Day 892

Monday.


1505.05876
Are rotating planes of satellite galaxies ubiquitous?
Phillips, Cooper, Bullock, Boylan-Kolchin

Compare the dynamics of satellite galaxies in the SDSS to simple models in order to test the hypothesis that a large fraction of satellites co-rotate in coherent planes.  Confirm the previously-reported excess of co-rotating satellite pairs located near diametric opposition with respect to the host, but show that this signal is unlikely to be due to rotating discs (or planes) of satellites.  In particular, no overabundance of co-rotating satellites pairs is observed within ~20-50 degrees of direct opposition, as would be expected for planar distributions inclined relative to the LoS.  Instead, the excess co-rotation for satellite pairs within ~10 degrees of opposition is consistent with random noise associated with undersampling of an underlying isotropic velocity distribution.  Conclude that at most 10% of the hosts in the sample harbor co-rotating satellite planes (as traced by the luminous satellite population).


1505.05885
Beam calibration of radio telescopes with drones
Chang, Monstein, Refregier, Amara, Glauser, Casura

Present a multifrequency far-field beam map for the 5m dish telescope at the Bleien Observatory measured using a commercially available drone.  Describe the hexacopter drone used in this experiment, the design of the flight pattern, and the data analysis scheme.  This is the first application of this calibration method to a single dish radio telescope in the far-field.  The high S/N data allows to characterize the beam pattern with high accuracy out to at least the 4th side-lobe.  The resulting 2d beam pattern is compared with that derived from a more traditional calibration approach using an astronomical calibration source.  Discuss the advantages of this method compared to other beam calibration methods.  Results show that this drone-based technique is very promising for ongoing and future radio experiments, where the knowledge of the beam pattern is key to obtaining high- accuracy cosmological and astronomical measurements.  


1505.06187
Time delay measurements for the cluster-lensed sextuple quasar SDSS J2222+2745
Dahle, Gladders, et al

As the title says.  Time delay between images A and B, the two most highly magnified images, is measured to be tau_AB=43.0±4.5 days (95% CL), consistent wit previous model predictions for this lens system.  The strong intrinsic variability of the quasar also allows derivation of a tentative time delay value of tau_CA=694+23-4 days between image C and A, in spite of modest overlap between their light curves in the current data set.  Longer values of tau_CA<830 days cannot yet be firmly excluded, but further monitoring should be sufficient to confirm the tentative value during 2015.  Image C, which is predicted to lead all the other lensed quasar images, has undergone a sharp, monotonic flux increase of 60-75% during 2014.  The same brightening is predicted to occur in images A and B during 2016.  The amplitude of this rise indicates that time delays involving all 6 known images in this system, including those of the demagnified central images D-F, will be obtainable from further ground-based monitoring of this system during the next few years.