Searching For Dark Matter Subhalos In the Fermi-LAT Second Source Catalog

The dark matter halo of the Milky Way is expected to contain an abundance of smaller subhalos. These subhalos can be dense and produce potentially observable fluxes of gamma rays. In this paper, we search for dark matter subhalo candidates among the sources in the Fermi-LAT Second Source Catalog which are not currently identified or associated with counterparts at other wavelengths. Of the nine high-significance, high-latitude (|b|>60 degrees), non-variable, unidentified sources contained in this catalog, only one or two are compatible with the spectrum of a dark matter particle heavier than approximately 50-100 GeV. The majority of these nine sources, however, feature a spectrum that is compatible with that predicted from a lighter (~5-40 GeV) dark matter particle. This population is consistent with the number of observable subhalos predicted for a dark matter candidate in this mass range and with an annihilation cross section of a simple thermal relic (sigma v~3x10^{-26} cm^3/s). Observations in the direction of these sources at other wavelengths will be necessary to either reveal their astrophysical nature (as blazars or other active galactic nuclei, for example), or to further support the possibility that they are dark matter subhalos by failing to detect any non-gamma ray counterpart.Comment: 8 pages, 4 figure

Concurrent and predictive validity of the Universal Nonverbal Intelligence Test and the Leiter International Performance Scale - Revised

The relationship between two tests of cognitive ability measured nonverbally and the relative capability of intellectual constructs measured by those tests to predict academic achievement (operationalized by end of the year group achievement tests) was examined. One hundred elementary and middle school students were administered the Universal Nonverbal Intelligence Test (UNIT) and the Leiter International Performance Scale - Revised in counter-balanced order; reading, math, and language scores from Terra Nova were matched with 37 cases in the sample. Correlation coefficients describing the relationship among global scores within the IT and between the UNIT and the Leiter-R were statistically significant (p \u3c .001) and ranged from .33 for the. UNIT Memory Quotient/Leiter-R Fluid Reasoning scores t .90 for the UNIT Full Scale IQ/UNIT Reasoning Quotient and UNIT Nonsymbolic Quotient/UNIT Reasoning Quotient. The coefficient between the UNIT and Leiter-R Full Scale IQ scores was .72 (Q \u3c .001). Mean differences between the UNIT and Leiter-R Full Scale were significant with the UNIT Full Scale IQ score being approximately five points higher than the Leiter-R, t. = 4.73, )2. \u3c .001. Effect size for the t-test was modest, .35. Based on stepwise multiple regression analyses, the UNIT Full Scale IQ predicted all three areas of academic achievement significantly better than the Leiter-R Full Scale IQ score, with the variance accounted for by the UNIT Full Scale IQ score ranging from 39 percent to 55 percent (p. \u3c .01). The Leiter-R contributed an additional 2 percent of variance. In addition, a number of the UNIT and Leiter-R global scores were statistically significant predictors of achievement (e.g., UNIT Reasoning Quotient, Memory Quotient, Leiter-R Reasoning). Results are consistent with prior research that has found the UNIT and Leiter-R to provide comparable measures of general intelligence. However, this is the first study to suggest that the UNIT may be superior to the Leiter-R in its relative capability to predict academic achievement. School psychologists and administrators will find these results useful in choosing assessment instruments to evaluate the increasingly culturally and linguistically diverse population of students

Payload/orbiter contamination control requirement study: Computer interface

The MSFC computer facilities, and future plans for them are described relative to characteristics of the various computers as to availability and suitability for processing the contamination program. A listing of the CDC 6000 series and UNIVAC 1108 characteristics is presented so that programming requirements can be compared directly and differences noted

Towards low-latency real-time detection of gravitational waves from compact binary coalescences in the era of advanced detectors

Electromagnetic (EM) follow-up observations of gravitational wave (GW) events will help shed light on the nature of the sources, and more can be learned if the EM follow-ups can start as soon as the GW event becomes observable. In this paper, we propose a computationally efficient time-domain algorithm capable of detecting gravitational waves (GWs) from coalescing binaries of compact objects with nearly zero time delay. In case when the signal is strong enough, our algorithm also has the flexibility to trigger EM observation before the merger. The key to the efficiency of our algorithm arises from the use of chains of so-called Infinite Impulse Response (IIR) filters, which filter time-series data recursively. Computational cost is further reduced by a template interpolation technique that requires filtering to be done only for a much coarser template bank than otherwise required to sufficiently recover optimal signal-to-noise ratio. Towards future detectors with sensitivity extending to lower frequencies, our algorithm's computational cost is shown to increase rather insignificantly compared to the conventional time-domain correlation method. Moreover, at latencies of less than hundreds to thousands of seconds, this method is expected to be computationally more efficient than the straightforward frequency-domain method.Comment: 19 pages, 6 figures, for PR

Payload/orbiter contamination control requirement study: Preliminary contamination mission support plan

