Oral Presentation

ALMA's contribution to the high redshift legacy of Herschel

Author(s): Stephen Eales (Cardiff University) Aris Amvrosiadis (Durham University)

Presenter: Tom Bakx (Nagoya University)

The Herschel surveys have detected more than half a million sub-millimeter galaxies (SMGs), allowing for the selection of both gravitational lenses and rare hyper-luminous galaxies. Gravitational lensing reveals previously-hidden populations of sub-mm sources. In turn, the unlensed sources are the most intensely star-forming systems in the Universe. Direct observations with SMA, NOEMA, and ALMA have identified their nature in the dust continuum, revealing the morphology of dust-obscured star-formation at high redshift. We will present the latest ALMA results revealing the dynamical behaviour inside these star-bursting galaxies in the early Universe. We will complement this with the results from redshift searches with NOEMA, IRAM 30m, ACA and ALMA, that aim to be 90% spectroscopically-complete by mid 2020.

Aside from individual lens studies, observations of large samples of Herschel-selected lensed SMGs can provide a unique probe of the intervening Universe and its cosmology. However, increasing the sample of the gravitational lenses still remains a challenge as our current selection methods are only based on relatively-crude flux cuts. Here, we show that optical and near-infrared imaging are an essential tool for identifying the gravitational lenses within the Herschel samples by finding the foreground lensing galaxies. We improve our method to near 100% accuracy, contrary previous work (only ~40%). Based on near-IR VIKING data, we will present the first measure of the lensing probability as a function of selection flux. We will then outline our ongoing work with ALMA in combination with multi-wavelength imaging to target confirmed lensed sources, and conversely, to target unlensed sources - the most intensely starforming systems in the known Universe.