We study the recently observed JellyFish galaxies (JFGs), which are found tohave their gas content ram-pressure stripped away in galaxy clusters. Thesegalaxies are observed to have an enhanced star formation rate of about 0.2 dexcompared with a control sample of the same stellar mass in their disks. Wemodel the increase in the star formation efficiency as a function ofinteracluster medium pressure and parametrize the cold gas content of thegalaxies as a function of cluster-centric distance. We show that regarding theexternal pressure as a positive feedback results in agreement with the observeddistribution of enhanced star formation in the JFGs if clouds are shielded fromevaporation by magnetic fields. Our results predict that satellites with halomass $< 10^{11}M_{\odot}$ moving with Mach numbers $\mathcal{M}\approx2$, andinclination angles below 60 degrees, are more likely to be detected as JFGs.

Metasurface optics provide an ultra-thin alternative to conventionalrefractive lenses. A present challenge is in realizing metasurfaces thatexhibit tunable optical properties and achromatic behavior across the visiblespectrum. Here, we report the design, fabrication, and characterization ofmetasurface lenses ("metalenses") that use asymmetric TiO2 nanostructures toinduce a polarization-dependent optical response. By rotating the polarizationof linearly-polarized input light, the focal length of a 40 micrometer-diametermetalens is tuned from 220-550 micrometers with nearly diffraction-limitedperformance. We show that imparting a wavelength-dependent polarizationrotation on incident light enables achromatic focusing over a wide band of thevisible spectrum, 483-620 nm. We use this property to demonstrate varifocalcolor imaging with white light from a halogen source. Tunable achromaticmetalenses may be useful for applications in imaging and display.

We present SCUBA-2 450$\mu$m and 850$\mu$m data of the mature redshift 2cluster CLJ1449. We combine this with archival Herschel data to explore thestar forming properties of CLJ1449. Using high resolution ALMA and JVLA data weidentify potentially confused galaxies, and use the Bayesian inference toolXID+ to estimate fluxes for them. Using archival optical and near infrared datawith the energy-balance code CIGALE we calculate star formation rates, andstellar masses for all our cluster members, and find the star formation ratevaries between 20-1600M$_{\odot}$yr$^{-1}$ over the entire 3Mpc radial range.The central 0.5Mpc region itself has a total star formation rate of800$\pm$200M$_{\odot}$yr$^{-1}$, which corresponds to a star formation ratedensity of (1.2$\pm$0.3)$\times$10$^{4}$M$_{\odot}$yr$^{-1}$Mpc$^{-3}$, whichis approximately five orders of magnitude greater than expected field values.When comparing this cluster to those at lower redshifts we find that there isan increase in star formation rate per unit volume towards the centre of thecluster. This indicates that there is indeed a reversal in the starformation/density relation in CLJ1449. Based on the radial star-formation ratedensity profile, we see evidence for an elevation in the star formation ratedensity, even out to radii of 3Mpc. At these radii the elevation could be anorder of magnitude greater than field values, but the exact number cannot bedetermined due to ambiguity in the redshift associations. If this is the caseit would imply that this cluster is still accreting material which is possiblyinteracting and undergoing vigorous star-formation.

Feedback processes from active galactic nuclei (AGN) are thought to play acrucial role in regulating star formation in massive galaxies. Previous studiesusing \textit{Herschel} have resulted in conflicting conclusions as to whetherstar formation is quenched, enhanced, or not affected by AGN feedback. We usenew deep 850 $\mu$m observations from the SCUBA-2 Cosmology Legacy survey(S2CLS) to investigate star formation in a sample of X-ray selected AGN,probing galaxies up to $L_{0.5-7~\rm keV} = 10^{46}$ erg s$^{-1}$. Here wepresent the results of our analysis on a sample of 1957 galaxies at $ 1 < z < 3$, using both S2CLS and ancilliary data at seven additional wavelengths(24--500 \mcm) from \textit{Herschel} and \textit{Spitzer}. We perform astacking analysis, binning our sample by redshift and X-ray luminosity. Byfitting analytical spectral energy distributions (SEDs) to decomposecontributions from cold and warm dust, we estimate star-formation rates foreach `average' source. We find that the average AGN in our sample resides in astar-forming host galaxy, with SFRs ranging from 80 - 600 $M_{\odot}$year$^{-1}$. Within each redshift bin, we see no trend of SFR with X-rayluminosity, instead finding a flat distribution of SFR across $\sim$3 orders ofmagnitude of AGN luminosity. By studying instantaneous X-ray luminosities andSFRs, we find no evidence that AGN activity affects star formation in hostgalaxies.