Towards a Molecular Inventory of Protostellar Discs

The chemical environment in circumstellar discs is a unique diagnostic of the thermal, physical and chemical environment. In this paper we examine the structure of star formation regions giving rise to low mass stars, and the chemical environment inside them, and the circumstellar discs around the developing stars.Comment: 9 page PDF, 550 kbyte

An observational study of cometary globules near the Rosette nebula

Molecular line observations are reported of two regions containing small cometary globules at the edge of the Rosette Nebula. Observations of the CO, 13CO and 18CO J = 2 - 1,and CO J = 4 -3 molecular lines towards Globule 1, the most prominent of the group, show it has a well-developed head-tail structure, with a head diameter ~0.4pc, and a tail extending ~ 1.3 pc behind it. The major axis of the system points about 45 degrees away from the direction to the centre of the Rosette Nebula (which contains the presumed illuminating stars), and 20 degrees out of the plane of the sky, along a projected line towards the luminous (924 L⊙) infrared source IRAS 06314+0427. The CO lines have a complex velocity structure; with a pronounced broadening at the front of the head (as viewed from IRAS 06314+0427); a velocity gradient ~1.4 km s-1 along the tail, and material at the front of the head is blue-shifted by ~0.5 km s-1 compared to surrounding gas. The CO J = 2 - 1 line intensity peaks towards the front of the head, and along the edges of the tail. The 13CO J =2 - 1 antenna temperatures in the head are very similar to those of CO, suggesting very high opacities or column densities, or that there is significant CO self-absorption. There is a narrow rim of CO J = 4 - 3 emission around the front of the head over a limited velocity range, which correlates with the position of a faint optical rim, and a narrow ridge of 2 μm H2 emission. These data give strong support to the Radiation Driven Implosion (RDI) model of Lefloch and Lazareff (1994 - hereafter LL94), which was developed to explain the physical structure of cometary globules. Using an RDI simulation, a remarkably good fit to the data has been obtained, allowing the CO, 13CO and C18O spatial structures and velocity field to be modelled. This simulation suggests that Globule 1 is ~400,000 years old, and has a mass ~ 50 M⊙. Additional observations towards the region close to IRAS 06314+0427 show that it is associated with an intense molecular concentration lying at the northern end of a ~ 5 pc long molecular ridge, with a mass ~ 330 M⊙, and lies close to the centre of a shell-like condensation

Searching for signs of triggered star formation toward IC 1848

We have carried out an in-depth study of three bright-rimmed clouds SFO 11, SFO 11NE and SFO 11E associated with the HII region IC 1848, using observations carried out at the James Clerk Maxwell Telescope (JCMT) and the Nordic Optical Telescope (NOT), plus archival data from IRAS, 2MASS and the NVSS. We show that the overall morphology of the clouds is reasonably consistent with that of radiative-driven implosion (RDI) models developed to predict the evolution of cometary globules. There is evidence for a photoevaporated flow from the surface of each cloud and, based upon the morphology and pressure balance of the clouds, it is possible that D-critical ionisation fronts are propagating into the molecular gas. The primary O star responsible for ionising the surfaces of the clouds is the 06V star HD 17505. Each cloud is associated with either recent or ongoing star formation: we have detected 8 sub-mm cores which possess the hallmarks of protostellar cores and identify YSO candidates from 2MASS data. We infer the past and future evolution of the clouds and demonstrate via a simple pressure-based argument that the UV illumination may have induced the collapse of the dense molecular cores found at the head of SFO 11 and SFO 11 E

ISOCAM observations of the rho Ophiuchi cloud: Luminosity and mass functions of the pre-main sequence embedded cluster

