Source extraction and photometry for the far-infrared and sub-millimeter continuum in the presence of complex backgrounds

(Abridged) We present a new method for detecting and measuring compact sources in conditions of intense, and highly variable, fore/background. While all most commonly used packages carry out the source detection over the signal image, our proposed method builds from the measured image a "curvature" image by double-differentiation in four different directions. In this way point-like as well as resolved, yet relatively compact, objects are easily revealed while the slower varying fore/background is greatly diminished. Candidate sources are then identified by looking for pixels where the curvature exceeds, in absolute terms, a given threshold; the methodology easily allows us to pinpoint breakpoints in the source brightness profile and then derive reliable guesses for the sources extent. Identified peaks are fit with 2D elliptical Gaussians plus an underlying planar inclined plateau, with mild constraints on size and orientation. Mutually contaminating sources are fit with multiple Gaussians simultaneously using flexible constraints. We ran our method on simulated large-scale fields with 1000 sources of different peak flux overlaid on a realistic realization of diffuse background. We find detection rates in excess of 90% for sources with peak fluxes above the 3-sigma signal noise limit; for about 80% of the sources the recovered peak fluxes are within 30% of their input values.Comment: Accepted on A&

The pre-ZAMS nature of Mol160/IRAS23385+6053 confirmed by Spitzer

Determining the timeline for the formation of massive YSOs requires the identification and characterisation of all the phases that a massive forming YSO undergoes. It is of particular interest to verify the observability of the phase in which the object is rapidly accreting while not yet igniting the fusion of hydrogen that marks the arrival on the ZAMS. One of the candidate prototypical objects for this phase is Mol160/IRAS23385+6053, which previous studies suggest it could be in a pre-Hot Core stage. We further investigate this issue by means of Spitzer imaging and spectroscopy in the 5-70 micron range. The dense core of Mol160/IRAS23385+6053, which up to now had only been detected at submm and mm wavelenghts has been revealed for the first time at 24 and 70 micron by Spitzer. The complete 24 micron -3.4 mm continuum cannot be fitted with a standard model of a Zero-Age Main-Sequence (ZAMS) star embedded in an envelope. A simple greybody fit yields a mass of 220 solar masses. The luminosity is slightly in excess of 3000 solar luminosities, which is a factor of 5 less than previous estimates when only IRAS fluxes were available between 20 and 100 micron. The source is under-luminous by the same factor with respect to UCHII regions or Hot-Cores of similar circumstellar mass, and simple models show that this is compatible with an earlier evolutionary stage. Spectroscopy between 5 and 40 microns revelas typical PDR/PIR conditions, where the required UV illumination may be provided by other sources revealed at 24 microns in the same region, and which can be plausibly modeled as moderately embedded intermediate-mass ZAMS stars. Our results strengthen the suggestion that the central core in Mol160/IRAS23385+6053 is a massive YSO actively accreting from its circumstellar envelope and which did not yet begin hydrogen fusion.Comment: Accepted by A&

The luminosity function of cluster galaxies. II. Data reduction procedures applied to the cluster Abell 496

We initiated a large project aimed to estimate the Luminosity Function of galaxies in clusters and to evaluate its relation to cluster morphology. With this paper we deem necessary to outline the general procedures of the data reduction and details of the data analysis. The cluster sample includes the brightest southern ROSAT all-sky survey clusters with z < 0.1. These have been observed in three colours g, r, i, and mapped up to a few core radii using a mosaic of CCD frames. E/S0 galaxies in the cluster core are singled out both by morphology (for the brightest galaxies), and by colour. The details of the data reduction procedure are illustrated via the analysis of the cluster Abell 496, which has been used as a pilot cluster for the whole program. The related photometric catalogue consists of 2355 objects. The limiting magnitudes (the reference Surface Brightness is given in parenthesis) in the various colours are respectively g(25.5) = 24.14, r(25.5) = 24.46, i(25.0) = 23.75$. These correspond to the limiting absolute magnitudes -12.28, -11.96 and -12.67 (H_0=50 km/sec/Mpc).Comment: 17 pages, 19 ps figures, aa.cl

