Extended Far-Infrared CO Emission in the Orion OMC-1 Core

We report on sensitive far-infrared observations of $^{12}$CO pure rotational transitions in the OMC-1 core of Orion. The lines were observed with the Long Wavelength Spectrometer (LWS) in the grating mode on board the Infrared Space Observatory (ISO), covering the 43-197 $\mu$m wavelength range. The transitions from $J_{up}=14$ up to $J_{up}=19$ have been identified across the whole OMC-1 core and lines up to $J_{up}= 43$ have been detected towards the central region, KL/IRc2. In addition, we have taken high-quality spectra in the Fabry-Perot mode of some of the CO lines. In KL/IRc2 the lines are satisfactorily accounted for by a three-temperature model describing the plateau and ridge emission. The fluxes detected in the high-$J$ transitions ($J_{up} > 34$) reveal the presence of a very hot and dense gas component ($T=1500-2500$ K; $\rm N(CO)$=2\times 10^{17}\cmmd$), probably originating from some of the embedded sources previously observed in the$\rm H_2$near-infrared lines. At all other positions in the OMC-1 core, we estimate kinetic temperatures$\geq 80$ K and as high as 150 K at some positions around IRc2, from a simple Large-Velocity Gradient model.Comment: 10 pages, 3 figure

Centimetre continuum emission from young stellar objects in Cederblad 110

The low-mass star formation region associated with the reflection nebula Cederblad 110 in the Chamaeleon I cloud was mapped with the Australian Telescope Compact Array (ATCA) at 6 and 3.5cm. Altogether 11 sources were detected, three of which are previously known low mass young stellar objects associated with the nebula: the illuminating star IRS2 (Class III, Einstein X-ray source CHX7), the brightest far-infrared source IRS4 (Class I), and the weak X-ray source CHX10a (Class III). The other young stellar objects in the region, including the Class 0 protostar candidate Cha-MMS1, were not detected. The radio spectral index of IRS4 (alpha = 1.7 +/- 0.3) is consistent with optically thick free-free emission arising from a dense ionized region, probably a jet-induced shock occurring in the circumstellar material. As the only Class I protostar with a 'thermal jet' IRS4 is the strongest candidate for the central source of the molecular outflow found previously in the region. The emission from IRS2 has a flat spectrum (alpha = 0.05 +/- 0.05) but shows no sign of polarization, and therefore its origin is likely to be optically thin free-free emission either from ionized wind or a collimated jet. The strongest source detected in this survey is a new compact object with a steep negative spectral index (-1.1) and a weak linear polarization (about 2 %), which probably represents a background radio galaxy.Comment: 7 pages, 2 Postscript figures. Accepted for publication in Astronomy & Astrophysic

Orbital Ferromagnetism and Quantum Collapse in Stellar Plasmas

The possibility of quantum collapse and characteristics of nonlinear localized excitations is examined in dense stars with Landau orbital ferromagnetism in the framework of conventional quantum magnetohydrodynamics (QMHD) model including Bohm force and spin-orbit polarization effects. Employing the concepts of effective potential and Sagdeev pseudopotential, it is confirmed that the quantum collapse and Landau orbital ferromagnetism concepts are consistent with the magnetic field and mass-density range present in some white dwarf stars. Furthermore, the value of ferromagnetic-field found in this work is about the same order of magnitude as the values calculated earlier. It is revealed that the magnetosonic nonlinear propagations can behave much differently in the two distinct non-relativistic and relativistic degeneracy regimes in a ferromagnetic dense astrophysical object. Current findings should help to understand the origin of the most important mechanisms such as gravitational collapse and the high magnetic field present in many compact stars.Comment: To appear in journal Physics of Plasma

