Water abundance variations around high-mass protostars: HIFI observations of the DR21 region

Context. Water is a key molecule in the star formation process, but its spatial distribution in star-forming regions is not well known. Aims. We study the distribution of dust continuum and H_(2)O and ^(13)CO line emission in DR21, a luminous star-forming region with a powerful outflow and a compact H ii region. Methods. Herschel-HIFI spectra near 1100 GHz show narrow ^(13)CO 10–9 emission and H_(2)O 1_(11)–0_(00) absorption from the dense core and broad emission from the outflow in both lines. The H_(2)O line also shows absorption by a foreground cloud known from ground-based observations of low-J CO lines. Results. The dust continuum emission is extended over 36” FWHM, while the ^(13)CO and H_(2)O lines are confined to ≈24” or less. The foreground absorption appears to peak further North than the other components. Radiative transfer models indicate very low abundances of ~2×10^(-10) for H_(2)O and ~8×10^(-7) for ^(13)CO in the dense core, and higher H_(2)O abundances of ~4×10^(-9) in the foreground cloud and ~7×10^(-7) in the outflow. Conclusions. The high H_(2)O abundance in the warm outflow is probably due to the evaporation of water-rich icy grain mantles, while the H_(2)O abundance is kept down by freeze-out in the dense core and by photodissociation in the foreground cloud

Chemical Modelling of Young Stellar Objects, I. Method and Benchmarks

Upcoming facilities such as the Herschel Space Observatory or ALMA will deliver a wealth of molecular line observations of young stellar objects (YSOs). Based on line fluxes, chemical abundances can then be estimated by radiative transfer calculations. To derive physical properties from abundances, the chemical network needs to be modeled and fitted to the observations. This modeling process is however computationally exceedingly demanding, particularly if in addition to density and temperature, far UV (FUV) irradiation, X-rays, and multi-dimensional geometry have to be considered. We develop a fast tool, suitable for various applications of chemical modeling in YSOs. A grid of the chemical composition of the gas having a density, temperature, FUV irradiation and X-ray flux is pre-calculated as a function of time. A specific interpolation approach is developed to reduce the database to a feasible size. Published models of AFGL 2591 are used to verify the accuracy of the method. A second benchmark test is carried out for FUV sensitive molecules. The novel method for chemical modeling is more than 250,000 times faster than direct modeling and agrees within a mean factor of 1.35. The tool is distributed for public use. In the course of devloping the method, the chemical evolution is explored: We find that X-ray chemistry in envelopes of YSOs can be reproduced by means of an enhanced cosmic-ray ionization rate. We further find that the abundance of CH+ in low-density gas with high ionization can be enhanced by the recombination of doubly ionized carbon (C++) and suggest a new value for the initial abundance of the main sulphur carrier in the hot-core.Comment: Accepted by ApJS. 24 pages, 15 figures. A version with higher resolution images is available from http://www.astro.phys.ethz.ch/staff/simonbr/papgridI.pdf . Online data available at http://www.astro.phys.ethz.ch/chemgrid.html . Second paper of this series of papers available at arXiv:0906.058

A short note on the joint entropy of n/2-wise independence

In this note, we prove a tight lower bound on the joint entropy of $n$ unbiased Bernoulli random variables which are $n/2$-wise independent. For general $k$-wise independence, we give new lower bounds by adapting Navon and Samorodnitsky's Fourier proof of the `LP bound' on error correcting codes. This counts as partial progress on a problem asked by Gavinsky and Pudl\'ak.Comment: 6 pages, some errors fixe

A Parameter Study of the Dust and Gas Temperature in a Field of Young Stars

We model the thermal effect of young stars on their surrounding environment in order to understand clustered star formation. We take radiative heating of dust, dust-gas collisional heating, cosmic-ray heating, and molecular cooling into account. Using Dusty, a spherical continuum radiative transfer code, we model the dust temperature distribution around young stellar objects with various luminosities and surrounding gas and dust density distributions. We have created a grid of dust temperature models, based on our modeling with Dusty, which we can use to calculate the dust temperature in a field of stars with various parameters. We then determine the gas temperature assuming energy balance. Our models can be used to make large-scale simulations of clustered star formation more realistic.Comment: 29 pages, 19 figures. Submitted to Ap