A 100 pc Elliptical and Twisted Ring of Cold and Dense Molecular Clouds Revealed by Herschel Around the Galactic Center

Thermal images of cold dust in the Central Molecular Zone of the Milky Way, obtained with the far-infrared cameras on board the Herschel satellite, reveal a ~3 × 10^7 M_☉ ring of dense and cold clouds orbiting the Galactic center. Using a simple toy model, an elliptical shape having semi-major axes of 100 and 60 pc is deduced. The major axis of this 100 pc ring is inclined by about 40° with respect to the plane of the sky and is oriented perpendicular to the major axes of the Galactic Bar. The 100 pc ring appears to trace the system of stable x_2 orbits predicted for the barred Galactic potential. Sgr A⋆ is displaced with respect to the geometrical center of symmetry of the ring. The ring is twisted and its morphology suggests a flattening ratio of 2 for the Galactic potential, which is in good agreement with the bulge flattening ratio derived from the 2MASS data

Evaluation of time-series registration methods in dynamic area telethermometry for breast cancer detection

Automated motion reduction in 3D dynamic infrared imaging is on demand in many applications. Few methods for registering time-series dynamic infrared frames have been proposed. Almost all such methods are feature based algorithms requiring manual intervention. We apply different automated registration methods based on spatial displacement to 11 datasets of Breast Dynamic Infrared Imaging (DIRI) and evaluate the results in terms of both the image similarity and anatomical consistency of the transformation. The aim is to optimize the registration strategy for breast DIRI in order to improve the spectral analysis of temperature modulation; thus facilitating the acquisition procedure in a Dynamic Area Telethermometry framework. The results show that symmetric diffeomorphic demons registration outperforms both warped frames similarity and smoothness of deformation fields; hence proving effective for time-series dynamic infrared registratio

Search for massive protostellar candidates in the southern hemisphere: I. Association with dense gas

(Abridged) We have observed CS and C17O lines, and 1.2 mm cont. emission towards a sample of 130 high-mass protostellar candidates with DEC<-30 deg. This is the first step of the southern extension of a project started more than a decade ago aimed at the identification of massive protostellar candidates. We selected from the IRAS PSC 429 sources which potentially are compact molecular clouds. The sample is divided into two groups: the 298 sources with [25-12]>0.57 and [60-12]>1.30 we call 'High' sources, the remaining 131 we call 'Low' sources. In this paper, we check the association with dense gas and dust in 130 'Low' sources. We find a detection rate of ca. 85% in CS, demonstrating a tight association with dense molecular clumps. Among the sources detected in CS, ca. 76% have also been detected in C17O and ca. 93% in the 1.2 mm cont. Mm-cont. maps show the presence of clumps with diameters 0.2-2 pc and masses from a few Msun to 10^5 Msun; H2 volume densities lie between ca. 10^{4.5} and 10^{5.5} cm^{-3}. The L(bol) are 10^3-10^6 Lsun, consistent with embedded high-mass objects. Based on our results and those found in the literature for other samples, we conclude that our sources are massive objects probably in a stage prior to the formation of an HII region. We propose a scenario in which 'High' and 'Low' sources are both made of a massive clump hosting a high-mass protostellar candidate and a nearby stellar cluster. The difference might be due to the fact that the IRAS 12mu flux, the best discriminant between the two groups, is dominated by the emission from the cluster in 'Lows' and from the massive protostellar object in 'Highs'.Comment: Accepted for publication in Astron. & Astroph.; 34 pages (incl. 14 figures and 8 tables

FEATURE SELECTION APPLIED TO THE TIME-FREQUENCY REPRESENTATION OF MUSCLE NEAR-INFRARED SPECTROSCOPY (NIRS) SIGNALS: CHARACTERIZATION OF DIABETIC OXYGENATION PATTERNS

