Numerical Simulations of HH 555

We present 3D gasdynamic simulations of the Herbig Haro object HH 555. HH 555 is a bipolar jet emerging from the tip of an elephant trunk entering the Pelican Nebula from the adjacent molecular cloud. Both beams of HH 555 are curved away from the center of the H II region. This indicates that they are being deflected by a side-wind probably coming from a star located inside the nebula or by the expansion of the nebula itself. HH 555 is most likely an irradiated jet emerging from a highly embedded protostar, which has not yet been detected. In our simulations we vary the incident photon flux, which in one of our models is equal to the flux coming from a star 1 pc away emitting 5x10^48 ionizing (i. e., with energies above the H Lyman limit) photons per second. An external, plane-parallel flow (a ``side-wind'') is coming from the same direction as the photoionizing flux. We have made four simulations, decreasing the photon flux by a factor of 10 in each simulation. We discuss the properties of the flow and we compute Halpha emission maps (integrated along lines of sight). We show that the level of the incident photon flux has an important influence on the shape and visibility of the jet. If the flux is very high, it causes a strong evaporation of the neutral clump, producing a photoevaporated wind traveling in the direction opposite to the incident flow. The interaction of the two flows creates a double shock ``working surface'' around the clump protecting it and the jet from the external flow. The jet only starts to curve when it penetrates through the working surface.Comment: 14 pages, 4 figures, accepted by Ap

A latitude-dependent wind model for Mira's cometary head

We present a 3D numerical simulation of the recently discovered cometary structure produced as Mira travels through the galactic ISM. In our simulation, we consider that Mira ejects a steady, latitude-dependent wind, which interacts with a homogeneous, streaming environment. The axisymmetry of the problem is broken by the lack of alignment between the direction of the relative motion of the environment and the polar axis of the latitude-dependent wind. With this model, we are able to produce a cometary head with a ``double bow shock'' which agrees well with the structure of the head of Mira's comet. We therefore conclude that a time-dependence in the ejected wind is not required for reproducing the observed double bow shock.Comment: 4 pages, 4 figures, accepted for publication in ApJ

A model of Mira's cometary head/tail entering the Local Bubble

We model the cometary structure around Mira as the interaction of an AGB wind from Mira A, and a streaming environment. Our simulations introduce the following new element: we assume that after 200 kyr of evolution in a dense environment Mira entered the Local Bubble (low density coronal gas). As Mira enters the bubble, the head of the comet expands quite rapidly, while the tail remains well collimated for a 100 kyr timescale. The result is a broad-head/narrow-tail structure that resembles the observed morphology of Mira's comet. The simulations were carried out with our new adaptive grid code WALICXE, which is described in detail.Comment: 12 pages, 8 figures (4 in color). Accepted for publication in The Astrophysical Journa

Emission lines from rotating proto-stellar jets with variable velocity profiles. I. Three-dimensional numerical simulation of the non-magnetic case

Using the Yguazu-a three-dimensional hydrodynamic code, we have computed a set of numerical simulations of heavy, supersonic, radiatively cooling jets including variabilities in both the ejection direction (precession) and the jet velocity (intermittence). In order to investigate the effects of jet rotation on the shape of the line profiles, we also introduce an initial toroidal rotation velocity profile, in agreement with some recent observational evidence found in jets from T Tauri stars which seems to support the presence of a rotation velocity pattern inside the jet beam, near the jet production region. Since the Yguazu-a code includes an atomic/ionic network, we are able to compute the emission coefficients for several emission lines, and we generate line profiles for the H, [O I]6300, [S II]6716 and [N II]6548 lines. Using initial parameters that are suitable for the DG Tau microjet, we show that the computed radial velocity shift for the medium-velocity component of the line profile as a function of distance from the jet axis is strikingly similar for rotating and non-rotating jet models. These findings lead us to put forward some caveats on the interpretation of the observed radial velocity distribution from a few outflows from young stellar objects, and we claim that these data should not be directly used as a doubtless confirmation of the magnetocentrifugal wind acceleration models.Comment: 15 pages, 8 figures. Accepted to publication in Astronomy and Astrophysic

