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&

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&

Determinants of Block Tridiagonal Matrices

An identity is proven that evaluates the determinant of a block tridiagonal matrix with (or without) corners as the determinant of the associated transfer matrix (or a submatrix of it).Comment: 8 pages, final form. To appear on Linear Algebra and its Application

Identities and exponential bounds for transfer matrices

This paper is about analytic properties of single transfer matrices originating from general block-tridiagonal or banded matrices. Such matrices occur in various applications in physics and numerical analysis. The eigenvalues of the transfer matrix describe localization of eigenstates and are linked to the spectrum of the block tridiagonal matrix by a determinantal identity, If the block tridiagonal matrix is invertible, it is shown that half of the singular values of the transfer matrix have a lower bound exponentially large in the length of the chain, and the other half have an upper bound that is exponentially small. This is a consequence of a theorem by Demko, Moss and Smith on the decay of matrix elements of inverse of banded matrices.Comment: To appear in J. Phys. A: Math. and Theor. (Special issue on Lyapunov Exponents, edited by F. Ginelli and M. Cencini). 16 page

Hedin's equations and enumeration of Feynman's diagrams

Hedin's equations are solved perturbatively in zero dimension to count Feynman graphs for self-energy, polarization, propagator, effective potential and vertex function in a many-body theory of fermions with two-body interaction. Counting numbers are also obtained in the GW approximation.Comment: Revised published version, 3 pages, no figure

Notes on Wick's theorem in many-body theory

In these pedagogical notes I introduce the operator form of Wick's theorem, i.e. a procedure to bring to normal order a product of 1-particle creation and destruction operators, with respect to some reference many-body state. Both the static and the time- ordered cases are presented.Comment: 6 page

About arithmetic-geometric multidistances.

In a previous paper (see [7] ) we considered the family of multi-argument functions called multidistances, introduced in some recent papers (see [1]-[6]) by J.Martin and G.Mayor , which extend to n-dimensional ordered lists of elements the usual concept of distance between a couple of points in a metric space. In particular Martin and Mayor investigated three classes of multidistances, that is Fermat, sum-based and OWA- based multidistances. In this note we introduce a new family of multidistance functions, which are a generalization of the sum-based multidistances and we call them arithmetic- geometric multidistancesMultidistance, sum-based multidistances, arithmetic-geometric multidistances.

Multi-argument distances and regular sum-based multidistances.

In this paper we consider the family of multi-argument functions called multidistances, introduced in some recent papers by J.Martin and G.Mayor, which extend to n-dimensional ordered lists of elements the usual concept of distance between a couple of points in a metric space. In particular Martin and Mayor investigated three classes of multidistances, that is Fermat, sum-based and OWA- based multidistances.In this note we focus our attention on a specific property of multidistances, i.e. regularity, and we provide an alternative proof about the regularity of the sum-based multidistances.distance, multidistance, regularity, sum-based multidistances;

Sticky Information and Inflation Persistence: Evidence from U.S. Data

This paper provides a novel single equation estimator of the Sticky Information Phillips Curve (SIPC), which permits to estimate the exact model without any approximation or truncation. In detail, information stickiness is estimated by employing a GMM estimator that matches the theoretical with the actual covariances between current inflation and the lagged exogenous shocks that affect firms’ pricing decisions, which are considered the moments that measure inflation persistence. The main result of the paper is to show that the SIPC model can match inflation persistence only at the cost of mispredicting the variance of inflation, which is a novel finding in the empirical literature on the SIPC.Sticky Information, Inflation Persistence, two-stage GMM estimator

Partial Identification of Probability Distributions with Misclassified Data

This paper addresses the problem of data errors in discrete variables. When data errors occur, the observed variable is a misclassified version of the variable of interest, whose distribution is not identified. Inferential problems caused by data errors have been conceptualized through convolution and mixture models. This paper introduces the direct misclassification approach. The approach is based on the observation that in the presence of classification errors, the relation between the distribution of the "true" but unobservable variable and its misclassified representation is given by a linear system of simultaneous equations, in which the coefficient matrix is the matrix of misclassification probabilities. Formalizing the problem in these terms allows one to incorporate any prior information--e.g., validation studies, economic theory, social and cognitive psychology--into the analysis through sets of restrictions on the matrix of misclassification probabilities. Such information can have strong identifying power; the direct misclassification approach fully exploits it to derive identification regions for any real functional of the distribution of interest. A method for estimating the identification regions and construct their confidence sets is given, and illustrated with an empirical analysis of the distribution of pension plan types using data from the Health and Retirement Study.