundance. Instruments must reach {approx}1 {mu}Jy RMS noise in bands of 1 MHz on a 1 Jy source to directly resolve this absorption. However, in combination with H i Ly{alpha} forest measurements, an instrument can statistically detect this absorption from z>3 with 30 {mu}Jy RMS noise in 0.1 MHz spectral bands over 100 MHz, which may be within the reach of present instruments.

McQuinn, Matthew; Switzer, Eric R. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138 (United States); Kavli Institute for Cosmological Physics, University of Chicago, Chicago, Illinois, 60637 (United States)

2009-09-15

82

Confirmation of X-ray Absorption by Warm-hot Intergalactic Medium in the Sculptor Wall  

E-print Network

In a previous paper, we reported a 3? detection of an absorption line from the warm-hot intergalactic medium (WHIM) using the Chandra and XMM X-ray grating spectra of the blazar H2356-309, the sight line of which intercepts ...

Fang, Taotao

83

Multiple Absorption-line Spectroscopy of the Intergalactic Medium. I. Model  

Microsoft Academic Search

We present a physically based absorption-line model for the spectroscopic study of the intergalactic medium (IGM). This model adopts results from Cloudy simulations and theoretical calculations by Gnat & Sternberg to examine the resulting observational signatures of the absorbing gas with the following ionization scenarios: collisional ionization equilibrium (CIE), photoionization equilibrium, hybrid (photo- plus collisional ionization), and non-equilibrium cooling. As

Yangsen Yao; J. Michael Shull; Charles W. Danforth; Brian A. Keeney; John T. Stocke

2011-01-01

84

Evolution of Structure in the Intergalactic Medium and the Nature of the Ly alpha Forest  

Microsoft Academic Search

We have performed a detailed statistical study of the evolution of structure in a photoionized intergalactic medium (IGM) using analytical simulations to extend the calculation into the mildly nonlinear density regime found to prevail at z = 3. Our work is based on a simple fundamental conjecture: that the probability distribution function of the density of baryonic diffuse matter in

Hongguang Bi; Arthur F. Davidsen

1997-01-01

85

Intergalactic Hydrogen Clouds at Low Redshift: Connections to Voids and Dwarf Galaxies  

NASA Technical Reports Server (NTRS)

We provide new post-COSTAR data on one sightline (Mrk 421) and updated data from another (I Zw 1) from our Hubble Space Telescope (HST) survey of intergalactic Ly(alpha) clouds located along sightlines to four bright quasars passing through well-mapped galaxy voids (16000 km/s pathlength) and superclusters (18000 km/s). We report two more definite detections of low-redshift Ly(alpha) clouds in voids: one at 3047 km/s (heliocentric) toward Mrk 421 and a second just beyond the Local Supercluster at 2861 km/s toward I Zw 1, confirming our earlier discovery of Ly(alpha) absorption clouds in voids (Stocke et al., ApJ, 451, 24). We have now identified ten definite and one probable low-redshift neutral hydrogen absorption clouds toward four targets, a frequency of approximately one absorber every 3400 km/s above 10(exp 12.7/sq cm column density. Of these ten absorption systems, three lie within voids; the probable absorber also lies in a void. Thus, the tendency of Ly(alpha) absorbers to 'avoid the voids' is not as clear as we found previously. If the Ly(alpha) clouds are approximated as homogeneous spheres of 100 kpc radius, their masses are approximately 10(exp 9)solar mass (about 0.01 times that of bright L* galaxies) and they are 40 times more numerous, comparable to the density of dwarf galaxies and of low-mass halos in numerical CDM simulations. The Ly(alpha) clouds contribute a fraction Omega(sub cl)approximately equals 0.003/h(sub 75) to the closure density of the universe, comparable to that of luminous matter. These clouds probably require a substantial amount of nonbaryonic dark matter for gravitational binding. They may represent extended haloes of low-mass protogalaxies which have not experienced significant star formation or low-mass dwarf galaxies whose star formation ceased long ago, but blew out significant gaseous material.

Shull, J. Michael; Stocke, John T.; Penton, Steve

1996-01-01

86

THE RELATIONSHIP BETWEEN INTERGALACTIC H I/O VI AND NEARBY (z < 0.017) GALAXIES  

SciTech Connect

We analyze intergalactic H I and O VI absorbers with v < 5000 km s{sup -1} in Hubble Space Telescope and Far Ultraviolet Spectroscopic Explorer spectra of 76 active galactic nuclei. The baryons traced by H I/O VI absorption are clearly associated with the extended surroundings of galaxies; for impact parameters <400 kpc they are 2-4 times more numerous as those inside the galaxies. This large reservoir of matter likely plays a major role in galaxy evolution. We tabulate the fraction of absorbers having a galaxy of a given luminosity within a given impact parameter ({rho}) and velocity difference ({delta}v), as well as the fraction of galaxies with an absorber closer than a given {rho} and {delta}v. We identify possible 'void absorbers' ({rho} > 3 Mpc to the nearest L{sub *} galaxy), although at v < 2500 km s{sup -1} all absorbers are within 1.5 Mpc of an L>0.1 L{sub *} galaxy. The absorber properties depend on {rho}, but the relations are not simple correlations. For four absorbers with {rho} = 50-350 kpc from an edge-on galaxy with known orientation of its rotation, we find no clear relation between absorber velocities and the rotation curve of the underlying galaxy. For {rho} < 350 kpc, the covering factor of Ly{alpha} (O VI) around L>0.1 L {sub *} galaxies is 100% (70%) for field galaxies and 65% (10%) for group galaxies; 50% of galaxy groups have associated Ly{alpha}. All O VI absorbers occur within 550 kpc of an L>0.25 L{sub *} galaxy. The properties of three of 14 O VI absorbers are consistent with photoionization, for five the evidence points to collisional ionization; the others are ambiguous. The fraction of broad Ly{alpha} lines increases from z = 3 to z = 0 and with decreasing impact parameter, consistent with the idea that gas inside {approx}500 kpc from galaxies is heating up, although alternative explanations cannot be clearly excluded.

Wakker, B. P.; Savage, B. D. [Department of Astronomy, University of Wisconsin, 475 N. Charter St, Madison, WI 53706 (United States)

2009-05-15

87

MULTIPLE ABSORPTION-LINE SPECTROSCOPY OF THE INTERGALACTIC MEDIUM. I. MODEL  

SciTech Connect

We present a physically based absorption-line model for the spectroscopic study of the intergalactic medium (IGM). This model adopts results from Cloudy simulations and theoretical calculations by Gnat and Sternberg to examine the resulting observational signatures of the absorbing gas with the following ionization scenarios: collisional ionization equilibrium (CIE), photoionization equilibrium, hybrid (photo- plus collisional ionization), and non-equilibrium cooling. As a demonstration, we apply this model to new observations made with the Cosmic Origins Spectrograph aboard the Hubble Space Telescope of the IGM absorbers at z {approx} 0.1877 along the 1ES 1553+113 sight line. We identify Ly{alpha}, C III, O VI, and N V absorption lines with two distinct velocity components (blue at z{sub b} = 0.18757; red at z{sub r} = 0.18772) separated by {Delta}(cz)/(1 + z) {approx} 38 km s{sup -1}. Joint analyses of these lines indicate that none of the examined ionization scenarios can be applied with confidence to the blue velocity component, although photoionization seems to play a dominant role. For the red component, CIE can be ruled out, but pure photoionization and hybrid scenarios (with T < 1.3 x 10{sup 5} K) are more acceptable. The constrained ranges of hydrogen density and metallicity of the absorbing gas are n{sub H} = (1.9-2.3) x 10{sup -5} cm{sup -3} and Z = (0.43-0.67) Z{sub sun}. These constraints indicate O VI and H I ionization fractions, f{sub OVI} = 0.10-0.15 and f{sub HI} = (3.2-5.1) x 10{sup -5}, with total hydrogen column density N{sub H} = (0.7-1.2) x 10{sup 18} cm{sup -2}. This demonstration shows that the joint analysis of multiple absorption lines can constrain the ionization state of an absorber, and results used to estimate the baryonic matter contained in the absorber.

Yao Yangsen; Michael Shull, J.; Danforth, Charles W.; Keeney, Brian A.; Stocke, John T., E-mail: yaoys@colorado.edu [Center for Astrophysics and Space Astronomy, Department of Astrophysical and Planetary Sciences, University of Colorado, 389 UCB, Boulder, CO 80309 (United States)

2011-04-01

88

Hubble/COS Observations of Intergalactic Gas Toward PKS 0405-123  

NASA Astrophysics Data System (ADS)

We present an overview of far-UV Hubble Space Telescope observations (1150-1780 A, at 17 km/s resolution) taken by the Cosmic Origins Spectrograph (COS) of the QSO PKS 0405-123 at redshift zem = 0.5726 and FUV flux 3.5x10-14 erg/s/cm2/A. This spectrum illustrates the the power of COS for studying metal-enriched gas between the galaxies, distributed throughout the multiphase intergalactic medium (IGM). We used 7 orbits with 9 FP-split positions, obtained S/N = 35-45 over much of the G130M band (1150-1440 A), and detected numerous absorption features of hydrogen (Lya, Lyb) and heavy-element probes of metallicity. Ions that can be studied include lines (O VI, N V, Ne VIII) sensitive to hot gas produced by strong shocks produced in gravitational inflows to the Cosmic Web, in circumgalactic gas, and in galactic winds. The high S/N allows a search for broad Ly-alpha possibly associated with O VI in hot gas (105 to 106 K). This sight line also intercepts a high-velocity cloud seen in Si III at 110-170 km/s (LSR) and b = -37.55 in the Galactic halo. In the absorption system at z = 0.495, the Ne VIII doublet (770.41, 780.32 A) shifts into the COS band, allowing us to probe the warm-hot IGM at log T = 5.5-6.0, several times deeper than previous (STIS) studies (Prochaska et al. 2004; Howk et al. 2009). In other posters, members of the COS science team describe the detection of O VI absorbers at redshifts z = 0.16710, 0.18292, 0.36156, 0.36332, and 0.49501, including a Lyman Limit system at z = 0.16710 with log N(HI) = 16.45 +/- 0.05. The high S/N observations allow us to measure important ions previously not detected and to evaluate the kinematical relationships and physical conditions among the detected ions.

Shull, J. Michael; Danforth, C.; Froning, C.; Green, J.; Keeney, B.; Stocke, J.; Yao, Y.; Savage, B.; Narayanan, A.; Sembach, K.

2010-01-01

89

Hot Gas in the Local Group and Low-Redshift Intergalactic Medium  

E-print Network

There is increasing observational evidence that hot, highly ionized interstellar and intergalactic gas plays a significant role in the evolution of galaxies in the local universe. The primary spectral diagnostics of the warm-hot interstellar/intergalactic medium are ultraviolet and X-ray absorption lines of O VI and O VII. In this paper, I summarize some of the recent highlights of spectroscopic studies of hot gas in the Local Group and low-redshift universe. These highlights include investigations of the baryonic content of low-z O VI absorbers,evidence for a hot Galactic corona or Local Group medium, and the discovery of a highly ionized high velocity cloud system around the Milky Way.

Kenneth R. Sembach

2003-11-04

90

Secondary Photons and Neutrinos from Distant Blazars and the Intergalactic Magnetic Fields  

NASA Astrophysics Data System (ADS)

Secondary photons and neutrinos produced in the interactions of cosmic ray protons and gamma rays emitted by distant Active Galactic Nuclei (AGN) with the photon background along the line of sight can reveal a wealth of new information about the intergalactic magnetic fields (IGMF), extragalactic background light (EBL), and the acceleration mechanisms of cosmic rays. The secondary photons may have already been observed by gamma-ray telescopes. With the inclusion of secondary photons the current upper limits on the extragalactic background light are significantly weakened and new limits are set for the intergalactic magnetic fields for a wide range of cosmic ray and gamma ray models. Recent results from IceCube may also hint at the first observation of secondary neutrinos. Ramifications for the cosmic backgrounds, magnetic fields, and AGN models will be discussed.

Essey, Warren

2014-06-01

91

Expanding hydrodynamical jets crossing a galactic halo/intergalactic medium interface  

NASA Technical Reports Server (NTRS)

Parameters within ranges that are plausible for radio sources are presently used to perform two-dimensional hydrodynamical calculations of axisymmetric, initially conical, jets whose initial propagation is through isothermal galactic halos with power-law density distributions; these emerge across a pressure-matched interface into a hotter, but less dense medium whose parameters are typical of an intracluster or intergalactic gas. Upon crossing this interface, the jets accelerate and focused toward cylindrical shapes having long, narrow cocoons.

Wiita, Paul J.; Rosen, Alexander; Norman, Michael L.

1990-01-01

92

The impact of spatial fluctuations in the ultraviolet background on intergalactic carbon and silicon  

NASA Astrophysics Data System (ADS)

Spatial inhomogeneities in the spectral shape of the ultraviolet background (UVB) at the tail-end of He II reionization are thought to be the primary cause of the large fluctuations observed in the He II to H I Ly? forest optical depth ratio, ?, at z? 2-3. These spectral hardness fluctuations will also influence the ionization balance of intergalactic metals; we extract realistic quasar absorption spectra from a large hydrodynamical simulation to examine their impact on intergalactic Si IV and C IV absorbers. Using a variety of toy UVB models, we find that while the predicted spatial inhomogeneities in spectral hardness have a significant impact on ?, the longer mean free path for photons with frequencies above and below the He II ionization edge means these fluctuations have less effect on the Si IV and C IV ionization balance. Furthermore, UVB models which produce the largest fluctuations in specific intensity at the He II ionization edge also have the softest ionizing spectra, and thus result in photoionization rates which are too low to produce significant fluctuations in the observed ?. Instead, we find spatial variations in the IGM metallicity will dominate any scatter in ?. Our results suggest that observational evidence for homogeneity in the observed ? distribution does not rule out the possibility of significant fluctuations in the UVB spectral shape at z? 2-3. On the other hand, the scatter in metallicity inferred from observations of intergalactic C IV and Si IV absorption at z? 2-3 using spatially uniform ionization corrections is likely intrinsic, and therefore provides a valuable constraint on intergalactic metal enrichment scenarios at these redshifts.

Bolton, James S.; Viel, Matteo

2011-06-01

93

Reionization of the Intergalactic Medium and the Damping Wing of the Gunn-Peterson Trough  

Microsoft Academic Search

Observations of high-redshift quasars show that the intergalactic medium (IGM) must have been reionized at some redshift z > 5. If a source of radiation could be observed at the rest-frame Ly alpha wavelength, at a sufficiently high redshift where some of the IGM in the line of sight was not yet reionized, the Gunn-Peterson trough should be present. Longward

Jordi Miralda-Escude

1998-01-01

94

EVIDENCE FOR GAMMA-RAY HALOS AROUND ACTIVE GALACTIC NUCLEI AND THE FIRST MEASUREMENT OF INTERGALACTIC MAGNETIC FIELDS  

SciTech Connect

Intergalactic magnetic fields (IGMFs) can cause the appearance of halos around the gamma-ray images of distant objects because an electromagnetic cascade initiated by a high-energy gamma-ray interaction with the photon background is broadened by magnetic deflections. We report evidence of such gamma-ray halos in the stacked images of the 170 brightest active galactic nuclei (AGNs) in the 11 month source catalog of the Fermi Gamma-Ray Space Telescope. Excess over the point-spread function in the surface brightness profile is statistically significant at 3.5{sigma} (99.95% confidence level), for the nearby, hard population of AGNs. The halo size and brightness are consistent with IGMF, B {sub IGMF} {approx} 10{sup -15} G. The knowledge of IGMF will facilitate the future gamma-ray and charged-particle astronomy. Furthermore, since IGMFs are likely to originate from the primordial seed fields created shortly after the big bang, this potentially opens a new window on the origin of cosmological magnetic fields, inflation, and the phase transitions in the early universe.

Ando, Shin'ichiro [California Institute of Technology, Mail Code 350-17, Pasadena, CA 91125 (United States); Kusenko, Alexander, E-mail: ando@caltech.ed, E-mail: kusenko@ucla.ed [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States)

2010-10-10

95

Constraints on the Sunyaev-Zel'dovich signal from the warm-hot intergalactic medium from WMAP and SPT data  

NASA Astrophysics Data System (ADS)

The fraction of ionized gas in the warm-hot intergalactic medium induces temperature anisotropies on the cosmic microwave background similar to those of clusters of galaxies. The Sunyaev-Zel'dovich (SZ) anisotropies due to these low-density, weakly non-linear, baryon filaments cannot be distinguished from that of clusters using frequency information, but they can be separated since their angular scales are very different. To determine the relative contribution of the WHIM SZ signal to the radiation power spectrum of temperature anisotropies, we explore the parameter space of the concordance ? cold dark matter model using Monte Carlo Markov chains and the Wilkinson Microwave Anisotropy Probe 7 yr and South Pole Telescope data. We find marginal evidence of a contribution by diffuse gas, with amplitudes of AWHIM = 10-20 ?K2, but the results are also compatible with a null contribution from the WHIM, allowing us to set an upper limit of AWHIM < 43 ?K2 (95.4 per cent CL). The signal produced by galaxy clusters remains at ACL = 4.5 ?K2, a value similar to what is obtained when no WHIM is included. From the measured WHIM amplitude, we constrain the temperature-density phase diagram of the diffuse gas, and find it to be compatible with numerical simulations. The corresponding baryon fraction in the WHIM varies from 0.43 to 0.47, depending on model parameters. The forthcoming Planck data could set tighter constraints on the temperature-density relation.

Génova-Santos, Ricardo; Suárez-Velásquez, I.; Atrio-Barandela, F.; Mücket, J. P.

2013-07-01

96

X-ray Scattering through the Intergalactic Medium: Time Variability and Ghost Halos  

NASA Astrophysics Data System (ADS)

Dust grains polluting the intergalactic medium (IGM) have a chance of being detected through the phenomenon of X-ray scattering, which produces a diffuse arcminute-scale halo around bright X-ray point sources. We present follow up work to Corrales & Paerels (2012) by calculating the expected intensity of intergalactic dust scattering halos using the more exact Mie scattering treatment. This adjustment is necessary to check for large 0.1-1 micron sized dust grains that would interfere with the photometry needed for high precision measurements of cosmological constants. Even with the supreme focusing power of Chandra, we find that the dust scattering halo intensity is much dimmer than the Chandra PSF wings. However, scattered light takes a longer path to reach the observer, causing intergalactic scattering halos to be delayed ~10,000 years. I investigate the possibility of detecting a scattering halo around a quasar that has recently become dim, or ghost halos from quasars that are no longer visible.

Corrales, Lia

2014-08-01

97

The Influence of Plasma Effects of Pair Beams on the Intergalactic Cascade Emission of Blazars  

NASA Astrophysics Data System (ADS)

The attenuation of TeV ?-rays from distant blazars by the extragalactic background light (EBL) produces relativistic electron-positron pair beams. It has been shown by Broderick et. al. (2012) and Schlickeiser et. al (2012) that a pair beam traversing the intergalactic medium is unstable to linear two-stream instabilities of both electrostatic and electromagnetic nature. While for strong blazars all free pair energy is dissipated in heating the intergalactic medium and a potential electromagnetic cascade via inverse-Compton scattering with the cosmic microwave background is suppressed, we investigate the case of weak blazars where the back reaction of generated electrostatic turbulence leads to a plateauing of the electron energy spectrum. In the ultra-relativistic Thomson limit we analytically calculate the inverse-Compton spectral energy distribution for both an unplateaued and a plateaued beam scenario, showing a peak reduction factor of Rpeak ? 0.345. This is consistent with the FERMI non-measurements of a GeV excess in the spectrum of EBL attenuated TeV blazars. Claims on the lower bound of the intergalactic magnetic field strengths, made by several authors neglecting plasma effects, are thus put into question.

Menzler, Ulf; Schlickeiser, Reinhard

2014-03-01

98

A Determination of the Intergalactic Redshift Dependent UV-Optical-NIR Photon Density Using Deep Galaxy Survey Data and the Gamma-ray Opacity of the Universe  

NASA Technical Reports Server (NTRS)

We calculate the intensity and photon spectrum of the intergalactic background light (IBL) as a function of redshift using an approach based on observational data obtained in many different wavelength bands from local to deep galaxy surveys. This allows us to obtain an empirical determination of the IBL and to quantify its observationally based uncertainties. Using our results on the IBL, we then place 68% confidence upper and lower limits on the opacity of the universe to gamma-rays, free of the theoretical assumptions that were needed for past calculations. We compare our results with measurements of the extragalactic background light and upper limits obtained from observations made by the Fermi Gamma-ray Space Telescope.

Stecker, Floyd W.; Malkan, Matthew A.; Scully, Sean T.

2012-01-01

99

A DETERMINATION OF THE INTERGALACTIC REDSHIFT-DEPENDENT ULTRAVIOLET-OPTICAL-NIR PHOTON DENSITY USING DEEP GALAXY SURVEY DATA AND THE GAMMA-RAY OPACITY OF THE UNIVERSE  

SciTech Connect

We calculate the intensity and photon spectrum of the intergalactic background light (IBL) as a function of redshift using an approach based on observational data obtained in many different wavelength bands from local to deep galaxy surveys. This allows us to obtain an empirical determination of the IBL and to quantify its observationally based uncertainties. Using our results on the IBL, we then place 68% confidence upper and lower limits on the opacity of the universe to {gamma}-rays, free of the theoretical assumptions that were needed for past calculations. We compare our results with measurements of the extragalactic background light and upper limits obtained from observations made by the Fermi Gamma-ray Space Telescope.

Stecker, Floyd W. [Astrophysics Science Division, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Malkan, Matthew A. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1547 (United States); Scully, Sean T., E-mail: Floyd.W.Stecker@nasa.gov, E-mail: malkan@astro.ucla.edu, E-mail: scullyst@jmu.edu [Department of Physics, James Madison University, Harrisonburg, VA 22807 (United States)

2012-12-20

100

Intergalactic spaceflight: an uncommon way to relativistic kinematics and dynamics  

E-print Network

In the Special Theory of Relativity space and time intervals are different in different frames of reference. As a consequence, the quantity 'velocity' of classical mechanics splits into different quantities in Special Relativity, coordinate velocity, proper velocity and rapidity. The introduction and clear distinction of these quantities provides a basis to introduce the kinematics of uniform and accelerated motion in an elementary and intuitive way. Furthermore, rapidity links kinematics to dynamics and provides a rigorous way to derive Newtons Second Law in the relativistic version. Although the covariant tensorial notation of relativity is a powerful tool for dealing with relativistic problems, its mathematical difficulties may obscure the physical background of relativity for undergraduate students. Proper velocity and proper acceleration are the spatial components of the relativistic velocity and acceleration vectors, and thus, they provide a possibility to introduce and justify the vectorial notation of...

Greber, T; Blatter, Heinz; Greber, Thomas

2006-01-01

101

Space  

NSDL National Science Digital Library

This unit begins by introducing students to the historical motivation for space exploration. They learn about the International Space Station, including current and futuristic ideas that engineers are designing to propel space research. Then they learn about the physical properties of the Moon, and think about what types of products engineers would need to design in order for humans to live on the Moon. Lastly, students learn some descriptive facts about asteroids, such as their sizes and how that relates to the potential danger of an asteroid colliding with the Earth.

Integrated Teaching And Learning Program

102

Consequences of Starbursts for the Interstellar and Intergalactic Medium  

NASA Astrophysics Data System (ADS)

Star formation in general, and starbursts in particular, drive the evolution of galaxies. To understand the process of galactic matter cycle quantitatively, it is absolutely necessary to follow the evolution of the components of the interstellar medium, such as gas, magnetic fields, cosmic rays in detail over sufficiently long time scales. Due to the non-linearity of the interactions between the various components, and the turbulent nature of the plasma, high resolution numerical simulations offer the best strategy to further our understanding. The results of our numerical studies can be summarized as follows: (i) Supernova explosions are the most important energy input sources in the ISM and lead to a high level of turbulence in the plasma, coupling structures on all scales, (ii) more than half of the disk mass resides in classically thermally unstable temperature regimes, (iii) turbulent mixing is the dominant energy transport process over a wide range of scales, (iv) proportionality between magnetic field and density is generally weak, except for the densest regions, (v) magnetic fields, even if they are parallel to the galactic disk, cannot prevent outflow into the halo, (vi) the ionization structure of the plasma depends on its thermal history, and is in general not in collisional ionization equilibrium, (vii) the cooling function varies in space and time, (viii) X-rays can be emitted even at plasma temperatures of the order of 104K due to delayed recombination, both in the disk and the halo, (ix) cosmic rays can help driving a galactic wind, (x) cosmic rays can be accelerated to high energies beyond 1015eV (the "knee") in long lived shocks propagating into the galactic halo, because of time-dependent star formation.

Breitschwerdt, Dieter; de Avillez, Miguel; Dorfi, Ernst

103

Multiple Absorption-Line Spectroscopy of the Intergalactic Medium. I. Model  

Microsoft Academic Search

We present a physically-based absorption-line model for the spectroscopic\\u000astudy of the intergalactic medium (IGM). This model adopts results from Cloudy\\u000asimulations and theoretical calculations by Gnat and Sternberg (2007) to\\u000aexamine the resulting observational signatures of the absorbing gas with the\\u000afollowing ionization scenarios: collisional ionization equilibrium (CIE),\\u000aphotoionization equilibrium, hybrid (photo- plus collisional ionization), and\\u000anon-equilibrium cooling. As

Yangsen Yao; J. Michael Shull; Charles W. Danforth; Brian A. Keeney; John T. Stocke

2011-01-01

104

The physical properties of the redshift-three intergalactic medium from studies of QSO absorption line systems  

NASA Astrophysics Data System (ADS)

We present high quality optical and ultraviolet spectra of several high redshift QSOs, from the W. M. Keck and Hubble Space telescopes. We use the absorption lines from these spectra to study several aspects of the z ~ 3 intergalactic medium (IGM), including: (1) the distribution of clumped and smoothly distributed baryonic material; (2) The spectral shape of the ultraviolet ionizing background (UVB); (3) The properties of hierarchical merging events at z ~ 3, and (4) the baryonic content of the Universe. We have determined the statistical distributions which describe the Ly? forest absorption in neutral hydrogen (H I), and have shown that there are vast numbers of absorbers with H I column densities N HI < 1013 CM-2. We have used observations of singly ionized helium (HeII) Ly? forest absorption to show that there are not a significant number of absorbers with NHI < 1012 CM-2. We use observations of HeII Gunn-Peterson absorption to infer that only 1 to 5% of all baryons are in a smooth component of the IGM at z ~ 3. The rest of the baryons may be in the Ly? forest, with only <10 % in collapsed objects such as protogalaxies. We show that the UVB has a soft spectrum, with ? ? 1.77J912/ J228 > 104, indicating the Universe is not fully reionized at z ~ 3. We have placed a strong upper limit on the primordial deuterium to hydrogen ratio in a Lyman limit system (LLS) with simple velocity structure, and show that D/H is low: D/H < 6 × 10-5. This limit is consistent only with previous measurements of D/H which indicate the Universe's baryon density is ?bh2 = 0.019. We present the only two known intervening absorption systems which show O VI. These O VI absorbers are associated with LLS which display some, but not all, of the properties expected of a z ~ 3 hierarchical merging event.

Kirkman, David Albert

1999-07-01

105

On Modeling and Measuring the Temperature of the z ~ 5 Intergalactic Medium  

NASA Astrophysics Data System (ADS)

The temperature of the low-density intergalactic medium (IGM) at high redshift is sensitive to the timing and nature of hydrogen and He II reionization, and can be measured from Lyman-alpha (Ly?) forest absorption spectra. Since the memory of intergalactic gas to heating during reionization gradually fades, measurements as close as possible to reionization are desirable. In addition, measuring the IGM temperature at sufficiently high redshifts should help to isolate the effects of hydrogen reionization since He II reionization starts later, at lower redshift. Motivated by this, we model the IGM temperature at z >~ 5 using semi-numeric models of patchy reionization. We construct mock Ly? forest spectra from these models and consider their observable implications. We find that the small-scale structure in the Ly? forest is sensitive to the temperature of the IGM even at redshifts where the average absorption in the forest is as high as 90%. We forecast the accuracy at which the z >~ 5 IGM temperature can be measured using existing samples of high resolution quasar spectra, and find that interesting constraints are possible. For example, an early reionization model in which reionization ends at z ~ 10 should be distinguishable—at high statistical significance—from a lower redshift model where reionization completes at z ~ 6. We discuss improvements to our modeling that may be required to robustly interpret future measurements.

Lidz, Adam; Malloy, Matthew

2014-06-01

106

Intergalactic Electrostatic  

E-print Network

Wolfram Kahl Coconut: Code Constructing User Tool McMaster University http://ocalgorithms.com #12;Anand-Kahl - Coconut - CASCON 2007 Software Pipelining 11 3 stages #12;Anand-Kahl - Coconut - CASCON 2007 Software Pipelining · hide latency 11 3 stages #12;Anand-Kahl - Coconut - CASCON 2007 Software Pipelining · hide

Anand, Christopher

107

Cosmic gamma-ray propagation as a probe for intergalactic media and interactions  

NASA Astrophysics Data System (ADS)

Very-high-energy (VHE) gamma rays beyond 100 GeV, coming from galactic and extragalactic sources, reflect the most energetic non-thermal processes in the universe. The emission of these photons indicates the acceleration of charged particles to very high energies or the existence of exotic particles that annihilate or decay to photons. Observations of VHE gamma rays probing this highest energy window of electromagnetic waves thus can reveal the underlying acceleration processes or new astrophysical particles. The fluxes tend to be power-law spectra and this poses a difficulty for direct observation due to the low flux at the high-energy end and to the limited effective area of space-borne instruments. Ground-based VHE gamma-ray observatories therefore take advantage of the earth atmosphere as a calorimeter and observe the gamma rays indirectly via the electromagnetic cascade shower particles they produce. The shower particles are detected either directly or via the Cherenkov radiation they emit while propagating through the air. The current-generation telescopes adopting this ground-based methodology have confirmed several source categories and are starting to answer various physical and astronomical questions, e.g., the origin of cosmic rays, the nature of dark matter, the black hole accretion processes, etc. Together with multi-wavelength observations covering the full electromagnetic spectrum and astrophysical observatories of other particles (cosmic rays, neutrinos, etc.) VHE gamma-ray astronomy contributes as an indispensable part of the recently emerging field of multi-messenger particle astrophysics. When emitted by extragalactic sources, the VHE gamma rays undergo various interactions in the intergalactic medium as they propagate toward the earth. There is a guaranteed interaction, where the VHE gamma-ray photons are absorbed by the extragalactic background light (EBL), an isotropic background of optical-to-infrared photons coming from starlight or dust re-emission in the universe, producing electron-positron pairs. The pairs then upscatter ambient EBL and cosmic microwave background (CMB) photons to gamma rays, which are mostly high-energy (HE), i.e., between 100 MeV and 100 GeV. These secondary gamma rays could also trigger further pair production processes, resulting in an electromagnetic cascade in the cosmic voids. When there is no magnetic field present, all of the cascade gamma rays travel in virtually the same direction as the primary emissions from the source, adding to the observed gamma-ray flux. If the magnetic field in the voids is not negligible, however, the electron-positron pairs are deflected prior to inverse-Compton (IC) scattering on the background photons, impacting to the cascade photons an angular extension. The angular extension caused by the magnetic field both decreases the directly-observed source flux and creates a gamma-ray halo around the original source. An observation of the gamma-ray halo would therefore present a detection of the cosmic magnetic field, which so far has only upper limits imposed from Faraday rotation measurements of radio galaxies. On the other hand, by placing an upper limit on the HE gamma-ray flux of the source we can also derive a lower limit on the magnetic field. To address the processes involved in VHE gamma-ray propagation, I employ both semi-analytic models and full-scale Monte Carlo simulations derived from first principles. The two ways of approach give complementary perspectives on the physics involved and cross-check with each other to ensure a reliable result. By fitting the predicted cascade flux with observed data in both VHE and HE energy ranges by ground-based imaging atmospheric Cherenkov telescopes (IACTs) and the Fermi Large Area Telescope (LAT), I can place a robust lower limit on the extragalactic magnetic field (EGMF) strength at 10--16 to 10--15 Gauss, or at 10 --18 to 10--17 Gauss for a more conservative assumption on the source livetime. The lower limit rules out a large portion of the parameter space for the magnetic field cosmogenic mo

Huan, Hao

2012-05-01

108

Probing the Intergalactic Magnetic Field with the Anisotropy of the Extragalactic Gamma-Ray Background  

NASA Technical Reports Server (NTRS)

The intergalactic magnetic field (IGMF) may leave an imprint on the anisotropy properties of the extragalactic gamma-ray background, through its effect on electromagnetic cascades triggered by interactions between very high energy photons and the extragalactic background light. A strong IGMF will deflect secondary particles produced in these cascades and will thus tend to isotropize lower energy cascade photons, thus inducing a modulation in the anisotropy energy spectrum of the gamma-ray background. Here we present a simple, proof-of-concept calculation of the magnitude of this effect and demonstrate that the two extreme cases (zero IGMF and IGMF strong enough to completely isotropize cascade photons) would be separable by ten years of Fermi observations and reasonable model parameters for the gamma-ray background. The anisotropy energy spectrum of the Fermi gamma-ray background could thus be used as a probe of the IGMF strength.

Venters, T. M.; Pavlidou, V.

2012-01-01

109

Planetary Nebulae as Tracers of the Intergalactic Stellar Background: a Population Synthesis Theoretical Approach  

E-print Network

We wish to assess the relationship between the population of planetary nebulae (PNe) and a given parent stellar population from a theoretical point of view. Our results rely on original population synthesis models used to estimate the expected luminosity-specific PN density accounting for different evolutionary scenarios and star formation histories, as observed in galaxies in the near Universe. For a complete PN sample, we find that 1 PN/1.5E06 L(sun) a safe (IMF-independent) lower limit to the traced global bolometric luminosity of the parent stellar population. A tentative application to Virgo cluster data allows us to place a lower limit at ~7% for the global B luminosity of the cluster provided by "loose" intergalactic stars.

Alberto Buzzoni; Magda Arnaboldi

2004-07-12

110

The Gunn Peterson effect: a test for a black holes induced photoionization of the intergalactic medium  

E-print Network

Many experimental evidences indicate the presence of a ionizing background radiation flux at large redshifts; in some previous works I suggested the possibility that this ionizing flux comes from the quantum evaporation of primordial black holes (PBHs). Here I discuss the constraints that the experimental measurements put upon the free parameters of this reionization model and I study the absorption of the ionizing background due to $\\lia$ clouds: in particular, I discuss this phenomenon in presence of different absorption levels and I calculate the HI Gunn Peterson optical depth $\\tau_{GP}(z)$; from a comparison with the experimental data I obtain a constraint on the intergalactic medium density parameter, namely $\\Omega_{IGM}$ $<0.020$. A study of the characteristics of the absorbers is also performed; finally, the same kind of analysis is repeated for He II.

Marina Gibilisco

1996-09-06

111

The detection of oxygen in the low-density intergalactic medium  

E-print Network

The abundances of metals in the intergalactic medium (IGM) can be used to constrain the amount of star formation at high redshift and the spectral shape of the ionizing background radiation. For both purposes it is essential to measure the abundances in regions of low density, away from local sources of metals and ionizing photons. Here we report the first detection of OVI in the low-density IGM at high redshift. We perform a pixel-by-pixel search for OVI absorption in eight high quality quasar spectra spanning the redshift range z = 2.0-4.5. At 2 ~ 3 is consistent with the enhanced photoionization from a hardening of the UV background below z ~ 3 but could also be caused by the high level of contamination from Ly series lines.

Joop Schaye; Michael Rauch; Wallace L. W. Sargent; Tae-Sun Kim

2000-08-01

112

A census of H? emitters in the intergalactic medium of the NGC 2865 system  

NASA Astrophysics Data System (ADS)

Tidal debris, which are rich in HI gas and formed in interacting and merging systems, are suitable laboratories to study star formation outside galaxies. Recently, several such systems were observed, which contained many young star forming regions outside the galaxies. In previous works, we have studied young star forming regions outside galaxies in different systems with optical and/or gaseous tidal debris, in order to understand how often they occur and in which type of environments. In this paper, we searched for star forming regions around the galaxy NGC 2865, a shell galaxy that is circled by a ring of HI with a total mass of 1.2 × 109 M?. Using the multi-slit imaging spectroscopy technique with the Gemini telescope, we detected all H? emitting sources in the surroundings of the galaxy NGC 2865, down to a flux limit of 10-18 erg cm-2 s-1 Å-1. With the spectra information and the near and far-ultraviolet flux, we characterize the star formation rates, masses, ages, and metallicities for these HII regions. In total, we found 26 emission-line sources in a 60 × 60 Kpc field centered over the southeastern tail of the HI gas present around the galaxy NGC 2865. Out of the 26 H? emitters, 19 are in the satellite galaxy FGCE 0745, and seven are intergalactic HII regions scattered over the south tail of the HI gas around NGC 2865. We found that the intergalactic HII regions are young (<200 Myr) with stellar masses in the range 4 × 103 M? to 17 × 106 M?. These are found in a region of low HI gas density, where the probability of forming stars is expected to be low. For one of the intergalactic HII regions, we estimated a solar oxygen abundance of 12 + log(O/H) ~ 8.7. We also were able to estimate the metallicity for the satellite galaxy FGCE 0745 to be 12 + log(O/H) ~ 8.0. Given these physical parameters, the intergalactic HII regions are consistent with young star forming regions (or clusters), which are born in situ outside the NGC 2865 galaxy from a pre-enriched gas removed from the host galaxies in a merger event. The relevance of these observations is discussed. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência e Tecnologia (Brazil) and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina) - Observing runs: GS-2008A-Q-35.

Urrutia-Viscarra, F.; Arnaboldi, M.; Mendes de Oliveira, C.; Gerhard, O.; Torres-Flores, S.; Carrasco, E. R.; de Mello, D.

2014-09-01

113

Gas around galaxy haloes: methodology comparisons using hydrodynamical simulations of the intergalactic medium  

NASA Astrophysics Data System (ADS)

We perform cosmological simulations of the intergalactic medium (IGM) at redshift z ˜ 3 using the numerical gravity-hydrodynamics codes GADGET-3 and ENZO for the purpose of modelling the gaseous environments of galaxies. We identify haloes in the simulations using three different algorithms. Different rank orderings of the haloes by mass result, introducing a limiting factor, in identifying haloes with observed galaxies. We also compare the physical properties of the gas between the two codes, focusing primarily on the gas outside the virial radius, motivated by recent H I absorption measurements of the gas around z ˜ 2-3 galaxies. The internal dispersion velocities of the gas in the haloes have converged for a box size of 30 comoving Mpc, but the centre-of-mass peculiar velocities of the haloes have not up to a box size of 60 comoving Mpc. The density and temperature of the gas within the instantaneous turn-around radii of the haloes are adequately captured for box sizes of 30 Mpc on a side, but the results are highly sensitive to the treatment of unresolved, rapidly cooling gas, with the gas mass fraction within the virial radius severely depleted by star formation in the GADGET-3 simulations. Convergence of the gas peculiar velocity field on large scales requires a box size of at least 60 Mpc. Outside the turn-around radius, the physical state of the gas agrees to 30 per cent or better both with box size and between simulation methods. We conclude that generic IGM simulations make accurate predictions for the intergalactic gas properties beyond the halo turn-around radii, but the gas properties on smaller scales are highly dependent on star formation and feedback implementations.

