Constraining DM through 21 cm observations

Beyond reionization epoch cosmic hydrogen is neutral and can be directly observed through its 21 cm line signal. If dark matter (DM) decays or annihilates the corresponding energy input affects the hydrogen kinetic temperature and ionized fraction, and contributes to the Ly_alpha background. The changes induced by these processes on the 21 cm signal can then be used to constrain the proposed DM candidates, among which we select the three most popular ones: (i) 25-keV decaying sterile neutrinos, (ii) 10-MeV decaying light dark matter (LDM) and (iii) 10-MeV annihilating LDM. Although we find that the DM effects are considerably smaller than found by previous studies (due to a more physical description of the energy transfer from DM to the gas), we conclude that combined observations of the 21 cm background and of its gradient should be able to put constrains at least on LDM candidates. In fact, LDM decays (annihilations) induce differential brightness temperature variations with respect to the non decaying/annihilating DM case up to Delta_delta T_b=8 (22) mK at about 50 (15) MHz. In principle this signal could be detected both by current single dish radio telescopes and future facilities as LOFAR; however, this assumes that ionospheric, interference and foreground issues can be properly taken care of.Comment: 9 pages, submitted to MNRA

Particle energy cascade in the intergalactic medium

We study the development of high-energy (Ein <= 1 TeV) cascades produced by a primary electron of energy Ein injected into the intergalactic medium (IGM). To this aim we have developed the new code MEDEA (Monte Carlo Energy Deposition Analysis) which includes Bremsstrahlung and inverse Compton (IC) processes, along with H/He collisional ionizations and excitations, and electron-electron collisions. The cascade energy partition into heating, excitations and ionizations depends primarily not only on the IGM ionized fraction, xe, but also on redshift, z, due to IC on cosmic microwave background (CMB) photons. While Bremsstrahlung is unimportant under most conditions, IC becomes largely dominant at energies Ein >= 1 MeV. The main effect of IC at injection energies Ein <= 100 MeV is a significant boost of the fraction of energy converted into low-energy photons (h\u3bd < 10.2 eV) which do not further interact with the IGM. For energies Ein >= 1 GeV CMB photons are preferentially upscattered within the X-ray spectrum (h\u3bd > 104 eV) and can free stream to the observer. Complete tables of the fractional energy depositions as a function of redshift, Ein and ionized fraction are given. Our results can be used in many astrophysical contexts, with an obvious application related to the study of decaying/annihilating dark matter (DM) candidates in the high-z Universe

Radio views of cosmic reionization

We use numerical simulations of cosmic reionization and radiative processes related to the HI 21 cm emission line to produce synthetic radio maps as seen by next generation radio telescopes that will operate at low radio frequencies (e.g. LOFAR). Two different scenarios, in which the end of reionization occurs early (z approx 13) or late (z approx 8) depending on the Initial Mass Function (IMF) of the first stars and ionizing photon escape fraction, have been explored. For each of these models we produce synthetic HI 21 cm emission maps by convolving the simulation outputs with the provisional LOFAR sampling function in the frequency range 76-140 MHz. If reionization occurs late, LOFAR will be able to detect individual HI structures on arcmin scales, emitting at a brightness temperature of approx 35 mK as a 3-sigma signal in about 1000 hours of observing time. In the case of early reionization, the detection would be unlikely, due to decreased sensitivity and increased sky temperatures. These results assume that ionospheric, interference and foreground issues are fully under control.Comment: 6 pages, 3 figures, Minor changes following referee repor

Corridor-Wide Surveillance Using Unmanned Aircraft Systems Phase II: Freeway Incident Detection Using Unmanned Aircraft Systems (Part A)

69A3551947136, 79075-00-SUB ADuring the second phase of this study, the team collected field data with unmanned aerial vehicles (UAVs) at different elevations and distances from the road to analyze the performance of a background subtraction algorithm for vehicle detection. Validation analyses were carried out and their results indicated that a detection rate with an accuracy of up to 92% can be reached using the background subtraction algorithm. The results of the ANOVA test confirmed that the drone\u2019s distance from the road was the only main factor associated with vehicle detection percentage (at the 95% confidence level). It was also determined that, depending on drone type, elevation can affect the detection rate based on the interaction plots created. The experiences from the field activities that took place during this phase of the project were incorporated into the previously developed protocol for the use of UAVs in corridor surveillance. The protocol was also updated with the steps that must be followed for several scenarios and these can be incorporated in future studies on the use of drones in transportation applications

