Interactions of the Infrared bubble N4 with the surroundings

The physical mechanisms that induce the transformation of a certain mass of gas in new stars are far from being well understood. Infrared bubbles associated with HII regions have been considered to be good samples of investigating triggered star formation. In this paper we report on the investigation of the dust properties of the infrared bubble N4 around the HII region G11.898+0.747, analyzing its interaction with its surroundings and star formation histories therein, with the aim of determining the possibility of star formation triggered by the expansion of the bubble. Using Herschel PACS and SPIRE images with a wide wavelength coverage, we reveal the dust properties over the entire bubble. Meanwhile, we are able to identify six dust clumps surrounding the bubble, with a mean size of 0.50 pc, temperature of about 22 K, mean column density of 1.7 $\times10^{22}$ cm$^{-2}$, mean volume density of about 4.4 $\times10^{4}$ cm$^{-3}$, and a mean mass of 320 $M_{\odot}$. In addition, from PAH emission seen at 8 $\mu$m, free-free emission detected at 20 cm and a probability density function in special regions, we could identify clear signatures of the influence of the HII region on the surroundings. There are hints of star formation, though further investigation is required to demonstrate that N4 is the triggering source.Comment: Accepted by ApJ (16 pages, 11 figures, 9 tables

The Focal-plane Instruments on Board WSO-UV

Dedicated to spectroscopic and imaging observations of the ultraviolet sky, the World Space Observatory for Ultraviolet Project is a Russia led international collaboration presently involving also China, Germany, Italy, Spain, and Ukraine. The mission consists of a 1.7m telescope able to perform: a) high resolution (R >= 60000) spectroscopy by means of two echelle spectrographs covering the 103-310 nm range; b) long slit (1 x 75 arcsec) low resolution (R similar to 1500 - 2500) spectroscopy using a near-UV channel and a far-UV channel to cover the 102-310 nm range; c) deep UV and diffraction limited UV and optical imaging (from 115 to 700 nm). Overall information on the project and on its science objectives are given by other two papers in these proceedings. Here we present the WSO-UV focal plane instruments, their status of implementation, and the expected performances

The Antarctic Submillimeter Telescope and Remote Observatory (AST/RO)

AST/RO, a 1.7 m diameter telescope for astronomy and aeronomy studies at wavelengths between 200 and 2000 microns, was installed at the South Pole during the 1994-1995 Austral summer. The telescope operates continuously through the Austral winter, and is being used primarily for spectroscopic studies of neutral atomic carbon and carbon monoxide in the interstellar medium of the Milky Way and the Magellanic Clouds. The South Pole environment is unique among observatory sites for unusually low wind speeds, low absolute humidity, and the consistent clarity of the submillimeter sky. Four heterodyne receivers, an array receiver, three acousto-optical spectrometers, and an array spectrometer are installed. A Fabry-Perot spectrometer using a bolometric array and a Terahertz receiver are in development. Telescope pointing, focus, and calibration methods as well as the unique working environment and logistical requirements of the South Pole are described.Comment: 57 pages, 15 figures. Submitted to PAS

Dust temperature maps of the Galactic plane: The

Context. Dust grains absorb the interstellar far ultra-violet and visible photons and re-emit them in far-infrared (FIR) wavebands. The dust FIR continuum can be predicted by a grid of models using various values of the interstellar radiation field. Aims. We analyze the dust continuum emission in two Hi-GAL science-demonstration phase (SDP) fields using both the radiative transfer code, Cloudy, and the DustEM dust model, to explore the effect of radiative transfer on dust temperature. The 500 μm sub-millimeter excess emission and the very small grain (VSG) contribution to the 70 μm intensity are investigated by spectral energy distribution (SED) fitting using the Cloudy model. Methods. By comparing the observation with the model prediction, we derive dust temperature maps of the two SDP fields by fitting the dust SED with 4-band data (SPIRE bands plus PACS 160 μm) using both Cloudy and DustEM models. Considering radiative transfer and grain physics simultaneously, we investigate the existence of a 500 μm excess and estimate the VSG contribution to the 70 μm intensity by fitting the dust SED with 3-band data (160, 250, and 350 μm) and 5-band data (SPIRE and PACS bands), respectively. Results. We confirm that the field with star formation activities have a higher temperature (18.7 ± 0.9 K) than the quiescent region (15.2 ± 0.6 K). We find that the radiative transfer affects the FIR SED of the SDP fields and results in a higher temperature distribution than the dust-only model fit. There is no significant detection of a 500 μm excess in the two SDP fields. The relative contribution from the VSGs to the 70 μm intensity can be up to 50%

A Method for Active Global Localization in Multi-robot System

In multi-robot system the ability to exchange information can reduce the uncertainty in the estimated location when robots can see each other. In this paper, a kind of dynamically evolving coordination architecture is proposed for cooperative localization according to the relative positions between robots. And to further improve the efficiency of cooperative localization, a decision theory based mechanism is proposed to make the robots cooperate actively during the localization process. Since stably tracking the multi-hypothesis of the robots' own position and their partners' position is of great importance for making a good decision of where to go in active localization, the co-evolution based adaptive Monte Carlo localization method in which samples are clustered into species to represents a hypothesis of robot's pose in a higher level than a single sample is adopted. Experiments are designed and carried out to prove the efficiency and stability of the proposed method

A Method for Active Global Localization in Multi-robot System

In multi-robot system the ability to exchange information can reduce the uncertainty in the estimated location when robots can see each other. In this paper, a kind of dynamically evolving coordination architecture is proposed for cooperative localization according to the relative positions between robots. And to further improve the efficiency of cooperative localization, a decision theory based mechanism is proposed to make the robots cooperate actively during the localization process. Since stably tracking the multi-hypothesis of the robots' own position and their partners' position is of great importance for making a good decision of where to go in active localization, the co-evolution based adaptive Monte Carlo localization method in which samples are clustered into species to represents a hypothesis of robot's pose in a higher level than a single sample is adopted. Experiments are designed and carried out to prove the efficiency and stability of the proposed method