Meiksin, Avery; Bolton, James S.; Tittley, Eric R.

2014-12-01

114

DETECTING THE WARM-HOT INTERGALACTIC MEDIUM THROUGH X-RAY ABSORPTION LINES  

SciTech Connect

The warm-hot intergalactic medium (WHIM) at temperatures 10{sup 5}-10{sup 7} K is believed to contain 30%-50% of the baryons in the local universe. However, all current X-ray detections of the WHIM at redshifts z > 0 are of low statistical significance ({approx}< 3{sigma}) and/or controversial. In this work, we aim to establish the detection limits of current X-ray observatories and explore requirements for next-generation X-ray telescopes for studying the WHIM through X-ray absorption lines. We analyze all available grating observations of Mrk 421 and obtain spectra with signal-to-noise ratios (S/Ns) of {approx}90 and 190 per 50 mA spectral bin from Chandra and XMM-Newton observations, respectively. Although these spectra are two of the best ever collected with Chandra and XMM-Newton, we cannot confirm the two WHIM systems reported by Nicastro et al. in 2005. Our bootstrap simulations indicate that spectra with such high S/N cannot constrain the WHIM with O VII column densities N{sub Ovii}{approx}10{sup 15} cm{sup -2} (corresponding to an equivalent width of 2.5 mA for a Doppler velocity of 50 km s{sup -1}) at {approx}> 3{sigma} significance level. The simulation results also suggest that it would take >60 Ms for Chandra and 140 Ms for XMM-Newton to measure the N{sub Ovii} at {>=}4{sigma} from a spectrum of a background QSO with flux of {approx}0.2 mCrab (1 Crab = 2 Multiplication-Sign 10{sup -8} erg s{sup -1} cm{sup -2} at 0.5-2 keV). Future X-ray spectrographs need to be equipped with spectral resolution R {approx} 4000 and effective area A {>=} 100 cm{sup 2} to accomplish the similar constraints with an exposure time of {approx}2 Ms and would require {approx}11 Ms to survey the 15 QSOs with flux {approx}> 0.2 mCrab along which clear intergalactic O VI absorbers have been detected.

Yao Yangsen; Shull, J. Michael; Cash, Webster [Center for Astrophysics and Space Astronomy, Department of Astrophysical and Planetary Sciences, University of Colorado, 389 UCB, Boulder, CO 80309 (United States); Wang, Q. Daniel, E-mail: yaoys@colorado.edu [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States)

2012-02-20

115

The impact of feedback on the low-redshift intergalactic medium  

NASA Astrophysics Data System (ADS)

We analyse the evolution of the properties of the low-redshift intergalactic medium (IGM) using high-resolution hydrodynamic simulations that include a detailed chemical evolution model. We focus on the effects that two different forms of energy feedback, strong galactic winds driven by supernova explosion and active galactic nuclei powered by gas accretion on to super-massive black holes (BHs), have on the thermo- and chemodynamical properties of the low-redshift IGM. We find that feedback associated with winds (W) and BHs leaves distinct signatures in both the chemical and thermal history of the baryons, especially at redshift z < 3. BH feedback produces an amount of gas with temperature in the range of 105-107K, the warm-hot intergalactic medium (WHIM), larger than that produced by the wind feedback. At z = 0, the fraction of baryons in the WHIM is about 50 per cent in the runs with BH feedback and about 40 per cent in the runs with wind feedback. The number of warm baryons (104 < T < 105K) is instead at about the same level, ~30 per cent, in the runs with BH and wind feedback. Also, BH feedback provides a stronger and more pristine enrichment of the WHIM. We find that the metal-mass-weighted age of WHIM enrichment at z = 0 is on average a factor of ~1.5 smaller in the BH run than for the corresponding runs with galactic winds. We present results for the enrichment in terms of mass and metallicity distributions for the WHIM phase, both as a function of density and as a function of temperature. Finally, we compute the evolution of the relative abundances between different heavy elements, namely oxygen, carbon and iron. While both C/O and O/Fe evolve differently at high redshifts for different feedback models, their values are similar at z = 0. We also find that changing the stellar initial mass function has a smaller effect on the evolution of the above relative abundances than changing the feedback model. The sensitivity of WHIM properties on the implemented feedback scheme could be important both for discriminating between different feedback physics and for detecting the WHIM with future far-UV and X-ray telescopes.

Tornatore, L.; Borgani, S.; Viel, M.; Springel, V.

2010-03-01

116

Evolution of Structure in the Intergalactic Medium and the Nature of the LY-Alpha Forest  

NASA Technical Reports Server (NTRS)

We have performed a detailed statistical study of the evolution of structure in a photoionized intergalactic medium (IGM) using analytical simulations to extend the calculation into the mildly nonlinear density regime found to prevail at z = 3. Our work is based on a simple fundamental conjecture: that the probability distribution function of the density of baryonic diffuse matter in the universe is described by a lognormal (LN) random field. The LN distribution has several attractive features and follows plausibly from the assumption of initial linear Gaussian density and velocity fluctuations at arbitrarily early times. Starting with a suitably normalized power spectrum of primordial fluctuations in a universe dominated by cold dark matter (CDM), we compute the behavior of the baryonic matter, which moves slowly toward minima in the dark matter potential on scales larger than the Jeans length. We have computed two models that succeed in matching observations. One is a nonstandard CDM model with OMEGA = 1, h = 0.5, and GAMMA = 0.3, and the other is a low-density flat model with a cosmological constant (LCDM), with OMEGA = 0.4, OMEGA(sub LAMBDA) = 0.6, and h = 0.65. In both models, the variance of the density distribution function grows with time, reaching unity at about z = 4, where the simulation yields spectra that closely resemble the Ly-alpha forest absorption seen in the spectra of high-z quasars. The calculations also successfully predict the observed properties of the Ly-alpha forest clouds and their evolution from z = 4 down to at least z = 2, assuming a constant intensity for the metagalactic UV background over this redshift range. However, in our model the forest is not due to discrete clouds, but rather to fluctuations in a continuous intergalactic medium. At z = 3; typical clouds with measured neutral hydrogen column densities N(sub H I) = 10(exp 13.3), 10(exp 13.5), and 10(exp 11.5) /sq cm correspond to fluctuations with mean total densities approximately 10, 1, and 0.1 times the universal mean baryon density. Perhaps surprisingly, fluctuations whose amplitudes are less than or equal to the mean density still appear as "clouds" because in our model more than 70% of the volume of the IGM at z = 3 is filled with gas at densities below the mean value.

Bi, Hongguang; Davidsen, Arthur F.

1997-01-01

117

Astrophysical bow shocks: An analytical solution for the hypersonic blunt body problem in the intergalactic medium  

E-print Network

Aims: Bow shock waves are a common feature of groups and clusters of galaxies since they are generated as a result of supersonic motion of galaxies through the intergalactic medium. The goal of this work is to present an analytical solution technique for such astrophysical hypersonic blunt body problems. Methods: A method, developed by Schneider (1968, JFM, 31, 397) in the context of aeronautics, allows calculation of the galaxy's shape as long as the shape of the bow shock wave is known (so-called inverse method). In contrast to other analytical models, the solution is valid in the whole flow region (from the stagnation point up to the bow shock wings) and in particular takes into account velocity gradients along the streamlines. We compare our analytical results with two-dimensional hydrodynamical simulations carried out with an extended version of the VH-1 hydrocode which is based on the piecewise parabolic method with a Lagrangian remap. Results: It is shown that the applied method accurately predicts the...

Schulreich, Michael Mathias

2011-01-01

118

Heating and ionization of the primordial intergalactic medium by high-mass X-ray binaries  

NASA Astrophysics Data System (ADS)

We investigate the influence of high-mass X-ray binaries (HMXBs) on their high-redshift environments. Using a one-dimensional radiative transfer code, we predict the ionization and temperature profiles surrounding a coeval stellar population, composed of main-sequence stars and HMXBs, at various times after its formation. We consider both uniform density surroundings, and a cluster embedded in a 108 M? Navarro-Frenk-White (NFW) halo. HMXBs in a constant density environment produce negligible enhanced ionization because of their high-energy spectral energy distributions and short lifetimes. In this case, HMXBs only marginally contribute to the local heating rate. For NFW profiles, radiation from main-sequence stars cannot prevent the initially ionized volume from recombining since it is unable to penetrate the high-density galactic core. However, HMXB photons stall recombinations behind the front, keeping it partially ionized for longer. The increased electron density in these partially ionized regions promotes further cooling, resulting in lower intergalactic medium (IGM) temperatures. In the context of this starburst model, we have shown that HMXBs do not make a major contribution to reionization or IGM heating. However, X-ray escape fractions are high in both density profile cases. Continuous star formation may result in the build up of X-rays over time, reducing the ionization time-scale and potentially leading to low level ionization of the distant IGM.

Knevitt, G.; Wynn, G. A.; Power, C.; Bolton, J. S.

2014-12-01

119

Towards a unified description of the intergalactic medium at redshift z ? 2.5  

NASA Astrophysics Data System (ADS)

We examine recent measurements of the z ? 2.5 intergalactic medium (IGM) which constrain the H I frequency distribution f(N_{H I}) and the mean free path ? _mfp^{912} to ionizing radiation. We argue that line-blending and the clustering of strong absorption-line systems have led previous authors to systematically overestimate the effective Lyman limit opacity, yielding too small of a ? _mfp^{912} for the IGM. We further show that recently published measurements of f(N_{H I}) at N_{H I}? 10^{16} cm^{-2} lie in strong disagreement, implying underestimated uncertainty from sample variance and/or systematics like line-saturation. Allowing for a larger uncertainty in the f(N_{H I}) measurements, we provide a new cubic Hermite spline model for f(N_{H I}) which reasonably satisfies all of the observational constraints under the assumption of randomly distributed absorption systems. We caution, however, that this formalism is invalid in the light of absorber clustering and use a toy model to estimate the effects. Future work must properly account for the non-Poissonian nature of the IGM.

Prochaska, J. Xavier; Madau, Piero; O'Meara, John M.; Fumagalli, Michele

2014-02-01

120

Intergalactic Magnetic Fields and Gamma-Ray Observations of Extreme TeV Blazars  

NASA Astrophysics Data System (ADS)

The intergalactic magnetic field (IGMF) in cosmic voids can be indirectly probed through its effect on electromagnetic cascades initiated by a source of teraelectronvolt (TeV) gamma-rays, such as active galactic nuclei (AGNs). AGNs that are sufficiently luminous at TeV energies, "extreme TeV blazars", can produce detectable levels of secondary radiation from inverse Compton scattering of the electrons in the cascade, provided that the IGMF is not too large. We review recent work in the literature that utilizes this idea to derive constraints on the IGMF for three TeV-detected blazars, 1ES 0229+200, 1ES 1218+304, and RGB J0710+591, and we also investigate four other hard-spectrum TeV blazars in the same framework. Through a recently developed, detailed, three-dimensional particle-tracking Monte Carlo code, incorporating all major effects of QED and cosmological expansion, we research the effects of major uncertainties, such as the spectral properties of the source, uncertainty in the ultraviolet and far-infrared extragalactic background light, undersampled very high energy (energy >=100 GeV) coverage, past history of gamma-ray emission, source versus observer geometry, and the jet AGN Doppler factor. The implications of these effects on the recently reported lower limits of the IGMF are thoroughly examined to conclude that the presently available data are compatible with a zero-IGMF hypothesis.

Arlen, Timothy C.; Vassilev, Vladimir V.; Weisgarber, Thomas; Wakely, Scott P.; Yusef Shafi, S.

2014-11-01

121

X-Ray Absorption by the Warm-Hot Intergalactic Medium in the Hercules Supercluster  

E-print Network

The "missing baryons", in the form of warm-hot intergalactic medium (WHIM), are expected to reside in cosmic filamentary structures that can be traced by signposts such as large-scale galaxy superstructures. The clear detection of an X-ray absorption line in the Sculptor Wall demonstrated the success of using galaxy superstructures as a signpost to search for the WHIM. Here we present an XMM-Newton Reflection Grating Spectrometer (RGS) observation of the blazar Mkn 501, located in the Hercules Supercluster. We detected an O VII K$\\alpha$ absorption line at the 98.7 % level ($2.5\\sigma$) at the redshift of the foreground Hercules Supercluster. The derived properties of the absorber are consistent with theoretical expectations of the WHIM. We discuss the implication of our detection for the search for the "missing baryons". While this detection shows again that using signposts is a very effective strategy to search for the WHIM, follow-up observations are crucial both to strengthen the statistical significance ...

Ren, Bin; Buote, David A

2014-01-01

122

FARADAY ROTATION MEASURE DUE TO THE INTERGALACTIC MAGNETIC FIELD. II. THE COSMOLOGICAL CONTRIBUTION  

SciTech Connect

We investigate the Faraday rotation measure (RM) due to the intergalactic magnetic field (IGMF) through the cosmic web up to cosmological distances, using a model IGMF based on turbulence dynamo in the large-scale structure of the universe. By stacking the IGMF and gas density data up to redshift z = 5 and taking account of the redshift distribution of polarized background radio sources against which the RM is measured, we simulate the sky map of the RM. The contribution from galaxy clusters is subtracted from the map, based on several different criteria of X-ray brightness and temperature. Our findings are as follows. The distribution of RM for radio sources of different redshifts shows that the rms value increases with redshift and saturates for z {approx}> 1. The saturated value is RM{sub rms} {approx} several rad m{sup -2}. The probability distribution function of |RM| follows the lognormal distribution. The power spectrum has a broad plateau over the angular scale of {approx}1{sup 0}-0.{sup 0}1 with a peak around {approx}0.{sup 0}15. The second-order structure function has a flat profile in the angular separation of {approx}> 0.{sup 0}2. Our results could provide useful insights for surveys to explore the IGMF with the Square Kilometer Array (SKA) and upcoming SKA pathfinders.

Akahori, Takuya [Research Institute of Basic Science, Chungnam National University, Daejeon (Korea, Republic of); Ryu, Dongsu, E-mail: akataku@canopus.cnu.ac.kr, E-mail: ryu@canopus.cnu.ac.kr [Department of Astronomy and Space Science, Chungnam National University, Daejeon (Korea, Republic of)

2011-09-10

123

The Volume Fraction of Ionized Intergalactic Gas at Redshift z=6.5  

E-print Network

The observed number density of Lyman-alpha sources implies a minimum volume of the inter-galactic medium that must be ionized, in order to allow the Lyman-alpha photons to escape attenuation. We estimate this volume by assigning to each Lyman-alpha emitter the minimum Stromgren sphere that would allow half its Lyman-alpha photons to escape. This implies a lower limit to ionized gas volume fraction of 20-50% at redshift z=6.5. This is a lower limit in two ways: First, we conservatively assume that the Lyman-alpha sources seen (at a relatively bright flux limit) are the only ones present; and second, we assume the smallest Stromgren sphere volume that will allow the photons to escape. This limit is completely independent of what ionizing photon sources produced the bubbles. Deeper Lyman-alpha surveys are possible with present technology, and can strengthen these limits by detecting a higher density of Lyman-alpha galaxies.

Sangeeta Malhotra; James Rhoads

2005-11-07

124

Scale-dependent bias in the baryonic-acoustic-oscillation-scale intergalactic neutral hydrogen  

NASA Astrophysics Data System (ADS)

I discuss fluctuations in the neutral hydrogen density of the z?2.3 intergalactic medium and show that their relation to cosmic overdensity is strongly scale dependent. This behavior arises from a linearized version of the well-known "proximity effect," in which bright sources suppress atomic hydrogen density. Using a novel, systematic and detailed linear-theory radiative-transfer calculation, I demonstrate how Hi density consequently anticorrelates with total matter density when averaged on scales exceeding the Lyman-limit mean-free path. The radiative-transfer thumbprint is highly distinctive and should be measurable in the Lyman-? forest. Effects extend to sufficiently small scales to generate significant distortion of the correlation function shape around the baryon acoustic oscillation peak, although the peak location shifts only by 1.2 percent for a mean source bias of bj=3. The distortion changes significantly with bj and other astrophysical parameters; measuring it should provide a helpful observational constraint on the nature of ionizing photon sources in the near future.

Pontzen, Andrew

2014-04-01

125

The evolving intergalactic medium - The uncollapsed baryon fraction in a cold dark matter universe  

NASA Technical Reports Server (NTRS)

The time-varying density of the intergalactic medium (IGM) is calculated by coupling detailed numerical calculations of the thermal and ionization balance and radiative transfer in a uniform IGM of H and He to the linearized equations for the growth of density fluctuations in both gases and a dark component in a cold dark matter universe. The IGM density is identified with the collapsed baryon fraction. It is found that even if the IGM is never reheated, a significant fraction of the baryons remain uncollapsed at redshifts of four. If instead the collapsed fraction releases enough ionizing radiation or thermal energy to reionize the IGM by z greater than four as required by the Gunn-Peterson (GP) constraint, the uncollapsed fraction at z of four is even higher. The known quasar distribution is insufficient to supply the ionizing radiation necessary to satisfy the GP constraint in this case and, if stars are instead responsible, a substantial metallicity must have been produced by z of four.

Shapiro, Paul R.; Giroux, Mark L.; Babul, Arif

1991-01-01

126

The Hot Inter-Galactic Medium and the Cosmic Microwave Background  

E-print Network

The physical characteristics of the Lyman-alpha forest cloud systems are combined with observations on the baryonic mass density of the Universe and constraints from primordial nucleosynthesis to set boundary conditions on the Intergalactic Medium (IGM) at the epoch of z=2.5. The Universe is considered a closed system and allowed to expand adiabatically from the epoch when QSOs first ionized the IGM (5 <= z_on <= 20). The average kinetic energy of a gas is calculated in the region where the gas transitions from relativistic to non-relativistic behavior. All of the above measurements are then used to determine the thermal history of the IGM in the redshift range 2.5 <= z <= z_on. The hot IGM is assumed to inverse Compton scatter photons from the Cosmic Microwave Background (CMBR) and consequently distort the CMBR as seen at the present epoch. The temperature of the IGM at z=2.5 and the epoch z_on are adjusted, within the constraints defined above, to give the best overall agreement with published data on the temperature of the IGM. We find that the model of the IGM proposed here does not grossly distort the CMBR, and in fact agrees quite closely with the preliminary results from the Cosmic Background Explorer (COBE) satellite. However, our model of the IGM cannot explain the observed cosmic x ray background. This paper was originally written in 1990. It was never submitted for publication.

Michael Fisher

2007-05-01

127

Search for Oxygen Emission from Warm-Hot Intergalactic Medium around A2218 with Suzaku  

SciTech Connect

We searched for redshifted O emission lines from the possible warm-hot intergalactic medium (WHIM) surrounding the cluster of galaxies A2218 at z = 0.1756 using the XIS instrument on Suzaku. This cluster is thought to have an elongated structure along the line of sight based on previous studies. We studied systematic uncertainties in the spectrum of the Galactic emission and in the soft X-ray response of the detectors due to the contamination building up on the XIS filters. We detected no significant redshifted O lines, and set a tight constraint on the intensity with upper limits for the surface brightness of O{sub VII} and O{sub VIII} lines of 1.1 x 10{sup -7} and 3.0 x 10{sup -7} photons cm{sup -2} s{sup -1} arcmin{sup -2}, respectively. These upper limits are significantly lower than the previously reported fluxes from the WHIM around other clusters of galaxies. We also discuss the prospect for the detection of the WHIM lines with Suzaku XIS in the future.

Takei, Yoh; Ohashi, Takaya; Henry, J.Patrick; Mitsuda, Kazuhisa; Fujimoto, Ryuichi; Tamura, Takayuki; Yamasaki, Noriko Y.; Hayashida, Kiyoshi; Tawa, Noriaki; Matsushita,; Bautz, Mark W.; Hughes, John P.; Madejski, Grzegorz M.; Kelley, Richard L.; Arnaud, Keith A.; /JAXA, Sagamihara /Tokyo Metropolitan U. /Inst. Astron., Honolulu /Osaka U.

2006-09-08

128

Strength of the Spontaneously Emitted Collective Aperiodic Magnetic Field Fluctuations in the Reionized Early Intergalactic Medium  

NASA Astrophysics Data System (ADS)

Nonmagnetized, fully ionized plasmas spontaneously emit aperiodic turbulent magnetic field fluctuations. Its fluctuation intensities are dominated by the contribution from a recently discovered collective, damped mode, which modifies the earlier estimate of the total magnetic field strength in a thermal nonrelativistic electron-proton plasma to |\\delta B|=24\\beta _e^{1/4}(gn_em_ec^2)^{1/2} G, where g denotes the plasma parameter and ? e the thermal electron velocity in units of the speed of light, in the case of no collisional damping. Accounting for simultaneous viscous damping reduces the estimate to |?B|eq = 2305g(nemec 2)1/2 G, depending only on the plasma parameter g and the electron density ne . For the unmagnetized intergalactic medium, immediately after the reionization onset the field strengths from this mechanism are about 6.8 × 10-13 G for no collisional damping and 1.5 × 10-16 G for viscous damping. Maximum spatial scales of 1015 cm of the emitted aperiodic fluctuations in cosmic voids are possible.

Schlickeiser, R.; Felten, T.

2013-11-01

129

A numerical model of resistive generation of intergalactic magnetic field at cosmic dawn  

E-print Network

Miniati and Bell (2011) proposed a mechanism for the generation of magnetic seeds that is based the finite resistivity of the low temperature IGM in the high redshift universe. In this model, cosmic-ray protons generated by the first generation of galaxies, escape into the intergalactic medium carrying an electric current that induces return currents, $j_t$, and associated electric fields, $\\vec E=\\eta\\vec j_t$ there. Because the resistivity, $\\eta$, depends on the IGM temperature, which is highly inhomogeneous due to adiabatic contraction and shocks produced by structure formation, a non-vanishing curl of the electric field exists which sustains the growth of magnetic field. In this contribution we have developed an approximate numerical model for this process by implementing the source terms of the resistive mechanism in the cosmological code CHARM. Our numerical estimates substantiate the earlier analysis in Miniati and Bell (2011) which found magnetic seeds between 10$^{-18}$ and 10$^{-16}$ Gauss througho...

Miniati, Francesco

2011-01-01

130

MAST Interface to Synthetic Telescopes with yt {MISTY}: Observing Simulations of the Intergalactic Medium  

NASA Astrophysics Data System (ADS)

The COS instrument has shed new light on the metal-rich, massive, multi-phase reservoirs of gas surrounding galaxies. Numerical modeling has greatly enhanced the scientific understanding of the large body of of circumgalactic medium {CGM} and intergalactic medium {IGM} observations taken with COS. These numerical models produce synthetic spectra for direct comparison against COS outputs, a useful data resource for both simulators and observers alike, yet different groups apply different methods and formats, and there is no public archive of this scientific resource. We propose to construct a uniform and public simulation-to-archive pipeline for generating, analyzing, and providing to the community such synthetic spectra. By enabling rigorous and consistent comparisons between COS data and simulations, this project will advance our detailed knowledge of the physical and chemical conditions in CGM/IGM absorbers {density, temperature, metallicity ionization, ionization process}, and of the connection between observed velocity structure and galactic inflows and outflows. The results of our pipeline will be searchable via a MAST interface allowing users to specify subsets of synthetic spectra they wish to download and analyze.

Peeples, Molly

2014-10-01

131

Gas around galaxy haloes: methodology comparisons using hydrodynamical simulations of the intergalactic medium  

E-print Network

We perform cosmological simulations of the intergalactic medium (IGM) at redshift z ~ 3 using the numerical gravity-hydrodynamics codes GADGET-3 and Enzo for the purpose of modelling the gaseous environments of galaxies. We identify haloes in the simulations using three different algorithms. Different rank orderings of the haloes by mass result, introducing a limiting factor in identifying haloes with observed galaxies. We also compare the physical properties of the gas between the two codes, focussing primarily on the gas outside the virial radius, motivated by recent HI absorption measurements of the gas around z ~ 2 - 3 galaxies. The internal dispersion velocities of the gas in the haloes have converged for a box size of 30 comoving Mpc, but the centre-of-mass peculiar velocities of the haloes have not up to a box size of 60 comoving Mpc. The density and temperature of the gas within the instantaneous turn-around radii of the haloes are adequately captured for box sizes 30 Mpc on a side, but the results ar...

Meiksin, Avery; Tittley, Eric R

2014-01-01

132

The b Distribution of the Lya Forest: Probing Cosmology and the Intergalactic Medium  

E-print Network

We investigate a method to determine the temperature-density relation of the intergalactic medium (IGM) at z~2-4 using quasar absorption line systems. Using a simple model combined with numerical simulations we show that there is a lower cutoff in the distribution of column density (NHI) and line width (b parameter). The location of this cutoff can be used to determine the temperature-density relation (under certain conditions). We describe and test an algorithm to do this. The method works as long as the amplitude of fluctuations on these scales (~100 kpc) is sufficiently large. Models with less power can mimic higher temperatures. A preliminary application is made to data from two quasar lines-of-sight, and we determine an upper limit to the temperature of the IGM. Finally, we examine the full distribution of b-parameters and show that this is completely specified by just two parameters: the temperature of the gas and the amplitude of the power spectrum. Using the temperature upper limit measured with the NHI-b cutoff method, we derive an upper limit to the amplitude of the power spectrum.

Greg L. Bryan; Marie E. Machacek

1999-06-28

133

The effect of neutrinos on the matter distribution as probed by the intergalactic medium  

NASA Astrophysics Data System (ADS)

We present a suite of full hydrodynamical cosmological simulations that quantitatively address the impact of neutrinos on the (mildly non-linear) spatial distribution of matter and in particular on the neutral hydrogen distribution in the Intergalactic Medium (IGM), which is responsible for the intervening Lyman-? absorption in quasar spectra. The free-streaming of neutrinos results in a (non-linear) scale-dependent suppression of power spectrum of the total matter distribution at scales probed by Lyman-? forest data which is larger than the linear theory prediction by about 25 % and strongly redshift dependent. By extracting a set of realistic mock quasar spectra, we quantify the effect of neutrinos on the flux probability distribution function and flux power spectrum. The differences in the matter power spectra translate into a ~ 2.5% (5%) difference in the flux power spectrum for neutrino masses with ?m? = 0.3 eV (0.6 eV). This rather small effect is difficult to detect from present Lyman-? forest data and nearly perfectly degenerate with the overall amplitude of the matter power spectrum as characterised by ?8. If the results of the numerical simulations are normalized to have the same ?8 in the initial conditions, then neutrinos produce a smaller suppression in the flux power of about 3% (5%) for ?m? = 0.6 eV (1.2 eV) when compared to a simulation without neutrinos. We present constraints on neutrino masses using the Sloan Digital Sky Survey flux power spectrum alone and find an upper limit of ?m? < 0.9 eV (2? C.L.), comparable to constraints obtained from the cosmic microwave background data or other large scale structure probes.

Viel, Matteo; Haehnelt, Martin G.; Springel, Volker

2010-06-01

134

THE INTERGALACTIC STELLAR POPULATION FROM MERGERS OF ELLIPTICAL GALAXIES WITH DARK MATTER HALOS  

SciTech Connect

We present simulations of dry-merger encounters between pairs of elliptical galaxies with dark matter halos. The aim of these simulations is to study the intergalactic (IG) stellar populations produced in both parabolic and hyperbolic encounters. We model progenitor galaxies with total-to-luminous mass ratios M{sub T} /M{sub L}= 3 and 11. The initial mass of the colliding galaxies are chosen so that M{sub 1}/M{sub 2} = 1 and 10. The model galaxies are populated by particles representing stars, as in Stanghellini et al., and dark matter. Merger remnants resulting from these encounters display a population of unbounded particles, both dark and luminous. The number of particles becoming unbounded depends on orbital configuration, with hyperbolic encounters producing a larger luminous intracluster population than parabolic encounters. Furthermore, in simulations with identical orbital parameters, a lower M{sub T} /M{sub L} of the colliding galaxies produces a larger fraction of unbounded luminous particles. For each modeled collision, the fraction of unbounded to initial stellar mass is the same in all mass bins considered, similarly to what we found previously by modeling encounters of galaxies without dark halos. The fraction of IG to total luminosity resulting from our simulations is {approx}4% and {approx}6% for dark-to-bright mass ratios of 10 and 2, respectively. These unbounded-to-total luminous fractions are down from the 17% that we had previously found in the case of no dark halos. Our results are in broad agreement with IG light observed in groups of galaxies, while the results of our previous models without dark halos better encompass observed intracluster populations. We suggest a possible formation scenario of IG stars.

Gonzalez-Garcia, A. Cesar [Departamento de Fisica Teorica, Universidad Autonoma de Madrid, 28049 Madrid (Spain); Stanghellini, Letizia [National Optical Astronomy Observatory, 950 N. Cherry Avenue, Tucson, AZ 85719 (United States); Manchado, Arturo, E-mail: c.gonzalezgarcia@uam.e [Instituto de Astrofisica de Canarias, vIa Lactea s/n, La Laguna, E-38200 Tenerife (Spain)

2010-02-20

135

Absorption in the Cosmic Web: Characterizing the Intergalactic Medium in Cosmological Filaments  

NASA Astrophysics Data System (ADS)

We propose to observe and characterize the IGM associated with cosmological filaments in a statistical manner up to redshift ~0.4. For this purpose, we have used a published cluster catalog (Hao et al. 2010) to identify massive nodes in the cosmic web. We used cluster-pairs separated by < 20 Mpc (transverse) and < 2000 km/s (along the LOS) to identify zones where filaments should reside with high probabilities. We have selected a single QSO whose sightline passess through a total of 9 independent cluster-pairs (8 of which having spectroscopic redshifts) at impact parameters <10 Mpc (7 of which at < 5 Mpc). We propose to observe the QSO with HST/COS using the G130M and G160M gratings to cover the full FUV spectral range at medium resolution (R~20000). We require observations at S/N>10 to ensure a full characterization of HI and OVI lines at column densities N~10^13 cm^-2. This setup will allow us to detect broad and shallow HI and OVI lines (if any) at the redshifts of these filaments, believed to trace portions of the warm-hot intergalactic medium (WHIM). Combining these new observations with those from our pilot study carried out in cycle 20 (ID 12958, PI Tejos), we aim to provide a firm detection of the WHIM in cosmological filaments, at the 95% confidence level. Our findings will test our understanding of galaxy formation and the role of AGN/supernova feedback by comparing them with state-of-the-art hydrodynamical simulations. We will also test the the hypothesis which states that the majority of OVI absorbers at low-z are confined within <300 kpc from galaxies (i.e. circumgalactic medium) thus not related to the WHIM (Prochaska et al. 2011; Tumlinson et al. 2011).

Tejos, Nicolas

2014-10-01

136

Characterizing the cool and warm-hot intergalactic medium in clusters at z < 0.4  

NASA Astrophysics Data System (ADS)

Dedicated surveys with HST/COS and previous UV spectrometers have revealed that present-day galaxies of essentially all mass and spectral-type harbor a substantial reservoir of cool (T~10^4K) and warm (T~10^5-10^6 K) gas in their halos, defining a circumgalactic medium (CGM) around galaxies. At much higher halo mass scales, groups and clusters exhibit a hot (T~10^6-10^7K) tenuous plasma designated the intragroup or intracluster medium (IGrM, ICM). Although these massive structures hosts up to hundreds of individual galaxies, it is unknown whether the IGrM/ICM also contains cool or warm phases. Numerical simulations offer some guidance, predicting that the outer environment is warm (T<10^6K) and recent work on Virgo reveals a cool phase close to its virial radius. Here we venture into this unexplored territory, and propose to use HST/COS spectroscopy of 6 background QSOs to search for the cool (narrow HI Lya) and the warm/highly-ionized gas (broad HI Lya and OVI) at impact parameters of ~0.2 - 3 R_200 from 11 clusters lying in the foreground. We will use both G130M and G160M gratings to cover the full FUV spectral range to simultaneosly survey HI Lya and OVI at the redshifts of the intervening structures. This first systematic study of cool and warm gas in massive, low-z halos will enable us to: (1) quantify the contribution of the warm-hot intergalactic medium (WHIM) within or near massive groups and clusters; (2) explore the signatures of tidal and ram-pressure stripping of group/cluster members; (3) search for evidence of expulsion of baryons via feedback processes; and (4) search for evidence of cold/hot accretion modes in these massive halos.

Tejos, Nicolas

2014-10-01

137

Probing Primordial Magnetic Fields with 21-cm Line Observations of the High-redshift Intergalactic Medium  

NASA Astrophysics Data System (ADS)

Coherent magnetic fields with strengths of the order of 10^(-5) G are observed on scales of individual galaxies, including the Milky Way. They are thought to be organized and maintained by a dynamo mechanism. However, the nature and origin of the seed magnetic field, required for the dynamo effect to take place, are still unknown. Here, we propose a method of probing the magnetic field in the intergalactic medium before the Epoch of Reionization through observations of redshifted 21-cm radiation of neutral hydrogen. The 21-cm line is created during the spin-flip transition between the hyperfine levels of the hydrogen ground state. The upper hyperfine level is a triplet consisting of atomic states with three different projections of the total angular momentum vector. Anisotropic 21-cm radiation, resulting from perturbations in the high-redshift IGM, unevenly populates triplet sublevels. If an atom is located in an external magnetic field, it precesses between the three states; this causes an additional anisotropy in the 21-cm radiation, which could be imprinted in the 21-cm power spectrum. In order to evaluate the effect of the magnetic field, we need to consider in full detail all mechanisms that affect the distribution of atoms in hyperfine sublevels, such as the interaction of hydrogen atoms with the 21-cm radiation, optical pumping by Lyman-alpha photons, and spin-exchange in hydrogen-hydrogen collisions. Preliminary calculations suggest that this method could be sensitive to extremely weak magnetic fields, of the order of 10^(-17) G.

Oklopcic, Antonija; Gluscevic, V.; Hirata, C. M.; Mishra, A.; Venumadhav, T. N.

2014-01-01

138

THE TEMPERATURE-DENSITY RELATION IN THE INTERGALACTIC MEDIUM AT REDSHIFT (z) = 2.4  

SciTech Connect

We present new measurements of the temperature-density (T-{rho}) relation for neutral hydrogen in the 2.0 < z < 2.8 intergalactic medium (IGM) using a sample of {approx}6000 individual H I absorbers fitted with Voigt profiles constrained in all cases by multiple Lyman series transitions. We find model-independent evidence for a positive correlation between the column density of H I (N{sub HI}) and the minimum observed velocity width of absorbers (b{sub min}). With minimal interpretation, this implies that the T-{rho} relation in the IGM is not 'inverted', contrary to many recent studies. Fitting b{sub min} as a function of N{sub HI} results in line-width-column-density dependence of the form b{sub min} = b{sub 0}(N{sub HI}/N{sub HI,0}){sup {Gamma}-1} with a minimum line width at mean density ({rho}/{rho}-bar = 1, N{sub HI,0} = 10{sup 13.6} cm{sup -2}) of b{sub 0} = 17.9 {+-} 0.2 km s{sup -1} and a power-law index of ({Gamma} - 1) = 0.15 {+-} 0.02. Using analytic arguments, these measurements imply an 'equation of state' for the IGM at (z) = 2.4 of the form T=T{sub 0} ({rho}/{rho}-bar){sup {gamma}-1} with a temperature at mean density of T{sub 0} = [1.94 {+-} 0.05] Multiplication-Sign 10{sup 4} K and a power-law index ({gamma} - 1) = 0.46 {+-} 0.05.

Rudie, Gwen C.; Steidel, Charles C. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, MS 249-17, Pasadena, CA 91125 (United States); Pettini, Max, E-mail: gwen@astro.caltech.edu [Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom)

2012-10-01

139

The Search for Diffuse Intergalactic and Circumgalactic Emission with the Cosmic Origins Spectrograph  

NASA Astrophysics Data System (ADS)

We propose to measure the emission from the gas associated with known extragalactic UV absorbers to constrain the physical conditions and physical size of the gas. This will be accomplished through the co-addition of numerous { >75} COS QSO lines of sight, shifted in wavelength so the absorbers are coincident. The COS aperture admits light from the surrounding sky that can be separated from the point source signal to measure diffuse emission. No single observation has the sensitivity to detect these signals, but large coadditions can, unless the gas is extremely low density. We have custom extraction procedures for this project, and our intimate understanding of CalCOS, the optical performance of COS, and FUV detector systematics {scattered light, dark rate, gain sag, detector walk, etc.}, are essential to its success. Our team consists of COS IDT members, the COS PI and optical designer of COS, STScI COS calibration team members, and IGM/CGM experts. We will look for emission from HI Lya 1216A and OVI 1032A. Emission and absorption measures on a unique line of sight would normally allow for a determination of the volume density and physical size. However, since this study will produce a net emission measure from many co-added lines of sight, it will provide an average, but unique, physical insight into the nature of the gas, and in particular, indicate what fraction of this previously undetected gas is circumgalactic versus truly intergalactic in nature. We will also search for extended diffuse emission from gas not associated with absorption systems. We will also assist in testing and enabling many cutting edge additions to CalCOS which will benefit future COS users.

Penton, Steven

2014-10-01

140

COSMOLOGICAL SIMULATIONS OF INTERGALACTIC MEDIUM EVOLUTION. I. TEST OF THE SUBGRID CHEMICAL ENRICHMENT MODEL  

SciTech Connect

We present a one-zone galactic chemical enrichment model that takes into account the contribution of stellar winds from massive stars under the effect of rotation, Type II supernovae, hypernovae, stellar winds from low- and intermediate-mass stars, and Type Ia supernovae. This enrichment model will be implemented in a galactic model designed to be used as a subgrid treatment for galaxy evolution and outflow generation in large-scale cosmological simulations, in order to study the evolution of the intergalactic medium. We test our enrichment prescription by comparing its predictions with the metallicity distribution function and the abundance patterns of 14 chemical elements observed in the Milky Way stars. To do so, we combine the effect of many stellar populations created from the star formation history of the Galaxy in the solar neighborhood. For each stellar population, we keep track of its specific mass, initial metallicity, and age. We follow the time evolution of every population in order to respect the time delay between the various stellar phases. Our model is able to reproduce the observed abundances of C, O, Na, Mg, Al, S, and Ca. For Si, Cr, Mn, Ni, Cu, and Zn, the fits are still reasonable, but improvements are needed. We marginally reproduce the nitrogen abundance in very low metallicity stars. Overall, our results are consistent with the predicted abundance ratios seen in previous studies of the enrichment history of the Milky Way. We have demonstrated that our semi-analytic one-zone model, which cannot deal with spatial information such as the metallicity gradient, can nevertheless successfully reproduce the global Galactic enrichment evolution obtained by more complex models, at a fraction of the computational cost. This model is therefore suitable for a subgrid treatment of chemical enrichment in large-scale cosmological simulations.

