The stochastic background of gravitational waves due to the f-mode instability in neutron stars

This paper presents an estimate for the spectral properties of the stochastic background of gravitational waves emitted by a population of hot, young, rapidly rotating neutron stars throughout the Universe undergoing $f$-mode instabilities, formed through either core-collapse supernova explosions or the merger of binary neutron star systems. Their formation rate, from which the gravitational wave event rate is obtained, is deduced from observation-based determinations of the cosmic star formation rate. The gravitational wave emission occurs during the spin-down phase of the $f$-mode instability. For low magnetized neutron stars and assuming 10\% of supernova events lead to $f$-mode unstable neutron stars, the background from supernova-derived neutron stars peaks at $\Omega_{\text{gw}} \sim 10^{-9}$ for the $l=m=2$ $f$-mode, which should be detectable by cross-correlating a pair of second generation interferometers (e.g. Advanced LIGO/Virgo) with an upper estimate for the signal-to-noise ratio of $\approx$ 9.8. The background from supramassive neutron stars formed from binary mergers peaks at $\Omega_{\text{gw}} \sim 10^{-10}$ and should not be detectable, even with third generation interferometers (e.g. Einstein Telescope)

An IRAS High Resolution Image Restoration (HIRES) Atlas of All Interacting Galaxies in the IRAS Revised Bright Galaxy Sample

We present high-resolution (30"-1') 12, 25, 60, and 100 micron images of 106 interacting galaxy systems contained in the IRAS Revised Bright Galaxy Sample (RBGS, Sanders et al. 2003), a complete sample of all galaxies having a 60 micron flux density greater than 5.24 Jy. These systems were selected to have at least two distinguishable galaxies separated by less than three average galactic diameters, and thus we have excluded very widely separated systems and very advanced mergers. The new complete survey has the same properties as the prototype survey of Surace et al. 1993. We find no increased tendency for infrared-bright galaxies to be associated with other infrared bright galaxies among the widely separated pairs studied here. We find small enhancements in far-infrared activity in multiple galaxy systems relative to RBGS non-interacting galaxies with the same blue luminosity distribution. We also find no differences in infrared activity (as measured by infrared color and luminosity) between late and early-type spiral galaxies.Comment: 49 pages, 13 figures. To appear in the Astronomical Journal. Figures have been degraded due to space considerations. A PDF version with higher quality figures is available at http://humu.ipac.caltech.edu/~jason/pubs/surace_hires.pd

The European Large Area ISO Survey - ISOPHOT results using the MPIA-pipeline

The European Large Area ISO Survey (ELAIS) will provide Infrared observations of 4 regions in the sky with ISO. Around 2000 Infrared sources have been detected at 7 and 15 microns (with ISOCAM), 90 and 175 microns (with ISOPHOT)) over 13 square degrees of the sky. We present the source extraction pipeline of the 90 microns ISOPHOT observations, describe and discuss the results obtained and derive the limits of the ELAIS observational strategy.Comment: 4 pages, 5 figures, to appear in the ISO conference "The Universe as seen by ISO", 1998, UNESCO, Pari

High Spatial Resolution Near-Ir Tip/Tilt Imaging Of "Warm" Ultraluminous Infrared Galaxies

We present results from high spatial resolution (FWHM ≈ 0.3–0.5 ″) near-IR (1.6 and 2.1μm) imaging of a complete sample of ultraluminous infrared galaxies (ULIGs) chosen to have “warm” mid-IR colors (f_(25)/f_(60) > 0.2) characteristic of AGN. In conjunction with our WFPC2 imaging program (Surace et al. 1998), we have found that nearly all of these systems are advanced mergers with complex nuclear morphologies. The extended underlying galaxies are detected in each system at H and K′, and are found to have luminosities of a few L*, similar to quasars (McLeod & Rieke 1994). Many of the circumnuclear star-forming knots seen at optical wavelengths have been detected. Based on model SEDs, their bolometric luminosities appear similar to those of the extended nuclear starbursts seen in other, less-luminous interacting systems (i.e. NGC 4038/9). Each ULIG is increasingly dominated at long wavelengths by a compact source which we identify as a putative active nucleus. The optical/near-IR colors of these putative nuclei are more extreme than the most infrared-active starburst galaxies, yet are identical to “far-IR loud” quasars which are in turn similar to optical quasars with significant hot (800 K) dust emission. Half of the ULIGs have dereddened nuclear near-IR luminosities comparable to those of QSOs, while the others resemble Seyferts; this may be an effect of patchy extinction and scattering. Similarities between the putative ULIG nuclei and QSO nuclei, the underlying host galaxies, and the apparent young age of the ULIGs (as evidenced by their compact star-forming knots) support the evolution of “warm” ULIGs into optical QSOs

The extreme function theory for damage detection: An application to civil and aerospace structures

Any damaged condition is a rare occurrence for mechanical systems, as it is very unlikely to be observed. Thus, it represents an extreme deviation from the median of its probability distribu-tion. It is, therefore, necessary to apply proper statistical solutions, i.e., Rare Event Modelling (REM). The classic tool for this aim is the Extreme Value Theory (EVT), which deals with uni-or multivariate scalar values. The Extreme Function Theory (EFT), on the other hand, is defined by enlarging the fundamental EVT concepts to whole functions. When combined with Gaussian Process Regres-sion (GPR), the EFT is perfectly suited for mode shape-based outlier detection. In fact, it is possible to investigate the structure’s normal modes as a whole rather than focusing on their constituent data points, with quantifiable advantages. This provides a useful tool for Structural Health Monitoring, especially to reduce false alarms. This recently proposed methodology is here tested and validated both numerically and experimentally for different examples coming from Civil and Aerospace Engineering applications. One-dimensional beamlike elements with several boundary conditions are considered, as well as a two-dimensional plate-like spar and a frame structure

