The Cologne Database for Molecular Spectroscopy, CDMS: a useful tool for astronomers and spectroscopists

The 21-cm absorption profile is detected in the sky-averaged radio spectrum, but is much stronger than predicted, suggesting that the primordial gas might have been cooler than predicted. As the first stars heated hydrogen in the early Universe, the 21-cm hyperfine line—an astronomical standard that represents the spin-flip transition in the ground state of atomic hydrogen—was altered, causing the hydrogen gas to absorb photons from the microwave background. This should produce an observable absorption signal at frequencies of less than 200 megahertz (MHz). Judd Bowman and colleagues report the observation of an absorption profile centred at a frequency of 78 MHz that is about 19 MHz wide and 0.5 kelvin deep. The profile is generally in line with expectations, although it is deeper than predicted. An accompanying paper by Rennan Barkana suggests that baryons were interacting with cold dark-matter particles in the early Universe, cooling the gas more than had been expected. After stars formed in the early Universe, their ultraviolet light is expected, eventually, to have penetrated the primordial hydrogen gas and altered the excitation state of its 21-centimetre hyperfine line. This alteration would cause the gas to absorb photons from the cosmic microwave background, producing a spectral distortion that should be observable today at radio frequencies of less than 200 megahertz1. Here we report the detection of a flattened absorption profile in the sky-averaged radio spectrum, which is centred at a frequency of 78 megahertz and has a best-fitting full-width at half-maximum of 19 megahertz and an amplitude of 0.5 kelvin. The profile is largely consistent with expectations for the 21-centimetre signal induced by early stars; however, the best-fitting amplitude of the profile is more than a factor of two greater than the largest predictions2. This discrepancy suggests that either the primordial gas was much colder than expected or the background radiation temperature was hotter than expected. Astrophysical phenomena (such as radiation from stars and stellar remnants) are unlikely to account for this discrepancy; of the proposed extensions to the standard model of cosmology and particle physics, only cooling of the gas as a result of interactions between dark matter and baryons seems to explain the observed amplitude3. The low-frequency edge of the observed profile indicates that stars existed and had produced a background of Lyman-α photons by 180 million years after the Big Bang. The high-frequency edge indicates that the gas was heated to above the radiation temperature less than 100 million years later.

An absorption profile centred at 78 megahertz in the sky-averaged spectrum

We are developing the Precision Array for Probing the Epoch of Re-ionization (PAPER) to detect 21 cm emission from the early universe, when the first stars and galaxies were forming. We describe the overall experiment strategy and architecture and summarize two PAPER deployments: a four-antenna array in the low radio frequency interference (RFI) environment of Western Australia and an eight-antenna array at a prototyping site at the NRAO facilities near Green Bank, WV. From these activities we report on system performance, including primary beam model verification, dependence of system gain on ambient temperature, measurements of receiver and overall system temperatures, and characterization of the RFI environment at each deployment site. We present an all-sky map synthesized between 139 MHz and 174 MHz using data from both arrays that reaches down to 80 mJy (4.9 K, for a beam size of 2.15e−5 sr at 156 MHz), with a 10 mJy (620 mK) thermal noise level that indicates what would be achievable with better foreground subtraction. We calculate angular power spectra (C� ) in a cold patch and determine them to be dominated by point sources, but with contributions from galactic synchrotron emission at lower radio frequencies and angular wavemodes. Although the sample variance of foregrounds dominates errors in these power spectra, we measure a thermal noise level of 310 mK at � = 100 for a 1.46 MHz band centered at 164.5 MHz. This sensitivity level is approximately 3 orders of magnitude in temperature above the level of the fluctuations in 21 cm emission associated with re-ionization.

The precision array for probing the epoch of re-ionization: eight station results

We study the implications of the Great Recession for voting for antiestablishment parties, as well as for general trust and political attitudes, using regional data across Europe. We find a strong relationship between increases in unemployment and voting for nonmainstream parties, especially populist ones. Moreover, unemployment increases in tandem with declining trust toward national and European political institutions, though we find only weak or no effects of unemployment on interpersonal trust. The correlation between unemployment and attitudes toward immigrants is muted, especially for their cultural impact. To explore causality, we extract the component of increases in unemployment explained by the precrisis structure of the economy, in particular the share of construction in regional value added, which is strongly related both to the buildup preceding and the bursting of the crisis. Our results imply that crisis- driven economic insecurity is a substantial determinant of populism and political distrust.

/pdf/the-european-trust-crisis-and-the-rise-of-populism-466x3vo5gq.pdf

The European Trust Crisis and the Rise of Populism

This paper analyses the effect of corporate governance structure’s 
development on the total amount and composition of the remuneration packages 
received by Spanish listed firms’ board members. We study the possible influence of 
the firms’ ownership structure and board features on remuneration policies. Our main 
results suggest that firm’s size and profitability, together with certain corporate 
governance characteristics, such as the ownership concentration, the directors’ 
ownership stake and the existence of a nomination and remuneration committee, affect 
the directors’ compensation schemes in the Spanish stock market.

