NIKA2 cosmological legacy survey. First measurement of the confusion noise at the IRAM 30 m telescope

Ponthieu, N.; Desert, F. -X.; Beelen, A.; Adam, R.; Ade, P.; Ajeddig, H.; Amarantidis, S.; Andre, P.; Aussel, H.; Benoit, A.; Berta, S.; Bethermin, M.; Bing, L. J.; Bongiovanni, A.; Bounmy, J.; Bourrion, O.; Calvo, M.; Catalano, A.; Cherouvrier, D.; De Petris, M.; Doyle, S.; Driessen, E. F. C.; Ejlali, G.; Ferragamo, A.; Gomez, A.; Goupy, J.; Hanser, C.; Katsioli, S.; Keruzore, F.; Kramer, C.; Ladjelate, B.; Lagache, G.; Leclercq, S.; Lestrade, J. -F.; Macias-Perez, J. F.; Madden, S. C.; Maury, A.; Mayet, F.; Monfardini, A.; Moyer-Anin, A.; Munoz-Echeverria, M.; Myserlis, I.; Neri, R.; Paliwal, A.; Perotto, L.; Pisano, G.; Reveret, V.; Rigby, A. J.; Ritacco, A.; Roussel, H.; Ruppin, F.; Sanchez-Portal, M.; Savorgnano, S.; Schuster, K.; Sievers, A.; Tucker, C.; Zylka, R.

doi:10.1051/0004-6361/202554530

The NIKA2 Cosmological Legacy Survey (N2CLS) is a large programme using the NIKA2 dual-band camera on the IRAM 30 m telescope. Its goal is to improve our understanding of the physics of distant Dusty Star Forming Galaxies (DSFGs) by carrying out deep surveys of two fields, GOODS-North and COSMOS. This work is focussed on GOODS-North, which was observed for 78.2 hours, simultaneously at 1.2 and 2 mm, with a field of view of ∼240 arcmin2. With such a deep integration, we were able to measure, for the first time, the confusion noise limits at the 30 m telescope using the best sampled ∼62 arcmin2 and masking sources with a flux greater than 0.54 or 0.17 mJy at 1.2 or 2 mm, respectively. We found a confusion noise of 139.1-19.2+15.9±11.9 μJy/beam at 1.2 mm and 38.6-13.1+9.6±3.7 μJy/beam at 2 mm (the first uncertainty is statistical, the second is the cosmic variance). In this region, this corresponds to half the instrumental noise. To derive these estimates, we devised a novel estimator, referred to as the cross variance, which also enabled us to estimate the correlated confusion noise between the two bands. Thus, we obtained a result of 49.6-24.8+15.9±6.4 μJy/beam. These values are consistent with the state of the art Simulated Infrared Dusty Extragalactic Sky (SIDES) model.

NIKA2 cosmological legacy survey. First measurement of the confusion noise at the IRAM 30 m telescope / Ponthieu, N.; Desert, F. -X.; Beelen, A.; Adam, R.; Ade, P.; Ajeddig, H.; Amarantidis, S.; Andre, P.; Aussel, H.; Benoit, A.; Berta, S.; Bethermin, M.; Bing, L. J.; Bongiovanni, A.; Bounmy, J.; Bourrion, O.; Calvo, M.; Catalano, A.; Cherouvrier, D.; De Petris, M.; Doyle, S.; Driessen, E. F. C.; Ejlali, G.; Ferragamo, A.; Gomez, A.; Goupy, J.; Hanser, C.; Katsioli, S.; Keruzore, F.; Kramer, C.; Ladjelate, B.; Lagache, G.; Leclercq, S.; Lestrade, J. -F.; Macias-Perez, J. F.; Madden, S. C.; Maury, A.; Mayet, F.; Monfardini, A.; Moyer-Anin, A.; Munoz-Echeverria, M.; Myserlis, I.; Neri, R.; Paliwal, A.; Perotto, L.; Pisano, G.; Reveret, V.; Rigby, A. J.; Ritacco, A.; Roussel, H.; Ruppin, F.; Sanchez-Portal, M.; Savorgnano, S.; Schuster, K.; Sievers, A.; Tucker, C.; Zylka, R.. - In: ASTRONOMY & ASTROPHYSICS. - ISSN 0004-6361. - 705:(2026), pp. 1-13. [10.1051/0004-6361/202554530]