| Name | OT1_mhogerhe_1 |
| Title | Deep HIFI searches for cold water vapor in protoplanetary disks |
| URL | http://archives.esac.esa.int/hsa/whsa-tap-server/data?retrieval_type=OBSERVATION&observation_id=1342235094&instrument_name=HIFI&product_level=LEVEL0&compress=true |
| DOI | https://doi.org/10.5270/esa-vsw96sn |
| Author | hogerheijde, m. |
| Description | Water vapor inside planet-forming disks is expected to show large variations. In the warm (~200 K) inner few AU of the disk all oxygen is locked up in water vapor. In the colder outer region water quickly freezes out onto dust grains. However, efficient photodesorption by stellar ultraviolet radiation will return an appreciable fraction back into the gas phase in the upper disk layers. This coupled water ice/vapor system explains the Spitzer observations of warm water in several disks, and predicts the presence of cold water vapor in the outer disk. Through the `Water in Star Forming Regions (WISH) Key Program, we have recently clearly detected the groundstate line of cold water vapor to TW Hya and very tentatively detected it to DM Tau. Both lines are factors 10-50 weaker than expected. We hypothesize that up to 99% of icy grains have settled to the disks midplane thus `freeze drying the upper disk layers. The WISH data do not go deep enough to probe cold water vapor content now that we know that the outer disk is freeze-dried. The only clear detection is TW Hya, which has a distance of only 51 pc. At more typical distances of 100-140 pc, line strengths are lower by factors 5-8, beyond the sensitivity of WISH. We propose much deeper HIFI observations of the H2O 110-101 line at 557 GHz of four targets: DM Tau (to confirm or reject WISHs `very tentative detection), and HD100546, HD163296, and AA Tau. These disks are, after TW Hya, the closest and largest disks that offer the best chances of detection. Because of the sensitivity of H2O 110-101 to cold water vapor in the outer disk, our observations probe as-of-yet unexplored grain settling in the outer disk and enrichment of the midplane with icy grains. This can boost planet formation, since icy grains coagulate more easily. Our proposal also contains a small request for velocity-resolved CO 10-9 observations with HIFI to study warm (~200 K) gas in these four disks, and investigate if preferential settling of icy grains also affects CO. |
| Publication | |
| Instrument | HIFI_HifiPoint_dbs |
| Temporal Coverage | 2011-12-23T15:57:04Z/2012-09-06T16:35:47Z |
| 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 | 2013-03-06T11:15:02Z |
| Keywords | Herschel, HSC, submillimetre, far-infrared, HIFI, PACS, SPIRE |
| Publisher And Registrant | European Space Agency |
| Credit Guidelines | European Space Agency, hogerheijde et al., 2013, 'Deep HIFI searches for cold water vapor in protoplanetary disks', SPG v14.1.0, European Space Agency, https://doi.org/10.5270/esa-vsw96sn |