Title Line surveys in evolved stars Pi P. Cox Time 680 hrs 1. Name: Line surveys in evolved stars Authors: P. Cox, J. Cernicharo....... 2. Science goal: At the border between stellar and interstellar physics, circumstellar envelopes (CSEs) are key objects in astrophysics. They appear at the end of the Red Giant phase, when the stars eject the bulk of their mass in less than 10(5) years. The episode of high mass loss contributes to the enrichment of the interstellar medium (ISM) in dust and heavy elements. Its timescale and yields control the chemical evolution of galaxies. During the phase of high mass loss, the cooling of the outer stellar atmosphere leads to the formation of dust grains. The grains, accelerated by radiation pressure, drag the gas outwards, building a thick, dusty circumstellar envelope. Later, at the end of the high mass loss phase, the star develops a bipolar outflow and evolves toward a planetary nebula. The gas in the envelope is essentially in the molecular form; in contact with interstellar UV radiation or with the outflowing matter, it experiences a rich chemistry. To date, over 60 different molecular species have been identified in CSEs. This wealth of molecules, allied to relatively well known physical conditions and timescales, makes of the circumstellar envelopes unvaluable probes of photo- and shock-chemistry. The CSE expansion velocities are of the order of 10 km/s, and their outer radii <10(18) cm. The most interesting regions, the acceleration region, which is also the region of dust formation, and the photochemical region lie respectively at distances of a few 10(14) cm and a few 10(16) cm from the star. The closest CSEs being 100 pc away, their detailed study asks for angular resolutions better than 0.1-0.2 arcsec. The outer envelopes of high mass loss AGB stars are cold (10< T/K < 100) and opaque up to the mid-infrared. Hence, these studies are best made with large sub-millimeter interferometers. The closest CSEs and protoplanetary nebulae (PPNs) have been studied in the emission of a number of molecules with the large millimeter single-dish telescopes and arrays. The main target of these studies is the closest C-rich CSE, IRC+10216, located between 100 pc and 200 pc from the Sun. Its spectrum has been almost completely surveyed from 1 cm to 0.8 mm; it is exceptionally rich in radicals and linear C-chain molecules (Cernicharo et al. 2000}. At the level of 10 mJy, the line density is one per 10--20 MHz, reaching line confusion limit with the IRAM 30-m telescope at a level of 5 mJy. The millimeter emission of a score of molecules and radicals has been mapped with interferometers in this CSE. The maps shows a clear chemical segregation, the stable species (particularly those with refractory elements) being observed mostly near the star, whereas the reactive species are confined to a thin shell of the outer envelope (e.g., Guelin et al. 1996). These observations have allowed to understand the basic processes controlling the chemistry in the outer envelopes (Glassgold et al. 1996). A few other C-rich or O-rich envelopes have also been studied, but far less in detail, because of their smaller sizes and of the weakness of their emission. In this proposal, we propose to make unbiased line surveys of **five** relatively nearby evolved stars in order to get an unbiased view of the chemical composition and structure of their envelopes. The stars have been selected to span a range in chemical composition (O and C-rich) and evolution (from AGB to proto-planetary nebulae). Spatially resolved data to separate the contribution from the inner and external layers of the envelopes are needed to reduce the confusion and to identify the largest possible number of new molecular species. The survey will be performed over the whole frequency range of ALMA in order to explore the different physical conditions of the envelopes. By measuring the continuum emission, it will be possible to study the thermal dust emission at high sensitivity, across the submillimeter bands, and at high angular resolution. This will be essential to study the formation of dust grains and the acceleration of the gas, which are capital since they control the mass loss process and the final stages of stellar evolution, but are still not understood . As in the case of the 'Unbiased line surveys of high mass star forming regions', the source list should be coordinated with that of HIFI so that complementary information on higher frequencies is also obtained. 3. Number of sources: 6 4. Coordinates: 4.1. Name RA Dec (J2000.0) IRC+10216 09:47:57.3 13:16:43 OH231.8+4.2 07:42:16.9 -14:42:50 Red Rectangle 06:19:58.2 -10:38:15 Vy Cma 07:22:58.3 -25:46:03 NGC6302 17 13 44.4 -37 06 11 NGC6072 16 12 58.8 -36 13 38 4.2. Moving target: no 4.3. Time critical: no 5. Spatial scales: 5.1. Angular resolution: 0.6" for Band 3, 0.3" for Bands 6, 7 and 9 5.2. Range of spatial scales/FOV: - 6"x6" for the innermost zone - 30"x30" for the external layer for IRC+10216 and OH231.8 Spatial scales scale as 1/D where D is the distance. For all other objects the spatial scales will be of the order of a few seconds for the whole envelope and smaller than 1" for the innermost zone. 5.3. Single dish: Yes, for IRC+10216 and OH231.8 5.4. ACA: Yes, for IRC+10216 and OH231.8 5.5. Subarrays: no 5.6. Configurations : Large , Intermediate and compact, together with ACA for IRC+10216 and OH231.8 Intermediate and Large for all other sources 6. Frequencies: 6.1. Receiver band: Band 3 Band 6 Band 7 Band 9 6.2. Line: 60 64 95 69 settings 6.3. Spectral resolution (km/s): 0.5 km/s for some frequencies. 3 km/s for most frequency settings 6.4. Spectral coverage (km/s or GHz): As Large as possible at all frequencies 7. Continuum flux density: Band 3 Band 6 Band 7 Band 9 7.1. Typical value: 10-50 20-80 30-100 100-1000 mJy 7.2. Continuum peak value: 50 200 300 1000 mJy/beam 7.3. Required continuum rms: 0.01 Jy 7.4. Dynamic range in image: >100 8. Line intensity: 8.1. Typical value: 5-500 K for the inner layers of AGBs (angular scales 0.05"-1" for IRC+10216) 8.2. Required rms per channel: 1 K for observations of the inner layers. Better than 0.05 K for the external layers (structures resolved with the 30m; cold gas) 8.3. Spectral dynamic range: 3 (for species which are barely detected) >100 (for brightest lines) 9. Polarization: Yes, for paramagnetic molecules formed in the zone of a few stellar radii around the star. Yes, for masers (HCN, H2O,...) 10. Integration time per setting: 10 min/Bd 3, 20 min/Bd 6 30 min/Bd 7, 9 - for 0.3 arcsec resolution and 0.2-0.3 k (1 sigma) sensitivity 11. Total integration time for program: 6 x 60 x 10m : 60 h Band 3 6 x 64 x 20m: 128 h Band 6 6 x 95 x 30m: 285 h Band 7 6 x 69 x 30m: 207 h Band 9 ------------------------------------------- 680 h total ***************************************************************************** Review Peter Schilke: Both scientifically very convincing and technically well constructed proposal. The source list could be commented on a bit further, but that's a detail. The observing time is well justified and reasonable. -------------------------------------------------- Review v2.0: 1. Name: Line surveys in evolved stars DRSP 2.0 Reviewer Leonardo Testi: Nothing to add wrt previous review. Well developed program