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It is shown how data on the cluster correlation function can be used in order to reconstruct the density of the pregalactic density field on the cluster mass scale. The method is applied to the data on the cluster correlation amplitude -- richness dependence. The spectrum of the recovered density field has the same shape as the density field derived from data on the galaxy correlation function which is measured as function of linear scales. Matching the two amplitudes relates the mass to the comoving scale it contains and thereby leads to a direct determination of $\Omega$. The resultant density parameter turns out to be $\Omega$=0.25.

We present new methodology to use cosmic infrared background (CIB) fluctuations to probe sources at 1030., Comment: ApJ, in press. Minor revisions/additions to match the version in proofs

We have performed a specific observational test to measure the effect that the zodiacal light can have on measurements of the spatial fluctuations of the near-IR background. Previous estimates of possible fluctuations caused by zodiacal light have often been extrapolated from observations of the thermal emission at longer wavelengths and low angular resolution, or from IRAC observations of high latitude fields where zodiacal light is faint and not strongly varying with time. The new observations analyzed here target the COSMOS field, at low ecliptic latitude where the zodiacal light intensity varies by factors of $\sim2$ over the range of solar elongations at which the field can be observed. We find that the white noise component of the spatial power spectrum of the background is correlated with the modeled zodiacal light intensity. Roughly half of the measured white noise is correlated with the zodiacal light, but a more detailed interpretation of the white noise is hampered by systematic uncertainties that are evident in the zodiacal light model. At large angular scales ($\gtrsim100"$) where excess power above the white noise is observed, we find no correlation of the power with the modeled intensity of the zodiacal light. This test clearly indicates that the large scale power in the infrared background is not being caused by the zodiacal light., Comment: 17 pp. Accepted for publication in the ApJ

We reconstruct \gamma-ray opacity of the Universe out to z, Comment: 5 pages, 5 figures. Published in ApJ Letters

We reconstruct ��-ray opacity of the Universe out to z, 5 pages, 5 figures. Published in ApJ Letters

Peculiar velocities important provide information about the matter distribution on large scales and the origin of density perturbations. We will review the recent determinations of large scale flows obtained from the kinematic Sunyaev-Zel'dovich effect of clusters of galaxies that generate temperature anisotropies on the Cosmic Microwave Background, as measured by the WMAP satellite. We will describe our latest findings on large scale velocity flows, in particular the so-called Dark Flow, a large scale motion that could encompass the observable Universe. We then discuss its implications for inflationary models.

Spatial Fluctuations in the Cosmic Infrared Background have now been measured out to sub-degree scales showing a strong clustering signal from unresolved sources. We attempt to explain these measurement by considering faint galaxy populations at z, 3 pages, 2 figures. To appear in proceedings of First Stars IV meeting (Kyoto, Japan; 2012)

We study the microwave background anisotropy due to superhorizon-size perturbations (the Grischuk-Zel'dovich effect) in open universes with negative spatial curvature. Using COBE results on the low-order temperature multipole moments, we find that if the homogeneity of the observable Universe arises from an early epoch of inflation, the present density parameter cannot differ from unity by more than the observed quadrupole anisotropy, |1-\Omega_0| \alt Q \simeq 5\times 10^{-6}. Thus, inflation models with low \Omega_0 either do not fit the microwave background observations or they do not solve the horizon problem.

We present new results on the "dark flow" from a measurement of the dipole in the distribution of peculiar velocities of galaxy clusters, applying the methodology proposed and developed by us earlier. Our latest measurement is conducted using new, low-noise 7-yr WMAP data as well as an all-sky sample of X-ray selected galaxy clusters compiled exclusively from published catalogs. Our analysis of the CMB signature of the kinematic Sunyaev-Zeldovich (SZ) effect finds a statistically significant dipole at the location of galaxy clusters. The residual dipole outside the cluster regions is small, rendering our overall measurement 3-4 sigma significant. The amplitude of the dipole correlates with cluster properties, being larger for the most X-ray luminous clusters, as required if the signal is produced by the SZ effect. Since it is measured at zero monopole, the dipole can not be due to the thermal SZ effect. Our results are consistent with those obtained earlier by us from 5-yr WMAP data and using a proprietary cluster catalog. In addition, they are robust to quadrupole removal, demonstrating that quadrupole leakage contributes negligibly to the signal. The lower noise of the 7-yr WMAP also allows us, for the first time, to obtain tentative empirical confirmation of our earlier conjecture that the adopted filtering flips the sign of the KSZ effect for realistic clusters and thus of the deduced direction of the flow. The latter is consistent with our earlier measurement in both the amplitude and direction. Assuming the filtering indeed flips the sign of the KSZ effect from the clusters, the direction agrees well also with the results of independent work using galaxies as tracers at lower distances. We make all maps and cluster templates derived by us from public data available to the scientific community to allow independent tests of our method and findings., Comment: ApJ, in press. Replaced with accepted version. The data needed for these results are at http://www.kashlinsky.info/bulkflows/data_public

