The ISM at high redshifts: ALMA results and a look to the future

ALMA is revolutionizing the way we study and understand the astrophysics of galaxies, both as a whole and individually. By exploiting its unique sensitivity and resolution to make spatially and spectrally resolved images of the gas and dust in the interstellar medium (ISM), ALMA can reveal new information about the relationship between stars and gas, during and between galaxies' cycles of star formation and AGN fueling. However, this can only be done for a modest number of targets, and thus works in the context of large samples drawn from other surveys, while providing parallel deep imaging in small fields around. Recent ALMA highlights are reviewed, and some areas where ALMA will potentially make great contributions in future are discussed.Comment: 8 pages, Review contribution to the Third Year ALMA conference, Tokyo, December 201

A Ghost at ω1\omega_1

In the final chain of the countable powerset functor, we show that the set at index $\omega_1$, regarded as a transition system, is not strongly extensional because it contains a "ghost" element that has no successor even though its component at each successor index is inhabited. The method, adapted from a construction of Forti and Honsell, also gives ghosts at larger ordinals in the final chain of other subfunctors of the powerset functor. This leads to a precise description of which sets in these final chains are strongly extensional

The differential magnification of high-redshift ultraluminous infrared galaxies

A class of extremely luminous high-redshift galaxies has recently been detected in unbiased submillimetre-wave surveys using the Submillimetre Common-User Bolometer Array (SCUBA) camera at the James Clerk Maxwell Telescope. Most of the luminosity of these galaxies is emitted from warm interstellar dust grains, and they could be the high-redshift counterparts of the low-redshift ultraluminous infrared galaxies (ULIRGs). Only one - SMM J02399-0136 - has yet been studied in detail. Three other very luminous high-redshift dusty galaxies with well determined spectral energy distributions in the mid-infrared waveband are known - IRAS F10214+4724, H1413+117 and APM 08279+5255. These were detected serendipitously rather than in unbiased surveys, and are all gravitationally lensed by a foreground galaxy. Two - H 1413+117 and APM 08279+5255 - appear to emit a significantly greater fraction of their luminosity in the mid-infrared waveband as compared with both low-redshift ULIRGs and high-redshift submillimetre-selected galaxies. This can be explained by a systematically greater lensing magnification of hotter regions of the source as compared with cooler regions: differential magnification. This effect can confuse the interpretation of the properties of distant ultraluminous galaxies that are lensed by intervening galaxies, but offers a possible way to investigate the temperature distribution of dust in their nuclei on scales of tens of parsecs.Comment: 5 pages, 1 two-panel figure, 2 one-panel figures. In press at MNRAS. Final proof versio

SCUBA deep fields and source confusion

Deep submillimetre(submm)-wave surveys made over the last three years using the SCUBA camera at the 15-m James Clerk Maxwell Telescope (JCMT) have revealed a new population of very luminous high-redshift galaxies. The properties of this population, and their contribution to the intensity of the extragalactic background radiation field are described briefly, especially in the context of the SCUBA lens survey (carried out since 1997 by Ian Smail, Rob Ivison, Jean-Paul Kneib and the author: a full description of the survey and references to supporting work can be found in the recent catalogue paper). The potential problems caused by source confusion in the large 15-arcsec SCUBA observing beam for the identification and follow up of the results are discussed. The effects of confusion are not important for the study of 850-micron SCUBA sources brighter than about 2 mJy.Comment: 6 pages. 1 4-panel figure. 1 two-panel figures. To be published in proceedings of Deep Fields meeting (Garching October 2000