Day 498

Sunday.  4 days of astro-ph to catch up...

1308.5237
Processing color in astronomical imagery
Arcand et al

Astronomical images can span the entire EM spectrum from radio to IR to X-ray and gamma rays.  How do the color choices affect the comprehension of the science behind the images? What is the best way to represent data to a non-expert?  Should choices be based on aesthetics, scientific veracity, or is it possible to satisfy both?  This paper review just one choice out of many in image processing:  color.  The choice of color is one of the most fundamental when creating an image taken with modern telescopes.  Briefly explore the concept of the image as translation, particularly in the case of astronomical images from invisible portions of the EM spectrum.  After placing modern astronomical imagery and photography in general in the context of its historical beginnings, review the standards (or lack thereof) in making the basic choice of color.  Discuss the possible implications for selecting one color palette over another in the context of the appropriateness of using these images as science communication products with a specific focus on how the non-expert perceives these images and how that affects their trust in science.  Finally, share new data sets that begin to look at these issues in scholarly research and discuss the need for a more robust examination of this and other related topics in the future to better understand the implications for science communications.

1308.5353
A critical assessment of photometric redshift methods: a CNDELS investigation
Dahlen, .. Faber, ... Acquaviva, ... Newman, ... et al

CANDELS photo-z method investigation from 11 participants.  Photometry includes U-band through MIR filters, and derived using the TFIT method.  Comparing the results, find that there is no particular code or set of template SEDs that results in significantly better photometric redshifts compared to others.  However, find codes producing the lowest scatter and outlier fraction utilize a training sample to optimize photo-z by adding zero-point offsets, template adjusting or adding extra smoothing errors.  These results therefore stress the importance of the training procedure.  Find a strong dependence of the photo-z accuracy on the signal-to-noise ratio of the photometry.  On the other hand, find a weak dependence of the photo-z scatter with redshift and galaxy color.  Find that most photo-z codes quote z errors (e.g., 68% CL) that are too small compared to that expected from the spectroscopic control sample.  Find that all codes show a statistically significant bias in the photo-z.  However, the bias is in all cases smaller than the scatter, the latter therefore dominates the errors.  Finally, find that combining results from multiple codes significantly decreases the photometric z scatter and outlier fraction.  Discuss different ways of combining data to produce accurate photo-z and error estimates.

1308.5636
Bayesian model selection for dark energy using weak lensing forecasts
Debono

The next generation of weak lensing probes can place strong constraints on cosmological parameters by measuring the mass distribution and geometry of the low redshift universe.  Show that a future all-sky tomographic cosmic shear survey with design properties similar to Euclid can provide the statistical accuracy required to distinguish between different dark energy models.  Using a fiducial cosmological model which includes cold dark matter, baryons, massive neutrinos (hot dark matter), a running primordial spectral index and possible spatial curvature as well as dark energy perturbations, calculate Fisher matrix forecasts for different dynamical dark energy models.  Using a Bayesian evidence calculation show how well a future weak lensing survey could do in distinguishing between a cosmological constant and dynamical dark energy.

1308.5480
Flaglets for studying the large-scale structure of the Universe
Leistedt, Peiris, McEwen

Exploit a sampling theorem to obtain exact Fourier-Laguerre and flaglet transforms, such that band-limited signals can [be] analyzed and reconstructed at floating point accuracy on a finite number of voxels on the ball.  Present a potential application of the flaglet transform for finding voids in galaxy surveys and studying the large-scale structure of the Universe.

1308.5681
H-ATLAS: estimating redshifts of Herschel sources from sub-mm fluxes
Pearson, et al

0.5M sources in H-ATLAS; get photo-z from assumed rest-frame SED.  Use 40 sources with known redshifts in 0.5<z<4.2 to derive suitable average template for high-z H-ATLAS sources.  Find that a template with two dust components T_c=23.9 K, T_h = 46.9 K and ratio of mass of cold dust to mass of warm dust of 30.1 provides a good fit to the rest-frame fluxes of the sources in the calibration sample.  Use a jackknife technique to estimate the accuracy of the redshifts estimated with this template, finding a root mean square of Delta z/(1+z) = 0.26.  For sources for which there is prior information that they lie at z>1, estimate that the RMS of Delta z/(1+z) = 0.12.  Use this template to estimate the redshift distribution for the sources detected in the H_ATLAS equatorial fields, finding a bimodal distribution with a mean redshift of 1.2, 1.9 and 2.5 for 250, 350, and 500 um selected sources respectively.

1308.5711
Probing the effect of gravitational microlensing on the measurements of the Rossiter-McLauglin effect
Oshagh, et al

Rossiter-McLaughlin effect: transit across a rotating star (with rotation axis having perpendicular component to the LoS) shows red/blue shifts of the star (caused by the stellar rotation) as the planet transits across the star.  In the RM effects, the contribution of the planet's gravitational microlensing effect is neglected.  Theoretical studies have shown that the planet's microlensing can affect the transit light-curve and in some extreme cases cause the transit depth to vanish.  In this letter, present the results of the quantitative analysis of microlensing on the RM effect.  Results indicate that for massive planets in on long period orbits, the planet's microlensing will have considerable contribution to the star's RV measurements.  Present the details of this study; discuss analysis and results.


1308.5797
Four open questions in massive star evolution
Meynet et al

(1) origin of slowly rotating, non-evolved, N-rich stars.  Propose that these stars may originate from initially fast rotating stars whose surface has been breaked down.  (2) evolutionary status of alpha-Cygni variables (stars which exhibit non-radial pulsations: some portions of the stars are contracting while the other parts expand; supergiant stars of spectral types B or A; pulsations typically have periods of days to weeks, while multiple pulsation periods exists and will beat; variation in brightness is of order 0.1 mag associated with radial pulsations; Deneb, or alpha-Cygni exhibits fluctations in brightness between mag 1.21 and 1.29).  According to their pulsation properties, these stars should be post red supergiant stars.  Hwoever, some stars at least present surface abundances indicating that they should be pre red supergiant stars.  How to reconcile these two contradictory requirements?  (3) the various SN types which are the end point of the evolution of stars with initial masses between 18 and 30 Msun, i.e., the most massive stars which go through a red supergiant phase during their lifetime.  Do they produce types IIP, IIL, IIn, IIb or Ib SNe, or do they end without producing any SN event?  (4) discuss reasons why so few progenitors of type Ibc SNe have yet been detected.