Diabetic patients might present peripheral microcirculation impairment and might benefit from physical training. Thirty-nine diabetic patients underwent the monitoring of the tibialis anterior muscle oxygenation during a series of voluntary ankle flexo-extensions by near-infrared spectroscopy (NIRS). NIRS signals were acquired before and after training protocols. Sixteen control subjects were tested with the same protocol. Time-frequency distributions of the Cohen's class were used to process the NIRS signals relative to the concentration changes of oxygenated and reduced hemoglobin. A total of 24 variables were measured for each subject and the most discriminative were selected by using four feature selection algorithms: QuickReduct, Genetic Rough-Set Attribute Reduction, Ant Rough-Set Attribute Reduction, and traditional ANOVA. Artificial neural networks were used to validate the discriminative power of the selected features. Results showed that different algorithms extracted different sets of variables, but all the combinations were discriminative. The best classification accuracy was about 70%. The oxygenation variables were selected when comparing controls to diabetic patients or diabetic patients before and after training. This preliminary study showed the importance of feature selection techniques in NIRS assessment of diabetic peripheral vascular impairmen

IRAS 23385+6053: a candidate protostellar massive object

We present the results of a multi-line and continuum study towards the source IRAS 23385+6053,performed with the IRAM-30m telescope, the Plateau de Bure Interferometer, the Very Large Array Interferometer and the James Clerk Maxwell Telescope. The new results confirm our earlier findings, namely that IRAS 23385+6053 is a good candidate high-mass protostellar object, precursor of an ultracompact H$_{II}$ region. The source is roughly composed of two regions: a molecular core $\sim0.03\div0.04$ pc in size, with a temperature of $\sim40$ K and an H$_{2}$ volume density of the order of 10$^{7}$ cm$^{-3}$, and an extended halo of diameter $\leq$0.4 pc, with an average kinetic temperature of $\sim 15$ K and H$_{2}$ volume density of the order of 10$^{5}$ cm$^{-3}$. The core temperature is much smaller than what is typically found in molecular cores of the same diameter surrounding massive ZAMS stars. We deduce that the core luminosity is between 150 and $1.6\times10^{4}L_{\odot}$, and we believe that the upper limit is near the ``true'' source luminosity. Moreover, by comparing the H$_{2}$ volume density obtained at different radii from the IRAS source, we find that the halo has a density profile of the type $n_{\rm H_{2}}\propto r^{-2.3}$. This suggests that the source is gravitationally unstable. Finally, we demonstrate that the temperature at the core surface is consistent with a core luminosity of $10^3 L_{\odot}$ and conclude that we might be observing a protostar still accreting material from its parental cloud, whose mass at present is $\sim 6 M_{\odot}$.Comment: 18 pages, 20 figure

IRAS 18511+0146: a proto Herbig Ae/Be cluster?

Context: The evolution of a young protocluster depends on the relative spatial distributions and dynamics of both stars and gas. Aims: We study the distribution and properties of the gas and stars surrounding the luminous (10^4 L_sun) protocluster IRAS 18511+0146. Methods: IRAS 18511+0146 and the cluster associated with it has been investigated using the sub-millimetre (JCMT-SCUBA), infrared (Spitzer-MIPSGAL, Spitzer-GLIMPSE, Palomar) and radio (VLA) continuum data. Cluster simulations have been carried out in order to understand the properties of clusters as well as to compare with the observations. Results: The central most obscured part of the protocluster coincident with the compact sub-millimetre source found with SCUBA is responsible for at least 2/3 of the total luminosity. A number of cluster members have been identified which are bright in mid infrared and show rising (near to mid infrared) spectral energy distributions suggesting that these are very young stellar sources. In the mid infrared 8.0 micron image, a number of filamentary structures and clumps are detected in the vicinity of IRAS 18511+0146. Conclusions: Based on the luminosity and cluster size as well as on the evolutionary stages of the cluster members, IRAS 18511+0146 is likely to be protocluster with the most massive object being a precursor to a Herbig type star.Comment: Accepted by the Astronomy and Astrophysics (23 Pages, 5 Tables, 12 Figures