1509.05406
The imprint of the cosmic supermassive black hole growth history on the 21 cm background radiation
Tanaka, O'Leary, Perna
The redshifted 21 cm transition line of H tracks the thermal evolution of the neutral IGM at "cosmic dawn," during the emergence of the first luminous astrophysical objects (~100 Myr after the Big Bang) but before these objects ionized the IGM (~400-800Myr after the BB). Because X-rays, in particular, are likely to be the chief energy courier for heating the IGM, measurements of the 21 cm signature can be used to infer knowledge about the first astrophysical X-ray sources. Using analytic arguments and a numerical population synthesis algorithm, argue that the progenitors of SMBHs should be the dominant source of hard astrophysical X-rays --- and thus the primary driver of IGM heating and the 21 cm signature --- at redshifts z<20, if (i) they grow readily from the remnants of Pop III stars and (ii) produce X-rays in quantities comparable to what is observed from AGN and high-mass X-ray binaries. Show that models satisfying these assumptions dominate over contributions to IGM heating from stellar populations, and cause the 21 cm brightness temperature to rise at z>20. An absence of such a signature in the forthcoming observational data would imply that SMBH formation occurred later (e.g. via absence of such a signature in the forthcoming observational data would imply that SMBH formation occurred later (e.g. via so-called direct collapse scenarios), that it was not a common occurrence in early galaxies and protogalaxies, or that it produced far fewer X-rays than empirical trends at lower redshifts, either due to intrinsic dimness (radiative inefficiency) or Compton-think obscuration close to the source.
1509.05420
The Apache Point Observatory Galactic Evolution Experiment (APOGEE)
Majewski, et al
APOGEE, on of the SDSS-III programs, has now completed its systematic, homogeneous spectroscopic survey sampling all major populations of the MW. After a 3 year observing campaign on the Sloan 2.5m telescope, APOGEE has collected a half million high res (R~22,500), high S/N (>100), infrared (1.51-1.70 microns) spectra for 146,000 stars, with time series information via repeat visits to most of these stars. This paper describes the motivations for the survey and its overall design --- hardware, field placement, target selection, operations --- and gives an observer of these aspects as well as the data reduction, analysis and products. An index is also given to the complement of technical papers that describe various critical survey opponents in detail. Finally, discuss the achieved survey performance and illustrate the variety of potential uses of the data products by way of a number of science demonstration, which span from time series analysis of stellar spectral variations and radial velocity variations from stellar companions, to spatial maps of kinematics, metallicity and abundance patterns across the Galaxy and as a function of gas, to new views of the ISM, the chemistry of star clusters, and the discovery of rare stellar species. As part of SDSS-III DR12, all of the APOGEE data projects are now publicly available.
1509.05504
Detection of signals from a possible extrasolar technological civilization is one of the challenging effort of sciences. Propose using natural telescopes made of single or binary gravitational lensings systems to magnify leakage of EM signs from a remote planet harbors Extra Terrestrial Intelligent (ETI) technology. The gravitational microlensing surveys are monitoring a large area of Galactic bulge for searching microlensing events and each year they find more than 2000 events. These lenses are capable of playing the role of natural telescopes and in some occasions they can magnify signals from planets orbiting around the source stars in the gravitational microlensing systems. Assuming that frequency of EM waves used for telecommunication in ETIs is similar to ours, propose follow-up observation of microlensing events with radio telescopes such as SKA, LFD, and MWA. Amplifying signals from leakage of broadcasting of Earth-like civilizations will allow detection up to the centre of MW galaxy. Analysis show that in binary microlensing systems, the probability of amplification of signals from ETIs is more likely than that n the single microlensing events. Finally, propose a practical observational strategy with the follow-up observation of binary microlensing events with the SKA as a new program for searching ETIs. The probability of detection in the opimisitc values for the factors of Drake equation is around one event per year.
1509.05619
Prediction of galaxy ellipticities and reduction of shape noise in cosmic shear measurements
Croft, Freement, Schuster, Schafer
The intrinsic scatter in the ellipticities of galaxies about the mean shape, known as "shape noise," is the most important source of noise in WL shear measurements. Several approaches to reducing shape noise have recently been put forward. Using information beyond photometry, such as radio polarization and optical spectroscopy. Investigate how well the intrinsic ellipticities of galaxies can be predicted using other, exclusively photometric parameters. These parameters (such as galaxy colors) are already available in the data and do not necessitate additional, often expensive observations, Apply two regression techniques, generalized additive models (GAM) and projection pursuit regression (PPR) to the publicly released data catalog of CHFTLenS. In the simple analysis, find that the individual galaxy ellipticities can indeed be predicted from other photometric parameters to better precision than the scatter about the mean ellipticity. This means that without additional observations beyond photometry the ellipticity contribution to the shear can be measured to higher precision, comparable to using a large sample of galaxies. The best-fit model, achieved using PPR, yields a gain equivalent to having 114.3% more galaxies. Using only parameters unaffected by lensing (e.g.~surface brightness, color) the gain is only ~12%.
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