GASPS -a Herschel survey of gas and dust in protoplanetary disks: summary and initial statistics

Dent, W. R. F. and Thi, W. F. and Kamp, I. and Williams, J. P. and Menard, F. and Andrews, I. and Ardila, D. and Aresu, G. and Augereau, J. C. and Barrado Y Navascues, D. and Brittain, S. and Carmona, A. and Ciardi, D. and Danchi, W. and Donaldson, J. and Duchene, G. and Eiroa, C. and Fedele, D. and Grady, C. and De Gregorio-Molsalvo, I. and Howard, C. and Huelamo, N. and Krivov, A. and Lebreton, J. and Liseau, R. and Martin-Zaidi, C. and Mathews, G. and Meeus, G. and Mendigutia, I. and Montesinos, B. and Morales-Calderon, M. and Mora, A. and Nomura, H. and Pantin, E. and Pascucci, I. and Phillips, N. and Pinte, C. and Podio, L. and Ramsay, S. K. and Riaz, B. and Riviere-Marichalar, P. and Roberge, A. and Sandell, G. and Solano, E. and Tilling, I. and Torrelles, J. M. and Vandenbusche, B. and Vicente, S. and White, G. J. and Woitke, P. (2013) GASPS -a Herschel survey of gas and dust in protoplanetary disks: summary and initial statistics. Publications of the Astronomical Society of the Pacific, 125 (927). pp. 477-505. ISSN 0004-6280

Abstract

We describe a large-scale far-infrared line and continuum survey of protoplanetary disk through to young debris disk systems carried out using the ACS instrument on the Herschel Space Observatory. This Open Time Key program, known as GASPS (Gas Survey of Protoplanetary Systems), targeted ~250 young stars in narrow wavelength regions covering the [OI] fine structure line at 63 μm the brightest far-infrared line in such objects. A subset of the brightest targets were also surveyed in [OI]145 μm, [CII] at 157 μm, as well as several transitions of H2O and high-excitation CO lines at selected wavelengths between 78 and 180 μm. Additionally, GASPS included continuum photometry at 70, 100 and 160 μm, around the peak of the dust emission. The targets were SED Class II- III T Tauri stars and debris disks from seven nearby young associations, along with a comparable sample of isolated Herbig AeBe stars. The aim was to study the global gas and dust content in a wide sample of circumstellar disks, combining the results with models in a systematic way. In this overview paper we review the scientific aims, target selection and observing strategy of the program. We summarise some of the initial results, showing line identifications, listing the detections, and giving a first statistical study of line detectability. The [OI] line at 63 μm was the brightest line seen in almost all objects, by a factor of ~10. Overall [OI]63 μm detection rates were 49%, with 100% of HAeBe stars and 43% of T Tauri stars detected. A comparison with published disk dust masses (derived mainly from sub-mm continuum, assuming standard values of the mm mass opacity) shows a dust mass threshold for [OI] 63 μm detection of ~105 Mȯ. Normalising to a distance of 140 pc, 84% of objects with dust masses ≥105 Mȯ can be detected in this line in the present survey; 32% of those of mass 106-105 Mȯ, and only a very small number of unusual objects with lower masses can be detected. This is consistent with models with a moderate UV excess and disk flaring. For a given disk mass, [OI] detectability is lower forM stars compared with earlier spectral types. Both the continuum and line emission was, in most systems, spatially and spectrally unresolved and centred on the star, suggesting that emission in most cases was from the disk. Approximately 10 objects showed resolved emission, most likely from outflows. In the GASPS sample, [OI] detection rates in T Tauri associations in the 0.3-4 Myr age range were ~50%. For each association in the 5-20 Myr age range, ~2 stars remain detectable in [OI]63 μm, and no systems were detected in associations with age >20 Myr. Comparing with the total number of young stars in each association, and assuming a ISM-like gas/dust ratio, this indicates that ~18% of stars retain a gas-rich disk of total mass ~1 MJupiter for 1-4 Myr, 1-7% keep such disks for 5-10 Myr, but none are detected beyond 10-20 Myr. The brightest [OI] objects from GASPS were also observed in [OI]145 μm, [CII]157 μm and CO J 1/4 18 17, with detection rates of 20-40%. Detection of the [CII] line was not correlated with disk mass, suggesting it arises more commonly from a compact remnant envelope.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Files associated with this item cannot be displayed due to copyright restrictions.
Faculty / Department / School: No Faculty
Date Deposited: 21 Jun 2017 23:01
Last Modified: 27 Jun 2017 00:59
Uncontrolled Keywords: Herschel Space Observatory; disk systems; dust
Fields of Research : 02 Physical Sciences > 0201 Astronomical and Space Sciences > 020102 Astronomical and Space Instrumentation
Socio-Economic Objective: E Expanding Knowledge > 97 Expanding Knowledge > 970102 Expanding Knowledge in the Physical Sciences
Identification Number or DOI: 10.1086/670826
URI: http://eprints.usq.edu.au/id/eprint/32130

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