De-blending Deep Herschel Surveys: A Multi-wavelength Approach

Cosmological surveys in the far infrared are known to suffer from confusion. The Bayesian de-blending tool, XID+, currently provides one of the best ways to de-confuse deep Herschel SPIRE images, using a flat flux density prior. This work is to demonstrate that existing multi-wavelength data sets can be exploited to improve XID+ by providing an informed prior, resulting in more accurate and precise extracted flux densities. Photometric data for galaxies in the COSMOS field were used to constrain spectral energy distributions (SEDs) using the fitting tool CIGALE. These SEDs were used to create Gaussian prior estimates in the SPIRE bands for XID+. The multi-wavelength photometry and the extracted SPIRE flux densities were run through CIGALE again to allow us to compare the performance of the two priors. Inferred ALMA flux densities (F$^i$), at 870$\mu$m and 1250$\mu$m, from the best fitting SEDs from the second CIGALE run were compared with measured ALMA flux densities (F$^m$) as an independent performance validation. Similar validations were conducted with the SED modelling and fitting tool MAGPHYS and modified black body functions to test for model dependency. We demonstrate a clear improvement in agreement between the flux densities extracted with XID+ and existing data at other wavelengths when using the new informed Gaussian prior over the original uninformed prior. The residuals between F$^m$ and F$^i$ were calculated. For the Gaussian prior, these residuals, expressed as a multiple of the ALMA error ($\sigma$), have a smaller standard deviation, 7.95$\sigma$ for the Gaussian prior compared to 12.21$\sigma$ for the flat prior, reduced mean, 1.83$\sigma$ compared to 3.44$\sigma$, and have reduced skew to positive values, 7.97 compared to 11.50. These results were determined to not be significantly model dependent. This results in statistically more reliable SPIRE flux densities.Comment: 8 pages, 7 figures, 3 tables. Accepted for publication in A&

Gambaran Tingkat Ketulian pada Tenaga Kerja Ruang Mesin PLTA Sektor Minahasa Wilayah Suluttenggo