We review the recent measurements on the cosmic infrared background (CIB) and their implications for the physics of the first stars era, including Population III. The recently obtained CIB results range from the direct measurements of CIB fluctuations from distant sources using deep Spitzer data to strong upper limits on the near-IR CIB from blazar spectra. This allows to compare the Population III models with the CIB data to gain direct insight into the era of the first stars and the formation and evolution of Population III and the microphysics of the feedback processes in the first halos of collapsing material. We also discuss the cosmological confusion resulting from these CIB sources and the prospects for resolving them individually with NASA's upcoming space instruments such as the JWST.

We present new measurements of the large-scale bulk flows of galaxy clusters based on 5-year WMAP data and a significantly expanded X-ray cluster catalogue. Our method probes the flow via measurements of the kinematic Sunyaev-Zeldovich (SZ) effect produced by the hot gas in moving clusters. It computes the dipole in the cosmic microwave background (CMB) data at cluster pixels, which preserves the SZ component while integrating down other contributions. Our improved catalog of over 1,000 clusters enables us to further investigate possible systematic effects and, thanks to a higher median cluster redshift, allows us to measure the bulk flow to larger scales. We present a corrected error treatment and demonstrate that the more X-ray luminous clusters, while fewer in number, have much larger optical depth, resulting in a higher dipole and thus a more accurate flow measurement. This results in the observed correlation of the dipole derived at the aperture of zero monopole with the monopole measured over the cluster central regions. This correlation is expected if the dipole is produced by the SZ effect and cannot be caused by unidentified systematics (or primary cosmic microwave background anisotropies). We measure that the flow is consistent with approximately constant velocity out to at least 800 Mpc. The significance of the measured signal peaks around 500 Mpc, most likely because the contribution from more distant clusters becomes progressively more diluted by the WMAP beam. We can, however, at present not rule out that these more distant clusters simply contribute less to the overall motion., Comment: Ap.J. (Letters), Mar 20/2010. Replaced with published version

A variety of observations constrain models of the origin of large-scale cosmic structures. Enough observational data have accumulated to constrain (and perhaps determine) the power spectrum of primordial density fluctuations over a very large range of scales, independently of the particular cosmogonical theory assumed. Observations in the near future should be able to weed out many such theories.

This paper presents detailed analysis of large-scale peculiar motions derived from a sample of ~ 700 X-ray clusters and cosmic microwave background (CMB) data obtained with WMAP. We use the kinematic Sunyaev-Zeldovich (KSZ) effect combining it into a cumulative statistic which preserves the bulk motion component with the noise integrated down. Such statistic is the dipole of CMB temperature fluctuations evaluated over the pixels of the cluster catalog (Kashlinsky & Atrio-Barandela 2000). To remove the cosmological CMB fluctuations the maps are Wiener-filtered in each of the eight WMAP channels (Q, V, W) which have negligible foreground component. Our findings are as follows: The thermal SZ (TSZ) component of the clusters is described well by the Navarro-Frenk-White profile expected if the hot gas traces the dark matter in the cluster potential wells. Such gas has X-ray temperature decreasing rapidly towards the cluster outskirts, which we demonstrate results in the decrease of the TSZ component as the aperture is increased to encompass the cluster outskirts. We then detect a statistically significant dipole in the CMB pixels at cluster positions. Arising exclusively at the cluster pixels this dipole cannot originate from the foreground or instrument noise emissions and must be produced by the CMB photons which interacted with the hot intracluster gas via the SZ effect. The dipole remains as the monopole component, due to the TSZ effect, vanishes within the small statistical noise out to the maximal aperture where we still detect the TSZ component. We demonstrate with simulations that the mask and cross-talk effects are small for our catalog and contribute negligibly to the measurements. The measured dipole thus arises from the KSZ effect produced by the coherent large scale bulk flow motion., Minor changes to match the published version - Ap.J., 1 Feb 2009 issue