Corporate governance structure and board of directors remuneration policies: evidence from Spain

[1] An analysis of multiscale observations of a substorm auroral breakup are presented which clarify the role of wave dispersion in the formation of elemental (<100 m) auroral structure. At coarse resolution (all-sky white light camera, 1 frame/s), observations fit the established substorm morphology—namely, arc brightening, formation of spatial distortions, and breakup into multiple “rayed” structures. At fine-scale resolution (electron multiplying charge-coupled device [EMCCD] camera, 9-degree field of view, prompt emission filter, 30 frames/s), an entirely different type of coherence is observed. The “arc,” as identified at lower resolution, is observed to be a dynamic structure composed of bifurcating elemental arcs that propagate outward from the center of an “arc packet.” This dynamic process is well captured in time-brightness histories (keograms) along a cut bisecting the structure. The observations are interpreted with respect to theoretical predictions for inertial Alfven wave dispersion. Specifically, the arc packets are interpreted as the B⊥ projection of the parallel electric field within the Alfven resonant cone. Prebreakup observations are found to be qualitatively consistent with this model. However, some difficulties are encountered for the more active postbreakup period. The article includes a discussion of perspective considerations in interpreting small-scale auroral features; in particular, it is shown that the “rayed” appearance of discrete breakup aurora is, in fact, a consequence of sharply kinked sheets viewed obliquely.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2008JA013122

Wave dispersion and the discrete aurora: New constraints derived from high-speed imagery

Evolutionary design of a satellite thermal control system: Real experiments for a CubeSat mission

The distribution of 12C16O J = 9 → 8 (1.037 THz) emission has been mapped in OMC-1 at 35 points with 84'' resolution. This is the first map of this source in this transition and only the second velocity-resolved ground-based observation of a line in the THz frequency band. There is emission present at all points in the map, a region roughly 4' × 6' in size, with peak antenna temperature dropping only near the edges. Away from the Orion KL outflow, the velocity structure suggests that most of the emission comes from the OMC-1 photon-dominated region, with a typical line width of 3-6 km s-1. Large velocity gradient modeling of the emission in J = 9 → 8 and six lower transitions suggests that the lines originate in regions with temperatures around 120 K and densities of at least 103.5 cm-3 near θ1C Ori and at the Orion bar, and from 70 K gas at around 104 cm-3 southeast and west of the bar. These observations are among the first made with the 0.8 m Smithsonian Astrophysical Observatory Receiver Lab Telescope, a new instrument designed to observe at frequencies above 1 THz from an extremely high and dry site in northern Chile.

http://iopscience.iop.org/article/10.1086/422831/pdf

A map of omc-1 in co j = 9¿8

The distribution of 12C16O J=9-8 (1.037 THz) emission has been mapped in OMC-1 at 35 points with 84" resolution. This is the first map of this source in this transition and only the second velocity-resolved ground-based observation of a line in the terahertz frequency band. There is emission present at all points in the map, a region roughly 4' by 6' in size, with peak antenna temperature dropping only near the edges. Away from the Orion KL outflow, the velocity structure suggests that most of the emission comes from the OMC-1 photon-dominated region, with a typical linewidthof 3-6 km/s. Large velocity gradient modeling of the emission in J=9-8 and six lower transitions suggests that the lines originate in regions with temperatures around 120 K and densities of at least 10^(3.5) cm^(-3) near theta^(1) C Ori and at the Orion Bar, and from 70 K gas at around 10^(4) cm^(-3) southeast and west of the bar. These observations are among the first made with the 0.8 m Smithsonian Astrophysical Observatory Receiver Lab Telescope, a new instrument designed to observe at frequencies above 1 THz from an extremely high and dry site in northern Chile.

A map of OMC-1 in CO 9-8

[1] Experimental results obtained with the 449-MHz Poker Flat Incoherent Scatter Radar (PFISR) show unusual features in both the ion line and plasma line measurements during an auroral breakup event. The features are a greatly enhanced flat ion acoustic spectrum (believed to indicate the presence of an additional peak at zero Doppler), and two peaks in the plasma line spectrum. Similar spectral morphologies are observed during active HF ionospheric modification experiments and are considered unmistakable indications of Strong Langmuir Turbulence (SLT). In SLT theory, the central peak in ion acoustic spectrum is caused by Bragg scattering from non-propagating density fluctuations (cavitons), and the two peaks in the plasma line spectrum are associated with (1) Langmuir waves trapped in the cavitons, at the cold plasma frequency, and (2) a “free mode” at the Langmuir frequency. Free modes are radiated Langmuir waves from collapsing cavitons that follow the linear dispersion relation. The observed turbulence was confined to a thin layer (∼10-km) centered at ∼230 km altitude.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2011GL050288

Marcos Diaz

Papers

Wave dispersion and the discrete aurora: New constraints derived from high-speed imagery

Evolutionary design of a satellite thermal control system: Real experiments for a CubeSat mission

A map of omc-1 in co j = 9¿8

A map of OMC-1 in CO 9-8

Anomalous ISR echoes preceding auroral breakup: Evidence for strong Langmuir turbulence