Influencing Travel Behavior via an Open-Source Platform Phase 1: Implementation of OneBusAway

69A3551947136, #79070-00-SUB ADeveloped and rural areas close to urban centers can use public transit as an effective strategy to reduce traffic congestion. Transit can improve mobility, accessibility, and quality of life of the residents of a region when perceived as reliable and efficient. However, unreliable or inefficient transit systems could lead to low ridership. Innovations in transit services are required to enhance the sustainability of urban centers and to increase the accessibility to jobs and other activities for people living in rural areas. Transportation professionals must develop strategies to improve the transit system and increase its ridership. One of these strategies is to provide users with real-time transit data through a real-time passenger information (RTPI) system. Transit users can then utilize this information to their advantage and comfort by reducing actual waiting times and the perception of waiting time at the stop. This solution increases ridership by improving the riders\u2019 experience when using this service. This report represents phase one of a two-phase project. The main objective of phase one is to implement the open-source platform OneBusAway in the Integrated Transit System of Mayag\ufcez (TIM, for its Spanish acronym) to have real-time information readily available for modeling and studying the impact on ridership. The methodology followed in this investigation was divided into four tasks, from literature review and understanding of OBA to its implementation. The preliminary results of this investigation show that OBA correctly identifies all the routes and stops of the system, and accurately estimates (predictions) for arrival time to specific stops while the buses are in operation. The main objective of phase two will be to explore how travelers choose between driving their own vehicles or using public transit, Transportation Network Companies (TNC) services, or other modes (e.g., carpooling, micro-mobility), and how to influence this behavior (i.e., increase transit ridership) using OBA

Trigger and Aperture of the Surface Detector Array of the Pierre Auger Observatory

The surface detector array of the Pierre Auger Observatory consists of 1600 water-Cherenkov detectors, for the study of extensive air showers (EAS) generated by ultra-high-energy cosmic rays. We describe the trigger hierarchy, from the identification of candidate showers at the level of a single detector, amongst a large background (mainly random single cosmic ray muons), up to the selection of real events and the rejection of random coincidences. Such trigger makes the surface detector array fully efficient for the detection of EAS with energy above $3\times 10^{18}$ eV, for all zenith angles between 0$^\circ$ and 60$^\circ$, independently of the position of the impact point and of the mass of the primary particle. In these range of energies and angles, the exposure of the surface array can be determined purely on the basis of the geometrical acceptance.Comment: 29 pages, 12 figure

Ultrahigh energy neutrinos at the Pierre Auger observatory

The observation of ultrahigh energy neutrinos (UHEνs) has become a priority in experimental astroparticle physics. UHEνs can be detected with a variety of techniques. In particular, neutrinos can interact in the atmosphere (downward-going ν) or in the Earth crust (Earth-skimming ν), producing air showers that can be observed with arrays of detectors at the ground. With the surface detector array of the Pierre Auger Observatory we can detect these types of cascades. The distinguishing signature for neutrino events is the presence of very inclined showers produced close to the ground (i.e., after having traversed a large amount of atmosphere). In this work we review the procedure and criteria established to search for UHEνs in the data collected with the ground array of the Pierre Auger Observatory. This includes Earth-skimming as well as downward-going neutrinos. No neutrino candidates have been found, which allows us to place competitive limits to the diffuse flux of UHEνs in the EeV range and above.P. Abreu ... K. B. Barber ... J. A. Bellido ... R. W. Clay ... M. J. Cooper ... B. R. Dawson ... T. A. Harrison ... A. E. Herve ... V. C. Holmes ... J. Sorokin ... P. Wahrlich ... B. J. Whelan ... et al

Pingutcula lithophytica C. Panfet-Vald\ue9s & P. Temple (Lentibulariaceae Rich.), a new species from the central region of cuba

Volume: 37Start Page: 90End Page: 9

MUHLENBERGIA JAIME-HINTONII (POACEAE: CHLORIDOIDEAE), A NEW SPECIES FROM NUEVO LE 3N, MEXICO

Volume: 18Start Page: 685End Page: 69