We present the latest results on CIB fluctuations from early epochs from deep Spitzer data. The results show the existence of significant CIB fluctuations at the IRAC wavelengths (3.6 to 8 mic) which remain after removing galaxies down to very faint levels. These fluctuations must arise from populations with a significant clustering component, but only low levels of the shot noise. There are no correlations between the source-subtracted IRAC maps and the corresponding fields observed with the HST ACS at optical wavelengths. Taken together, these data imply that 1) the sources producing the CIB fluctuations are individually faint with S_��< a few nJy at 3.6 and 4.5 mic; 2) have different clustering pattern than the more recent galaxy populations; 3) are located within the first 0.7 Gyr (unless these fluctuations can somehow be produced by - so far unobserved - local galaxies of extremely low luminosity and with the unusual for local populations clustering pattern), 4) produce contribution to the net CIB flux of at least 1-2 nW/m^2/sr at 3.6 and 4.5 mic and must have mass-to-light ratio significantly below the present-day populations, and 5) they have angular density of ~ a few per arcsec^2 and are in the confusion of the present day instruments, but can be individually observable with JWST., Talk at IAU 250 "Massive stars as cosmic engines", Hawaii, Dec 2007

Peculiar velocities of clusters of galaxies can be measured by studying the fluctuations in the cosmic microwave background (CMB) generated by the scattering of the microwave photons by the hot X-ray emitting gas inside clusters. While for individual clusters such measurements result in large errors, a large statistical sample of clusters allows one to study cumulative quantities dominated by the overall bulk flow of the sample with the statistical errors integrating down. We present results from such a measurement using the largest all-sky X-ray cluster catalog combined to date and the 3-year WMAP CMB data. We find a strong and coherent bulk flow on scales out to at least > 300 h^{-1} Mpc, the limit of our catalog. This flow is difficult to explain by gravitational evolution within the framework of the concordance LCDM model and may be indicative of the tilt exerted across the entire current horizon by far-away pre-inflationary inhomogeneities., Ap.J. (Letters), in press. 20 Oct issue (Vol. 686)

Cosmic infrared background (CIB) contains emission from epochs inaccessible to current telescopic studies, such as the era of the first stars. We discuss theoretical expectations for the CIB contributions from the early population of massive stars. We then present the latest results from the ongoing project by our team (Kashlinsky, Arendt, Mather & Moseley 2005,2007a,b,c,) to measure CIB fluctuations from early epochs using deep Spitzer data. The results show the existence of significant CIB fluctuations at the IRAC wavelengths (3.6 to 8 mic) which remain after removing galaxies down to very faint levels. These fluctuations must arise from populations that have a significant clustering component, but only low levels of the shot noise. Furthermore, there are no correlations between the source-subtracted IRAC maps and the corresponding fields observed with the HST ACS at optical wavelengths. Taken together, these data imply that 1) the sources producing the CIB fluctuations are individually faint with flux < a few nJy at 3.6 and 4.5 mic; 2) are located within the first 0.7 Gyr (unless these fluctuations can somehow be produced by - so far unobserved - local galaxies of extremely low luminosity and with the unusual for local populations clustering pattern), 3) they produce contribution to the net CIB flux of at least 1-2 nW/m^2/sr at 3.6 and 4.5 mic and must have mass-to-light ratio significantly below the present-day populations, and 4) they have angular density of ~ a few per arcsec^2 and are in the confusion of the present day instruments, but can be individually observable with JWST., To appear in "First Stars III", eds. B. O'Shea, A. Heger & T. Abel

We constrain the deviation of adiabatic evolution of the Universe using the data on the Cosmic Microwave Background (CMB) temperature anisotropies measured by the {\it Planck} satellite and a sample of 481 X-ray selected clusters with spectroscopically measured redshifts. To avoid antenna beam effects, we bring all the maps to the same resolution. We use a CMB template to subtract the cosmological signal while preserving the Thermal Sunyaev-Zeldovich (TSZ) anisotropies; next, we remove galactic foreground emissions around each cluster and we mask out all known point sources. If the CMB black-body temperature scales with redshift as $T(z)=T_0(1+z)^{1-\alpha}$, we constrain deviations of adiabatic evolution to be $\alpha=-0.007\pm 0.013$, consistent with the temperature-redshift relation of the standard cosmological model. This result could suffer from a potential bias $\delta\alpha$ associated with the CMB template, that we quantify it to be $|\delta\alpha|\le 0.02$ and with the same sign than the measured value of $\alpha$, but is free from those biases associated with using TSZ selected clusters; it represents the best constraint to date of the temperature-redshift relation of the Big-Bang model using only CMB data, confirming previous results., Comment: ApJ, in press. Manuscript matches the accepted version: 10 pages, 7 figures, 3 tables