A rotating molecular jet in Orion

We present CO(2-1), $^{13}$CO(2-1), CO(6-5), CO(7-6), and SO(6$_5-5_4$) line observations made with the {\it IRAM 30 m} and {\it APEX} radiotelescopes and the {\it Submillimeter Array} toward the highly collimated and extended southwest lobe of the bipolar outflow {\it Ori-S6} located in the Orion South region. We report, for all these lines, the detection of velocity asymmetries about the flow axis, with velocity differences roughly on the order of 1 km s$^{-1}$ over distances of about 5000 AU, 4 km s$^{-1}$ over distances of about 2000 AU, and close to the source of between 7 and 11 km s$^{-1}$ over smaller scales of about 1000 AU. We interpret these velocity differences as a signature of rotation but also discuss some alternatives which we recognize as unlikely in view of the asymmetries' large downstream continuation. This rotation across the {\it Ori-S6} outflow is observed out to (projected) distances beyond 2.5 $\times$ 10$^4$ AU from the flow's presumed origin. Comparison of our large-scale and small-scale observations suggests the rotational velocity to decline not faster than 1/R with distance R from the axis; in the innermost few arcsecs an increase of rotational velocity with R is even indicated. The magnetic field lines threading the inner rotating CO shell may well be anchored in a disk of radius $\sim$ 50 AU; the field lines further out need a more extended rotating base.Comment: Accepted by Astronomy and Astrophysic

Field-Induced Degeneracy Regimes in Quantum Plasmas

It is shown that in degenerate magnetized Fermi-Dirac plasma where the electron-orbital are quantized distinct quantum hydrodynamic (QHD) limits exist in which the nonlinear density waves behave differently. The Coulomb interaction among degenerate electrons affect the electrostatic nonlinear wave dynamics more significant in the ground-state Landau quantization or the so-called quantum-limit ($l=0$) rather than in the classical-limit ($l=\infty$). It is also remarked that the effective electron quantum potential unlike the number-density and degeneracy pressure is independent of the applied magnetic field in the classical-limit plasma, while, it depends strongly on the field strength in the quantum-limit. Current findings are equally important in the study of wave dynamics in arbitrarily-high magnetized astrophysical and laboratory dense plasmas.Comment: To appear in journal Physics of Plasma

Compton Scattering in Static and Moving Media. II. System-Frame Solutions for Spherically Symmetric Flows

I study the formation of Comptonization spectra in spherically symmetric, fast moving media in a flat spacetime. I analyze the mathematical character of the moments of the transfer equation in the system-frame and describe a numerical method that provides fast solutions of the time-independent radiative transfer problem that are accurate in both the diffusion and free-streaming regimes. I show that even if the flows are mildly relativistic (V~0.1, where V is the electron bulk velocity in units of the speed of light), terms that are second-order in V alter the emerging spectrum both quantitatively and qualitatively. In particular, terms that are second-order in V produce power-law spectral tails, which are the dominant feature at high energies, and therefore cannot be neglected. I further show that photons from a static source are upscattered by the bulk motion of the medium even if the velocity field does not converge. Finally, I discuss these results in the context of radial accretion onto and outflows from compact objects.Comment: 28 pages, 9 figures; minor changes, to appear in the Astrophysical Journa

Warm Molecular Gas Traced with CO J=7->6 in the Galaxy's Central 2 Parsecs: Dynamical Heating of the Circumnuclear Disk

We present an 11 arcsec resolution map of the central two parsecs of the Galaxy in the CO J =7->6 rotational transition. The CO emission shows rotation about Sgr A*, but also evidence for non-circular turbulent motion and a clumpy morphology. We combine our dataset with available CO measurements to model the physical conditions in the disk. We find that the molecular gas in the region is both warm and dense, with T~200-300 K, n_H2~50,000-70,000 cm^-3. The mass of warm molecular gas we measure in the central two parsecs is at least 2000 M_solar, about 20 times the UV-excited atomic gas mass, ruling out an UV heating scenario for the molecular material. We compare the available spectral tracers with theoretical models and conclude that molecular gas is heated with magneto-hydrodynamic shocks with v~10-20 kms and B~0.3-0.5 mG. Using the conditions derived with the CO analysis, we include the other important coolants--neutral oxygen and molecular hydrogen--to estimate the total cooling budget of the molecular material. We derive a mass to luminosity ratio of 2-3 M_solar/ L_solar, which is consistent with the total power dissipated via turbulent decay in 0.1 pc cells with v_rms~15 kms. These size and velocity scales are comparable to the observed clumping scale and the velocity dispersion. At this rate, the material near Sgr A* its dissipating its orbital energy on an orbital timescale, and cannot last for more than a few orbits. Our conclusions support a scenario in which the features near Sgr A* such as the CND and northern arm are generated by infalling clouds with low specific angular momentum.Comment: 31 pages, including 5 figures, accepted for publication in Ap

