Strong irradiation of protostellar cores in Corona Australis

The importance of the physical environment in the evolution of newly formed low-mass stars remains an open question. In particular, radiation from nearby more massive stars may affect both the physical and chemical structure of these kinds of young stars. Aims: To constrain the physical characteristics of a group of embedded low-mass protostars in Corona Australis in the vicinity of the young luminous Herbig Be star R CrA. Methods: Millimetre wavelength maps of molecular line and continuum emission towards the low-mass star forming region IRS7 near R CrA from the SMA and APEX are presented. The maps show the distribution of 18 lines from 7 species (H2CO, CH3OH, HC3N, c-C3H2, HCN, CN and SiO) on scales from 3" to 60" (400-8000 AU). Using a set of H2CO lines, we estimate the temperatures and column densities in the region using LTE and non-LTE methods. The results are compared with 1-D radiative transfer modelling of the protostellar cores. These models constrain which properties of the central source, envelope, and environment can give rise to the observed line and continuum emission. Results: Most of the H2CO emission from the regions emerges from two elongated narrow ridges dominating the emission picked up in both interferometric and single-dish measurements. The temperatures inferred from the H2CO lines are no less than ~30 K and more likely 50-60 K, and the line emission peaks are offset by ~2500 AU from the location of the embedded protostars. The temperatures can not be explained by the heating from the young stellar objects themselves. Irradiation by the nearby Herbig Be star R CrA could, however, explain the high temperatures. The elevated temperatures can in turn impact the physical and chemical characteristics of protostars and lead to enhanced abundances of typical tracers of photon dominated regions seen in single-dish line surveys of embedded protostars in the region.Comment: Accepted for publication in A&A; 21 pages, 28 figures; Added footnote in Section 2.

Urban storage heat flux variability explored using satellite, meteorological and geodata

The storage heat flux (ΔQS) is the net flow of heat stored within a volume that may include the air, trees, buildings and ground. Given the difficulty of measurement of this important and large flux in urban areas, we explore the use of Earth Observation (EO) data. EO surface temperatures are used with ground-based meteorological forcing, urban morphology, land cover and land use information to estimate spatial variations of ΔQS in urban areas using the Element Surface Temperature Method (ESTM). First, we evaluate ESTM for four “simpler” surfaces. These have good agreement with observed values. ESTM coupled to SUEWS (an urban land surface model) is applied to three European cities (Basel, Heraklion, London), allowing EO data to enhance the exploration of the spatial variability in ΔQS. The impervious surfaces (paved and buildings) contribute most to ΔQS. Building wall area seems to explain variation of ΔQS most consistently. As the paved fraction increases up to 0.4, there is a clear increase in ΔQS. With a larger paved fraction, the fraction of buildings and wall area is lower which reduces the high values of ΔQS

Externally heated protostellar cores in the Ophiuchus star-forming region

We present APEX 218 GHz observations of molecular emission in a complete sample of embedded protostars in the Ophiuchus star-forming region. To study the physical properties of the cores, we calculate H$_2$CO and c-C$_3$H$_2$ rotational temperatures, both of which are good tracers of the kinetic temperature of the molecular gas. We find that the H$_2$CO temperatures range between 16 K and 124 K, with the highest H$_2$CO temperatures toward the hot corino source IRAS 16293-2422 (69-124 K) and the sources in the $\rho$ Oph A cloud (23-49 K) located close to the luminous Herbig Be star S 1, which externally irradiates the $\rho$ Oph A cores. On the other hand, the c-C$_3$H$_2$ rotational temperature is consistently low (7-17 K) in all sources. Our results indicate that the c-C$_3$H$_2$ emission is primarily tracing more shielded parts of the envelope whereas the H$_2$CO emission (at the angular scale of the APEX beam; 3600 au in Ophiuchus) mainly traces the outer irradiated envelopes, apart from in IRAS 16293-2422, where the hot corino emission dominates. In some sources, a secondary velocity component is also seen, possibly tracing the molecular outflow.Comment: 19 pages, 9 figures, accepted for publication in Ap

The LMT circuit and SPICE

The state equations of the LMT circuit are modeled as a dedicated analogue computer circuit and solved by means of PSpice. The nonlinear part of the system is studied. Problems with the PSpice program are presented