A dataset provided by the European Space Agency

Name OT1_cjoblin_1
Title Physics of gas evaporation at PDR edges


DOI https://doi.org/10.5270/esa-519ej9v
Author European Space Agency
Description Far-ultraviolet (FUV) photons in massive OB star-forming
regions have a major impact on the structure, dynamics,
chemistry and thermal balance of their associated molecular
cloud. We propose to study the photoevaporation under
FUV irradiation of dense filaments in prototype
photodissociation regions (PDR) by mapping with the HIFI
spectrometer the [CII] 158 micron line associated with the
evaporating gas and high-J CO lines tracing the warm dense
structures. The combination of the spectral range covered
by Herschel and the very high spectral resolution of HIFI is
unique to get insight into the process of mixing of cold
molecular gas into warm atomic gas. This process governs
the evolution of dense gas submitted to FUV photons
in a wide variety of astronomical objects including
protostellar and protoplanetary disks but is best studied
in PDRs.
We ask for 9.8 hours of observations in two PDRs, NGC7023
and the Horsehead nebula. NGC7023 is illuminated by a
B2Ve star and hosts very diluted atomic gas and dense
filaments. The Horsehead nebula is a PDR viewed nearly
edge-on with a high gas density gradient at the edge
that is illuminated by a O9.5V star and is immersed in
an HII region.
In these objects, there is evidence for dynamical processes
that create a mixing layer between molecular and atomic
gas, both from gas kinematics (first results with HIFI on the
[CII] line) and chemistry. The first HIFI [CII] results clearly
call for a larger spatial coverage of the region using OTF
mapping mode with HIFI to obtain a more complete picture
of the PDR morphology and dynamics. The 12^CO(8-7)
and 13^CO(8-7) lines will be also targeted to trace
the warm interfaces of the dense filaments/edges.
The team gathers together specialists of the studied regions
and of the Herschel instruments: HIFI (this proposal), SPIRE
and PACS (comple...mentary data). The team has strong
expertise in the study of the physics and chemistry of PDRs,
both in terms of data analysis and modelling using and
developing the Meudon PDR code.
Instrument HIFI_HifiMapping_load-raster, HIFI_HifiMapping_fly
Temporal Coverage 2011-02-03T22:17:13Z/2012-04-14T09:41:29Z
Version SPG v14.1.0
Mission Description Herschel was launched on 14 May 2009! It is the fourth 'cornerstone' mission in the ESA science programme. With a 3.5 m Cassegrain telescope it is the largest space telescope ever launched. It is performing photometry and spectroscopy in approximately the 55-671 µm range, bridging the gap between earlier infrared space missions and groundbased facilities.
Creator Contact https://support.cosmos.esa.int/h®erschel/
Date Published 2012-10-14T08:09:13Z
Publisher And Registrant European Space Agency
Credit Guidelines European Space Agency, 2012, Physics Of Gas Evaporation At Pdr Edges, SPG v14.1.0, European Space Agency, https://doi.org/10.5270/esa-519ej9v