Science Highlight




ACA Observatory Filler Programs

In Cycles 5 and 6, the ALMA Observatory observed nine Atacama Compact Array (ACA) filler projects. The programs were designed to fill specific gaps in the ACA observing schedule. The programs were selected based on input from scientists at the Joint ALMA Observatory (JAO) and the ALMA Regional Centers (ARCs). The proposed programs were reviewed by staff in the Department of Science Operations (DSO) at the JAO with final approval by the ALMA Director. The data was released through the ALMA Science Archive with no proprietary period. The original announcements can be found at https://almascience.org/news/alma-announces-new-aca-observatory-filler-programs-for-cycle-5 and https://almascience.org/news/alma-announces-aca-observatory-filler-programs-for-cycle-6.

The programs are listed in the following Table along with their main publications:


PID (linked to ASA) Title Description Primary Articles
2017.A.00043.T Time evolution of CO & H2O in the Martian atmosphere during a large-scale dust storm We propose to use the ACA to monitor the evolution of CO and H2O in the Martian atmosphere, on a timescale of weeks and on a global size scale, during the current dust storm. The CO profile will be used to derive the global wind structure and vertical atmospheric temperature profile. The submm H2O line will be observed for the first time; its' profile will give the vertical H2O abundance and the ACA spatial resolution will enable us to derive the H2O distribution over the planet. As well, we can can measure the H2O/HDO ratio, which is predicted to be affected by the exact origin of gaseous H2O. Dust storms are expected to affect the abundances of both of these molecules, as well as their vertical temperature profiles. We can test these predictions with the new observations, giving a better understanding of the Mars weather during and after such global events. The data can be compared with the latest Mars atmosphere models, as well as in-situ measurements by the orbiters and landers currently on the surface.


2017.A.00053.S ALMA ACA Band-8 observatory project: Mapping fine structure lines of neutral atomic carbon in local bright galaxies The fine structure lines of neutral atomic carbon have been proposed to be robust tracers of the molecular gas, offering a new way for us to probe the molecular gas mass in extragalactic environments, especially for high-redshift galaxies, whose CO(1-0) lines are very difficult to access. Here we propose an ALMA Band-8 ACA observatory project mapping the 492GHz [CI](1-0) transition in a group of infrared bright nearby galaxies, who are located within the 22:00h-01:30h LST range. The goal is to study the spatial distribution of the atomic carbon gas, compared with the existing images of other gas tracers such as CO(1-0), to test the proposed scenario. The kinematical information from the proposed data will also allow us to understand the dynamical properties, and possibly revealing detailed structures.


2017.A.00054.S ACA Observatory Project: SMC Band 6 CO and continuum mapping This project will complete the Cycle 5 observatory program to obtain a large area map (~ 0.34ox 1o) of the North bar in the Small Magellanic Cloud (SMC) in 12CO(1-0), 12CO(2-1), H(30)α, and the continuum.

Agliozzo et al. 2021

Neelamkodan et al. 2021

Tokuda et al. 2021

2017.A.00056.S The nature of Planck compact sources at 353 microns High frequency studies are a priority for ALMA, but in practical terms requires nearby (~1 degree) compact phase calibrators. The Planck satellite covered the same bands as ALMA soon will, detecting >40000 bright (>671 mJy) compact sources at 857 GHz, close to 1 per sq. degree and bright enough to be used as phase calibrators. However, the resolution is 4.4 and the positional uncertainty is 37, so the precise locations and source morphologies (i.e. compact or extended) are unknown. We plan to use the ACA in ALMA Band 6, which has a 40 FoV, to determine through short 30 second snapshots their morphology and positions. In this pilot, we select approximately 1500 sources at LST 22:0001:30 and lower than declination > 40 that appear in the Planck catalog at both 857 GHz and 217 GHz and not flagged as extended. This survey will have archival value both by improving the ALMA calibrator database and providing a sort of ALMA Galaxy Zoo finding any interesting sources, such as lensed high-z galaxies and mergers, for further study.  
2018.A.00046.S The host properties and environment of high-redshift radio galaxies with ACA Over 40 high-redshift radio-AGN in the ELAIS-S1 field will be observed in the Band 6 continuum. The observations will provide a statistical understanding of radio-AGN at high redshift (z~2) and assess the star-formation activity in the local environment of these galaxies. Messias et al. 2021
2018.A.00047.S Shock-induced chemistry in the CSEs of late-type stars: a pilot study Band 3 and Band 6 spectral scans will be obtained for a sample of late-type stars in transition from the Asymptotic Giant Branch to the Planetary Nebula phase. The spectral survey will trace lines found in the shocked materials as well as typical lines of molecules found in circumstellar envelopes. The survey will provide the scientific community with a set of data that can pave the way for further detailed studies at higher spectral and angular resolution.  
2018.A.00049.S ACA Observatory Project: SMC Band 3 mapping As a complement to project 2017.A.00054.S, the North bar in the SMC will also be mapped in the 3mm transitions of CS, HCN, HCO+, H(42)α, SiO, and CCH, and the continuum. The observations will probe other emission mechanisms that occur in star forming regions and in stellar ejecta, such as free-free, hydrogen recombination lines, and dense case tracers. Agliozzo et al. 2021
2018.A.00050.T Sgr A* Coordinated observations with Spitzer, Chandra, NuSTAR This project will observe the galactic center in the Band 6 or Band 7 continuum in coordination with Spitzer, Chandra, and NuStar. The ACA observations will be obtained on 3 days in July for approximately 7 hours each day. The description of the campaign is available at https://www.cfa.harvard.edu/irac/gc/.

Michail et al. 2021

Boyce et al. 2022

2018.A.00051.S Mapping Zeeman-sensitive molecules in the Orion Filament with the ACA Selected regions of the Orion filament will be mosaicked in Band 3 transitions of SO and CN as well as the continuum. The mosaic will identify regions that are bright in these transitions that will be suitable for follow-up Zeeman observations to measure the magnetic field strength in the filament.