Day 1006

Thursday.


Nature 527, 204-207
A small nearby star with an Earth-like planet
Zachary et al

M-dwarf stars -- H-burning stars that are smaller than 60^ of the size of the Sun -- are the most common class of star in our Galaxy and outnumber Sun-like stars by a ratio of 12:1.  Recent results have shown that M dwarfs host Earth-sized planets in great numbers: the average number of M-dwarf plants that are between 0.5 to 1.5 times the size of Earth is at least 1.4 per star.  The nearest such planets known to transit their star are 39 parsecs away, too distant for detailed follow-up observations to measure the planatery masses or to study their atmospheres.  Here, report observations of GJ 1132b,  a planet with a size of 1.2 Earth radii that is transiting a mall star 12 pc away.  Doppler mass measurement yields a density consistent with an Earth-like bulk composition, similar to the compositions of the 6 known exoplanets with masses less than 6x that of the Earth and precisely measured densities.  Receiving 19x more stellar radiation than the Earth, the planet is too hot to be habitable but is cool enough to support a substantial atmosphere, one that has probably been considerably depleted of H.  Because the host star is nearby and only 21% the radius of the Sun, existing and upcoming telescopes will be able to observe the composition and dynamics of the planetary atmosphere.


1511.03284
Revisiting the classics: Is [Mg/Fe] a good proxy for galaxy formation time-scales?
Martín-Navarro

In the local Universe, massive early-type galaxies exhibit enhanced [Mg/Fe] ratios, which has been traditionally interpreted as the result of a rapid (tau<1 Gyr) collapse.  However, recent claims of a non-universal, steep IMF call for a revision of this standard interpretation.  In the present work, show how the simultaneous consideration of a high [Mg/Fe] and a steep IMF slope would imply unreasonably short (tau~7 Myr) and intense (SFR~1e5 Msun/yr) formation events for massive early-type galaxies.  Discuss possible caveats and explanations to this apparent inconsistency, and suggest that further IMF determinations, both in the local Universe and at high z, are necessary to better understand the problem.


1511.03391
Crowdsourcing quality control for Dark Energy Survey images
Melchior, Sheldon, et al

Developed a crowdsourcing web application for image quality control employed by DES.  Dubbed the "DES exposure checker", it renders science-grade images directly to a web browser and allows users to mark problematic features from a set of predefined classes.  Users can also generate custom labels and thus help identify previously unknown problem classes.  User reports are fed back to hardware and software experts to help mitigate and eliminate recognized issues.  Report on the implementation of the application and the experience with its over 100 users, the majority of which are professional or prospective astronomers but not data management experts.  Discuss aspects of user training and engagement, and demonstrate how problem reports have been pivotal to rapidly correct artifacts which would likely have been too subtle or infrequent to be recognized otherwise.  Conclude with a number of important lessons learned, suggest possible improvements, and recommend this collective exploratory approach for future astronomical surveys or wither extensive data sets wit a sufficiently large user base.  Also release open-source code of the web application and host and online demo version.


1511.03594
The Gini Coefficient as a tool for image family identification in strong lensing systems with multiple images
Florian, Gladers, Li, Sharon

The sample of cosmo SL systems has been strongly growing in recent years; the sample will reach into the thousands with the advent of the next generation of space-based survey telescopes.  The accuracy of SL models relies on robust ID of multiple image families of lensed galaxies.  For the most massive lenses, often more than one background galaxy is magnified and multiply-imaged, and even in the cases of only a single lensed source, identification of counter images is not always robust.  Recently, it was shown that the Gini coefficient in space-telescope-quality imaging is a measurement of galaxy morphology that is relatively well-preserved by strong gravitational lensing.  Here, investigate its usefulness as a diagnostic for the purposes of image family identification and show that it can remove some of the degeneracies encountered when using color as the sole diagnostic, and can do so without the need for additional observations since whenever a color is available, two Gini coefficients are as well.