Dust, ice, and gas evolve as they move from envelopes of forming stars into circumstellar disks where they can become the main building blocks of planets. Herschel-PACS is uniquely suited to trace this evolution through broadband emission from dust, through specific features of solids which reveal elemental composition and water content, and through spectral bands of the main icy components. Both atomic and molecular lines, in particular the [O I], H2O and OH lines, will be used to follow the gas, study the interchange between gas and ice, and trace the oxygen budget. The gas and dust spectral features are at the same time excellent probes of macroscopic parameters, such as temperature, UV and X-ray fields, density and thermal structures of envelopes and disks, and dynamical mixing processes. Our sample covers sources with a range in evolutionary state from embedded objects with massive envelopes to weak-line T Tauri stars with dissipating disks, and with a range in luminosity, spectral type, and dust characteristics. Both our high S/N PACS full spectral range scans (complemented by Spitzer mid-IR spectral scans) and our targeted, deep gas-phase line measurements will have lasting archival value.
Publication
Herschel Key Program, Dust, Ice, and Gas In Time (DIGIT): The Origin of Molecular and Atomic Emission in Low-mass Protostars in Taurus . Lee Jeong-Eun et al. . The Astrophysical Journal Supplement, Volume 214, Issue 2, article id. 21, 17 pp. (2014). . 214 . 10.1088\/0067-0049\/214\/2\/21 . 2014ApJS..214...21L , The Evolution of Far-infrared CO Emission from Protostars . Manoj P. et al. . The Astrophysical Journal, Volume 831, Issue 1, article id. 69, 11 pp. (2016). . 831 . 10.3847\/0004-637X\/831\/1\/69 . 2016ApJ...831...69M , Herschel-PACS observations of far-IR lines in young stellar objects. I. [OI] and H2O at 63 μm . Riviere-Marichalar P. et al. . Astronomy & Astrophysics, Volume 594, id.A59, 25 pp. . 594 . 10.1051\/0004-6361\/201527829 . 2016A&A...594A..59R , Embedded Protostars in the Dust, Ice, and Gas In Time (DIGIT) Herschel Key Program: Continuum SEDs, and an Inventory of Characteristic Far-infrared Lines from PACS Spectroscopy . Green Joel D. et al. . The Astrophysical Journal, Volume 770, Issue 2, article id. 123, 45 pp. (2013). . 770 . 10.1088\/0004-637X\/770\/2\/123 . 2013ApJ...770..123G , The Herschel-PACS Legacy of Low-mass Protostars: The Properties of Warm and Hot Gas Components and Their Origin in Far-UV Illuminated Shocks . Karska Agata et al. . The Astrophysical Journal Supplement Series, Volume 235, Issue 2, article id. 30, 45 pp. (2018). . 235 . 10.3847\/1538-4365\/aaaec5 . 2018ApJS..235...30K , The CDF Archive: Herschel PACS and SPIRE Spectroscopic Data Pipeline and Products for Protostars and Young Stellar Objects . Green Joe...l D. et al. . The Astronomical Journal, Volume 151, Issue 3, article id. 75, 23 pp. (2016). . 151 . 10.3847\/0004-6256\/151\/3\/75 . 2016AJ....151...75G , The Warm CO Gas along the UV-heated Outflow Cavity Walls: A Possible Interpretation for the Herschel/PACS CO Spectra of Embedded YSOs . Lee Seokho et al. . The Astrophysical Journal Supplement Series, Volume 217, Issue 2, article id. 30, 16 pp. (2015). . 217 . 10.1088\/0067-0049\/217\/2\/30 . 2015ApJS..217...30L ,
Herschel was launched on 14 May 2009! It is the fourth 'cornerstone' mission in the ESA science programme. With a 3.5 m Cassegrain telescope it is the largest space telescope ever launched. It is performing photometry and spectroscopy in approximately the 55-671 µm range, bridging the gap between earlier infrared space missions and groundbased facilities.
European Space Agency, 2012, Dust Comma Ice Comma And Gas In Time Openpardigitclosepar, SPG v14.2.0, European Space Agency, https://doi.org/10.5270/esa-5orcpzo
