Astronomical instrumentation

Abstract:

We investigate the Galactic disc distribution of a sample of planetary nebulae characterized in terms of their mid-infrared spectral features. The total number of Galactic disc PNe with 8-13 μm spectra is brought up to 74 with the inclusion of 24 new objects, the spectra of which we present for the first time. 54 PNe have clearly identified warm dust emission features, and form a sample that we use to construct the distribution of the C/O chemical balance in Galactic disc PNe. The dust emission features complement the information on the progenitor masses brought by the gas-phase N/O ratios: PNe with unidentified infrared emission bands have the highest N/O ratios, while PNe with the silicate signature have either very high N enrichment or close to none. We find a trend for a decreasing proportion of O-rich PNe towards the third and fourth Galactic quadrants. Two independent distance scales confirm that the proportion of O-rich PNe decreases from 30 ± 9 per cent inside the solar circle to 14 ± 7 per cent outside. PNe with warm dust are also the youngest. PNe with no warm dust are uniformly distributed in C/O and N/O ratios, and do not appear to be confined to C/O ∼ 1. They also have higher 6-cm fluxes, as expected from more evolved PNe. We show that the IRAS fluxes are a good representation of the bolometric flux for compact and IR-bright PNe, which are probably optically thick. Selection of objects with F(12 μm) > 0.5 Jy should probe a good portion of the Galactic disc for these young, dense and compact nebulae, and the dominant selection effects are rooted in the PN catalogues.

Abstract:

Progress in understanding the embedded stars in LkHa225 has been hampered by their variability, making it hard to compare data taken at different times, and by the limited resolution of the available data, which cannot probe the small scales between the two stars. In an attempt to overcome these difficulties, we present new near-infrared data on this object taken using the ALFA adaptive optics system with the MPE 3D integral field spectrometer and the near-infrared camera Omega-Cass. The stars themselves have K-band spectra which are dominated by warm dust emission, analagous to class I-II for low mass YSOs, suggesting that the stars are in a phase where they are still accreting matter. On the other hand, the ridge of continuum emission between them is rather bluer, suggestive of extincted and/or scattered stellar light rather than direct dust emission. The compactness of the CO emission seen toward each star argues for accretion disks (which can also account for much of the K-band veiling) rather than a neutral wind. In contrast to other YSOs with CO emission, LkHa225 has no detectable Br_gamma emission. Additionally there is no H_2 detected on the northern star, although we do confirm that the strongest H_2 emission is on the southern star, where we find it is excited primarily by thermal mechanisms. A second knot of H_2 is observed to its northeast, with a velocity shift of -75kms and a higher fraction of non-thermal emission. This is discussed with reference to the H2O maser, the molecular outflow, and [S II] emission observed between the stars.

Abstract:

We present deep optical and near infrared imaging over half square degree of sky in the centres of the ELAIS regions N1 and N2 and coincident with deep XMM/Chandra observations. The data have been obtained with the Wide Field Camera (WFC) and the Cambridge InfraRed Survey Instrument (CIRSI) both at the Isaac Newton Telescope (Observatorio del Roque de los Muchachos, Canary Islands). Limiting magnitudes achieved are g'=26.7, r'=26.2, i'=25.0 and H=20.2 (3σ). These data have been used to identify the faint optical counterparts of the Infrared Space Observatory (ISO), radio and X-ray sources in these areas.

Abstract:

We present the properties of all the galaxies detected by ISO at 7, 15 and 90μm in ELAIS northern fields. The spectral energy distribution (SED) of those 20 galaxies with IRAS detections can generally be well fitted by a predominant cirrus component plus a modest starburst contribution. Follow-up spectroscopy has shown that all the objects are emission-line galaxies but without a very intense star formation event. Most of the galaxies analyzed by means of optical R band photometry result to host an important exponential disk component, in good agreement with the SED IR modelling. We note that galaxies with morphological signs of perturbations seem to show slightly higher f15/f6.7 ratios, indicating that star formation could be more important in them. One of the objects is a broad-line, radio-quiet quasar at z=1.099; its spectral energy distribution indicates that it is a hyperluminous infrared galaxy (HLIG), the first HLIG detected in the ELAIS areas.