Progress is reported on the mission support plan and those support activities envisioned to be applicable and necessary during premission and postmission phases of the Spacelab program. The purpose, role, and requirements of the contamination control operations for the first two missions of the Spacelab equipped Space Transportation System are discussed. The organization of the contamination control operation and its relationship to and interfaces with other mission support functions is also discussed. Some specific areas of contamination to be investigated are treated. They are: (1) windows and viewports, (2) experiment equipment, (3) thermal control surfaces, (4) the contaminant induced atmosphere (as differentiated from the normal ambient atmosphere at the orbit altitude), and (5) optical navigation instruments

No Indications of Axion-Like Particles From Fermi

As very high energy (~100 GeV) gamma rays travel over cosmological distances, their flux is attenuated through interactions with the extragalactic background light. Observations of distant gamma ray sources at energies between ~200 GeV and a few TeV by ground-based gamma ray telescopes such as HESS, however, suggest that the universe is more transparent to very high energy photons than had been anticipated. One possible explanation for this is the existence of axion-like-particles (ALPs) which gamma rays can efficiently oscillate into, enabling them to travel cosmological distances without attenuation. In this article, we use data from the Fermi Gamma Ray Space Telescope to calculate the spectra at 1-100 GeV of two gamma ray sources, 1ES1101-232 at redshift z=0.186 and H2356-309 at z=0.165, and use this in conjunction with the measurements of ground-based telescopes to test the ALP hypothesis. We find that the observations can be well-fit by an intrinsic power-law source spectrum with indices of -1.72 and -2.1 for 1ES1101-232 and H2356-309, respectively, and that no ALPs or other exotic physics is necessary to explain the observed degree of attenuation.Comment: 7 pages, 4 figures. v3: Matches published version, the analysis of H2356-309 is revised, no change in conclusion

CoGeNT, DAMA, and Light Neutralino Dark Matter

Recent observations by the CoGeNT collaboration (as well as long standing observations by DAMA/LIBRA) suggest the presence of a $\sim 5$-10 GeV dark matter particle with a somewhat large elastic scattering cross section with nucleons ($\sigma\sim 10^{-40}$ cm$^2$).Within the context of the minimal supersymmetric standard model (MSSM), neutralinos in this mass range are not able to possess such large cross sections, and would be overproduced in the early universe. Simple extensions of the MSSM, however, can easily accommodate these observations. In particular, the extension of the MSSM by a chiral singlet superfield allows for the possibility that the dark matter is made up of a light singlino that interacts with nucleons largely through the exchange of a fairly light ($\sim$30-70 GeV) singlet-like scalar higgs, \hi. Such a scenario is consistent with all current collider constraints and can generate the signals reported by CoGeNT and DAMA/LIBRA. Furthermore, there is a generic limit of the extended model in which there is a singlet-like pseudoscalar higgs, \ai, with \mai\sim \mhi and in which the $\chi^0\chi^0$ and b\anti b, s\anti s coupling magnitudes of the \hi and \ai are very similar. In this case, the thermal relic abundance is automatically consistent with the measured density of dark matter if \mchi is sufficiently small that \chi^0\chi^0\to b\anti b is forbidden.Comment: 6 pages, published versio

On The Origin Of The Gamma Rays From The Galactic Center

The region surrounding the center of the Milky Way is both astrophysically rich and complex, and is predicted to contain very high densities of dark matter. Utilizing three years of data from the Fermi Gamma Ray Space Telescope (and the recently available Pass 7 ultraclean event class), we study the morphology and spectrum of the gamma ray emission from this region and find evidence of a spatially extended component which peaks at energies between 300 MeV and 10 GeV. We compare our results to those reported by other groups and find good agreement. The extended emission could potentially originate from either the annihilations of dark matter particles in the inner galaxy, or from the collisions of high energy protons that are accelerated by the Milky Way's supermassive black hole with gas. If interpreted as dark matter annihilation products, the emission spectrum favors dark matter particles with a mass in the range of 7-12 GeV (if annihilating dominantly to leptons) or 25-45 GeV (if annihilating dominantly to hadronic final states). The intensity of the emission corresponds to a dark matter annihilation cross section consistent with that required to generate the observed cosmological abundance in the early universe (sigma v ~ 3 x 10^-26 cm^3/s). We also present conservative limits on the dark matter annihilation cross section which are at least as stringent as those derived from other observations.Comment: 13 pages, 11 figure

The Interplay Between Collider Searches For Supersymmetric Higgs Bosons and Direct Dark Matter Experiments

In this article, we explore the interplay between searches for supersymmetric particles and Higgs bosons at hadron colliders (the Tevatron and the LHC) and direct dark matter searches (such as CDMS, ZEPLIN, XENON, EDELWEISS, CRESST, WARP and others). We focus on collider searches for heavy MSSM Higgs bosons ($A$, $H$, $H^{\pm}$) and how the prospects for these searches are impacted by direct dark matter limits and vice versa. We find that the prospects of these two experimental programs are highly interrelated. A positive detection of $A$, $H$ or $H^{\pm}$ at the Tevatron would dramatically enhance the prospects for a near future direct discovery of neutralino dark matter. Similarly, a positive direct detection of neutralino dark matter would enhance the prospects of discovering heavy MSSM Higgs bosons at the Tevatron or the LHC. Combining the information obtained from both types of experimental searches will enable us to learn more about the nature of supersymmetry.Comment: 22 pages, 28 figure