FAUST I. The hot corino at the heart of the prototypical Class I protostar L1551 IRS5

Abstract

The study of hot corinos in Solar-like protostars has been so far mostly limited to the Class 0 phase, hampering our understanding of their origin and evolution. In addition, recent evidence suggests that planet formation starts already during Class I phase, which, therefore, represents a crucial step in the future planetary system chemical composition. Hence, the study of hot corinos in Class I protostars has become of paramount importance. Here we report the discovery of a hot corino towards the prototypical Class I protostar L1551 IRS5, obtained within the ALMA Large Program FAUST. We detected several lines from methanol and its isopotologues (13CH3OH and CH2DOH), methyl formate and ethanol. Lines are bright toward the north component of the IRS5 binary system, and a possible second hot corino may be associated with the south component. The methanol lines non-LTE analysis constrains the gas temperature (∼100 K), density (≥1.5 × 108 cm−3), and emitting size (∼10 au in radius). All CH3OH and 13CH3OH lines are optically thick, preventing a reliable measure of the deuteration. The methyl formate and ethanol relative abundances are compatible with those measured in Class 0 hot corinos. Thus, based on the present work, little chemical evolution from Class 0 to I hot corinos occurs.

ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP): A Hot Corino Survey toward Protostellar Cores in the Orion Cloud

“…We report toward our ALMASOP sample the detection of 11 hot corinos, among which 10 were classified as Class 0 and one was classified as Class I by Dutta et al (2020) based on their bolometric temperatures. G208E, the only Class I hot corino, appears special, as there have been so far only a very limited number of Class I hot corinos reported, namely SVS 13A (Bianchi et al 2019), Ser-emb 17 (Bergner et al 2019), L1551 IRS5 (Bianchi et al 2020), and Ser-emb 11 W likely in Class 0/I transition (Martín-Doménech et al 2021). We note, however, that the classification of G208E may not be secure.…”

“…It appears much closer, though still less than the local ISM value, implying possibly an underestimate of the 13 CH 3 OH column density. Bianchi et al (2020) has reported high opacity in a 13 C substituted methanol transition ( 13 CH 3 OH) at E up =48 K toward the Class I hot corino L1551 IRS5. We consider that the column densities of 13 CH 3 OH derived in this study are not severely affected by the opacity because, first, the [ 13 CH 3 OH] in this study are derived from transitions including those at high upper energies (i.e., E up =162 and 254 K), which are less affected by the opacity, and second, the ratio between the column densities of 13 CH 3 OH and CH 2 DOH appears to be similar among the hot corino sources in this study and in the literature (Figure 7).…”

Chemical and Physical Characterization of the Isolated Protostellar Source CB68: FAUST IV

“…We are conducting the Atacama Large Millimeter/submillimeter Array (ALMA) large program FAUST (Fifty AU Study of the Chemistry in the Disk/Envelope System of Solar-like Protostars), exploring the physical and chemical structures on a 50 au scale toward 13 nearby young protostellar sources with the same brightness sensitivity (Bianchi et al 2020;Codella et al 2021;Okoda et al 2021a;Ohashi et al 2022). By observing more than 40 molecular species, FAUST systematically compares the physical and chemical structures of various types of sources.…”

FAUST VI. VLA 1623--2417 B: a new laboratory for astrochemistry around protostars on 50 au scale

“…In other words, out of the coeval A1+A2 binary, only A1 appears to be associated with a hot-corino. This chemical differentiation has been indeed found in the (sub-)mm spectral window for several binaries across different star-forming regions (Taquet et al 2015;De Simone et al 2017;Bianchi et al 2020;Belloche et al 2020;Yang et al 2021;Bouvier et al 2022, and references therein). Is this a real chemical differentiation, possibly related to colder conditions, or is it a signature of dust opacity playing a major role at (sub-)mm wavelengths?…”

“…This value is within the range found in the literature for hot-corinos associated with Class 0 or I objects, as imaged by interferometers. If we consider the ALMA-PILS, IRAM-CALYPSO, ALMA-FAUST, and ALMA-PEACHES, a relatively large spread is revealed, from a few 10 −2 to values close to unity (Jørgensen et al 2016(Jørgensen et al , 2018Manigand et al 2020;Bianchi et al 2020;Belloche et al 2020;Yang et al 2021).…”