Côté, Benoit; Martel, Hugo; Drissen, Laurent [Département de physique, de Génie Physique et d'Optique, Université Laval, Québec, QC G1V 0A6 (Canada)

2013-11-10

141

THE OPACITY OF THE INTERGALACTIC MEDIUM DURING REIONIZATION: RESOLVING SMALL-SCALE STRUCTURE  

SciTech Connect

Early in the reionization process, the intergalactic medium (IGM) would have been quite inhomogeneous on small scales, due to the low Jeans mass in the neutral IGM and the hierarchical growth of structure in a cold dark matter universe. This small-scale structure acted as an important sink during the epoch of reionization, impeding the progress of the ionization fronts that swept out from the first sources of ionizing radiation. Here we present results of high-resolution cosmological hydrodynamics simulations that resolve the cosmological Jeans mass of the neutral IGM in representative volumes several Mpc across. The adiabatic hydrodynamics we follow are appropriate in an unheated IGM, before the gas has had a chance to respond to the photoionization heating. Our focus is determination of the resolution required in cosmological simulations in order to sufficiently sample and resolve small-scale structure regulating the opacity of an unheated IGM. We find that a dark matter particle mass of m {sub dm} {approx}< 50 M {sub Sun} and box size of L {approx}> 1 Mpc are required. With our converged results we show how the mean free path of ionizing radiation and clumping factor of ionized hydrogen depend on the ultraviolet background flux and redshift. We find, for example at z = 10, clumping factors typically of 10-20 for an ionization rate of {Gamma} {approx} (0.3-3) Multiplication-Sign 10{sup -12} s{sup -1}, with corresponding mean free paths of {approx}3-15 Mpc, extending previous work on the evolving mean free path to considerably smaller scales and earlier times.

Emberson, J. D.; Thomas, Rajat M.; Alvarez, Marcelo A., E-mail: emberson@astro.utoronto.ca [Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George St., Toronto, ON M5S 3H8 (Canada)

2013-02-15

142

The significance of the Hansen Ideal space frame  

NASA Astrophysics Data System (ADS)

Known and unknown properties of Hansen Ideal coordinates are summarized. It is shown that the ideal space frame is a general and necessary component of basic celestial mechanics and astrodynamics, as well as of any theory of motion. A typical consequence is the intimate correlation of the Hansen frame with the Lagrange constraint within the method of the variation of the parameters. The use of observations in the ideal frame may allow conclusions on the intergalactic fundamental coordinate system.

Jochim, E. F. M.

2012-10-01

143

Physical Properties and Baryonic Content of Low-Redshift Intergalactic Ly? and O VI Absorption Line Systems: The PG 1116+215 Sight Line  

NASA Astrophysics Data System (ADS)

We present Hubble Space Telescope and Far Ultraviolet Spectroscopic Explorer observations of the intergalactic absorption toward QSO PG 1116+215 in the 900-3000 Å spectral region. We detect 25 Ly? absorbers along the sight line at rest-frame equivalent widths Wr>30 mÅ, yielding (dN/dz)Ly?=166+/-20 over an unblocked redshift path ?zLy?=0.150. Two additional weak Ly? absorbers with Wr~15-20 mÅ are also present. Eight of the Ly? absorbers have large line widths (b>~40 km s-1). The detection of narrow O VI absorption in the broad Ly? absorber at z=0.06244 supports the idea that the Ly? profile is thermally broadened in gas with T>105 K. We find dN/dz~53 for broad Ly? absorbers with Wr>~30 mÅ and b>=40 km s-1. This number drops to dN/dz~40 if the line widths are restricted to 40<=b<=100 km s-1. If the broad Ly? lines are dominated by thermal broadening in hot gas, the amount of baryonic material in these absorbers is enormous, perhaps as much as half the baryonic mass in the low-redshift universe. We detect O VI absorption in several of the Ly? clouds along the sight line. Two detections at z=0.13847 and z=0.16548 are confirmed by the presence of other ions at these redshifts (e.g., C II-III, N II-III, N V, O I, O VI, and Si II-IV), while the detections at z=0.04125, 0.05895, 0.05928, and 0.06244 are based upon the Ly? and O VI detections alone. We find (dN/dz)OVI~18 for O VI absorbers with Wr>50 mÅ toward PG 1116+215. The information available for 13 low-redshift O VI absorbers with Wr>=50 mÅ along six sight lines yields (dN/dz)OVI~13 and ?b(OVI)>~0.0022h-175, assuming a metallicity of 0.1 solar and an O VI ionization fraction fOVI<=0.2. The properties and prevalence of low-redshift O VI absorbers suggest that they too may be a substantial baryon repository, perhaps containing as much mass as stars and gas inside galaxies. The redshifts of the O VI absorbers are highly correlated with the redshifts of galaxies along the PG 1116+215 sight line, though few of the absorbers lie closer than ~600 h-175 to any single galaxy. We analyze the kinematics and ionization of the metal-line systems along this sight line and discuss the implications of these observations for understanding the physical conditions and baryonic content of intergalactic matter in the low-redshift universe. Based on observations obtained with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Based on observations obtained with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer. FUSE is operated for NASA by the Johns Hopkins University under NASA contract NAS5-32985.

Sembach, Kenneth R.; Tripp, Todd M.; Savage, Blair D.; Richter, Philipp

2004-12-01

144

The Faint End of the Quasar Luminosity Function at z ~ 4: Implications for Ionization of the Intergalactic Medium and Cosmic Downsizing  

NASA Astrophysics Data System (ADS)

We present an updated determination of the z ~ 4 QSO luminosity function (QLF), improving the quality of the determination of the faint end of the QLF presented by Glikman et al. (2010). We have observed an additional 43 candidates from our survey sample, yielding one additional QSO at z = 4.23 and increasing the completeness of our spectroscopic follow-up to 48% for candidates brighter than R = 24 over our survey area of 3.76 deg2. We study the effect of using K-corrections to compute the rest-frame absolute magnitude at 1450 Å compared with measuring M 1450 directly from the object spectra. We find a luminosity-dependent bias: template-based K-corrections overestimate the luminosity of low-luminosity QSOs, likely due to their reliance on templates derived from higher luminosity QSOs. Combining our sample with bright quasars from the Sloan Digital Sky Survey and using spectrum-based M 1450 for all the quasars, we fit a double power law to the binned QLF. Our best fit has a bright-end slope, ? = 3.3 ± 0.2, and faint-end slope, ? = 1.6+0.8 -0.6. Our new data revise the faint-end slope of the QLF down to flatter values similar to those measured at z ~ 3. The break luminosity, though poorly constrained, is at M* = -24.1+0.7 -1.9, approximately 1-1.5 mag fainter than at z ~ 3. This QLF implies that QSOs account for about half the radiation needed to ionize the intergalactic medium at these redshifts. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

Glikman, Eilat; Djorgovski, S. G.; Stern, Daniel; Dey, Arjun; Jannuzi, Buell T.; Lee, Kyoung-Soo

2011-02-01

145

The contribution of the warm-hot intergalactic medium to the cosmic microwave background anisotropies via the Sunyaev-Zeldovich effect  

NASA Astrophysics Data System (ADS)

Cosmological hydrodynamical simulations predict that a large fraction of all baryons reside within mildly non-linear structures with temperatures in the range 105-107 K. As the gas is highly ionized, it could be detected by the temperature anisotropies generated on the cosmic microwave background radiation. We refine our previous estimates of the thermal Sunyaev-Zeldovich effect by introducing a non-polytropic equation of state to model the temperature distribution of the shock-heated gas derived from temperature-density phase diagrams of different hydrodynamical simulations. Depending on the specific model, the Comptonization parameter varies in the range 10-7 ? yc ? 2 × 10-6, compatible with the Far-Infrared Absolute Spectrophotometer upper limit. This amplitude is in agreement with a simple toy model constructed to estimate the average effect induced by filaments of the ionized gas. Using the log-normal probability density function, we calculate the correlation function and the power spectrum of the temperature anisotropies generated by the warm-hot intergalactic medium filaments. For a wide range of the parameter space, the maximum amplitude of the radiation power spectrum is (? + 1)?C?/2? = 0.7-70 (?K)2 at ? ? 200-500. This amplitude scales with baryon density, Hubble constant and the amplitude of the matter power spectrum ?8 as [(? + 1)?C?]max/2???2.68(?b h)2. Since the thermal Sunyaev-Zeldovich effect has a specific frequency dependence, we analyse the possibility of detecting this component with the forthcoming Planck data.

Suárez-Velásquez, I. F.; Mücket, J. P.; Atrio-Barandela, F.

2013-05-01

146

THE BARYON CENSUS IN A MULTIPHASE INTERGALACTIC MEDIUM: 30% OF THE BARYONS MAY STILL BE MISSING  

SciTech Connect

Although galaxies, groups, and clusters contain {approx}10% of the baryons, many more reside in the photoionized and shocked-heated intergalactic medium (IGM) and in the circumgalactic medium (CGM). We update the baryon census in the (H I) Ly{alpha} forest and warm-hot IGM (WHIM) at 10{sup 5-6} K traced by O VI {lambda}1032, 1038 absorption. From Enzo cosmological simulations of heating, cooling, and metal transport, we improve the H I and O VI baryon surveys using spatially averaged corrections for metallicity (Z/Z {sub Sun }) and ionization fractions (f {sub HI}, f {sub OVI}). Statistically, the O VI correction product correlates with column density, (Z/Z {sub Sun })f {sub OVI} Almost-Equal-To (0.015)(N {sub OVI}/10{sup 14} cm{sup -2}){sup 0.70}, with an N {sub OVI}-weighted mean of 0.01, which doubles previous estimates of WHIM baryon content. We also update the Ly{alpha} forest contribution to baryon density out to z = 0.4, correcting for the (1 + z){sup 3} increase in absorber density, the (1 + z){sup 4.4} rise in photoionizing background, and cosmological proper length dl/dz. We find substantial baryon fractions in the photoionized Ly{alpha} forest (28% {+-} 11%) and WHIM traced by O VI and broad-Ly{alpha} absorbers (25% {+-} 8%). The collapsed phase (galaxies, groups, clusters, CGM) contains 18% {+-} 4%, leaving an apparent baryon shortfall of 29% {+-} 13%. Our simulations suggest that {approx}15% reside in hotter WHIM (T {>=} 10{sup 6} K). Additional baryons could be detected in weaker Ly{alpha} and O VI absorbers. Further progress requires higher-precision baryon surveys of weak absorbers, down to minimum column densities N {sub HI} {>=} 10{sup 12.0} cm{sup -2}, N {sub OVI} {>=} 10{sup 12.5} cm{sup -2}, N {sub OVII} {>=} 10{sup 14.5} cm{sup -2}, using high signal-to-noise data from high-resolution UV and X-ray spectrographs.

Shull, J. Michael; Danforth, Charles W.; Smith, Britton D., E-mail: michael.shull@colorado.edu, E-mail: smit1685@msu.edu, E-mail: charles.danforth@colorado.edu [CASA, Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309 (United States)

2012-11-01

147

ANISOTROPIC GALACTIC OUTFLOWS AND ENRICHMENT OF THE INTERGALACTIC MEDIUM. II. NUMERICAL SIMULATIONS  

SciTech Connect

We combine an analytic model for anisotropic outflows and galaxy formation with numerical simulations of large-scale structure and halo formation to study the impact of galactic outflows on the evolution of the intergalactic medium (IGM). Using this algorithm, we have simulated the evolution of a comoving volume of size (15 Mpc){sup 3} in the {Lambda}CDM universe. Using an N-body simulation starting at redshift z = 24, we follow the formation of galaxies and simulate the galactic outflows produced by these galaxies. Outflows are modeled as bipolar cones with opening angle {alpha}, which expand along the direction of least resistance. We consider five opening angles: {alpha} = 60{sup 0}, 90{sup 0}, 120{sup 0}, 150{sup 0}, and 180{sup 0} (isotropic outflows). We also consider the effect of photoionization suppression of galaxy formation by reionization at redshift z = 6. Anisotropic outflows travel preferentially into low-density regions, away from cosmological structures (filaments and pancakes) where galaxies form. These anisotropic outflows are less likely to overlap with one another than isotropic ones. They are also less likely to hit pre-galactic collapsing halos and strip them of their gas, preventing a galaxy from forming. Going from 180{sup 0} to 60{sup 0}, the number of galaxies that actually form doubles, producing twice as many outflows, and these outflows overlap to a lesser extent. As a result, the metal volume filling factor of the IGM goes from 8% for isotropic outflows up to 28% for anisotropic ones. High-density regions are more efficiently enriched than low-density ones ({approx}80% compared to {approx}20% by volume), even though most enriched regions are low densities. Increasing the anisotropy of outflows increases the extent of enrichment at all densities, low and high. This is in part because anisotropic outflows are more numerous. When this effect is factored out, we find that the probability a galaxy will enrich systems at densities up to 10 {rho}-bar is higher for increasingly anisotropic outflows. This is interpreted as an effect of the dynamical evolution of the IGM. Anisotropic outflows expand preferentially into underdense gas, but that gas can later accrete onto overdense structures. The inclusion of photoionization greatly reduces the formation of low-mass galaxies at redshifts z < 3. The result is a decline in the physical extent of galactic outflows after z = 3 as accretion overwhelms the expansion of new outflows and reduces feedback in underdense regions.

Pinsonneault, Steeve; Martel, Hugo [Departement de physique, de genie physique et d'optique, Universite Laval, Quebec, QC G1K 7P4 (Canada); Pieri, Matthew M. [Department of Astronomy, Ohio State University, Columbus, OH 43210 (United States)

2010-12-20

148

High redshift in greatness scale caused by Interstellar and Intergalactic Media  

NASA Astrophysics Data System (ADS)

According to QFT it is deduced that the gravitation is likely to originate from the polarization effect of Dirac vacuum fluctuation (Chen Shao-Guang, Nuovo Cimento B 104, 611, 1989) . In Dirac vacuum the lowest-energy virtual neutrinos u possess most number, which exert isotropic colliding pressure to isolated mass-point A (m ) , the net force on A is zero. For another masspoint B (M ) near A to obstruct u flux shooting to A, the u number along the line connecting A and B will decrease and destroy isotropic distribution of u, which leads to not only the change in momentum P (produces net u flux and net force Fp) but also the change in energy E or rest mass m (produces net force Fm). From the definition of force: F = Fp + Fm, Fp = m ( d v / d t ) , Fm = v (d m / d t ) (1) on A (or B) net force F Q (quasi-Casimir pressure of weak interaction) is: F Q = Fp + Fm = - K (m M /r 2 ) ( r/r ) + (v/c ) (2) According to the change in masses caused by Bondi's inductive transfer of energy in GR (H. Bondi, Proc. R. Soc. London A 427, 249, 1990) and Eq. (1) a new gravitational formula is deduced: F G = Fp + Fm = - G (m M /r 2 ) (r/r ) + (v/c ) (3) F G is equivalent to Einstein's equation, then we can solve the multi-bodies gravitational problems. K calculated from the weak-electromagnetism unified theory (W-EUT) has the same order of magnitude as experimental gravitational constant G. F G and F Q as a bridge joins QFT and GR. If K = G, gravitational theory would be merged into W-EUT. The gravitational laws predicted by F G and F Q are identical except that F Q has quantum effects but F G has not, F G has Lense- Thirring effect but FQ has not. Because Fp • d s= 0, the relative loss rate of total energy of A in a period T of circular motion around B calculated from Fm = - G (m M /r 2 ) (v/c ) is: lr = F m d s / m c 2 = - 4 (pi) 2 G M / c 3 T (4) Eq.(4) is a typical dipole radiation formula and approves directly Will's conjecture (C.M.Will, Phys. Rep. 113, 345,1984) . A gravitational wave of dipole radiation will be produced from the change in masses of A and B caused by the nonlinearity of Einstein's equation or by mass renormalization of QFT. The change in period of energy loss of pulsar binary PSR1913+16 calculated with Eq. (4) is consistent with the observation value of Taylar et al. The change in mass of photons on the way calculated from F Q or F G is the redshift ratio: Red=(E-Ei)/Ei= F G ds / Ei = - 4 GM / c 2 D (5) Where E is actual energy, Ei is in inertial system energy, which is just the metrical definition of redshift. The redshift ratio of Eq. (5) is numerically equal to the deflection ratio of GR, which is consistent with relativistic combination of energy and momentum. When light sweep the sun once maximal redshift ratio is 4GM / c2 R =-8×10-6 . When photons pass through greatness scale interstellar and intergalactic media high gravitational redshift will arises, e.g., if universal luminosity mass density ( about 10-31 g cm -3 )is entirely constituted by stars with M in homogeneous distribution, the distance of two stars is about 800 PC, maximal redshift constant is 3000 km s-1 / MPC, average value is 62.5 km s-1 / MPC ( near the observational Hubble's constant ), which will influence astronomical distance estimated by redshift and many astrophysical parameter.

Chen, Shao-Guang

149

Reionization in a cold dark matter universe: The feedback of galaxy formation on the intergalactic medium  

NASA Technical Reports Server (NTRS)

We study the coupled evolution of the intergalactic medium (IGM) and the emerging structure in the universe in the context of the cold dark matter (CDM) model, with a special focus on the consequences of imposing reionization and the Gunn-Peterson constraint as a boundary condition on the model. We have calculated the time-varying density of the IGM by coupling our detailed, numerical calculations of the thermal and ionization balance and radiative transfer in a uniform, spatially averaged IGM of H and He, including the mean opacity of an evolving distribution of gas clumps which correspond to quasar absorption line clouds, to the linearized equations for the growth of density fluctuations in both the gaseous and dark matter components in a CDM universe. We use the linear growth equations to identify the fraction of the gas which must have collapsed out at each epoch, an approach similar in spirit to the so-called Press-Schechter formalism. We identify the IGM density with the uncollapsed baryon fraction. The collapsed fraction is postulated to be a source of energy injection into the IGM, by radiation or bulk hydrodynamical heating (e.g., via shocks) or both, at a rate which is marginally enough to satisfy the Gunn-Peterson constraint at z less than 5. Our results include the following: (1) We find that the IGM in a CDM model must have contained a substantial fraction of the total baryon density of the universe both during and after its reionization epoch. (2) As a result, our previous conclusion that the observed Quasi-Stellar Objects (QSOs) at high redshift are not sufficient to ionize the IGM enough to satisfy the Gunn-Peterson constraint is confirmed. (3) We predict a detectable He II Gunn-Peterson effect at 304(1 + z) A in the spectra of quasars at a range of redshift z greater than or approx. 3, depending on the nature of the sources of IGM reionization. (4) We find, moreover, that a CDM model with high bias parameter b (i.e., b greater than or approx. 2) cannot account for the baryon content of the universe at z approximately 3 observed in quasar absorption line gas unless Omega (sub B) significantly exceeds the maximum value allowed by big bang nucleocynthesis. (5) For a CDM model with bias parameter within the allowed range of (lower) values, the lower limit to Omega(sub B) imposed by big bang nucleosynthesis (Omega(sub B) h(sup 2) greater than or equal to 0.01) combines with our results to yield the minimum IGM density for the CDM fodel. For CDM with b = 1 (Cosmic Background Explorer (COBE) normalization), we find Omega(sub IGM)(sup min) (z approximately 4) approx. equal 0.02-0.03, and Omega(sub IGM)(sup min)(z approximately 0) approx. equal 0.005-0.03, depending upon the nature of the sources of IGM reionization. (6) In general, we find that self-consistent reionization of the IGM by the collapsed baryon fraction has a strong effect on the rate of collapse. (7) As a further example, we show that the feedback effect on the IGM of energy release by the collapsed baryon fraction may explain the slow evolution of the observed comoving QSO number density between z = 5 and z = 2, followed by the sharp decline after z = 2.

Shapiro, Paul R.; Giroux, Mark L.; Babul, Arif

1994-01-01

150

TURBULENT MOLECULAR GAS AND STAR FORMATION IN THE SHOCKED INTERGALACTIC MEDIUM OF STEPHAN'S QUINTET  

SciTech Connect

The Stephan's Quintet (hereafter SQ) is a template source to study the impact of galaxies interaction on the physical state and energetics of their gas. We report on IRAM single-dish CO observations of the SQ compact group of galaxies. These observations follow up the Spitzer discovery of bright mid-IR H{sub 2} rotational line emission (L(H{sub 2}) Almost-Equal-To 10{sup 35} W) from warm (10{sup 2-3} K) molecular gas, associated with a 30 kpc long shock between a galaxy, NGC 7318b, and NGC 7319's tidal arm. We detect CO(1-0), (2-1) and (3-2) line emission in the inter-galactic medium (IGM) with complex profiles, spanning a velocity range of Almost-Equal-To 1000 km s{sup -1}. The spectra exhibit the pre-shock recession velocities of the two colliding gas systems (5700 and 6700 km s{sup -1}), but also intermediate velocities. This shows that much of the molecular gas has formed out of diffuse gas accelerated by the galaxy-tidal arm collision. CO emission is also detected in a bridge feature that connects the shock to the Seyfert member of the group, NGC 7319, and in the northern star forming region, SQ-A, where a new velocity component is identified at 6900 km s{sup -1}, in addition to the two velocity components already known. Assuming a Galactic CO(1-0) emission to H{sub 2} mass conversion factor, a total H{sub 2} mass of Almost-Equal-To 5 Multiplication-Sign 10{sup 9} M{sub Sun} is detected in the shock. The ratio between the warm H{sub 2} mass derived from Spitzer spectroscopy, and the H{sub 2} mass derived from CO fluxes is Almost-Equal-To 0.3 in the IGM of SQ, which is 10--100 times higher than in star-forming galaxies. The molecular gas carries a large fraction of the gas kinetic energy involved in the collision, meaning that this energy has not been thermalized yet. The kinetic energy of the H{sub 2} gas derived from CO observations is comparable to that of the warm H{sub 2} gas from Spitzer spectroscopy, and a factor Almost-Equal-To 5 greater than the thermal energy of the hot plasma heated by the collision. In the shock and bridge regions, the ratio of the PAH-to-CO surface luminosities, commonly used to measure the star formation efficiency of the H{sub 2} gas, is lower (up to a factor 75) than the observed values in star-forming galaxies. We suggest that turbulence fed by the galaxy-tidal arm collision maintains a high heating rate within the H{sub 2} gas. This interpretation implies that the velocity dispersion on the scale of giant molecular clouds in SQ is one order of magnitude larger than the Galactic value. The high amplitude of turbulence may explain why this gas is not forming stars efficiently.

Guillard, P.; Cluver, M. E.; Lisenfeld, U.; Ogle, P. M. [Spitzer Science Center (SSC), California Institute of Technology, MC 220-6, Pasadena, CA 91125 (United States); Boulanger, F.; Pineau des Forets, G. [Institut d'Astrophysique Spatiale (IAS), UMR 8617, CNRS, Universite Paris-Sud 11, Batiment 121, 91405 Orsay Cedex (France); Falgarone, E.; Gusdorf, A. [ENS, LERMA, UMR 8112, CNRS, Observatoire de Paris, 24 rue Lhomond 75005 Paris (France); Appleton, P. N. [NASAHerschel Science Center (NHSC), California Institute of Technology, Mail code 100-22, Pasadena, CA 91125 (United States); Duc, P.-A. [AIM, Unite Mixte de Recherche CEA-CNRS, Universite Paris VII, UMR 7158 (France); Xu, C. K. [Infrared Processing and Analysis Center (IPAC), JPL, Pasadena, CA 91109 (United States)

2012-04-20

151

Where Am I? My Place in Time and Space. First Grade Activity. Schools of California Online Resources for Education (SCORE): Connecting California's Classrooms to the World.  

ERIC Educational Resources Information Center

In this activity, first grade students learn their addresses and their places in space. Each student pretends they are a student in Ms. Frizzle's class and are to help the class figure out how to get home. The students create their own intergalactic address book, so that on their next trip into the universe they will have a map to guide them back…

Boston, Jaime

152

High-Redshift Intergalactic C IV Abundance Measurements from the Near-Infrared Spectra of Two z ~ 6 QSOs  

NASA Astrophysics Data System (ADS)

New measurements of the z~6 intergalactic C IV abundance are presented, using moderate-resolution IR spectra of two QSOs taken with GNIRS on Gemini-South. These data were systematically searched for high-redshift C IV absorption lines, using objective selection criteria. Comprehensive tests were performed to quantify sample incompleteness, as well as the rate of false-positive C IV identifications. The trend of constant ?CIV(z) observed at z~2-5 appears to continue to z~6, the highest observed redshift. The C IV sample is also consistent with the redshift-invariant form of the C IV column density distribution reported by Songaila at lower redshift, although with fairly large uncertainties due to a smaller sample size and noisier infrared data. The constant value of ?CIV does not necessarily imply that the IGM was infused with an early metallicity ``floor,'' but the presence of early C IV does indicate that heavy-element enrichment began <~1 Gyr after the big bang. The lack of a decline in ?CIV at high redshift may indicate that integrated C IV measurements are sensitive to the instantaneous rate of feedback from galaxy formation at each epoch. Alternatively, it could result from a balance in the evolution of the intergalactic gas density, ionization conditions, and heavy-element abundance over time. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Particle Physics and Astronomy Research Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), CNPq (Brazil), and CONICET (Argentina).

Simcoe, Robert A.

2006-12-01

153

Small Scale Structure at High Redshift: III. The Clumpiness of the Intergalactic Medium on Sub-kpc Scales  

E-print Network

Spectra from the Keck HIRES instrument of the Lyman alpha forests in the lines of sight to the A and C components of the gravitationally lensed QSO Q1422+231 were used to investigate the structure of the intergalactic medium at mean redshift z = 3.3 on sub-kpc scales. We measured the cross-correlation amplitude between the two Lyman alpha forests for a mean transverse separation of 120 pc, and computed the RMS column density and velocity differences between individual absorption systems seen in both lines of sight. The RMS differences between the velocity centroids of the Lyman alpha forest lines were found to be less than about 400 m/s, for unsaturated absorption lines with column densities in the range 12intergalactic medium was used to obtain an upper limit on the RMS fluctuations of the baryonic density field. The fraction of the absorption lines that are different across the lines of sight was used to determine the filling factor of the universe for gas which has suffered recent hydrodynamic disturbances. We thereby derived upper limits on the filling factor of galactic outflows at high redshift. Short-lived, short-range ancient winds are essentially unconstrained by this method but strong winds blowing for a substantial fraction of a Hubble time (at z = 3.3) appear to fill less than 20 percent of the volume of the universe.

Michael Rauch; Wallace L. W. Sargent; Thomas A. Barlow; Robert F. Carswell

2001-07-27

154

The Properties of Low Redshift Intergalactic O VI Absorbers Determined from High S/N Observations of 14 QSOs with the Cosmic Origins Spectrograph  

NASA Astrophysics Data System (ADS)

We report on the observed properties of the plasma revealed through high signal-to-noise observations of 54 intervening O VI absorption systems containing 85 O VI and 133 H I components in a blind survey of 14 QSOs observed at ~18 km s-1 resolution with the Cosmic Origins Spectrograph over a redshift path of 3.52 at z < 0.5. Simple systems with one or two H I components and one O VI component comprise 50% of the systems. For a sample of 45 well-aligned absorption components where the temperature can be estimated, we find evidence for cool photoionized gas in 31 (69%) and warm gas (6 > log T > 5) in 14 (31%) of the components. The total hydrogen content of the 14 warm components can be estimated from the temperature and the measured value of log N(H I). The very large implied values of log N(H) range from 18.38 to 20.38 with a median of 19.35. The metallicity, [O/H], in the 6 warm components with log T > 5.45 ranges from -1.93 to 0.03 with a median value of -1.0 dex. Ground-based galaxy redshift studies reveal that most of the absorbers we detect sample gas in the intergalactic medium extending 200 to 600 kpc beyond the closest associated galaxy. For the warm aligned O VI absorbers, we estimate ?b(O VI)Warm = 0.0019 ± 0.0005 which corresponds to (4.1 ± 1.1)% of the baryons at low z. The warm plasma traced by the aligned O VI and H I absorption contains nearly as many baryons as are found in galaxies. Based on observations obtained with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS5-2655, and the NASA-CNES/ESA Far-Ultraviolet Spectroscopic Explorer mission operated by Johns Hopkins University, supported by NASA contract NAS 05-32885.

Savage, B. D.; Kim, T.-S.; Wakker, B. P.; Keeney, B.; Shull, J. M.; Stocke, J. T.; Green, J. C.

2014-05-01

155

THE LOW-REDSHIFT INTERGALACTIC MEDIUM AS SEEN IN ARCHIVAL LEGACY HST/STIS AND FUSE DATA  

SciTech Connect

We present a comprehensive catalog of ultraviolet (HST/STIS and FUSE) absorbers in the low-redshift intergalactic medium (IGM) at z < 0.4. The catalog draws from much of the extensive literature on IGM absorption and reconciles discrepancies among several previous catalogs through a critical evaluation of all reported absorption features in light of new HST/COS data. We report on 746 H I absorbers down to a rest-frame equivalent width of 12 mA over a maximum redshift path length {Delta}z = 5.38. We also confirm 111 O VI absorbers, 29 C IV absorbers, and numerous absorption lines due to other metal ions. We characterize the bivariate distribution of absorbers in redshift and column density as a power law, {partial_derivative}{sup 2}N/{partial_derivative}z{partial_derivative}N) {proportional_to} N{sup -{beta}}, where {beta} = 2.08 {+-} 0.12 for O VI and {beta} = 1.68 {+-} 0.03 for H I. Utilizing a more sophisticated accounting technique than past work, our catalog accounts for {approx}43% of the baryons: 24% {+-} 2% in the photoionized Ly{alpha} forest and 19% {+-} 2% in the warm-hot IGM as traced by O VI. We discuss the large systematic effects of various assumed metallicities and ionization states on these calculations, and we implement recent simulation results in our estimates.

Tilton, Evan M.; Danforth, Charles W.; Michael Shull, J. [CASA, Department of Astrophysical and Planetary Sciences, University of Colorado, 389-UCB, Boulder, CO 80309 (United States); Ross, Teresa L., E-mail: evan.tilton@colorado.edu, E-mail: charles.danforth@colorado.edu, E-mail: michael.shull@colorado.edu, E-mail: rosst@nmsu.edu [Department of Astronomy, New Mexico State University, Las Cruces, NM 88003 (United States)

2012-11-10

156

The M_BH - T relation for a black hole in thermodynamic equilibrium with the surrounding intergalactic medium  

E-print Network

I consider a toy model of self-regulated black hole accretion. The black hole grows through Bondi accretion and a fraction of the accretion power is distributed as thermal feedback into the surrounding gas. The gas expands or contracts until AGN heating and radiative cooling balance each other. The balance of heating and cooling is used to determine a quasi-equilibrium temperature at which the black hole accretes in self-regulated equilibrium with the surrounding intergalactic medium. This temperature grows with the black hole mass. The temperature increase is very steep around a critical black hole mass due to the shape of the cooling function. The quasi-equilibrium temperature cannot exceed the virial temperature or the AGN will drive a thermal wind. This limits the black hole mass to a maximum value determined by the depth of the potential well. In the regime in which cooling is dominated by bremsstrahlung, this model determines a relation between black hole mass and halo characteristic velocity of the form M_BH ~ v^4. The predictions of the model are consistent with the observed black hole mass -- bulge velocity dispersion relation.

Andrea Cattaneo

2006-01-19

157

The Nature of the Warm/Hot Intergalactic Medium. I. Numerical Methods, Convergence, and O VI Absorption  

NASA Astrophysics Data System (ADS)

We perform a series of cosmological simulations using Enzo, an Eulerian adaptive-mesh refinement, N-body + hydrodynamical code, applied to study the warm/hot intergalactic medium (WHIM). The WHIM may be an important component of the baryons missing observationally at low redshift. We investigate the dependence of the global star formation rate and mass fraction in various baryonic phases on spatial resolution and methods of incorporating stellar feedback. Although both resolution and feedback significantly affect the total mass in the WHIM, all of our simulations find that the WHIM fraction peaks at z ~ 0.5, declining to 35%-40% at z = 0. We construct samples of synthetic O VI absorption lines from our highest-resolution simulations, using several models of oxygen ionization balance. Models that include both collisional ionization and photoionization provide excellent fits to the observed number density of absorbers per unit redshift over the full range of column densities (1013 cm-2 <~ N O VI <~ 1015 cm-2). Models that include only collisional ionization provide better fits for high column density absorbers (N O VI >~ 1014 cm-2). The distribution of O VI in density and temperature exhibits two populations: one at T ~ 105.5 K (collisionally ionized, 55% of total O VI) and one at T ~ 104.5 K (photoionized, 37%) with the remainder located in dense gas near galaxies. While not a perfect tracer of hot gas, O VI provides an important tool for a WHIM baryon census.

Smith, Britton D.; Hallman, Eric J.; Shull, J. Michael; O'Shea, Brian W.

2011-04-01

158

The thermal history of the intergalactic medium down to redshift z = 1.5: a new curvature measurement  

NASA Astrophysics Data System (ADS)

According to the photoheating model of the intergalactic medium (IGM), He II reionization is expected to affect its thermal evolution. Evidence for additional energy injection into the IGM has been found at 3 ? z ? 4, though the evidence for the subsequent fall-off below z ˜ 2.8 is weaker and depends on the slope of the temperature-density relation, ?. Here we present, for the first time, an extension of the IGM temperature measurements down to the atmospheric cut-off of the H I Lyman-? (Ly?) forest at z ? 1.5. Applying the curvature method on a sample of 60 Ultraviolet and Visual Echelle Spectrograph (UVES) spectra we investigated the thermal history of the IGM at z < 3 with precision comparable to the higher redshift results. We find that the temperature of the cosmic gas traced by the Ly? forest [T(bar{? })] increases for increasing overdensity from T(bar{? })˜ 22670 to 33740 K in the redshift range z ˜ 2.8-1.6. Under the assumption of two reasonable values for ?, the temperature at the mean density (T0) shows a tendency to flatten at z ? 2.8. In the case of ? ˜ 1.5, our results are consistent with previous ones which indicate a falling T0 for redshifts z ? 2.8. Finally, our T(bar{? }) values show reasonable agreement with moderate blazar heating models.

Boera, Elisa; Murphy, Michael T.; Becker, George D.; Bolton, James S.

2014-07-01

159

Polarization of absorption lines as a diagnostics of circumstellar, interstellar and intergalactic magnetic fields: Fine structure atoms  

E-print Network

The relative population of the fine structure sublevels of an atom's ground state is affected by radiative transitions induced by an anisotropic radiation flux. This causes the alignment of atomic angular momentum. In terms of observational consequences for the interstellar and intergalactic medium, this results in the polarization of the absorption lines. In the paper we consider the conditions necessary for this effect and provide calculations of polarization from a few astrophysically important atoms and ions with multiple upper and lower levels for an arbitrary orientation of magnetic fields to the a) source of optical pumping, b) direction of observation, c) absorbed source. We also consider an astrophysically important ``degenerate'' case when the source of optical pumping coincides with the source of the absorbed radiation. We present analytical expressions that relate the degree of linear polarization and the intensity of absorption to the 3D orientation of the magnetic field with respect to the pumping source, the source of the absorbed radiation, and the direction of observations. We discuss how all these parameters can be determined via simultaneous observations of several absorption lines and suggest graphical means that are helpful in practical data interpretation. We prove that studies of absorption line polarization provide a unique tool to study 3D magnetic field topology in various astrophysical conditions.

Huirong Yan; A. Lazarian

2006-11-09

160

Tracing the Cosmic Metal Evolution in the Low-Redshift Intergalactic Medium  

E-print Network

Using the Cosmic Origins Spectrograph aboard the Hubble Space Telescope, we measured the abundances of six ions (C III, C IV, Si III, Si IV, N V, O VI) in the low-redshift (z hydrogen photoionization rate Gamma_H = (8 +/- 2) x 10^{-14} s^{-1} at z < 0.4 and specific intensity I_0 = (3 +/- 1) x 10^{-23} erg/(cm^2 s Hz sr) at the Lyman limit. We find mean photoionization parameter log U = -1.5 +/- 0.4, baryon overdensity Delta_b = 200 +/- 50, and Si/C enhanced to three times its solar ratio ...

Shull, J Michael; Tilton, Evan M

2014-01-01

161

Heating of the Hot Intergalactic Medium by Powerful Radio Galaxies and Associated High Energy Gamma-Ray Emission  

E-print Network

There is increasing evidence that some heating mechanism in addition to gravitational shock heating has been important for the hot gas inside clusters and groups of galaxies, as indicated by their observed X-ray scaling properties. While supernovae are the most obvious candidate heating sources, a number of recent studies have suggested that they may be energetically insufficient. Here we consider high-power, FRII radio galaxies and shock heating of the intracluster medium (ICM, including the case of the intergalactic medium prior to cluster formation) by their large-scale jets. Based on the observed statistics of radio galaxies in clusters and their evolution, along with the most reasonable assumptions, it is shown that they can provide the ICM with excess specific energies of 1--2 keV per particle, mainly during the redshift interval $z \\sim 1-3$. This naturally meets the requirements of cluster evolution models with non-gravitational feedback in accounting for the observed deviations in the X-ray luminosity-temperature relation. In contrast to supernovae, such large-scale jets deposit their energy directly into the low density ICM outside galaxies, and are much less susceptible to radiative losses. As a clear and potentially decisive test of this scenario, we propose the observation of `prompt' high energy gamma-rays emitted by shock-accelerated, non-thermal electrons during the epoch of ICM heating by radio galaxies, which may be feasible with the {\\it GLAST} satellite. Implications for recent detections of excess hard X-rays from groups are also discussed.

Susumu Inoue; Shin Sasaki

2001-06-11

162

Relativistic Pair Beams from TeV Blazars: A Source of Reprocessed GeV Emission rather than Intergalactic Heating  

NASA Astrophysics Data System (ADS)

The interaction of TeV photons from blazars with the extragalactic background light produces a relativistic beam of electron-positron pairs streaming through the intergalactic medium (IGM). The fate of the beam energy is uncertain. By means of two- and three-dimensional particle-in-cell simulations, we study the nonlinear evolution of dilute ultra-relativistic pair beams propagating through the IGM. We explore a wide range of beam Lorentz factors ? b Gt 1 and beam-to-plasma density ratios ? Lt 1, so that our results can be extrapolated to the extreme parameters of blazar-induced beams (? b ~ 106 and ? ~ 10-15, for powerful blazars). For cold beams, we show that the oblique instability governs the early stages of evolution, but its exponential growth terminates—due to self-heating of the beam in the transverse direction—when only a negligible fraction ~(?/? b )1/3 ~ 10-7 of the beam energy has been transferred to the IGM plasma. Further relaxation of the beam proceeds through quasi-longitudinal modes, until the momentum dispersion in the direction of propagation saturates at ?p b, ?/? b mec ~ 0.2. This corresponds to a fraction ~10% of the beam energy—irrespective of ? b or ?—being ultimately transferred to the IGM plasma (as compared to the heating efficiency of ~50% predicted by one-dimensional models, which cannot properly account for the transverse broadening of the beam). For the warm beams generated by TeV blazars, the development of the longitudinal relaxation is suppressed, since the initial dispersion in beam momentum is already ?p b0, ?/? b mec >~ 1. Here, the fraction of beam energy ultimately deposited into the IGM is only ~? ? b ~ 10-9. It follows that most of the beam energy is still available to power the GeV emission produced by inverse Compton up-scattering of the cosmic microwave background by the beam pairs.

