12,083 research outputs found

    The silicate absorption profile in the ISM towards the heavily obscured nucleus of NGC 4418

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    The 9.7-micron silicate absorption profile in the interstellar medium provides important information on the physical and chemical composition of interstellar dust grains. Measurements in the Milky Way have shown that the profile in the diffuse interstellar medium is very similar to the amorphous silicate profiles found in circumstellar dust shells around late M stars, and narrower than the silicate profile in denser star-forming regions. Here, we investigate the silicate absorption profile towards the very heavily obscured nucleus of NGC 4418, the galaxy with the deepest known silicate absorption feature, and compare it to the profiles seen in the Milky Way. Comparison between the 8-13 micron spectrum obtained with TReCS on Gemini and the larger aperture spectrum obtained from the Spitzer archive indicates that the former isolates the nuclear emission, while Spitzer detects low surface brightness circumnuclear diffuse emission in addition. The silicate absorption profile towards the nucleus is very similar to that in the diffuse ISM in the Milky Way with no evidence of spectral structure from crystalline silicates or silicon carbide grains.Comment: 7 Pages, 3 figures. MNRAS in pres

    A characterization of dual quermassintegrals and the roots of dual steiner polynomials

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    For any IRI\subset\mathbb{R} finite with 0I0\in I, we provide a characterization of those tuples (ωi)iI(\omega_i)_{i\in I} of positive numbers which are dual querma\ss integrals of two star bodies. It turns out that this problem is related to the moment problem. Based on this relation we also get new inequalities for the dual querma\ss integrals. Moreover, the above characterization will be the key tool in order to investigate structural properties of the set of roots of dual Steiner polynomials of star bodies

    Isospin breaking in the nucleon mass and the sensitivity of β decays to new physics

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    We discuss the consequences of the approximate conservation of the vector and axial currents for the hadronic matrix elements appearing in β decay if nonstandard interactions are present. In particular, the isovector (pseudo)scalar charge gS(P) of the nucleon can be related to the difference (sum) of the nucleon masses in the absence of electromagnetic effects. Using recent determinations of these quantities from phenomenological and lattice QCD studies we obtain the accurate values gS=1.02(11) and gP=349(9) in the modified minimal subtraction scheme at μ=2  GeV. The consequences for searches of nonstandard scalar interactions in nuclear β decays are studied, finding for the corresponding Wilson coefficient εS=0.0012(24) at 90% C.L., which is significantly more stringent than current LHC bounds and previous low-energy bounds using less precise gS values. We argue that our results could be rapidly improved with updated computations and the direct calculation of certain ratios in lattice QCD. Finally, we discuss the pion-pole enhancement of gP, which makes β decays much more sensitive to nonstandard pseudoscalar interactions than previously thought

    Wine tourism in Spain: The case of three wine regions

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    By far the main focus of contemporary wine tourism research has been in ‘New World’ regions, while it appears to be under development in much of the ‘Old World.’ The present study adds to this underdeveloped body of research in that it addresses a range of wine tourism development issues, across three prominent ‘Old World’ wine regions: La Mancha, La Rioja and Penedès. A total of 94 wineries participated in the study. Respondents’ answers and comments indicate that while many of the participating wineries are several generations, or centuries, old, wine tourism appears to be in its ‘tentative’ stages, that is, only starting to gain momentum. One positive aspect is that most participants (68.1%) indicated that their wineries are open to the public mainly to generate interest for their wine brands among visitors, while 61.7% use the cellar door to educate customers, thus demonstrating wineries’ longer-term strategy to ‘convert’ visitors to brand loyalty through wine tourism. Given the critical role tourism plays for Spain’s economy, with over 50 million visitors per year, these findings can have important implications for the long term sustainability of the wine industry in many of the nation’s wine regions

    A Nexafs Study of Nitric Oxide Layers Adsorbed from a nitrite Solution onto a Pt(111) Surface

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    NO molecules adsorbed on a Pt(111) surface from dipping in an acidic nitrite solution are studied by near edge X-ray absorption fine structure spectroscopy (NEXAFS), X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and scanning tunnelling microscopy (STM) techniques. LEED patterns and STM images show that no long range ordered structures are formed after NO adsorption on a Pt(111) surface. Although the total NO coverage is very low, spectroscopic features in N K-edge and O K-edge absorption spectra have been singled out and related to the different species induced by this preparation method. From these measurements it is concluded that the NO molecule is adsorbed trough the N atom in an upright conformation. The maximum saturation coverage is about 0.3 monolayers, and although nitric oxide is the major component, nitrite and nitrogen species are slightly co-adsorbed on the surface. The results obtained from this study are compared with those previously reported in the literature for NO adsorbed on Pt(111) under UHV conditions

    Sub-arcsec mid-IR observations of NGC 1614: Nuclear star-formation or an intrinsically X-ray weak AGN?

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    We present new mid-infrared N-band spectroscopy and Q-band photometry of the local luminous infrared galaxy NGC1614, one of the most extreme nearby starbursts. We analyze the mid-IR properties of the nucleus (central 150 pc) and four regions of the bright circumnuclear (diameter~600 pc) star-forming (SF) ring of this object. The nucleus differs from the circumnuclear SF ring by having a strong 8-12 micron continuum (low 11.3 micron PAH equivalent width). These characteristics, together with the nuclear X-ray and sub-mm properties, can be explained by an X-ray weak active galactic nucleus (AGN), or by peculiar SF with a short molecular gas depletion time and producing an enhanced radiation field density. In either case, the nuclear luminosity (L(IR) < 6e43 erg/s) is only <5% of the total bolometric luminosity of NGC1614. So this possible AGN does not dominate the energy output in this object. We also compare three star-formation rate (SFR) tracers (Paα\alpha, 11.3 micron PAH, and 24 micron emissions) at 150 pc scales in the circumnuclear ring. In general, we find that the SFR is underestimated (overestimated) by a factor of 2-4 (2-3) using the 11.3 micron PAH (24 micron) emission with respect to the extinction corrected Paα\alpha SFR. The former can be explained because we do not include diffuse PAH emission in our measurements, while the latter might indicate that the dust temperature is particularly warmer in the central regions of NGC1614.Comment: Accepted for publication in MNRAS; 10 pages, 5 figure

    The Top Ten solar analogs in the ELODIE library

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    Several solar analogs have been identified in the library of high resolution stellar spectra taken with the echelle spectrograph ELODIE. A purely differential method has been used, based on the chi2 comparison of a large number of G dwarf spectra to 8 spectra of the Sun, taken on the Moon and Ceres. HD 146233 keeps its status of closest ever solar twin (Porto de Mello & da Silva 1997). Some other spectroscopic analogs have never been studied before, while the two planet-host stars HD095128 and HD186427 are also part of the selection. The fundamental parameters found in the literature for these stars show a surprising dispersion, partly due to the uncertainties which affect them. We discuss the advantages and drawbacks of photometric and spectroscopic methods to search for solar analogs and conclude that they have to be used jointly to find real solar twins.Comment: 12 pages, accepted in A&
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