We present the results of the first extensive mid-infrared (IR) imaging survey of the rho Ophiuchi embedded cluster, performed with the ISOCAM camera on board the ISO satellite. The main molecular cloud L1688, as well as L1689N and L1689S, have been completely surveyed for point sources at 6.7 and 14.3 micron. A total of 425 sources are detected including 16 Class I, 123 Class II, and 77 Class III young stellar objects (YSOs). Essentially all of the mid-IR sources coincide with near-IR sources, but a large proportion of them are recognized for the first time as YSOs. Our dual-wavelength survey allows us to identify essentially all the YSOs with IR excess in the embedded cluster down to Fnu ~ 10 - 15 mJy. It more than doubles the known population of Class II YSOs and represents the most complete census to date of newly formed stars in the rho Ophiuchi central region. The stellar luminosity function of the complete sample of Class II YSOs is derived with a good accuracy down to L= 0.03 Lsun. A modeling of this lumino- sity function, using available pre-main sequence tracks and plausible star for- mation histories, allows us to derive the mass distribution of the Class II YSOs which arguably reflects the IMF of the embedded cluster. We estimate that the IMF in rho Ophiuchi is well described by a two-component power law with a low- mass index of -0.35+/-0.25, a high-mass index of -1.7 (to be compared with the Salpeter value of -1.35), and a break occurring at M = 0.55+/-0.25 Msun. This IMF is flat with no evidence for a low-mass cutoff down to at least 0.06 Msun.Comment: A&A Document Class -- version 5.01, 27 pages, 10 figures v2: typos added including few changes in source numberin

The young stellar population in the Serpens Cloud Core: An ISOCAM survey

We present results from an ISOCAM survey in the two broad band filters LW2 (5-8.5 mu) and LW3 (12-18 mu) of a 0.13 square degree coverage of the Serpens Main Cloud Core. A total of 392 sources were detected in the 6.7 mu band and 139 in the 14.3 mu band to a limiting sensitivity of ~ 2 mJy. Only about 50% of the mid-IR excess sources show excesses in the near-IR J-H/H-K diagram. In the central Cloud Core the Class I/Class II number ratio is 19/18, i.e. about 10 times larger than in other young embedded clusters such as rho Ophiuchi or Chamaeleon. The mid-IR fluxes of the Class I and flat-spectrum sources are found to be on the average larger than those of Class II sources. Stellar luminosities are estimated for the Class II sample, and its luminosity function is compatible with a coeval population of about 2 Myr which follows a three segment power-law IMF. For this age about 20% of the Class IIs are found to be young brown dwarf candidates. The YSOs are in general strongly clustered, the Class I sources more than the Class II sources, and there is an indication of sub-clustering. The sub-clustering of the protostar candidates has a spatial scale of 0.12 pc. These sub-clusters are found along the NW-SE oriented ridge and in very good agreement with the location of dense cores traced by millimeter data. The smallest clustering scale for the Class II sources is about 0.25 pc, similar to what was found for rho Ophiuchi. Our data show evidence that star formation in Serpens has proceeded in several phases, and that a ``microburst'' of star formation has taken place very recently, probably within the last 10^5 yrs.Comment: 25 pages, 14 figures, accepted by A&A March 18th, see also http://www.not.iac.es/~amanda

Design for values in ICT

Information and communication technologies (ICT) are becoming pervasive. ICT development has accelerated, and within a few decades its use has expanded from particular work domains to diverse areas of work and everyday life. Consequently, the range of ICT stakeholders expanded from highly trained experts to all kinds of people with varying expertise and abilities. Sometimes, even people, who are not active users, are affected by the surrounding ICT. Since ICT influences stakeholders’ lives and in particular also their values, the ethical impact of ICT and the active consideration of values throughout design of ICT have become topics for research in several disciplines, including among others computer ethics, social informatics, or human-computer interaction. This chapter provides an overview of the history of ICT; different approaches to investigating, analyzing, and incorporating values in ICT; and practical methods to account for values in the ICT design process

Probing the potential of multimedia artefacts to support communication of people with dementia

Communication between people with dementia and others becomes increasingly difficult as the disease progresses. Symptoms such as memory loss, speech impairments and limitations in higher cognitive functions affect people’s abilities for communication and social interaction. At the same time, meaningful interactions with others are important for the quality of life of people with dementia. In this paper, we describe our work in designing technology probes and testing them with target users to understand how multimedia could be utilized to support the communication of people with dementia through memories