| Name | OT1_hdinerst_1 |
| Title | How Cool Are Planetary Nebulae? |
| URL | http://archives.esac.esa.int/hsa/whsa-tap-server/data?retrieval_type=OBSERVATION&observation_id=1342220755&instrument_name=PACS&product_level=LEVEL0&compress=true |
| DOI | https://doi.org/10.5270/esa-es6krlz |
| Author | dinerstein, h. |
| Description | We propose to observe the O III 52 and 88 micron fine-structure lines with PACS in planetary nebulae, in order to investigate whether they contain a cold and possibly metal-rich component in addition to the ordinary hot (10,000 K) material. The presence of cold gas has been proposed in order to account for the excessive strengths of optical emission lines from recombining O++ ions, and low temperatures (500 - 5000 K) indicated by some diagnostics. If planetary nebulae truly have such inhomogeneous physical conditions and abundances, this calls into question our fundamental understanding of the composition of the nebular gas, a major source of recycled material to the ISM. The FIR O III lines offer a unique opportunity to address this issue because, due to their low excitation energies, they are emitted from both cold and hot gas, while the optical O III lines arise only from hot gas. The bright 52 and 88 micron lines were easily observed in some of our sample using less sensitive, large-beam instruments such as the Kuiper Airborne Observatory (by this P.I.) and ISO-LWS. For several targets the previous observations indicate O/H values greater than solar, supporting the idea that metal-rich gas is present, but the higher angular resolution of PACS is needed in order to discern whether the metal-rich material is concentrated towards the central regions, as claimed by optical studies. For several objects we propose to also measure the 88.8 micron 1312 H I line, which will not only provide a measurement of H+, but also a probe of temperature by comparing its strength to that of shorter-wavelength H I lines. The latter will be taken from Spitzer-IRS maps (for a few targets), and optical integrated-field unit spectral maps either already obtained, or to be obtained, at McDonald Observatory. These observations may enable us to prove or disprove the presence of cold O-rich material in planetary nebulae. |
| Publication |
|
| Instrument | PACS_PacsRangeSpec_point, PACS_PacsLineSpec_point |
| Temporal Coverage | 2011-05-12T22:36:23Z/2012-09-12T08:45:36Z |
| Version | SPG v14.2.0 |
| 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 | 2013-03-12T06:06:57Z |
| Keywords | Herschel, HSC, submillimetre, far-infrared, HIFI, PACS, SPIRE |
| Publisher And Registrant | European Space Agency |
| Credit Guidelines | European Space Agency, dinerstein et al., 2013, 'How Cool Are Planetary Nebulae?', SPG v14.2.0, European Space Agency, https://doi.org/10.5270/esa-es6krlz |