Search for Hα Emitters at z ∼ 7.8: A Constraint on the Hα-based Star Formation Rate Density

We search for Hα emitters at z ∼ 7.8 in four gravitationally lensed fields observed in the Hubble Frontier Fields program. We use the Lyman break method to select galaxies at the target redshift and perform photometry in the Spitzer/IRAC 5.8 μm band to detect Hα emission from the candidate galaxies. We find no significant detections of counterparts in the IRAC 5.8 μm band, and this gives a constraint on the Hα luminosity function (LF) at z ∼ 7.8. We compare the constraint with previous studies based on rest-frame UV and far-infrared observations using the correlation between the Hα luminosity and the star formation rate. Additionally, we convert the constraint on the Hα LF into an upper limit for the star formation rate density (SFRD) at this epoch assuming the shape of the LF. We examine two types of parameterization of the LF and obtain an upper limit for the SFRD of log 10 ( ρ SFR [ M ⊙ yr − 1 Mpc − 3 ] ) ≲ − 1.1 at z ∼ 7.8. With this constraint on the SFRD, we present an independent probe into the total star formation activity including dust-obscured and unobscured star formation at the Epoch of Reionization.

2. Creation revealed

‘Creation revealed’ examines key observations on planetary systems. Astronomers at first could probe the Universe only through the medium of visible light. In the early 1600s, the invention of the telescope allowed the Universe to be observed in much greater detail. With the discovery of ‘heat rays’, the seeds of infrared astronomy were planted. Meanwhile, throughout the course of the nineteenth century, one of the grandest unifications in physics was accomplished. It was discovered that the forces of electricity and magnetism were in fact different aspects of the same phenomenon: electromagnetism. Other important topics include blackbody radiation; infrared observations of young stellar objects; and the Atacama Large Millimeter/Submillimeter Array (ALMA).

Precipitation Products’ Inter–Comparison over East and Southern Africa 1983–2017

During recent decades East Africa (EA) and Southern Africa (SA) have experienced an intensification of hydrological hazards, such as floods and droughts, which have dramatically affected the population, making these areas two of the regions of the African continent most vulnerable to these hazards. Thus, precipitation monitoring and the evaluation of its variability have become fundamentally important actions through the analysis of long-term data records. In particular, satellite-based precipitation products are often used because they counterbalance the sparsity of the rain gauge networks which often characterize these areas. The aim of this work is to compare and contrast the capabilities of three daily satellite-based products in EA and SA from 1983 to 2017. The selected products are two daily rainfall datasets based on high-resolution thermal infrared observations, TAMSAT version 3 and CHIRPS, and a relatively new global product, MSWEP version 2.2, which merges satellite-based, rain gauge and re-analysis precipitation data. The datasets have been directly intercompared, avoiding the traditional rain gauge validation. This is done by means of pairwise comparison statistics at 0.25° spatial resolution and daily time scale to assess rain–detection and quantitative estimate capabilities. Monthly climatology and spatial distribution of seasonality are analyzed as well. The time evolution of the statistical indexes has been evaluated in order to analyze the stability of the rain detection and estimation performances. Considerable agreement among the precipitation products emerged from the analysis, in spite of the differences occurring in specific situations over complex terrain, such as mountainous and coastal regions and deserts. Moreover, the temporal evolution of the statistical indices has demonstrated that the agreement between the products improved over time, with more stable capabilities in identifying precipitating days and estimating daily precipitation starting in the second half of the 1990s.

Optical and Near-Infrared Monitoring of Gamma-ray Binaries Hosting Be Stars

Optical and near-infrared observations are compiled for the three gamma-ray binaries hosting Be stars: PSR B1259−63, LSI+61 303, and HESS J0632+057. The emissions from the Be disk are considered to vary according to the changes in its structure, some of which are caused by interactions with the compact object (e.g., tidal forces). Due to the high eccentricity and large orbit of these systems, the interactions—and, hence the resultant observables—depend on the orbital phase. To explore such variations, multi-band photometry and linear polarization were monitored for the three considered systems, using two 1.5 m-class telescopes: IRSF at the South African Astronomical Observatory and Kanata at the Higashi–Hiroshima Observatory.

Novel methods to probe exoplanet atmospheres using ground-based spectrophotometry

<p>Ground-based spectrophotometric observations of transiting exoplanet atmospheres conventionally rely on correcting for instrumental and telluric systematics in the light curves by using reference stars that are simultaneously observed. However, this approach often leads to sub-optimal corrections due to multiple accounts on which the target and reference star spectra can be affected by systematics differently through the night, ultimately limiting the achievable precision and accuracy on the measurement of planetary atmospheric signatures. We introduce a new method based on Gaussian Processes regression to address this challenge by extracting the transmission or emission spectrum without relying explicitly on the reference stars. Our new method overcomes the necessity of using reference stars and opens up the doors to ground-based atmospheric observations of exoplanets orbiting bright host stars (e.g. those discovered by TESS) that intrinsically lack proper reference stars. We present results from the application of our method to a broad sample of exoplanets observed in the optical and near-infrared using Gemini/GMOS and Keck/MOSFIRE. We also discuss the challenges and possible solutions arising from stellar variability towards combining high precision ground-based low-resolution spectroscopy observations in complementarity with future infrared observations from HST and JWST.</p>