P. Boumis

The distribution of the ISM in the Milky Way - A three-dimensional large-scale model

We use the COBE/DIRBE (1.2, 2.2, 60, 100, 140, and 240 µm) maps and the COBE/FIRAS spectra (for the wavelength range 100−1000 µm) to constrain a model for the spatial distribution of the dust, the stars, and the gas in the Milky Way. By assuming exponential axisymmetric distributions for the dust and the stars and by performing the corresponding radiative transfer calculations we closely (given the simple geometry of the model) reproduce the FIR and NIR maps of the Milky Way. Similar distributions for the atomic and molecular hydrogen in the disk are used (with an inner cut-off radius for the atomic hydrogen) to fit the gas data. The star formation rate as a function of the Galactic radius is derived from the FIR emission and is well in agreement with existing estimates from various star formation tracers. The gas surface density is plotted against the star formation rate density and an “intrinsic” Galactic Schmidt law is derived with excellent agreement with the “external” Schmidt law found for spiral galaxies. The Milky Way is found to consume ∼1% and ∼10% of its gas in the outer and inner regions respectively (for a period of 0.1 Gyr) to make stars. The dust-induced B − V color excess observed in various directions and distances (up to ∼6.5 kpc) with well-studied Cepheid stars is compared with the model predictions showing a good agreement. The simple assumption of exponential distributions of stars and dust in the Galaxy is found to be quite instructive and adequate in modeling all the available data sets from 0.45 µ m( B-band) to 1000 µm.

Deep optical observations of the interaction of the SS 433 microquasar jet with the W50 radio continuum shell

Four mosaics of deep, continuum-subtracted, CCD images have been obtained over the extensive Galactic radio continuum shell, W50, which surrounds the remarkable stellar system SS 433. Two of these mosaics in the Hα + [N II] and [O III] 5007 A emission lines, respectively, cover a field of ∼2. ◦ 3 × 2. 5 which contains all of W50 but at a low angular resolution of 5 arcsec. The third and fourth mosaics cover the eastern (in [O III] 5007 A) and western (in Hα + [N II] 6548, 6584 A) filamentary nebulosity, respectively, but at an angular resolution of 1 arcsec. These observations are supplemented by new low-dispersion spectra and longslit, spatially resolved echelle spectra. The [O III] 5007 A images show for the first time the distribution of this emission in both the eastern and western filaments while new Hα + [N II] emission features are also found in both of these regions. Approaching flows of faintly emitting material from the bright eastern filaments of up 100 km s −1 in radial velocity are detected. The present observations also suggest that the heliocentric systemic radial velocity of the whole system is 56 ± 2k m s −1 . Furthermore, very deep imagery and high-resolution spectroscopy of a small part of the northern radio ridge of W50 has revealed for the first time the very faint optical nebulosity associated with this edge. It is suggested that patchy foreground dust along the ≈5 kpc sightline is inhibiting the detection of all of the optical nebulosity associated with W50. The interaction of the microquasar jets of SS 433 with the W50 shell is discussed.

Flows along cometary tails in the Helix planetary nebula NGC 7293

Previous velocity images which reveal flows of ionized gas along the most prominent cometary tail (from Knot 38) in the Helix planetary nebula are compared with that taken at optical wavelengths with the Hubble Space Telescope and with an image in the emission from molecular hydrogen. The flows from the second most prominent tail from Knot 14 are also considered. The kinematics of the tail from the more complex Knot 32, shown here for the first time, also reveal an acceleration away from the central star. All of the tails are explained as accelerating ionized flows of ablated material driven by the previous, mildly supersonic, asymptotic giant branch wind from the central star. The longest tail of ionized gas, even though formed by this mechanism in a very clumpy medium, as revealed by the emission from molecular hydrogen, appears to be a coherent outflowing feature.

Discovery of optical emission from the supernova remnant G 32.8 0.1 (Kes 78)

Deep optical CCD images of the supernova remnant G 32.8−0.1 were obtained where filamentary and diffuse emission was discovered. The images were acquired in the emission lines of Hα + [N ii ]a nd [Sii]. Filamentary and diffuse structures are detected in most areas of the remnant, while no significant [O iii] emission is present. The flux-calibrated images suggest that the optical emission originates from shock-heated gas since the [S ii]/Hα ratio is greater than 1.2. The Spitzer images at 8 μm and 24 μm show a few filamentary structures to be correlated with the optical filaments, while the radio emission at 1.4 GHz in the same area is found to be very well correlated with the brightest optical filaments. The results from deep long-slit spectra also support the origin of the emission being from shock-heated gas ([S ii]/H α> 1.5). The absence of [O iii] emission indicates slow shock velocities into the interstellar “clouds” (≤100 km s −1 ), while the [S ii]λλ 6716/6731 ratio indicates electron densities up to ∼200 cm −3 .T he Hα emission is measured to lie between 1.8 to 4.6 × 10 −17 erg s −1 cm −2 arcsec −2 , while from VGPS Hi images the distance to the SNR is estimated to be between 6 to 8.5 kpc.

Deciphering the bipolar planetary nebula Abell 14 with 3D ionization and morphological studies

Abell 14 is a poorly studied object despite being considered a born again planetary nebula. We performed a detailed study of its 3D morphology and ionization structure using the SHAPE and MOCASSIN codes. We found that Abell 14 is a highly evolved, bipolar nebula with a kinematical age of

The expansion proper motions of the extraordinary giant lobes of the planetary nebula KjPn 8 revisited

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Two rings but no fellowship: LoTr 1 and its relation to planetary nebulae possessing barium central stars.

19,400 yr for a distance of 4 kpc. The high He abundance, and N/O ratio indicate a progenitor of 5

Deep optical observations of the supernova remnants G 126.2+1.6, G 59.8+1.2 and G 54.4-0.3

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First optical detection of the supernova remnant G 15.1-1.6

that has experienced the third dredge-up and hot bottom burning phases. The stellar parameters of the central source reveal a star at a highly evolved stage near to the white dwarf cooling track, being inconsistent with the born again scenario. The nebula shows unexpectedly strong [N I]

From Dense Hot Jupiter to Low Density Neptune: The Discovery of WASP-127b, WASP-136b and WASP-138b

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