In view of both the size of its gap and the previously reported asymmetries and near-infrared spiral arms, the transition disk of the Herbig Fe star HD 142527 constitutes a remarkable case study. This paper focuses on the morphology of the outer disk
through ALMA observations of $^{12}$CO J=2-1, $^{12}$CO J=3-2 and $^{13}$CO J=2-1. Both $^{12}$CO J=2-1 and $^{12}$CO J=3-2 show spiral features of different sizes. The innermost spiral arm (S1) is a radio counterpart of the first near-infrared spiral observed by Fukagawa et al. (2006), but it is shifted radially outward. However, the most conspicuous CO spiral arm (S2) lies at the outskirts of the disk and had not been detected before. It corresponds to a cold density structure, with both brightness and excitation temperatures of order 13$pm$2 K and conspicuous in the $^{12}$CO J=2-1 peak-intensity map, but faint in $^{12}$CO J=3-2. There is also a faint counterarm (S3), point-symmetrical of S2 with respect to the star. These three spirals are modelled separately with two different formulae that approximate the loci of density maxima in acoustic waves due to embedded planets. S1 could be fit relatively well with these formulae, compared to S2 and S3. Alternative scenarios such as gravitational instability or external tidal interaction are discussed. The impact of channelization on spectrally and spatially resolved peak intensity maps is also briefly addressed.
A preliminary VLT-UVES spectrum of NGC 6302 (Casassus et al. 2002, MN), which hosts one of the hottest PN nuclei known (Teff ~ 220000 K; Wright et al. 2011, MN), has been recently analysed by means of X-SSN, a spectrum synthesis code for nebulae (Mor
isset and Pequignot). Permitted recombination lines from highly-ionized species are detected/identified for the first time in a PN, and some of them probably for the first time in (Astro)Physics. The need for a homogeneous, high signal-to-noise UVES spectrum for NGC 6302 is advocated.
We present near-infrared VLT ISAAC imaging and spectroscopy of the peculiar Virgo galaxy NGC 4438, whose nucleus has been classified as a LINER. The data are supplemented by mid-infrared imaging, and compared to previous WFPC2 HST broadband images. I
mages and position-velocity maps of the [Fe II] and H2 line emissions are presented and compared with the distribution of the optical narrow-line region and radio features. Our results show that shocks (possibly driven by a radio jet) contribute to an important fraction of the excitation of [Fe II], while X-ray heating from a central AGN may be responsible for the H2 excitation. We address the question whether the outflow has an AGN or a starburst origin by providing new estimates of the central star formation rate and the kinetic energy associated with the gas. By fitting a Sersic bulge, an exponential disc and a compact nuclear source to the light distribution, we decomposed NGC 4438s light distribution and found an unresolved nuclear source at 0.8 arcsec resolution with M_K = -18.7 and J-H = 0.69. Our measured bulge velocity dispersion, 142 km/s, together with the standard M_bh-sigma relation, suggests a central black hole mass of log(M_bh/Msun) ~ 7.0. The stellar kinematics measured from the near-infrared CO lines shows a strong peak in the velocity dispersion of 178 km/s in the central 0.5 arcsec, which is possible kinematic evidence of a central black hole. We calculated a general expression for the integrated Sersic profile flux density in elliptical geometry, including the case of disky isophotes.
The rho Oph molecular cloud is undergoing intermediate-mass star formation. UV radiation from its hottest young stars heats and dissociates exposed layers, but does not ionize hydrogen. Only faint radiation from the Rayleigh-Jeans tail of ~10-100K du
st is expected at wavelengths longwards of 3mm. Yet Cosmic Background Imager (CBI) observations reveal that the rho Oph W photo-dissociation region (PDR) is surprisingly bright at centimetre wavelengths. We searched for interpretations consistent with the WMAP radio spectrum, new ISO-LWS parallel mode images and archival Spitzer data. Dust-related emission mechanisms at 1 cm, as proposed by Draine & Lazarian, are a possibility. But a magnetic enhancement of the grain opacity at 1cm is inconsistent with the morphology of the dust column maps Nd and the lack of detected polarization. Spinning dust, or electric-dipole radiation from spinning very small grains (VSGs), comfortably explains the radio spectrum, although not the conspicuous absence from the CBI data of the infrared circumstellar nebulae around the B-type stars S1 and SR~3. Allowing for VSG depletion can marginally reconcile spinning dust with the data. As an alternative interpretation we consider the continuum from residual charges in rho Oph W, where most of carbon should be photoionised by the close binary HD147889 (B2IV, B3IV). Electron densities of ~100 cm^{-3}, or H-nucleus densities n_H > 1E6 cm^{-3}, are required to interpret rho Oph W as the CII Stromgren sphere of HD147889. However the observed steep and positive low-frequency spectral index would then require optically thick emission from an hitherto unobserved ensemble of dense clumps or sheets with a filling factor ~1E-4 and n_H ~ 1E7 cm^{-3}.
