NIKA2 maps tracing dust grain evolution in cores of TMC1

¹ Institut de RadioAstronomie Millimétrique (IRAM), Grenoble, France
² Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, France
³ School of Physics and Astronomy, Cardiff University, Queen’s Buildings, The Parade, Cardiff, CF24 3AA, UK
⁴ Université Paris Cité, Université Paris-Saclay, CEA, CNRS, AIM, F-91191 Gif-sur-Yvette, France
⁵ IRAM, Avenida Divina Pastora 7, Local 20, E-18012, Granada, Spain
⁶ Aix Marseille Univ, CNRS, CNES, LAM (Laboratoire d’Astrophysique de Marseille), Marseille, France
⁷ Institut Néel, CNRS, Université Grenoble Alpes, France
⁸ Université de Strasbourg, CNRS, Observatoire astronomique, UMR 7550, 67000 Strasbourg, France
⁹ Univ. Grenoble Alpes, CNRS, LPSC-IN2P3, 53, av. des Martyrs, 38000 Grenoble, France
¹⁰ Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 5, I-00185 Roma, Italy
¹¹ Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
¹² Institute for Research in Fundamental Sciences (IPM), School of Astronomy, Tehran, Iran
¹³ Centro de Astrobiología (CSIC-INTA), Torrejón de Ardoz, 28850 Madrid, Spain
¹⁴ Aix Marseille Univ, CNRS/IN2P3, CPPM, Marseille, France
¹⁵ National Observatory of Athens, Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing, Ioannou Metaxa and Vasileos Pavlou GR-15236, Athens, Greece
¹⁶ Department of Astrophysics, Astronomy & Mechanics, Faculty of Physics, University of Athens, Panepistimiopolis, GR-15784 Zografos, Athens, Greece
¹⁷ High Energy Physics Division, Argonne National Laboratory, 9700 South Cass Av., Lemont, IL 60439, USA
¹⁸ LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Université, UPMC, 75014 Paris, France
¹⁹ Institute of Space Sciences (ICE), CSIC, Campus UAB, Carrer de Can Magrans s/n, E-08193, Barcelona, Spain
²⁰ ICREA, Pg. Lluís Companys 23, Barcelona, Spain
²¹ IRAP, CNRS, Université de Toulouse, CNES, UT3-UPS, (Toulouse), France
²² Dipartimento di Fisica, Università di Roma, Via della Ricerca Scientifica 1, I-00133 Roma, Italy
²³ School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK
²⁴ Institut d’Astrophysique de Paris, CNRS (UMR7095), 98 bis boulevard Arago, 75014 Paris, France
²⁵ University of Lyon, UCB Lyon 1, CNRS/IN2P3, IP2I, 69622 Villeurbanne, France
²⁶ Max Planck Institute for Extraterrestrial Physics, 85748 Garching, Germany

Published online: 20 February 2026

Abstract

The Taurus Molecular Cloud TMC1 is a nearby molecular cloud filament exhibiting several dense cores. It has been intensely studied in particular because of its very rich gas phase chemistry. Here, we present NIKA2 observations with the IRAM 30m telescope of its dust emission at 1 and 2mm wavelengths. Its vicinity of only 140 pc allows to study variations of its grain properties, i.e. its dust emissivity index β, on scales of only 2430 a.u. (18″). The NIKA2 maps are combined with Planck data to retrieve the emission at scales larger than the NIKA2 field-of-view. Maps of the 1mm/2mm flux ratio are then combined with a dust temperature map derived from Herschel data to create a map of the β index. Several of the observed cores exhibit a significant increase of β from ~ 1.2 in the outskirts at optical extinctions of ~ 5 mag to ~ 1.8 in the centers at ~ 18 mag. Grain models show that this steepening of the mm/submm emissivity is consistent with the gradual build-up of ice layers on the grain surfaces due to freeze-out of molecules in the cold, dense interiors of these cores.