Cosmic infrared background fluctuations may contain measurable contribution from objects inaccessible to current telescopic studies, such as the first stars and other luminous objects in the first Gyr of the Universe's evolution. In an attempt to uncover this contribution we have analyzed the GOODS data obtained with the Spitzer IRAC instrument, which are deeper and cover larger scales than the Spitzer data we have previously analyzed. Here we report these new measurements of the cosmic infrared background (CIB) fluctuations remaining after removing cosmic sources to fainter levels than before. The remaining anisotropies on scales > 0.5 arcmin have a significant clustering component with a low shot-noise contribution. We show that these fluctuations cannot be accounted for by instrumental effects, nor by the Solar system and Galactic foreground emissions and must arise from extragalactic sources., Ap.J.Letters, in press

We discuss interpretation of the cosmic infrared background (CIB) anisotropies detected by us recently in the Spitzer IRAC based measurements. The fluctuations are approximately isotropic on the sky consistent with their cosmological origin. They remain after removal of fairly faint intervening sources and must arise from a population which has a strong CIB clustering component with only a small shot-noise level. We discuss the constraints the data place on the luminosities, epochs and mass-to-light ratios of the indvidual sources producing them. Assuming the concordance LambdaCDM cosmology the measurements imply that the luminous sources producing them lie at cosmic times < 1 Gyr and were individually much brighter per unit mass than the present stellar populations., Ap.J.Letters, in press

We review the recent measurements on the cosmic infrared background (CIB) and their implications for the physics of the first stars era, including Population III. The recently obtained CIB results range from the direct measurements of CIB fluctuations from distant sources using deep Spitzer data to strong upper limits on the near-IR CIB from blazar spectra. This allows to compare the Population III models with the CIB data to gain direct insight into the era of the first stars and the formation and evolution of Population III and the microphysics of the feedback processes in the first halos of collapsing material. We also discuss the cosmological confusion resulting from these CIB sources and the prospects for resolving them individually with NASA's upcoming space instruments such as the JWST., Comment: Invited talk at "Massive Stars: From Pop III and GRBs to the Milky Way", STScI (Baltimore), May 2006

Cosmic infrared background (CIB) contains information about galaxy luminosities over the entire history of the Universe and can be a powerful diagnostic of the early populations otherwise inaccessible to telescopic studies. Its measurements are very difficult because of the strong IR foregrounds from the Solar system and the Galaxy. Nevertheless, substantial recent progress in measuring the CIB and its structure has been made. The measurements now allow to set significant constraints on early galaxy evolution and, perhaps, even detect the elusive Population III era. We discuss briefly the theory behind the CIB, review the latest measurements of the CIB and its structure, and discuss their implications for detecting and/or constraining the first stars and their epochs., Invited review to appear in proceedings of Irvine workshop "First light and reionization", eds. E. Barton & A. Cooray. New Astronomy Reviews, in press

The deepest space and ground-based observations find metal-enriched galaxies at cosmic times when the Universe was, appears as Article in Nature, 3 Nov 2005. Maps and paper with high-resolution figures can be oibtained from http://haiti.gsfc.nasa.gov/kashlinsky/LIBRA/NATURE

The deepest space- and ground-based observations find metal-enriched galaxies at cosmic times when the Universe was less than 1 Gyr old. These stellar populations had to be preceded by the metal-free first stars, known as 'population III'. Recent cosmic microwave background polarization measurements indicate that stars started forming early--when the Universe wasor =200 Myr old. It is now thought that population III stars were significantly more massive than the present metal-rich stellar populations. Although such sources will not be individually detectable by existing or planned telescopes, they would have produced significant cosmic infrared background radiation in the near-infrared, whose fluctuations reflect the conditions in the primordial density field. Here we report a measurement of diffuse flux fluctuations after removing foreground stars and galaxies. The anisotropies exceed the instrument noise and the more local foregrounds; they can be attributed to emission from population III stars, at an era dominated by these objects.