Sironi, Lorenzo; Giannios, Dimitrios

2014-05-01

163

Heating the Intergalactic Medium by X-Rays from Population III Binaries in High-redshift Galaxies  

NASA Astrophysics Data System (ADS)

Due to their long mean free path, X-rays are expected to have an important impact on cosmic reionization by heating and ionizing the intergalactic medium (IGM) on large scales, especially after simulations have suggested that Population III (Pop III) stars may form in pairs at redshifts as high as 20-30. We use the Pop III distribution and evolution from a self-consistent cosmological radiation hydrodynamic simulation of the formation of the first galaxies and a simple Pop III X-ray binary model to estimate their X-ray output in a high-density region larger than 100 comoving (Mpc)3. We then combine three different methods—ray tracing, a one-zone model, and X-ray background modeling—to investigate the X-ray propagation, intensity distribution, and long-term effects on the IGM thermal and ionization state. The efficiency and morphology of photoheating and photoionization are dependent on the photon energies. The sub-kiloelectronvolt X-rays only impact the IGM near the sources, while the kiloelectronvolt photons contribute significantly to the X-ray background and heat and ionize the IGM smoothly. The X-rays just below 1 keV are most efficient in heating and ionizing the IGM. We find that the IGM might be heated to over 100 K by z = 10 and the high-density source region might reach 104 K, limited by atomic hydrogen cooling. This may be important for predicting the 21 cm neutral hydrogen signals. On the other hand, the free electrons from X-ray ionizations are not enough to contribute significantly to the optical depth of the cosmic microwave background to the Thomson scattering.

Xu, Hao; Ahn, Kyungjin; Wise, John H.; Norman, Michael L.; O'Shea, Brian W.

2014-08-01

164

A Snapshot Survey of AGNS/QSOS for Intergalactic Medium Studies  

NASA Technical Reports Server (NTRS)

This spectroscopic program with the Far Ultraviolet Spectroscopic Explorer (FUSE) program was designed to identify ultraviolet-bright active galactic nuclei (AGNs) and quasi-stellar objects (QSOs) for follow-up spectroscopy with FUSE and the Hubble Space Telescope (HST). All of the FUSE spectra obtained for this snapshot program (FUSE identifier D808) have been examined for data quality and flux levels. As expected, only a small number of objects observed (4/19) have flux levels suitable for follow-up spectroscopy. A portion of our effort in this program was devoted to comparing the spectra obtained in these snapshot exposures to others to determine if the spectra could be used for detailed scientific analyses. The resulting effort demonstrated that some of the brighter sources are relatively stable (non- variable), as determined through comparisons of the spectra at multiple epochs. For these brighter sources, the exposure times are simply too short to perform meaningful detailed analyses. Comparisons of the absorption lines in these spectra with those of higher signal-to-noise spectra, like those of PG1116+215 and H1821+643, showed that many of the lines of interest could not be characterized adequately at the S/N levels reached in the short snapshot exposures. As a result, the FUSE D808 observations are suitable only for their original purpose - flux determination. Several bright objects identified as part of this program include: HE0153-4520, flux >2x10E-14 erg cm^-2s^-1 at 1000 Angstroms IRASF04250-5718, flux >4x10E-14 erg cm^-2s^-1 A^-1 at 1000 Angstroms RXJ2154.1-4414, flux > 1.6x10E-14 erg cm^-2s^-1 A^-1 at 1000 Angstroms S50716+714, flux >2.5x10E-14 erg cm^-2s^-1 A^-1 at 1000 Angstroms. All of these objects have been incorporated into the primary target lists for the HST Cosmic Origins Spectrograph. Identifying such objects for follow-up observations with HST/COS was the primary goal of this program, so the program wa successful. In addition, some of the objects were included in proposed target lists for future FUSE observations. Given that the state of the FUSE observatory is uncertain at this time, it is unknown whether anyjof htese objects will be re-observed with FUSE. The results of this program have been communicated to the astronomical community via email and by word of mouth since the resuts in and of themselves do not warrant publication in an astronomical journal. However, these lists will be maintained for future observers. The data are archived in the Multi-Mission Archive at the Space Telescioe Science INstitute.

Sonneborn, George (Technical Monitor); Sembach, George

2005-01-01

165

Detection of an Intergalactic Meteor Particle with the 6-m Telescope  

E-print Network

Abstract. On July 28, 2006 the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences recorded the spectrum of a faint meteor. We confidently identify the lines of FeI and MgI, OI, NI and molecular-nitrogen (N2) bands. The entry velocity of the meteor body into the Earth’s atmosphere estimated from radial velocity is equal to 300 km/s. The body was several tens of a millimeter in size, like chondrules in carbon chondrites. The radiant of the meteor trajectory coincides with the sky position of the apex of the motion of the Solar system toward the centroid of the Local Group of galaxies. Observations of faint sporadic meteors with FAVOR TV CCD camera confirmed the radiant at a higher than 96 % confidence level. We conclude that this meteor particle is likely to be of extragalactic origin. The following important questions remain open: (1) How metal-rich dust particles came to be in the extragalactic space? (2) Why are the sizes of extragalactic particles larger by two orders of magnitude (and their masses greater by six orders of magnitude) than common interstellar dust grains in our Galaxy? (3) If extragalactic dust surrounds galaxies in the form of dust (or gas-and-dust) aureoles, can such formations now be observed using other observational techniques (IR observations aboard Spitzer satellite, etc.)? (4) If inhomogeneous extragalactic dust medium with the parameters mentioned above actually exists, does it show up in the form of irregularities on the cosmic microwave background (WMAP etc.)? 1.

V. L. Afanasiev; V. V. Kalenichenko; I. D. Karachentsev

2007-01-01

166

Detection of an intergalactic meteor particle with the 6-m telescope  

E-print Network

On July 28, 2006 the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences recorded the spectrum of a faint meteor. We confidently identify the lines of FeI and MgI, OI, NI and molecular-nitrogen N_2 bands. The entry velocity of the meteor body into the Earth's atmosphere estimated from radial velocity is equal to 300 km/s. The body was several tens of a millimeter in size, like chondrules in carbon chondrites. The radiant of the meteor trajectory coincides with the sky position of the apex of the motion of the Solar system toward the centroid of the Local Group of galaxies. Observations of faint sporadic meteors with FAVOR TV CCD camera confirmed the radiant at a higher than 96% confidence level. We conclude that this meteor particle is likely to be of extragalactic origin. The following important questions remain open: (1) How metal-rich dust particles came to be in the extragalactic space? (2) Why are the sizes of extragalactic particles larger by two orders of magnitude (and their masses greater by six orders of magnitude) than common interstellar dust grains in our Galaxy? (3) If extragalactic dust surrounds galaxies in the form of dust (or gas-and-dust) aureoles, can such formations now be observed using other observational techniques (IR observations aboard Spitzer satellite, etc.)? (4) If inhomogeneous extragalactic dust medium with the parameters mentioned above actually exists, does it show up in the form of irregularities on the cosmic microwave background (WMAP etc.)?

V. L. Afanasiev; V. V. Kalenichenko; I. D. Karachentsev

2007-12-10

167

Physical Properties and Baryonic Content of Low-Redshift Intergalactic Ly-alpha and O VI Absorption Systems: The PG1116+215 Sight Line  

Microsoft Academic Search

We present HST and FUSE observations of the intergalactic absorption toward\\u000aPG1116+215 in the 900-3000 A spectral region. We detect 25 Ly-alpha absorbers\\u000aat rest-frame equivalent widths W_r > 30 mA, yielding (dN\\/dz)_Ly-alpha =\\u000a154+\\/-18 over an unblocked redshift path of 0.162. Two additional weak Ly-alpha\\u000aabsorbers with W_r ~ 15-20 mA are also present. Eight of the Ly-alpha absorbers

Kenneth R. Sembach; Todd M. Tripp; Blair D. Savage; Philipp Richter

2004-01-01

168

A Determination of the Intergalactic Redshift Dependent UV-Optical-NIR Photon Density Using Deep Galaxy Survey Data and the Gamma-Ray Opacity of the Universe  

NASA Technical Reports Server (NTRS)

We calculate the intensity and photon spectrum of the intergalactic background light (IBL) as a function of red shift using an approach based on observational data obtained at in different wavelength bands from local to deep galaxy surveys. Our empirically based approach allows us, for the firs.t time, to obtain a completely model independent determination of the IBL and to quantify its uncertainties. Using our results on the IBL, we then place upper and lower limits on the opacity of the universe to gamma-rays, independent of previous constraints.

Stecker, Floyd W.

2012-01-01

169

A meeting with the universe: Science discoveries from the space program  

NASA Technical Reports Server (NTRS)

A general history of space exploration is presented. The solar system is discussed. The Sun-Earth relationship is considered, including magnetic fields, solar wind, the magnetosphere, and the Sun-weather relationship. The universe beyond the solar system is discussed. Topics include stellar and galactic evolution, quasars and intergalactic space. The effects of weightlessness and ionizing radiation on human beings are considered. The possibility of extraterrestrial life is discussed. Lunar and planetary exploration, solar-terrestrial physics, astrophysics, biomedical research and exobiology are reviewed. Numerons color illustrations are included.

French, B. M. (editor); Maran, S. P. (editor)

1981-01-01

170

THE COLUMN DENSITY DISTRIBUTION AND CONTINUUM OPACITY OF THE INTERGALACTIC AND CIRCUMGALACTIC MEDIUM AT REDSHIFT (z) = 2.4  

SciTech Connect

We present new high-precision measurements of the opacity of the intergalactic and circumgalactic medium (IGM; CGM) at (z) = 2.4. Using Voigt profile fits to the full Ly{alpha} and Ly{beta} forests in 15 high-resolution high-S/N spectra of hyperluminous QSOs, we make the first statistically robust measurement of the frequency of absorbers with H I column densities 14{approx}< log (N{sub H{sub I}}/cm{sup -2}){approx}<17.2. We also present the first measurements of the frequency distribution of H I absorbers in the volume surrounding high-z galaxies (the CGM, 300 pkpc), finding that the incidence of absorbers in the CGM is much higher than in the IGM. In agreement with Rudie et al., we find that there are fractionally more high-N{sub H{sub I}} absorbers than low-N{sub H{sub I}} absorbers in the CGM compared to the IGM, leading to a shallower power law fit to the CGM frequency distribution. We use these new measurements to calculate the total opacity of the IGM and CGM to hydrogen-ionizing photons, finding significantly higher opacity than most previous studies, especially from absorbers with log (N{sub H{sub I}}/cm{sup -2}) < 17.2. Reproducing the opacity measured in our data as well as the incidence of absorbers with log (N{sub H{sub I}}/cm{sup -2})>17.2 requires a broken power law parameterization of the frequency distribution with a break near N{sub H{sub I}} Almost-Equal-To 10{sup 15} cm{sup -2}. We compute new estimates of the mean free path ({lambda}{sub mfp}) to hydrogen-ionizing photons at z{sub em} = 2.4, finding {lambda}{sub mfp} = 147 {+-} 15 Mpc when considering only IGM opacity. If instead, we consider photons emanating from a high-z star-forming galaxy and account for the local excess opacity due to the surrounding CGM of the galaxy itself, the mean free path is reduced to {lambda}{sub mfp} = 121 {+-} 15 Mpc. These {lambda}{sub mfp} measurements are smaller than recent estimates and should inform future studies of the metagalactic UV background and of ionizing sources at z Almost-Equal-To 2-3.

Rudie, Gwen C.; Steidel, Charles C. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, MS 249-17, Pasadena, CA 91125 (United States); Shapley, Alice E. [Department of Astronomy, University of California, Los Angeles, 430 Portola Plaza, Los Angeles, CA 90024 (United States); Pettini, Max, E-mail: gwen@astro.caltech.edu [Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom)

2013-06-01

171

Metallicity of the intergalactic medium using pixel statistics. II. The distribution of metals as traced by C IV  

E-print Network

(Modified) We measure the distribution of carbon in the intergalactic medium as a function of redshift z and overdensity delta. Using a hydrodynamical simulation to link the H I absorption to the density and temperature of the absorbing gas, and a model for the UV background radiation, we convert ratios of C IV to H I pixel optical depths into carbon abundances. A careful analysis of 19 high-quality quasar absorption spectra reveals that the carbon abundance is spatially highly inhomogeneous and is well-described by a lognormal distribution for fixed delta and z. Using data in the range log(delta) = -0.5 - 1.8 and z = 1.8 - 4.1, and a renormalized version of the Haardt & Madau (2001) model for the UV background radiation from galaxies and quasars, we measure a median metallicity of [C/H] = -3.47 + 0.08(z-3) + 0.65[log(delta)-0.5] and a lognormal scatter of sigma([C/H]) = 0.76 + 0.02(z-3) - 0.23[log(delta)-0.5]. Thus, we find significant trends with overdensity, but no evidence for evolution. These measurements imply that gas in this density range accounts for a cosmic carbon abundance of [C/H] = -2.80 +/- 0.13 (Omega_C = 2e-7), with no evidence for evolution. The dominant source of systematic error is the spectral shape of the UV background, with harder spectra yielding higher carbon abundances. While the systematic errors due to uncertainties in the spectral hardness may exceed the quoted statistical errors for delta < 10, we stress that UV backgrounds that differ significantly from our fiducial model give unphysical results. The measured lognormal scatter is strictly independent of the spectral shape, provided the background radiation is uniform. We also present measurements of the C III/C IV ratio (which rule out collisional ionization) and of the evolution of the effective Lyman-alpha optical depth.

Joop Schaye; Anthony Aguirre; Tae-Sun Kim; Tom Theuns; Michael Rauch; Wallace L. W. Sargent

2003-06-23

172

THE COSMOLOGICAL IMPACT OF LUMINOUS TeV BLAZARS. II. REWRITING THE THERMAL HISTORY OF THE INTERGALACTIC MEDIUM  

SciTech Connect

The universe is opaque to extragalactic very high energy gamma rays (VHEGRs, E > 100 GeV) because they annihilate and pair produce on the extragalactic background light. The resulting ultrarelativistic pairs are commonly assumed to lose energy primarily through inverse Compton scattering of cosmic microwave background (CMB) photons, reprocessing the original emission from TeV to GeV energies. In Broderick et al., we argued that this is not the case; powerful plasma instabilities driven by the highly anisotropic nature of the ultrarelativistic pair distribution provide a plausible way to dissipate the kinetic energy of the TeV-generated pairs locally, heating the intergalactic medium (IGM). Here, we explore the effect of this heating on the thermal history of the IGM. We collate the observed extragalactic VHEGR sources to determine a local VHEGR heating rate. Given the pointed nature of VHEGR observations, we estimate the correction for the various selection effects using Fermi observations of high- and intermediate-peaked BL Lac objects. As the extragalactic component of the local VHEGR flux is dominated by TeV blazars, we then estimate the evolution of the TeV blazar luminosity density by tying it to the well-observed quasar luminosity density and producing a VHEGR heating rate as a function of redshift. This heating is relatively homogeneous for z {approx}< 4, but there is greater spatial variation at higher redshift (order unity at z {approx} 6) because of the reduced number of blazars that contribute to local heating. We show that this new heating process dominates photoheating in the low-redshift evolution of the IGM and calculate the effect of this heating in a one-zone model. As a consequence, the inclusion of TeV blazar heating qualitatively and quantitatively changes the structure and history of the IGM. Due to the homogeneous nature of the extragalactic background light, TeV blazars produce a uniform volumetric heating rate. This heating is sufficient to increase the temperature of the mean density IGM by nearly an order of magnitude, and at low densities by substantially more. It also naturally produces the inverted temperature-density relation inferred by recent observations of the high-redshift Ly{alpha} forest, a feature that is difficult to reconcile with standard reionization models. Finally, we close with a discussion on the possibility of detecting this hot low-density IGM suggested by our model either directly or indirectly via the local Ly{alpha} forest, the Comptonized CMB, or free-free emission, but we find that such measurements are currently not feasible.

Chang, Philip; Broderick, Avery E.; Pfrommer, Christoph, E-mail: aeb@cita.utoronto.ca, E-mail: pchang@cita.utoronto.ca, E-mail: christoph.pfrommer@h-its.org [Canadian Institute for Theoretical Astrophysics, 60 St. George Street, Toronto, ON M5S 3H8 (Canada)

2012-06-10

173

A New Method to Directly Measure the Jeans Scale of the Intergalactic Medium Using Close Quasar Pairs  

NASA Astrophysics Data System (ADS)

Although the baryons in the intergalactic medium (IGM) trace dark matter fluctuations on megaparsec scales, on smaller scales ~100 kpc, fluctuations are suppressed because the finite temperature gas is pressure supported against gravity, analogous to the classical Jeans argument. This Jeans filtering scale, which quantifies the small-scale structure of the IGM, has fundamental cosmological implications. First, it provides a thermal record of heat injected by ultraviolet photons during cosmic reionization events, and thus constrains the thermal and reionization history of the universe. Second, the Jeans scale determines the clumpiness of the IGM, a critical ingredient in models of cosmic reionization. Third, it sets the minimum mass scale for gravitational collapse from the IGM, and hence plays a pivotal role in galaxy formation. Unfortunately, it is extremely challenging to measure the Jeans scale via the standard technique of analyzing purely longitudinal Ly? forest spectra, because the thermal Doppler broadening of absorption lines along the line-of-sight, is highly degenerate with Jeans smoothing. In this work, we show that the Jeans filtering scale can be directly measured by characterizing the coherence of correlated Ly? forest absorption in close quasar pairs, with separations small enough ~100 kpc to resolve it. We present a novel technique for this purpose, based on the probability density function (PDF) of phase angle differences of homologous longitudinal Fourier modes in close quasar pair spectra. A Bayesian formalism is introduced based on the phase angle PDF, and Markov Chain Monte Carlo techniques are used to characterize the precision of a hypothetical Jeans scale measurement, and explore degeneracies with other thermal parameters governing the IGM. A semi-analytical model of the Ly? forest is used to generate a large grid (500) of thermal models from a dark matter only simulation. Our full parameter study indicates that a realistic sample of only 20 close quasar pair spectra can pinpoint the Jeans scale to ~= 5% precision, independent of the amplitude T 0 and slope ? of the temperature-density relation of the IGM T=T_0(\\rho / {\\bar{\\rho }})^{\\gamma -1}. This exquisite sensitivity arises because even long-wavelength one-dimensional Fourier modes ~10 Mpc, i.e., two orders of magnitude larger than the Jeans scale, are nevertheless dominated by projected small-scale three-dimensional (3D) power. Hence phase angle differences between all modes of quasar pair spectra actually probe the shape of the 3D power spectrum on scales comparable to the pair separation. We show that this new method for measuring the Jeans scale is unbiased and is insensitive to a battery of systematics that typically plague Ly? forest measurements, such as continuum fitting errors, imprecise knowledge of the noise level and/or spectral resolution, and metal-line absorption.

Rorai, Alberto; Hennawi, Joseph F.; White, Martin

2013-10-01

174

A NEW METHOD TO DIRECTLY MEASURE THE JEANS SCALE OF THE INTERGALACTIC MEDIUM USING CLOSE QUASAR PAIRS  

SciTech Connect

Although the baryons in the intergalactic medium (IGM) trace dark matter fluctuations on megaparsec scales, on smaller scales ?100 kpc, fluctuations are suppressed because the finite temperature gas is pressure supported against gravity, analogous to the classical Jeans argument. This Jeans filtering scale, which quantifies the small-scale structure of the IGM, has fundamental cosmological implications. First, it provides a thermal record of heat injected by ultraviolet photons during cosmic reionization events, and thus constrains the thermal and reionization history of the universe. Second, the Jeans scale determines the clumpiness of the IGM, a critical ingredient in models of cosmic reionization. Third, it sets the minimum mass scale for gravitational collapse from the IGM, and hence plays a pivotal role in galaxy formation. Unfortunately, it is extremely challenging to measure the Jeans scale via the standard technique of analyzing purely longitudinal Ly? forest spectra, because the thermal Doppler broadening of absorption lines along the line-of-sight, is highly degenerate with Jeans smoothing. In this work, we show that the Jeans filtering scale can be directly measured by characterizing the coherence of correlated Ly? forest absorption in close quasar pairs, with separations small enough ?100 kpc to resolve it. We present a novel technique for this purpose, based on the probability density function (PDF) of phase angle differences of homologous longitudinal Fourier modes in close quasar pair spectra. A Bayesian formalism is introduced based on the phase angle PDF, and Markov Chain Monte Carlo techniques are used to characterize the precision of a hypothetical Jeans scale measurement, and explore degeneracies with other thermal parameters governing the IGM. A semi-analytical model of the Ly? forest is used to generate a large grid (500) of thermal models from a dark matter only simulation. Our full parameter study indicates that a realistic sample of only 20 close quasar pair spectra can pinpoint the Jeans scale to ? 5% precision, independent of the amplitude T{sub 0} and slope ? of the temperature-density relation of the IGM T=T{sub 0}(?/ ?-bar ){sup ?-1}. This exquisite sensitivity arises because even long-wavelength one-dimensional Fourier modes ?10 Mpc, i.e., two orders of magnitude larger than the Jeans scale, are nevertheless dominated by projected small-scale three-dimensional (3D) power. Hence phase angle differences between all modes of quasar pair spectra actually probe the shape of the 3D power spectrum on scales comparable to the pair separation. We show that this new method for measuring the Jeans scale is unbiased and is insensitive to a battery of systematics that typically plague Ly? forest measurements, such as continuum fitting errors, imprecise knowledge of the noise level and/or spectral resolution, and metal-line absorption.

Rorai, Alberto; Hennawi, Joseph F. [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); White, Martin [Department of Astronomy, University of California at Berkeley, 601 Campbell Hall, Berkeley, CA 94720-3411 (United States)

2013-10-01

175

High Resolution Spectroscopy of X-ray Quasars: Searching for the X-ray Absorption from the Warm-Hot Intergalactic Medium  

NASA Technical Reports Server (NTRS)

We present a survey of six low to moderate redshift quasars with Chandra and XMM-Newton. The primary goal is to search for the narrow X-ray absorption lines produced by highly ionized metals in the Warm-Hot Intergalactic Medium. All the X-ray spectra can be well fitted by a power law with neutral hydrogen absorption. Only one feature is detected at above 3-sigma level in all the spectra, which is consistent with statistic fluctuation. We discuss the implications in our understanding of the baryon content of the universe. We also discuss the implication of the non-detection of the local (z approx. 0) X-ray absorption.

Fang, Taotao; Canizares, Claude R.; Marshall, Herman L.

2004-01-01

176

A Measurement of the Temperature-Density Relation in the Intergalactic Medium Using a New Lyman-alpha Absorption Line Fitting Method  

E-print Network

The evolution of the temperature in the intergalactic medium is related to the reionization of hydrogen and helium, and has important consequences for our understanding of the Lya forest and of galaxy formation in gravitational models of large-scale structure. We measure the temperature-density relation of intergalactic gas from Lya forest observations of eight quasar spectra with high resolution and signal-to-noise ratio, using a new line fitting technique to obtain a lower cutoff of the distribution of line widths from which the temperature is derived. We carefully test the accuracy of this technique to recover the gas temperature with a hydrodynamic simulation. The temperature at redshift z=(3.9, 3.0, 2.4) is best determined at densities slightly above the mean: T_star=(20200\\pm2700, 20200\\pm1300, 22600\\pm1900)K (statistical error bars) for gas density (in units of the mean density) Delta_star=(1.42\\pm0.08, 1.37\\pm0.11, 1.66\\pm0.11). The power-law index of the temperature-density relation, defined by T=T_star(Delta/Delta_star)^{gamma-1}, is gamma-1= (0.43\\pm0.45, 0.29\\pm0.30, 0.52\\pm0.14) for the same three redshifts. The temperature at the fixed over-density Delta=1.4 is T_1.4=(20100\\pm2800, 20300\\pm1400, 20700\\pm1900)K. These temperatures are higher than expected for photoionized gas in ionization equilibrium with a cosmic background, and can be explained by a gradual additional heating due to on-going HeII reionization. The measurement of the temperature reduces one source of uncertainty in the lower limit to the baryon density implied by the observed mean flux decrement. We find that the temperature cannot be reliably measured for under-dense gas, because the velocities due to expansion always dominate the widths of the corresponding weak lines.

Patrick McDonald; Jordi Miralda-Escude; Michael Rauch; Wallace L. W. Sargent; Tom A. Barlow; Renyue Cen

2000-05-29

177

THE SIZE AND ORIGIN OF METAL-ENRICHED REGIONS IN THE INTERGALACTIC MEDIUM FROM SPECTRA OF BINARY QUASARS  

SciTech Connect

We present tomography of the circum-galactic metal distribution at redshift 1.7-4.5 derived from echellete spectroscopy of binary quasars. We find C IV systems at similar redshifts in paired sightlines more often than expected for sightline-independent redshifts. As the separation of the sightlines increases from 36 kpc to 907 kpc, the amplitude of this clustering decreases. At the largest separations, the C IV systems cluster similar to the Lyman-break galaxies studied by Adelberger et al. in 2005. The C IV systems are significantly less correlated than these galaxies, however, at separations less than R{sub 1} {approx_equal} 0.42 {+-} 0.15 h {sup -1} comoving Mpc. Measured in real space, i.e., transverse to the sightlines, this length scale is significantly smaller than the break scale estimated previously from the line-of-sight correlation function in redshift space by Scannapieco et al. in 2006. Using a simple model, we interpret the new real-space measurement as an indication of the typical physical size of enriched regions. We adopt this size for enriched regions and fit the redshift-space distortion in the line-of-sight correlation function. The fitted velocity kick is consistent with the peculiar velocity of galaxies as determined by the underlying mass distribution and places an upper limit on the average outflow (or inflow) speed of metals. The implied timescale for dispersing metals is larger than the typical stellar ages of Lyman-break galaxies, and we argue that enrichment by galaxies at z {>=} 4.3 played a greater role in dispersing metals. To further constrain the growth of enriched regions, we discuss empirical constraints on the evolution of the C IV correlation function with cosmic time. This study demonstrates the potential of tomography for measuring the metal enrichment history of the circum-galactic medium.

Martin, Crystal L.; Fournier, Amanda P. [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Scannapieco, Evan [School of Earth and Space Exploration, Arizona State University, P.O. Box 871404, Tempe, AZ 85287-1404 (United States); Ellison, Sara L. [Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia, V8P 1A1 (Canada); Hennawi, Joseph F. [Department of Astronomy, 601 Campbell Hall, University of California, Berkeley, CA 94720-3411 (United States); Djorgovski, S. G., E-mail: cmartin@physics.ucsb.ed [Division of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States)

2010-09-20

178

Line-emitting Galaxies beyond a Redshift of 7: An Improved Method for Estimating the Evolving Neutrality of the Intergalactic Medium  

NASA Astrophysics Data System (ADS)

The redshift-dependent fraction of color-selected galaxies revealing Lyman alpha (Ly?) emission, x Ly? has become the most valuable constraint on the evolving neutrality of the early intergalactic medium. However, in addition to resonant scattering by neutral gas, the visibility of Ly? is also dependent on the intrinsic properties of the host galaxy, including its stellar population, dust content, and the nature of outflowing gas. Taking advantage of significant progress we have made in determining the line-emitting properties of z ~= 4-6 galaxies, we propose an improved method, based on using the measured slopes of the rest-frame ultraviolet continua of galaxies, to interpret the growing body of near-infrared spectra of z > 7 galaxies in order to take into account these host galaxy dependencies. In a first application of our new method, we demonstrate its potential via a new spectroscopic survey of 7 < z < 8 galaxies undertaken with the Keck MOSFIRE spectrograph. Together with earlier published data, our data provide improved estimates of the evolving visibility of Ly?, particularly at redshift z ~= 8. As a by-product, we also present a promising new line-emitting galaxy candidate, detected at 4.0? at redshift z = 7.62. We discuss the improving constraints on the evolving neutral fraction over 6 < z < 8 and the implications for cosmic reionization.

Schenker, Matthew A.; Ellis, Richard S.; Konidaris, Nick P.; Stark, Daniel P.

2014-11-01

179

Stochastic Absorption of the Light of Background Sources due to Intergalactic Neutral Hydrogen I. Testing different line-number evolution models via the cosmic flux decrement  

E-print Network

We test the accuracy of different models of the attenuation of light due to intergalactic neutral hydrogen by comparing their predictions of the evolution of the mean cosmic flux decrement D_A to its measurements based on observations. To this end, we use data available in the literature and our own measurements of D_A for 25 QSOs in the redshift range 2.64 the SDSS Data Release 5. In order to perform the measurements of D_A, we fit a power-law to the continuum redward of the Lyman Alpha emission line, and extrapolate this fit to region blueward of it, where the flux is severely affected by absorption due to intervening HI absorbers. We compute, using numerical simulations, the redshift evolution of the mean flux depression due to the presence of Lyman Alpha Forest absorbers and Lyman limit systems randomly distributed along the line-of-sight, and compute its intrinsic scatter at the 1-, 2-, and 3$\\sigma$ level due to fluctuations in the absorber properties (column density, Doppler...

Tepper-Garc{\\'\\i}a, Thorsten

2007-01-01

180

Star Formation and the Interstellar Medium In Nearby Tidal Streams (SAINTS): Spitzer Mid-infrared Spectroscopy and Imaging of Intergalactic Star-forming Objects  

E-print Network

A spectroscopic analysis of 10 intergalactic star forming objects (ISFOs) and a photometric analysis of 67 ISFOs in a sample of 14 interacting systems is presented. The majority of the ISFOs have relative polycyclic aromatic hydrocarbon (PAH) band strengths similar to those of nearby spiral and starburst galaxies. In contrast to what is observed in blue compact dwarfs (BCDs) and local giant HII regions in the Milky Way (NGC 3603) and the Magellanic Clouds (30 Doradus and N 66), the relative PAH band strengths in ISFOs correspond to models with a significant PAH ion fraction ( 3.7, i.e., enhanced non-stellar emission, most likely due to PAHs, relative to normal spirals, dwarf irregulars and BCD galaxies. The relative strength of the 8 um emission compared to that at 3.6 um or 24 um separates ISFOs from dwarf galaxies in Spitzer two color diagrams. The infrared power in two thirds of the ISFOs is dominated by emission from grains in a diffuse interstellar medium. One in six ISFOs have significant emission from ...

Higdon, S J U; Smith, B J; Hancock, M

2014-01-01

181

Space Elevator: Path to Space  

NASA Astrophysics Data System (ADS)

The Space Elevator is the most promising Space Transportation system on the drawing boards today, combining scalability, qualify of ride, and safety to deliver truly commercial-grade space access-practically comparable to a train ride to space.

Kaushal, A. K.

2012-05-01

182

Extreme Ultraviolet Absorption Lines in LyA Forest Absorbers and the Oxygen Abundance in the Intergalactic Medium  

Microsoft Academic Search

We create stacked composite absorption spectra from Hubble Space Telescope\\u000aFaint Object Spectrograph data from four quasi-stellar objects to search for\\u000aabsorption lines in the extreme ultraviolet wavelength region associated with\\u000aLyA forest absorbers in the redshift range 1.6 < z < 2.9. We successfully\\u000adetect O V 630 in LyA absorbers throughout the 10^13 to 10^16.2 cm^-2 column\\u000adensity

Randal C. Telfer; Gerard A. Kriss; Wei Zheng; Arthur F. Davidsen; David Tytler

2002-01-01

183

Space Tools! Space Tools!  

E-print Network

of the Universe. Radio telescopes are also used to search for signs of intelligent life on other planets. 13 #12 and planets they saw. The only tools they had to study space were their eyes and their imaginations. They had no other tools to help them learn what these lights in the sky really were. As people studied the night sky

184

Space Communication  

Microsoft Academic Search

As the space era approaches, the importance of including space science in the general curriculum and communicating space science to the general public is becoming extremely important. The paper, points out that the inclusion of more space education in the school curriculum and to the general public will increase awareness and interest in the new developments of space exploration. The

Bhavini Patel

2002-01-01

185

Space Travel  

NSDL National Science Digital Library

Students are introduced to the historical motivation for space exploration. They learn about the International Space Station as an example of space travel innovation and are introduced to new and futuristic ideas that space engineers are currently working on to propel space research far into the future!

Integrated Teaching And Learning Program

186

Space Discovery.  

ERIC Educational Resources Information Center

Describes one teacher's experience taking Space Discovery courses that were sponsored by the United States Space Foundation (USSF). These courses examine the history of space science, theory of orbits and rocketry, the effects of living in outer space on humans, and space weather. (DDR)

Blackman, Joan

1998-01-01

187

Space Shuttle  

NASA Technical Reports Server (NTRS)

The space shuttle flight system and mission profile are briefly described. Emphasis is placed on the economic and social benefits of the space transportation system. The space shuttle vehicle is described in detail.

1976-01-01

188

Space Station  

NASA Technical Reports Server (NTRS)

The official start of a bold new space program, essential to maintain the United States' leadership in space was signaled by a Presidential directive to move aggressively again into space by proceeding with the development of a space station. Development concepts for a permanently manned space station are discussed. Reasons for establishing an inhabited space station are given. Cost estimates and timetables are also cited.

Anderton, D. A.

1985-01-01

189

Probing intergalactic neutral hydrogen by the Lyman alpha red damping wing of gamma-ray burst 130606A afterglow spectrum at z = 5.913  

NASA Astrophysics Data System (ADS)

The unprecedentedly bright optical afterglow of GRB 130606A located by Swift at a redshift close to the reionization era (z = 5.913) provides a new opportunity to probe the ionization status of the intergalactic medium (IGM). Here we present an analysis of the red Ly? damping wing of the afterglow spectrum taken by Subaru/FOCAS during 10.4-13.2 hr after the burst. We find that the minimal model including only the baseline power-law and H I absorption in the host galaxy does not give a good fit, leaving residuals showing concave curvature in 8400-8900 Å with an amplitude of about 0.6% of the flux. Such a curvature in the short wavelength range cannot be explained either by extinction at the host with standard extinction curves, intrinsic curvature of afterglow spectra, or by the known systematic uncertainties in the observed spectrum. The red damping wing by intervening H I gas outside the host can reduce the residual by about 3 ? statistical significance. We find that a damped Ly? system is not favored as the origin of this intervening H I absorption, from the observed Ly? and metal absorption features. Therefore absorption by diffuse IGM remains as a plausible explanation. A fit by a simple uniform IGM model requires an H I neutral fraction of fH I ˜ 0.1-0.5 depending on the distance to the GRB host, implying high fH I IGM associated with the observed dark Gunn-Peterson (GP) troughs. This gives new evidence that the reionization is not yet complete at z = 6.

Totani, Tomonori; Aoki, Kentaro; Hattori, Takashi; Kosugi, George; Niino, Yuu; Hashimoto, Tetsuya; Kawai, Nobuyuki; Ohta, Kouji; Sakamoto, Takanori; Yamada, Toru

2014-06-01

190

New Limits on 21 cm Epoch of Reionization from PAPER-32 Consistent with an X-Ray Heated Intergalactic Medium at z = 7.7  

NASA Astrophysics Data System (ADS)

We present new constraints on the 21 cm Epoch of Reionization (EoR) power spectrum derived from three months of observing with a 32 antenna, dual-polarization deployment of the Donald C. Backer Precision Array for Probing the Epoch of Reionization in South Africa. In this paper, we demonstrate the efficacy of the delay-spectrum approach to avoiding foregrounds, achieving over eight orders of magnitude of foreground suppression (in mK2). Combining this approach with a procedure for removing off-diagonal covariances arising from instrumental systematics, we achieve a best 2? upper limit of (41 mK)2 for k = 0.27 h Mpc-1 at z = 7.7. This limit falls within an order of magnitude of the brighter predictions of the expected 21 cm EoR signal level. Using the upper limits set by these measurements, we generate new constraints on the brightness temperature of 21 cm emission in neutral regions for various reionization models. We show that for several ionization scenarios, our measurements are inconsistent with cold reionization. That is, heating of the neutral intergalactic medium (IGM) is necessary to remain consistent with the constraints we report. Hence, we have suggestive evidence that by z = 7.7, the H I has been warmed from its cold primordial state, probably by X-rays from high-mass X-ray binaries or miniquasars. The strength of this evidence depends on the ionization state of the IGM, which we are not yet able to constrain. This result is consistent with standard predictions for how reionization might have proceeded.

Parsons, Aaron R.; Liu, Adrian; Aguirre, James E.; Ali, Zaki S.; Bradley, Richard F.; Carilli, Chris L.; DeBoer, David R.; Dexter, Matthew R.; Gugliucci, Nicole E.; Jacobs, Daniel C.; Klima, Pat; MacMahon, David H. E.; Manley, Jason R.; Moore, David F.; Pober, Jonathan C.; Stefan, Irina I.; Walbrugh, William P.

2014-06-01

191

Star Formation and the Interstellar Medium in Nearby Tidal Streams (SAINTS): Spitzer Mid-infrared spectroscopy and Imaging of Intergalactic Star-forming Objects  

NASA Astrophysics Data System (ADS)

A spectroscopic analysis of 10 intergalactic star-forming objects (ISFOs) and a photometric analysis of 67 ISFOs in a sample of 14 interacting systems is presented. The majority of the ISFOs have relative polycyclic aromatic hydrocarbon (PAH) band strengths similar to those of nearby spiral and starburst galaxies. In contrast to what is observed in blue compact dwarfs (BCDs) and local giant H II regions in the Milky Way (NGC 3603) and the Magellanic Clouds (30 Doradus and N 66), the relative PAH band strengths in ISFOs correspond to models with a significant PAH ion fraction (<50%) and bright emission from large PAHs (~100 carbon atoms). The [Ne III]/[Ne II] and [S IV]/[S III] line flux ratios indicate moderate levels of excitation with an interstellar radiation field that is harder than the majority of the Spitzer Infrared Nearby Galaxies Survey and starburst galaxies, but softer than BCDs and local giant H II regions. The ISFO neon line flux ratios are consistent with a burst of star formation lsim6 million years ago. Most of the ISFOs have ~106 M ? of warm H2 with a likely origin in photo-dissociation regions (PDRs). Infrared Array Camera photometry shows the ISFOs to be bright at 8 ?m, with one-third having [4.5] - [8.0] > 3.7, i.e., enhanced non-stellar emission, most likely due to PAHs, relative to normal spirals, dwarf irregulars, and BCD galaxies. The relative strength of the 8 ?m emission compared to that at 3.6 ?m or 24 ?m separates ISFOs from dwarf galaxies in Spitzer two-color diagrams. The infrared power in two-thirds of the ISFOs is dominated by emission from grains in a diffuse interstellar medium. One in six ISFOs have significant emission from PDRs, contributing ~30%-60% of the total power. ISFOs are young knots of intense star formation.

Higdon, S. J. U.; Higdon, J. L.; Smith, B. J.; Hancock, M.

2014-06-01

192

Stochastic Absorption of the Light of Background Sources due to Intergalactic Neutral Hydrogen I. Testing different line-number evolution models via the cosmic flux decrement  

E-print Network

[Abridged] We test the accuracy of different models of the attenuation of light due to resonant scattering by intergalactic neutral hydrogen by comparing their predictions of the evolution of the mean cosmic flux decrement, D_A, to measurements of this quantity based on observations. To this end, we use data available in the literature and our own measurements of the cosmic flux decrement for 25 quasars in the redshift range 2.71 of D_A, we fit a power-law to the continuum redward of the Lya emission line, and extrapolate this fit to region blueward of it, where the flux is severely affected by absorption due to intervening HI absorbers. We compute, using numerical simulations, the redshift evolution of D_A accounting for the presence of Lya Forest absorbers and Lyman limit systems randomly distributed along the line-of-sight, and compute its intrinsic scatter at the 1-, 2-, and 3-sigma level due to fluctuations in the absorber properties (column density, Doppler parameter, redshift) along different lines-of-sight. The numerical simulations consist of Monte Carlo realizations of distributions of the absorber properties constrained from observations. The results from the models considered here confirm our theoretical expectation that the distribution of D_A at any given redshift be well described by a lognormal distribution function. This implies that the effective optical depth, usually defined as the negative logarithm of the average flux, 1 - D_A, is very accurately Gaussian distributed, in contrast to previous studies. This result is independent to the form of the input distribution functions, and rather insensitive to the presence of high-column density absorbers, such as the Lyman limit systems.

