Science Verification

Science Verification is the process by which we demonstrate that the data produced by ALMA are valid. The primary means of doing this is by observing sources that have already been observed by other telescopes and then comparing our results directly with those existing data sets. This will be a continuing process as we test the validity of different aspects of the observations on different types of objects. The reduced and calibrated datasets will be available to the community for download from this site as the projects are successfully completed and analyzed. The list of Science Verification sources that we hope to observe over the next several months using the initial set of capabilities that have already been commissioned, namely single-field imaging and mosaics, is shown below, but we may not be able to observe the full list. During this period, commissioning of additional capabilities will continue, so later observations will include observing modes such as polarization, solar observing, and the addition of the short baseline and zero-spacing information from the Atacama Compact Array. During commissioning, we will also be testing our ability to observe transient sources and objects requiring an external ephemeris file, so we do appreciate continuing suggestions for targets appropriate for these tests.

Since the focus in the Science Verification program is on the comparison with existing data sets, the ALMA observations will be designed to have comparable properties - e.g. covering the same spectral lines and/or using similar angular resolution - to those sets. The results will be made public, with no waiting period, as soon as satisfactory observations and data reduction have been achieved. Investigators are welcome to submit ALMA Early Science proposals for sources that are being observed as part of the Science Verification program. Clearly all proposals will need to demonstrate that they will provide new information, and in the case that the target is included in the Science Verification program this could be done by, for example, exploiting the sensitivity and/or resolution of the ALMA Cycle 0 array or by using new frequencies, spectral configurations, etc.

Currently Available Science Verification Data:

We now have several datasets available to demonstrate the early capabilities of ALMA. These projects, in many cases, were observed before 16 antennas were available and while many of the subsystems were still being tested, so they should not be construed to represent the quality of the data that can be expected during the Early Science cycles. They are provided here as a means for the user to become acquainted with the ALMA data structure, observing strategies and reduction techniques. Given that the data have been taken during the construction phase, there may be more idiosyncrasies present than will be expected during full operations, so we ask the user to please review carefully the CASA guides provided with the datasets that represent unique observing modes or strategies, as indicated below.

1. TW Hya: Band 7, high spectral resolution. Many thanks to the following people for suggesting this source for ALMA Science Verification: Meredith Hughes, Stuartt Corder, Chunhua Qi, Karin Oberg, Michiel Hogerheide, Andrea Isella, Dmitry Semenov.

Additional data on TW Hya is available (without a separate CASA guide) here: Band 3, Band 6.

2. NGC3256: Band 3, low spectral resolution. Many thanks to the following people for suggesting this source for ALMA Science Verification: Kazushi Sakamoto, Alison Peck, Satoki Matsushita, Martin Zwaan.

3. Antennae galaxies: Band 7, high spectral resolution. Many thanks to the following people for suggesting this source for ALMA Science Verification: Christine Wilson, Junko Ueda, Francois Boulanger, Nicole Nesvadba, Cinthya Herrera.

Additional data on Antennae is available (without a separate CASA guide) here: Band 6

4. M100 Band 3, low spectral resolution. Many thanks to the following people for suggesting this source for ALMA Science Verification: Preben Grosbol and Caterine Vlahakis.

5. SgrA* Band 6, recombination lines. Many thanks to the following people for suggesting this source for ALMA Science Verification: Sergio Martin, Stephane Leon, Farhad Zadeh, Andreas Eckart.

6. BR1202-0725 Band 7: low spectral resolution. Many thanks to the following people for suggesting this source for ALMA Science Verification: Daisuke Iono, Satoki Matsushita, Shinya Komugi, Jeff Wagg, Tommy Wiklind, Dominik Reichers

Update: A second dataset on this source, taken shortly after the first, has been added to the above directory.  This data was taken under very good conditions and at higher elevation, so has better sensitivity than the first but, due to a fault lacks the system temperature information which is required to perform a standard flux calibration.

7. IRAS16293 Band 6: high spectral resolution. Many thanks to the following people for suggesting this source for ALMA Science Verification: Jes Jorgensen, Suzanne Bisschop, Ewine van Dishoeck, Tyler Bourke, Johan Lindberg, Michiel Hogerheijde, Bill Dent, Martin Zwaan, Al Wootten

Update: The raw dataset with the full spectral resolution has been added to the above directory.  Be aware that this is a large file so downloading it and reducing it will take patience.

8. Centaurus A Band 6: high spectral resolution mosaic. Many thanks to the following people for suggesting this source for ALMA Science Verification: Juergen Ott, Christian Struve, Tommy Wiklind, Sergio Martin

9. Orion KL Band 6: high resolution spectral survey. Many thanks to the following people for suggesting this source for ALMA Science Verification: Tom Wilson, Melvyn Wright, Ciriaco Goddi, Tom Wilson

Commissioning Test data

1. Proof of Concept of Response to Targets of Opportunity: GRB 110715A followup Band 7: continuum. Many thanks to the following people for participating in the Rapid Response testing: Dale Frail, Ashley Zauderer, Andreas Lundgren, Itziar de Gregorio, Mark Rawlings, Diego Garcia, Stuartt Corder

Using the data for publication

The following statement should be included in the acknowledgment of papers using the datasets listed above:

“This paper makes use of the following ALMA data: ADS/JAO.ALMA#<Project code>.  ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada) and NSC and ASIAA (Taiwan), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ."

For Science Verification data, the codes have the following form: ADS/JAO.ALMA#2011.0.0000X.SV, where X=1 for the TW Hya dataset, X=2 for the NGC3256 dataset,  X=3 for the Antennae mosaic, etc.

Status of ALMA Cycle 0 Science Verification Projects:

The observations will be made in single-field interferometry or small mosaic modes, generally using dual polarization with 4 basebands of 1.875 GHz each with either high spectral resolution (FDM - ~1 MHz) or low spectral resolution (TDM - ~30 MHz).  For some objects a higher resolution mode will be used to match that of the comparison data.