Orbital Ferromagnetism and the Chandrasekhar Mass-Limit

In this paper, using both quantum magnetohydrodynamic (MHD) and magnetohydrostatic (MHS) models of a relativistically degenerate magnetic compact star, the fundamental role of Landau orbital ferromagnetism (LOFER) on the magneto-gravitational stability of such star is revealed. It is shown that the previously suggested magnetic equation of state for LOFER with some generalization of form $B=\beta \rho^{2s/3}$ only within the range $0\leq s\leq 1$ and $0\leq \beta< \sqrt{2\pi}$ leads to magneto-gravitational stability with distinct critical value $\beta_{cr}=\sqrt{2\pi}$ governing the magnetohydrostatic stability of the compact star. Furthermore, the value of the parameters $s$ and $\beta$ is shown to fundamentally control both the quantum and Chandrasekhar gravitational collapse mechanisms and the previously discovered mass-limit on white dwarfs. Current findings can help to understand the origin of magnetism and its inevitable role on the stability of the relativistically degenerate super-dense magnetized matter encountered in many white-dwarfs and neutron stars

Low Velocity Ionized Winds from Regions Around Young O Stars

We have observed seven ultracompact HII regions in hydrogen recombination lines in the millimeter band. Toward four of these regions, there is a high velocity (full width to half maximum 60-80 km/s) component in the line profiles. The high velocity gas accounts for 35-70% of the emission measure within the beam. We compare these objects to an additional seven similar sources we have found in the literature. The broad recombination line objects (BRLOs) make up about 30% of all sources in complexes containing ultracompact HII regions. Comparison of spectral line and continuum data implies that the BRLOs coincide with sources with rising spectral indices, >=0.4 up to 100 GHz. Both the number of BRLOs and their frequency of occurrence within HII region complexes, when coupled with their small size and large internal motions, mean that the apparent contradiction between the dynamical and population lifetimes for BRLOs is even more severe than for ultracompact HII regions. We evaluate a number of models for the origin of the broad recombination line emission. The lifetime, morphology, and rising spectral index of the sources argue for photo- evaporated disks as the cause for BRLOs. Existing models for such regions, however, do not account for the large amounts of gas observed at supersonic velocities.Comment: 36 pages, 8 figure

A 2.4 - 12 microns spectrophotometric study with ISO of Cygnus X-3 in quiescence

We present mid-infrared spectrophotometric results obtained with the ISO on the peculiar X-ray binary Cygnus X-3 in quiescence, at orbital phases 0.83 to 1.04. The 2.4-12 microns continuum radiation observed with ISOPHOT-S can be explained by thermal free-free emission in an expanding wind with, above 6.5 microns, a possible additional black-body component with temperature T ~ 250 K and radius R ~ 5000 solar radii at 10 kpc, likely due to thermal emission by circumstellar dust. The observed brightness and continuum spectrum closely match that of the Wolf-Rayet star WR 147, a WN8+B0.5 binary system, when rescaled at the same 10 kpc distance as Cygnus X-3. A rough mass loss estimate assuming a WN wind gives ~ 1.2 10^{-4} M(sun)/yr. A line at ~ 4.3 microns with a more than 4.3 sigma detection level, and with a dereddened flux of 126 mJy, is interpreted as the expected He I 3p-3s line at 4.295 microns, a prominent line in the WR 147 spectrum. These results are consistent with a Wolf-Rayet-like companion to the compact object in Cygnus X-3 of WN8 type, a later type than suggested by earlier works.Comment: 8 pages, 10 figures ; Accepted in A&