Thorsten Tepper-Garcia; Uta Fritze

2007-05-09

193

Space colonization.  

PubMed

NASA interest in colonization encompasses space tourism; space exploration; space bases in orbit, at L1, on the Moon, or on Mars; in-situ resource utilization; and planetary terraforming. Activities progressed during 2002 in areas such as Mars colonies, hoppers, and biomass; space elevators and construction; and in-situ consumables. PMID:12506926

2002-12-01

194

Themed Space  

ERIC Educational Resources Information Center

This article presents a classroom activity that introduces students to the concept of themed space. Students learn to think critically about the spaces they encounter on a regular basis by analyzing existing spaces and by working in groups to create their own themed space. This exercise gives students the chance to see the relevance of critical…

Lynch, Christopher O.

2010-01-01

195

A LYMAN BREAK GALAXY IN THE EPOCH OF REIONIZATION FROM HUBBLE SPACE TELESCOPE GRISM SPECTROSCOPY  

SciTech Connect

We present observations of a luminous galaxy at z = 6.573-the end of the reionization epoch-which has been spectroscopically confirmed twice. The first spectroscopic confirmation comes from slitless Hubble Space Telescope Advanced Camera for Surveys grism spectra from the PEARS survey (Probing Evolution And Reionization Spectroscopically), which show a dramatic continuum break in the spectrum at rest frame 1216 A. The second confirmation is done with Keck + DEIMOS. The continuum is not clearly detected with ground-based spectra, but high wavelength resolution enables the Ly{alpha} emission line profile to be determined. We compare the line profile to composite line profiles at z = 4.5. The Ly{alpha} line profile shows no signature of a damping wing attenuation, confirming that the intergalactic gas is ionized at z = 6.57. Spectra of Lyman breaks at yet higher redshifts will be possible using comparably deep observations with IR-sensitive grisms, even at redshifts where Ly{alpha} is too attenuated by the neutral intergalactic medium to be detectable using traditional spectroscopy from the ground.

Rhoads, James E.; Malhotra, Sangeeta; Cohen, Seth; Zheng Zhenya [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 (United States); Stern, Daniel [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Dickinson, Mark [National Optical Astronomy Observatory, Tucson, AZ (United States); Pirzkal, Norbert; Grogin, Norman; Koekemoer, Anton; Peth, Michael A. [Space Telescope Science Institute, Baltimore, MD (United States); Spinrad, Hyron [University of California, Berkeley, CA (United States); Reddy, Naveen [University of California, Riverside, CA (United States); Hathi, Nimish [Observatories of the Carnegie Institution of Washington, Pasadena, CA (United States); Budavari, Tamas [Johns Hopkins University, Baltimore, MD (United States); Ferreras, Ignacio [Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT (United Kingdom); Gardner, Jonathan P. [NASA Goddard Space Flight Center, Astrophysics Science Division, Observational Cosmology Laboratory, Code 665, Greenbelt, MD 20771 (United States); Gronwall, Caryl [Department of Astronomy and Astrophysics, and Institute for Gravitation and the Cosmos, The Pennsylvania State University, University Park, PA 16802 (United States); Haiman, Zoltan [Columbia University, New York, NY (United States); Kuemmel, Martin [Universitaets-Sternwarte Muenchen, Scheinerstr. 1, D-81679 Muenchen (Germany); Meurer, Gerhardt, E-mail: James.Rhoads@asu.edu [International Centre for Radio Astronomy Research, University of Western Australia, M468, 35 Stirling Highway, Crawley, WA 6009 (Australia); and others

2013-08-10

196

Space Missions  

NSDL National Science Digital Library

With three levels to choose from on each page - beginner, intermediate or advanced - this site provides in formation on past and current exploration ideas and achievements. The advances science has made in the space exploration area, such as having a permanent space station in space and the hundreds of probes, satellite, and space shuttles that have been launched. Advanced telescopes have given scientists the opportunity to see far beyond we ever imagined, and new explorations are found every day. Also featured are details about the International space station and what kinds of experiments scientists do in outer space.

Russell, Randy

2004-05-10

197

GRB 130606A as a Probe of the Intergalactic Medium and the Interstellar Medium in a Star-forming Galaxy in the First Gyr after the Big Bang  

NASA Astrophysics Data System (ADS)

We present high signal-to-noise ratio Gemini and MMT spectroscopy of the optical afterglow of the gamma-ray burst (GRB) 130606A at redshift z = 5.913, discovered by Swift. This is the first high-redshift GRB afterglow to have spectra of comparable quality to those of z ? 6 quasars. The data exhibit a smooth continuum at near-infrared wavelengths that is sharply cut off blueward of 8410 Å due to absorption from Ly? at redshift z ? 5.91, with some flux transmitted through the Ly? forest between 7000 and 7800 Å. We use column densities inferred from metal absorption lines to constrain the metallicity of the host galaxy between a lower limit of [Si/H] >~ -1.7 and an upper limit of [S/H] <~ -0.5 set by the non-detection of S II absorption. We demonstrate consistency between the dramatic evolution in the transmission fraction of Ly? seen in this spectrum over the redshift range z = 4.9-5.85 with that previously measured from observations of high-redshift quasars. There is an extended redshift interval of ?z = 0.12 in the Ly? forest at z = 5.77 with no detected transmission, leading to a 3? upper limit on the mean Ly? transmission fraction of lsim0.2% (or \\tau _{{GP}}^{{eff}} (Ly?) > 6.4). This is comparable to the lowest-redshift Gunn-Peterson troughs found in quasar spectra. Some Ly? and Ly? transmission is detected in this redshift window, indicating that it is not completely opaque, and hence that the intergalactic medium (IGM) is nonetheless mostly ionized at these redshifts. We set a 2? upper limit of 0.11 on the neutral fraction of the IGM at the redshift of the GRB from the lack of a Ly? red damping wing, assuming a model with a constant neutral density. GRB 130606A thus for the first time realizes the promise of GRBs as probes of the first galaxies and cosmic reionization.

Chornock, Ryan; Berger, Edo; Fox, Derek B.; Lunnan, Ragnhild; Drout, Maria R.; Fong, Wen-fai; Laskar, Tanmoy; Roth, Katherine C.

2013-09-01

198

PROBING THE INTERGALACTIC MEDIUM/GALAXY CONNECTION. V. ON THE ORIGIN OF Ly{alpha} AND O VI ABSORPTION AT z < 0.2  

SciTech Connect

We analyze the association of galaxies with Ly{alpha} and O VI absorption, the most commonly detected transitions of the low-z intergalactic medium (IGM), in the fields of 14 quasars with z{sub em} = 0.06-0.57. Confirming previous studies, we observe a high covering fraction for Ly{alpha} absorption to impact parameter {rho} = 300 h{sup -1}{sub 72} kpc: 33/37 of our L > 0.01 L* galaxies show Ly{alpha} equivalent width W{sup Ly{alpha}} {>=} 50 mA. Galaxies of all luminosity L > 0.01 L* and spectral type are surrounded by a diffuse and ionized circumgalactic medium (CGM), whose baryonic mass is estimated at {approx}10{sup 10.5{+-}0.3} M{sub sun} for a constant N{sub H} = 10{sup 19} cm{sup -2}. The virialized halos and extended CGM of present-day galaxies are responsible for most strong Ly{alpha} absorbers (W{sup Ly{alpha}} > 300 mA) but cannot reproduce the majority of observed lines in the Ly{alpha} forest. We conclude that the majority of Ly{alpha} absorption with W{sup Ly{alpha}} = 30-300 mA occurs in the cosmic web predicted by cosmological simulations and estimate a characteristic width for these filaments of {approx}400 h{sup -1}{sub 72} kpc. Regarding O VI, we observe a near unity covering fraction to {rho} = 200 h{sup -1}{sub 72} kpc for L > 0.1 L* galaxies and to {rho} = 300 h{sup -1}{sub 72} kpc for sub-L* (0.1 L* < L < L*) galaxies. Similar to our Ly{alpha} results, stronger O VI systems (W{sup 1031} > 70 mA) arise in the virialized halos of L > 0.1 L* galaxies. Unlike Ly{alpha}, the weaker O VI systems (W{sup 1031} {approx} 30 mA) arise in the extended CGM of sub-L* galaxies. The majority of O VI gas observed in the low-z IGM is associated with a diffuse medium surrounding individual galaxies with L {approx} 0.3 L* and rarely originates in the so-called warm-hot IGM (predicted by cosmological simulations.

Prochaska, J. Xavier [Department of Astronomy and Astrophysics and UCO/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States); Weiner, B. [Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721 (United States); Chen, H.-W. [Department of Astronomy, University of Chicago, 5640 S. Ellis Ave., Chicago, IL 60637 (United States); Mulchaey, J. [Carnegie Observatories, 813 Santa Barbara St., Pasadena, CA 91101 (United States); Cooksey, K., E-mail: xavier@ucolick.org, E-mail: bjw@as.arizona.edu, E-mail: hchen@oddjob.uchicago.edu, E-mail: mulchaey@obs.carnegiescience.edu, E-mail: kcooksey@space.mit.edu [MIT Kavli Institute for Astrophysics and Space Research, 77 Massachusetts Avenue, 37-611, Cambridge, MA 02139 (United States)

2011-10-20

199

Intergalactic Medium Emission Observations with the Cosmic Web Imager. II. Discovery of Extended, Kinematically Linked Emission around SSA22 Ly? Blob 2  

NASA Astrophysics Data System (ADS)

The intergalactic medium (IGM) is the dominant reservoir of baryons, delineates the large-scale structure of the universe at low to moderate overdensities, and provides gas from which galaxies form and evolve. Simulations of a cold-dark-matter- (CDM-) dominated universe predict that the IGM is distributed in a cosmic web of filaments and that galaxies should form along and at the intersections of these filaments. While observations of QSO absorption lines and the large-scale distribution of galaxies have confirmed the CDM paradigm, the cosmic web of IGM has never been confirmed by direct imaging. Here we report our observation of the Ly? blob 2 (LAB2) in SSA22 with the Cosmic Web Imager (CWI). This is an integral field spectrograph optimized for low surface brightness, extended emission. With 22 hr of total on- and off-source exposure, CWI has revealed that LAB2 has extended Ly? emission that is organized into azimuthal zones consistent with filaments. We perform numerous tests with simulations and the data to secure the robustness of this result, which relies on data with modest signal-to-noise ratios. We have developed a smoothing algorithm that permits visualization of data cube slices along image or spectral image planes. With both raw and smoothed data cubes we demonstrate that the filaments are kinematically associated with LAB2 and display double-peaked profiles characteristic of optically thick Ly? emission. The flux is 10-20 times brighter than expected for the average emission from the IGM but is consistent with boosted fluorescence from a buried QSO or gravitation cooling radiation. Using simple emission models, we infer a baryon mass in the filaments of at least 1-4 × 1011 M ?, and the dark halo mass is at least 2 × 1012 M ?. The spatial-kinematic morphology is more consistent with inflow from the cosmic web than outflow from LAB2, although an outflow feature maybe present at one azimuth. LAB2 and the surrounding gas have significant and coaligned angular momentum, strengthening the case for their association.

Martin, D. Christopher; Chang, Daphne; Matuszewski, Matt; Morrissey, Patrick; Rahman, Shahin; Moore, Anna; Steidel, Charles C.; Matsuda, Yuichi

2014-05-01

200

Chandra View of the Warm-hot Intergalactic Medium toward 1ES 1553+113: Absorption-line Detections and Identifications. I.  

NASA Astrophysics Data System (ADS)

We present the first results from our pilot 500 ks Chandra Low Energy Transmission Grating Large Program observation of the soft X-ray brightest source in the z >~ 0.4 sky, the blazar 1ES 1553+113, aimed to secure the first uncontroversial detections of the missing baryons in the X-rays. We identify a total of 11 possible absorption lines, with single-line statistical significances between 2.2? and 4.1?. Six of these lines are detected at high single-line statistical significance (3.6 <= ? <= 4.1), while the remaining five are regarded as marginal detections in association with either other X-ray lines detected at higher significance and/or far-ultraviolet (FUV) signposts. Three of these lines are consistent with metal absorption at z ~= 0, and we identify them with Galactic O I and C II. The remaining eight lines may be imprinted by intervening absorbers and are all consistent with being high-ionization counterparts of FUV H I and/or O VI intergalactic medium signposts. In particular, five of these eight possible intervening absorption lines (single-line statistical significances of 4.1?, 4.1?, 3.9?, 3.8?, and 2.7?), are identified as C V and C VI K? absorbers belonging to three WHIM systems at zX = 0.312, zX = 0.237, and langzX rang = 0.133, which also produce broad H I (and O VI for the zX = 0.312 system) absorption in the FUV. For two of these systems (zX = 0.312 and 0.237), the Chandra X-ray data led the a posteriori discovery of physically consistent broad H I associations in the FUV (for the third system the opposite applies), so confirming the power of the X-ray-FUV synergy for WHIM studies. The true statistical significances of these three X-ray absorption systems, after properly accounting for the number of redshift trials, are 5.8? (zX = 0.312; 6.3? if the low-significance O V and C V K? associations are considered), 3.9? (zX = 0.237), and 3.8? (langzX rang = 0.133), respectively.

Nicastro, F.; Elvis, M.; Krongold, Y.; Mathur, S.; Gupta, A.; Danforth, C.; Barcons, X.; Borgani, S.; Branchini, E.; Cen, R.; Davé, R.; Kaastra, J.; Paerels, F.; Piro, L.; Shull, J. M.; Takei, Y.; Zappacosta, L.

2013-06-01

201

CHANDRA VIEW OF THE WARM-HOT INTERGALACTIC MEDIUM TOWARD 1ES 1553+113: ABSORPTION-LINE DETECTIONS AND IDENTIFICATIONS. I  

SciTech Connect

We present the first results from our pilot 500 ks Chandra Low Energy Transmission Grating Large Program observation of the soft X-ray brightest source in the z {approx}> 0.4 sky, the blazar 1ES 1553+113, aimed to secure the first uncontroversial detections of the missing baryons in the X-rays. We identify a total of 11 possible absorption lines, with single-line statistical significances between 2.2{sigma} and 4.1{sigma}. Six of these lines are detected at high single-line statistical significance (3.6 {<=} {sigma} {<=} 4.1), while the remaining five are regarded as marginal detections in association with either other X-ray lines detected at higher significance and/or far-ultraviolet (FUV) signposts. Three of these lines are consistent with metal absorption at z {approx_equal} 0, and we identify them with Galactic O I and C II. The remaining eight lines may be imprinted by intervening absorbers and are all consistent with being high-ionization counterparts of FUV H I and/or O VI intergalactic medium signposts. In particular, five of these eight possible intervening absorption lines (single-line statistical significances of 4.1{sigma}, 4.1{sigma}, 3.9{sigma}, 3.8{sigma}, and 2.7{sigma}), are identified as C V and C VI K{alpha} absorbers belonging to three WHIM systems at z{sub X} = 0.312, z{sub X} = 0.237, and (z{sub X} ) = 0.133, which also produce broad H I (and O VI for the z{sub X} = 0.312 system) absorption in the FUV. For two of these systems (z{sub X} = 0.312 and 0.237), the Chandra X-ray data led the a posteriori discovery of physically consistent broad H I associations in the FUV (for the third system the opposite applies), so confirming the power of the X-ray-FUV synergy for WHIM studies. The true statistical significances of these three X-ray absorption systems, after properly accounting for the number of redshift trials, are 5.8{sigma} (z{sub X} = 0.312; 6.3{sigma} if the low-significance O V and C V K{beta} associations are considered), 3.9{sigma} (z{sub X} = 0.237), and 3.8{sigma} ((z{sub X} ) = 0.133), respectively.

Nicastro, F.; Zappacosta, L. [Osservatorio Astronomico di Roma-INAF, Via di Frascati 33, I-00040 Monte Porzio Catone, RM (Italy); Elvis, M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., MS-04, Cambridge, MA 02138 (United States); Krongold, Y. [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Mexico City Mexico (Mexico); Mathur, S.; Gupta, A. [Ohio State University, Columbus, OH (United States); Danforth, C.; Shull, J. M. [CASA, Department of Astrophysical and Planetary Sciences, University of Colorado, 389-UCB, Boulder, CO 80309 (United States); Barcons, X. [Instituto de Fisica de Cantabria (CSIC-UC), E-39005 Santander (Spain); Borgani, S. [Dipartimento di Astronomia dell'Universita di Trieste, Via G.B. Tiepolo 11, I-34131 Trieste (Italy); Branchini, E. [Dipartimento di Fisica ''E. Amaldi'', Universita degli Studi ''Roma Tre'', via della Vasca Navale 84, I-00146 Roma (Italy); Cen, R. [Princeton University Observatory, Princeton, NJ 08544 (United States); Dave, R. [Astronomy Department, University of Arizona, Tucson, AZ 85721 (United States); Kaastra, J. [SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA, Utrecht (Netherlands); Paerels, F. [Columbia Astrophysics Laboratory and Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027 (United States); Piro, L. [INAF-IAPS, Via del Fosso del Cavaliere 100, I-00133 Roma (Italy); Takei, Y. [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan)

2013-06-01

202

Amazing Space  

NSDL National Science Digital Library

The Space Telescope Science Institute's Amazing Space site is the product of teachers teamed up with scientists and engineers and staff from the institute. This site has interactive lessons in astronomy and math designed for the web.

Space Telescope Science Institute, Formal E.

2003-10-10

203

Innovation Spaces  

E-print Network

Innovation ecosystems today are the lifeblood or the great hope of many major economies, but at the heart of these ecosystems, there are places and spaces. Silicon Valley is not just a place, but a cluster of spaces where ...

Schneider-Sikorsky, Patrick A

2014-01-01

204

Space Update  

NSDL National Science Digital Library

This DVD includes space science images, movies and activities aligned with national standards. Includes the following sections: Astronomy, Solar System, Sky Tonight, and Space Weather models, which run separately or as a linked system, plus Space Events. It is safe for unattended use and suitable for museums or school libraries. Images can be updated without need of an open web browser.

2006-01-01

205

Space Survey  

NSDL National Science Digital Library

This is a lesson about society and space exploration. Learners will survey the public about their different opinions about space exploration and the use of robotics in space exploration. Then they will represent and analyze the results. This is lesson 5 of 16 in the MarsBots learning module.

206

Multipurpose Spaces  

ERIC Educational Resources Information Center

The concept of multipurpose spaces in schools is certainly not new. Especially in elementary schools, the combination of cafeteria and auditorium (and sometimes indoor physical activity space as well) is a well-established approach to maximizing the use of school space and a school district's budget. Nonetheless, there continue to be refinements…

Gordon, Douglas

2010-01-01

207

Space Kimchi  

E-print Network

Broadcast Transcript: In space, no one can hear you scream... but did you know that in space no one can detect your smell either? The smell-taste connection means that food in space is not only weightless but tasteless, too. What's a flavor...

Hacker, Randi; Oborny, Jaimie; Tsutsui, William

2006-07-05

208

$?$--Rindler space  

E-print Network

In this paper we construct, and investigate some thermal properties of, the non-commutative counterpart of Rindler space, which we call $\\kappa$--Rindler space. This space is obtained by changing variables in the defining commutators of $\\kappa$--Minkowski space. We then re-derive the commutator structure of $\\kappa$--Rindler space with the help of an appropriate star product, obtained from the $\\kappa$--Minkowski one. Using this star product, following the idea of Padmanabhan, we find the leading order, $1/\\kappa$ correction to the Hawking thermal spectrum.

J. Kowalski-Glikman

2009-07-18

209

Metals in the Intergalactic Medium  

E-print Network

We use high spectral resolution (R=45000) and high signal-to-noise ratio (S/N \\~ 35-70 per pixel) spectra of 19 high-redshift (2.11. Our observations strongly suggest that the CIV/HI ratio decreases with decreasing tau(HI) with log[tau(CIV)]=1.3xlog[tau(HI)]-3.2. We do not detect CIV absorption statistically associated with gas of tau(HI)2.4). Therefore, at the limit of present surveys, the presence of metals in the underdense regions of the IGM is still to be demonstrated.

Bastien Aracil; Patrick Petitjean; Christophe Pichon; Jacqueline Bergeron

2003-07-29

210

Space Telescopes  

NASA Technical Reports Server (NTRS)

Space telescopes have been a dominant force in astrophysics and astronomy over the last two decades. As Lyman Spitzer predicted in 1946, space telescopes have opened up much of the electromagnetic spectrum to astronomers, and provided the opportunity to exploit the optical performance of telescopes uncompromised by the turbulent atmosphere. This special section of Optical Engineering is devoted to space telescopes. It focuses on the design and implementation of major space observatories from the gamma-ray to far-infrared, and highlights the scientific and technical breakthroughs enabled by these telescopes. The papers accepted for publication include reviews of major space telescopes spanning the last two decades, in-depth discussions of the design considerations for visible and x-ray telescopes, and papers discussing concepts and technical challenges for future space telescopes.

Clampin, Mark; Flanagan, Kathryn A.

2012-01-01

211

Probability Spaces  

NSDL National Science Digital Library

Created by Kyle Siegrist of the University of Alabama-Huntsville, this is an online, interactive lesson on probability spaces. The resource provides examples, exercises, and applets that cover conditional probability, independence, and several modes of convergence that are appropriate for random variables. This section also covers probability space, the paradigm of a random experiment and its mathematical model as well as sample spaces, events, random variables, and probability measures. This is the second of seventeen different statistics lessons provided by Siegrist.

Siegrist, Kyle

2009-02-27

212

Spaced Out  

NSDL National Science Digital Library

Students are introduced to the space environment, learning about the major differences between the environment on Earth and that of outer space (atmosphere, radiation, microgravity) â and the engineering challenges that arise because of these differences. To prepare students for the upcoming lessons on the human body, they are challenged to think about how their bodies would change and adapt in the unique environment of space.

Integrated Teaching And Learning Program

213

Personal space  

Microsoft Academic Search

Reviews major findings of personal-space research in clinical psychology, personality, demographic studies (including sex, age, cross-cultural studies), and studies of the effects of familiarity and affinity. The substantial lack of consistent findings in the literature is attributed to the lack of experimental controls in most of the personal-space research. It is suggested that researchers explore personal space using multivariate techniques.

Gary W. Evans; Roger B. Howard

1973-01-01

214

Space antennas  

NASA Astrophysics Data System (ADS)

The design and operation of ground based space communication antennas are generally reviewed. Antenna components, phased arrays, atmospheric attenuation, and characteristic radition patterns are addressed.

Andreyev, V.; Shagov, V.

1982-08-01

215

Space Stations: Beans in Space  

NSDL National Science Digital Library

In this activity, learners perform 20 arm curls with cans that simulate the weight of beans on Earth versus the weights of the same number of beans on the Moon and in space. Learners explore what happens to muscles in space that do not have to fight the force of gravity. This activity station is part of a sequence of stations that can be set up to help learners explore how space affects the human body and why.

Byerly, Diane; Institute, Lunar A.

2006-01-01

216

Space Weather  

E-print Network

Space Weather :: Printer Friendly Version of Article 2004SW000119 http://www.agu magnetic Faraday cages, to designing artificial magnetospheres around the spacecraft, to employing into nature. Louis J. Lanzerotti is Editor of Space Weather, Distinguished Research Professor at the New

Shepherd, Simon

217

Space Debris  

NSDL National Science Digital Library

This Wikipedia article provides information about space debris, the objects in orbit around Earth left over from earlier space missions. The article introduces the history of orbital debris production as well as the growing concern about collisions between this debris and functional satellites. Links provide further information.

2008-02-26

218

Space Microbiology  

PubMed Central

Summary: The responses of microorganisms (viruses, bacterial cells, bacterial and fungal spores, and lichens) to selected factors of space (microgravity, galactic cosmic radiation, solar UV radiation, and space vacuum) were determined in space and laboratory simulation experiments. In general, microorganisms tend to thrive in the space flight environment in terms of enhanced growth parameters and a demonstrated ability to proliferate in the presence of normally inhibitory levels of antibiotics. The mechanisms responsible for the observed biological responses, however, are not yet fully understood. A hypothesized interaction of microgravity with radiation-induced DNA repair processes was experimentally refuted. The survival of microorganisms in outer space was investigated to tackle questions on the upper boundary of the biosphere and on the likelihood of interplanetary transport of microorganisms. It was found that extraterrestrial solar UV radiation was the most deleterious factor of space. Among all organisms tested, only lichens (Rhizocarpon geographicum and Xanthoria elegans) maintained full viability after 2 weeks in outer space, whereas all other test systems were inactivated by orders of magnitude. Using optical filters and spores of Bacillus subtilis as a biological UV dosimeter, it was found that the current ozone layer reduces the biological effectiveness of solar UV by 3 orders of magnitude. If shielded against solar UV, spores of B. subtilis were capable of surviving in space for up to 6 years, especially if embedded in clay or meteorite powder (artificial meteorites). The data support the likelihood of interplanetary transfer of microorganisms within meteorites, the so-called lithopanspermia hypothesis. PMID:20197502

Horneck, Gerda; Klaus, David M.; Mancinelli, Rocco L.

2010-01-01

219

Space Review.  

National Technical Information Service (NTIS)

Human space flight in the US and other space-faring countries is faced with a twin challenge that is likely to persist for many years: flat or declining budgets along with an expectation of continuing, significant achievements. A partial solution may invo...

D. Lester, H. Thronson, S. Hatfield

2011-01-01

220

Collaborative Spaces  

ERIC Educational Resources Information Center

When architects discuss the educational facilities of the next century and beyond, the conversation turns to collaborative spaces. They envision flexible and fluid spaces that will encourage creative and critical thinking, and free students to communicate clearly about the task at hand. While these are admirable ideals, there are some fundamental…

Lippman, Peter C.

2013-01-01

221

Space Contamination  

NASA Astrophysics Data System (ADS)

In 1957, the first man-made satellite, Sputnik 1, was launched into the space. This important event has brought many technological advances and important discoveries for mankind. However a new challenge to mankind has become a reality because of the more than 5,000 satellites that have been launched, a great number of them have stopped operating and remain floating uncontrollably in space and have become space debris. Debris is artificial matter floating uncontrollably in space. Among the debris floating around the Earth, are not just old satellites, but also parts that have broken off spacecraft, paint chips or tiles, gloves that astronauts have dropped - and a multitude of objects. In this paper we present and discuss the impact of artificial space debris.

Dávila, C. R.; Rojas, M.

2002-12-01

222

Space engineering  

NASA Technical Reports Server (NTRS)

Human productivity was studied for extravehicular tasks performed in microgravity, particularly including in-space assembly of truss structures and other large objects. Human factors research probed the anthropometric constraints imposed on microgravity task performance and the associated workstation design requirements. Anthropometric experiments included reach envelope tests conducted using the 3-D Acoustic Positioning System (3DAPS), which permitted measuring the range of reach possible for persons using foot restraints in neutral buoyancy, both with and without space suits. Much neutral buoyancy research was conducted using the support of water to simulate the weightlessness environment of space. It became clear over time that the anticipated EVA requirement associated with the Space Station and with in-space construction of interplanetary probes would heavily burden astronauts, and remotely operated robots (teleoperators) were increasingly considered to absorb the workload. Experience in human EVA productivity led naturally to teleoperation research into the remote performance of tasks through human controlled robots.

Alexander, Harold L.

1991-01-01

223

An Empirical Determination of the Intergalactic Background Light Using Near-infrared Deep Galaxy Survey Data out to 5 ?m and the Gamma-Ray Opacity of the Universe  

NASA Astrophysics Data System (ADS)

We extend our previous model-independent determination of the intergalactic background light, based purely on galaxy survey data, out to a wavelength of 5 ?m. Our approach enables us to constrain the range of photon densities, based on the uncertainties from observationally determined luminosity densities and colors. We further determine a 68% confidence upper and lower limit on the opacity of the universe to ?-rays up to energies of 1.6/(1 + z) TeV. A comparison of our lower limit redshift-dependent opacity curves to the opacity limits derived from the results of both ground-based air Cerenkov telescope and Fermi-LAT observations of PKS 1424+240 allows us to place a new upper limit on the redshift of this source, independent of IBL modeling.

Scully, Sean T.; Malkan, Matthew A.; Stecker, Floyd W.

2014-04-01

224

Space polypropulsion  

NASA Astrophysics Data System (ADS)

Hybrid space propulsion has been a feature of most space missions. Only the very early rocket propulsion experiments like the V2, employed a single form of propulsion. By the late fifties multi-staging was routine and the Space Shuttle employs three different kinds of fuel and rocket engines. During the development of chemical rockets, other forms of propulsion were being slowly tested, both theoretically and, relatively slowly, in practice. Rail and gas guns, ion engines, "slingshot" gravity assist, nuclear and solar power, tethers, solar sails have all seen some real applications. Yet the earliest type of non-chemical space propulsion to be thought of has never been attempted in space: laser and photon propulsion. The ideas of Eugen Saenger, Georgii Marx, Arthur Kantrowitz, Leik Myrabo, Claude Phipps and Robert Forward remain Earth-bound. In this paper we summarize the various forms of nonchemical propulsion and their results. We point out that missions beyond Saturn would benefit from a change of attitude to laser-propulsion as well as consideration of hybrid "polypropulsion" - which is to say using all the rocket "tools" available rather than possibly not the most appropriate. We conclude with three practical examples, two for the next decades and one for the next century; disposal of nuclear waste in space; a grand tour of the Jovian and Saturnian moons - with Huygens or Lunoxod type, landers; and eventually mankind's greatest space dream: robotic exploration of neighbouring planetary systems.

Kellett, B. J.; Griffin, D. K.; Bingham, R.; Campbell, R. N.; Forbes, A.; Michaelis, M. M.

2008-05-01

225

Hubble Space Telescope/Cosmic Origins Spectrograph Observations of the Quasar Q0302-003: Probing the He II Reionization Epoch and QSO Proximity Effects  

NASA Astrophysics Data System (ADS)

Q0302-003 (z = 3.2860 ± 0.0005) was the first quasar discovered that showed a He II Gunn-Peterson trough, a sign of incomplete helium reionization at z >~ 2.9. We present its Hubble Space Telescope/Cosmic Origins Spectrograph far-UV medium-resolution spectrum, which resolves many spectral features for the first time, allowing study of the quasar itself, the intergalactic medium, and quasar proximity effects. Q0302-003 has a harder intrinsic extreme-UV spectral index than previously claimed, as determined from both a direct fit to the spectrum (yielding ?? ? -0.8) and the helium-to-hydrogen ion ratio in the quasar's line-of-sight proximity zone. Intergalactic absorption along this sightline shows that the helium Gunn-Peterson trough is largely black in the range 2.87 < z < 3.20, apart from ionization due to local sources, indicating that helium reionization has not completed at these redshifts. However, we tentatively report a detection of nonzero flux in the high-redshift trough when looking at low-density regions, but zero flux in higher-density regions. This constrains the He II fraction to be about 1% in the low-density intergalactic medium (IGM) and possibly a factor of a few higher in the IGM as a whole, suggesting helium reionization has progressed substantially by z ~ 3.1. The Gunn-Peterson trough recovers to a He II Ly? forest at z < 2.87. We confirm a transmission feature due to the ionization zone around a z = 3.05 quasar just off the sightline, and resolve the feature for the first time. We discover a similar such feature possibly caused by a luminous z = 3.23 quasar further from the sightline, which suggests that this quasar has been luminous for >34 Myr.

Syphers, David; Shull, J. Michael

2014-03-01

226

Space medicine  

NASA Technical Reports Server (NTRS)

This paper attempts to underscore the importance of continued studies on the effects of space on human physiology. With particular reference to the Space Station, it is pointed out that there are two aspects which are challenging to life scientists: first is the development of a research capability for the life sciences which will be used to conduct investigations necessary to extend the time humans can remain in space; second is the challenge to develop a medical capability to provide prevention, diagnosis, and therapy. A discussion of physiological changes that have been observed in spacecrews follows along the lines of the two aspects mentioned.

Pool, Sam L.

1988-01-01

227

Space Weather  

NSDL National Science Digital Library

With three levels to choose from on each page - beginner, intermediate or advanced - this site provides information on Space Weather and the terms scientists use to describe the everchanging conditions in space. Explosions on the Sun create storms of radiation, fluctuating magnetic fields, and swarms of energetic particles. These phenomena travel outward through the Solar System with the solar wind. Upon arrival at Earth, they interact in complex ways with Earth's magnetic field, creating Earth's radiation belts and the Aurora. Some space weather storms can damage satellites, disable electric power grids, and disrupt cell phone communications systems. This site provides images, activities, and interesting facts about all of these events.

2004-02-06

228

Space Shuttle  

NASA Technical Reports Server (NTRS)

A general description of the space shuttle program is presented, with emphasis on its application to the use of space for commercial, scientific, and defense needs. The following aspects of the program are discussed: description of the flight system (orbiter, external tank, solid rocket boosters) and mission profile, direct benefits related to life on earth (both present and expected), description of the space shuttle vehicle and its associated supporting systems, economic impacts (including indirect benefits such as lower inflation rates), listing of participating organizations.

1975-01-01

229

Animated Space  

E-print Network

spaces of Boston and Birmingham, but the ontology of plurality is the same as in Bamako and Bogota, only less visible, more ordered. In both kinds of city, the ecology of public space is rich, 5 its inhabitation germane to sociality and citizenship... is fraught with difficulty. The label conceals more than it reveals, its singularity better a 7 reflection of the predilections of the urban designer keen to engineer a particular place aesthetic or of the urban scholar trained to think public space...

Amin, Ash

2014-01-01

230

Space Sense  

NSDL National Science Digital Library

Another great resource from the University of Michigan's Windows to the Universe Web site is the new Space Science activity. This interactive space trivia game tests your knowledge of space trivia with the goal to boost your rocket ship out of the atmosphere with correct answers. As with other Windows to the Universe resources, users get to choose the difficulty level they'd like to play and even between an adult and kids version of the game. Every question accompanies three answers from which to choose; when a correct answer is chosen, the rocket ship on the screen ascends towards outer space. Perhaps the most useful part of the activity is the "learn more" link that accompanies each answer, providing kids with a wealth of additional information and encouraging them to explore the subject further.

2008-01-03

231

Built space  

E-print Network

This thesis explores the spatial qualities of built environments through observation and design. Recognition that we move through our environment should be reflected in the space we design. Where applicable, a series of ...

Dyer, Daniel Joseph

1984-01-01

232

Space nursing.  

PubMed

Rogers' nursing science of unitary human beings has potential for providing a unique understanding of human life and health in space as well as on Earth. When planning for nursing services beyond the planetary level, we must focus these on people as integrated wholes in mutual process with a radically different environment. The overview effect, as experienced by astronauts and others, suggests that future space inhabitants are precursors of spacekind. PMID:1743064

Barrett, E A

1991-10-01

233

Space science  

NASA Technical Reports Server (NTRS)

A fact sheet on the NASA space science program is presented. Some of the subjects considered include the following: (1) the Orbiting Astronomical Observatory, (2) the Orbiting Solar Observatory, (3) the Small Astronomy Satellite, (4) lunar programs, (5) planetary programs using the Mariner, Pioneer 10, and Viking space probes, and (6) the Scout, Thor-Delta, and Atlas-Centaur launch vehicles. For each program there is a description of the effort, the schedule, management, program officials, and funding aspects in outline form.

1975-01-01

234

Hyperbolic Space  

Microsoft Academic Search

\\u000a This chapter is devoted to the definition of a Riemannian n-manifold Hn called hyperbolic n-space and to the determination of its geometric properties (isometries, geodesies, curvature, etc.). This space is the local model for the class of manifolds we shall deal with in the whole book. The results we are going\\u000a to prove may be found in several texts (e.g.

Riccardo Benedetti; Carlo Petronio

235

Space Resources  

NASA Technical Reports Server (NTRS)

Space resources must be used to support life on the Moon and exploration of Mars. Just as the pioneers applied the tools they brought with them to resources they found along the way rather than trying to haul all their needs over a long supply line, so too must space travelers apply their high technology tools to local resources. The pioneers refilled their water barrels at each river they forded; moonbase inhabitants may use chemical reactors to combine hydrogen brought from Earth with oxygen found in lunar soil to make their water. The pioneers sought temporary shelter under trees or in the lee of a cliff and built sod houses as their first homes on the new land; settlers of the Moon may seek out lava tubes for their shelter or cover space station modules with lunar regolith for radiation protection. The pioneers moved further west from their first settlements, using wagons they had built from local wood and pack animals they had raised; space explorers may use propellant made at a lunar base to take them on to Mars. The concept for this report was developed at a NASA-sponsored summer study in 1984. The program was held on the Scripps campus of the University of California at San Diego (UCSD), under the auspices of the American Society for Engineering Education (ASEE). It was jointly managed under the California Space Inst. and the NASA Johnson Space Center, under the direction of the Office of Aeronautics and Space Technology (OAST) at NASA Headquarters. The study participants (listed in the addendum) included a group of 18 university teachers and researchers (faculty fellows) who were present for the entire 10-week period and a larger group of attendees from universities, Government, and industry who came for a series of four 1-week workshops. The organization of this report follows that of the summer study. Space Resources consists of a brief overview and four detailed technical volumes: (1) Scenarios; (2) Energy, Power, and Transport; (3) Materials; (4) Social Concerns. Although many of the included papers got their impetus from workshop discussions, most have been written since then, thus allowing the authors to base new applications on established information and tested technology. All these papers have been updated to include the authors' current work. This overview, drafted by faculty fellow Jim Burke, describes the findings of the summer study, as participants explored the use of space resources in the development of future space activities and defined the necessary research and development that must precede the practical utilization of these resources. Space resources considered included lunar soil, oxygen derived from lunar soil, material retrieved from near-Earth asteroids, abundant sunlight, low gravity, and high vacuum. The study participants analyzed the direct use of these resources, the potential demand for products from them, the techniques for retrieving and processing space resources, the necessary infrastructure, and the economic tradeoffs. This is certainly not the first report to urge the utilization of space resources in the development of space activities. In fact, Space Resources may be seen as the third of a trilogy of NASA Special Publications reporting such ideas arising from similar studies. It has been preceded by Space Settlements: A Design Study (NASA SP-413) and Space Resources and Space Settlements (NASA SP-428). And other, contemporaneous reports have responded to the same themes. The National Commission on Space, led by Thomas Paine, in Pioneering the Space Frontier, and the NASA task force led by astronaut Sally Ride, in Leadership and America's Future in Space, also emphasize expansion of the space Infrastructure; more detailed exploration of the Moon, Mars, and asteroids; an early start on the development of the technology necessary for using space resources; and systematic development of the skills necessary for long-term human presence in space. Our report does not represent any Government-authorized view or official NASA policy. NASA's official response to these challenging op

McKay, Mary Fae (Editor); McKay, David S. (Editor); Duke, Michael S. (Editor)

1992-01-01

236

Space Debris  

NSDL National Science Digital Library

This Topic in Depth begins with a Web site maintained by Dr. Richard B. Gomez of George Mason University called Space Debris (1). The site is offered as a slide presentation, which explains what space debris is, where it comes from, if it's dangerous, what is known about it, and what can be done about it. The very interesting site is perfect for non-experts because of its simple descriptions and abundance of graphics. The second site from Space.com is an article written by Robert Roy Britt entitled Space Junk: The Stuff Left Behind (2). Visitors can read about the number of objects being tracked (at the time the article was written), what the total weight of these objects is, view a table of the number of various pieces of space junk by country, and even find out it if there is a risk of getting hit in the head by these objects. The next site, Nature's Tiniest Space Junk (3), is offered by NASA's news portal Science@NASA Web site. The page describes how scientists are monitoring tiny dust sized meteoroids that are constantly flying around our planet that have the potential to be quite dangerous. For those really interested, the site lets people listen to audio files of the meteor radar in action. The fourth site on space junk, maintained by the Texas Advanced Computing Center, is a Simulation of Orbital Debris Shielding Performance at High Impact Velocities (4). The page highlights the work of Dr. Eric Fahrenthold, who is simulating orbital debris shielding performance at high impact velocities. A basic description of the work is offered along with the simulation itself, which shows a piece of space debris striking a surface. Next, from NASA's Hazards Assessment Web site, comes the Hypervelocity Impact Test Facility: Orbital Debris and Micrometeoroids (5) page. Readers can find out more on the problem of space junk, why NASA feels its so important to study simulating particle impacts on spacecraft, the lightweight shields that are in place on the International Space Station, and more. The sixth site is an article that appeared in the Bulletin of the Atomic Scientists by Joel Primack called Pelted by Paint, Downed by Debris (6). Although there's not a large amount of content on the site, it does give some interesting information on a different aspect of the subject. The author describes how any missile defense program could be detrimentally affected by space debris and suggests the need for space agencies to take active steps to prevent its buildup. The National Academies Press offers the next site, which is actually an online book on Protecting the Space Station from Meteoroids and Orbital Debris (7). Contents include risk management strategies for the space station, debris modeling, shielding the station, collision warning and avoidance, and more. The last site is from the Aerospace Corporation and its Center for Orbital and Reentry Debris Studies (8). Visitors will find an introduction to the Center, the basics of space debris, what happens during satellite reentry, re-entry data and predictions, additional links, and more.