We discuss the contribution of Population III stars to the near-IR (NIR) cosmic infrared background (CIB) and its effect on spectra of high-$z$ high-energy gamma-ray bursts (GRBs). It is shown that if Population III were massive stars, the claimed NIR CIB excess will be reproduced if only ~ 4+/-2% of all baryons went through these stars. Regardless of the precise value of the NIR CIB produced by them, they would leave enough photons to provide a large optical depth for high-energy photons from high-z GRBs. Observations of such GRBs are expected following the planned launch of NASA's GLAST mission. The presence or absence of such damping in the spectra of high-$z$ GRBs will then provide important information on the emissions from the Population III. The location of this cutoff may also serve as an indicator of the GRB's redshift., Comment: Ap.J.Letters, in press. Revision includes discussion of CIB and low-z blazars. Some typos corrected and minor error in Fig.2 corrected

The cross-correlating cosmic microwave background (CMB) fluctuations caused by the Sunyaev-Zel'dovich effect from observed clusters of galaxies with their redshifts can be used to measure the mean squared cluster peculiar velocity with an error $\sigma_{C_S^2}\simeq (300{\rm km/s})^2$ . This can be done around $z\gt0.3$ with clusters of flux above 200 mJy which will be detected by PLANCK, coupled with high resolution microwave images to eliminate the cosmological part of the CMB fluctuations. The latter can be achieved with observations by the planned ALMA array or the NSF South Pole telescope and other surveys. By measuring the rms peculiar velocity of clusters and their bulk flow in, e.g., 4 spheres of $\sim 100h^{-1}$ Mpc at $z=0.3$ , we could have a direct measurement of the matter density $0.21\lt\Omega_m\lt0.47$ at 95% confidence level. To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Following the successful mapping of the last scattering surface by WMAP and balloon experiments, the epoch of the first stars, when Population III stars formed, is emerging as the next cosmological frontier. It is not clear what these stars' properties were, when they formed or how long their era lasted before leading to the stars and galaxies we see today. We show that these questions can be answered with the current and future measurements of the near-IR cosmic infrared background (CIB). Theoretical arguments suggest that Population III stars were very massive and short-lived stars that formed at $z\sim 10-20$ at rare peaks of the density field in the cold-dark-matter Universe. Because Population III stars probably formed individually in small mini-halos, they are not directly accessible to current telescopic studies. We show that these stars left a strong and measurable signature via their contribution to the CIB anisotropies for a wide range of their formation scenarios. The excess in the recently measured near-IR CIB anisotropies over that from normal galaxies can be explained by contribution from early Population III stars. These results imply that Population III were indeed very massive stars and their epoch started at $z\sim 20$ and lasted past $z\lsim 13$. We show the importance of accurately measuring the CIB anisotropies produced by Population III with future space-based missions., Ap.J., in press. (Replaced with accepted version)

The Cosmic Infrared Background (CIB) reflects the sum total of galactic luminosities integrated over the entire age of the universe. From its measurements one can deduce information about objects at epochs currently inaccessible to telescopic studies. This review discusses the state of the current CIB measurements and the (mostly space-based) instruments with which these measurements have been made, the obstacles (the various foreground emissions)and the physics behind the CIB and its structure. Theoretical discussion of the CIB levels can now be normalized to the standard cosmological model narrowing down theoretical uncertainties. We review the information behind and theoretical modeling of both the mean (isotropic) levels of the CIB and their fluctuations. The CIB is divided into three broad bands: near-IR, mid-IR and far-IR. For each of the bands we review the main contributors to the CIB flux and the epochs at which the bulk of the flux originates. We also discuss the data on the various quantities relevant for correct interpretation of the CIB levels: the star-formation history, the present-day luminosity function measurements, resolving the various galaxy contributors to the CIB, etc. The integrated light of all galaxies in the deepest near-IR galaxy counts to date fails to match the observed mean level of the CIB, probably indicating a significant high-redshift contribution to the CIB. Additionally, Population III stars should have left a strong and measurable signature via their contribution to the cosmic infrared background (CIB) anisotropies for a wide range of their formation scenarios, and measuring the excess CIB anisotropies coming from high z would provide direct information on that epoch., Comment: Invited review, Physics Reports, in press. 97 pages, 24 figures

