Day 936

Friday.


1507.08292
CMB lensing and scale dependent new physics
Hojjati, Linder

CMB lensing has become a new cosmological probe, carrying rich information on the matter power spectrum and distances over the redshift range z~1-4.  Investigate the role of scale dependent new physics, such as from modified gravity, neutrino mass, and cold (low sound speed) dark energy, and its signature on CMB lensing.  The distinction between different scale dependences, and the different redshift dependent weighting of the matter power spectrum entering into CMB lensing and other power spectra, imply that CMB lensing can probe simultaneously a diverse range of physics.  Highlight the role of arc minute resolution polarization experiments for distinguishing between physical effects.


1507.08336
No galaxy left behind: accurate measurements with the faintest objects in the Dark Energy Survey
Suchyta, Huff, .. Melchir, ... Gaztanaga, ... Leistedt, Peiris, Ross, Rykoff, Sheldon, et al

Accurate statistical measurement with large imaging surveys has traditionally required throwing away a sizable fraction of the data.  This is because most measurements have relied on selecting nearly complete samples, where variations in the composition of the galaxy population with seeing, depth, or other survey characteristics are small.  Introduce a new measurement method that aims to minimize this wastage, allowing precision measurement for any class of stars or galaxies detectable in an imaging survey.  Implement the proposal in Balrog, a software package which embeds fake objects in real imaging in order to accurately characterize measurement biases.  Demonstrate this technique with an angular clustering measurement using DES data.  First show that recovery of the injected galaxies depends on a wide variety of survey characteristics in the same way as the real data.  Then construct a flux-limited sample of the faintest galaxies in DES, chosen specifically for their sensitivity to depth and seeing variations.  Using the synthetic galaxies as randoms in the standard Lande-Szalay correlation function estimator suppresses the effects of variable survey selection by at least 2 orders of magnitude.   With this correction, the measured angular clustering is found to be in excellent agreement with that of a matched sample drawn from much deeper, higher-resolution space-based COSMOS imaging; over angular scales of 0.004 deg<theta<0.2 deg; find a best-fit scaling amplitude between the DES and COSMOS measurements of 1.00±0.09. Expect this methodology to be broadly useful for extending the statistical reach of measurements in a wide variety of coming imaging surveys.


1507.08530
Observational signatures of self-destructive civilisations
Stevens, Forgan, O'Malley-James

Address the possibility that intelligent civilizations that destroy themselves could present signatures observable by humanity.  Placing limits on the number of self-destroyed civilizations in the MW has strong implications for the final three terms in Drake's Equation, and would allow identification of which classes of solution to Fermi's paradox fit wit the evidence (or lack thereof).  Using the Earth as an example, consider a variety of scenarios in which humans could extinguish their own technological civilization.  Each scenario presents some form of observable signature that could be probed by astronomical campaigns to detect and chartreuse extrasolar planetary systems.  Some observables are unlikely to be detected at interstellar distances, but some scenarios are likely to produce significant changes in atmospheric composition that could be detected serendipitously with next-generation telescopes.  In some cases, the timing of the observation would prove crucial to detection, as the decay of signatures is rapid compared to humanity's communication lifetime.  In others, the signatures persist on far longer timescales.


1507.08552
How astronomers view education and public outreach
Dang, Russo

Over the past few years, there have been a few studies on the development of an interest in science and scientists' views on public outreach.  Yet, to date, there has been no global study regarding astronomers' views on these matters.  Through the completion of the survey by 155 professional astronomers online and in person during the 28th IAU general assembly in 2012, explored the development of an interest for astronomy and their views on time constraints and budget restriction regarding public outreach activities.  Find that astronomers develop an interest in astronomy between the ages of 4-6 but that the decision to undertake a career in astronomy often comes during late adolescence.  Also discuss the claim that education and public outreach is regarded an optional task rather than a scientist's duty.  The study revealed that many astronomers think there should be a larger percentage of their research that should be invested into outreach activities, calling for a change in grant policies.