Brieske, Joel A.

2003-01-01

237

Space Rescue  

NASA Technical Reports Server (NTRS)

Space Rescue has been a topic of speculation for a wide community of people for decades. Astronauts, aerospace engineers, diplomats, medical and rescue professionals, inventors and science fiction writers have all speculated on this problem. Martin Caidin's 1964 novel Marooned dealt with the problems of rescuing a crew stranded in low earth orbit. Legend at the Johnson Space Center says that Caidin's portrayal of a Russian attempt to save the American crew played a pivotal role in convincing the Russians to join the real joint Apollo-Soyuz mission. Space Rescue has been a staple in science fiction television and movies portrayed in programs such as Star Trek, Stargate-SG1 and Space 1999 and movies such as Mission To Mars and Red Planet. As dramatic and as difficult as rescue appears in fictional accounts, in the real world it has even greater drama and greater difficulty. Space rescue is still in its infancy as a discipline and the purpose of this chapter is to describe the issues associated with space rescue and the work done so far in this field. For the purposes of this chapter, the term space rescue will refer to any system which allows for rescue or escape of personnel from situations which endanger human life in a spaceflight operation. This will span the period from crew ingress prior to flight through crew egress postlanding. For the purposes of this chapter, the term primary system will refer to the spacecraft system that a crew is either attempting to escape from or from which an attempt is being made to rescue the crew.

Muratore, John F.

2007-01-01

238

Space.com - Space TV  

NSDL National Science Digital Library

At this site, users can view and download videos on a variety of space-related topics including exploration, astronomy, the Earth, historic moments in exploration, and the search for extraterrestrial life.

239

BBC Space  

NSDL National Science Digital Library

Hosted by the British Broadcasting Corporation (BBC), this site provides comprehensive information about space science. There is the latest news about space findings and issues, and what's happening in the sky for the current month. Galleries show images of the planets, Sunspots, eclipses, auroras, and more. There is a night sky section with observation notes and a constellation guide for learning more about the star patterns. 'Deep Space' covers phenomena such as black holes, wormholes, and dark matter. There is a discussion covering the possibility of life elsewhere, planets outside of our Solar System, and astrobiology. 'Origins' explores the Big Bang, from the first few seconds to the future. 'Cosmology' discusses how our ideas about the Earth and Universe have grown and continue to expand. The stars section illustrates different star types, and the life of stars from birth to death. There is also a section of brief biographies on all astronomers who have contributed to our current knowledge of space, such as Galileo, Copernicus, Ptolemy, Hubble, and many more. There are links to additional sites, as well as space games to play.

240

Space Exploration  

NASA Technical Reports Server (NTRS)

This abstract covers a one hour presentation on Space Exploration. The audience is elementary students; therefore there are few words on the slides, mostly pictures of living and working in space. The presentation opens with a few slides describing a day in the life of a space explorer. It begins with a launch, discussions of day-night cycles, eating, exercising, housekeeping, EVA, relaxation, and sleeping. The next section of the presentation shows photos of astronauts performing experiments on the ISS. Yokomi Elementary School launched this fall with the most advanced educational technology tools available in schools today. The science and technology magnet school is equipped with interactive white boards, digital projectors, integrated sound systems and several computers for use by teachers and students. The only elementary school in Fresno Unified with a science focus also houses dedicated science classrooms equipped specifically for elementary students to experience hands-on science instruction in addition to the regular elementary curriculum.

Davis, Jeffrey R.

2006-01-01

241

Entering Space  

NASA Astrophysics Data System (ADS)

The authors is giving a classification of civilisations depending on the degree of colonisation of the Earth, Solar System and Our Galaxy. The problems of: History of geographic discoveries (The great geographical discoveries during the Middle Age, the concurence of Chinnese and Europeans in this Area); The Astrophysics, such as: Asteroids, Water and Atmosphere on outer planets, Planet Mars Planet, Agriculture on outer planets, Minerals on outer planets; Cosmic flights: Fuels, Robotics, Moon (as an intermediary basis for interplanetary flights), Mars colonisation; Interstellar flights, Space research costs, strategy and tactics of the space colonisation; Policy: War and Peace, International Collaboration are discussed.

Zubrin, Robert

242

Space vehicle  

NASA Technical Reports Server (NTRS)

A space vehicle having an improved ascent configuration for use in traveling in space is presented. Components of the vehicle are: (1) a winged orbiter having an elongater fuselage and rearwardly directed main engines fixed to the fuselage; (2) an elongated tank assembly of an improved configuration disposed forwardly of the fuselage and connected with the main engines of the vehicle for supplying liquid propellants; and (3) a booster stage comprising a pair of integrated solid rocket boosters connected with the orbiter immediately beneath the fuselage and extended in substantial parallelism.

Vonpragenau, G. L. (inventor)

1975-01-01

243

Second Symposium on Space Industrialization. [space commercialization  

NASA Technical Reports Server (NTRS)

The policy, legal, and economic aspects of space industrialization are considered along with satellite communications, material processing, remote sensing, and the role of space carriers and a space station in space industrialization.

Jernigan, C. M. (editor)

1984-01-01

244

Trading Spaces  

ERIC Educational Resources Information Center

Education administrators face the dual dilemma of crowded, aging facilities and tightening capital budgets. The challenge is to build the necessary classroom, laboratory and activity space while minimizing the length and expense of the construction process. One solution that offers an affordable alternative is modular construction, a method that…

Cort, Cliff

2006-01-01

245

Space languages  

NASA Technical Reports Server (NTRS)

Applications of linguistic principles to potential problems of human and machine communication in space settings are discussed. Variations in language among speakers of different backgrounds and change in language forms resulting from new experiences or reduced contact with other groups need to be considered in the design of intelligent machine systems.

Hays, Dan

1987-01-01

246

Appealing Spaces  

ERIC Educational Resources Information Center

For more than a decade, educators and designers have been moving tentatively into uncharted waters. This article reports that administrators, faculty, and planners now recognize that learning spaces should be developed for reasons beyond utilization numbers. With declining retention and graduation rates, education institutions are acknowledging…

Dittoe, William; Porter, Nat

2007-01-01

247

Training Spaces  

ERIC Educational Resources Information Center

Creating a balanced learning space for employees is about more than trying different types of seating. It is a challenge that an affect how well employees absorb the lessons and whether they will be able to product better results for the company. The possible solutions are as diverse as the learners. This article describes how three companies…

Weinstein, Margery

2010-01-01

248

Inherit Space  

NASA Technical Reports Server (NTRS)

The objective of the proposed research was to begin development of a unique educational tool targeted at educating and inspiring young people 12-16 years old about NASA and the Space Program. Since these young people are the future engineers, scientists and space pioneers, the nurturing of their enthusiasm and interest is of critical importance to the Nation. This summer the basic infrastructure of the tool was developed in the context of an educational game paradigm. The game paradigm has achieved remarkable success in maintaining the interest of young people in a self-paced, student-directed learning environment. This type of environment encourages student exploration and curiosity which are exactly the traits that future space pioneers need to develop to prepare for the unexpected. The Inherit Space Educational Tool is an open-ended learning environment consisting of a finite-state machine classic adventure game paradigm. As the young person explores this world, different obstacles must be overcome. Rewards will be offered such as using the flight simulator to fly around and explore Titan. This simulator was modeled on conventional Earth flight simulators but has been considerably enhanced to add texture mapping of Titan's atmosphere utilizing the latest information from the NASA Galileo Space Probe. Additional scenery was added to provide color VGA graphics of a futuristic research station on Titan as well as an interesting story to keep the youngster's attention. This summer the game infrastructure has been developed as well as the Titan Flight Simulator. A number of other enhancements are planned.

Giarratano, Joseph C.; Jenks, K. C.

1997-01-01

249

Southern Spaces  

NSDL National Science Digital Library

Exploring the American South is a splendid idea, and this online journal is a great way to think about the "real and imagined places" of this unique cultural region. Southern Spaces is a peer-reviewed Internet journal and forum that "provides open access to essays, interviews and performances, events and conferences, gateways, timescapes, and annotated links about real and imagined spaces and places of the U.S. South." Their work is supported by the Robert W. Woodruff Library of Emory University, and visitors will want to browse around the site more than once. First-time visitors may wish to start by looking at interactive features like "Negotiating Gender Lines: Women's Movement across Atlanta Mosques" and "The Other Side of Paradise: Glimpsing Slavery in the University's Utopian Landscapes". The site also includes information about the journal's editorial board and a set of thematically organized weblinks.

250

Communication spaces  

PubMed Central

Background and objective Annotations to physical workspaces such as signs and notes are ubiquitous. When densely annotated, work areas become communication spaces. This study aims to characterize the types and purpose of such annotations. Methods A qualitative observational study was undertaken in two wards and the radiology department of a 440-bed metropolitan teaching hospital. Images were purposefully sampled; 39 were analyzed after excluding inferior images. Results Annotation functions included signaling identity, location, capability, status, availability, and operation. They encoded data, rules or procedural descriptions. Most aggregated into groups that either created a workflow by referencing each other, supported a common workflow without reference to each other, or were heterogeneous, referring to many workflows. Higher-level assemblies of such groupings were also observed. Discussion Annotations make visible the gap between work done and the capability of a space to support work. Annotations are repairs of an environment, improving fitness for purpose, fixing inadequacy in design, or meeting emergent needs. Annotations thus record the missing information needed to undertake tasks, typically added post-implemented. Measuring annotation levels post-implementation could help assess the fit of technology to task. Physical and digital spaces could meet broader user needs by formally supporting user customization, ‘programming through annotation’. Augmented reality systems could also directly support annotation, addressing existing information gaps, and enhancing work with context sensitive annotation. Conclusions Communication spaces offer a model of how work unfolds. Annotations make visible local adaptation that makes technology fit for purpose post-implementation and suggest an important role for annotatable information systems and digital augmentation of the physical environment. PMID:24005797

Coiera, Enrico

2014-01-01

251

Open Spaces  

NSDL National Science Digital Library

Featuring articles by leading experts on topics from science policy to ecology (such as Bruce Babbitt and Jane Lubchenko), this new publication from Portland, Oregon attempts to incorporate synthetic, broad perspectives with a host of (familiar) environmental topics. A subscription fee is required to access all articles at the Open Spaces Website, but several interesting sample articles are currently posted for free online viewing. Science writers and scientists interested in widening their perspectives will find this an intriguing resource.

252

Narrative Spaces  

Microsoft Academic Search

Game designers don’t simply tell stories; they design worlds and sculpt spaces. It is no accident, for example, that game\\u000a designers have historically been more interested in issues of level design than of plot or character motivation. A prehistory\\u000a of video and computer games might take us through the evolution of paper mazes or board games, both preoccupied with the

Henry Jenkins

253

Sobolev spaces  

Microsoft Academic Search

i.j=l a~i Oxj Oxi it is clear that Vu c L 2 and u e L 2 are sufficient conditions for the integrals to be well-defined. In addition, when you seek to minimize the functional thus arising (Dirichlet's principle for the Laplacian), they are the natural complete spaces to which the sought after minimizers belong. This allows existence to be

Raymond Johnson; V. G. Maz; T. O. Shaposhnikova

1987-01-01

254

America plans for space  

SciTech Connect

Contents include: pursuing a balanced space program; the space defense initiative; warfare in space; the lunar laboratory; the role of space in preserving the peace; living off the land - the use of resources in space for future civilian space operations; the military uses of space; C3I(command control communications and intelligence); aspects of space technology; arms control in space: preserving critical strategic space systems without weapons in space; space and arms control: a skeptical view; options for space arms control; space arms control.

Not Available

1986-01-01

255

Space Research Centre Space Research Centre  

E-print Network

Space Research Centre Space Research Centre www.src.le.ac.uk #12;2 University of Leicester � DeLivering over five DecaDes of space science anD instrUmentation expertise... Welcome to the SRC The Space Research Centre's (SRC) programme has two main foci: the Space Science and Instrumentation (SSI) Group

Hinton, Jim

256

Open Spaces  

NSDL National Science Digital Library

Recently, the U.S. Fish & Wildlife Service created the "Open Spaces" blog to showcase some of their wildlife refuges and to offer the general public an inside view on the day-to-day operations of the organization. Visitors to the site will find blog posts that profile their work in the Everglades, reflections on September 11th, migratory birds, and the Labrador retrievers that work at the Kenai National Wildlife Refuge in Alaska. Users of the site can search posts by category, and they will find that each entry also contains a selection of links to other materials, such as park management plans and lesson plans. Finally, visitors can also use the social media buttons here to share each post on Twitter and Facebook.

257

Swedish Space Corporation (SSC)  

NASA Astrophysics Data System (ADS)

Located in Solna, near Stockholm. SSC is a government-owned commercial company with activities covering space systems engineering, space operations and the commercial exploitation of space. SSC also offers support and technical expertise to the National Swedish Space Board....

Murdin, P.

2000-11-01

258

Swedish Space Corporation (SSC)  

Microsoft Academic Search

Located in Solna, near Stockholm. SSC is a government-owned commercial company with activities covering space systems engineering, space operations and the commercial exploitation of space. SSC also offers support and technical expertise to the National Swedish Space Board....

P. Murdin

2000-01-01

259

Esrange Space Center, a Gate to Space  

Microsoft Academic Search

Swedish Space Corporation (SSC) is operating the Esrange Space Center in northern Sweden. Space operations have been performed for more than 40 years. We have a unique combination of maintaining balloon and rocket launch operations, and building payloads, providing space vehicles and service systems. Sub-orbital rocket flights with land recovery and short to long duration balloon flights up to weeks

Ola Widell

2008-01-01

260

COMMERCIAL SPACE ACCOMPLISHMENTS Commercial Cargo Space Accomplishments  

E-print Network

11/13/2013 COMMERCIAL SPACE ACCOMPLISHMENTS Commercial Cargo Space Accomplishments The Obama Administration's ambitious commercial space program, which has bipartisan support in Congress, has enabled NASA NASA does business, helping build a strong American commercial space industry, and freeing the agency

Waliser, Duane E.

261

3741SPACE AUDIT PROCEDURE Space audit  

E-print Network

Page 1 3741SPACE AUDIT PROCEDURE Space audit identified to be conducted Will audit disrupt or disturb occupants of the space Notify Faculty, School or Business Unit of the audit Is the audit for timetabling purposes Is the audit a physical audit Confirm audit requirements Is the audit for other space

262

UNIVERSITY SPACE POLICY ALLOCATION OF UNIVERSITY SPACE  

E-print Network

UNIVERSITY COLLEGE DUBLIN UNIVERSITY SPACE POLICY #12;ALLOCATION OF UNIVERSITY SPACE I Purpose To provide a methodology for the allocation of space across the University II Background Due to the university's success in attracting research funding, the need for space and facilities has grown

263

Equally Spaced?  

NSDL National Science Digital Library

Urbanologists and other types have been interested in the interactions between different groups of people in cities for hundreds of years. There is quite a broad literature on studying different types of communities and public spaces, and this recent paper from the Demos group in the United Kingdom adds to that body of work. This 40-page report was first published in July 2007, and it was authored by Hannah Lownsbrough and Joost Beunderman. As the report's subtitle suggests, it is primarily concerned with presenting a dynamic look at how public places can effectively encourage interaction between diverse communities in urban areas. For this work, the researchers looked at three separate locations in Britain, and this report presents some of their findings on what works well (and not so well) in terms of creating and maintaining high-quality public places. The report is both thoughtful and thorough, and persons with an interest in urban planning, sociology, and related fields will find it quite compelling.

Beunderman, Joost; Lownsbrough, Hannah

2007-07-01

264

Planetary Science Space Physics  

E-print Network

bring together space science, space technology, and the education of the next generation of space space science with hardware design, development, implementation, mission operations, and data management is almost one-of-a-kind among university-based space centers. With up to a dozen space science flight

Mojzsis, Stephen J.

265

Space physiology and medicine  

SciTech Connect

The state of knowledge in space physiology and medicine are reviewed. Overviews of manned space flight, the space environment, spaceflight systems and procedures, physiological adaptation to space flight, health maintenance of space crew members, and medical problems of space flight are presented.

Nicogossian, A.E.; Parker J.F. Jr.

1982-01-01

266

Space habitats. [prognosis for space colonization  

NASA Technical Reports Server (NTRS)

Differences between space industrialization and space colonization are outlined along with the physiological, psychological, and esthetic needs of the inhabitants of a space habitat. The detrimental effects of zero gravity on human physiology are reviewed, and the necessity of providing artificial gravity, an acceptable atmosphere, and comfortable relative humidity and temperature in a space habitat is discussed. Consideration is also given to social organization and governance, supply of food and water, and design criteria for space colonies.

Johnson, R. D.

1978-01-01

267

"Space, the Final Frontier"; Books on Space and Space Exploration.  

ERIC Educational Resources Information Center

Advocates play in a child's life. Describes how science fiction seizes the imaginations of young readers with its tales of the future and of outer space. Talks about various nonfiction books about space. Elaborates a workshop on books about space exploration. Gives 10 questions about stimulating student response. (PA)

Jordan, Anne Devereaux

1997-01-01

268

8 Meter Advanced Technology Large-Aperture Space Telescope (ATLAST-8m)  

NASA Technical Reports Server (NTRS)

ATLAST-8m (Advanced Technology Large Aperture Space Telescope) is a proposed 8-meter monolithic UV/optical/NIR space observatory (wavelength range 110 to 2500 nm) to be placed in orbit at Sun-Earth L2 by NASA's planned Ares V heavy lift vehicle. Given its very high angular resolution (15 mas @ 500 nm), sensitivity and performance stability, ATLAST-8m is capable of achieving breakthroughs in a broad range of astrophysics including: Is there life elsewhere in the Galaxy? An 8-meter UVOIR observatory has the performance required to detect habitability (H2O, atmospheric column density) and biosignatures (O2, O3, CH4) in terrestrial exoplanet atmospheres, to reveal the underlying physics that drives star formation, and to trace the complex interactions between dark matter, galaxies, and intergalactic medium. The ATLAST Astrophysics Strategic Mission Concept Study developed a detailed point design for an 8-m monolithic observatory including optical design; structural design/analysis including primary mirror support structure, sun shade and secondary mirror support structure; thermal analysis; spacecraft including structure, propulsion, GN&C, avionics, power systems and reaction wheels; mass and power budgets; and system cost. The results of which were submitted by invitation to NRC's 2010 Astronomy & Astrophysics Decadal Survey.

Stahl, H. Philip

2010-01-01

269

Studying Galaxy Formation and Reionization with the James Webb Space Telescope  

NASA Technical Reports Server (NTRS)

The deepest optical to infrared observations of the universe include the Hubble Deep Fields, the Great Observatories Origins Deep Survey and the recent Hubble Ultra-Deep Field. Galaxies are seen in these surveys at redshifts z>6, less than 1 Gyr after the Big Bang, at the end of a period when light from the galaxies has reionized Hydrogen in the inter-galactic medium. These observations, combined with theoretical understanding, indicate that the first stars and galaxies formed at z>10, beyond the reach of the Hubble and Spitzer Space Telescopes. To observe the first galaxies, NASA is planning the James Webb Space Telescope (JWST), a large (6.5m), cold (<50K), infrared-optimized observatory to be launched early in the next decade into orbit around the second Earth- Sun Lagrange point. JWST will have four instruments: The Near-Infrared Camera, the Near-Infrared multi-object Spectrograph, and the Tunable Filter Imager will cover the wavelength range 0.6 to 5 microns, while the Mid-Infrared Instrument will do both imaging and spectroscopy from 5 to 28.5 microns. I will review the current status of the project.

Gardner, Jonathan P.

2008-01-01

270

Studying Galaxy Formation with the Hubble, Spitzer and James Webb Space Telescopes  

NASA Technical Reports Server (NTRS)

The deepest optical to infrared observations of the universe include the Hubble Deep Fields, the Great Observatories Origins Deep Survey and the recent Hubble Ultra-Deep Field. Galaxies are seen in these surveys at redshifts z>6, less than 1 Gyr after the Big Bang, at the end of a period when light from the galaxies has reionized Hydrogen in the inter-galactic medium. These observations, combined with theoretical understanding, indicate that the first stars and galaxies formed at z>10, beyond the reach of the Hubble and Spitzer Space Telescopes. To observe the first galaxies, NASA is planning the James Webb Space Telescope (JWST), a large (6.5m), cold (<50K), infrared-optimized observatory to be launched early in the next decade into orbit around the second Earth- Sun Lagrange point. JWST will have four instruments: The Near-Infrared Camera, the Near-Infrared multi-object Spectrograph, and the Tunable Filter Imager will cover the wavelength range 0.6 to 5 microns, while the Mid-Infrared Instrument will do both imaging and spectroscopy from 5 to 28.5 microns. In addition to JWST's ability to study the formation and evolution of galaxies, I will also briefly review its expected contributions to studies of the formation of stars and planetary systems.

Gardner, Jonathan P.

2007-01-01

271

Studying Galaxy Formation with the Hubble, Spitzer and James Webb Space Telescopes  

NASA Technical Reports Server (NTRS)

The deepest optical to infrared observations of the universe include the Hubble Deep Fields, the Great Observatories Origins Deep Survey and the recent Hubble Ultra-Deep Field. Galaxies are seen in these surveys at redshifts 2x3, less than 1 Gyr after the Big Bang, at the end of a period when light from the galaxies has reionized Hydrogen in the inter-galactic medium. These observations, combined with theoretical understanding, indicate that the first stars and galaxies formed at z>lO, beyond the reach of the Hubble and Spitzer Space Telescopes. To observe the first galaxies, NASA is planning the James Webb Space Telescope (JWST), a large (6.5m), cold (<50K), infrared-optimized observatory to be launched early in the next decade into orbit around the second Earth- Sun Lagrange point. JWST will have four instruments: The Near-Infrared Camera, the Near-Infrared multi-object Spectrograph, and the Tunable Filter Imager will cover the wavelength range 0.6 to 5 microns, while the Mid-Infrared Instrument will do both imaging and spectroscopy from 5 to 28.5 microns. In addition to JWST's ability to study the formation and evolution of galaxies, I will also briefly review its expected contributions to studies of the formation of stars and planetary systems.

Gardner, Jonathan P.

2007-01-01

272

The Swedish space program  

Microsoft Academic Search

The main Swedish space organizations and projects are briefly reviewed. The main responsibilities of the Swedish National Space Board and Swedish Space Corporation are outlined and the government space budget is presented for fiscal years 1987-1990. The main objectives of the Swedish national scientific program are listed in their relationship to space efforts, and the participating institutes are given. The

Arne Helger

1990-01-01

273

Definitions Numbered Space  

E-print Network

Definitions · Numbered Space ­ a single space marked with a number and reserved for a single permit 24/7 · Unnumbered Space ­ a space which can be used by any customer allowed to park in that lot. High Low Average Question 4: If I buy a staff permit for an UNNUMBERED* space in a non-gated surface

Behmer, Spencer T.

274

CRYSTALLOGRAPHIC POINT AND SPACE  

E-print Network

CRYSTALLOGRAPHIC POINT AND SPACE GROUPS Andy Elvin June 10, 2013 #12;Contents Point and Space no reflection axes #12;Cube and Octahedron are dual Symmetries under Oh #12;Space Groups Subgroups of E(3) Point Group + Translation { R | 0 }{ E | t }a = { R | t }a = Ra + t 230 Space Groups 73 symmorphic space

California at Santa Cruz, University of

275

Life in Space: The International Space Station  

NSDL National Science Digital Library

Students are introduced to the International Space Station (ISS) with information about its structure, operation and key experiments. The ISS itself is an experiment in international cooperation to explore the potential for humans to live in space. The space station features state-of-the-art science and engineering laboratories to conduct research in medicine, materials and fundamental science to benefit people on Earth as well as people who will live in space in the future.

Integrated Teaching And Learning Program

276

Space Science and Marshall Space Flight Center  

NASA Technical Reports Server (NTRS)

Space Science a t Marshall Space Flight Center is diverse and very interesting. It ranges from high energy astrophysics to astrobiology, from solar physics to space weather to dusty plasmas. I will present some of the more interesting investigations regarding auroral physics, what it takes to build a space camera, and laboratory investigations of dust. There will be time for questions and answers at the conclusion.

Spann, James

2005-01-01

277

Space history, space policy, and executive leadership  

NASA Technical Reports Server (NTRS)

A lecture that attempts to establish the role of space historians in formulating space policy is presented. The discussion focusses on two adages and their relevance to space policy. The adages are as follows: 'write about what you know;' and 'good managers do things right; good executives do the right things.'

Kraemer, Sylvia K.

1993-01-01

278

Space-to-Space Communications System  

NASA Technical Reports Server (NTRS)

The Space-to-Space Communications System (SSCS) is an Ultra High Frequency (UHF) Time-Division-Multiple Access (TDMA) system that is designed, developed, and deployed by the NASA Johnson Space Center (JSC) to provide voice, commands, telemetry and data services in close proximity among three space elements: International Space Station (ISS), Space Shuttle Orbiter, and Extravehicular Mobility Units (EMU). The SSCS consists of a family of three radios which are, Space-to-Space Station Radio (SSSR), Space-to-Space Orbiter Radio (SSOR), and Space-to-Space Extravehicular Mobility Radio (SSER). The SSCS can support up to five such radios at a time. Each user has its own time slot within which to transmit voice and data. Continuous Phase Frequency Shift Keying (CPFSK) carrier modulation with a burst data rate of 695 kbps and a frequency deviation of 486.5 kHz is employed by the system. Reed-Solomon (R-S) coding is also adopted to ensure data quality. In this paper, the SSCS system requirements, operational scenario, detailed system architecture and parameters, link acquisition strategy, and link performance analysis will be presented and discussed

Tu, Kwei; Gaylor, Kent; Vitalpur, Sharada; Sham, Cathy

1999-01-01

279

World Space Week: Linking Space and Humanity  

NASA Astrophysics Data System (ADS)

World Space Week, October 4-10 annually, is an international celebration of the contribution that space science and technology makes to the betterment of the human condition. Since its official declaration in 1999 by the United Nation, World Space Week has rapidly grown to include over 40 nations. The dates of World Space Week commemorate key milestones in space. October 4, 1957 was the launch date of Sputnik I, the first artificial Earth satellite. The Outer Space Treaty took effect on October 10, 1967. During World Space Week, participants such as government agencies, companies, science museums, teachers, and individuals organize public events, school activities, and Web-based programs related to space. So many synchronized events attract media coverage which reaches a global audience about space. In this way, World Space Week truly links space and humanity. The global organization of World Space Week is discussed as well as the results to date. The benefits of participation and opportunities to do so also identified.

Stone, D.

2002-01-01

280

SPACE THINKS? Sociological concepts of space  

Microsoft Academic Search

Space Thinks - on the one hand, this title refers to the possibility of understanding space as something more that just the background against which societal developments take place and of granting the term 'space' a dynamic of its own. On the other hand, the title also plays on the phonetic similarity to the name of another central concept in

Sergej Stoetzer

281

The partnership: Space shuttle, space science, and space station  

NASA Technical Reports Server (NTRS)

An overview of the NASA Space Station Program functions, design, and planned implementation is presented. The discussed functions for the permanently manned space facility include: (1) development of new technologies and related commercial products; (2) observations of the Earth and the universe; (3) provision of service facilities for resupply, maintenance, upgrade and repair of payloads and spacecraft; (4) provision of a transportation node for stationing, processing and dispatching payloads and vehicles; (5) provision of manufacturing and assembly facilities; (6) provision of a storage depot for parts and payloads; and (7) provision of a staging base for future space endeavors. The fundamental concept for the Space Station, as given, is that it be designed, operated, and evolved in response to a broad variety of scientific, technological, and commercial user interests. The Space Shuttle's role as the principal transportation system for the construction and maintenance of the Space Station and the servicing and support of the station crew is also discussed.

Culbertson, Philip E.; Freitag, Robert F.

1989-01-01

282

International Space Apps Challenge  

NASA Video Gallery

During the 2013 Space Apps Challenge, space enthusiasts with diverse backgrounds gathered April 20-21 for a collaborative, global problem-solving effort. Held at Kennedy Space Center Visitor Comple...

283

Space Solar Power Program  

SciTech Connect

Information pertaining to the Space Solar Power Program is presented on energy analysis; markets; overall development plan; organizational plan; environmental and safety issues; power systems; space transportation; space manufacturing, construction, operations; design examples; and finance.

Arif, H.; Barbosa, H.; Bardet, C.; Baroud, M.; Behar, A.; Berrier, K.; Berthe, P.; Bertrand, R.; Bibyk, I.; Bisson, J.; Bloch, L.; Bobadilla, G.; Bourque, D.; Bush, L.; Carandang, R.; Chiku, T.; Crosby, N.; De Seixas, M.; De Vries, J.; Doll, S.; Dufour, F.; Eckart, P.; Fahey, M.; Fenot, F.; Foeckersperger, S.; Fontaine, J.E.; Fowler, R.; Frey, H.; Fujio, H.; Gasa, J.M.; Gleave, J.; Godoe, J.; Green, I.; Haeberli, R.; Hanada, T.; Ha

1992-08-01

284

Space art and education  

NASA Astrophysics Data System (ADS)

Space Art has been a growing activity in Europe and in the USA since the end of the 70'ies. With space exploration, space programmes and activities have constantly become a source of inspiration and ideas, particularly suitable for art.

Comte, Pierre; Lipsey, Sharon; Willekens, Philippe

285

Quantum Complex Minkowski Space  

E-print Network

The complex Minkowski phase space has the physical interpretation of the phase space of the scalar massive conformal particle. The aim of the paper is the construction and investigation of the quantum complex Minkowski space.

Grzegorz Jakimowicz; Anatol Odzijewicz

2005-05-06

286

Sculpting space through sound  

E-print Network

How does one experience space? What kind of information do humans collect in the process of constructing space in their mind? How does one begin to understand volume, light, texture, material, smell and sense of space? The ...

Nakagawa, Junko, 1975-

2002-01-01

287

The International Space Station in Space Exploration  

NASA Technical Reports Server (NTRS)

The International Space Station (ISS) Program has many lessons to offer for the future of space exploration. Among these lessons of the ISS Program, three stand out as instrumental for the next generation of explorers. These include: 1) resourcefulness and the value of a strong international partnership; 2) flexibility as illustrated by the evolution of the ISS Program and 3) designing with dissimilar redundancy and simplicity of sparing. These lessons graphically demonstrate that the ISS Program can serve as a test bed for future programs. As the ISS Program builds upon the strong foundation of previous space programs, it can provide insight into the prospects for continued growth and cooperation in space exploration. As the capacity for spacefaring increases worldwide and as more nations invest in space exploration and space sector development, the potential for advancement in space exploration is unlimited. By building on its engineering and research achievements and international cooperation, the ISS Program is inspiring tomorrow s explorers today.

Gerstenmaier, William H.; McKay, Meredith M.

2006-01-01

288

Spaced Retrieval: Absolute Spacing Enhances Learning Regardless of Relative Spacing  

Microsoft Academic Search

Repeated retrieval enhances long-term retention, and spaced repetition also enhances retention. A question with practical and theoretical significance is whether there are particular schedules of spaced retrieval (e.g., gradually expanding the interval between tests) that produce the best learning. In the present experiment, subjects studied and were tested on items until they could recall each one. They then practiced recalling

Jeffrey D. Karpicke; Althea Bauernschmidt

2011-01-01

289

In Outer Space without a Space Suit?  

E-print Network

The author proposes and investigates his old idea - a living human in space without the encumbrance of a complex space suit. Only in this condition can biological humanity seriously attempt to colonize space because all planets of Solar system (except the Earth) do not have suitable atmospheres. Aside from the issue of temperature, a suitable partial pressure of oxygen is lacking. In this case the main problem is how to satiate human blood with oxygen and delete carbonic acid gas (carbon dioxide). The proposed system would enable a person to function in outer space without a space suit and, for a long time, without food. That is useful also in the Earth for sustaining working men in an otherwise deadly atmosphere laden with lethal particulates (in case of nuclear, chemical or biological war), in underground confined spaces without fresh air, under water or a top high mountains above a height that can sustain respiration.

Bolonkin, Alexander

2008-01-01

290

Space Toxicology: Human Health during Space Operations  

NASA Technical Reports Server (NTRS)

Space Toxicology is a unique and targeted discipline for spaceflight, space habitation and occupation of celestial bodies including planets, moons and asteroids. Astronaut explorers face distinctive health challenges and limited resources for rescue and medical care during space operation. A central goal of space toxicology is to protect the health of the astronaut by assessing potential chemical exposures during spaceflight and setting safe limits that will protect the astronaut against chemical exposures, in a physiologically altered state. In order to maintain sustained occupation in space on the International Space Station (ISS), toxicological risks must be assessed and managed within the context of isolation continuous exposures, reuse of air and water, limited rescue options, and the need to use highly toxic compounds for propulsion. As we begin to explore other celestial bodies in situ toxicological risks, such as inhalation of reactive mineral dusts, must also be managed.

Khan-Mayberry, Noreen; James, John T.; Tyl, ROchelle; Lam, Chiu-Wing

2010-01-01

291

Space vehicle propulsion systems: Environmental space hazards  

NASA Technical Reports Server (NTRS)

The hazards that exist in geolunar space which may degrade, disrupt, or terminate the performance of space-based LOX/LH2 rocket engines are evaluated. Accordingly, a summary of the open literature pertaining to the geolunar space hazards is provided. Approximately 350 citations and about 200 documents and abstracts were reviewed; the documents selected give current and quantitative detail. The methodology was to categorize the various space hazards in relation to their importance in specified regions of geolunar space. Additionally, the effect of the various space hazards in relation to spacecraft and their systems were investigated. It was found that further investigation of the literature would be required to assess the effects of these hazards on propulsion systems per se; in particular, possible degrading effects on exterior nozzle structure, directional gimbals, and internal combustion chamber integrity and geometry.

Disimile, P. J.; Bahr, G. K.

1990-01-01

292

In Outer Space without a Space Suit?  

E-print Network

The author proposes and investigates his old idea - a living human in space without the encumbrance of a complex space suit. Only in this condition can biological humanity seriously attempt to colonize space because all planets of Solar system (except the Earth) do not have suitable atmospheres. Aside from the issue of temperature, a suitable partial pressure of oxygen is lacking. In this case the main problem is how to satiate human blood with oxygen and delete carbonic acid gas (carbon dioxide). The proposed system would enable a person to function in outer space without a space suit and, for a long time, without food. That is useful also in the Earth for sustaining working men in an otherwise deadly atmosphere laden with lethal particulates (in case of nuclear, chemical or biological war), in underground confined spaces without fresh air, under water or a top high mountains above a height that can sustain respiration.

Alexander Bolonkin

2008-06-24

293

Achievements in space robotics  

Microsoft Academic Search

Outer space is an ultimate field for the application of robotics technology. As outer space is a harsh environment with extreme temperatures, vacuum, radiation, gravity, and great distances, human access is very difficult and hazardous and is therefore limited. To assist human activities in space for constructing and maintaining space modules and structures, robotic manipulators have been playing essential roles

Kazuya Yoshida

2009-01-01

294

SPACEWAR WIRE MILITARY SPACE  

E-print Network

TERRORWARS SPACEDAILY TERRADAILY MARSDAILY SPACE TRAVEL SPACEMART SPACE DATABASE Endangered Species WeCHANNELS SPACEWAR WIRE MILITARY SPACE UAV NEWS MILITARY COMMS CYBERWARS MISSILE NEWS RAYGUNS against Kashmiri militants SPACEDAILY NEWS Jan 29, 2004 NASA chief defends Bush's space plans Japan

295

astronautics & space technology  

E-print Network

of molecular interaction and space robotics will likely change the way we travel in space. ProgrAmS AVAil28 astronautics & space technology aste overview · programs available courses of instruction · flowcharts Astronautical engineers design, build and operate space vehicles used in exploration

Rohs, Remo

296

Using space resources  

NASA Technical Reports Server (NTRS)

The topics covered include the following: reducing the cost of space exploration; the high cost of shipping; lunar raw materials; some useful space products; energy from the moon; ceramic, glass, and concrete construction materials; mars atmosphere resources; relationship to the Space Exploration Initiative (SEI); an evolutionary approach to using space resources; technology development; and oxygen and metal coproduction.

Sullivan, Thomas A.; Mckay, David S.

1991-01-01

297

The Swedish space programme  

Microsoft Academic Search

The Swedish National Space Board (SNSB) under the Ministry of Industry is the central governmental agency responsible for the goverment-funded Swedish national and international space and remote sensing activities. The technical implementation is mainly contracted by the Board to the state-owned Swedish Space Corporation (SSC). International cooperation is a cornerstone in the Swedish space activities, absorbing more than 80% of

Arne Helger

1992-01-01

298

Budgeting Academic Space  

ERIC Educational Resources Information Center

There are many articles about space management, including those that discuss space calculations, metrics, and categories. Fewer articles discuss the space budgeting processes used by administrators to allocate space. The author attempts to fill this void by discussing her administrative experiences with Middle Tennessee State University's (MTSU)…

Harris, Watson

2011-01-01

299

The Indian Space Program  

NASA Technical Reports Server (NTRS)

The Indian Space program aimed at providing operation space services in communications and remote sensing and using state-of-the-art space technologies is reviewed. Emphasis is placed on the development and operation of satellites and launch vehicles for providing these space services.

Talapatra, Dipak C.

