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Envelope structure of deeply embedded young stellar objects in the Serpens Molecular Cloud
M R Hogerheijde1, E F van Dishoeck, J M Salverda
1Sterrewacht Leiden, The Netherlands.
The Astrophysical Journal
|September 7, 2001
Summary
Detailed observations of young stellar objects in the Serpens Molecular Cloud reveal their envelope structures. These studies show that embedded protostars (SMM 1, 3, 4) have dense envelopes and outflows, while SMM 2 lacks a central protostar.
Area of Science:
- Astronomy and Astrophysics
- Star Formation
- Interstellar Medium
Background:
- Deeply embedded young stellar objects (YSOs) are crucial for understanding star formation.
- The Serpens Molecular Cloud is a region of dense, active star formation.
- Previous studies have provided limited detail on the physical and chemical structure of YSO envelopes.
Purpose of the Study:
- To conduct detailed observations of the envelope structure of deeply embedded YSOs in the Serpens Molecular Cloud.
- To investigate the physical properties (density, mass, temperature) and chemical composition of these envelopes.
- To understand the relationship between YSOs, their envelopes, and associated molecular outflows.
Main Methods:
- Utilized aperture-synthesis and single-dish millimeter/submillimeter observations.
- Analyzed molecular-line and continuum emission from various transitions (e.g., 13CO, C18O, HCN, HCO+, SO, SiO).
- Employed Monte Carlo calculations for molecular excitation and line transfer modeling.
Main Results:
- Resolved continuum emission for SMM 1, 3, and 4, revealing density structures consistent with a radial power law (slope -2.0 +/- 0.5).
- Inferred envelope masses between 3.0 and 8.7 Msolar for SMM 1, 3, and 4 within 8000 AU.
- Detected compact molecular emission tracing dense cores and outflow cavities for SMM 1, 3, and 4; SMM 2 showed no compact emission, suggesting no central protostar.
- Identified warm material (>100 K) associated with outflows or inner envelopes, comprising <1% of total mass.
- Observed molecular abundances similar to other Class 0 YSOs, with some enhancements toward SMM 1.
Conclusions:
- The study provides a comprehensive view of the physical and chemical structure of embedded YSO envelopes in a clustered environment.
- The density structure of the envelopes is well-described by a power law, with evidence for circumstellar disks or warm inner envelopes.
- SMM 2 likely does not host a central protostar, unlike SMM 1, 3, and 4.
- CO depletion is modest, suggesting a short-lived phase of large depletions influenced by local star formation density.
- The findings offer insights into the early stages of star and planet formation.