To understand the cosmic history of element synthesis it will be important to obtain extinction-free measures of the heavy element contents of high-redshift objects and to chart two monumental events: the collapse of the first metal-free clouds to form stars, and the initial seeding of the universe with dust. The information needed to achieve these objectives is uniquely available in the far-infrared/submillimeter (FIR/SMM) spectral region. Following the Decadal Report and anticipating the development of the Single Aperture Far-IR (SAFIR) telescope and FIR/SMM interferometry, we estimate the measurement capabilities of a large-aperture, background-limited FIR/SMM observatory and an interferometer on a boom, and discuss how such instruments could be used to measure the element synthesis history of the universe., 9 pages, 2 figures To be published in Proc. Origins 2002 Conf. "The Heavy Element Trail From Galaxies to Habitable Worlds," ed. C. Woodward

We implement and further refine the recently proposed method (Kashlinsky, Hern\'andez-Monteagudo & Atrio-Barandela, 2001 - KHA) for a time efficient extraction of the power spectrum from future cosmic microwave background (CMB) maps. The method is based on the clustering properties of peaks and troughs of the Gaussian CMB sky. The procedure takes only ${1/2}[f(\nu)]^2N^2$ steps where $f(\nu)$ is the fraction of pixels with $|\delta T|\geq\nu$ standard deviations in the map of $N$ pixels. We use the new statistic introduced in KHA, $\xi_\nu$, which characterizes spatial clustering of the CMB sky peaks of progressively increasing thresholds. The tiny fraction of the remaining pixels (peaks and troughs) contains the required information on the CMB power spectrum of the entire map. The threshold $\nu$ is the only parameter that determines the accuracy of the final spectrum. We performed detailed numerical simulations for parameters of the two-year WMAP and Planck CMB sky data including cosmological signal, inhomogeneous noise and foreground residuals. In all cases we find that the method can recover the power spectrum out to the Nyquist scale of the experiment channel. We discuss how the error bars scale with $\nu$ allowing to decide between accuracy and speed. The method can determine with significant accuracy the CMB power spectrum from the upcoming CMB maps in only $\sim(10^{-5}-10^{-3})\times N^2$ operations., Comment: 11 pages, 14 figures. Minor changes, updated references, matches accepted version in A&A

This is one of two papers in which we report the detection of structure in the cosmic infrared background (CIB) between 1.25 - 2.2 micron through the use of data from the Two Micron Sky Survey (2MASS). This paper concentrates on data assembly, analysis and the estimate of the various foreground contributions; the companion paper (Kashlinsky, Odenwald, Mather, Skrutskie, Cutri 2002, hereafter KOMSC) presents the cosmological results for the CIB fluctuations and their implications. By using repeated observations of a specific calibration star field, we were able to achieve integration times in excess of 3900 seconds compared to the 7.8 seconds in the standard 2MASS data product. This yielded a point source detection limit (3 \sigma) of +18.5^m in K_s band. The resulting co-added images were processed to remove point sources to a limiting surface brightness of +20^m/arcsec$^2 or 40 nW/m^2/sr. The remaining maps contained over 90% of the pixels and were Fourier transformed to study the spatial structure of the diffuse background light. After removing resolved sources and other artifacts, we find that the power spectrum of the final images has a power-law distribution consistent with clustering by distant galaxies. We estimate here the contributions to this signal from Galactic foregrounds, atmospheric OH-glow, zodiacal light and instrument noise, all of which are small and of different slopes. Hence, this supports the KOMSC identification of the signal as coming from the CIB fluctuations produced by distant clustered galaxies., Comment: Ap. J., in press

The question "How did we get here and what will the future bring?" captures the human imagination and the attention of the National Academy of Science's Astronomy and Astrophysics Survey Commitee (AASC). Fulfillment of this "fundamental goal" requires astronomers to have sensitive, high angular and spectral resolution observations in the far-infrared/submillimeter (far-IR/sub-mm) spectral region. With half the luminosity of the universe and vital information about galaxy, star and planet formation, observations in this spectral region require capabilities similar to those currently available or planned at shorter wavelengths. In this paper we summarize the scientific motivation, some mission concepts and technology requirements for far-IR/sub-mm space interferometers that can be developed in the 2010-2020 timeframe., Comment: 11 pages, 6 figures, submitted as a "mission white paper" to NASA's SEU Roadmap Committee