1993-01-01

300

Project Space Vision  

NASA Astrophysics Data System (ADS)

Project Space Vision attempts to document the visions of a new generation of international space professionals for the long-term future of space activities. This voluntary effort was initiated as an independent response from the young space community to an invitation to provide direct input to the Long Term Space Policy Committee of the European Space Agency. By using modern communications tools in the form of the Internet, the World Wide Web and the ISUnet, calls for contributions could reach several thousands of potential contributors within a few weeks time. In return, contributions in the form of survey responses and concise papers were received internationally from young professionals within space agencies, space industry, universities and other organisations. The dominating fundamental reasons for future space activities were found in the areas of services to humankind, scientific progress and exploration. Main perceived barriers were lack of public and political support and high cost of access to space. Other main results include drastic overestimates by the contributors regarding the relative magnitude of spending on space activities. This paper describes the specifics of Project Space Vision and provides an analysis of the fundamental motivations for space activities in our generation as seen by the reached representatives of an emerging space community. The ideas, proposals and suggestions for future space activities are condensed into five specific areas of recommendations followed by general conclusions. Final recommendations are expressed in the form of a space policy in three steps, supported by the general spirit of the contributors.

Edin, P.; Baker, A.; Breitfellner, M.; Debouzy, S.; Fatelnig, P.; Figa, J.; Gilson, P.; Norstrom, J.; Postema, R.; Spiero, F.; Vignelles, A.

1996-01-01

301

Space Shuttle Program Status  

E-print Network

1 Space Shuttle Program Status John Casper Associate Manager Space Shuttle Program September 13, 2010 NAC Space Operations Committee #12;2 Operations #12;3 Flown Manifest March 2009 ­ May 2010 #12, 2010 · 132nd Space Shuttle mission · 32nd Flight of Atlantis (120,650,907 statute miles) · 294 Total

Waliser, Duane E.

302

Space Complexity Algorithms & Complexity  

E-print Network

Space Complexity Algorithms & Complexity Space Complexity Nicolas Stroppa Patrik Lambert - plambert@computing.dcu.ie CA313@Dublin City University. 2008-2009. December 4, 2008 #12;Space Complexity Hierarchy of problems #12;Space Complexity NP-intermediate Languages If P = NP, then are there languages which neither in P

Way, Andy

303

Section 2: The Space of Media Space  

Microsoft Academic Search

We began our study of media space with the social aspects of mediated communication because many in the computer-supported\\u000a cooperative work (CSCW) realm are familiar with models, theories, frameworks, issues, and design approaches related to sociality.\\u000a But the first media space research came from another set of traditions — the ordering of space and the making of place. Formally,\\u000a these

Steve Harrison

2009-01-01

304

Space educators' handbook  

NASA Technical Reports Server (NTRS)

The Space Educators' Handbook is a collection of space exploration information available on Hypercard as a space education reference book. Ranging from early dreams of space ships to current manned missions, the more than four thousand cards include entries of statistics, historical facts and anecdotes, technical articles, accounts of NASA missions from Mercury through the space shuttle, biographical information on women and men who have contributed to space exploration, scientific facts, and various other space-related data. The means of presenting the data range from cartoons and drawings to lists and narratives, some briefly quoted and some reproduced in full.

Woodfill, Jerry

1992-01-01

305

Bioprocessing in Space  

NASA Technical Reports Server (NTRS)

Proceedings are presented of the 1976 NASA Colloquium on bioprocessing in space. The program included general sessions and formal presentations on the following topics: NASA's Space Shuttle, Spacelab, and space-processing programs; the known unusual behavior of materials in space; space-processing experiment results; cell biology, gravity sensors in cells, space electrophoresis of living cells, new approaches to biosynthesis of biologicals from cell culture in space, and zero-g fermentation concepts; and upcoming flight opportunities and industrial application planning studies already underway.

Morrison, D. R. (compiler)

1977-01-01

306

Space Physiology and Operational Space Medicine  

NASA Technical Reports Server (NTRS)

The objectives of this slide presentation are to teach a level of familiarity with: the effects of short and long duration space flight on the human body, the major medical concerns regarding future long duration missions, the environmental issues that have potential medical impact on the crew, the role and capabilities of the Space Medicine Flight Surgeon and the environmental impacts experienced by the Apollo crews. The main physiological effects of space flight on the human body reviewed in this presentation are: space motion sickness (SMS), neurovestibular, cardiovascular, musculoskeletal, immune/hematopoietic system and behavioral/psycho-social. Some countermeasures are discussed to these effects.

Scheuring, Richard A.

2009-01-01

307

Cosmology from the high redshift intergalactic medium  

NASA Astrophysics Data System (ADS)

Spectroscopic observations of absorption systems towards high redshift quasars provide a powerful tool for constraining the values of a variety of cosmological parameters. The measurement of the primordial D/H ratio, within the framework of standard big bang nucleosynthesis, gives a determination of the baryon density ?bh2. A measurement of the mean flux decrement DA of the Ly? forest, when combined with sophisticated hydrodynamical simulations, provides constraints on the baryon density ?bh 2, the amplitude of mass fluctuations ?8, and the amplitude of H I photoionizing radiation J912. This thesis presents the D/H abundance in absorption systems towards two quasars, HS 0105+1619 and Q1243+4037, which when combined with other measurements of D/H at high redshift gives a value for the baryon density of ? bh2 = 0.0214 ± 0.002. Also presented in the thesis is the measurement of DA at a redshift of z ? 1.9 of DA = 0.118 ± 0.010 along with constraints on ?bh 2, ?8, and J912 from an analysis of DA along with one of the largest cosmological simulations performed to date.

O'Meara, John M.

2004-10-01

308

Extragalactic Radio Jets and Intergalactic Medium 2  

NASA Technical Reports Server (NTRS)

During the mid 1990s, the ROSAT satellite provided the highest resolution X-ray imaging, with useful X-ray spectroscopy, and excellent sensitivity. ROSAT"s PSPC and HRI instruments gave us our first high-quality data on the AGN phenomenon in nearby galaxies - the central theme of this research project. Initially this project concentrated on separating the AGN-related component of the X-ray emission from thermal radiation from the surrounding atmospheres in radio galaxies. There was ample reason to believe that this separation would be possible, although earlier work had taken the view that the X-ray emission from radio galaxies is either wholly AGN-related (and hence of sub-arcsec scale), or wholly from the galaxy and cluster atmospheres (and hence of scales - 10 arcsec or more in the low-redshift radio galaxies that we chose to study). First with the PSPC, and then with the HRI, we proved that a wide range of AGN core X ray emissivities could be found, and that the generic radio galaxy produces both AGN-related and atmosphere-related X-radiation. We demonstrated that there is a close relationship between the core X-ray power and the core radio power, and found instances in which the hot atmospheres of the galaxies must be participating in cooling flows, and other cases where those atmospheres are relatively stable. In some cases, there is a clear active relationship between the extended radio emission and the X-ray atmospheres: thus in NGC 326, we interpret the distorted radio structure as evidence of buoyancy as the radio plasma rises through the cluster atmosphere. In 3C 449, we can see that the radio plasma is displacing the X-ray emitting gas. In a further case (NGC 1265), we hoped that the motion of a radio galaxy through a cluster atmosphere would be apparent though the wake that it might establish - unfortunately, other structure in the atmosphere of the Perseus cluster tends to dominate our X-ray image, and no useful limits could be placed on the strength of the wake. In the light of so-called "unified" models of AGN, it is expected that the low-power radio galaxies studied under these programmes are the unbeamed counterparts of BL Lac objects. Accordingly, we predicted that BL Lac objects, as a class, should show X-ray halos from atmospheres similar to those associated with radio galaxies. The difficulty with studying this is that BL Lac objects tend to be X-ray bright, and the halos then vanish under the wings of the point response function. We found a BL Lac with less of a dynamic range problem, mapped it with the ROSAT HRI, and duly found an atmosphere (Hardcastle et al. 1999). Unfortunately for unification models, this atmosphere is exceptionally dense, so that it must be participating in an intense cooling flow. The implications of this for unification models are far from clear, and further work is under way.

Birkinshaw, Mark

2000-01-01

309

Galactic winds in the intergalactic medium  

E-print Network

We have performed hydrodynamical simulations to investigate the effects of galactic winds on the high-redshift (z=3) universe. Strong winds suppress the formation of low-mass galaxies significantly, and the metals carried by them produce C IV absorption lines with properties in reasonable agreement with observations. The winds have little effect on the statistics of the H I absorption lines, because the hot gas bubbles blown by the winds fill only a small fraction of the volume and because they tend to escape into the voids, thereby leaving the filaments that produce these lines intact.

Tom Theuns; Matteo Viel; Scott Kay; Joop Schaye; Robert F. Carswell; Panayiotis Tzanavaris

2002-08-23

310

The Swedish space program  

NASA Astrophysics Data System (ADS)

The main Swedish space organizations and projects are briefly reviewed. The main responsibilities of the Swedish National Space Board and Swedish Space Corporation are outlined and the government space budget is presented for fiscal years 1987-1990. The main objectives of the Swedish national scientific program are listed in their relationship to space efforts, and the participating institutes are given. The Viking, Freja, and Promics satellites are discussed. Swedish remote sensing efforts and participation in international efforts are addressed.

Helger, Arne

311

Destination Outer Space  

NSDL National Science Digital Library

Students acquire a basic understanding of the science and engineering of space travel as well as a brief history of space exploration. They learn about the scientists and engineers who made space travel possible and briefly examine some famous space missions. Finally, they learn the basics of rocket science (Newton's third law of motion), the main components of rockets and the U.S. space shuttle, and how engineers are involved in creating and launching spacecraft.

Integrated Teaching And Learning Program

312

Space Today Online  

NSDL National Science Digital Library

This online magazine is intended to provide accurate information on past, present, and future human activities in and about space, including space science, history, research, space flight, solar system exploration, deep space astronomy, and cosmology. It features news articles on space vehicles, astronauts, coming launches and landings, satellite missions, telescopes, and many other topics. The site also provides image galleries, videos, and resources for teachers such as lesson plans, book reviews, tutorials, and other items.

Curtis, Anthony R.

2006-03-07

313

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION COMMERCIAL SPACE COMMITTEE  

E-print Network

Committee explore what can be done regarding market issues concerning commercial space companies and what1 NATIONAL AERONAUTICS AND SPACE ADMINISTRATION COMMERCIAL SPACE COMMITTEE OF THE NASA ADVISORY _____________________________________ ________________________________ John Emond, Executive Secretary Commercial Space Committee Bretton Alexander, Chair Commercial Space

Waliser, Duane E.

314

Space Math: Mathematics in Space Science II  

NSDL National Science Digital Library

This booklet contains 36 math problems that cover solar physics, space physics, radiation dosimetry, and the human impacts of space weather. The problems range from pre-algebra to calculus and span the math skills appropriate for Grade 8-12 students. The problems are taken from authentic applications of arithmetic, graph analysis, pre-algebra, and algebra.

Odenwald, Sten

2007-01-01

315

Space Math: Mathematics in Space Science III  

NSDL National Science Digital Library

This booklet contains 36 math problems that cover solar physics, space physics, radiation dosimetry, and the human impacts of space weather. The problems range from pre-algebra to calculus and span the math skills appropriate for Grade 8-12 students. The problems are taken from applications of arithmetic, graph analysis, pre-algebra, and algebra.

Odenwald, Sten

2007-01-01

316

Man in Space, Space in the Seventies.  

ERIC Educational Resources Information Center

Included is a summary of the Apollo lunar program to date. Projected future NASA programs planned for the 1970's are discussed under the headings Skylab, Space Shuttle, and Space Station. Possibilities for the 1980's are outlined in the final section. (Author/AL)

Froehlich, Walter

317

National Aeronautics and Space Administration International Space  

E-print Network

: Enabling Exploration · International Activities ­ Global Exploration Strategy (GES) ­ International Space Exploration Coordination Group (ISECG) · 14 Int'l Space Agencies ­ Developing the Global Exploration Roadmap-traditional ­ Strong NASA interest in enabling commercial opportunities that contribute to exploration program success

Waliser, Duane E.

318

SpaceTech—Postgraduate space education  

NASA Astrophysics Data System (ADS)

SpaceTech is a postgraduate program geared primarily for mid-career space professionals seeking to gain or improve their expertise in space systems engineering and in business engineering. SpaceTech provides a lifelong impact on its participants by broadening their capabilities, encouraging systematic "end-to-end" thinking and preparing them for any technical or business-related engineering challenges they may encounter. This flexible 1-year program offers high competency gain and increased business skills. It is held in attractive locations in a flexible, multi-cultural environment. SpaceTech is a highly effective master's program certified by the esteemed Technical University of Delft (TUD), Netherlands. SpaceTech provides expert instructors who place no barriers between themselves and participants. The program combines innovative and flexible new approaches with time-tested methods to give participants the skills required for future missions and new business, while allowing participants to meet their work commitments at the same time as they study for their master's degree. The SpaceTech program is conducted in separate sessions, generally each of 2-week duration, separated by periods of some 6-8 weeks, during which time participants may return to their normal jobs. It also includes introductory online course material that the participants can study at their leisure. The first session is held at the TUD, with subsequent sessions held at strategic space agency locations. By participating at two or more of these sessions, attendees can earn certificates of satisfactory completion from TU Delft. By participating in all of the sessions, as well as taking part in the companion Central Case Project (CCP), participants earn an accredited and highly respected master's degree in Space Systems Engineering from the TUD. Seven distinct SpaceTech modules are provided during these sessions: Space Mission Analysis and Design, Systems Engineering, Business Engineering, Interpersonal Skills, Telecommunications, Earth Observation and Navigation. A group CCP, a major asset of this unique program, is a focused project, aimed at the formation of a credible virtual commercial space-related business. Participants exercise space systems engineering fundamentals as well as marketing and business engineering tools, with the goal of creating a financially viable business opportunity. They then present the result, in the form of an unsolicited proposal to potential investors, as well as a varied group of engineers, managers and executives from the space community. During the CCP, participants learn the ties between mission and system design and the potential return to investors. They develop an instinct for the technical concepts and which of the parameters to adjust to make their newly conceived business more effective and profitable.

de Bruijn, Ferdi J.; Ashford, Edward W.; Larson, Wiley J.

2008-07-01

319

Section 2: The Space of Media Space  

NASA Astrophysics Data System (ADS)

We began our study of media space with the social aspects of mediated communication because many in the computer-supported cooperative work (CSCW) realm are familiar with models, theories, frameworks, issues, and design approaches related to sociality. But the first media space research came from another set of traditions — the ordering of space and the making of place. Formally, these are the professional and intellectual provinces of architecture, which are probably remote from the disciplinary backgrounds of most readers. However, remoteness in terms of rhetoric and training does not prevent proximity to everyday human experience. The meaning of media space with respect to human experience is the focus of the articles in this section. The spaces are designed to have meaning, and the meaning of the design derives from spatial experience.

Harrison, Steve

320

Deep Space Communication  

NASA Technical Reports Server (NTRS)

ITU defines deep space as the volume of Space at distances from the Earth equal to, or greater than, 2 106 km. Deep Space Spacecraft have to travel tens of millions of km from Earth to reach the nearest object in deep space. Spacecraft mass and power are precious. Large ground-based antennas and very high power transmitters are needed to overcome large space loss and spacecraft's small antennas and low power transmitters. Navigation is complex and highly dependent on measurements from the Earth. Every deep space mission is unique and therefore very costly to develop.

Manshadi, Farzin

2012-01-01

321

[Reflections on physical spaces and mental spaces].  

PubMed

This article analyzes certain reciprocal impacts from physical spaces to mental spaces. If the epistemological construction and the spatial imagination from the subject of cogito or the social collectivities are able to influence the construction and creation of the physical spaces of that subject, then the context of that physical space may also affect the cognitive or social subject's mental cognition. This article applies the methodology of iconology from art history (E. Panofsky) and sociology (P. Bourdieu) to explore correlations between the creation of imaginative and physical spaces from the collective consciousness and mental cognition. The author uses Gilles Deleuses's opinion regarding the 17th-century Baroque style and contemporary social collective symptoms as an explanation. From these theoretical studies, the author analyzes the differences of spatial epistemology generated by Taiwan's special geological text. Finally, the author applies Michel Foucault's studies on spatial context to assess the possible application of this thesis of reciprocal impacts from mental spaces to physical spaces in a nursing context. PMID:23922087

Chen, Hung-Yi

2013-08-01

322

Dosimetry of space radiations  

NASA Technical Reports Server (NTRS)

Harmful effects of space radiation are discussed. Radiation dosimetry methods are given. Dosimetry monitoring is investigated. Methods for measuring space radiation by ionization, thermoluminescence, and nuclear photographic emulsions are described.

Arkhangelskiy, V. V.; Markelov, V. V.; Skvortsov, S. S.; Smirennyy, L. N.; Turkin, V. N.; Chernykh, I. V.

1973-01-01

323

Angry Birds Space Encounter  

NASA Video Gallery

At NASA's Kennedy Space Center Visitor Complex in Florida, a grand opening celebration was held for the new Angry Birds Space Encounter, March 22. Finland-based Rovio Entertainment, the creator of ...

324

Space spider crane  

NASA Technical Reports Server (NTRS)

A space spider crane for the movement, placement, and or assembly of various components on or in the vicinity of a space structure is described. As permanent space structures are utilized by the space program, a means will be required to transport cargo and perform various repair tasks. A space spider crane comprising a small central body with attached manipulators and legs fulfills this requirement. The manipulators may be equipped with constant pressure gripping end effectors or tools to accomplish various repair tasks. The legs are also equipped with constant pressure gripping end effectors to grip the space structure. Control of the space spider crane may be achieved either by computer software or a remotely situated human operator, who maintains visual contact via television cameras mounted on the space spider crane. One possible walking program consists of a parallel motion walking program whereby the small central body alternatively leans forward and backward relative to end effectors.

Macconochie, Ian O. (inventor); Mikulas, Martin M., Jr. (inventor); Pennington, Jack E. (inventor); Kinkead, Rebecca L. (inventor); Bryan, Charles F., Jr. (inventor)

1988-01-01

325

What's Your Favorite Space?  

NASA Video Gallery

The crew of STS-135, NASA's final space shuttle mission, and Sesame Street's Elmo welcomed visitors to "What's Your Favorite Space?" in New York City. The free, public event was presented by NASA a...

326

Causal Learning Space Carving  

E-print Network

Causal Learning Space Carving Deep CRFs Cambridge Interview Technical Talk David Duvenaud February 2, 2010 David Duvenaud Cambridge Interview Technical Talk #12;Causal Learning Space Carving Deep Results 3 Deep CRFs Motivation Recursive Segmentation Learning David Duvenaud Cambridge Interview

Ghahramani, Zoubin

327

Plants in Space  

NASA Video Gallery

This student plant growth investigation on the International Space Station compares plant growth on the ground with plant growth in space. Brassica rapa seeds, commonly known as a turnip mustard, w...

328

Stereotype locally convex spaces  

NASA Astrophysics Data System (ADS)

We give complete proofs of some previously announced results in the theory of stereotype (that is, reflexive in the sense of Pontryagin duality) locally convex spaces. These spaces have important applications in topological algebra and functional analysis.

Akbarov, S. S.

2000-08-01

329

Characterizing Protein Conformation Space  

E-print Network

In this work, we propose a radical approach for exploring the space of all possible protein structures. We present techniques to explore the clash-free conformation space, which comprises all protein structures whose atoms ...

Nigham, Anshul

330

NESTEC - New Space Technology  

Microsoft Academic Search

The EU \\/ NESTEC proposal is a dedicated project to study a new spacecraft concept for space weather purposes. This includes a new satellite bus technology, a new space weather storm particle detection technology and a new EUV solar telescope.

F. Jansen

2009-01-01

331

NESTEC - New Space Technology  

NASA Astrophysics Data System (ADS)

The EU / NESTEC proposal is a dedicated project to study a new spacecraft concept for space weather purposes. This includes a new satellite bus technology, a new space weather storm particle detection technology and a new EUV solar telescope.

Jansen, F.

2009-04-01

332

Traveling Space Museum  

NASA Video Gallery

In an effort to inspire and motivate the next generation of space explorers, NASAâ??s Ames Research Center teamed up with the Traveling Space Museum to teach students the way astronauts are taughtâ...

333

Pathfinder: Humans in space  

NASA Technical Reports Server (NTRS)

Viewgraphs are presented on the Pathfinder program. Information is given on human exploration of the solar system, technical requirements interfaces, program objectives, space suits, human performance, man-machine systems, space habitats, life support systems, and artificial gravity

Anderson, John L.

1988-01-01

334

The Classroom Space Project.  

ERIC Educational Resources Information Center

Introduces the Classroom Space project aimed at revitalizing science education at Key Stages 3 and 4 by using exciting examples from Space Science and Astronomy to illustrate key science concepts. (Author/YDS)

Verbickas, Sarah

2002-01-01

335

Space.com  

NSDL National Science Digital Library

This site is a collection of recent news articles on astronomy topics. Topics include, space flight, technology, SETI, and more. The site includes multimedia resources, image galleries, tech news and a link to Space.com's Twitter feed.

2010-07-02

336

Beyond the Space Cadre.  

National Technical Information Service (NTIS)

The Marine Corps must develop an expeditionary trained and equipped core of space professionals who can provide the commander with integrated space analysis, products, and expertise during the Marine Corps Planning Process (MCPP), as well as synchronize a...

B. W. Phillips

2008-01-01

337

Occupational Space Medicine  

NASA Technical Reports Server (NTRS)

Learning Objectives are: (1) Understand the unique work environment of astronauts. (2) Understand the effect microgravity has on human physiology (3) Understand how NASA Space Medicine Division is mitigating the health risks of space missions.

Tarver, William J.

2012-01-01

338

Welding in Space Workshop  

NASA Technical Reports Server (NTRS)

The potential was discussed for welding in space, its advantages and disadvantages, and what type of programs can benefit from the capability. Review of the various presentations and comments made in the course of the workshop suggests several routes to obtaining a better understanding of how welding processes can be used in NASA's initiatives in space. They are as follows: (1) development of a document identifying well processes and equipment requirements applicable to space and lunar environments; (2) more demonstrations of welding particular hardware which are to be used in the above environments, especially for space repair operations; (3) increased awareness among contractors responsible for building space equipment as to the potential for welding operations in space and on other planetary bodies; and (4) continuation of space welding research projects is important to maintain awareness within NASA that welding in space is viable and beneficial.

Workman, Gary L.

1990-01-01

339

Space Ship Pilot Lesson  

NSDL National Science Digital Library

The Space Ship Pilot lesson is a study of Newton's Laws of motion. Students use a model of a space shuttle and a ferry boat to study differences in an oject's motion with and without resistive forces.

Joiner, David; The Shodor Education Foundation, Inc.

340

The Space Station Chronicles  

NASA Video Gallery

As early as the nineteenth century, writers and artists and scientists around the world began to publish their visions of a crewed outpost in space. Learn about the history of space stations, from ...

341

Architecting space communication networks  

E-print Network

Reliable communication and navigation services are critical to robotic and human space missions. NASA currently provides them through three independent and uncoordinated network that consist of both Earth-based and space-based ...

Sanchez Net, Marc

2014-01-01

342

Space astronomy update  

NASA Astrophysics Data System (ADS)

A discussion of the images obtained by NASA's Hubble Space Telescope (HST) is featured on this video. The discussion panel consists of Dr. Jeff Hester (Arizona State Univ.), Dr. Jon Morse (Space Telescope Science Inst.), Dr. Chris Burrows (European Space Agency), Dr. Bruce Margon (Univ. of Washington), and host Don Savage (Goddard Space Flight Center). A variety of graphics and explanations are provided for the images of star formations and other astronomical features that were viewed by the HST.

1995-06-01

343

Ice in Space  

NSDL National Science Digital Library

This is a detailed lesson about space and how Earth fits in it. Learners will consider the essential question, "What is space?" Activities include small group miming, speaking, drawing, and/or writing about space and the evidence for ice in space. Included are detailed games and dialogue. Native stories are shared. This is lesson 9 of 12 in the unit, Exploring Ice in the Solar System.

344

Arizona Space Grant Consortium  

NSDL National Science Digital Library

The Arizona Space Grant Consortium's mission "is to expand opportunities for Americans to learn about and participate in NASA's aeronautics and space programs by supporting and enhancing science, and engineering education, research, and outreach programs." The website features overviews, explanations of the missions, and the histories of a number of space science projects including Moon Devils and the Students Satellite Program. Students can explore graduate fellowship and undergraduate internship opportunities. Teachers can learn about opportunities to have Space Grant Speakers visit their classrooms.

345

The Tensor Theory Space  

E-print Network

The tensor track is a background-independent discretization of quantum gravity which includes a sum over all topologies. We discuss how to define a functional renormalization group flow and the Wetterich equation in the corresponding theory space. This space is different from the Einsteinian theory space of asymptotic safety. It includes all fixed-rank tensor-invariant interactions, hence generalizes matrix models and the (Moyal) non-commutative field theory space.

Vincent Rivasseau

2014-07-01

346

Space and energy  

Microsoft Academic Search

Potential contributions of space to energy-related activities are discussed. Advanced concepts presented include worldwide energy distribution to substation-sized users using low-altitude space reflectors; powering large numbers of large aircraft worldwide using laser beams reflected from space mirror complexes; providing night illumination via sunlight-reflecting space mirrors; fine-scale power programming and monitoring in transmission networks by monitoring millions of network points from

I. Bekey

1976-01-01

347

Canadian 'Handshake in Space'  

NASA Technical Reports Server (NTRS)

A Canadian 'handshake' in space occurred on April 28, 2001, as the Canadian-built space station robotic arm (Canadarm-2) transferred its launch cradle over to Endeavor's robotic arm. Marning the controls from the shuttle's aft flight deck, Canadian Mission Specialist Chris A. Hadfield of the Canadian Space Agency (CSA) was instrumental in the activity. The Spacelab pallet that carried the Canadarm2 robotic arm to the station was developed at the Marshall Space Flight Center (MSFC) in Huntsville, Alabama.

2001-01-01

348

Space Photography 1977 Index  

NASA Technical Reports Server (NTRS)

An index is provided to representative photographs and transparencies available from NASA. Subjects include spacecraft, astronauts, lunar surface, planets and outer space phenomena, earth observations, and aviation. High altitude aircraft infrared photographs are included along with artists' conceptions of space shuttle and space colonies.

1976-01-01

349

Teacher in Space Project.  

ERIC Educational Resources Information Center

Prepared by NASA, this guide contains lessons dealing with space for use in elementary and secondary social studies classes. Activities are many and varied. For example, students analyze the costs and benefits of space travel, develop their own space station, and explore the decision-making processes involved in the shuttle. (RM)

Social Education, 1986

1986-01-01

350

Space travel and gravity  

Microsoft Academic Search

Space travelling is not possible for human because, by the time, we cross Jupiter, our bones dissolve as there is zero gravity and, by developing a gravity chamber in the space ship itself we will be able to travel in space for generations and explore the universe.

P. Karmakar; Greeninavin

2010-01-01

351

Space nuclear power  

SciTech Connect

This volume considers the major aspects of space nuclear power. It includes treatments of radioactivity, radiation interaction with matter, nuclear reactor principles, thermodynamic power conversion systems, and heat transfer and heat rejection systems. Applications of nuclear energy in space are introduced in the context of man's space exploits.

Angelo, J. Jr.; Buden, D.

1985-01-01

352

Deep Space Telecommunications  

NASA Technical Reports Server (NTRS)

The increasing load on NASA's deep Space Network, the new capabilities for deep space missions inherent in a next-generation radio telescope, and the potential of new telescope technology for reducing construction and operation costs suggest a natural marriage between radio astronomy and deep space telecommunications in developing advanced radio telescope concepts.

Kuiper, T. B. H.; Resch, G. M.

2000-01-01

353

Space methods in oceanology  

NASA Technical Reports Server (NTRS)

The study of Earth from space with specialized satellites, and from manned orbiting stations, has become important in the space programs. The broad complex of methods used for probing Earth from space are different methods of the study of ocean, dynamics. The different methods of ocean observation are described.

Bolshakov, A. A.

1985-01-01

354

European Space Agency (ESA)  

NSDL National Science Digital Library

The European Space Agency's homepage provides information on the ESA's telecommunications, navigations, Earth observations, human spaceflight missions, launches, space science, technology, industry, space operations, technical and quality management and television broadcasting. The site also contains a multimedia gallery, press releases, and an educational page for kids.

2010-04-30

355

Space laser power transmission  

NASA Technical Reports Server (NTRS)

Proposed laser transmission applications are reviewed. Technologies for laser power transmissions are assessed. Feasible laser mission systems are set out. Components by wavelength are summarized. Feasible space to space laser power transmission systems are summarized. Space laser transmitter masses for 1 MW and 100 KW output power are summarized.

1982-01-01

356

Time or Space ' Fluctuating  

E-print Network

' Time or Space =0 2 2 ( ') Variance of ( ) Independent of space and time Concept of Spatial Homogeneity and Temporal Stationarity Correlation Function R 2 1 2 1 Space: R( ) '( ) '( ) R( ),x x x x x x x x 2 1 2 1 2 1 Time: R(t ) '( ) '( ) R(t); tt

Goodman, Louis

357

Space Weather Now  

NSDL National Science Digital Library

The Space Weather Now page is intended to give the non-technical user a "plain language" look at space weather. It includes information about relevant events and announcements, data from and about different instruments and satellites watching various aspects of space weather, alerts and advisories, daily themes of products and services, and links appropriate for the various groups of users.

Center, Space E.; Service, National O.

358

Dependent Probability Spaces  

ERIC Educational Resources Information Center

The mathematical model used to describe independence between two events in probability has a non-intuitive consequence called dependent spaces. The paper begins with a very brief history of the development of probability, then defines dependent spaces, and reviews what is known about finite spaces with uniform probability. The study of finite…

Edwards, William F.; Shiflett, Ray C.; Shultz, Harris

2008-01-01

359

SPACE RESOURCES ROUNDTABLE IX  

E-print Network

SPACE RESOURCES ROUNDTABLE IX Colorado School of Mines October 25-27, 2007 http://www.ISRUinfo.com Sponsored by: Colorado School of Mines Lunar and Planetary Institute Space Resources Roundtable, Inc. First Space Michael B. Duke, Colorado School of Mines Leslie Gertsch, University of Missouri-Rolla Alex

Rathbun, Julie A.

360

My Place, My Space  

ERIC Educational Resources Information Center

Five- and six-year-olds know a lot about their own homes. Besides school, home is probably where they spend most of their time. But have they ever really thought about their space? Using students' knowledge of their current space will help them design new spaces and think about all the areas that surround them. In this project, students design…

Kostal, Heather

2011-01-01

361

Space processing applications bibliography  

NASA Technical Reports Server (NTRS)

This special bibliography lists 724 articles, papers, and reports which discuss various aspects of the use of the space environment for materials science research or for commercial enterprise. The potentialities of space processing and the improved materials processes that are made possible by the unique aspects of the space environment are emphasized. References identified in April, 1978 are cited.

1978-01-01

362

Attachment 2 SPACE SUMMARY  

E-print Network

Attachment 2 SPACE SUMMARY ACADEMIC CENTER 1-Apr-04 Space Number Room Use Code Space Name N Psychology Clinic 930 1,395 MULTI-PURPOSE HALL AREA 22 610 Multi-Purpose Hall 6,000 1.2 7,200 23 615 Stage 1

Sura, Philip

363

The Ninth National Space Symposium  

NASA Astrophysics Data System (ADS)

Proceedings of the Ninth National Space Symposium held 13-16 April 1993 by the United States Space Foundation are presented. Presentations made at the symposium are included. Topics discussed include: Change, Challenge and Opportunity; Washington Insiders: National Space Policy and Budget Issues; Civil Space: a Vision for the Future; Space Power for an Expanded Vision; Unparalled Launch Vehicle Propulsion Capabilities; National Security Space Issues; Perspectives on the Air Force in Space; Future Technology: Space Propulsion, Earth Observation and International Cooperation; Achieving Efficient Space Transportation; the Future in Space Exploration; Kids, Parents and Teachers are into Space; and Public Congressional Forum on Space - International Space Issues.

Lipskin, Beth Ann; Patterson, Sara; Brescia, David A.; Burk, Donna; Flannery, Jack; St. John, Pat; Zimkas, Chuck

364

Space tourism risks: A space insurance perspective  

NASA Astrophysics Data System (ADS)

Space transportation is inherently risky to humans, whether they are trained astronauts or paying tourists, given that spaceflight is still in its relative infancy. However, this is easy to forget when subjected to the hype often associated with space tourism and the ventures seeking to enter that market. The development of commercial spaceflight constitutes a challenge as much as a great opportunity to the insurance industry as new risks emerge and standards, policies and procedures to minimise/mitigate and cover them still to be engineered. Therefore the creation of a viable and affordable insurance regime for future space tourists is a critical step in the development of a real space tourism market to address burning risk management issues that may otherwise ultimately hamper this nascent industry before it has a chance to prove itself.

Bensoussan, Denis

2010-06-01

365

Affordable Space Tourism: SpaceStationSim  

NASA Technical Reports Server (NTRS)

For over 5 years, people have been living and working in space on the International Space Station (ISS), a state-of-the-art laboratory complex orbiting high above the Earth. Offering a large, sustained microgravity environment that cannot be duplicated on Earth, the ISS furthers humankind s knowledge of science and how the body functions for extended periods of time in space all of which will prove vital on long-duration missions to Mars. On-orbit construction of the station began in November 1998, with the launch of the Russian Zarya Control Module, which provided battery power and fuel storage. This module was followed by additional components and supplies over the course of several months. In November 2000, the first ISS Expedition crew moved in. Since then, the ISS has continued to change and evolve. The space station is currently 240 feet wide, measured across the solar arrays, and 171 feet long, from the NASA Destiny Laboratory to the Russian Zvezda Habitation Module. It is 90 feet tall, and it weighs approximately 404,000 pounds. Crews inhabit a living space of about 15,000 cubic feet. To date, 90 scientific investigations have been conducted on the space station. New results from space station research, from basic science to exploration research, are being published each month, and more breakthroughs are likely to come. It is not all work on the space station, though. The orbiting home affords many of the comforts one finds on Earth. There is a weightless "weight room" and even a musical keyboard alongside research facilities. Holidays are observed, and with them, traditional foods such as turkey and cobbler are eaten, with lemonade to wash them down

2006-01-01

366

National Aeronautics and Space Administration Space Launch System (SLS)  

E-print Network

National Aeronautics and Space Administration Space Launch System (SLS) Fun Facts · Designed operational vehicle today (Crew Configuration Shown) #12;National Aeronautics and Space Administration George

Waliser, Duane E.

367

Storms in Space  

NASA Astrophysics Data System (ADS)

Introduction; The cast of characters; Vignettes of the storm; 1. Two kinds of weather; 2. The saga of the storm; 3. Weather stations in space; 4. Lights in the night: the signature of the storm; 5. A walking tour of the magnetosphere; 6. The sun: where it all begins; 7. Nowcasting and forecasting storms in space; 8. Technology and the risks from storms in space; 9. A conversation with Joe Allen; 10. Manned exploration and space weather hazards; 11. The present and future of space weather forecasting; Mathematical appendix. A closer look; Glossary; Figure captions.

Freeman, John W.

2012-11-01

368

{kappa}-Rindler space  

SciTech Connect

In this paper we construct, and investigate some thermal properties of, the noncommutative counterpart of Rindler space, which we call {kappa}-Rindler space. This space is obtained by changing variables in the defining commutators of {kappa}-Minkowski space. We then rederive the commutator structure of {kappa}-Rindler space with the help of an appropriate star product, obtained from the {kappa}-Minkowski one. Using this star product, following the idea of Padmanabhan, we find the leading order, 1/{kappa} correction to the Hawking thermal spectrum.

Kowalski-Glikman, J. [Institute for Theoretical Physics, University of Wroclaw (Poland)

2009-08-15

369

TANK SPACE OPTIONS REPORT  

SciTech Connect

Since this report was originally issued in 2001, several options proposed for increasing double-shell tank (DST) storage space were implemented or are in the process of implementation. Changes to the single-shell tank (SST) waste retrieval schedule, completion of DST space saving options, and the DST space saving options in progress have delayed the projected shortfall of DST storage space from the 2007-2011 to the 2018-2025 timeframe (ORP-11242, River Protection Project System Plan). This report reevaluates options from Rev. 0 and includes evaluations of new options for alleviating projected restrictions on SST waste retrieval beginning in 2018 because of the lack of DST storage space.

WILLIS WL; AHRENDT MR

2009-08-11

370

Developments in space medicine.  

NASA Technical Reports Server (NTRS)

The principal directions and results of space medicine studies are reviewed, starting with the early 1950s. The effects of prolonged inaction, a gravity-free environment, and isolation on the survival and functioning of man in space are examined. Quarantine and other measures developed to guard the health of astronauts during space missions are described. Space radiation hazards and means of overcoming them are discussed. The development of exobiology as a new field of science from our increasing knowledge of the universe is noted, together with some technological and medical advances resulting from space research.

Warren, S.

1973-01-01

371

Madrid space station  

NASA Technical Reports Server (NTRS)

The Madrid space station, operated under bilateral agreements between the governments of the United States and Spain, is described in both Spanish and English. The space station utilizes two tracking and data acquisition networks: the Deep Space Network (DSN) of the National Aeronautics and Space Administration and the Spaceflight Tracking and Data Network (STDN) operated under the direction of the Goddard Space Flight Center. The station, which is staffed by Spanish employees, comprises four facilities: Robledo 1, Cebreros, and Fresnedillas-Navalagamella, all with 26-meter-diameter antennas, and Robledo 2, with a 64-meter antenna.

Fahnestock, R. J.; Renzetti, N. A.

1975-01-01

372

Space Station habitability research  

NASA Technical Reports Server (NTRS)

The purpose and scope of the Habitability Research Group within the Space Human Factors Office at the NASA/Ames Research Cente is described. Both near-term and long-term research objectives in the space human factors program pertaining to the U.S. manned Space Station are introduced. The concept of habitability and its relevancy to the U.S. space program is defined within a historical context. The relationship of habitability research to the optimization of environmental and operational determinants of productivity is discussed. Ongoing habitability research efforts pertaining to living and working on the Space Station are described.

Clearwater, Y. A.

1986-01-01

373

Space Station Habitability Research  

NASA Technical Reports Server (NTRS)

The purpose and scope of the Habitability Research Group within the Space Human Factors Office at the NASA/Ames Research Center is described. Both near-term and long-term research objectives in the space human factors program pertaining to the U.S. manned Space Station are introduced. The concept of habitability and its relevancy to the U.S. space program is defined within a historical context. The relationship of habitability research to the optimization of environmental and operational determinants of productivity is discussed. Ongoing habitability research efforts pertaining to living and working on the Space Station are described.

Clearwater, Yvonne A.

1988-01-01

374

Canadian 'Handshake in Space'  

NASA Technical Reports Server (NTRS)

A Canadian 'handshake' in space occurred on April 28, 2001, as the Canadian-built space station robotic arm (Canadarm2) transferred its launch cradle over to Endeavour's robotic arm. Pictured is astronaut James S. Voss, Expedition Two flight engineer, working the controls of the new robotic arm. Marning the controls from the shuttle's aft flight deck, Canadian Mission Specialist Chris A. Hadfield of the Canadian Space Agency (CSA) was instrumental in the activity. The Space lab pallet that carried the Canadarm2 robotic arm to the station was developed at the Marshall Space Flight Center (MSFC) in Huntsville, Alabama.

