We present results of far-infrared photometric observations with Herschel PACS of a sample of Upper Scorpius stars, with a detection rate of previously known disk-bearing K and M stars at 70, 100,... Show moreWe present results of far-infrared photometric observations with Herschel PACS of a sample of Upper Scorpius stars, with a detection rate of previously known disk-bearing K and M stars at 70, 100, and 160 {$μ$}m of 71%, 56%, and 50%, respectively. We fit power-law disk models to the spectral energy distributions of K {amp} M stars with infrared excesses, and have found that while many disks extend in to the sublimation radius, the dust has settled to lower scale heights than in disks of the less evolved Taurus-Auriga population, and have much reduced dust masses. We also conducted Herschel PACS observations for far-infrared line emission and JCMT observations for millimeter CO lines. Among B and A stars, 0 of 5 debris disk hosts exhibit gas line emission, and among K and M stars, only 2 of 14 dusty disk hosts are detected. The OI 63 {$μ$}m and CII 157 {$μ$}m lines are detected toward [PZ99] J160421.7-213028 and [PBB2002] J161420.3-190648, which were found in millimeter photometry to host two of the most massive dust disks remaining in the region. Comparison of the OI line emission and 63 {$μ$}m continuum to that of Taurus sources suggests the emission in the former source is dominated by the disk, while in the other there is a significant contribution from a jet. The low dust masses found by disk modeling and low number of gas line detections suggest that few stars in Upper Scorpius retain sufficient quantities of material for giant planet formation. By the age of Upper Scorpius, giant planet formation is essentially complete. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. Show less
Klaassen, P.D.; Juhasz, A.; Mathews, G.S.; Mottram, J.C.; De Gregorio-Monsalvo, I.; Dishoeck, E.F. van; ... ; Testi, L. 2013
Disk winds have been postulated as a mechanism for angular momentum release in protostellar systems for decades. HD 163296 is a Herbig Ae star surrounded by a disk and has been shown to host a... Show moreDisk winds have been postulated as a mechanism for angular momentum release in protostellar systems for decades. HD 163296 is a Herbig Ae star surrounded by a disk and has been shown to host a series of HH knots (HH 409) with bow shocks associated with the farthest knots. Here we present ALMA science verification data of CO J = 2-1 and J = 3-2 emission, which are spatially coincident with the blue shifted jet of HH knots, and offset from the disk by -18.6 km s$^{-1}$. The emission has a double corkscrew morphology and extends more than 10'' from the disk with embedded emission clumps coincident with jet knots. We interpret this double corkscrew as emission from material in a molecular disk wind, and that the compact emission near the jet knots is being heated by the jet that is moving at much higher velocities. We show that the J = 3-2 emission is likely heavily filtered by the interferometer, but the J = 2-1 emission suffers less due to the larger beam and sensitivity to larger scale structures. Excitation analysis suggests temperatures exceeding 900 K in these compact features, with the wind mass, momentum and energy being of order 10$^{-5}$ M$_{⊙}$, 10$^{-4}$ M$_{⊙}$ km s$^{-1}$ and 10$^{40}$ erg, respectively. The high mass loss rate suggests that this star is dispersing the disk faster than it is funneling mass onto the star. Show less
The Herschel Space Observatory was used to observe ~{}120 pre-main-sequence stars in Taurus as part of the GASPS Open Time Key project. Photodetector Array Camera and Spectrometer was used to... Show moreThe Herschel Space Observatory was used to observe ~{}120 pre-main-sequence stars in Taurus as part of the GASPS Open Time Key project. Photodetector Array Camera and Spectrometer was used to measure the continuum as well as several gas tracers such as [O I] 63 {$μ$}m, [O I] 145 {$μ$}m, [C II] 158 {$μ$}m, OH, H$_{2}$O, and CO. The strongest line seen is [O I] at 63 {$μ$}m. We find a clear correlation between the strength of the [O I] 63 {$μ$}m line and the 63 {$μ$}m continuum for disk sources. In outflow sources, the line emission can be up to 20 times stronger than in disk sources, suggesting that the line emission is dominated by the outflow. The tight correlation seen for disk sources suggests that the emission arises from the inner disk ({lt}50 AU) and lower surface layers of the disk where the gas and dust are coupled. The [O I] 63 {$μ$}m is fainter in transitional stars than in normal Class II disks. Simple spectral energy distribution models indicate that the dust responsible for the continuum emission is colder in these disks, leading to weaker line emission. [C II] 158 {$μ$}m emission is only detected in strong outflow sources. The observed line ratios of [O I] 63 {$μ$}m to [O I] 145 {$μ$}m are in the regime where we are insensitive to the gas-to-dust ratio, neither can we discriminate between shock or photodissociation region emission. We detect no Class III object in [O I] 63 {$μ$}m and only three in continuum, at least one of which is a candidate debris disk. Show less
Gregorio-Monsalvo, I.; Ménard, F.; Dent, W.; Pinte, C.; López, C.; Klaassen, P.D.; ... ; Van Kempen, T. 2013
Aims: The aim of this work is to study the structure of the protoplanetary disk surrounding the Herbig Ae star HD 163296. Methods: We used high-resolution and high-sensitivity ALMA observations... Show moreAims: The aim of this work is to study the structure of the protoplanetary disk surrounding the Herbig Ae star HD 163296. Methods: We used high-resolution and high-sensitivity ALMA observations of the CO(3-2) emission line and the continuum at 850 {$μ$}m, as well as the three-dimensional Monte Carlo radiative transfer code, MCFOST, to model the data presented in this work. Results: The CO(3-2) emission unveils for the first time at submillimeter frequencies the vertical structure details of a gaseous disk in Keplerian rotation, showing the back and front sides of a flared disk. Continuum emission at 850 {$μ$}m reveals a compact dust disk with a 240 AU outer radius and a surface brightness profile that shows a very steep decline at radius larger than 125 AU. The gaseous disk is more than two times larger than the dust disk, with a similar critical radius but with a shallower radial profile. Radiative transfer models of the continuum data confirm the need for a sharp outer edge to the dust disk. The models for the CO(3-2) channel map require the disk to be slightly more geometrically thick than previous models suggested, and that the temperature at which CO gas becomes depleted (i.e., frozen out) from the outer regions of the disk midplane is T {lt} 20 K, in agreement with previous studies. Show less
