Tracing the cold and warm physico-chemical structure of deeply embedded protostars: IRAS 16293−2422 versus VLA 1623−2417 N.
Journal article, 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.

astrochemistry - stars

low-mass - ism

individual objects

iras 16293-2422 and vla1623-2417



observational - techniques

formation - stars


N. M. Murillo

Leiden University

E. F. van Dishoeck

Max Planck Institute for Extraterrestrial Physics

Leiden University

M. H. D. van der Wiel

Netherlands Institute for Radio Astronomy (ASTRON)

University of Copenhagen

J. K. Jorgensen

University of Copenhagen

M. N. Drozdovskaya

University of Copenhagen

Leiden University

Hannah Calcutt

University of Copenhagen

D. Harsono

Leiden University

Astronomy and Astrophysics

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

Vol. 617 A120

Protostellar Interferometric Line Survey (PILS)

European Research Council (ERC), 2019-10-30 -- .

Subject Categories

Astronomy, Astrophysics and Cosmology


Basic sciences



More information

Latest update