2001-01-01

375

The gender of space 1  

Microsoft Academic Search

A systematic review of studies on space and on gender in general anthropology, sociology, architecture and other related social science fields allows us to distinguish four different types of approaches. Studies on gender, space, on gender and space (including gendered space), and the gender of space. Unlike genderized space, where biologically determined gender is a factor, gender of space is

2003-01-01

376

Cellular stratified spaces  

E-print Network

The notion of cellular stratified spaces was introduced in a joint work of the author with Basabe, Gonz{\\'a}lez, and Rudyak [http://arxiv.org/abs/1009.1851">1009.1851] with the aim of constructing a cellular model of the configuration space of a sphere. In particular, it was shown that the classifying space (order complex) of the face poset of a totally normal regular cellular stratified space $X$ can be embedded in $X$ as a strong deformation retract. Here we elaborate on this idea and develop the theory of cellular stratified spaces. We introduce the notion of locally polyhedral cellular stratified spaces and associate a PL topological category $C(X)$ to such a stratified space $X$. We show the classifying space $BC(X)$ of $C(X)$ can be embedded into $X$ as a strong deformation retract. We also introduce a more general structure, called stellar stratified spaces, and extend the results to stellar stratified spaces. The classifying space $BC(X)$ is shown to be equipped with a canonical stellar structure, whi...

Tamaki, Dai

2011-01-01

377

Center for Space Construction  

NASA Technical Reports Server (NTRS)

The Center for Space Construction (CSC) at University of Colorado at Boulder is one of eight University Space Engineering Research Centers established by NASA in 1988. The mission of the Center is to conduct research into space technology and to directly contribute to space engineering education. The Center reports to the Department of Aerospace Engineering Sciences and resides in the College of Engineering and Applied Sciences. The College has a long and successful track record of cultivating multi-disciplinary research and education programs. The Center for Space Construction represents prominent evidence of this record. The basic concept on which the Center was founded is the in-space construction of large space systems, such as space stations, interplanetary space vehicles, and extraterrestrial space structures. Since 1993, the scope of CSC research has evolved to include the design and construction of all spacecraft, large and small. With the broadened scope our research projects seek to impact the technological basis for spacecraft such as remote sensing satellites, communication satellites and other special-purpose spacecraft, as well as large space platforms. A summary of accomplishments, including student participation and degrees awarded, during the contract period is presented.

Su, Renjeng

1998-01-01

378

RBSP Space Weather data  

NASA Astrophysics Data System (ADS)

On August 23, 2012, NASA will launch two identical probes into the radiation belts to provide unprecedented insight into the physical processes and dynamics of near-Earth space. The RBSP mission in addition to the scientific data return, provides a 1Kbps real-time space weather broadcast data in support of real time space weather modeling, forecast and prediction efforts. Networks of ground stations have been identified to downlink the space weather data. The RBSP instrument suites have selected space weather data to be broadcast from their collected space data on board the spacecraft, a subset from measurements based on information normally available to the instrument. The data subset includes particle fluxes at a variety of energies, and magnetic and electric field data. This selected space weather data is broadcast at all times through the primary spacecraft science downlink antennas when an observatory is not in a primary mission-related ground contact. The collected data will resolve important scientific issues and help researchers develop and improve various models for the radiation belts that can be used by forecasters to predict space weather phenomena and alert astronauts and spacecraft operators to potential hazards. The near real-time data from RBSP will be available to monitor and analyze current environmental conditions, forecast natural environmental changes and support anomaly resolution. The space weather data will be available on the RBSP Science Gateway at http://athena.jhuapl.edu/ and will provide access to the space weather data received from the RBSP real-time space weather broadcast. The near real-time data will be calibrated and displayed on the web as soon as possible. The CCMC will ingest the RBSP space weather data into real-time models. The raw space weather data will be permanently archived at APL. This presentation will provide a first look at RBSP space weather data products.

Weiss, M.; Fox, N. J.; Mauk, B. H.; Barnes, R. J.; Potter, M.; Romeo, G.; Smith, D.

2012-12-01

379

Making space law relevant to basic space science in the commercial space age  

Microsoft Academic Search

Space science has been at the heart of humanity's activity in space, a fact reflected in the body of space law set up to regulate such activity. The increase in commercial utilisation of space may threaten the conduct of space science; reform of space law, however, could alleviate this situation. Using the examples of radio and light interference, and space

Sriram Swaminathan

2005-01-01

380

National Aeronautics and Space Administration Space Life and Physical Sciences  

E-print Network

National Aeronautics and Space Administration Space Life and Physical Sciences D National Laboratory management organization (CASIS) #12;National Aeronautics and Space Administration #12;National Aeronautics and Space Administration geneLAB Campaign Progress To move forward

Waliser, Duane E.

381

Space Resources Roundtable 2  

NASA Technical Reports Server (NTRS)

Contents include following: Developing Technologies for Space Resource Utilization - Concept for a Planetary Engineering Research Institute. Results of a Conceptual Systems Analysis of Systems for 200 m Deep Sampling of the Martian Subsurface. The Role of Near-Earth Asteroids in Long-Term Platinum Supply. Core Drilling for Extra-Terrestrial Mining. Recommendations by the "LSP and Manufacturing" Group to the NSF-NASA Workshop on Autonomous Construction and Manufacturing for Space Electrical Power Systems. Plasma Processing of Lunar and Planetary Materials. Percussive Force Magnitude in Permafrost. Summary of the Issues Regarding the Martian Subsurface Explorer. A Costing Strategy for Manufacturing in Orbit Using Extraterrestrial Resources. Mine Planning for Asteroid Orebodies. Organic-based Dissolution of Silicates: A New Approach to Element Extraction from LunarRegohth. Historic Frontier Processes Active in Future Space-based Mineral Extraction. The Near-Earth Space Surveillance (NIESS) Mission: Discovery, Tracking, and Characterization of Asteroids, Comets, and Artificial Satellites with a microsatellite. Privatized Space Resource Property Ownership. The Fabrication of Silicon Solar Cells on the Moon Using In-Situ Resources. A New Strategy for Exploration Technology Development: The Human Exploration and Development of Space (HEDS) Exploratiori/Commercialization Technology Initiative. Space Resources for Space Tourism. Recovery of Volatiles from the Moon and Associated Issues. Preliminary Analysis of a Small Robot for Martian Regolith Excavation. The Registration of Space-based Property. Continuous Processing with Mars Gases. Drilling and Logging in Space; An Oil-Well Perspective. LORPEX for Power Surges: Drilling, Rock Crushing. An End-To-End Near-Earth Asteroid Resource Exploitation Plan. An Engineering and Cost Model for Human Space Settlement Architectures: Focus on Space Hotels and Moon/Mars Exploration. The Development and Realization of a Silicon-60-based Economy in CisLunar Space. Our Lunar Destiny: Creating a Lunar Economy. Cost-Effective Approaches to Lunar Passenger Transportation. Lunar Mineral Resources: Extraction and Application. Space Resources Development - The Link Between Human Exploration and the Long-term Commercialization of Space. Toward a More Comprehensive Evaluation of Space Information. Development of Metal Casting Molds by Sol-Gel Technology Using Planetary Resources. A New Concept in Planetary Exploration: ISRU with Power Bursts. Bold Space Ventures Require Fervent Public Support. Hot-pressed Iron from Lunar Soil. The Lunar Dust Problem: A Possible Remedy. Considerations on Use of Lunar Regolith in Lunar Constructions. Experimental Study on Water Production by Hydrogen Reduction of Lunar Soil Simulant in a Fixed Bed Reactor.

Ignatiev, A.

2000-01-01

382

Public choice economics and space policy: realising space tourism  

Microsoft Academic Search

Government space agencies have the statutory responsibility to suport the commercialisation of space activities. NASA's 1998 report “General Public Space Travel and Tourism” concluded that passenger space travel can start using already existing technology, and is likely to grow into the largest commercial activity in space: it is therefore greatly in taxpayers' economic interest that passenger space travel and accommodation

Patrick Collins

2001-01-01

383

UCL DEPARTMENT OF SPACE & CLIMATE PHYSICS SPACE PLASMA PHYSICS GROUP  

E-print Network

UCL DEPARTMENT OF SPACE & CLIMATE PHYSICS SPACE PLASMA PHYSICS GROUP 18th September 2012 STFC 2012 #12;UCL DEPARTMENT OF SPACE & CLIMATE PHYSICS SPACE PLASMA PHYSICS GROUP 18th September 2012 STFC · Conclusion #12;UCL DEPARTMENT OF SPACE & CLIMATE PHYSICS SPACE PLASMA PHYSICS GROUP 18th September 2012 STFC

384

Compact spaces and their applications in Banach space theory  

E-print Network

topological properties of the unit ball of the dual space X ensure a given property of a Banach space X problems and deep theorems. Banach spaces are closely related to compact spaces. Firstly, the space C, the unit ball of its dual space X is compact when equipped with the topology of pointwise convergence on X

Tebbens, Jurjen Duintjer

385

Space Systems Finland 1 Deployment in the Space Sector  

E-print Network

© Space Systems Finland 1 Deployment in the Space Sector #12;© Space Systems Finland 2 SW Constraints Design Requirements User Requirements SW Requirements #12;© Space Systems Finland 3 The space, but there is no viable alternative · Many requirements are not testable #12;© Space Systems Finland 4 SSF OBJECTIVES

Southampton, University of

386

space for science, enterprise and environment Bringing Space Into School  

E-print Network

space for science, enterprise and environment Bringing Space Into School Science The National Space Education Initiative #12;space for science, enterprise and environment National Space Education Initiative the consultations · Recommendations of the report #12;space for science, enterprise and environment Background

387

Gymnastics in Phase Space  

SciTech Connect

As accelerator technology advances, the requirements on accelerator beam quality become increasingly demanding. Facing these new demands, the topic of phase space gymnastics is becoming a new focus of accelerator physics R&D. In a phase space gymnastics, the beam's phase space distribution is manipulated and precision tailored to meet the required beam qualities. On the other hand, all realization of such gymnastics will have to obey accelerator physics principles as well as technological limitations. Recent examples of phase space gymnastics include Emittance exchanges, Phase space exchanges, Emittance partitioning, Seeded FELs and Microbunched beams. The emittance related topics of this list are reviewed in this report. The accelerator physics basis, the optics design principles that provide these phase space manipulations, and the possible applications of these gymnastics, are discussed. This fascinating new field promises to be a powerful tool of the future.

Chao, Alexander Wu; /SLAC

2012-03-01

388

Space resources. Overview  

NASA Technical Reports Server (NTRS)

Space resources must be used to support life on the Moon and in the exploration of Mars. Just as the pioneers applied the tools they brought with them to resources they found along the way rather than trying to haul all their needs over a long supply line, so too must space travelers apply their high technology tools to local resources. This overview describes the findings of a study on the use of space resources in the development of future space activities and defines the necessary research and development that must precede the practical utilization of these resources. Space resources considered included lunar soil, oxygen derived from lunar soil, material retrieved from near-Earth asteroids, abundant sunlight, low gravity, and high vacuum. The study participants analyzed the direct use of these resources, the potential demand for products from them, the techniques for retrieving and processing space resources, the necessary infrastructure, and the economic tradeoffs.

Mckay, Mary Fae (editor); Mckay, David S. (editor); Duke, Michael B. (editor)

1992-01-01

389

Space biology research development  

NASA Technical Reports Server (NTRS)

The purpose of the Search for Extraterrestrial Intelligence (SETI) Institute is to conduct and promote research related activities regarding the search for extraterrestrial life, particularly intelligent life. Such research encompasses the broad discipline of 'Life in the Universe', including all scientific and technological aspects of astronomy and the planetary sciences, chemical evolution, the origin of life, biological evolution, and cultural evolution. The primary purpose was to provide funding for the Principal Investigator to collaborate with the personnel of the SETI Institute and the NASA-Ames Research center in order to plan and develop space biology research on and in connection with Space Station Freedom; to promote cooperation with the international partners in the space station; to conduct a study on the use of biosensors in space biology research and life support system operation; and to promote space biology research through the initiation of an annual publication 'Advances in Space Biology and Medicine'.

Bonting, Sjoerd L.

1993-01-01

390

Quantum-Space Attacks  

E-print Network

Theoretical quantum key distribution (QKD) protocols commonly rely on the use of qubits (quantum bits). In reality, however, due to practical limitations, the legitimate users are forced to employ a larger quantum (Hilbert) space, say a quhexit (quantum six-dimensional) space, or even a much larger quantum Hilbert space. Various specific attacks exploit of these limitations. Although security can still be proved in some very special cases, a general framework that considers such realistic QKD protocols, as well as} attacks on such protocols, is still missing. We describe a general method of attacking realistic QKD protocols, which we call the `quantum-space attack'. The description is based on assessing the enlarged quantum space actually used by a protocol, the `quantum space of the protocol'. We demonstrate these new methods by classifying various (known) recent attacks against several QKD schemes, and by analyzing a novel attack on interferometry-based QKD.

Ran Gelles; Tal Mor

2007-11-19

391

THz Sources for Space  

NASA Technical Reports Server (NTRS)

Terahertz is the primary frequency for line and continuum radiation from cool (5-100K) gas (atoms and molecules) and dust. This viewgraph presentation reviews the reasons for the interest in Terahertz Space Applications; the Terahertz Space Missions: in the past, present and planned for the future, Terahertz source requirements and examples of some JPL instruments; and a case study for a flight deliverable: THz Local Oscillators for ESA s Herschel Space Telescope

Siegel, Peter H.; Ward, John; Maiwald, Frank; Mehdi, Imran

2007-01-01

392

Commutators on Banach Spaces  

E-print Network

Page 1. Commutators on Lp, 1 ?pDistance between finite dimensional Banach spaces . . 60 3. Best constant in Grotendieck?s inequality . . . . . . . 60 REFERENCES... with respect to a basis in the space and it is not hard to see (the proof of which we will present in Chapter II) that the operators on a finite dimensional Banach space which are commutators are the ones which have trace equal to zero. Commutators also appear...

Dosev, Detelin

2010-10-12

393

Aging and space travel  

NASA Technical Reports Server (NTRS)

The matter of aging and its relation to space vehicle crewmembers undertaking prolonged space missions is addressed. The capabilities of the older space traveler to recover from bone demineralization and muscle atrophy are discussed. Certain advantages of the older person are noted, for example, a greater tolerance of monotony and repetitious activities. Additional parameters are delineated including the cardiovascular system, the reproductive system, ionizing radiation, performance, and group dynamics.

Mohler, S. R.

1982-01-01

394

Rocket and Space Technology  

NSDL National Science Digital Library

This site, created by author Robert Braeuning, features material on orbital mechanics, propulsion, rocket hardware, space centers and missions. It includes definitions of important terms and black-and-white diagrams. The page also features information on rocket propellants, rocket propulsion, orbital mechanics, spacecraft systems, vehicle specifications, launch vehicles, manned space flights, planetary spacecraft, and lunar spacecraft. A glossary and discussion forum are also provided. This is a nice resource for a overview of all things involving rockets or other space technologies.

Braeuning, Robert

2009-05-04

395

Space solar cell research  

SciTech Connect

New solar cell technologies are emerging that could replace silicon cells in power-conversion applications. Gallium arsenide, indium phosphide, and other semiconducting compounds are the focal point of an expanding research effort. The primary subject matter of the article is divided into the following areas: Space vs. terrestrial cell efficiency; Space solar cells; Silicon Cells; Gallium arsenide cells; Other space solar cells; Indium phosphide cells; Superlattice solar cells.

Flood, D.J.

1989-04-01

396

Space Weather Media Viewer  

NSDL National Science Digital Library

This is version 3 of the space Weather Media Viewer, created to work with the space Weather Action Center to see near-real time data and to provide additional images and resources available for educational use. It features easy downloads that can also be added to news reports and space weather reports. It was designed for ease in adding any media (videos, images) data.

2011-01-01

397

Space Mechanisms Technology Workshop  

NASA Technical Reports Server (NTRS)

The Mechanical Components Branch at NASA Glenn Research Center hosted a workshop to discuss the state of drive systems technology needed for space exploration. The Workshop was held Thursday, November 2, 2000. About 70 space mechanisms experts shared their experiences from working in this field and considered technology development that will be needed to support future space exploration in the next 10 to 30 years.

Oswald, Fred B. (Editor)

2001-01-01

398

Space Bounds for Resolution  

Microsoft Academic Search

We introduce a new way to measure the space needed in a resolution refutation of a CNF formula in propositional logic. With\\u000a the former definition [6] the space required for the resolution of any unsatisfiable formula in CNF is linear in the number of clauses. The new definition\\u000a allows a much finer analysis of the space in the refutation, ranging

Juan Luis Esteban; Jacobo Torán

1999-01-01

399

Space Odyssey Gift Shop  

NASA Technical Reports Server (NTRS)

The Space Odyssey Gift Shop located in StenniSphere at the John C. Stennis Space Center in Hancock County, Miss., offers every visitor the opportunity to go home with 'the right stuff' from his or her StenniSphere visit. The gift shop is located just inside the front doors to StenniSphere and offers a wide range of space-related apparel, memorabilia, toys, books, mission patches and more.

2000-01-01

400

Space as a Resource  

Microsoft Academic Search

\\u000a In this assay, we aim at defending the hypothesis that physically spoken sheer “empty” space in itself without any other commodities\\u000a has the function of resource for plant life. Definitions of space, niche, and resource are examined. We consider competition\\u000a for resources and space occupation and exploitation above ground, where light is often a decisive limiting factor. Steady-state\\u000a and dynamic

Thorsten E. E. Grams; Ulrich Lüttge

401

Space Systems Laboratory (SSL)  

NSDL National Science Digital Library

The Space Systems Laboratory (SSL) at the University of Maryland is investigating human and robotic performance in space. Among the many projects being conducted at the SSL are a telerobotic spacecraft servicer called Ranger--to be launched into Earth orbit via an expendable rocket in 1997, and a Space Shuttle flight experiment which will investigate human fatigue during extravehicular activities (spacewalks). The SSL Home Page presents the projects, personnel, and facilities of the lab.

402

Basics of Space Flight  

NSDL National Science Digital Library

This training module was designed to help the user identify and grasp basic concepts associated with space travel and deep space missions. Separate sections deal with topics such as the physical environment of space (solar system, gravity, orbital mechanics), flight projects (mission concepts, system requirements, design, onboard systems and instruments), and flight operations (launch, cruise, encounter). Links to related topics are embedded in the text.

403

Space Station galley design  

NASA Technical Reports Server (NTRS)

An Advanced Food Hardware System galley for the initial operating capability (IOC) Space Station is discussed. Space Station will employ food hardware items that have never been flown in space, such as a dishwasher, microwave oven, blender/mixer, bulk food and beverage dispensers, automated food inventory management, a trash compactor, and an advanced technology refrigerator/freezer. These new technologies and designs are described and the trades, design, development, and testing associated with each are summarized.

Trabanino, Rudy; Murphy, George L.; Yakut, M. M.

1986-01-01

404

Distances between Banach spaces  

Microsoft Academic Search

The main object of the paper is to study the distance between Banach spaces\\u000aintroduced by Kadets. For Banach spaces $X$ and $Y$, the Kadets distance is\\u000adefined to be the infimum of the Hausdorff distance $d(B_X,B_Y)$ between the\\u000arespective closed unit balls over all isometric linear embeddings of $X$ and\\u000a$Y$ into a common Banach space $Z.$ This is

Nigel J. Kalton; Mikhail I. Ostrovskii

1999-01-01

405

Matter: Space without Time  

E-print Network

While Quantum Gravity remains elusive and Quantum Field Theory retains the interpretational difficulties of Quantum Mechanics, we have introduced an alternate approach to the unification of particles, fields, space and time, suggesting that the concept of matter as space without time provides a framework which unifies matter with spacetime and in which we anticipate the development of complete theories (ideally a single unified theory) describing observed 'particles, charges, fields and forces' solely with the geometry of our matter-space-time universe.

Yousef Ghazi-Tabatabai

2012-09-14

406

International Space Station exhibit  

NASA Technical Reports Server (NTRS)

The International Space Station (ISS) exhibit in StenniSphere at John C. Stennis Space Center in Hancock County, Miss., gives visitors an up-close look at the largest international peacetime project in history. Step inside a module of the ISS and glimpse how astronauts will live and work in space. Currently, 16 countries contribute resources and hardware to the ISS. When complete, the orbiting research facility will be larger than a football field.

2000-01-01

407

AB Space Engine  

E-print Network

On 4 January 2007 the author published the article Wireless Transfer of Electricity in Outer Space in http://arxiv.org wherein he offered and researched a new revolutionary method of transferring electric energy in space. In that same article, he offered a new engine which produces a large thrust without throwing away large amounts of reaction mass (unlike the conventional rocket engine). In the current article, the author develops the theory of this kind of impulse engine and computes a sample project which shows the big possibilities opened by this new AB-Space Engine. The AB-Space Engine gets the energy from ground-mounted power; a planet electric station can transfer electricity up to 1000 millions (and more) of kilometers by plasma wires. Author shows that AB-Space Engine can produce thrust of 10 tons (and more). That can accelerate a space ship to some thousands of kilometers/second. AB-Space Engine has a staggering specific impulse owing to the very small mass expended. The AB-Space Engine reacts not by expulsion of its own mass (unlike rocket engine) but against the mass of its planet of origin (located perhaps a thousand of millions of kilometers away) through the magnetic field of its plasma cable. For creating this plasma cable the AB-Space Engine spends only some kg of hydrogen.

Alexander Bolonkin

2008-03-02

408

Space support forum  

NASA Technical Reports Server (NTRS)

This is a report of the discussions held by the Space Support Forum on the subject of education as an investment in the future. The Space Support Forum is a gathering of representatives of various space-related organizations that interact or overlap with the mission of the Space Foundation. They reported that an international science assessment in 17 countries ranked the United States either near or at the bottom in biology, chemistry, and physics. The U.S. Department of Education has laid out 6 National Education Goals to turn this status around and is helping hundreds of communities to work towards these goals, referred to as America 2000.

Posvar, Wesley W.; Laidlaw, Donald A.; Brown, Robert; King, Douglas; Graham, Daniel O.; Strine, Linda; Hopkins, Mark; Mcnair, Carl

1992-01-01

409

Space Shuttle Cockpit  

NASA Technical Reports Server (NTRS)

Want to sit in the cockpit of the Space Shuttle and watch astronauts work in outer space? At StenniSphere, you can do that and much more. StenniSphere, the visitor center at John C. Stennis space Center in Hancock County, Miss., presents 14,000-square-feet of interactive exhibits that depict America's race for space as well as a glimpse of the future. Stennisphere is open free of charge from 9 a.m. to 5 p.m. daily.

2000-01-01

410

Space Shuttle Cockpit exhibit  

NASA Technical Reports Server (NTRS)

Want to sit in the cockpit of the Space Shuttle and watch astronauts work in outer space? At StenniSphere, you can do that and much more. StenniSphere, the visitor center at John C. Stennis Space Center in Hancock County, Miss., presents 14,000-square-feet of interactive exhibits that depict America's race for space as well as a glimpse of the future. StenniSphere is open free of charge from 9 a.m. to 5 p.m. daily.

2000-01-01

411

Space station structures development  

NASA Technical Reports Server (NTRS)

A study of three interrelated tasks focusing on deployable Space Station truss structures is discussed. Task 1, the development of an alternate deployment system for linear truss, resulted in the preliminary design of an in-space reloadable linear motor deployer. Task 2, advanced composites deployable truss development, resulted in the testing and evaluation of composite materials for struts used in a deployable linear truss. Task 3, assembly of structures in space/erectable structures, resulted in the preliminary design of Space Station pressurized module support structures. An independent, redundant support system was developed for the common United States modules.

Teller, V. B.

1986-01-01

412

Man in space.  

PubMed

Today, more than 20 years after the first in the world man's space walk, soviet cosmonautics gained large experience of extravehicular activity (EVA). Space suits of high reliability, onboard facilities for passing through the airlock, sets of special tools and technological rigging, as well as procedures for carrying out various EVA's were developed. In the course of the Salyut-7 space station orbital operation the EVA's have become regular. The author of the report as the participant of the EVA's considers the main steps of man activities in space and analyzes specific problems arised in performing such activities. PMID:11542958

Solovjev, V A

1987-09-01

413

The space station  

NASA Technical Reports Server (NTRS)

Conceived since the beginning of time, living in space is no longer a dream but rather a very near reality. The concept of a Space Station is not a new one, but a redefined one. Many investigations on the kinds of experiments and work assignments the Space Station will need to accommodate have been completed, but NASA specialists are constantly talking with potential users of the Station to learn more about the work they, the users, want to do in space. Present configurations are examined along with possible new ones.

Munoz, Abraham

1988-01-01

414

Space construction activities  

NASA Technical Reports Server (NTRS)

The Center for Space Construction at the University of Colorado at Boulder was established in 1988 as a University Space Engineering Research Center. The mission of the Center is to conduct interdisciplinary engineering research which is critical to the construction of future space structures and systems and to educate students who will have the vision and technical skills to successfully lead future space construction activities. The research activities are currently organized around two central projects: Orbital Construction and Lunar Construction. Summaries of the research projects are included.

1991-01-01

415

Space vacuum processing  

NASA Technical Reports Server (NTRS)

The unique ultra-vacuum environment of low-earth orbit space is to be utilized for vacuum processing of advanced semiconductor and superconductor materials through epitaxial thin-film growth. The quality of semiconductor single crystal (epitaxial) thin-films can be significantly enhanced in the space ultra-vacuum through the reduction of impurities. This will be accomplished by the development of the free-flying Wake Shield Facility presently being built by the Space Vacuum Epitaxy Center in conjunction with industry and NASA under a low-cost, short time commercial approach to space hardware development.

Ignatiev, A.; Shih, H. D.; Daniels, M.; Sega, R.; Bonner, T.

1991-01-01

416

Growing plant in space  

NASA Technical Reports Server (NTRS)

Space agencies in several countries are planning for the culture of plants in long duration space bases. The challenge of developing crop production procedures suitable for space projects will result in a new approach of problems we may meet today or in the near future in our common production systems. You may keep in mind subjects as: minimizing wastes or pollution problems, saving materials, introductions robotic helps. Discussion between scientists involved with food production for space programmes and protected horticultural cultivation may open new perspectives.

Tibbitts, T. W.; Bula, R. J.; Tibbits, T. W.

1989-01-01

417

Kennedy Space Center  

NASA Technical Reports Server (NTRS)

Among 2011's many accomplishments, we safely retired the Space Shuttle Program after 30 incredible years; completed the International Space Station and are taking steps to enable it to reach its full potential as a multi-purpose laboratory; and helped to expand scientific knowledge with missions like Aquarius, GRAIL, and the Mars Science Laboratory. Responding to national budget challenges, we are prioritizing critical capabilities and divesting ourselves of assets no longer needed for NASA's future exploration programs. Since these facilities do not have to be maintained or demolished, the government saves money. At the same time, our commercial partners save money because they do not have to build new facilities. It is a win-win for everyone. Moving forward, 2012 will be even more historically significant as we celebrate the 50th Anniversary of Kennedy Space Center. In the coming year, KSC will facilitate commercial transportation to low-Earth orbit and support the evolution of the Space Launch System and Orion crew vehicle as they ready for exploration missions, which will shape how human beings view the universe. While NASA's Vision is to lead scientific and technological advances in aeronautics and space for a Nation on the frontier of discovery KSC's vision is to be the world's preeminent launch complex for government and commercial space access, enabling the world to explore and work in space. KSC's Mission is to safely manage, develop, integrate, and sustain space systems through partnerships that enable innovative, diverse access to space and inspires the Nation's future explorers.

Griffin, Amanda

2012-01-01

418

The deep space network  

NASA Technical Reports Server (NTRS)

Presented is Deep Space Network (DSN) progress in flight project support, tracking and data acquisition (TDA) research and technology, network engineering, hardware and software implementation, and operations.

1977-01-01

419

The deep space network  

NASA Technical Reports Server (NTRS)

Summaries are given of Deep Space Network progress in flight project support, tracking and data acquisition research and technology, network engineering, hardware and software implementation, and operations.

1975-01-01

420

Management of outer space  

NASA Astrophysics Data System (ADS)

Various aspects of space-environment management are discussed. Attention is called to the fact that, while space radio communications are already under an adequate management by the International Communications Union, the use of nuclear power sources is regulated by the recently adopted set of principles, and space debris will be discussed in the near future at the UN COPUOS, other aspects of management of outer space received little or no attention of the international community. These include the competency of crews and technical equipment of spacecraft launched by newcomers to space exploration; monitoring of locations and motions of space objects (now in national hands), with relevant data made accessible through a computer network; and the requirement to use space only for beneficial purposes and not for promoting narrow and debatable interests damaging the outer space environment and impeding on astronomical observations. It is suggested that some of these tasks would be best performed by an international space agency within the UN system of organizations.

Perek, Lubos

1993-10-01

421

Concept Learning Hypotheses Space  

E-print Network

in high-dimensional space Maximization of margins Minimizing the VC-dimension Optimal Generalization-S Candidate Elimination Bias Restriction Bias Preference Bias Generalization Decision Trees Entropy

Kjellström, Hedvig

422

Space Flight Now  

NSDL National Science Digital Library

Space Flight Now offers the latest space news from around the world. Visitors can discover information on current missions, launch schedules, and mission reports. Along with providing the space news headlines, the web site supplies news archives so people can catch up on the activities of the space science world. Visitors can enjoy video footage from cameras onboard recent rocket launches. While users do have to subscribe to obtain many of the videos and audio recordings, individuals can benefit from the free up-to-date astronomy news stories and a few videos.

423

Multimegawatt space power reactors  

SciTech Connect

In response to the need of the Strategic Defense Initiative (SDI) and long range space exploration and extra-terrestrial basing by the National Air and Space Administration (NASA), concepts for nuclear power systems in the multi-megawatt levels are being designed and evaluated. The requirements for these power systems are being driven primarily by the need to minimize weight and maximize safety and reliability. This paper will discuss the present requirements for space based advanced power systems, technological issues associated with the development of these advanced nuclear power systems, and some of the concepts proposed for generating large amounts of power in space. 31 figs.

Dearien, J.A.; Whitbeck, J.F.

1989-01-01

424

Android in Space  

NASA Video Gallery

Can smartphones control robots in space? The Nexus-S upgrade of Synchronized Position Hold, Engage, Reorient, Experimental Satellites -- SPHERES -- makes this a reality. By connecting a smartphone ...

425

Space Jell-O  

NSDL National Science Digital Library

This hands-on OLogy experiment uses Jell-O, fruit, nuts, and candy to demonstrate how space bends around anything that has mass. The activity begins with kid-friendly introductions to the concept of mass and Einstein's theory of bending space. The illustrated, step-by-step directions include notes about how the fruit, nuts, and candy represent stars, planets, and other objects in space. At the end, kids are encouraged to celebrate their new-found knowledge by digging into their edible space.

426

Beyond Space-Time  

E-print Network

These notes, based on the remarks made at the 23 Solvay Conference, collect several speculative ideas concerning gauge/ strings duality, de Sitter spaces, dimensionality and the cosmological constant.

A. M. Polyakov

2006-02-01

427

Space Weather: Welcome, SEC  

NSDL National Science Digital Library

This video presentation welcomes the Space Weather Prediction Center, formerly known as the Space Environment Center or SEC to the National Weather Service (NWS) as an operational entity of the National Centers for Environmental Prediction (NCEP) family. Describing the ways in which space weather affects global communications and power resources, it demonstrates the importance of space weather forecasting as a part of the NWS family of services. With the inclusion of SWPC, the NWS now provides environmental understanding from the sun to the sea.

Comet

2005-01-11

428

Commercialization of the Space Frontier  

NASA Technical Reports Server (NTRS)

This paper discusses the current outlook for space business, how growing space business will improve the quality of life for all, and identified strategies for better relating international space research, technology, and space system operations to commercial interests in space. By drawing on recent assessments of the future potential for business in space, opportunities will be defined for encouraging the growth of business uses of space and regaining the public's awareness and support for expanding the space frontier.

Piland, William M.

1997-01-01

429

On Multi-Metric Spaces  

E-print Network

A Smarandache multi-space is a union of $n$ spaces $A_1,A_2,..., A_n$ with some additional conditions holding. Combining Smarandache multi-spaces with classical metric spaces, the conception of multi-metric space is introduced. Some characteristics of a multi-metric space are obtained and Banach's fixed-point theorem is generalized in this paper.

Linfan Mao

2005-10-22

430

Physiologic adaptation to space - Space adaptation syndrome  

NASA Technical Reports Server (NTRS)

The adaptive changes of the neurovestibular system to microgravity, which result in space motion sickness (SMS), are studied. A list of symptoms, which range from vomiting to drowsiness, is provided. The two patterns of symptom development, rapid and gradual, and the duration of the symptoms are described. The concept of sensory conflict and rearrangements to explain SMS is being investigated.

Vanderploeg, J. M.

1985-01-01

431

Cognitive neuroscience in space.  

PubMed

Humans are the most adaptable species on this planet, able to live in vastly different environments on Earth. Space represents the ultimate frontier and a true challenge to human adaptive capabilities. As a group, astronauts and cosmonauts are selected for their ability to work in the highly perilous environment of space, giving their best. Terrestrial research has shown that human cognitive and perceptual motor performances deteriorate under stress. We would expect to observe these effects in space, which currently represents an exceptionally stressful environment for humans. Understanding the neurocognitive and neuropsychological parameters influencing space flight is of high relevance to neuroscientists, as well as psychologists. Many of the environmental characteristics specific to space missions, some of which are also present in space flight simulations, may affect neurocognitive performance. Previous work in space has shown that various psychomotor functions degrade during space flight, including central postural functions, the speed and accuracy of aimed movements, internal timekeeping, attentional processes, sensing of limb position and the central management of concurrent tasks. Other factors that might affect neurocognitive performance in space are illness, injury, toxic exposure, decompression accidents, medication side effects and excessive exposure to radiation. Different tools have been developed to assess and counteract these deficits and problems, including computerized tests and physical exercise devices. It is yet unknown how the brain will adapt to long-term space travel to the asteroids, Mars and beyond. This work represents a comprehensive review of the current knowledge and future challenges of cognitive neuroscience in space from simulations and analog missions to low Earth orbit and beyond. PMID:25370373

De la Torre, Gabriel G

2014-01-01

432

Cognitive Neuroscience in Space  

PubMed Central

Humans are the most adaptable species on this planet, able to live in vastly different environments on Earth. Space represents the ultimate frontier and a true challenge to human adaptive capabilities. As a group, astronauts and cosmonauts are selected for their ability to work in the highly perilous environment of space, giving their best. Terrestrial research has shown that human cognitive and perceptual motor performances deteriorate under stress. We would expect to observe these effects in space, which currently represents an exceptionally stressful environment for humans. Understanding the neurocognitive and neuropsychological parameters influencing space flight is of high relevance to neuroscientists, as well as psychologists. Many of the environmental characteristics specific to space missions, some of which are also present in space flight simulations, may affect neurocognitive performance. Previous work in space has shown that various psychomotor functions degrade during space flight, including central postural functions, the speed and accuracy of aimed movements, internal timekeeping, attentional processes, sensing of limb position and the central management of concurrent tasks. Other factors that might affect neurocognitive performance in space are illness, injury, toxic exposure, decompression accidents, medication side effects and excessive exposure to radiation. Different tools have been developed to assess and counteract these deficits and problems, including computerized tests and physical exercise devices. It is yet unknown how the brain will adapt to long-term space travel to the asteroids, Mars and beyond. This work represents a comprehensive review of the current knowledge and future challenges of cognitive neuroscience in space from simulations and analog missions to low Earth orbit and beyond.

De la Torre, Gabriel G.

2014-01-01

433

Chinese Space Program  

NSDL National Science Digital Library

China will soon make history by sending the first Chinese man to space. Scheduled for sometime in 2003, it will be the first step toward China's highly ambitious plans for space exploration.The China National Space Administration Web site (1) has a detailed description of the country's space policy. Aerospace China, a journal published online by the administration, has information on space development plans and other issues. The history of China's space program is recounted by the online Encyclopedia Astronautica (2). Several influential scientists and their contributions to Chinese rocketry and satellite technology are highlighted. The China Academy of Launch Vehicle Technology (3) sent the first Chinese satellite into space. Its home page showcases eight launch vehicles and offers an extensive technical description of the LM-3C model. The work of various research groups at the Shanghai Astronomical Observatory (4) deals with topics ranging from satellite dynamics to stellar astronomy. Some of the groups have details of their projects and facilities online. Another observatory studies molecular clouds and star formation (5). A large collection of its research papers are provided on its Web site. A news article from Space.com (6) discusses the forthcoming launch of the Shenzhou IV spacecraft, scheduled for later this year. It is generating considerable interest, since it is said to be identical to China's first manned spacecraft, expected to launch in 2003. Another article (7) considers China's rapidly developing space program. With the tremendous effort and lofty goals for moon bases and Mars missions, the author argues that China could eventually rival the US. Many more news stories about the Chinese space program can be found on the Dragon Space Web site (8).

Leske, Cavin.

2002-01-01

434

Space and Atmospheric Environments  

NASA Technical Reports Server (NTRS)

This viewgraph presentation provides information on space environments and the protection of materials and structures from their harsh conditions. Space environments are complex, and the complexity of spacecraft systems is increasing. Design accommodation must be realistic. Environmental problems can be limited at low cost relative to spacecraft cost.

Barth, Janet L.; Day, John H. (Technical Monitor)

2002-01-01

435

Space Mathematics Website  

NSDL National Science Digital Library

This Website contains over 200 authentic math problems that cover solar physics, space physics, radiation dosimetry, and the human impacts of space weather. The problems range from pre-algebra to calculus and span the math skills appropriate for grade 8-12 students. The problems are taken from authentic applications of arithmetic, graph analysis, pre-algebra, and algebra.

2010-09-27

436

Space Station fluid resupply  

Microsoft Academic Search

Viewgraphs on space station fluid resupply are presented. Space Station Freedom is resupplied with supercritical O2 and N2 for the ECLSS and USL on a 180 day resupply cycle. Resupply fluids are stored in the subcarriers on station between resupply cycles and transferred to the users as required. ECLSS contingency fluids (O2 and N2) are supplied and stored on station

Al Winters

1990-01-01

437

Law in Outer Space.  

ERIC Educational Resources Information Center

Provides an overview of the current practice and fascinating future of legal issues involved in outer space exploration and colonization. Current space law, by necessity, addresses broad principles rather than specific incidents. Nonetheless, it covers a variety of issues including commercial development, rescue agreements, object registration,…

Schmidt, William G.

1997-01-01

438

Dr. Massimo Space Telescope  

E-print Network

Dr. Massimo Robberto Space Telescope Science Institute Massimo Robberto received in 1989 his Ph/VLT telescopes. In 1995 he joined the Max Planck Institutein Heidelberg to lead the construction of a new IR camera for the UKIRT telescope in Mauna Kea, Hawaii. In 1999 he moved to the European Space Agency

Zanibbi, Richard

439

Space Ship Pilot Model  

NSDL National Science Digital Library

The Space Ship Pilot model is a model of motion under Newton's laws with and without resistive forces. The first environment puts the user in control of docking a space shuttle, and the second puts the user in control of docking a boat.

Joiner, David; The Shodor Education Foundation, Inc.

440

Space station dynamics  

NASA Technical Reports Server (NTRS)

Structural dynamic characteristics and responses of the Space Station due to the natural and induced environment are discussed. Problems that are peculiar to the Space Station are also discussed. These factors lead to an overall acceleration environment that users may expect. This acceleration environment can be considered as a loading, as well as a disturbance environment.

Berka, Reg

1990-01-01