Development period at last decay show the requirement of energy electrics non-stoped to experience of the very keen improvement. This matter not only because of more its is the development of industrial development. Limited Copartnership of company of electrics of Regional Sector Minahasa State of North Sulawesi of South-East Gorontalo (PT. Regional PLN Sector Minahasa Suluttenggo) owning three centre’s of hydropower (PLTA) that is PLTA Tonsealama, PLTA Tanggari I and PLTA Tanggari II. In its operation activities, PLTA use the machine equipments yielding noise so hat an effect on to all existing labour. Research Target that is to know the deafness level description at labour in machine room of Regional PLTA Sector Minahasa Suluttenggo. This Research is included in descriptive research use the method survey through transversal crosscut approach (cross sectional), with the responder amount as much 36 people.Result of research indicate that for the right ear 39 % responder is included in normal category is its hearing, 50 % experiencing of light deaf and 11 % is deaf. While result of the left ear 47 % still in normal category, 42 % light and 11 % experiencing of deaf is. Relate at data of result of measurement mount noise in one of unit PLTA at October 2009 and result of May measurement 2010 indicating that at machine room have exceeded the sill of hearing boundary which have been specified by Ministrial Decree of Labour of Number Kep-51/Men/1999 about Value Float The Boundary of Physics Factor at work that is 85 dB for the standard of working 8 hours each day and 40 hours for a week, that is reach 89,5 dB - 92,2 dB.Suggestion for the company to be executing observation to use of Appliance of Ear Protector ( APT) and applying of management of safety and health work to all labour and also for the labour of in order that obedient in use of appliance of protector of moment ear work in place which mount its noise is high. ABSTRAKPeriode pembangunan pada dasawarsa terakhir menunjukkan kebutuhan energi listrik terus mengalami peningkatan yang sangat tajam. Hal ini bukan saja disebabkan oleh semakin banyaknya kebutuhan listrik tiap keluarga tetapi diakibatkan pula oleh semakin besar energi listrik yang digunakan untuk pembangunan dan pengembangan industri. Perseroan Terbatas Perusahaan Listrik Negara Sektor Minahasa Wilayah Sulawesi Utara Tenggara Gorontalo (PT. PLN Sektor Minahasa Wilayah Suluttenggo) yang memiliki 3 Pusat Listrik Tenaga Air (PLTA) yaitu PLTA Tonsealama, PLTA Tanggari I dan PLTA Tanggari II. Dalam kegiatan operasinya PLTA menggunakan peralatan mesin yang menghasilkan kebisingan sehingga berpengaruh bagi para tenaga kerja yang ada. Tujuan penelitian yaitu untuk mengetahui gambaran tingkat ketulian pada tenaga kerja ruang mesin PLTA Sektor Minahasa Wilayah Suluttenggo. Penelitian ini termasuk dalam penelitian deskriptif menggunakan metode survei melalui pendekatan potong lintang (cross sectional), dengan jumlah responden sebanyak 36 orang.Hasil penelitian menunjukkan bahwa untuk telinga kanan 39 % sampel termasuk dalam kategori normal pendengarannya, 50 % mengalami tuli ringan dan 11 % tuli sedang. Sedangkan untuk hasil telinga kiri 47 % masih dalam kategori normal, 42 % tuli ringan dan 11 % mengalami tuli sedang. Mengacu pada data hasil pengukuran tingkat kebisingan di salah satu unit PLTA pada bulan Oktober 2009 dan hasil pengukuran Mei 2010 menunjukkan bahwa pada ruang mesin telah melebihi ambang batas pendengaran yang telah ditetapkan oleh Keputusan Menteri Tenaga Kerja Nomor Kep-51/Men/1999 tentang Nilai Ambang Batas Faktor Fisika di Tempat Kerja yaitu 85 dB untuk standar 8 jam kerja per hari dan 40 jam per minggu, yaitu mencapai 89,5 dB – 92,2 dB.Saran bagi pihak perusahaan agar melaksanakan pengawasan terhadap penggunaan Alat Pelindung Telinga (APT) dan penerapan manajemen keselamatan dan kesehatan kerja bagi para tenaga kerja serta untuk tenaga kerja agar supaya patuh dalam penggunaan alat pelindung telinga saat bekerja di tempat yang tingkat paparan bisingnya tinggi

Observation-assisted optimal control of quantum dynamics

This paper explores the utility of instantaneous and continuous observations in the optimal control of quantum dynamics. Simulations of the processes are performed on several multilevel quantum systems with the goal of population transfer. Optimal control fields are shown to be capable of cooperating or fighting with observations to achieve a good yield, and the nature of the observations may be optimized to more effectively control the quantum dynamics. Quantum observations also can break dynamical symmetries to increase the controllability of a quantum system. The quantum Zeno and anti-Zeno effects induced by observations are the key operating principles in these processes. The results indicate that quantum observations can be effective tools in the control of quantum dynamics

Water emission from the high-mass star-forming region IRAS 17233-3606. High water abundances at high velocities

We investigate the physical and chemical processes at work during the formation of a massive protostar based on the observation of water in an outflow from a very young object previously detected in H2 and SiO in the IRAS 17233-3606 region. We estimated the abundance of water to understand its chemistry, and to constrain the mass of the emitting outflow. We present new observations of shocked water obtained with the HIFI receiver onboard Herschel. We detected water at high velocities in a range similar to SiO. We self-consistently fitted these observations along with previous SiO data through a state-of-the-art, one-dimensional, stationary C-shock model. We found that a single model can explain the SiO and H2O emission in the red and blue wings of the spectra. Remarkably, one common area, similar to that found for H2 emission, fits both the SiO and H2O emission regions. This shock model subsequently allowed us to assess the shocked water column density, N(H2O)=1.2x10^{18} cm^{-2}, mass, M(H2O)=12.5 M_earth, and its maximum fractional abundance with respect to the total density, x(H2O)=1.4x10^{-4}. The corresponding water abundance in fractional column density units ranges between 2.5x10^{-5} and 1.2x10^{-5}, in agreement with recent results obtained in outflows from low- and high-mass young stellar objects.Comment: accepted for publication as a Letter in Astronomy and Astrophysic