Tracing the cold and warm physico-chemical structure of deeply embedded protostars: IRAS 16293−2422 versus VLA 1623−2417 N.
Artikel i vetenskaplig tidskrift, 2018

Context. Much attention has been placed on the dust distribution in protostellar envelopes, but there are still many unanswered questions regarding the physico-chemical structure of the gas. Aims. Our aim is to start identifying the factors that determine the chemical structure of protostellar regions, by studying and com- paring low-mass embedded systems in key molecular tracers. Methods. The cold and warm chemical structures of two embedded Class 0 systems, IRAS 16293−2422 and VLA 1623−2417 were characterized through interferometric observations. DCO+, N2H+, and N2D+ were used to trace the spatial distribution and physics of the cold regions of the envelope, while c−C3H2 and C2H from models of the chemistry are expected to trace the warm (UV-irradiated) regions. Results. The two sources show a number of striking similarities and differences. DCO+ consistently traces the cold material at the disk-envelope interface, where gas and dust temperatures are lowered due to disk shadowing. N2H+ and N2D+, also tracing cold gas, show low abundances toward VLA 1623−2417, but for IRAS 16293−2422, the distribution of N2D+ is consistent with the same chemical models that reproduce DCO+. The two systems show different spatial distributions c−C3H2 and C2H. For IRAS 16293−2422, c−C3H2 traces the outflow cavity wall, while C2H is found in the envelope material but not the outflow cavity wall. In contrast, toward VLA 1623−2417 both molecules trace the outflow cavity wall. Finally, hot core molecules are abundantly observed toward IRAS 16293−2422 but not toward VLA 1623−2417. Conclusions. We identify temperature as one of the key factors in determining the chemical structure of protostars as seen in gaseous molecules. More luminous protostars, such as IRAS 16293−2422, will have chemical complexity out to larger distances than colder protostars, such as VLA 1623−2417. Additionally, disks in the embedded phase have a crucial role in controlling both the gas and dust temperature of the envelope, and consequently the chemical structure.
Key

interferometric

iras 16293-2422 and vla1623-2417

observational - techniques

formation - stars

methods

astrochemistry - stars

low-mass - ism

individual objects

Författare

N. M. Murillo

Universiteit Leiden

E. F. van Dishoeck

M. H. D. van der Wiel

J. K. Jorgensen

M. N. Drozdovskaya

Hannah Calcutt

Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik, Galaktisk astrofysik

D. Harsono

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Protostellar Interferometric Line Survey (PILS)

Europeiska forskningsrådet (ERC), 2019-10-30 -- .

Ämneskategorier

Astronomi, astrofysik och kosmologi

Fundament

Grundläggande vetenskaper

Mer information

Skapat

2019-10-30