5 research outputs found
The Additional Representative Images for Legacy (ARI-L) project for the ALMA Science Archive
The Additional Representative Images for Legacy (ARI-L) project is a European
Development project for ALMA Upgrade approved by the Joint ALMA Observatory
(JAO) and the European Southern Observatory (ESO), started in June 2019. It
aims to increase the legacy value of the ALMA Science Archive (ASA) by bringing
the reduction level of ALMA data from Cycles 2-4 close to that of data from
more recent Cycles processed for imaging with the ALMA Pipeline. As of mid-2021
more than 150000 images have been returned to the ASA for public use. At its
completion in 2022, the project will have provided enhanced products for at
least 70% of the observational data from Cycles 2-4 processable with the ALMA
Pipeline. In this paper we present the project rationale, its implementation,
and the new opportunities offered to ASA users by the ARI-L products. The ARI-L
cubes and images complement the much limited number of archival image products
generated during the data quality assurance stages (QA2), which cover only a
small fraction of the available data for those Cycles. ARI-L imaging products
are highly relevant for many science cases and significantly enhance the
possibilities for exploiting archival data. Indeed, ARI-L products facilitate
archive access and data usage for science purposes even for non-expert data
miners, provide a homogeneous view of all data for better dataset comparisons
and download selections, make the archive more accessible to visualization and
analysis tools, and enable the generation of preview images and plots similar
to those possible for subsequent Cycles.Comment: 15 pages. Accepted for publication in PAS
An Overview of the 2014 ALMA Long Baseline Campaign
A major goal of the Atacama Large Millimeter/submillimeter Array (ALMA) is to
make accurate images with resolutions of tens of milliarcseconds, which at
submillimeter (submm) wavelengths requires baselines up to ~15 km. To develop
and test this capability, a Long Baseline Campaign (LBC) was carried out from
September to late November 2014, culminating in end-to-end observations,
calibrations, and imaging of selected Science Verification (SV) targets. This
paper presents an overview of the campaign and its main results, including an
investigation of the short-term coherence properties and systematic phase
errors over the long baselines at the ALMA site, a summary of the SV targets
and observations, and recommendations for science observing strategies at long
baselines. Deep ALMA images of the quasar 3C138 at 97 and 241 GHz are also
compared to VLA 43 GHz results, demonstrating an agreement at a level of a few
percent. As a result of the extensive program of LBC testing, the highly
successful SV imaging at long baselines achieved angular resolutions as fine as
19 mas at ~350 GHz. Observing with ALMA on baselines of up to 15 km is now
possible, and opens up new parameter space for submm astronomy.Comment: 11 pages, 7 figures, 2 tables; accepted for publication in the
Astrophysical Journal Letters; this version with small changes to
affiliation
The 2014 ALMA Long Baseline Campaign: An Overview
A major goal of the Atacama Large Millimeter/submillimeter Array (ALMA) is to make accurate images with resolutions of tens of milliarcseconds, which at submillimeter (submm) wavelengths requires baselines up to ~15 km. To develop and test this capability, a Long Baseline Campaign (LBC) was carried out from September to late November 2014, culminating in end-to-end observations, calibrations, and imaging of selected Science Verification (SV) targets. This paper presents an overview of the campaign and its main results, including an investigation of the short-term coherence properties and systematic phase errors over the long baselines at the ALMA site, a summary of the SV targets and observations, and recommendations for science observing strategies at long baselines. Deep ALMA images of the quasar 3C138 at 97 and 241 GHz are also compared to VLA 43 GHz results, demonstrating an agreement at a level of a few percent. As a result of the extensive program of LBC testing, the highly successful SV imaging at long baselines achieved angular resolutions as fine as 19 mas at ~350 GHz. Observing with ALMA on baselines of up to 15 km is now possible, and opens up new parameter space for submm astronomy