Observing the millimeter sky with the NIKA2 camera – NIKA2Sky

The NIKA2Sky project is dedicated to the scientific exploitation of the NIKA2 camera, from the commissioning of the instrument to the first observations and results of our three large programs (LP) of the NIKA2 guaranteed time.
The first LP aims at the high-resolution observation of clusters of galaxies at large redshifts via the Sunyaev-Zel'dovich effect. The main objective is a thorough study of a sample of 50 clusters to improve cosmology with clusters. In the second LP, our objective is to map the formation of stars in dusty galaxies of the Universe at high redshift. By observing two cosmological reference fields with NIKA2, our final objectives are to obtain a complete census of the history of star formation in galaxies and to increase our knowledge of what fuels the star formation processes in the early Universe. The third LP focuses on NIKA2 polarization capabilities to map magnetic fields in star-forming regions. The scientific objective is to use NIKA2 observations of the 1.2 mm polarized dust continuum emission to characterize the role played by magnetic fields in regulating the fragmentation/evolution of dense filaments and in channelling filamentary material into prestellar and protostellar cores.

The results obtained in the NIKA2Sky project are of two kinds. First of all, the NIKA2 camera was commissioned using the IRAM 30m telescope. This topic is of general interest to the scientific community because the results are used by open time users as well as by members of the NIKA2 collaboration. Secondly, these are the first results of the three large programs (LP) run by French laboratories. Observations of the millimetre sky with NIKA2 has produced results relevant to a wide variety of topics, from cosmology to local stellar formation.

The NIKA2 project continues beyond NIKA2Sky because the camera is a resident instrument at IRAM 30-m telescope for the next decade. The guaranteed time of the collaboration also continues with future observations and many results to be published.

The NIKA2Sky project has resulted in the publication of 14 articles in peer-reviewed journals, several of which have had a significant impact on the international scientific community. It also made it possible to organize an international conference in Grenoble that brought together world specialists in millimetre astronomy and whose congress proceedings are currently being drafted.

The observation of the sky at millimetre and submillimetre wavelengths in the past years contributed to tremendous improvements in our understanding of a great variety of scientific topics ranging from the star formation in the Milky Way to the measurement of cosmological parameters. Following the recent results obtained by the Planck and Herschel satellites, the advent of a millimetre camera, capable of surveying large areas of the sky at a high-angular resolution, with a high sensitivity and a large field of view, will continue to reveal the details of the formation and evolution of structures throughout the Universe.

The NIKA2 camera is a next-generation instrument for millimetre astronomy. It is operated at 100 mK and will be installed in June 2015 on the 30-m telescope of IRAM (Institut de RadioAstronomie Millimétrique). NIKA2 will observe the sky at 150 and 260 GHz with a wide field of view (6.5 arcmin) at high-angular resolution (nominally 18 and 12 arcsec, respectively), and state-of-art sensitivity (requirement 20 and 30 mJy.s1/2, respectively). It will also have polarization capabilities at 260 GHz. With its high mapping speed (5000 detectors in total) and dual band observation, NIKA2 will revolutionize our view of the cold Universe. No other instrument exists or is even planned for the coming years to compete with NIKA2 in terms of sensitivity, angular resolution, polarization capabilities and available time of observation in the world.
The NIKA2 consortium is an international collaboration gathering 14 laboratories from France UK and Italy that has successfully answered in 2011 a call for tender issued by the IRAM concerning the next generation large field continuum instrumentation at the 30-m telescope.

The first phase (2011-2015) of the project has been partially funded by the ANR. It addresses the design, building and testing of the NIKA2 camera. This phase is completed and the camera is taking the first laboratory images in the two bands, including the polarization channel. The NIKA2 schedule for the installation in June 2015 at the 30-m telescope has been approved by IRAM. During this first phase, a prototype camera (NIKA1, dual-band with a total of ~300 KIDs) has also been built and installed at the IRAM 30-m telescope. As a test bench for the final NIKA2 instrument, the NIKA1 camera has been optimized during the two observation campaigns on November 2012 and June 2013. Current NIKA1 performance fulfills already the NIKA2 requirements in terms of sensitivity.

The second phase (2016-2020) regards the scientific exploitation of this future world-leading instrument. Indeed, 1300 hours have been allocated to the NIKA2 consortium, i.e. the largest amount of guaranteed time ever given by IRAM to a single collaboration. Our NIKA2Sky project is centered on the three large programs led by French institutes, that have each been granted 300 hours of observation (900 hr in total). The scientific program is dedicated to the study of the inner structure of galaxy clusters via Sunyaev Zel’dovich effect, and of star formation at low and high redshift, both by studying the role of magnetic fields on sub-parsec scales (down to a resolution of ~ 2000 AU) in our Galaxy, and mapping the dusty star forming galaxies up to redshifts 6.

We request a financial support to hire 4 post-docs and organize collaboration meetings as well as a workshop to ensure a high visibility of the results obtained with NIKA2. This support would capitalize on our instrumental efforts, funded by the ANR, which led to the building of a unique and world-leading instrument in millimetre astronomy.