Context. Intermediate-mass young stellar objects (YSOs) provide a link to understanding how feedback from shocks and UV radiation scales from low- to high-mass star forming regions. Aims. Our aim is ...to analyze excitation of CO and H sub(2)O in deeply embedded intermediate-mass YSOs and compare it with similar studies on low-mass and high-mass YSOs. Methods. Herschel/PACS spectral maps are analyzed for six YSOs with bolometric luminosities of L sub(bol) ~ 10 super(2)-10 super(3)L sub(middot in circle). The maps cover spatial scales of ~10 super(4) AU in several CO and H sub(2)O lines located in the ~55-210 mum range. Results. Rotational diagrams of CO show two temperature components at T sub(rot) ~ 320 K and T sub(rot) ~ 700-800 K, comparable to low-and high-mass protostars probed at similar spatial scales. The diagrams for H sub(2)O show a single component at T sub(rot) ~ 130 K, as seen in low-mass protostars, and about 100 K lower than in high-mass protostars. Since the uncertainties in T sub(rot) are on the same order as the difference between the intermediate and high-mass protostars, we cannot conclude whether the change in rotational temperature occurs at a specific luminosity or whether the change is more gradual from low- to high-mass YSOs. Conclusions. Molecular excitation in intermediate-mass protostars is comparable to the central 10 super(3) AU of low-mass protostars and consistent within the uncertainties with the high-mass protostars probed at 3 x 10 super(3) AU scales, suggesting similar shock conditions in all those sources.
New UBV(RI)C observations and radial velocities of the W UMa-type system BD + 14compfn5016 were collected. Changes of the properties of a hot spot, located on the surface of the primary component, ...have been noticed.
During the embedded stage of star formation, bipolar molecular outflows and UV radiation from the protostar are important feedback processes. Our aim is to quantify the feedback, mechanical and ...radiative, for a large sample of low-mass sources in a consistent manner. The outflow activity is compared to radiative feedback in the form of UV heating by the accreting protostar to search for correlations and evolutionary trends. Large-scale maps of 26 young stellar objects, which are part of the Herschel WISH key program are obtained using the CHAMP+ instrument on the Atacama Pathfinder EXperiment, and the HARPB instrument on the James Clerk Maxwell Telescope. The maps are used to determine outflow parameters and the results are compared with higher-J CO lines obtained with Herschel. All sources in our sample show outflow activity, with the spatial extent decreasing from the Class 0 to the Class I stage. The out-flowing gas typically extends to much greater distances than the power-law envelope and therefore influences the surrounding cloud material directly.
Abstract The Origins Space Telescope (Origins) is one of four science and technology definition studies selected by the National Aeronautics and Space Administration (NASA) in preparation of the 2020 ...Astronomy and Astrophysics Decadal survey in the US. Origins will trace the history of our origins from the time dust and heavy elements permanently altered the cosmic landscape to present-day life. It is designed to answer three major science questions: How do galaxies form stars, make metals, and grow their central supermassive black holes from reionization? How do the conditions for habitability develop during the process of planet formation? Do planets orbiting M-dwarf stars support life? Origins operates at mid- to far-infrared wavelengths from ~ 2.8 μm to 588 μm, and is more than 1000 times more sensitive than prior far-IR missions due to its cold (~ 4.5 K) aperture and state-of-the-art instruments.
Context. The gas-solid budget of carbon in protoplanetary disks is related to the composition of the cores and atmospheres of the planets forming in them. The principal gas-phase carbon carriers CO, ...C0, and C+ can now be observed regularly in disks. Aims. The gas-phase carbon abundance in disks has thus far not been well characterized observationally. We obtain new constraints on the C/H ratio in a large sample of disks, and compile an overview of the strength of C i and warm CO emission. Methods. We carried out a survey of the CO 6–5 line and the C i 1–0 and 2–1 lines towards 37 disks with the APEX telescope, and supplemented it with C ii data from the literature. The data are interpreted using a grid of models produced with the DALI disk code. We also investigate how well the gas-phase carbon abundance can be determined in light of parameter uncertainties. Results. The CO 6–5 line is detected in 13 out of 33 sources, C i 1–0 in 6 out of 12, and C i 2–1 in 1 out of 33. With separate deep integrations, the first unambiguous detections of the C i 1–0 line in disks are obtained, in TW Hya and HD 100546. Conclusions. Gas-phase carbon abundance reductions of a factor of 5–10 or more can be identified robustly based on CO and C i detections, assuming reasonable constraints on other parameters. The atomic carbon detection towards TW Hya confirms a factor of 100 reduction of C/Hgas in that disk, while the data are consistent with an ISM-like carbon abundance for HD 100546. In addition, BP Tau, T Cha, HD 139614, HD 141569, and HD 100453 are either carbon-depleted or gas-poor disks. The low C i 2–1 detection rates in the survey mostly reflect insufficient sensitivity for T Tauri disks. The Herbig Ae/Be disks with CO and C ii upper limits below the models are debris-disk-like systems. An increase in sensitivity of roughly order of magnitude compared to our survey is required to obtain useful constraints on the gas-phase C/H ratio in most of the targeted systems.
Context. During the embedded stage of star formation, bipolar molecular outflows and UV radiation from the protostar are important feedback processes. Both processes reflect the accretion onto the ...forming star and affect subsequent collapse or fragmentation of the cloud. Aims. Our aim is to quantify the feedback, mechanical and radiative, for a large sample of low-mass sources in a consistent manner. The outflow activity is compared to radiative feedback in the form of UV heating by the accreting protostar to search for correlations and evolutionary trends. Methods. Large-scale maps of 26 young stellar objects, which are part of the Herschel WISH key program are obtained using the CHAMP+ instrument on the Atacama Pathfinder EXperiment (12CO and 13CO 6−5; Eup ~ 100 K), and the HARP-B instrument on the James Clerk Maxwell Telescope (12CO and 13CO 3−2; Eup ~ 30 K). The maps have high spatial resolution, particularly the CO 6−5 maps taken with a 9″ beam, resolving the morphology of the outflows. The maps are used to determine outflow parameters and the results are compared with higher-J CO lines obtained with Herschel. Envelope models are used to quantify the amount of UV-heated gas and its temperature from 13CO 6−5 observations. Results. All sources in our sample show outflow activity, with the spatial extent decreasing from the Class 0 to the Class I stage. Consistent with previous studies, the outflow force, FCO, is larger for Class 0 sources than for Class I sources, even if their luminosities are comparable. The outflowing gas typically extends to much greater distances than the power-law envelope and therefore influences the surrounding cloud material directly. Comparison of the CO 6−5 results with HIFI H2O and PACS high-J CO lines, both tracing currently shocked gas, shows that the two components are linked, even though the transitions do not probe the same gas. The link does not extend down to CO 3−2. The conclusion is that CO 6−5 depends on the shock characteristics (density and velocity), whereas CO 3−2 is more sensitive to conditions in the surrounding environment (density). The radiative feedback is responsible for increasing the gas temperature by a factor of two, up to 30–50 K, on scales of a few thousand AU, particularly along the direction of the outflow. The mass of the UV heated gas exceeds the mass contained in the entrained outflow in the inner ~3000 AU and is therefore at least as important on small scales.
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