Herschel/HIFI detections of hydrides towards AFGL 2591. Envelope emission versus tenuous cloud absorption
Research output: Contribution to journal › Journal article › Research › peer-review
The Heterodyne Instrument for the Far Infrared (HIFI) onboard the
Herschel Space Observatory allows the first observations of light
diatomic molecules at high spectral resolution and in multiple
transitions. Here, we report deep integrations using HIFI in different
lines of hydrides towards the high-mass star forming region AFGL 2591.
Detected are CH, CH+, NH, OH+,
H2O+, while NH+ and SH+ have
not been detected. All molecules except for CH and CH+ are
seen in absorption with low excitation temperatures and at velocities
different from the systemic velocity of the protostellar envelope.
Surprisingly, the CH(JF,P = 3/22,- -
1/21,+ ) and CH+(J = 1-0, J = 2-1) lines are
detected in emission at the systemic velocity. We can assign the
absorption features to a foreground cloud and an outflow lobe, while the
CH and CH+ emission stems from the envelope. The observed
abundance and excitation of CH and CH+ can be explained in
the scenario of FUV irradiated outflow walls, where a cavity etched out
by the outflow allows protostellar FUV photons to irradiate and heat the
envelope at larger distances driving the chemical reactions that produce
these molecules.
Herschel is an ESA space observatory with science instruments provided
by European-led Principal Investigator consortia and with important
participation from NASA.Apppendices and Table 1 (pages 6 to 7) are only
available in electronic form at http://www.aanda.org
Original language | English |
---|---|
Journal | Astronomy & Astrophysics |
Volume | 521 |
Pages (from-to) | L44 |
Number of pages | 7 |
ISSN | 0004-6361 |
DOIs | |
Publication status | Published - 1 Oct 2010 |
ID: 35114151