Artículo de revista
CO(6−5) and [C i](2−1) pointed observations of five protoplanetary disks: Warm gas in HD 142527
Fecha
2013-05Registro en:
A&A 553, A64 (2013)
DOI: 10.1051/0004-6361/201219644
Autor
Casassus Montero, Simón
Hales, A.
De Gregorio Monsalvo, Itziar
Dent, B.
Belloche, A.
Güsten, R.
Ménard, Francois
Hughes, A.M.
Wilner, D.
Salinas, V.
Institución
Resumen
Context. The molecular gas in protoplanetary disks can be traced with single-dish instruments in low J rotational lines of CO, in systems
clear of coincident extended emission. Other rotational lines of CO also sample the gas-phase CO reservoir, albeit with different
biases; CO(6−5) traces warmer molecular gas. A rarefied atomic gas could be traced in [C](2−1), but no C detections in disks exist.
Aims. Our goals are to identify gas-rich systems that are bright in CO(6−5), for subsequent ALMA observations, and search for C.
Methods. We follow-up a CO(3−2) survey in protoplanetary disks with APEX/CHAMP+ maps in CO(6−5) 691.4 GHz
and [C](2−1) 809.3 GHz.
Results. We obtain one compact CO(6−5) detection in HD 142 527, three upper limits, and extended CO(6−5) emission in HD 37389.
Given the CO(2−1) flux, the CO(6−5) line in HD 142527 would imply a temperature of 19 K if the CO ladder was isothermal, for a
common solid angle, which is close to CO freezeout. This low temperature, together with a modulated CO(6−5) line profile, can be
explained by a 400 pointing offset. The C observations yield upper limits on the mass of rarefied gas phase neutral carbon.
Conclusions. The CO(6−5) detection in HD 142527 adds to the other two southern systems with known CO(6−5) signal (HD 100546
and TW Hya). The CO(6−5)/CO(3−2) flux ratio varies from 2 to 24 among seven sources with bona-fide CO(6−5) detections, and
is uncorrelated with spectral type in this sample. The upper limits on CI emission constrain the fraction of carbon in low-density
(<103
cm−3
) atomic gas to <4 × 10−3
(3σ).