Resolved CO(1-0) Nuclei in IRAS 14348-1447: Evidence for Massive Bulge Progenitors to Ultraluminous Infrared Galaxies

High-resolution, CO(1-0) interferometry of the ultraluminous infrared galaxy IRAS 14348-1447 is presented. The merger system has a molecular gas mass of \~3x10^10 solar masses and a projected nuclear separation of 4.8 kpc (3.5"), making it one of the most molecular gas-rich galaxies known and an ideal candidate for studying the intermediate stages of an ultraluminous merger event. The CO morphology shows two molecular gas components associated with the stellar nuclei of the progenitors, consistent with the idea that the molecular disks are gravitationally bound by the dense bulges of the progenitor galaxies as the interaction proceeds. In contrast, less luminous infrared galaxies observed to date with projected nuclear separations of ~<5 kpc show a dominant CO component between the stellar nuclei. This discrepancy may be an indication that the progenitors of mergers with lower infrared luminosity do not possess massive bulges, and that the gas is stripped during the initial encounter of their progenitors. A comparison of the CO and radio luminosities of the NE and SW component show them to have comparable radio and CO flux ratios of f(NE)/f(SW) ~0.6, possibly indicating that the amount of star-forming molecular gas in the progenitors is correlated with the supernovae rate. The estimate of molecular gas masses of the nuclei and the extent of the radio emission are used to infer that the nuclei of IR 14348-1447 have gas densities comparable to the cores of elliptical galaxies.Comment: LaTex, 5 pages with 1 postscript and 1 jpg figure, ApJ Letters, in pres

The IRAS Revised Bright Galaxy Sample (RBGS)

IRAS flux densities, redshifts, and infrared luminosities are reported for all sources identified in the IRAS Revised Bright Galaxy Sample (RBGS), a complete flux-limited survey of all extragalactic objects with total 60 micron flux density greater than 5.24 Jy, covering the entire sky surveyed by IRAS at Galactic latitude |b| > 5 degrees. The RBGS includes 629 objects, with a median (mean) sample redshift of 0.0082 (0.0126) and a maximum redshift of 0.0876. The RBGS supersedes the previous two-part IRAS Bright Galaxy Samples, which were compiled before the final ("Pass 3") calibration of the IRAS Level 1 Archive in May 1990. The RBGS also makes use of more accurate and consistent automated methods to measure the flux of objects with extended emission. Basic properties of the RBGS sources are summarized, including estimated total infrared luminosities, as well as updates to cross-identifications with sources from optical galaxy catalogs established using the NASA/IPAC Extragalactic Database (NED). In addition, an atlas of images from the Digitized Sky Survey with overlays of the IRAS position uncertainty ellipse and annotated scale bars is provided for ease in visualizing the optical morphology in context with the angular and metric size of each object. The revised bolometric infrared luminosity function, phi(L_ir), for infrared bright galaxies in the local Universe remains best fit by a double power law, phi(L_ir) ~ L_ir^alpha, with alpha = -0.6 (+/- 0.1), and alpha = -2.2 (+/- 0.1) below and above the "characteristic" infrared luminosity L_ir ~ 10^{10.5} L_solar, respectively. (Abridged)Comment: Accepted for publication in the Astronomical Journal. Contains 50 pages, 7 tables, 16 figures. Due to astro-ph space limits, only 1 of 26 pages of Figure 1, and 1 of 11 pages of Table 7, are included; full resolution Postscript files are available at http://nedwww.ipac.caltech.edu/level5/March03/IRAS_RBGS/Figures/ . Replacement: Corrected insertion of Fig. 15 (MethodCodes.ps) in LaTe

HST NICMOS imaging of z~2, 24 micron-selected Ultraluminous Infrared Galaxies

We present Hubble Space Telescope NICMOS H-band imaging of 33 Ultraluminous Infrared Galaxies (ULIRGs) at z~2 that were selected from the 24 micron catalog of the Spitzer Extragalactic First Look Survey. The images reveal that at least 17 of the 33 objects are associated with interactions. Up to one fifth of the sources in our sample could be minor mergers whereas only 2 systems are merging binaries with luminosity ratio <=3:1, which is characteristic of local ULIRGs. The rest-frame optical luminosities of the sources are of the order 10^10-10^11 L_sun and their effective radii range from 1.4 to 4.9 kpc. The most compact sources are either those with a strong active nucleus continuum or those with a heavy obscuration in the mid-infrared regime, as determined from Spitzer Infra-Red Spectrograph data. The luminosity of the 7.7 micron feature produced by polycyclic aromatic hydrocarbon molecules varies significantly among compact systems whereas it is typically large for extended systems. A bulge-to-disk decomposition performed for the 6 brightest (m_H<20) sources in our sample indicates that they are best fit by disk-like profiles with small or negligible bulges, unlike the bulge-dominated remnants of local ULIRGs. Our results provide evidence that the interactions associated with ultraluminous infrared activity at z~2 can differ from those at z~0.Comment: ApJ, in press. Document revised to match the journal versio