Day 1452

Friday.

1808.05208
The evolution of the UV-to-mm extragalactic background light: evidence for a top-heavy initial mass function?
Cowley et al

Present predictions for the UV-to-mm extragalactic background light (EBL) from the GALFORM SAM of galaxy formation.  Combine GALFORM with the GRASIL radiative transfer code for computing fully self-consistent UV-to-mm SEDs for each simulated galaxy, accounting for the absorption and re-emission of stellar radiation by interstellar dust.  The predicted EBL is in near-perfect agreement with recent observations over the whole UV-to-mm spectrum, as is the evolution of the cosmic SED over the z range for which observations are available (z<~1).  Show that approximately 90% of the EBL is produced at z<2 although this shifts to higher z for sub-mm wavelengths.  Assess whether one of the more controversial aspects of the model, a top-heavy IMF for galaxies undergoing dynamically-triggered bursts of SF, is necessary in order to reproduce the EBL, and find that variant models with a universal solar-neighborhood IMF cannot produce as good agreement with EBL observations over the whole UV-to-mm spectrum.


1808.05223
Galaxy ellipticity measurements n the near-infrared for weak lensing
Lee, Chary, Wright

Investigate the value of the NIR imaging from upcoming surveys for constraining the ellipticities of galaxies.  Select galaxies between 0.5<z<3 that are brighter than expected Euclid sensitivity limits from the GOODS-S and N fields in CANDELS.  The co-added CANDELS/HST V+I and J+H imagine are degraded in resolution and sensitivity to simulate Euclid-quality optical and NIR images.  Then run GALFIT on these simulated images and find that optical and NIR provide similar performance in measuring galaxy ellipticities at 0.5<z<3.  At z>1.0, the NIR-selected source density is higher by a factor of 1.4 and therefore the scatter in NIR-derived ellipticities is about 30% smaller, implying a more precise ellipticity measurement.  The good performance of the NIR is mainly because galaxies have an intrinsically smoother light distribution in the NIR bands than in the optical, the latter tracing the clumpy SF regions.  In addition, the NIR bands have a higher surface brightness per pixel than the optical images, while being less affected by dust attenuation.  Despite the worse spatial sampling and resolution of Euclid NIR compared to optical, the NIR approach yields equivalent or more precise galaxy ellipticity measurements.  If systematics that affect shape such as dithering strategy and PSF under sampling can be mitigated, inclusion of the NIR can improve galaxy ellipticity measurements over all redshifts.  This is particularly important for upcoming weak lensing surveys, such as with Euclid and WFIRST.


1808.05422
Accurate prediction of H$_3$O$^+$ and D$_3$O$^+$ sensitivity coefficients to probe a variable proton-to-electron mass ratio
Owens, et al

The mass sensitivity of the vibration-rotation-inversion transitions of H_3 ^16O^+, H_3 ^18O^+, and D_3 ^16O^+ is investigated variationally using the nuclear motion program TROVE.  The calculations utilize new high-level ab initio potential energy and dipole moment surfaces.  Along with the mass dependence, frequency data and Einstein A coefficients are computed for all transitions probed.  Particular attention is paid to the Delta|k|=3 and Delta|k-l|=3 transitions comprising the accidentally coinciding |J,K=0, v_2=0^+> and |J,K=3, v_2=0^-> rotation-inversion energy levels.  The newly computed probes exhibit sensitivities comparable to their ammonia and methanol counterparts, thus demonstrating their potential for testing the cosmological stability of the proton-to-electron mass ratio.  The theoretical TROVE results are in close agreement with sensitivities obtained using the nonrigid and rigid inverter approximate models, confirming that the ab initio theory used in the present study is adequate.