A precessing jet model for the PN K 3-35: simulated radio-continuum emission

The bipolar morphology of the planetary nebula (PN) K 3-35 observed in radio-continuum images was modelled with 3D hydrodynamic simulations with the adaptive grid code yguazu-a. We find that the observed morphology of this PN can be reproduced considering a precessing jet evolving in a dense AGB circumstellar medium, given by a mass loss rate \dot{M}_{csm}=5x10^{-5}M_{\odot}/yr and a terminal velocity v_{w}=10 km/s. Synthetic thermal radio-continuum maps were generated from numerical results for several frequencies. Comparing the maps and the total fluxes obtained from the simulations with the observational results, we find that a model of precessing dense jets, where each jet injects material into the surrounding CSM at a rate \dot{M}_j=2.8x10^{-4} {M_{\odot}/yr (equivalent to a density of 8x10^{4} {cm}^{-3}, a velocity of 1500 km/s, a precession period of 100 yr, and a semi-aperture precession angle of 20 degrees agrees well with the observations.Comment: 6 pages, 4 figures, accepted to MNRA

Filaments in Galactic Winds Driven by Young Stellar Clusters

The starburst galaxy M82 shows a system of H$\alpha$-emitting filaments which extend to each side of the galactic disk. We model these filaments as the result of the interaction between the winds from a distribution of Super Stellar Clusters (SSCs). We first derive the condition necessary for producing a radiative interaction between the cluster winds (a condition which is met by the SSC distribution of M82). We then compute 3D simulations for SSC wind distributions which satisfy the condition for a radiative interaction, and also for distributions which do not satisfy this condition. We find that the highly radiative models, that result from the interaction of high metallicity cluster winds, produce a structure of H$\alpha$ emitting filaments, which qualitatively agrees with the observations of the M82, while the non-radiative SSC wind interaction models do not produce filamentary structures. Therefore, our criterion for radiative interactions (which depends on the mass loss rate and the terminal velocity of the SSC winds, and the mean separation between SSCs) can be used to predict whether or not an observed galaxy should have associated H$\alpha$ emitting filaments.Comment: 10 pages, 6 Figures. ApJ Accepted, August 7, 200

PENGARUH DISIPLIN KERJA DAN MOTIVASI KERJA TERHADAP KINERJA KARYAWAN PADA PT. JASA ANGKASA SEMESTA SURABAYA

Sumber daya manusia memiliki peran yang penting baik secara perorangan ataupun kelompok, dan sumber daya manusia merupakan salah satu penggerak utama atas kelancaran jalannya kegiatan sebuah organisasi. Berdasarkan data menurunnya hasil kinerja karyawan pada tahun 2016 dari target yang diberikan oleh perusahaan, diketahui karena kurangnya disiplin dan motivasi kerja yang dianggap kurang menyeluruh oleh karyawan. Penelitian ini bertujuan untuk mengetahui pengaruh disiplin kerja dan motivasi kerja terhadap kinerja karyawan pada PT. Jasa Angkasa Semesta Surabaya. Sampel yang digunakan dalam penelitian ini adalah semua karyawan yang bekerja di PT. Jasa Angkasa Semesta Surabaya yang berjumlah 60 orang. Teknik penentuan sampel yang digunakan yaitu teknik sampel jenuh yang artinya teknik penentuan sampel dengan menggunakan semua anggota populasi. Teknik analis yang digunakan dalam penelitian ini adalah Partial Least Square (PLS). Berdasarkan hasil penelitian menyimpulkan bahwa Disiplin Kerja dan Motivasi Kerja yang tinggi mampu meningkatkan Kinerja Karyawan pada PT. Jasa Angkasa Semesta di Surabaya. Keyword : Disiplin Kerja, Motivasi Kerja, dan Kinerja Karyawa

Time-dependent ejection velocity model for the outflow of Hen 3--1475

We present 2D axisymmetric and 3D numerical simulations of the proto-planetary nebula Hen 3-1475, which is characterized by a remarkably highly collimated optical jet, formed by a string of shock-excited knots along the axis of the nebula. It has recently been suggested that the kinematical and morphological properties of the Hen 3-1475 jet could be the result of an ejection variability of the central source (Riera et al. 2003). The observations suggest a periodic variability of the ejection velocity superimposed on a smoothly increasing ejection velocity ramp. From our numerical simulations, we have obtained intensity maps (for different optical emission lines) and position-velocity diagrams, in order to make a direct comparison with the HST observations of this object. Our numerical study allows us to conclude that a model of a precessing jet with a time-dependent ejection velocity, which is propagating into an ISM previously perturbed by an AGB wind, can succesfully explain both the morphological and the kinematical characteristics of this proto-planetary nebula.Comment: Astronomy and Astrophysics (accepted) (8 figures