SWIMS, simultaneous-color wide-field infrared multi-object spectrograph, was installed on the Subaru Telescope of the National Astronomical Observatory of Japan (NAOJ) at Hawaii for performance verification and succeeded in the first light observation.

After its fabrication, assemblies, evaluations, and adjustments in Japan from 2009, SWIMS has been transported to the NAOJ Hawaii Observatory in July 2017. SWIMS is one of the instruments developed for the TAO 6.5 m telescope. While the site of TAO at the altitude of 5,640 m is ideal for astronomical observations, it is a severe environment for humans to work with instruments at the site, especially for the first installation and testing on the telescope. Also, by evaluating the observing performance of the instrument at the other observatory prior to the completion of TAO, we will be promptly able to perform scientific observations on the TAO telescope. So we have applied for engineering observations of the instrument on the Subaru Telescope of the NAOJ Hawaii Observatory in 2015, and our observation proposal has been accepted after reviews over two years. And on May 30th this year, which marks the 10th years milestone, SWIMS has successfully seen its "first light", i.e., has received astronomical light on detectors for the first time.

SWIMS, installed on the Subaru telescope

Star-forming region Sharpless 2-106 (S106) taken with SWIMS (false-color image in J, H, and Ks band; exposure time is 50 seconds)

Engineering observations have been carried out for 4 days from May 29th to June 1st. Although the sky condition was unfortunately not good and clouds were occasionally flowing through the observing area of the sky, we have observed various astronomical objects from stars and star clusters in the Milky Way to distant galaxies, and have evaluated the hardware / software of SWIMS to work as designed and to promptly output astronomical data.

By means of the simultaneous two-color observation which is one of the major features of SWIMS, we have efficiently acquired data with various filters, and most of the engineering items were successfully evaluated. With those dataset, we will be also able to demonstrate the design concept of the instrument that "Even under unstable weather, the simultaneous two-color observation will deliver us multi-wavelength data evenly affected by the variation of the sky, and thus, will improve the accuracy of data analyses and the reliability in resulting scientific outputs".

The evaluation in the observations has been mainly focused on the imaging function. We will be performing further engineering observations in the next January to evaluate the multi-object spectroscopic function which is another feature of SWIMS. We would like to continue the evaluation of the instrument on the Subaru telescope and make it to be fully ready for scientific observations at TAO.